Phospholipids>70%, cholesterol<30%, glycolipids<10%; Content in phospholipids: phosphatidylcholine (outer layer of membrane) > phosphatidylserine > phosphatidylethanolamine > phosphatidylinositol (the lowest, can be used as a donor for intracellular second messenger inositol triphosphate IP3 and diacylglycerol DG)

Surface membrane proteins: 20%~30%, mainly attached to the inner surface of the cell membrane; Integral membrane proteins: 70% to 80%, whose peptide chains pass through the membrane lipid bilayer once or repeatedly; generally speaking, proteins related to substance transmembrane transport and receptor functions are integral membrane proteins, such as carriers , channels, ion pumps, G protein-coupled receptors

Mainly some oligosaccharide and polysaccharide chains, combined with membrane proteins or membrane lipids in the form of covalent bonds to form glycoproteins or glycolipids

The diffusion of substances across the membrane from the high-concentration side of the plasma membrane to the low-concentration side through the interstitial space between lipid molecules. Oxygen, carbon dioxide, ethanol, urea, glycerin and other fat-soluble substances; Determining factors: concentration difference on both sides of the membrane, membrane permeability to the substance

It refers to the transmembrane transport of non-lipid-soluble small molecule substances or charged ions with the help of transmembrane proteins along the concentration gradient and potential gradient.

Certain substances are transported across membranes against concentration gradients and potential gradients with the help of membrane proteins and energy provided by cell metabolism. According to whether membrane proteins directly consume energy, they are divided into primary active transport and secondary active transport.

Enter the cell

Coming out of the cell

Chemically gated channels have the functions of both receptors and ion channels, also known as ion channel receptors, eg nicotinic acetylcholine receptors, ionotropic glutamate receptors Voltage-gated channels and mechanical-gated channels have "ion-promoting" signal transduction functions similar to chemical-gated channels. They can also be classified as ion channel-type receptors, but only accept electrical signals or mechanical signals.

G protein-coupled receptor: refers to a type of receptor that, after being activated by a ligand, acts on the G protein coupled to it, and then triggers a series of cascade reactions dominated by signaling proteins to complete transmembrane signal transduction. The signaling molecules involved in this type of transduction include a variety of signaling proteins (G protein-coupled receptors, G proteins, G protein effectors, protein kinases) and second messengers

Refers to a membrane receptor that itself has enzymatic activity or is combined with an enzyme; Structural features: Each receptor molecule has only a single transmembrane segment, the extracellular domain contains a site that can bind ligands, and the intracellular domain has enzymatic activity or a site that can bind to an enzyme.

A single transmembrane receptor. The intracellular domain has no enzymatic activity. However, once the extracellular domain binds to a ligand, its intracellular domain can recruit kinases or adapter proteins in the cytoplasm to activate downstream signals that do not involve classical second messengers. transduction pathways; Mainly regulates the functions of hematopoietic cells and immune cells

Intracellular receptors are collectively called nuclear receptors

It is a specialized structure between motor nerve endings and the skeletal muscle cells they innervate. It is composed of pre-joint membrane, post-joint membrane and joint gap. prejunctional membrane: part of the terminal membrane of a motor nerve axon Post-joint membrane: The skeletal muscle cell membrane opposite to the pre-joint membrane, also called the end plate membrane, is a shallow groove that is depressed inward. The end plate membrane at the bottom of the groove is sunk inward to form many wrinkles.

The AP transmitted from the motor nerve fiber to the axon terminal triggers the outflow of calcium ion-dependent synaptic vesicles from the prejunction membrane and releases Ach into the junction gap. Ach activates the nitrogen molecule type Ach receptor cation channel on the terminal plate membrane. produce changes in membrane potential

The intermediary mechanism that links the electrical excitation process of AP produced by striated muscle cells with the mechanical contraction of myofilament sliding.

1. Action potential conduction of T-tubule membrane: The action potential on the sarcolemma is transmitted along the T-tubule membrane to the inside of the cell, and activates L-type calcium channels in the T-tubule membrane and sarcolemma.

2. Calcium ion release in the JSR: Depolarization of the sarcolemma causes skeletal muscle to trigger a calcium release mechanism through conformational changes. In the myocardium, calcium induces a calcium release mechanism, causing calcium ions in the JSR to be released into the cytoplasm.

3. Calcium ions trigger myofilament sliding: The increase in cytoplasmic calcium ion concentration prompts calcium ions to bind to Tnc and trigger muscle contraction.

4. Calcium ions are taken back up by JSR: In skeletal muscle, almost all the calcium ions in the cytoplasm are taken back into the SR through the calcium pump in the activated LSR membrane. Most of the calcium ions in the myocardial cytoplasm are taken up by the calcium pump in the LSR membrane Recycled, a small part is discharged to the outside of the cell by the sodium ion-calcium ion exchanger and calcium pump in the sarcolemma

The potential difference between the inner negative and outer positive that exists on both sides of the cell membrane in the resting state

Basic Cause: Transport of charged ions across membranes; In a quiet state, the permeability of the cell membrane to various ions is highest with potassium ions, and the resting potential is closer to the equilibrium potential of potassium ions (because the cell membrane still has a certain permeability to sodium ions at rest, the actual measurement is slightly less than equilibrium potential of potassium ions)

After cells receive effective stimulation based on the resting potential, they generate a rapid membrane potential fluctuation that can propagate to a distance.

Go to extremes

Repolar phase

Peak potential

back potential

The “all or nothing” phenomenon

propagation without attenuation

Pulse delivery

Two factors: 1. Electro-chemical driving force 2. Permeability of the cell membrane to ions; The generation of action potential is the result of changes in the resting potential.

Threshold intensity: The minimum stimulus that can cause cells to generate action potentials. Stimuli equivalent to the threshold intensity are called threshold stimuli; stimuli greater than or less than the threshold intensity are called suprathreshold stimuli and subthreshold stimuli respectively. Threshold potential: The critical value of membrane potential that can trigger action potential is called threshold potential; The intensity of the threshold stimulus is just enough to depolarize the resting potential of the cell to the threshold potential level.

Spread on the same cell

spread between cells

Periodic changes in excitability after cell excitation

The membrane potential whose spatial distribution and temporal changes are determined by the passive electrical properties of the membrane is called point tension potential.

Described by a space constant, it refers to the spatial distance spread when the membrane potential decays to 37% of its maximum value, represented by l; Increasing the membrane resistance or reducing the axial resistance can increase l

The time constant is used to describe the time change characteristics of the electrotonic potential, which refers to the time required for the membrane potential to rise to 63% of the maximum value during charging or drop to 37% of the initial value during discharge, represented by t; Reducing membrane capacitance shortens the time it takes for the electrotonic potential to reach a stable value.

Injecting a positive charge into a cell exhibits a depolarizing electrotonic potential; injecting a negative charge into a cell exhibits a hyperpolarizing electrotonic potential.

graded potential

attenuating conduction

Potentials can be fused

After the cell is stimulated, the change in membrane potential that is formed by the active characteristics of the membrane, that is, the opening of some ion channels, and cannot propagate to long distances is called local potential.

graded potential

attenuating conduction

no refractory period