Physiology I - Cell Membrane and Nerve Electrophysiology

Comprehensive vocabulary flashcards covering cellular membrane transport, ion channels, action potential stages, electrical equations, and the microanatomy of muscle types.

Cell Membrane

A selectively permeable lipid bilayer composed of proteins and carbohydrates that regulates the movement of water and water-soluble molecules into and out of the cell.

Mitochondria

A membrane-bound organelle featuring a lipid bilayer that serves as the site of aerobic/cellular respiration.

Diffusion (Passive Transport)

Movement that occurs down a concentration gradient ($[highest] ightarrow [lowest]$) through the lipid bilayer or a protein channel/carrier without requiring additional energy.

Active Transport

Movement of molecules or ions against a concentration gradient that involves a protein carrier and requires energy, such as $ATP$.

Simple Diffusion

A type of diffusion where movement occurs through membrane openings or intermolecular spaces without a carrier protein; involves lipid-soluble substances like Oxygen, Nitrogen, Carbon Dioxide, and Alcohols.

Facilitated Diffusion

Diffusion through a membrane aided by a specific carrier protein or protein channel, providing specificity to the membrane for substances like Water, Ions, Glucose, and Amino Acids.

Vmax

The maximum rate of diffusion achieved when a carrier protein is involved in transport.

Leak Channels

Channels that are more permeable but less selective, where transport is determined by the size, shape, and charge of the channel and ions.

Voltage-gated Channels

Gated channels that open in response to a voltage change inside the cell.

Mechanically-gated Channels

Gated channels also known as mechanoreceptors that open in response to a deformation of the membrane.

Ligand-gated Channels

Gated channels that open in response to a chemical or ligand signal.

Osmosis

The movement of $H_2O$ across a semipermeable membrane toward the area of higher solute concentration.

Primary Active Transport

Transport using $ATP$ directly as an energy source, such as in the $Na^+-K^+$ Pump.

Secondary Active Transport

Transport where the concentration gradient of one ion/molecule provides the energy source to move another substance.

Nernst equation

Calculates the membrane potential for a single ion: E_{ion} ext{ (mV)} = rac{61}{z} imes ext{log}{10} ext{( [ion]}{out} ext{ / [ion]}_{in} ext{)}, where $z$ is the charge of the ion.

Goldman-Hodgkin-Katz equation

An equation used to calculate membrane potential ($Vm$) by considering multiple ions and their respective membrane permeabilities.

Na+/K+ ATPase Pump

A pump that maintains the resting membrane potential by moving $3 ext{ Na}^+$ out of the cell and $2 ext{ K}^+$ into the cell, resulting in a net $-1$ charge inside.

Action Potential

A rapid, all-or-nothing, non-decremental change in voltage across a cell membrane used for long-distance communication.

Depolarization

The phase of an action potential where the membrane potential becomes more positive as a result of rapid $Na^+$ entry into the cell.

Repolarization

The phase where $Na^+$ channels close and slower $K^+$ channels open, allowing $K^+$ to leave the cell and restore the negative membrane potential.

Hyperpolarization

The phase where $K^+$ channels remain open and additional $K^+$ leaves the cell, making the membrane potential more negative than its resting state.

Absolute Refractory Period

A period that prevents retrograde movement of the action potential because $Na_V$ channels are inactive and $K_V$ channels are open.

Saltatory Conduction

Action potential movement through myelinated neurons, which increases conduction velocity by increasing resistance to ion leakage.

Skeletal Muscle

Voluntary, striated, multinucleate muscle with elongated parallel cells and $Z$ disks, characterized by rapid and vigorous contractions.

Cardiac Muscle

Involuntary, striated muscle with short branched fibers and intercalated disks (containing desmosomes and gap junctions) that contracts rhythmically.

Smooth Muscle

Involuntary, non-striated, uninucleate muscle with fusiform cells that perform slow and sustained contractions in blood vessel walls and hollow organs.

Sarcoplasmic Reticulum

A muscle fiber structure that stores $Ca^{2+}$.

Myosin

The thick filament of a myofibril composed of heavy and light chains, featuring globular heads that interact with actin and house the site of myosin ATPase.

Actin

The thin filament chain tethered to the $Z$ disk, consisting of Filamentous actin ($F ext{ actin}$), Globular actin ($G ext{ actin}$), Troponin, and Tropomyosin.

Titin

An elastic fiber that keeps actin and myosin in place and allows the sarcomere to return to its original shape.