Mastering A&P: Muscular System HW#2
True or False: Depolarization of a skeletal muscle cell leads to the opening of more channels that only allow potassium entry.
False
True or False: The neurotransmitter used by the nervous system to activate skeletal muscle cells is acetylcholine.
True
True or False: The sarcoplasmic reticulum wraps like a sleeve around the myofibril and stores and releases calcium.
True
What changes occur in the sarcomere during muscle contraction? A. A band decreases in length. B. The thin filament shortens. C. I band increases in length. D. Z discs move closer together.
Z discs move closer together
What is acetylcholine?
a neurotransmitter that stimulates skeletal muscle to contract
The mechanical force of contraction is generated by ________.
a sliding of thin filaments past thick filaments
Specific neurotransmitter that stimulates skeletal muscle cells
acetylcholine
What is released by axon terminals into the synaptic cleft to stimulate a muscle to contract?
acetylcholine
What mineral is released within muscle cells to trigger contraction?
calcium
The sarcoplasmic reticulum stores this chemical
calcium ions
What must rush into a muscle cell to promote its depolarization?
sodium ions
Gap between the axon terminals and the plasma membrane of a neighboring muscle cell
synaptic cleft
A sarcomere is ________.
the contractile unit between two Z discs
Why are calcium ions necessary for skeletal muscle contraction?
Calcium ions trigger the binding of myosin heads to actin filaments.
According to the sliding filament theory, how does muscle contraction occur?
Myosin heads form cross bridges and pull thin filaments, causing them to slide.
Which neurotransmitter is released by motor neurons at the neuromuscular junction?
acetylcholine
What initiates an action potential on a muscle cell?
acetylcholine binding to receptors on the sarcolemma within the neuromuscular junction
Enzyme that breaks down acetylcholine (ACh)
acetylcholinesterase
What enzyme breaks down acetylcholine into acetic acid and choline to prevent continued contraction of the muscle fiber?
acetylcholinesterase
During skeletal muscle contraction, to what do myosin heads bind?
actin filaments
Electrical current that travels the length of the sarcolemma that results in the contraction of the muscle fiber
action potential
What is the unstoppable electrical current that travels down the length of the entire surface of a sarcolemma?
action potential
Neurotransmitters are released upon stimulation from a nerve impulse from the ________.
axon terminals of the motor neuron
What term refers to a smooth, sustained contraction?
complete tetanus
Muscle tissue has the ability to shorten when adequately stimulated, a characteristic known as ________.
contractility
The plasma membrane of a skeletal muscle cell is called the ________.
sarcolemma
What organelle wraps and surrounds the myofibril and stores calcium?
sarcoplasmic reticulum
Chemical that enters a muscle cell upon excitation
sodium ions
The gap between the axon terminal of a motor neuron and the sarcolemma of a skeletal muscle cell is called the ________.
synaptic cleft
Which one of the following is composed mostly of the protein myosin?
thick filaments
Contractions in which muscles shorten and produce movement are known as ________.
isotonic contractions
A motor neuron and all of the skeletal muscle fibers it stimulates are termed a ________.
motor unit
