Muscle Tissue Anatomy & Physiology Flashcards

This set of vocabulary flashcards covers the anatomy and physiology of skeletal, cardiac, and smooth muscle tissues, focusing on contraction mechanisms, tension types, and responses to stimuli.

Muscle tension

The force generated when a muscle is stimulated to contract.

Myogram

A laboratory graph used to measure and record muscle tension over time.

Muscle twitch

A brief contraction of a muscle in response to a single stimulus.

Threshold

The minimum voltage required to trigger a muscle twitch.

Latent period

The time after a stimulus but before contraction begins, during which there is no change in tension.

Contraction period

The phase during a muscle twitch when tension is increasing as power strokes pull thin filaments.

Relaxation period

The phase of a twitch when tension decreases to baseline, beginning with the release of crossbridges.

Recruitment

Also known as multiple motor unit summation, it is the process where increasing stimulating voltage results in more motor units being contracted to exhibit varying degrees of force.

Wave summation

Also known as temporal summation, this occurs when contractile forces are added because relaxation is not completed before the next stimulus arrives; typically occurs at $20$ to $50$ stimuli per second.

Incomplete tetany

A state where stimulation frequency is increased such that tension increases and twitches partially fuse.

Tetany

A smooth, continuous tension trace without relaxation, occurring at very high frequencies such as $40$ to $50$ stimuli per second.

Muscle tone

The resting tension in a muscle generated by involuntary nervous stimulation of random motor units.

Isometric contraction

A contraction where muscle tension is insufficient to overcome resistance, resulting in no change in muscle length.

Isotonic contraction

A contraction where muscle tension overcomes resistance, resulting in movement and a change in muscle length.

Concentric contraction

A type of isotonic contraction where the muscle shortens as it contracts.

Eccentric contraction

A type of isotonic contraction where the muscle lengthens as it contracts.

Length-tension relationship

The principle that the tension a muscle produces depends on its length at the time of stimulation, with maximum force occurring at resting length.

Muscle fatigue

A reduced ability to produce muscle tension, primarily caused by a decrease in glycogen stores.

Hypertrophy

An increase in muscle size due to the increased synthesis of contractile proteins, often resulting from resistance exercise.

Hyperplasia

A limited increase in the number of muscle fibers.

Atrophy

A decrease in muscle size due to lack of use, which can become permanent if extreme.

Fibrosis

A condition associated with aging where muscle mass is replaced by dense regular connective tissue.

Intercalated discs

Structures that join the ends of neighboring cardiac muscle fibers, containing desmosomes and gap junctions.

Caveolae

Flasklike invaginations of the smooth muscle sarcolemma that increase surface area.

Dense bodies

Points in smooth muscle where intermediate filaments interact within the sarcoplasm.

Dense plaques

Points where intermediate filaments attach to the inner sarcolemma in smooth muscle cells.

Latchbridge mechanism

A unique mechanism in smooth muscle where myosin attaches to actin for an extended time without consuming extra ATP.

Calmodulin

A protein in smooth muscle that binds to $Ca^{2+}$ to trigger the contraction process.

Myosin light-chain kinase (MLCK)

An enzyme activated by the calcium-calmodulin complex that phosphorylates myosin heads in smooth muscle.

Myosin light-chain phosphatase

The enzyme required for smooth muscle relaxation by dephosphorylating the myosin head.

Myogenic response

A smooth muscle contraction that occurs in reaction to being stretched.

Stress-relaxation response

The relaxation of smooth muscle that occurs after a period of prolonged stretch.

Multiunit smooth muscle

A category of smooth muscle where cells are arranged in units that receive individual stimulation, such as in the iris or arrector pili.

Single-unit smooth muscle

The most common category of smooth muscle, where cells are linked by gap junctions and contract in unison.

Varicosities

Swellings of autonomic neurons containing synaptic vesicles that stimulate single-unit smooth muscle.