chapter 10: muscle tissue & physiology

What are the general functions of muscle tissue?

Creates movement, maintains posture, stabilizes joints, generates heat, regulates flow of materials through hollow organs.

What are the three types of muscle tissue?

Skeletal, cardiac, and smooth muscle.

Describe the characteristics of skeletal muscle fibers.

Long, thin, striated, multinucleated cells.

What type of muscle is found only in the heart?

Cardiac muscle.

What type of muscle lines hollow organs?

Smooth muscle.

How do skeletal and smooth muscle contractions generate tension?

Both involve interactions between actin and myosin and require calcium ions and ATP.

What is contractility in muscle cells?

The ability to contract, where proteins in the cell draw closer together.

What does excitability refer to in muscle cells?

The ability to respond to a stimulus.

What is the sarcoplasm?

The cytoplasm of a muscle cell.

What is the function of the sarcoplasmic reticulum?

Stores and releases calcium ions.

What is a triad in muscle tissue?

A combination of one T-tubule and two terminal cisternae.

What are myofilaments?

Protein bundles that make up myofibrils.

What are the three types of proteins found in myofilaments?

Contractile proteins, regulatory proteins, and structural proteins.

What is the role of myosin in muscle contraction?

It is a contractile protein that produces tension.

What is the function of actin in muscle fibers?

It is a contractile protein that binds to myosin heads.

What is the role of tropomyosin in muscle contraction?

It covers the active sites on actin at rest.

What is the function of troponin?

It holds tropomyosin in place and helps regulate muscle contraction.

What is a sarcomere?

The functional contractile unit of a myofibril.

What occurs during the sliding-filament mechanism?

Thin filaments slide past thick filaments, generating tension and shortening the sarcomere.

What is resting membrane potential?

The electrical potential difference across the plasma membrane of a resting cell.

What is the role of the sodium-potassium pump?

It pumps 3 sodium ions out of the cell and 2 potassium ions into the cell.

What happens during depolarization?

The membrane potential becomes more positive as sodium ions enter the cell.

What is repolarization?

The return of the membrane potential to its negative resting value after depolarization.

What is the difference between leak channels and gated channels?

Leak channels are always open, while gated channels open in response to specific stimuli.

What is the neuromuscular junction?

The synapse of a motor neuron with a muscle fiber.

What is the function of titin in muscle fibers?

It provides elasticity and resists excessive stretching.

What is the function of nebulin?

It helps determine the length of the thin filament.

What does the A band in a sarcomere contain?

Thick filaments and regions of overlap with thin filaments.

What is the H zone in a sarcomere?

The area that contains only thick filaments.

What is the M line in a sarcomere?

The middle of the sarcomere, holding thick filaments in place.

What is the axon terminal?

The swollen end of a neuron's axon containing synaptic vesicles filled with neurotransmitters.

What neurotransmitter is involved in muscle contraction?

Acetylcholine (ACh)

What is the synaptic cleft?

The narrow space between the axon terminal and muscle fiber where ACh is released.

How is acetylcholine released?

An action potential triggers voltage-gated calcium ion channels to open, leading to exocytosis of synaptic vesicles.

What is the motor end plate?

A specialized region of the sarcolemma containing receptors for acetylcholine.

What is an end-plate potential?

Local depolarization in the area of the motor end plate due to the influx of sodium ions.

What role does acetylcholinesterase (AChE) play?

It degrades and inactivates ACh in the synaptic cleft almost immediately after its release.

What is excitation-contraction coupling?

The process that transmits excitation from the sarcolemma to the myofilaments using calcium ions.

What happens during the contraction phase of muscle contraction?

The sliding-filament mechanism occurs, leading to sarcomere contraction.

What initiates the crossbridge cycling in muscle contraction?

Calcium ions bind to troponin, causing tropomyosin to move and expose active sites on actin.

What is the power stroke in muscle contraction?

The phase where myosin pulls actin toward the center of the sarcomere.

What is muscle relaxation?

The process where ACh release stops, calcium ions are pumped back into the sarcoplasmic reticulum, and muscle fibers return to resting state.

What is a motor unit?

A single motor neuron along with the muscle fibers it innervates.

What is muscle tone?

The small amount of tension a muscle has despite being relaxed, due to involuntary activation of motor units.

What is wave summation?

The effect where repeated stimulation of a muscle fiber results in twitches with progressively greater tension.

What is the difference between isometric and isotonic contractions?

Isometric contractions do not change muscle length, while isotonic contractions involve muscle shortening or lengthening.

What is atrophy?

The decrease in muscle fiber diameter due to loss of myofibrils.

What is hypertrophy?

The increase in the number of myofibrils and diameter of muscle fibers.

What is the creatine phosphate reaction?

A process that regenerates ATP almost immediately for muscle activity using creatine kinase.

What is muscle fatigue?

The inability to maintain a given level of intensity of a particular exercise due to various factors.

What are the types of muscle fibers?

Type I - Slow Oxidative, Type IIa - Fast Oxidative Glycolytic, Type IIx - Fast Glycolytic.

What characterizes Type I muscle fibers?

They contract slowly, maintain extended periods of contraction, and have high myoglobin content.

What is excess postexercise oxygen consumption (EPOC)?

The increased rate of ventilation after exercise to correct homeostasis disturbances.

What is the refractory period in muscle fibers?

A time interval of about 5 milliseconds when a muscle fiber cannot respond to another stimulus.

What triggers the release of calcium ions from the sarcoplasmic reticulum?

Depolarization of T-tubules during excitation-contraction coupling.

What happens during fused (complete) tetanus?

The muscle fiber cannot relax between stimuli, producing a sustained contraction.