Ch 11 - Muscle Tissue and Function

These flashcards cover the major functions, structure, and characteristics of muscle tissue, including skeletal, cardiac, and smooth muscle, as well as muscle contraction and relaxation mechanisms.

What are the major functions of muscle tissue?

Movement, posture & stability, heat production, control of openings, support & protection.

What type of muscle moves bones?

Skeletal muscle.

What type of muscle moves substances like food and urine?

Smooth muscle.

What is the main function of skeletal muscle?

Voluntary movement.

Describe the structure of skeletal muscle.

Long, cylindrical fibers, multinucleated, and striated.

Where is skeletal muscle located in the body?

Attached to bones.

What is the main function of cardiac muscle?

Pumps blood (involuntary).

Describe the structure of cardiac muscle.

Branched cells, 1-2 nuclei, striated, and intercalated discs.

Where is cardiac muscle located?

In the heart.

What is the main function of smooth muscle?

Moves substances (involuntary).

Describe the structure of smooth muscle.

Spindle-shaped, single nucleus, and non-striated.

Where is smooth muscle found in the body?

Walls of organs like the GI tract and blood vessels.

What is the organization of skeletal muscle from cell to whole muscle?

Myofilaments, sarcomere, myofibril, muscle fiber, fascicle, whole muscle.

What connective tissue surrounds individual muscle fibers?

Endomysium.

What connective tissue surrounds fascicles?

Perimysium.

What connective tissue surrounds the entire muscle?

Epimysium.

What connective tissue surrounds groups of muscles?

Fascia.

What is the sarcolemma?

The cell membrane of a muscle fiber.

What do T-tubules do?

Carry action potentials deep into the muscle cell.

What is the function of the sarcoplasmic reticulum (SR)?

Stores Ca²⁺.

What are myofibrils?

Contractile structures within a muscle fiber.

What are thick myofilaments composed of?

Myosin.

What binds to troponin?

Calcium ions (Ca²⁺).

What does tropomyosin do?

Blocks myosin-binding sites.

Define sarcomere.

The functional unit of muscle contraction, between two Z-discs.

What does the A-band in a sarcomere represent?

The dark region that is the length of myosin.

What does the I-band in a sarcomere represent?

The light region consisting of actin only.

What is the H-zone in a sarcomere?

The center of the sarcomere containing myosin only.

What is the Z-disc in a sarcomere?

The boundary of the sarcomere that anchors actin.

What does the M-line do in a sarcomere?

Holds myosin in the middle of the sarcomere.

What is the neuromuscular junction?

The synapse between a motor neuron and a muscle fiber.

What neurotransmitter is released at the neuromuscular junction?

Acetylcholine (ACh).

Describe the sliding filament theory.

Muscle shortens as actin slides past myosin; filaments do not change length.

What initiates contraction at the neuromuscular junction?

A nerve impulse causes ACh release.

What happens during excitation-contraction coupling?

Action potential travels down T-tubules, SR releases Ca²⁺.

What is the first step in the cross-bridge cycle?

Ca²⁺ binds to troponin.

What occurs during the power stroke?

Myosin pulls actin.

What happens after ATP binds during the cross-bridge cycle?

Myosin releases actin.

What is the sequence of events in muscle relaxation?

ACh is broken down, Ca²⁺ pumped back into SR, tropomyosin blocks binding sites.

What are the three sources of ATP for muscle contraction?

Creatine phosphate, glycolysis, oxidative phosphorylation.

Describe creatine phosphate. What is its energy duration?

Fastest source of immediate energy (~10 sec).

What does glycolysis produce, and is it aerobic or anaerobic?

Produces lactic acid, and is anaerobic.

What is oxidative phosphorylation?

Aerobic process in mitochondria, most efficient for ATP production.

What factors contribute to skeletal muscle fatigue?

Depletion of ATP, lactic acid buildup, ion imbalance, reduced oxygen.

What are the characteristics of Type I muscle fibers?

High endurance, lots of mitochondria, uses oxygen.

What defines Type IIa muscle fibers?

Intermediate characteristics, both aerobic and anaerobic.

Describe Type IIb/IIx fiber characteristics.

Quick, powerful, fatigues quickly, low mitochondria.

Define tension in muscle terms.

The force generated by muscle.

Define contraction in muscle terms.

The activation of muscle.

What is a twitch in muscle terms?

A single contraction of a muscle.

What is a motor unit?

One neuron plus all the muscle fibers it controls.

What occurs during the latent period of muscle contraction?

Delay until Ca²⁺ is released.

What happens during the contraction phase of muscle contraction?

Force increases in the muscle.

What occurs during the relaxation phase of muscle contraction?

Ca²⁺ is removed from the cytoplasm.

What is summation in muscle contraction?

Rapid stimuli lead to a stronger contraction.

What does the length-tension relationship indicate?

Maximum tension at optimal sarcomere length.

What happens if a muscle is too stretched?

No overlap of actin and myosin.

What happens if a muscle is too compressed?

Interference in actin-myosin interaction.

What is an isotonic contraction?

Muscle length changes during contraction.

What is an isometric contraction?

Tension is generated without changing muscle length.

What is a concentric contraction?

Muscle shortens while contracting.

What is an eccentric contraction?

Muscle lengthens while contracting.

What is the role of calcium ions in muscle contraction?

They bind to troponin to expose myosin-binding sites.

What is the role of ATP in muscle contractions?

Provides energy for muscle fiber to relax and reset myosin heads.

What is the muscle fiber's resting potential?

The state of the muscle fiber when not contracted.

What is the effect of lactic acid on muscle performance?

It contributes to muscle fatigue and soreness.

How do veins assist smooth muscle?

They contain smooth muscle that regulates blood flow.

What is the consequence of prolonged muscle contraction?

Potential muscle cramps or fatigue.

What initiates the muscle contraction cycle?

Nerve signal triggering ACh release.

What is the significance of intercalated discs in cardiac muscle?

They enable synchronized contraction of the heart muscle.

What happens to the sarcomere during contraction?

It shortens as actin slides toward M-line.

What role do motor neurons play in muscle contraction?

They transmit signals to muscle fibers to initiate contraction.

How does oxygen availability affect muscle fiber types?

Type I uses more oxygen for endurance, while Type IIb is anaerobic.

State one difference between skeletal and smooth muscle.

Skeletal muscle is voluntary; smooth muscle is involuntary.

What are the two types of isotonic contractions?

Concentric and eccentric contractions.

What is muscle hypertrophy?

Increase in muscle fiber size due to training.

What is the definition of atrophy?

Decrease in muscle fiber size when muscles are not used.

What physiological process occurs when muscles experience overload?

Muscle adaptation resulting in strength gains.

What component of skeletal muscle helps with rapid energy production?

Creatine phosphate.

What is the main function of the sarcoplasmic reticulum?

Calcium storage for muscle contraction.

How are action potentials generated in muscle fibers?

By the binding of acetylcholine to receptors.

What does the power stroke result in during muscle contraction?

Shortening of the muscle fiber.

What is the role of myoglobin in muscle?

Storage and transport of oxygen in muscle cells.

What is a neuromuscular transmission?

The process in which a nerve signal triggers muscle contraction.

What structural feature distinguishes cardiac muscle from skeletal muscle?

Presence of intercalated discs.

What is the anatomical significance of Z-discs?

They act as anchoring points for actin filaments in sarcomeres.

What is the primary energy source during intense exercise?

Glycolysis.

What allows for muscle fiber type differentiation?

Genetic predisposition and training adaptations.

What is the functional significance of myofibrils?

They contain the contractile elements of muscle.

What action occurs when myosin and actin bind?

Cross-bridge formation.

Define tetanus in muscle physiology.

Sustained muscle contraction without rest.

How does ACh affect muscle contraction?

It binds to receptors causing depolarization of muscle fibers.