Unit 2 - A & P Module - The Somatic Nervous System

Question 1

Compare and contrast the voltage-gated sodium and potassium channels. What type of change in the cell is produced by ion movement through each type of channel?

Answer 1

1. The voltage-gated sodium channel opens in response to threshold voltage and allows sodium to enter the cell, thereby depolarizing the membrane potential.
2. The potassium channel is also opened by threshold voltage and allows potassium to exit the cell, repolarizing or hyperpolarizing the membrane potential.

Question 1

The motor end plate is __________.

Answer 1

a folded area of muscle cell membrane with nicotinic cholinergic receptor clusters at the top of each fold

Question 2

The disease myasthenia gravis is caused by __________.

Answer 2

destruction of acetylcholine receptors

Question 3

What is the effector tissue of the somatic motor division?

Answer 3

Skeletal muscle

Question 4

A motor unit consists of __________.

Answer 4

a motor neuron and all of the myofibers innervated by it

Question 5

Curare produces skeletal muscle paralysis because it is a __________.

Answer 5

nicotinic cholinergic antagonist

Question 6

In contrast to autonomic synapses, the synapses between neurons and skeletal muscle (neuromuscular junctions) __________.

Answer 6

1. Are always excitatory
2. Almost always produce muscle contractions when the synapse is active
3. Produce end-plate potentials that almost always bring the postsynaptic muscle cell to threshold

Question 7

A toxin that inhibits acetylcholinesterase at the neuromuscular junction would cause __________.

Answer 7

muscle spasms and respiratory failure

Question 8

If a somatic motor neuron fires an action potential, the response is always __________.

Answer 8

excitatory

Question 9

Somatic motor neurons in the spinal cord control all of the following muscles, except those that __________.

Answer 9

move the face

Question 10

The somatic nervous system differs from the parasympathetic nervous system in that it is __________.

Answer 10

mostly under voluntary control and the efferent pathway consists of only a single motor neuron

Question 11

End-plate potentials at the neuromuscular junction are similar to excitatory postsynaptic potentials in what way?

Answer 11

They are both depolarizing.

Question 12

A toxin that prevents the release of acetylcholine at the neuromuscular junction would cause __________.

Answer 12

flaccid paralysis of skeletal muscles

Question 13

If a person has a genetic disorder that caused him to produce none of the neurotransmitter norepinephrine, which type of tissue would be affected the least?

Answer 13

Skeletal muscle