Chapter 16 Review Questions

The white ramus communicans contains a. preganglionic sympathetic fibers. b. postganglionic sympathetic fibers. c. preganglionic parasympathetic fibers. d. postganglionic parasympathetic fibers.

A

Which of the following statements concerning the preganglionic neurons of the ANS is true? a. All parasympathetic preganglionic neurons secrete acetylcholine. b. Only parasympathetic preganglionic neurons secrete acetylcholine. c. All sympathetic preganglionic neurons secrete norepinephrine. d. Only sympathetic preganglionic neurons secrete norepinephrine.

A

Splanchnic nerves a. are part of the parasympathetic division. b. have preganglionic neurons that synapse in the collateral ganglia. c. exit from the cervical region of the spinal cord. d. travel from the spinal cord to the sympathetic chain ganglia. e. All of these are correct.

B

A drug is known to decrease heart rate. After cutting the white rami of T1-T4, the drug still causes the heart rate to decline. After cutting the vagus nerves, the drug no longer affects heart rate. Which division of the ANS does the drug affect? Does the drug affect the synapse between preganglionic and postganglionic neurons, the synapse between postganglionic neurons and effectors, or the CNS? Is the drug's effect excitatory or inhibitory?

Because cutting the white rami of T1-T4 does not affect the drug's action, sympathetic preganglionic neurons in the spinal cord and sympathetic centers in the brain can be ruled out as a site of action. Because cutting the vagus nerves eliminates the drug's effect, the drug cannot be acting at the synapse between the preganglionic neurons and the postganglionic neurons, or between the synapse of the postganglionic neuron and the effector of either division of the ANS. The drug must therefore excite parasympathetic centers in the brainstem, resulting in decreased heart rate.

A drug blocks the sympathetic division's effect on the heart. Careful investigation reveals that, after administration of the drug, normal action potentials are produced in the sympathetic preganglionic and postganglionic neurons. Also, injection of norepinephrine produces a normal response in the heart. Explain, in as many ways as you can, the mode of action of the unknown drug.

Because normal action potentials are produced, the drug does not act at the synapse between the preganglionic and postganglionic neurons. Because injected norepinephrine works, sympathetic receptors in the heart are functioning and are not affected by the drug. Therefore, the drug must somehow affect the postganglionic neurons. Possibly it inhibits neurotransmitter production or release from the postganglionic neurons.

A sudden increase in blood pressure a. initiates a sympathetic reflex that decreases heart rate. b. initiates a local reflex that decreases heart rate. c. initiates a parasympathetic reflex that decreases heart rate. d. Both a and b are correct. e. Both b and c are correct.

C

When acetylcholine binds to nicotinic receptors, a. the cell's response is mediated by G proteins. b. the response can be excitatory or inhibitory. c. Na+ channels open. d. the binding occurs at the effectors. e. All of these are correct.

C

Which of these events is expected if the sympathetic division is activated? a. Secretion of watery saliva increases. b. Tear production increases. c. Air passageways dilate. d. Glucose release from the liver decreases. e. All of these are correct.

C

Given these structures: (1) collateral ganglion (2) sympathetic chain ganglion (3) white ramus communicans (4) splanchnic nerve Choose the arrangement that lists the structures in the order an action potential travels through them on the way from a spinal nerve to an effector. a. 1,3,2,4 b. 1,4,2,3 c. 3,1,4,2 d. 3,2,4,1 e. 4,3,1,2

D

Sympathetic axons reach organs through all of the following except a. abdominopelvic nerve plexuses. b. head and neck nerve plexuses. c. thoracic nerve plexuses. d. pelvic splanchnic nerves. e. spinal nerves.

D

The sympathetic division a. is always stimulatory. bis always inhibitory. c. is usually under conscious control. d. generally opposes the actions of the parasympathetic division. e. Both a and c are correct.

D

Which of the following statements regarding the adrenal gland is true? a. The parasympathetic division stimulates the adrenal gland to release acetylcholine. b. The parasympathetic division stimulates the adrenal gland to release epinephrine. c. The sympathetic division stimulates the adrenal gland to release acetylcholine. d. The sympathetic division stimulates the adrenal gland to release epinephrine.

D

Which of these cranial nerves does not contain parasympathetic fibers? a. oculomotor (III) b. facial (VII) c. glossopharyngeal (IX) d. trigeminal (V) e. vagus (X)

D

Which of these is not a part of the enteric nervous system? a. ANS motor neurons b. neurons located only in the digestive tract c. sensory neurons d. somatic motor neurons

D

Given these phrases: (1) neuron cell bodies in the nuclei of cranial nerves (2) neuron cell bodies in the lateral gray horn of the spinal cord (T1-L2 and S2-S4) (3) two synapses between the CNS and effectors (4) regulates smooth muscle Which of the phrases are true for the autonomic nervous system? a. 1,3 b. 2,4 c. 1,2,3 d. 2,3,4 e. 1,2,3,4

E

Nicotinic receptors are located in a. postganglionic neurons of the parasympathetic division. b. postganglionic neurons of the sympathetic division. c. membranes of skeletal muscle cells. d. Both a and b are correct. e. all of these sites.

E

The cell bodies of the postganglionic neurons of the sympathetic division are located in the a. sympathetic chain ganglia. b. collateral ganglia. c. terminal ganglia. d. dorsal root ganglia. e. Both a and b are correct.

E

The parasympathetic division a. is also called the craniosacral division. b. has preganglionic axons in cranial nerves. c. has preganglionic axons in pelvic splanchnic nerves. d. has ganglia near or in the wall of effectors. e. All of these are correct.

E

Which of these structures is innervated almost exclusively by the sympathetic division? a. gastrointestinal tract b. heart c. urinary bladder d. reproductive tract e. blood vessels

E

Epinephrine is routinely mixed with local anesthetic solutions. Why?

Epinephrine causes vasoconstriction and confines the drug to the site of administration. This increases the drug's duration of action locally and decreases its systemic effects. Vasoconstriction also reduces bleeding if a dry field (an area clear of blood on its surface) is required.

A patient has been exposed to the organophosphate pesticide malathion, which inactivates acetylcholinesterase. Which of the following symptoms would you predict: blurring of vision, excess tear formation, frequent or involuntary urination, pallor (pale skin), muscle twitching, or cramps? Would atropine be an effective drug to treat the symptoms? (See Clinical Impact, "Influence of Drugs on the Autonomic Nervous System," for the action of atropine.) Explain.

Inactivation of acetylcholinesterase results in a buildup of acetylcholine in synapses and an overstimulation of muscarinic receptors. One would expect mostly parasympathetic effects because the effects of acetylcholine are enhanced: blurred vision as a result of contraction of ciliary muscles, excess tear formation because of overstimulation of the lacrimal glands, and frequent or involuntary urination because of overstimulation of the urinary bladder. Pallor resulting from vasoconstriction in the skin is a sympathetic effect that would not be expected because skin blood vessels respond to norepinephrine. Muscle twitching or cramps of skeletal muscles might occur because they normally respond to acetylcholine. Atropine, a muscarinic blocking agent, can be used to treat exposure to malathion.

Reduced secretion from salivary and lacrimal glands can indicate damage to what nerve?

Reduced salivary and lacrimal gland secretions can indicate damage to the facial nerves, which innervate the submandibular, sublingual, and lacrimal glands. The glossopharyngeal nerves innervate the parotid glands, but not the lacrimal glands.

When a person is startled or sees a "pleasurable" object, the pupils of the eyes may dilate. What division of the ANS is involved in this reaction? Describe the nerve pathway involved.

The sympathetic division of the ANS is responsible for dilation of the pupil. Preganglionic fibers from the upper thoracic region of the spinal cord pass through spinal nerves (T1 and T2), into the white rami communicantes, and into the sympathetic chain ganglia. The preganglionic fibers ascend the sympathetic chain and synapse with postganglionic neurons in the superior cervical sympathetic chain ganglia. The axons of the postganglionic neurons leave the sympathetic chain ganglia as small nerves that project to the iris of the eye.

Make a list of the responses controlled by the ANS in (a) a person who is extremely angry and (b) a person who has just finished eating and is relaxing.

a. Responses in a person who is extremely angry are primarily controlled by the sympathetic division of the ANS. These responses include increased heart rate and blood pressure, decreased blood flow to the internal organs, increased blood flow to skeletal muscles, decreased contractions of the intestinal smooth muscle, flushed skin in the face and neck region, and dilation of the pupils of the eyes. b. For a person who has just finished eating and is relaxing, parasympathetic reflexes are more important than sympathetic reflexes. The blood pressure and heart rate are at normal resting levels, the blood flow to the internal organs is greater, contractions of smooth muscle in the intestines are greater, and secretions that achieve digestion are more active. If the urinary bladder or the colon becomes distended, autonomic reflexes that result in urination or defecation can result. Blood flow to the skeletal muscles is reduced.

Patients with diabetes mellitus can develop autonomic neuropathy, which is damage to parts of the autonomic nerves. Given the following parts of the ANS—vagus nerve, oculomotor nerve, splanchnic nerve, pelvic splanchnic nerve, outflow of gray ramus—match the part with the symptom it would produce if the part were damaged: a. impotence b. subnormal sweat production c. relaxed stomach muscles and delayed emptying of the stomach d. diminished pupil reaction (constriction) to light e. bladder paralysis with urinary retention

a. pelvic splanchic nerves b. outflow of gray ramus c. vagus nerve d. oculomotor nerve e. pelvic splanchic nerve