Muscle Tissue

Flashcards covering key vocabulary related to muscle tissue physiology.

Neuromuscular Junction

The site of communication between a neuron and a muscle cell, where an action potential from the neuron creates an action potential in the muscle cell.

Resting Membrane Potential

The membrane potential of a cell at rest, before any stimulation.

Depolarization

When the membrane potential becomes less negative (more positive).

Repolarization

When the membrane potential returns to its resting value.

Hyperpolarization

When the membrane potential becomes more negative than its resting value.

Excitation-Contraction Coupling

The process by which an action potential from a motor neuron causes muscle contraction.

Troponin

The molecule to which Calcium binds, causing a change in its shape, which then pulls tropomyosin out of the way.

Tropomyosin

A molecule that blocks the myosin-binding sites on the actin thin filaments in resting muscle.

Motor Unit

Consists of a single motor neuron and all the muscle fibers it innervates.

Recruitment

The smooth and steady increase in muscle tension resulting from increasing the number of active motor units.

Twitch

A single neural stimulation that produces a brief contraction.

Latent Period

The time delay between the action potential and the start of contraction.

Contraction Phase

The period when calcium ions bind and tension builds to a peak.

Relaxation Phase

When calcium levels fall, active sites are covered, and tension decreases.

Fast Fibers

Reach peak tension quickly, have densely packed myofibrils, few mitochondria, large glycogen reserves, and are supported by anaerobic metabolism.

Slow Fibers

Take longer to reach peak tension, have numerous mitochondria, are surrounded by numerous capillaries, contain myoglobin, and are supported by aerobic metabolism.

Intermediate Fibers

Similar to fast fibers but more resistant to fatigue, with an intermediate capillary network and more mitochondria.

Wave Summation

Repeated stimulations before the end of the relaxation phase, causing increasing tension or summation of twitches.

Incomplete Tetanus

Continuing rapid stimulation where periods of relaxation are brief and twitches reach a maximum level of tension.

Complete Tetanus

High stimulation frequency where the muscle never begins to relax and is in continuous contraction.

Rigor Mortis

A fixed muscular contraction after death due to the unavailability of ATP.

Muscle Tone

Resting tension in a skeletal muscle, which keeps the muscle ready to respond, helps stabilize joints, and maintain posture.

Isotonic Contraction

A skeletal muscle changes length, resulting in motion. Can be concentric (muscle shortens) or eccentric (muscle lengthens).

Isometric Contraction

Skeletal muscle length remains the same; muscle maintains position but contraction is initiated.

Concentric Contraction

Contraction of the muscle results in the shortening of the muscle; muscle tension > load.

Eccentric Contraction

Muscle is contracted but its force is less than the load, resulting in the lengthening of the muscle; muscle tension < load.

Cardiac Muscle

Differs from skeletal muscle; cells are smaller, have only 1 nucleus, are joined by gap junctions, and some are autorhythmic.

Smooth Muscle

Involuntary muscle with spindle-shaped cells, a single nucleus, no striations, and exhibits slow, prolonged contractions.