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MindMap Gallery Medicine-Chapter 10 Functions of the Nervous System
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Medicine-Chapter 10 Functions of the Nervous System
This is a mind map about the functions of the nervous system in Chapter 10. It is introduced in detail and described comprehensively. I hope it will be helpful to those who are interested!
Edited at 2023-11-29 20:08:16
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Medicine-Chapter 10 Functions of the Nervous System
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- Outline
functions of nervous system
Basic principles of functional activity of the nervous system
neurons and glial cells
Neurons
nervous system
Cells that make up the nervous system: neurons, glial cells
Neurons are the basic structural and functional units of the nervous system and undertake the main functional activities of the nervous system.
General structure of neurons
dendrites
Dendritic spines: On the dendritic branches, the dendritic membrane protrudes to form numerous polymorphic dendritic spines, which form synapses with the axon terminals of other neurons.
The branches of dendrites and their dendritic spines greatly expand the area of the cell membrane, improving the range and sensitivity of neuronal information reception.
During brain development, the increasing number of dendritic spines is related to the development of intelligence
axon
A neuron usually has only one axon, but there are more than one dendrites.
axis hillock
The part of the cell body where the axons originate swells and protrudes outward.
The starting part of the axon is slightly thick and not wrapped by myelin sheath.
The neurons in the middle segment are shorter, and the diameter of the axon is often proportional to its length, but within the same axon, the entire length is more uniform.
The axon terminal is divided into many small branches, which are completely unmyelinated, and are called nerve endings. The most terminal part is often enlarged into a ball, button or handle shape, and is called a synaptic button, terminal button, or synaptic nodule, which stores neurotransmitters. synaptic vesicles are highly aggregated
The main function
Neurons - receive, integrate, conduct, and transmit information
Cell body and dendrites - receive and integrate information
Axon initial segment - mainly responsible for generating action potentials and also involved in information integration
Axon - conducts information
Synaptic terminals - responsible for transmitting information to effector cells or other neurons
Nerve fibers and their functions
Definition: Axons and peripheral processes of sensory neurons are called nerve fibers.
nerve fibers
Myelinated nerve fibers: repeatedly wound and tightly wrapped by the myelin sheath or neural membrane formed by glial cells
Unmyelinated nerve fibers: loosely wrapped by glial cells, with thin or loose myelin sheath
The glial cells that make up the myelin or nerve membrane are mainly Schwann cells in the peripheral nervous system; they are microdendrocytes in the central nervous system.
Main functions: excitation conduction and material transport
Excitatory conduction characteristics, influencing factors, classification
Characteristics of conducted excitation
Dependence on intact nerve fiber structure and function, referred to as "integrity"
Non-interference, referred to as "insulation"; one nerve fiber contains multiple nerve fibers, but they do not interfere with each other when conducting excitement at the same time
Bidirectionality. An action potential that occurs locally in a nerve fiber and conducts in two opposite directions at the same time
Relatively fatigue-free (relative to synapses, synaptic transmission is prone to fatigue due to depletion of neurotransmitters
Factors affecting nerve fiber conduction velocity
Diameter size, presence or absence of myelin sheath, different thickness of myelin sheath, temperature (within a certain range, conduction velocity is proportional to temperature, for example: hypothermic anesthesia)
Myelinated nerve fiber conduction velocity > unmyelinated nerve fiber
Classification (according to differences in excitatory conduction velocity)
Three categories: A (α, β, γ, δ), B and C
nerve fiber axoplasmic transport function
Axoplasm: The cytoplasm that fills the axon and has the function of transporting substances
Classification
Orthodromic axoplasmic transport
Fast: performed by a kinesin protein
slow
reverse axoplasmic transport
Mainly seen in the transport of certain substances taken up by axon terminals (neurotrophic factors, rabies virus, tetanus toxin, etc.)
horseradish peroxidase to trace
Executed by dynein and its many cofactors
Significance: It is of great significance for maintaining the integrity of neuron morphology and function.
Trophic effects of nerves on effector tissues
Functional role: Nerves release neurotransmitters through their terminals, causing the innervated tissues to quickly perform their main functions (muscle contraction, gland secretion, etc.)
nutritional effect
Nerve terminals release certain nutritional factors to adjust the metabolic activity of the tissues they control, slowly but continuously affecting their structure and functional status.
The consequences of short-term deletion are not obvious, but the consequences of long-term deletion are serious.
Regulatory effects of neurotrophic factors on neurons
Neurotrophic factors refer to a type of protein or polypeptide molecules produced by effector tissues and glial cells innervated by nerves and necessary for the growth and survival of neurons.
Glial cells
Structural and functional characteristics
Widely distributed in peripheral and central nervous systems
There are processes, but there are no dendrites or axons. There are also many types of neurotransmitter receptors on some glial cell membranes.
Chemical synapses are not formed between cells, but gap junctions are common; membrane potential also changes with the extracellular K+ concentration, but action potentials cannot be generated.
Glial cells have the ability to divide and proliferate throughout their lives
Types and functions
astrocytes
The most numerous and most complex glial cells in the brain
Function
Mechanical support and nutritional effects
Isolation and Barrier Function
Migration guidance
Repair and proliferative effects
Excessive astrocyte proliferation can also form brain tumors and become the focus of epileptic seizures
immune response
Astrocytes are antigen-presenting cells of the central nervous system. The specific major histocompatibility complex molecule II expressed on their cell membranes can bind to unprocessed antigens and present them to T lymphocytes.
Stabilization of K+ concentration in extracellular fluid
There is a sodium-potassium pump on the membrane; proliferating glial cells produce scars and their potassium-pumping ability is weakened, resulting in high K+ in the local external fluid and the formation of epileptic lesions.
Metabolism of certain transmitters and active substances
Oligodendrocytes and Schwann cells
Can form myelin sheaths in the central and peripheral nervous systems respectively
Other types of glial cells
Microdendrocytes: equivalent to phagocytes in the central nervous system
synaptic transmission
Synapse: A functional connection site or device between neurons or between neurons and other types of cells (effectors)
electrical synaptic transmission
Electrical synapse is a synapse that uses electric current as the transmission medium. Its structural basis is gap junction.
Features
Bidirectional and fast
electrotension spread
plasticity
Electrical synapses are ubiquitous in invertebrate nervous systems
chemical synaptic transmission
Use neurotransmitters released by neurons as information transmission media
directed synaptic transmission
Neurotransmitters released from directional synaptic terminals only act on a very limited part of the post-synaptic membrane structure, typical ions: skeletal muscle nerve-muscle junctions and neurons
Microstructure of the classic synapse
Axon-dendrite or axon-soma synapse
Synapse: presynaptic membrane, synaptic cleft, postsynaptic membrane
There are dense mitochondria and synaptic vesicles in the axoplasm of the presynaptic terminal
Synaptic vesicle type
Small, clear, transparent vesicles containing acetylcholine or amino acid transmitters
Small, dense-centered vesicles containing catecholamine transmitters
Large, dense-centered vesicles containing neuropeptide transmitters
Classical synaptic transmission process (electro-chemical-electrical)
Electricity: When the excitement of the presynaptic neuron is transmitted to the terminal, the presynaptic membrane depolarizes
Chemistry: Neurotransmitter Release
Mobilization: Activated Ca2+-CaM-dependent protein kinase phosphorylates synaptic proteins, weakening their ability to bind to cytoskeletal filaments and dissociating synaptic vesicles from the cytoskeletal filaments.
Ferry: Free synaptic vesicles ferry to the activation zone with the help of a type of small molecule G protein Rab3/Rab27
Positioning: requires the participation of vesicle proteins on the vesicle membrane and target proteins on the presynaptic membrane
Fusion: Fusion of synaptic vesicles and presynaptic membrane
Exit: A temporary fusion pore is formed on the synaptic vesicle and the presynaptic membrane, and the neurotransmitter is released from the synaptic vesicle.
Electricity: a potential change in the postsynaptic membrane that causes a certain degree of depolarization or hyperpolarization.
non-directional synaptic transmission
It does not have a classic synaptic structure, and the neurotransmitters released from its presynaptic membrane can diffuse to postsynaptic components that are far away and wide in scope.
In the central nervous system, it mainly occurs in the fiber endings of monoaminergic (adrenaline, dopamine, serotonergic) neurons.
Compared with directional synapses, characteristics
No specific postsynaptic component, the site of action is scattered
There is no fixed synaptic gap, so the diffusion distance varies and the length of time varies.
Whether the released transmitter can produce information transmission effects depends on whether there are corresponding receptors on the target cells)
Factors and links affecting directional synaptic transmission
Affects transmitter release
Mainly depends on the amount of Ca2+ entering the terminal. Increased extracellular calcium ion concentration, accelerated frequency, increased amplitude or prolonged duration of action potentials reaching presynaptic terminals can all increase transmitter release.
Affects transmitter clearance
Released transmitter synapses are reuptaken by presynaptic terminals or metabolized by enzymes and cleared
Tricyclic antidepressants inhibit the reuptake of NE in the presynaptic membrane in the brain
Reserpine can inhibit the reuptake of NE by the vesicle membrane
Neostigmine and organophosphorus pesticides can inhibit acetylcholinesterase on the postsynaptic membrane and hinder the hydrolysis of acetylcholine so that it can continue to function.
Affects postsynaptic membrane reactivity
Both the density of postsynaptic receptors and their affinity for transmitter binding can change.
Tubocurarine (muscle relaxant) and α-bungarotoxin can block the N2-type acetylcholine receptor channel in the acetylcholine postsynaptic membrane
excitatory and inhibitory postsynaptic potentials
Excitatory postsynaptic potential (EPSP)
Depolarizing postsynaptic potential (chemically gated channel) caused by synaptic transmission in the postsynaptic membrane
Mainly Na+ and K+
Inhibitory postsynaptic potential (IPSP)
Hyperpolarizing postsynaptic potential caused by synaptic transmission in the postsynaptic membrane
Mainly Cl-
Generation of action potentials in postsynaptic neurons
A postsynaptic neuron generally synapses with multiple presynaptic nerve terminals, producing both EPSP and IPSP
Synaptic transmission characteristics
One way delivery
central delay
sum of excitement
Changes in excitatory rhythm
issued later
synaptic plasticity
Refers to the characteristics of long-lasting changes in the form and function of synapses (mainly refers to changes in synaptic efficacy)
posttetanic enhancement
Repeated stimulation of presynaptic neurons induces transient changes in synaptic efficacy
Depression: plasticity mechanism that reduces synaptic efficacy - some voltage-gated calcium channels on the presynaptic terminal membrane are closed
Potentiation: the phenomenon of increased synaptic efficacy
Habituation and sensitization
Habituation: the phenomenon of weakening or shortening of postsynaptic responses in a short period of time after repeated mild stimulation.
The gill retraction reflex of the invertebrate Aplysia
Calcium channels in presynaptic terminals are gradually inactivated and calcium ion influx is reduced.
Sensitization: the phenomenon of short-term enhancement or prolongation of postsynaptic responses after noxious stimulation
The opening time of calcium channels in presynaptic terminals is prolonged and the influx of calcium ions is increased.
long-term synaptic plasticity
Long-term enhanced LTP
long-term depression of LTD
Long-term weakening of synaptic efficacy
Longer-lasting LTP and LTD also involve protein synthesis and structural changes in synapses and synaptic spines
neurotransmitters and receptors
Neurotransmitters
Definition: A message-transmitting substance synthesized and released by presynaptic neurons that can specifically act on receptors on postsynaptic neurons or effector cells to produce certain effects.
Identification of transmitters
Meet the criteria
Presynaptic neurons possess precursors and enzyme systems that synthesize transmitters
can synthesize this transmitter
The synthesized transmitter is stored in synaptic vesicles and can be released into the synaptic cleft when the excitatory impulse reaches the terminal.
Can act on specific receptors on the postsynaptic membrane and exert its physiological effects
There is an enzyme or other means of inactivation that inactivates the transmitter
There are specific receptor activators and antagonists that can mimic or block the synaptic transmission of this transmitter.
The concept of tempering
Substances that regulate transmitter information
Most act through G protein-coupled receptors
No clear boundary between modulators and neurotransmitters
coexistence of transmitters
Two or more transmitters (modulators) coexist in the same neuron
Helps coordinate certain physiological activities
transmitter metabolism
Process: synthesis, storage, release, degradation (via enzymatic degradation and reuptake in presynaptic terminals), reuptake, resynthesis
Receptor type and distribution
Definition: refers to special biomolecules located on the cell membrane or within the cell that can specifically bind to certain chemical substances and induce specific biological effects.
Activator: A chemical substance that can enhance the biological activity of the receptor after specifically binding to the receptor.
Antagonist (blocker): A chemical substance that does not change the biological activity of the receptor after specifically binding to the receptor, but produces an anti-agonist effect by occupying the receptor.
Ligands: Agonists (primary) and Blockers
Receptor Types and Subtypes
presynaptic receptor
Receptors located on the presynaptic membrane
When presynaptic receptors are activated, they can affect synaptic transmission by modulating transmitter release at presynaptic terminals.
For α1 and α2 receptors in glutamatergic terminals, their ligands are derived from other types of synaptic terminals, also known as heterologous receptors.
Mechanism of action of receptors
The vast majority of receptors that mediate membrane signal transduction are G protein-coupled receptors (metabotropic).
A few are ion channel receptors (ionotropic receptors)
concentration of receptors
There are clusters of receptors on the postsynaptic membrane corresponding to the presynaptic membrane activation zone.
modulation of receptors
The number of membrane receptor proteins and their affinity for binding to transmitters can be regulated in different physiological or pathological situations.
When transmitter secretion is insufficient, the number of receptors will gradually increase and the affinity will gradually increase - upregulation of receptors
Changes in receptor affinity: achieved through phosphorylation or dephosphorylation of receptor proteins
Main neurotransmitters and their receptors
Acetylcholine and its receptors
Neurons that use ACh as a transmitter are called cholinergic neurons, and their nerve fibers are cholinergic nerve fibers.
Receptors that specifically bind to ACh are called cholinergic receptors
muscarinic receptors
nicotinic receptors
Neurons that express cholinergic receptors are called acetylcholine-sensitive neurons
The cholinergic system consists of cholinergic neurons, cholinergic receptors, neurons or effector cells expressing cholinergic receptors - it is the most widely distributed and involved nerve signal transmission system in the body.
Monoamine receptors and their receptors
Including: NE, epinephrine, dopamine, 5-hydroxytryptamine, histamine, etc.
Common features: Neuron cell bodies are relatively concentrated in the central nervous system, but fiber projections and receptors are distributed over a wide range
Classification
NE and adrenaline and their receptors
Both are catecholamines and use tyrosine as a synthetic raw material.
Tyrosine forms dopamine under the action of cytoplasmic tyrosine hydroxylase and dopamine decarboxylase, and dopamine is catalyzed by dopamine-β-hydroxylase to generate NE.
Neurons that use NE as a neurotransmitter are called NE neurons
In the center: the effects of epinephrine are mainly involved in the regulation of cardiovascular activity; the effects of NE are more extensive
In the periphery: NE has a strong effect on alpha receptors
Neurons that use adrenaline as a transmitter are called adrenergic neurons
Widely distributed in the central and peripheral nervous systems
Myocardium mainly expresses beta receptors; vascular smooth muscle has alpha and beta receptors; vascular smooth muscle of the skin, kidney, and gastrointestinal tract mainly contains alpha receptors.
Receptors that can bind to NE and epinephrine are called adrenergic neurons, both of which are G protein-coupled receptors (alpha type, beta type)
Dopamine and its receptors (DA)
It belongs to the catecholamines and mainly exists in three pathways: central substantia nigra-striatum, midbrain-limbic forebrain, and nodule-infundibulum.
Dopamine receptors in the basal ganglia gradually decrease with age
The massive reduction of dopamine receptor neurons in the nigrostriatal pathway is the main mechanism of Parkinson's disease at the central neuronal and transmitter levels.
5-hydroxytryptamine and its receptors
Serotonin (5-TH, serotonin)
In platelets and intestines, mainly involving the digestive system and platelet aggregation In the center, its main function is to regulate pain sensation, sleep, body temperature, sexual behavior, pituitary endocrine activity, etc.
Histamine and its receptors
Histaminergic fibers reach almost all parts of the central
H1, H2, and H3 receptors are widely found in the central and peripheral nervous systems. In the central nervous system, H3 is mostly a presynaptic receptor.
Histamine is also present in mast cells of non-nervous tissues and enterochromaffin cells of the gastrointestinal mucosa, which express H4 receptors. H4 receptors are also highly expressed in many other types of peripheral tissues or cells
Amino acid transmitters and their receptors
Excitatory amino acid transmitters and their receptors
Glutamic acid
The main excitatory transmitter in the brain and spinal cord
Widely distributed in the central nervous system and can be divided into ionotropic receptors and metabotropic receptors
aspartic acid
Pyramidal cells and spiny stellate cells commonly found in the visual cortex
Inhibitory amino acid transmitters and their receptors
Gamma-aminobutyric acid (CABA)
is the main inhibitory transmitter in the brain
Glycine
Mainly distributed in the brainstem and spinal cord
Glycine receptors are ionotropic receptors. The chloride ion channel of the channel usually allows chloride ions and other monovalent anions to enter the cell when the channel is open, causing IPSP in the postsynaptic membrane.
Neuropeptides and their receptors
Hormone peptides and their receptors
Substance P
It is abundant in the primary afferent fibers of the spinal cord and has a high concentration in the substantia nigra-striatal pathway. It may cause neuroendocrine regulation in the hypothalamus. In the periphery, substance P can cause intestinal smooth muscle contraction, vasodilation, and decrease in blood pressure.
Opioid peptides and their receptors
Endorphins (mainly beta-endorphin), enkephalins, dynorphins
Hypothalamic and pituitary neuropeptides and their receptors
hypothalamic regulatory peptide (HRP)
Brain-gut peptide and its receptors
Peptides dually distributed in the gastrointestinal tract and brain
Other peptide transmitters and their receptors
Bradykinin, endothelin atrial natriuretic peptide, calcitonin gene-related peptide, neuropeptide Y
Purine transmitters and their receptors
The main transmitters are adenosine and ATP
Gas molecules and other types of neurotransmitters and their receptors
Nitric oxide, carbon monoxide, hydrogen sulfide
Basic laws of reflex activity
Definition and Classification of Reflection
Reflex is the basic way of nerve activity
Classification
Unconditioned reflex: a reflex activity that is present at birth, limited in number, relatively fixed and low-level in form.
Conditioned reflex: a reflex formed through acquired learning and training. It is the most advanced form of reflex activity and is established on the basis of unconditioned reflex.
Integration of reflex centers
Monosynaptic reflex: a reflex that passes through only one synaptic transmission between an afferent neuron and an efferent neuron.
Tendon reflex: The only reflex in the body that can be completed only through a monosynaptic reflex
Polysynaptic reflex: a reflex transmitted through multiple synapses in the central nervous system
The connection between central neurons
Single-line connection: a total of presynaptic neurons have synaptic connections with only one postsynaptic neuron.
divergent and convergent connections
divergent connections
One neuron forms synaptic connections with multiple neurons through its axon collaterals or terminal branches
(More in the afferent pathway)
aggregation contact
A neuron can receive projections from the axon terminals of many neurons to establish synaptic connections.
(More in the outgoing path
Chain and ring connections
The divergent and convergent connections composed of interneurons exist at the same time, and can form chain connections or ring connections.
Local neurons and local neuronal circuits
Local circuit neurons: There are a large number of short axons and axonless neurons in the central nervous system, and their dendrites and axons only serve to connect within a certain central location.
local neuronal circuit
Definition: The interconnection pathway of neuronal interactions composed of local circuit neurons and their processes.
type
A circuit composed of multiple local circuit neurons
A circuit consisting of a local circuit of neurons
Part of the structural process circuit consisting of local circuit neurons
Characteristics of central excitation propagation
One-way propagation (only from presynaptic terminal → postsynaptic neuron)
Central delay (response nerve time minus the conduction time required for excitation on the afferent and efferent routes and the time required for excitation to be transmitted at the effector synapse
The EPSP caused by the sum of the excitations of a single afferent impulse in a single fiber is a local potential with a smaller depolarization amplitude.
Changes in the excitatory rhythm. The afferent neurons and efferent neurons of a certain reflex arc often have different firing frequencies during the excitation transmission process.
Post-release and feedback
Sensitive to changes in internal environment and prone to fatigue (related to transmitter depletion)
central inhibition and central facilitation
postsynaptic inhibition
Release of inhibitory transmitters from inhibitory interneurons in the central nervous system
two forms
Afferent collateral inhibition (inhibitory central neuron excitation
On the one hand, it forms an excitatory synapse with a central neuron on the reflex pathway; on the other hand, it forms an excitatory synapse with an inhibitory neuron through collateral branches.
Ensure coordinated control of flexor and extensor muscle activities
regression inhibition
Inhibition of neurons by axonal collaterals and inhibitory interneurons
Promptly terminate the activity of neurons and synchronize the activity of many neurons in the same center
presynaptic inhibition
The axon terminal of one neuron forms an axon-axon synapse with the axon terminal of a second excitatory neuron
The transmitter released when the first neuron is excited relatively reduces the excitatory postsynaptic potential - postsynaptic inhibition - generated in the cell body of the third neuron when the second neuron is excited.
Three mechanisms
When terminal B is excited, the release of GABA causes the Cl- conductance of terminal A to increase, the membrane depolarizes, the action potential amplitude of conductive terminal A decreases, and the duration shortens, which reduces the Ca2+ entering terminal A, causing the amount of transmitter release to decrease. Resulting in a decrease in the EPSP of neuron C
There are GABAb receptors in some axon terminals. When this receptor is activated, the potassium channel on the membrane is opened through the coupled G protein, causing K+ outflow, accelerating membrane repolarization, reducing terminal Ca2+ inflow and causing inhibition. effect
Directly inhibits transmitter release by activating certain metabotropic receptors at excitatory terminals, regardless of Ca'2+ influx.
presynaptic facilitation
Prolonged terminal action potential duration
Calcium channels are open longer
postsynaptic facilitation
It manifests as the summation of EPSPs, which increases the amplitude of EPSPs and brings them closer to the threshold potential level.
higher functions of the brain
learning and memory
form of learning
non-joint learning
There is no need to establish a connection between two stimuli or a stimulus and a response, only the repetition of a single stimulus can produce
federated learning
The process of repeated occurrences of two stimuli or a behavior and a stimulus that are very close in time, and finally gradually forming in the brain.
① Classical conditioned reflex (Pavlovian reflex); conditioned reflex is established on the basis of unconditioned reflex
②Operant conditioned reflex: a complex conditioned reflex controlled by consciousness
form of memory
Declarative memory and non-declarative memory
Declarative memory: memory of facts or events related to a specific time, place, or task
Formation depends on brain areas such as the hippocampus and medial temporal lobe
Non-declarative memory: the memory of a series of regular operating procedures, which is a kind of subconscious perception and reflection
It is a process that does not rely on consciousness and understanding. Once formed, it is not easy to forget.
Short-term memory and long-term memory
Short-term memory: short storage time
Long-term memory: long retention time
Human memory processes and forgetting
human memory process
Four stages: sensory memory, first-level memory, second-level memory, and third-level memory
forget
Partial or complete loss of memory and recognition ability. Forgetting is an inevitable physiological phenomenon.
Forgetting does not mean that memory traces disappear completely
Amnesia: memory impairment due to brain disorder
Anterograde amnesia: No new memories can be formed, and existing ones are not affected (mechanism; first-level memories cannot be transferred to second-level memories)
Retrograde amnesia: the inability to recall experiences in the period before the memory impairment occurred (mechanism: second-level memory is disturbed, while tertiary memory is not affected)
mechanisms of learning and memory
Brain areas involved in learning and memory
The striatum is involved in the learning of certain operating skills, and the cerebellum is involved in the learning of motor skills.
The prefrontal lobe coordinates the formation of short-term memory, and after processing is transferred to the hippocampus, the hippocampus plays an important role in the formation of long-term memory.
synaptic plasticity
is the physiological basis of learning and memory
Synthesis of proteins and transmitters in the brain
Longer memory is related to the metabolism of substances in the brain (especially the synthesis of proteins in the brain)
Language and other cognitive functions
One-sided dominance of language function in cerebral cortex
The left cerebral cortex is the dominant hemisphere for language
language center of cerebral cortex
Damage to the posterior part of the superior temporal gyrus → Sensory aphasia: The patient can speak and write, and can understand text, but cannot understand other people’s conversations → cannot answer other people’s questions
Damage to Broca's area → Motor aphasia: Can read text and understand what others are saying, but cannot speak himself and has lost the ability to organize language.
Angular gyrus damage → alexia: unable to read text, but his vision is not damaged, and other language functions are intact
Damage to the middle frontal gyrus → Agraphia: Can understand what others are saying, can read text, can speak, but cannot write
Damage to the posterior part of the left temporal lobe → fluent aphasia: normal speech, but unable to express what he means
Other cognitive functions of the cerebral cortex
The prefrontal cortex is involved in short-term episodic memory and emotional activities
The temporal lobe association cortex is involved in auditory and visual memory
The parietal association cortex is involved in the learning of fine somatosensory and spatial depth sensations
Correlation between cerebral cortex functions on both sides
Brain electrical activity and sleep and wakefulness
brain electrical activity
spontaneous electrical activity
EEG waveform
Spontaneous brain electrical activity: Rhythmic potential changes spontaneously generated in the cerebral cortex without obvious stimulation.
waveform
Alpha wave: occurs when an adult is awake, quiet and has his eyes closed
Beta waves; a sign of intense activity in the neocortex
Theta wave: when adults are sleepy
Delta wave: falling asleep, extreme fatigue or anesthesia
Changes in EEG waveforms
Waveforms with low frequencies have larger amplitudes, and waveforms with higher frequencies have smaller amplitudes.
During sleep, the brain waves show high-amplitude slow waves - synchronization of the brain; when awake, they show low-amplitude fast waves - desynchronization of the brain.
Patients with epilepsy or patients with space-occupying lesions in the cortex may have spikes in their brain waves.
Brain wave formation mechanism
cortical evoked potential
Definition refers to the potential change induced in a certain part of the cerebral cortex when stimulating the sensory afferent system or a certain part of the brain.
Generally includes three parts: main reaction, secondary reaction, and post-release
The amplitude of the evoked potential is small
Sleep and wakefulness
Two states of sleep and their physiological significance
Non-rapid eye movement sleep (NREM)
It is divided into four stages: Stage I is the sleep stage; Stage II is the light sleep stage; Stage III is the moderate sleep stage; Stage IV is the deep sleep stage.
high amplitude slow wave
Conducive to physical recovery and promote growth and development
Rapid eye movement sleep (REM)
Low-amplitude fast waves, (also called heterogeneous sleep)
During REM sleep: protein synthesis in the brain is accelerated, brain oxygen consumption and blood flow increase, and growth hormone secretion decreases
Can promote learning and memory as well as energy recovery
The mechanism of wakefulness and sleep
brain regions associated with arousal
The generation of arousal is related to the activity of the brainstem reticular formation
brain areas related to sleep
Brain areas that promote NERM sleep
The most important is the ventrolateral part of the preoptic area (VLPO)
Brain areas that promote REM sleep
The pons-lateral geniculate body-occipital spike (PGO) is the initiating factor of REM sleep
Endogenous substances that regulate wakefulness and sleep
Adenosine
The content of adenosine during awakening increases with the length of awakening, and high levels of adenosine can promote NREM sleep
Prostaglandin D2
It is formed from prostaglandin H2 through the action of prostaglandin D synthase. Inhibiting prostaglandin D synthase can lead to decreased sleep.
growth hormone
Growth hormone release occurs during the NREM sleep phase. NREM has the effect of promoting body growth and physical recovery. Growth hormone release can promote NREM sleep.
Regulation of visceral activity, instinctive behavior, and emotions by the nervous system
autonomic nervous system
Structure
Main function: regulate visceral activity
Composed of preganglionic neurons and postganglionic neurons
Sympathetic nerves: originate from the neurons in the lateral horns of the thoracic and lumbar segments of the spinal cord (T1-L3). Parasympathetic nerves: originate from the cranial nerve nuclei of the brainstem and neurons in the lateral corners of the sacral segments S2-4 of the spinal cord.
The reason why sympathetic nerve excitement has a wider effect, while parasympathetic excitement has a relatively limited effect
Sympathetic nerves are widely distributed and innervate almost all internal organs; parasympathetic nerves are relatively limited in distribution, and some organs have no parasympathetic innervation.
Sympathetic nerves have a higher degree of divergence when preganglionic and postganglionic neurons change, and one preganglionic neuron often has synaptic connections with multiple postganglionic neurons; parasympathetic nerves change when preganglionic and postganglionic neurons change. The degree of dispersion is low when
Function
Autonomic nervous system: regulates the activity of cardiac muscle, smooth muscle, and glands to maintain homeostasis
Originates from lateral horn of spinal cord, N1 receptor
The main transmitters of the sympathetic and parasympathetic nervous systems are acetylcholine and norepinephrine
basic unit of functional activity
stressful activities
In a quiet state, the autonomic nervous system continues to send impulses of a certain frequency, keeping the organs it controls in a certain degree of activity.
Dual dominance of the same effector
Many tissues and organs are under dual innervation by sympathetic and parasympathetic nerves, which are often antagonistic to each other or can be consistent.
Affected by the functional state of the effector
Different scope of action and physiological significance
The sympathetic nervous system has a wide range of activities, prompting the body to adapt to rapid changes in the environment.
The activity of the parasympathetic nervous system is relatively limited, and its significance is mainly to protect the body, rest and recover, promote digestion, accumulate energy, and enhance excretion and reproductive functions.
Central regulation of visceral activity
spinal cord
The spinal cord is the basic center for various visceral reflexes
brainstem
The medulla oblongata is known as the "life center", and the midbrain is the center of the pupillary light reflex.
hypothalamus
Regulation of autonomic nervous system activity
thermoregulation
Regulatory center: preoptic area-anterior hypothalamus
The brainstem is transected below the hypothalamus and the animal is unable to maintain its body temperature
water balance regulation
Osmoreceptors may be present in the anterior hypothalamus
Damage to the hypothalamus → increased water intake and polyuria; the area of the hypothalamus that controls water intake and the nuclei that control vasopressin secretion are functionally interconnected
Regulation of pituitary hormone secretion
The hypothalamus regulates the synthesis, storage and secretion of endocrine hormones in the adenohypophysis and neuropituitary gland through the pituitary portal system and the hypothalamic-pituitary tract, and indirectly affects visceral function.
biological rhythm control
suprachiasmatic nucleus of hypothalamus
Related to the regulation of pineal gland synthesis and secretion of melatonin
cerebral cortex
limbic lobe and limbic system,
Limbic lobe: the circumferential structure next to the corpus callosum at the junction between the medial cerebral hemisphere cortex and the brainstem.
Limbic system: the limbic lobe and the insula, temporal pole, orbital gyrus of the cerebral cortex, as well as the subcortical amygdala, septal area, hypothalamus, anterior thalamic nucleus and other structures
neocortex
It appears later in phylogeny and is the most differentiated structure on the lateral surface of the cerebral hemisphere.
Advanced center that controls visceral activity
Neural regulation of instinctive behavior and emotions
instinctive behavior
Definition: A behavior that is formed by animals in the process of evolution and is genetically fixed and is of great significance to the individual and the species.
feeding behavior
Feeding behavior is the basic activity of animals to maintain individual survival.
There is a feeding center in the ventrolateral nucleus of the hypothalamus; there is a satiety center in the ventromedial nucleus of the hypothalamus.
Almonds are involved in the regulation of feeding behavior
Amygdala central nucleus: promotes food intake
The cerebral cortex can control the activity of the feeding center to a certain extent
Neuropeptide Y, opioid peptides, food-enhancing factors, pancreatic polypeptide, norepinephrine, dopamine → promote food intake Leptin, neurotensin, cholecystokinin → inhibit feeding behavior
drinking behavior
caused by thirst
The generation of thirst is mainly related to the increase in plasma crystal osmotic pressure and the significant decrease in extracellular fluid volume.
sexual behavior
Basic activities for animals and humans to maintain species survival
mood
Definition: A special psychological experience and a fixed form of physical behavior expressed by humans and animals in response to environmental stimuli.
fear and anger
Fear manifestations: sweating, dilated pupils, curling up, looking left and right in an attempt to escape Angry manifestations: aggressive behavior, hair erection, baring teeth, growling
pleasure and pain
anxiety and depression
Anxiety: A complex emotional response of humans to potential challenges or threats in reality, characterized by the degree of anxiety consistent with the degree of actual threat
emotional physiological response
Changes in functional activity of the autonomic nervous system
Changes in functional activity of the endocrine system
Emotional and physiological reactions often cause changes in the secretion of multiple hormones
motivation and addiction
motivation
refers to an idea that inspires people to perform a certain behavior
The reward system and punishment system in the brain play an important role in motivating and inhibiting behavior.
addiction
Generally refers to the inability to control oneself and repeatedly taking something into the body regardless of its negative consequences.
Characteristics: Individuals clearly know that their actions are harmful but cannot control themselves.
Nervous system’s regulation of body movement
Overview of central regulation of movement
Classification of movements (movements vary in complexity and degree of conscious control)
reflex movement
The simplest and most basic form of movement is generally caused by fixed sensory stimulation and has a fixed movement trajectory.
Generally not under conscious control, the intensity of movement is related to the size of the stimulus. The number of neurons participating in the reflex circuit is small and the time required is short.
free movement
It is relatively complex. Under the control of the cerebral cortex, a conscious movement is carried out to achieve a certain purpose. Its movement direction, trajectory, speed and duration can be changed at will.
The procedure is complex and takes a long time
rhythmic movement
A form of movement that is between reflex and voluntary movement and has characteristics of both types of movement (breathing, refusing, walking)
Can start and stop at will
The basic structure and function of the central nervous system for movement regulation
Composed of three levels of neural structures,
The cerebral cortex contact area, basal ganglia and cortical cerebellum are the highest epithelium and are responsible for the overall planning of movement.
The motor cortex and spinocerebellar are at the intermediate level and are responsible for the coordination, organization and execution of movement
The brainstem and spinal cord are at the lowest level and are responsible for the execution of movement
Exercise requires posture as the basis
The spinal cord’s regulatory role in body movement
spinal shock
The spinal cord is the primary center for many body movement reflexes, and its reflex activities are controlled by higher centers
After the animal's spinal cord is separated from the high center, it temporarily loses its reflex activity and enters an unresponsive state - spinal shock
The spinal cord has the ability to complete some simple reflexes. The high center usually facilitates extensor reflexes and inhibits flexor reflexes.
Spinal cord anterior horn motor neurons and motor units
spinal motor neurons
alpha motor neuron
It receives incoming peripheral information from receptors on the trunk, limb skin, muscles, and joints, and at the same time receives information from high-level centers at all levels from the brainstem to the cerebral cortex, and finally sends out impulses of a certain form and frequency to the skeletal muscle nerves it controls. fibers of extrafusal muscles
It is the last highway for somatic motor reflexes
After integration, various movement information gathered into α motor neurons can trigger voluntary muscle movements, adjust posture, and coordinate the activities of different muscle groups, so that body movements can be carried out smoothly and accurately.
gamma motor neuron
It only receives downward regulation from high-level centers such as the cerebral cortex and brainstem, and the fibers it sends innervate the intrafusal muscle fibers of skeletal muscles.
The excitability is higher than that of alpha neurons, and they often discharge continuously at a higher frequency.
Function: Regulates the sensitivity of muscle spindles to stretch stimulation
beta motor neuron
Emitted fibers innervate both intrafusal and extrafusal muscles
Function not yet clear
motor unit
A functional unit composed of an alpha motor neuron and all the muscle fibers it innervates is called a motor unit
Size depends on the number of axon terminal branches of the alpha neuron
Spinal cord regulation of postural reflexes
Definition: The central nervous system changes the muscle tension of skeletal muscles or produces corresponding actions through reflexes to maintain or change the body's posture to avoid tipping.
Flexor reflex and contralateral extensor reflex
flexor reflex
When the skin of one limb of a vertebrate is subject to noxious stimulation, it can reflexively cause the flexor muscles of the joints of the stimulated limb to contract and the extensor muscles to relax, causing the limb to flex.
It has protective significance to avoid harm, but it is not a postural reflex.
The degree of limb flexion is related to the intensity of stimulation
contralateral extensor reflex
Definition: Further increase in stimulation intensity can cause extension of the contralateral limb in addition to flexion of the ipsilateral limb.
It is a postural reflex that maintains body balance.
stretch reflex
It refers to a reflex that causes the same stretched muscle to contract when a skeletal muscle with complete innervation is stretched by an external force.
stretch reflex receptors
Receptor: muscle spindle
The afferent nerve fibers of muscle spindles are type Ia and type II fibers; both types terminate in alpha motor neurons
Alpha and gamma neurons are often activated simultaneously under the control of higher centers
Type Ia fibers have spiral ends
Distributed in nuclear bag fibers and nuclear chain fibers
Type II fiber ends are flowery and branch-like
Distributed in nuclear chain fibers
The efferent fibers of gamma motor neurons innervate the contractile component of muscle fibers within the muscle spindle, and there are two types of terminals
Plate-like terminals innervating nuclear bag fibers
Pendant-like terminals, innervating nuclear chain fibers
A muscle spindle is a length receptor, a structure that the central nervous system uses to understand the relative position of a limb or body segment.
excitatory alpha motor neurons
Types of stretch reflex
tendon reflex (monosynaptic reflex)
The stretch reflex that occurs when a tendon is stretched rapidly
Muscle tone (polysynaptic reflex)
Refers to the stretch reflex that occurs when a tendon is slowly and continuously stretched. It shows that the stretched muscle is in a state of continuous and mild contraction, but does not show obvious movement.
Both extensor and flexor muscles have stretch reflexes
Weakened tendon reflexes and muscle tone or disappearance of activity indicate damage or interruption of the reflex arc. Increased tendon reflexes and muscle tone indicate lesions in the high central nervous system.
Tendon organs and counterstretch reflex
Tendon organ: a receptor that senses muscle tension; distributed between tendon collagen fibers and in series relationship with extrafusal muscle fibers
afferent fiber IB
Inhibit alpha motor neurons
Inhibition of the stretch reflex caused by tendon organ excitation - anti-stretch reflex
The anti-stretch reflex prevents the stretch reflex from being too strong and causing muscle strain
intersegmental reflex
After the high-level center loses contact, the spinal cord relies on the synergy of the upper and lower segments to complete certain reflex activities.
Example: Scratching reflex
Brainstem regulation of muscle tone and posture
Brainstem regulation of muscle tone
Brainstem reticular formation inhibitory and facilitative areas
inhibitory zone
There are areas in the reticular structure that inhibit muscle tone and muscle movement.
Smaller, located in the ventromedial part of the rostral reticular formation
facilitation area
Areas in the reticular structure that enhance muscle tone and movement
Larger, distributed in the central area of the brainstem; strong activity,
Remove brain stiffness
catalepsy
The muscle tone is obviously increased; the limbs are straight and as hard as pillars, the head and tail are raised, the spine is stiff, and the muscles are opisthotonic.
Mechanism: It is a manifestation of increased antigravity muscle tone
Cerebral rigidity is a sign of lesions involving the brainstem
type
Gamma rigidity: mainly achieved through the reticulospinal tract
Alpha catalepsy: Action occurs through the vestibulospinal tract
Brainstem control of posture
The postural reflexes involved in the brainstem include state reflexes and righting reflexes.
Regulation of body movements by the basal ganglia
Fiber connections of the basal ganglia
Neural circuits between the basal ganglia and cerebral cortex
Basal ganglia: neostriatum (caudate nucleus, putamen) globus pallidus
The neostriatum of the basal ganglia receives excitatory fiber projections from extensive areas of the cerebral cortex; efferent fibers arise from the medial part of the globus pallidus
Nigra-striatal projection system
functions of basal ganglia
It is the center for movement regulation in birds and other animals, and plays an important role in movement regulation.
Disorders associated with damage to the basal ganglia
Parkinson's disease (paralysis shaking)
Manifestations: Increased muscle tension throughout the body, muscle stiffness, reduced voluntary movements, slow movements, and dull facial expressions
Parkinson's disease is caused by degeneration of dopaminergic neurons in the substantia nigra
Huntington's disease (chorea)
Manifestation: Involuntary dance-like movements of the upper limbs and head, accompanied by symptoms such as decreased muscle tone, which appear when awake and worsen when emotional.
Cause: Neostriatal lesions
Depleting dopamine with reserpine relieves symptoms
Cerebellar regulation of body movements
Cerebellum: maintains body balance, regulates muscle tone, coordinates and forms voluntary movements
vestibule cerebellum
Mainly composed of the follicles, the most primitive part of the cerebellum
Participate in the regulation of body posture and balance functions; regulate the activities of extraocular muscles
After removal of the flocculus leaves, the body cannot maintain balance, resulting in a wide step base, unsteady standing, staggering gait, and easy falling, but the voluntary muscles are not affected.
Spinocerebellar
Composed of the intermediate zone of the anterior and posterior cerebellum
Function
Regulate ongoing activities and assist the cerebral cortex in timely control of voluntary movements.
The area that regulates muscle tension and inhibits muscle tension is the vermis in the anterior part of the cerebellum; the area that facilitates muscle tension is both sides of the anterior lobe of the cerebellum and the middle part of the posterior lobe.
After spinocerebellar damage, movement becomes clumsy and inaccurate, the strength, direction, and limit of voluntary muscle movement are disordered, and intention tremor occurs.
cortical cerebellum
The lateral part of the hemisphere does not receive peripheral sensory input, but mainly receives large areas of the cerebral cortex via the pontine nucleus.
stored procedure
Regulation of body movement by the cerebral cortex
motor area of cerebral cortex
main sports area
Including primary motor cortex (precentral gyrus), premotor area, secondary motor cortex
Premotor area includes premotor cortex and supplementary motor area
Participate in the planning of voluntary muscle movements
Other sports areas
subtopic
motor efferent pathways
Corticospinal and cortical brainstem tracts
Plays an important role in regulating the movements of the trunk, limbs, head and face
Performance of motor efferent pathway damage
Incomplete paralysis: Difficulty in maintaining body balance, walking and climbing, weakened movement ability, decreased muscle tone, but no tendon reflexes or hypertonia.
Motor conduction pathway damage
Flexible paralysis: stretch reflex weakens or disappears, muscles relax, and muscle atrophy gradually occurs, Babinski sign is negative, seen in spinal cord motor neuron damage
Spastic paralysis (hard paralysis): hyperactive stretch reflex, unclear muscle atrophy, positive Babinski sign, common in central injury
Check: Babinski sign
Signs of dorsiflexion of the thumb and abduction of the other four toes fanning out
Cerebral cortex regulation of posture
Remove the skin and stiffness; maintain the normal position of the limbs and maintain body balance
The sensory analysis function of the nervous system
Central analysis of somatic sensations
somatosensory pathways
prethalamic afferent system
When one side of the spinal cord is transected, impairment of proprioception and fine touch-pressure sensation occurs on the ipsilateral side below the injury level; impairment of pain, temperature, and gross touch-pressure sensation occurs on the contralateral side.
When a tumor occurs in the high spinal cord, superficial sensation loss in the neck or chest occurs first.
nuclei of thalamus
In addition to smell, all sensory afferent pathways use the thalamus as an important afferent relay station
Classification
The first type of cell group (collectively called the specific sensory nuclei)
After the projection fibers of the second-level sensory neurons are replaced by such nuclei, they project to the cerebral cortex.
Tertiary sensory neuron fibers project to the postcentral gyrus
Medial geniculate body (hearing) Lateral geniculate body (vision)
The second type of cell group (collectively known as contact nuclei)
Receive fibers from specific sensory relay nuclei and other subcortical centers, and then project to specific areas of the cerebral cortex.
Main function: Coordinate the connections between various senses in the thalamus and cerebral cortex
The third type of cell population (collectively referred to as non-specific projection nuclei)
Mainly includes the central nucleus, parafascicular nucleus, and lateral central nucleus
After multiple substitutions, it is diffusely projected to the entire cerebral cortex, which has the effect of maintaining and changing the excitability state of the cerebral cortex.
The parafascicular nucleus may be related to pain transmission. Stimulating the parafascicular nucleus of the human thalamus can aggravate pain, and damage to this area can relieve pain.
sensory projection system
specific projection system
Refers to the specific sensory relay nucleus and communication nucleus of the thalamus and their neural pathways to the cerebral cortex.
Sensory inputs from various parts of the body and various types are directed to specific areas of the cerebral cortex in a point-to-point manner.
non-specific projection system
Refers to the non-specific projection nuclei of the thalamus and their pathways that project to the cerebral cortex.
Function: Maintaining the excitement state of the cerebral cortex, which is the basis for the specific projection system to produce specific feelings.
Loss of function
Basis of sensory impairment in some patients with traumatic brain injury and brain disease
It is also part of the mechanism by which some anesthetic drugs produce anesthetic effects.
Cortical representative areas of somatosensory and sensory information processing
Transthalamic retroventral nucleus relay
Projected by a special projection system
somatosensory representative area
Body surface sensory representative area and its sensory information processing
first sensory area
Located at the back of the center
Features
The sensations of the body and limbs are cross-projected, but the projection of sensations on the head and face is bilateral.
The size of the projection area of the body surface sensory cortex mainly depends on the fineness of its sensory resolution. The finer the resolution, the larger the area.
The projection areas of different areas of the body surface in the postcentral gyrus have certain divisions and the overall arrangement is inverted.
Cortical sensory areas are plastic
second sensory area
Located on the upper wall of the lateral sulcus of the brain
area extending from the postcentral gyrus to the insula
In central damage, touch-pressure sensation usually does not disappear completely unless the area is very extensive.
Cortical representation area of proprioception and its processing of sensory information
The proprioceptive area is the motor area, located in the precentral gyrus (area 4)
Information processing of somatic pain
In addition to projecting the somatic pain sensation to the first and second sensory areas, many pain fibers project to extensive areas of the cerebral cortex via non-specific projection systems.
Central analysis of visceral sensations
Visceral sensory pathways
The afferent nerves for visceral sensation are autonomic nerves, including sympathetic and parasympathetic sensory afferents.
Visceral sensory representative area and visceral pain information processing
Visceral sensation is mainly pain