Muscle Tissue and Physiology – Chapter 10 Review

Question-and-answer flashcards covering major concepts from Chapter 10 on muscle tissue: types, properties, cellular structure, contraction mechanics, energy sources, and tension principles.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle tissues.

What is the basic function common to all muscle tissues?

Generating a force called muscle tension.

List four additional functions of muscle tissue besides producing tension.

Create movement, maintain posture, stabilize joints, generate heat, and regulate flow through hollow organs (any four).

Which muscle tissue type is multinucleated and voluntary?

Skeletal muscle tissue.

Where is cardiac muscle found and is its contraction voluntary or involuntary?

Found only in the heart; contraction is involuntary.

What specialized junctions connect cardiac muscle cells?

Intercalated discs containing gap junctions and desmosomes.

Do smooth muscle cells have striations?

No, smooth muscle cells lack striations.

Describe the shape and nucleus number of a smooth muscle cell.

Long, spindle-shaped with a single centrally located nucleus.

Define contractility in muscle cells.

Ability to contract by proteins drawing closer; does not always involve shortening.

Define excitability in muscle cells.

Ability to respond to a stimulus (chemical, stretch, or electrical).

Define conductivity in muscle cells.

Ability to conduct electrical changes across the entire plasma membrane.

Define extensibility in muscle cells.

Ability to be stretched up to three times resting length without damage.

Define elasticity in muscle cells.

Ability to return to original length after stretching.

What is the sarcolemma?

The plasma membrane of a muscle cell.

What is the sarcoplasm?

The cytoplasm of a muscle cell.

What organelle stores and releases Ca²⁺ in muscle fibers?

Sarcoplasmic reticulum (SR).

What are myofibrils?

Cylindrical organelles composed of contractile proteins; constitute 50–80 % of cell volume.

Name the connective tissue layer surrounding individual muscle fibers.

Endomysium.

Bundles of muscle fibers form a __, surrounded by __.

Fascicle; perimysium.

Entire skeletal muscle is wrapped by what connective tissue layer?

Epimysium.

What structure anchors groups of muscles together?

Fascia.

What are transverse tubules (T-tubules)?

Deep invaginations of sarcolemma that encircle myofibrils and conduct action potentials.

A triad consists of __.

Two terminal cisternae of SR plus one T-tubule.

What protein makes up thick filaments?

Myosin.

List the three proteins of the thin filament.

Actin, tropomyosin, and troponin.

Which band contains only thin filaments?

I band.

Which line anchors thin filaments and marks sarcomere boundaries?

Z disc.

Which band remains unchanged during contraction?

A band.

What happens to the I band and H zone during contraction?

Both narrow (shorten).

Do filaments themselves shorten during sliding-filament contraction?

No, thin filaments slide toward the M line; filament length stays constant.

Define neuromuscular junction (NMJ).

Synapse where a motor neuron communicates with a skeletal muscle fiber.

Name the neurotransmitter released at the NMJ.

Acetylcholine (ACh).

What ion enters the muscle fiber when ACh binds its ligand-gated channel?

Na⁺ (sodium).

List the three phases of skeletal muscle contraction.

Excitation, excitation-contraction coupling, and contraction (cross-bridge cycle).

During excitation-contraction coupling, what triggers Ca²⁺ release from SR?

Propagation of an action potential to terminal cisternae opens voltage-gated Ca²⁺ channels.

Which ion binds to troponin to initiate contraction?

Ca²⁺ (calcium).

In the cross-bridge cycle, what causes the power stroke?

Release of ADP and Pi from the myosin head.

What breaks the link between myosin and actin?

Binding of a new ATP to the myosin head.

During relaxation, which enzyme degrades ACh in the synaptic cleft?

Acetylcholinesterase.

Why does rigor mortis occur?

Lack of ATP post-death prevents myosin detachment; Ca²⁺ remains in cytosol, causing sustained contraction.

List three processes that require ATP in skeletal muscle.

Na⁺/K⁺ pump operation, recocking myosin heads, pumping Ca²⁺ back into SR.

What immediate energy molecule donates a phosphate to ADP in muscles?

Creatine phosphate (CP).

How long can CP provide maximal muscle activity?

About 10 seconds.

What enzyme catalyzes transfer of phosphate from CP to ADP?

Creatine phosphokinase (CPK).

Glycolysis occurs in the and supplies ATP for about seconds.

Cytosol; 30–40.

If oxygen is plentiful, pyruvate enters __; if not, it is converted to __.

Mitochondria for oxidative catabolism; lactic acid.

Oxidative (aerobic) catabolism predominates after about minute of activity.

One minute (and supplies nearly 100 % after several minutes).

What oxygen-binding protein stores O₂ inside muscle fibers?

Myoglobin.

Define a muscle twitch.

Smallest measurable contraction produced by a muscle fiber in a lab setting.

Name the three phases of a twitch myogram.

Latent period, contraction period, relaxation period.

What is wave summation?

Increase in tension due to repeated stimulation before complete relaxation.

Differentiate unfused and fused tetanus.

Unfused tetanus shows partial relaxation and ~80 % max tension; fused tetanus shows no relaxation and nearly 100 % max tension.

Why can skeletal muscle achieve fused tetanus?

Its refractory period is extremely short (~5 ms).

What sarcomere length (percent of natural) produces maximal tension?

Approximately 100–120 % of natural length.

Define motor unit.

A single motor neuron and all the muscle fibers it innervates.

Why do fingers have small motor units?

They require fine motor control (as few as 10 fibers per unit).

Why do postural back muscles have large motor units?

They require less precision but greater power (2000–3000 fibers per unit).