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36 Cards in this Set
- Front
- Back
Which of the following is CORRECTLY paired? |
C. skeletal muscle: voluntary control |
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What causes the release of calcium from the terminal cisternae of the sarcoplasmic reticulum within a muscle cell? |
B. arrival of an action potential |
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The binding of calcium to which molecule causes the myosin binding sites to be exposed? |
troponin |
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A myosin head binds to which molecule to form a cross bridge? |
A. actin |
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What causes the myosin head to disconnect from actin? |
D. binding of ATP |
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What energizes the power stroke? |
C. hydrolysis of ATP |
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In a neuromuscular junction, synaptic vesicles in the motor neuron contain which neurotransmitter? |
D. acetylcholine (ACh) |
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When an action potential arrives at the axon terminal of a motor neuron, which ion channels open? |
A. voltage-gated calcium channels |
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What means of membrane transport is used to release the neurotransmitter into the synaptic cleft? |
A. exocytosis |
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The binding of the neurotransmitter to receptors on the motor end plate causes which of the following to occur? |
C. Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate. |
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How is acetylcholine (ACh) removed from the synaptic cleft? |
C. acetylcholinesterase (AChE; an enzyme) |
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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? |
A. terminal cisternae of the sarcoplasmic reticulum |
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Excitation-contraction coupling is a series of events that occur after the events of the neuromuscular junction have transpired. The term excitation refers to which step in the process? |
D. Excitation refers to the propagation of action potentials along the axon of a motor neuron. |
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Excitation of the sarcolemma is coupled or linked to the contraction of a skeletal muscle fiber. What specific event initiates the contraction? |
B. Calcium release from the sarcoplasmic reticulum initiates the contraction. |
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A triad is composed of a T-tubule and two adjacent terminal cisternae of the sarcoplasmic reticulum. How are these components connected? |
D. A series of proteins that control calcium release. |
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What is name given to the regularly spaced infoldings of the sarcolemma? |
B. transverse or T tubules |
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Which of the following is most directly responsible for the coupling of excitation to contraction of skeletal muscle fibers? |
A. Calcium ions. |
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What is the relationship between the number of motor neurons recruited and the number of skeletal muscle fibers innervated? |
A. Typically, hundreds of skeletal muscle fibers are innervated by a single motor neuron. |
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Excitation-contraction coupling includes all EXCEPT which of the following events? |
C. release of acetylcholine from axon terminals at the neuromuscular junction |
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What is a cross bridge cycle? |
D. It is the cycle in which an energized myosin head binds to actin and performs a power stroke, then binds to ATP in order to detach and re-energize. |
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Muscle tissue does NOT ________. |
C. produce blood cells |
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Which type of muscle CANNOT contract without being stimulated by the nervous system? |
A. skeletal |
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Which muscle characteristic describes the ability of muscle to respond to a stimulus? |
A. excitability |
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Action potential propagation in a skeletal muscle fiber ceases when acetylcholine is removed from the synaptic cleft. Which of the following mechanisms ensures a rapid and efficient removal of acetylcholine? |
D. Acetylcholine is degraded by acetylcholinesterase. |
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The neuromuscular junction is a well-studied example of a chemical synapse. Which of the following statements describes a critical event that occurs at the neuromuscular junction? |
A. Acetylcholine is released by axon terminals of the motor neuron. |
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Action potentials travel the length of the axons of motor neurons to the axon terminals. These motor neurons __________. |
B. extend from the brain or spinal cord to the sarcolemma of a skeletal muscle fiber |
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Calcium entry into the axon terminal triggers which of the following events? |
C. Synaptic vesicles fuse to the plasma membrane of the axon terminal and release acetylcholine. |
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Acetylcholine binds to its receptor in the sarcolemma and triggers __________. |
C. the opening of ligand-gated cation channels |
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Sodium and potassium ions do not diffuse in equal numbers through ligand-gated cation channels. Why? |
A. The inside surface of the sarcolemma is negatively charged compared to the outside surface. Sodium ions diffuse inward along favorable chemical and electrical gradients. |
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The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? |
D. A myosin head bound to actin |
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What structure is the functional unit of contraction in a skeletal muscle fiber? |
B. The sarcomere |
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Calcium ions couple excitation of a skeletal muscle fiber to contraction of the fiber. Where are calcium ions stored within the fiber? |
C. Calcium ions are stored in the sarcoplasmic reticulum. |
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After a power stroke, the myosin head must detach from actin before another power stroke can occur. What causes cross bridge detachment? |
D. ATP binds to the myosin head. |
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How does the myosin head obtain the energy required for activation? |
B. The energy comes from the hydrolysis of ATP. |
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What specific event triggers the uncovering of the myosin binding site on actin? |
C. Calcium ions bind to troponin and change its shape. |
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When does cross bridge cycling end? |
C. Cross bridge cycling ends when sufficient calcium has been actively transported back into the sarcoplasmic reticulum to allow calcium to unbind from troponin. |