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MindMap Gallery Physiology - mind map of basic functions of cells
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Physiology - mind map of basic functions of cells
This is a mind map about physiology - the basic functions of cells, including the electrical activity of cells, the contraction of muscle cells, etc.
Edited at 2023-11-16 17:40:16
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Physiology - mind map of basic functions of cells
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- Outline
basic functions of cells
muscle cell contraction
striated muscle
Excitatory transmission at the neuromuscular junction of skeletal muscles
skeletal muscle-neuromuscular junction
specialized structure between motor nerve endings and the skeletal muscle cells they innervate
structure
Pre-joint membrane
synaptic vesicle
Acetylcholine (Ach)
Joint clearance
Post-joint membrane/end plate membrane
N2 type Ach receptor cation channel
acetylcholinesterase
Ach→choline acetic acid
excitement transfer process
End plate potential (EPP)
Net influx of Na depolarizes the endplate membrane
Belongs to local potential
Micro final plate potential (MEPP)
In the resting state, spontaneous release of single vesicles also occurs due to random movement of vesicles and causes a weak depolarization of the end plate potential.
Structural characteristics of striated muscle
Myofibrils and sarcomeres
myotubular system
composition
Horizontal tube (T tube)
The striated muscle cell membrane invaginates and extends deep to form
Longitudinal tube (L tube)
=Sarcoplasmic reticulum (SR)
calcium pump
Moves Ca from the cytosol into the SR against the concentration gradient
cisterna terminalis/junctional sarcoplasmic reticulum (JSR)
Features
High calcium ion concentration
The terminal membrane contains
Calcium release channel/raynodine receptor (RYR)
distributed
Corresponds to L-type calcium channels on the T-tubule membrane or sarcolemma
Secondary pipe
myocardium
T-tube unilateral terminal cistern
Triple tube
skeletal muscle
T-tube terminal pools on both sides
striated muscle cell contraction mechanism
Myofilament sliding principle
The myofibrils of striated muscle are composed of thick and thin myofilaments parallel to their direction. The shortening and elongation of the muscle are caused by the thick and thin myofilaments sliding against each other within the sarcomere, and the thick and thin myofilaments themselves The length does not change
Molecular structure of myofilaments
Thick myofilaments
myosin
stem
head
Hengqiao
ATPase activity
Can bind to actin
After being activated, twist towards the M line.
Thin myofilaments
actin
myosin binding site
Binds to myosin cross-bridge
Tropomyosin
Covering myosin binding sites
Troponin
Maintain tropomyosin sites during muscle relaxation
Troponin T (TnT)
linked to tropomyosin
Troponin I (TnI)
linked to actin
There is a Ca binding site, which in turn causes the tropomyosin site to move.
Troponin C (TnC)
Classification
contractile protein
myosin, actin
regulatory protein
tropomyosin, troponin
myofilament sliding process
cross bridge period
The process in which myosin cross-bridge binds to actin, twists, and resets
The operating pattern of the cross-bridge cycle and the performance of muscle contraction
substance
The process of converting chemical energy obtained from decomposing ATP into mechanical energy through the interaction between actin and myosin
The tension produced by muscle shortening is determined by the number of cross-bridges bound to actin at a certain moment, and the speed of muscle shortening depends on the length of the cross-bridge period
Excitation-contraction coupling in striated muscle cells
An intermediary mechanism that links the electrical excitation process of striated muscle cells to generate action potentials and the mechanical contraction of myofilament sliding.
coupling factor
Ca
parts
Triple tube or double tube
The basic steps
Factors affecting striated muscle contraction efficiency
muscle contraction efficiency
The amount of tension produced when a muscle contracts, the degree of shortening, and the speed at which the tension or shortening is produced
Classification
Isometric contraction
isotonic contraction
Common forms of contraction
First isometric contraction, then isotonic contraction
include
load
front load
The load a muscle undergoes before it contracts
Determines the length of the muscle before contraction—initial length
passive tension
The force that causes the muscle to stretch and return elastically during preload
active tension
In isometric contraction, the tension generated by active muscle contraction under different initial length conditions
optimal initial length
Initial length that produces maximum shrinkage tension
Corresponding sarcomere length
2.0～2.2 micron
afterload
The load a muscle undergoes after contraction
= Contractile tension produced by isotonic contraction
Muscle contractility
Refers to the intrinsic characteristics of muscles that have nothing to do with preload and afterload and can affect cell contraction efficiency.
sum of shrinkage
The superimposed nature of myocyte contraction
Sum of multiple fibers (=sum of multiple motor units)
The superimposed effect of simultaneous contraction of multiple muscle fibers
motor unit
A motor unit of skeletal muscle composed of all the muscle fibers innervated by a motor neuron and its axonal branches
size principle
sum of frequencies
The additive effect of increasing skeletal muscle contraction frequency
single contraction
When the action potential frequency is very low, a complete contraction and relaxation process occurs after each action potential.
cause
The time required to complete a contraction process is much longer than the time of the action potential → the frequency of the action potential increases to a certain level → the contraction triggered by the latter action potential can be superimposed on the previous contraction
Classification
incomplete tetanic contraction
The subsequent contraction is superimposed on the diastole of the previous contraction
full tetanic contraction
The subsequent contraction process is superimposed on the systolic period of the previous contraction.
Material transport function of cell membrane Transmembrane transport of cell membrane and materials Transmembrane transport of cell membrane and materials
cell electrical activity
cell bioelectricity
Cells are accompanied by electrical phenomena when carrying out life activities
membrane potential
A manifestation of cellular bioelectricity, produced by the flow of some charged ions across membranes
Classification
Resting potential (RP)
The potential difference between the inner negative and outer positive that exists on both sides of the cell membrane in the resting state
Determination
polarization
At rest, both sides of the cell membrane are in a stable state of positive outside and negative inside.
hyperpolarization
The process or state of increasing resting potential
depolarization
The process or state of decreasing resting potential
reverse polarization
The potential within the membrane becomes positive and the polarity on both sides of the membrane is reversed.
repolarization
The process by which the cell membrane returns to its resting potential after depolarization
production mechanism
Ion concentration difference and equilibrium potential on both sides of the cell membrane
The formed transmembrane electric field has exactly the opposite effect on the movement of charged ions across the membrane than the concentration difference, and will prevent the ions from continuing to diffuse.
Electro-chemical driving force
The algebraic sum of the transmembrane electric field and the ion concentration difference, the two driving forces that affect the movement of charged ions
Potential difference driving force = concentration difference driving force → electro-chemical driving force is zero → net ion diffusion is zero
equilibrium potential
The potential difference across the membrane when the net diffusion of ions is zero
Relative permeability of cells to ions at rest
Among various ions, the higher the permeability of a certain ion, the closer the resting potential is to the equilibrium potential of the ion.
In the quiet state, the K permeability of the cell membrane is the highest, and the resting potential is closer to the K equilibrium potential.
Actual measured value of resting potential＜K equilibrium potential
reason
The cell membrane also has a certain degree of permeability to K at rest
Sodium pump electrogenesis
The sodium pump maintains the concentration difference between Na and K on both sides of the cell membrane through active transport.
Every time 1 ATP is decomposed, 3 Na are pumped out and 2 K are pumped back → the negative value of the potential in the membrane increases
Factors affecting resting potential levels
Extracellular fluid K concentration
Extracellular K increases → K equilibrium potential decreases → Resting potential decreases
The relative permeability of the membrane to K and Na
sodium pump activity level
action potential (AP)
Refers to a rapid membrane potential that can propagate to a distance after cells receive effective stimulation based on the resting potential.
Potential
Spike potential (action potential marker)
back potential
afterdepolarization potential (negative afterpotential)
Afterhyperpolarization potential (positive afterpotential)
Features
all or nothing phenomenon
The given stimulus must reach a certain intensity (threshold potential) → generate an action potential
Beyond this intensity, no matter how great the stimulus is, what determines the amplitude and speed of action potential depolarization is only the properties of the Na channel itself and the electrochemical driving force of sodium ions.
propagation without attenuation
Amplitude and waveform
Pulse delivery
production mechanism
Electro-chemical driving forces and their changes
Expression of electrochemical driving force
Em (membrane potential)-Ex (equilibrium potential)
Positive sign outward flow, negative sign inward flow
The larger the difference, the greater the electrochemical driving force on the ions.
Changes in cell membrane permeability during action potentials
Changes in sodium and potassium conductance (Gx)
Process: When the cell is effectively stimulated, the GNa of the cell membrane first increases → Na enters the cell driven by a larger electrochemical driving force, and the membrane depolarizes → the membrane depolarization reaches a certain level (threshold potential), and the depolarization and Positive feedback occurs between GNa, and the membrane potential rises sharply, forming an ascending branch of the action potential until it is close to the Na equilibrium potential → GNa decreases rapidly after depolarization reaches the peak, and GK gradually increases → K rapidly flows out under the strong outward driving force →The membrane rapidly repolarizes to form the descending branch of the action potential
The essence of membrane conductance changes
Opening and closing of ion channels in membranes
Functional state of ion channels
Sodium ions
Resting state (steady state)
The membrane potential level remains at the resting potential level when the channel is not yet open.
Activation door (m door) is fully closed
The deactivation door (h door) is close to opening but cannot conduct
Active state (transient)
A state in which voltage-gated sodium channels open immediately upon rapid depolarization of the membrane
Door m is open, door h is closed
Inactive state (steady state)
A state in which a channel no longer responds to depolarizing stimuli after being activated
The h gate is completely closed in a time-dependent manner, and the m gate is open but cannot conduct.
Only through membrane repolarization can voltage-gated sodium channels return to their resting state.
potassium ions
Activation gate (n gate)
trigger
threshold stimulus
stimulus equivalent to threshold intensity
suprathreshold stimulus
subliminal stimulation
It can also cause some sodium channels to open and cause slight depolarization, but this is quickly offset by the enhanced K outflow (potassium leak channel).
stimulus amount
intensity of stimulation
duration of stimulation
Stimulation intensity-time rate of change
threshold intensity
The minimum stimulation intensity that can produce action potentials
effective stimulation
Threshold or suprathreshold stimulation that causes cells to generate action potentials
Threshold potential (TP)
Only when certain stimuli cause the positive charge in the membrane to increase, that is, the negative potential decreases (depolarization) and rapidly decreases to a critical value, the sodium conductance of the cell membrane can be activated by positive feedback to form an action potential.
This membrane potential that triggers an action potential is called the threshold potential.
Factors Affecting Threshold Potential Levels
Distribution density and functional status of voltage-gated sodium channels in cell membranes
density
High sodium channel density → requires less membrane depolarization → low threshold potential level, close to resting potential = high excitability
functional status
resting, activation and deactivation
Extracellular calcium levels (stabilizer)
Increased extracellular Ca concentration → decreased membrane permeability to Na → increased threshold potential = decreased excitability
spread
Propagation of action potentials in the same cell
conduction
The action potential generated in a certain part of the cell membrane can propagate throughout the cell along the cell membrane without attenuation.
local current
The current between an excited area and an adjacent unexcited area
substance
The cell membrane in turn regenerates the action potential
Myelinated and unmyelinated nerve fibers
propagation of action potentials between cells
Gap junctions (electrical synapses)
Connector
Features
Excitement spreads quickly
Two-way communication
Excitability and its changes
Excitability
The ability or characteristic of the body's tissues or cells to respond to stimuli
Metrics
The smaller the threshold, the higher the excitability
The larger the threshold, the lower the excitability
excited
When the body is stimulated, the functional activity changes from weak to strong or from relatively static to a more active reaction process
excitable cells
Sensitive to electrical stimulation = action potential can be used as a marker of excitement
nerve cells
muscle cells
gland cells
Changes in excitability after cell excitation
absolute refractory period
During the initial period of time after excitement occurs, no matter how strong the stimulus is, the cells cannot be excited again.
Features
The threshold is infinite and the excitability is zero.
reason
When excitement occurs, most sodium channels are already activated and there is no reactivation.
After stimulation, most sodium channels immediately enter an inactivated state and cannot be activated again by stimulation.
relative refractory period
After the absolute refractory period, the excitability of the cells gradually recovers, and excitation can occur after receiving stimulation again, but the stimulation intensity must be greater than the original threshold.
Features
A period in which excitability gradually returns from zero to near normal
Reason (lower excitability)
Although the inactivated voltage-gated sodium channels have begun to be resurrected, the number of reactivated channels is small (some are still in the process of reactivation)
Suprathreshold stimulation is therefore required to elicit action potentials
supernormal period
After the relative refractory period, some cells will experience a period of mildly increased excitability.
reason
Voltage-gated sodium channels have been basically resurrected, but the membrane potential has not yet completely returned to the resting potential and is closer to the threshold potential level
Only subthreshold stimulation can depolarize the membrane to reach the threshold potential and trigger excitement again.
low normal period
After the supernormal period, some cells show a slight decrease in excitability.
reason
Voltage-gated sodium channels are fully resurrected, but the membrane potential is in a slightly supercharged state, and the horizontal distance from the threshold potential increases
Suprathreshold stimulation is required to cause cells to become excited again
electrotonic potential and local potential
Passive electrical properties of cell membranes and cytoplasm
The electrical properties of the cell membrane and cytoplasm as a static electrical component
including resting state
film capacitor
big
membrane resistance
Small
Axial resistance
The smaller the diameter and the longer the major axis, the greater the axial resistance.
electrotonic potential
The membrane potential determines its spatial distribution and temporal variation by the passive electrical properties of the membrane.
Propagation range and generation speed of electrotonic potential
Characteristics of electrotonic potential
No ion channel activation and membrane conductance changes
Graded potential, the amplitude of electrotonic potential increases with the intensity of stimulation.
Attenuated conduction, which decreases as the propagation distance increases
Potentials can be fused
When the amplitude of the depolarizing electrotonic potential reaches a certain level, it can cause a small number of voltage-gated channels in the membrane to open, forming a local potential.
local potential
Under the action of neurotransmitters or the stimulation of electrotonic potential, some ion channels in the cell membrane may open, forming a mild depolarization or hyperpolarization reaction.
After this kind of cell is stimulated, the membrane potential change is formed by the participation of the active characteristics of the membrane, that is, the opening of some ion channels, and cannot propagate to long distances, which is called local potential.
local excitement
Depolarizing membrane potential fluctuations produced by small amounts of sodium channel activation
Local potential characteristics and significance
Electrical Characteristics of Electrotonic Potential
Graded potential, amplitude related to stimulus intensity
attenuated conduction
No refractory period, reactions can be additive
space sum
time sum
(The summation can depolarize the cell membrane to reach the threshold potential, thereby triggering an action potential)