Muscular System Review

What chemical helps to regenerate ATP?

Creatine phosphate

What is the function of skeletal muscles?

To move bones

What are muscle fibers made of?

Individual fibers called myofibrils

What is the connective tissue that surrounds fascicles?

Perimysium

What happens when poisons like botulism prevent the release of acetylcholine?

Muscles stay relaxed

What are the three types of muscles?

Skeletal, cardiac, and smooth muscles

What neurotransmitter is associated with muscles?

Acetylcholine

What cell organelle provides ATP for muscle activity?

Mitochondria

What is the gap between the nerve and the muscle called?

Synaptic cleft

What is hypertrophy?

Increase in muscle size

What is atrophy?

Decrease in muscle size

What symptoms would a person with a disease inhibiting cholinesterase production have?

Muscle that stays contracted

What is the function of cholinesterase?

To break down acetylcholine

During muscle contraction, cross-bridges form between which two structures?

Actin and myosin

What are the I band and A band made of in a sarcomere?

I band: Actin, A band: Myosin

What gives muscle cells a striated appearance?

The arrangement of dark and light fibers

What is the energy source for muscle contraction?

ATP

What substance is stored in vesicles in the motor neuron?

Acetylcholine

What happens to the number of motor units being activated during recruitment?

Increases

What is the sustained contraction of individual fibers, even when the muscle is at rest, called?

Muscle tone

What is the immovable end of a muscle called?

Origin

What is the movable end of a muscle called?

Insertion

What is muscle fatigue likely due to?

Buildup of lactic acid

What is a sarcomere?

The region between two Z-lines

What is the condition called when a body becomes stiff after death?

Rigor mortis

What does ATP become when it has been used?

ADP and phosphate

What is a motor unit?

Motor neuron and muscle fiber cell

What are myofibrils composed of?

Actin and myosin (myofilaments)

What is the specialized part of the muscle fiber membrane at the neuromuscular junction called?

Motor end plate

What type of connective tissue surrounds fascicles (bundles)?

Perimysium

What type of tissue surrounds the entire muscle?

Epimysium

What is the substance that crosses the gap between a neuron and a muscle fiber called?

Neurotransmitter

What do tendons connect?

Muscles to bones

What are bundles of muscle fibers called?

Fascicles

What is the minimum amount of stimulus required for a muscle contraction to occur called?

Threshold stimulus

What model explains how muscles contract?

Sliding filament theory

Place the following in the correct order: 1. Acetylcholine crosses the gap at the neuromuscular junction, 2. Calcium is released into the sarcoplasm, 3. Actin and myosin form links, 4. Myosin cross-bridges pull actin filaments inward.

1-4-2-3

What are the A bands and I bands in muscle fibers?

A bands are dark, I bands are light

What is the muscle fiber membrane called?

Sarcolemma

What is the transport network of the muscle called?

Sarcoplasmic Reticulum

What factor determines how forcefully a muscle contracts?

Number of cells stimulated

Describe muscle fatigue and its cause.

Caused by oxygen debt during prolonged muscle activity, muscle becomes unable to contract even when stimulated, depends on blood supply

Fill in the blanks in these sentences about the action potential and muscle cell contraction.

An action potential is an electrical current generated by the change in charge across the muscle cell membrane or sarcolemma. The result of this electrical impulse traveling from one end of the cell to the other is contraction of the muscle cell.

What is the function of acetylcholinesterase?

To break down ACh and prevent continued muscle contraction.

What is the role of the sodium-potassium pump?

To help the cell return to its resting state.

How do myofibrils attach to thin filaments?

By binding to binding sites on the thin filaments.

What provides energy for crossbridge attachment and detachment?

ATP.

What happens simultaneously in sarcomeres during muscle contraction?

The entire muscle cell shortens.

What is the role of calcium in the attachment of myosin crossbridges to actin?

It is required for the attachment.

What happens to calcium ions when the action potential ends?

They are reabsorbed into the sarcoplasmic reticulum.

What is the sarcolemma?

The plasma membrane of a muscle cell.

What is the function of the sarcoplasmic reticulum?

To transmit electrical impulses and store calcium ions.

What are myofibrils?

Long, filamentous organelles within muscle cells.

What are myofilaments?

Filaments of myofibrils made of proteins, primarily myosin or actin.

What are sarcomeres?

Contracting subunits of skeletal muscle.

What is myosin?

A fibrous protein that forms contractile filaments in muscle cells.

What is actin?

A protein that forms contractile filaments in muscle cells.