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