Ch. 7 Muscles A&P
release(s) calcium ions into the sarcoplasm
terminal cistern
When an action potential arrives at the axon terminal of a motor neuron, which ion channels open?
voltage-gated calcium channels
In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter?
acetylcholine (ACh)
A myosin head binds to whihc molecule to form a cross bridge?
actin
The striated appearance of skeletal muscle results from
actin and myosin arrangement
Most of the ATP needed by muscle cells is provided through
aerobic metabolism
What causes the release of calcium ions into the sarcoplasm from the terminal cisterns?
an action potential traveling along the t tubule
Muscles whose actions oppose one another are referred to as
antagonists
What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum wihtin a muscle cell?
arrival of an action potential
Which of the following is NOT a function of skeletal muscles?
contraction of the heart
What means of membrane transport is used to release the neurotransmitter into the synaptic cleft?
exocytosis
receive(s) stimulus from the motor neuron
junctional folds
Number of cross-bridges decline and tension is reduced during which phase?
relaxation phase
What causes the power stroke?
release of ADP and Pi
The binding of calcium to which molecule causes the myosin binding sites to be exposed?
troponin
change(s) shape upon binding with calcium ions
troponin
Nonstriated, involuntary muscle is
smooth
block(s) binding sites on actin
tropomyosin
Which order do they occur? 1. Muscle relaxation occurs. 2. ACh molecules are released into the synaptic cleft. 3. Na+ enters the sarcoplasm, producing an action potential. 4. Muscle contraction occurs. 5. The sarcoplasmic reticulum actively pumps back calcium. 6. ACh binds to receptors on the sarcolemma. 7. Calcium ions are released from the sarcoplasmic reticulum. 8. Calcium ions bind to troponin.
2, 6, 3, 7, 8, 4, 5, 1
Rigor mortis occurs due to the lack of what molecule?
ATP
The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur?
Binding of the nuerotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell
Which of the following is ranked from smallest to largest?
H-band, sacromere, myofibril, muscle fiber, fascicle, muscle
Which of the following effects would EGTA have on excitation-contraction coupling after the neuron releases acetylcholine at the neuromuscular junction?
It would prevent myosin from forming cross bridges with actin.
Botulism is caused by a bacterial toxin that prevents the release of ACh at the axon terminals. What happens as a result?
Muscles are not capable of contracting.
conduct(s) action potentials throughout the interior of the muscle fiber
T tubule
Which of the following does NOT occur in the sacromere during muscle contraction?
The Z-lines move further apart
What causes the myosin head to disconnect from actin?
binding of ATP
Conduction of an action potential along the sarcolemma depends upon
diffusion of sodium ions through voltage-gated channels
The term used to describe muscular growth in response to usage is
hypertrophy
What structures are found in the cardiac muscles?
intercalated disc
Unlike skeletal tissue, cardiac muscle tissue
is involuntary, and contains branched cells and intercalated discs
Unlike skeletal muscle tissue, smooth muscle tissue
is involuntary, lacks sarcomeres, and is not striated
As you unsuccessfully attempt to lift the 300-pound weights off the ground, you are demonstrating
isometric contraction
How is acetylcholine (ACh) removed from the synaptic cleft?
simple diffusion away from the synaptic cleft and acetylcholinesterae (AChE; an enzyme)
The action potential on the muscle cell leads to contraction due to the release of calcium ions. Where are calcium ions stored in the muscle cell?
terminal cesterns (cisternae) of the sarcoplasmic reticulum
