A&P chapter 7 7e

Each myofibril consists of approximately ________ sarcomeres

10.000

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

Myofibrils are made primarily of

actin and myosin

The striated appearance of skeletal muscle results from

actin and myosin arrangement

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

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

calcium ions

Upon the nerve impulse arriving at the axon terminal

acetylcholine is released

The specialized sarcolemma that contains acetylcholine receptors is the

motor end plate

Neurotransmitters that cause skeletal muscle contraction are normally stored in

motor neuron axon terminals

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

muscle tension falls to resting levels

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

After death, rigor mortis lasts until

myofilaments are broken down

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

troponin molecules

a single stimulus- contraction relaxation sequence the muscle fiber is known as

twitch

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

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

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

I band

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

epimysium

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

fiber

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

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

latent

a sheath of connective tissue surrounding a bundle of 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

Which of the following describes how muscles help maintain homeostasis?

skeletal muscle contractions help maintain body temp

which statement regarding skeletal system is true?

skeletal muscles contain blood vessels

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

sodium ions

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 cells interior