Muscle Tissue & Physiology – Lecture Review

30 question-and-answer flashcards covering muscle tissue types, anatomy, physiology, contraction mechanics, metabolism, fiber types, and special features of skeletal, cardiac, and smooth muscle.

What are the three types of muscle tissue in the human body?

Skeletal muscle, smooth muscle, and cardiac muscle.

Which connective-tissue layer surrounds individual muscle fibers?

The endomysium.

Bundles of muscle fibers are called , and are wrapped by which connective tissue layer?

Fascicles; the perimysium wraps each fascicle.

What plasma membrane surrounds a skeletal muscle fiber?

The sarcolemma.

Name the functional unit of a skeletal muscle fiber located between two Z-lines.

The sarcomere.

Which ion binds to troponin to expose the active sites on actin?

Calcium ions (Ca++).

At the neuromuscular junction, which neurotransmitter is released by the axon terminal?

Acetylcholine (ACh).

What tiny gap does ACh diffuse across to reach receptors on the muscle fiber?

The synaptic cleft.

What structures form a muscle fiber ‘triad’?

One T-tubule and two terminal cisternae of the sarcoplasmic reticulum (SR).

During the power stroke of muscle contraction, which molecules leave the myosin head?

The inorganic phosphate (Pi) and ADP.

What causes detachment of the myosin head from actin?

Binding of a new ATP molecule to the myosin head.

How is Ca++ removed from the sarcoplasm during muscle relaxation?

It is actively pumped back into the sarcoplasmic reticulum (SR).

According to the sliding filament model, what happens to the I-band during full contraction?

The I-band becomes smaller (it shortens).

Which immediate energy source can regenerate ATP for about 15 seconds of activity?

Creatine phosphate.

In the absence of oxygen, pyruvic acid is converted into what molecule, potentially contributing to fatigue?

Lactic acid.

Where does aerobic respiration occur in the muscle cell?

In the mitochondria.

Differentiate isotonic and isometric contractions.

Isotonic contractions change muscle length to move a load; isometric contractions generate tension without changing muscle length because the load is too great.

At what percentage of resting sarcomere length is maximal tension produced?

When sarcomeres are 80 %–120 % of their optimal length.

List the three phases of a single muscle twitch in the correct order.

Latent period, contraction phase, relaxation phase.

What is wave summation in skeletal muscle?

The additive effect of successive stimuli before the muscle fully relaxes, increasing tension.

When stimulus frequency is so high that no relaxation occurs between contractions, the condition is called .

Tetanus (complete tetanus).

What staircase-like increase in tension results from repeated stimulation of a rested muscle?

Treppe.

Which muscle-fiber type predominates in long-distance runners?

Slow oxidative (SO) fibers.

Bodybuilders’ muscles contain a higher proportion of which fiber type?

Fast glycolytic (FG) fibers.

Define muscle hypertrophy.

An increase in muscle mass due to enlargement of existing fibers, often from resistance training.

What is muscle atrophy?

A reduction in muscle mass from disuse or loss of neural stimulation.

Where is cardiac muscle tissue found?

Only in the heart.

Name the specialized junctions that connect cardiac muscle cells.

Intercalated discs containing gap junctions and desmosomes.

Smooth muscle is commonly located in which body systems?

Digestive, respiratory, reproductive tracts, and the iris of the eye.

In smooth muscle, autonomic neurons form motor units through axon-like swellings called .

Varicosities (or boutons).