Ch. 9 Anatomy

Immediately following the arrival of the stimulus at a skeletal muscle cell there is a short period called the ________ period during which the events of excitation-contraction coupling occur.

Latent

The response of a motor unit to a single action potential of its motor neuron is called a:

Muscle twitch

Thick myofilaments are made of:

Myosin

Muscle tissue has all of the following properties except ________.

Secretion

Which of the following is correctly paired?

Skeletal muscle: voluntary control

What is the role of tropomyosin in skeletal muscles?

Tropomyosin serves as a contraction inhibitor by blocking the myosin binding sites on the actin molecules.

Which protein inhibits skeletal muscle contraction, and what ion removes the inhibition?

Tropomyosin; calcium ions

What is the functional unit of a skeletal muscle called?

a sarcomere

The term aponeurosis refers to ________.

a sheetlike indirect attachment to a skeletal element

Muscle tone is...

a state of sustained partial contraction

What is the role of calcium ions in muscle contraction?

bind to regulatory sites on troponin to remove contraction inhibition

In an isotonic contraction, the muscle ________.

changes in length and moves the "load"

Which of the following surrounds the individual muscle cell?

endomysium

The connective tissue sheaths of skeletal muscle, in order from internal to external are the:

endomysium, perimysium, and epimysium.

What is the functional role of the T tubules?

enhance cellular communication during muscle contraction

Which muscle characteristic describes the ability of muscle to respond to a stimulus?

excitability

The strongest muscle contractions are normally achieved by ________.

increasing the stimulation up to the maximal stimulus

Which of the following is a factor that affects the velocity and duration of muscle contraction?

load on the fiber

Which of the following is the correct sequence of events for muscle contractions?

motor neuron action potential, neurotransmitter release, muscle cell action potential, release of calcium ions from SR, ATP-driven power stroke, sliding of myofilaments

Hypothetically, if a muscle were stretched to the point where thick and thin filaments no longer overlapped, ________.

no muscle tension could be generated

The muscle cell membrane is called the ________.

sarcolemma

What structure in skeletal muscle cells functions in calcium storage?

sarcoplasmic reticulum

Myoglobin...

stores oxygen in muscle cells

The force of a muscle contraction is not affected by:

the amount of ATP in the muscle cells.

What produces the striations of a skeletal muscle cell?

the arrangement of myofilaments

Which of the following are composed of myosin?

thick filaments

Which type of muscle can contract without being stimulated by the nervous system?

Cardiac

The distance between Z-discs ______ during muscle contraction.

Decreases

After nervous stimulation stops, what prevents ACh in the synaptic cleft from continuing to stimulate contraction?

acetylcholinesterase destroying the ACh

The sliding filament model of contraction involves

actin and myosin sliding past each other and partially overlapping

During muscle contraction, myosin cross bridges attach to which active sites?

actin filaments