Motor neuron 1. 4 Muscle fiber nucleus Myofibril of muscle fiber Figure 10.15. Details of the neuromuscular junction. O bluedoor, LLC The numbers 1-4 indicate the chain of events that occur at the neuromuscular junction. Put these events in chronological order by placing a 1 in the blank before the first event, etc. Refer back to Figure 10.15 for information. Acetylcholine diffuses across the synaptic cleft. Nerve impulse reaches the axon terminal. Synaptic vesicles release acetylcholine into the synaptic cleft. Acetylcholine binds to receptors at the motor end plate. Answer the following questions. 1. Which event listed above is the point at which myasthenia gravis interrupts the process? Explain why. 2. One treatment for myasthenia gravis is a medication that blocks the activity of acetylcholinesterase. Suggest why this might be a successful treatment.

Put these events that occur in skeletal muscle in the correct chronological sequence: 1. Opening of mechanically-gated ryanodine receptors (RyR) on the sarcoplasmic reticulum 2. Ca²+ binding to troponin to initiate contraction 3. Activation of voltage-gated dihydropyridine (DHP) receptor in the T-tubule 4. Na+ influx through ligand-gated ion channels on the motor end plate 4, 3, 2, 1 2, 1, 4, 3 3, 1, 2, 4 4, 3, 1, 2 3, 1, 4, 2

In a skeletal muscle if calcium levels in the cytosol increase, as calcium is released from the sarcoplasmic reticulum (SR,) how would this affect the position of the actin and myosin filaments?  Group of answer choices Calcium released from the SR binds to calmodulin. Calmodulin activates myosin light chain kinase, causing cross bridge formation. Calcium released from the SR binds to troponin, moving tropomyosin and allowing for cross bridge formation. Calcium released from the SR binds to troponin, moving tropomyosin and inhibiting cross bridge formation. Calcium released from the SR binds to troponin, causing actin to detach from myosin. pick one answer

Interruption of spindle discharge from a muscle causes contraction of the muscle to become jerky and irregular due to :-a- increased activity of reverberating circuits causing fluctuation of the motor discharge to the muscleb- increased activity of inhibitory interneurons causing oscillating inhibition of the α-motor neurons of the musclec- irregular discharge of excitatory inputs to the α-motor neurons of the muscle d- post-tetanic potentiation of the α-motor neurons of the muscle

When an action potential arrives at the neuromuscular junction, acetylcholine is released into the synaptic cleft and binds to receptors in the postsynaptic membrane. Which of the following represents the correct order of the next series of events?   A. An action potential travels down the T tubules, depolarization spreads through the T tubules, Ca2+ is released from the sarcoplasmic reticulum, and myosin binds to actin.   B. Ca2+ is released from the sarcoplasmic reticulum, an action potential travels down the T tubules, depolarization spreads through the T tubules, and myosin binds to actin.   C. An action potential travels down the T tubules, depolarization spreads through the T tubules, Ca2+ is taken up by the sarcoplasmic reticulum, and myosin binds to actin.   D. T tubules are depolarized, Ca2+ is released from the sarcoplasmic reticulum, an action potential is created in the muscle cell, and myosin bonds to actin.   E. An action potential travels…

Jane is wishing to artificially stimulate neurotransmitter release by a motor neuron. She should be able to do this by electrically activating the neuron (TRUE or FALSE) and/or by injecting potassium ions into the synaptic terminal/knob region (TRUE or FALSE).

Caffeine is known to alter transmembrane movement of calcium. What are two possible sites in the nerve and/or muscle that caffeine can act upon?

Order the following events that occur during a nerve impulse.     a few milliseconds behind the Na channels, K channels open and allow K into the cell (-70 mV)   Na voltage-gated channel opens and Na leaves the cell (-55 mV)   some stimulus is detected (-70 mV)   more Na outside the cell causes other nearby Na channels to open (+35 mV)   the cell rebalances the Na and K ions in preparation for the next impulse (~3-4ms)

Researchers are working to understand a rare disease that affects the ability of the muscles to contract. They have identified that the disease is caused by abnormal gene expression leading to a relatively large intracellular space between the T-tubules and the terminal cisternae in the triad, which causes an interruption in the connection between the dihydropyridine (DHP) receptor and the ryanodine calcium channel. Based on this description of the morphology underlying the disease, which of the following problems would you expect in excitation-contraction coupling? An action potential would not be able to be transmitted down the T-tubule. Re-uptake of calcium would be blocked, leading to an increase in intracellular calcium. O The actin binding sites may continue to be blocked by tropomyosin even following an action potential along the sarcolemma. O All of the above. Only B and C.

Select all that are true of motor pathways. They are composed of at least two neurons. Somas of upper motor neurons are housed within the spinal cord. Lower motor neurons can be excitatory or inhibitory. Axons of lower motor neurons innervate skeletal muscle cells. ©2017 McGr