Voltage Gated Channels and Crossbridge Cycling

Flashcards covering key concepts related to voltage gated channels, action potentials, and crossbridge cycling from the provided lecture notes.

Threshold potential

The critical level to which a membrane potential must be depolarized to initiate an action potential, around -55mV.

Voltage gated sodium channels

Channels that open in response to membrane depolarization, allowing sodium ions to enter the cell and cause depolarization.

Voltage gated potassium channels

Channels that open to allow potassium ions to exit the cell, contributing to repolarization and hyperpolarization after an action potential.

After-hyperpolarization

The phase following an action potential when the membrane potential temporarily becomes more negative than the resting potential.

Self-propagation of action potentials

The process by which an action potential is regenerated along the axon, allowing it to travel without diminishing.

Refractory period

The time following an action potential during which the neuron cannot fire another action potential.

Crossbridge cycling

The process by which myosin heads attach to actin filaments, pulling them during muscle contraction.

Calcium pumps

Proteins that actively transport calcium ions back into the sarcoplasmic reticulum, aiding muscle relaxation.

Acetylcholine's role

A neurotransmitter that stimulates muscle contraction by initiating action potentials in muscle fibers.

Tetany

A condition characterized by prolonged muscle contraction due to a high frequency of action potentials leading to excessive calcium release.

Sarcoplasmic calcium levels

The concentration of calcium ions in the sarcoplasm, crucial for initiating muscle contraction and relaxation.

ATP in crossbridge cycling

A necessary molecule that provides energy for the myosin heads to detach and prepare for another cycle.

Positive feedback of sodium influx

The phenomenon whereby the influx of sodium ions during depolarization causes further opening of sodium channels.

Calcium's controlled release

The process allowing for transient spikes in calcium concentration during action potentials, crucial for initiating muscle contraction.

Factors affecting sarcomere shortening

Action potential frequency, acetylcholine levels, sarcoplasmic calcium concentration, and sarcoplasmic ATP availability must all support continued muscle contraction.