anatomy exam 2 chapter 7

Each myofibril consists of approximately ________ sarcomeres.

10,000

Myofibrils are made primarily of

actin and myosin

The striated appearance of skeletal muscle results from

actin and myosin arrangement.

A resting muscle generates most of its ATP by

aerobic respiration

The stiffness that occurs at death, when actin and myosin molecules stay linked to each other in a contracted state, is due to a lack of

ATP

Which of the following is one of the steps that ends a contraction?

Acetylcholine is broken down by acetylcholinesterase

The ________ contains vesicles filled with acetylcholine.

axon terminal

The enzyme acetylcholinesterase causes acetylcholine to

break down.

Which statement regarding "heat loss" is true?

Muscle contractions play an important role in the maintenance of normal body temperature.

Which statement regarding isometric contractions is true?

The tension produced never exceeds the load

Upon the nerve impulse arriving at the axon terminal

acetylcholine is released

Muscle cells

can only contract

During which phase is the stimulus frequency so high that the relaxation phase is eliminated?

complete tetanus

Exhaustion of energy reserves or decline in pH due to production and dissociation of lactic acid causes

muscle fatigue

Which of the following occurs as a result of motor units in a particular muscle being always active, even though their contractions do not produce enough movement to cause contraction?

muscle tone

The additional oxygen required during the recovery period to restore the normal pre-exertion levels is called the

oxygen debt.

Tropomyosin strands are held in position by which of the following?

troponin molecules

A single stimulus-contraction-relaxation sequence in a muscle fiber is known as a(n)

twitch

The active sites on actin molecules are usually covered up by other molecules. What is the critical material required to uncover the active sites on the actin molecules that will then bind to myosin heads?

calcium

The specialized sarcolemma that contains acetylcholine receptors is the

motor end plate.

In response to action potentials arriving from the transverse tubules, the sarcoplasmic reticulum releases

calcium ions

Neurotransmitters that cause skeletal muscle contraction are normally stored in

motor neuron axon terminals.

After death, rigor mortis lasts until

myofilaments are broken down

Place these steps of muscle contraction in the correct order. 1. Action potential is generated along the sarcolemma 2. Nerve impulse arrives at synapse 3. Calcium is released into muscle cell cytoplasm 4. Acetylcholine is produced 5. Actin and myosin molecules continuously cross-link, with actin molecules being pulled inward

2, 4, 1, 3, 5

The region of a sarcomere containing myosin, going from one end of the myosin molecules to the other end of the myosin molecules, is the

A band

Choose the correct statement regarding motor units

A motor neuron may control only two or three muscle fibers of the eye muscle(s)

During moderate activity, which of the following is true regarding muscle metabolism?

Glucose and fatty acids are catabolized.

The area of the sarcomere that is the light region between two successive A-bands is the

I band

Which of the following occurs when glycolysis produces pyruvate faster than it can be used by the mitochondria?

Lactic acid is produced

Why do individual muscle twitches have to be added together, as in summation or tetanus?

Multiple twitches add up to an increase in muscle fiber tension, which increases the strength of the muscle.

Which statement regarding the relaxation phase of a muscle twitch is true?

Muscle tension falls to resting levels

Which of the following statements describes how muscles help maintain homeostasis?

Skeletal muscle contractions help maintain body temperature.

Which statement regarding skeletal muscle is true?

Skeletal muscles contain blood vessels.

A layer of collagen fibers that surrounds an entire muscle is called?

epimysium.

A muscle ________ contains a sarcolemma, sarcoplasm, myofilaments, and myofibrils.

fiber

Regarding muscle fiber elongation

gravity may help lengthen a muscle fiber after elongation

Skeletal muscle fibers differ from "typical cells" in that these muscle fibers

have many nuclei.

Which of the following occurs when tension production rises to a peak and very brief periods of relaxation occur?

incomplete tetanus

Glycolysis

is an anaerobic process

Calcium ions are released from the sarcoplasmic reticulum during the ________ phase of contraction.

latent

Regarding lactic acid regulation, which cells in the body consume extra oxygen and produce ATP for the conversion of excess lactate absorbed from the blood back to glucose?

liver cells

A sheath of connective tissue surrounding a bundle of striated muscle fibers is called?

perimysium

Muscle fascicles are separated by

perimysium.

Botulism

results from a bacterial toxin that prevents the release of acetylcholine at the axon terminals

The area between Z lines is the

sarcomere.

The terminal cisternae are structural features of the

sarcoplasmic reticula.

The skeletal muscles store calcium ions in the terminal cisternae of the

sarcoplasmic reticulum

As a skeletal muscle contraction is initiated, acetylcholine binding alters the motor end plate membrane's permeability to

sodium ions

Creatine phosphate serves to

supply energy to synthesize ATP

Acetylcholinesterase is found within the

synaptic cleft.

Regarding a skeletal muscle fiber, wherever a T-tubule encircles a myofibril, the tubule is tightly bound to

the sarcoplasmic reticulum.

What is the function of the transverse tubule?

to transmit electrical impulses to the cell's interior