Chapter 17 Chapter checkpoints and review test The Autonomic Nervous System

Postganglionic fibers of autonomic neurons are usually (a) myelinated. (b) unmyelinated. (c) larger than preganglionic fibers. (d) located in the spinal cord.

(b) unmyelinated

Which of the following ganglia belong to the sympathetic division of the ANS? (a) otic ganglion (b) sphenopalatine ganglion (c) sympathetic chain ganglia (d) all of the above

(c) sympathetic chain ganglia

Describe the general organization of the pathway for visceral motor output.

Visceral motor neurons, called preganglionic neurons, send their axons, called preganglionic fibers, from the CNS to synapse on ganglionic neurons, whose cell bodies are located in ganglia outside the CNS.

Damage to the ventral roots of the first five thoracic spinal nerves on the right side of the body would interfere with the ability to (a) dilate the right pupil. (b) dilate the left pupil. (c) contract the right biceps brachii. (d) contract the left biceps brachii.

(a) dilate the right pupil.

What anatomical mechanism is involved in causing a person to blush? (a) Blood flow to the skin is increased by parasympathetic stimulation. (b) Sympathetic stimulation relaxes vessel walls, increasing blood flow to the skin. (c) Parasympathetic stimulation decreases skin muscle tone, allowing blood to pool at the surface. (d) Sympathetic stimulation increases respiratory oxygen uptake, making the blood brighter red.

(b) Sympathetic stimulation relaxes vessel walls, increasing blood flow to the skin.

Splanchnic nerves (a) are formed by parasympathetic postganglionic fibers. (b) include preganglionic fibers that go to collateral ganglia. (c) control sympathetic function of structures in the head. (d) connect one chain ganglion with another.

(b) include preganglionic fibers that go to collateral ganglia.

Sympathetic preganglionic fibers are characterized as being (a) short in length and unmyelinated. (b) short in length and myelinated. (c) long in length and myelinated. (d) long in length and unmyelinated.

(b) short in length and myelinated.

All preganglionic autonomic fibers release _____ at their axon terminals, and the effects are always _____. (a) norepinephrine; inhibitory (b) norepinephrine; excitatory (c) acetylcholine; excitatory (d) acetylcholine; inhibitory

(c) acetylcholine; excitatory

The large cells in the adrenal medulla, which resemble neurons in sympathetic ganglia, (a) are located in the adrenal cortex. (b) release acetylcholine into blood capillaries. (c) release epinephrine and norepinephrine into blood capillaries. (d) have no endocrine functions.

(c) release epinephrine and norepinephrine into blood capillaries.

Cutting the ventral root of the spinal nerve at L2 would interrupt the transmission of what type of information? (a) voluntary motor output (b) ANS motor output (c) sensory input (d) a and b

(d) a and b

The neurotransmitter at all synapses and neuroeffector junctions in the parasympathetic division of the ANS is (a) epinephrine. (b) cyclic AMP. (c) norepinephrine. (d) acetylcholine.

(d) acetylcholine.

The white ramus communicans (a) carries the postganglionic fibers to the effector organs. (b) arises from the dorsal root of the spinal nerves. (c) has fibers that do not diverge. (d) carries the preganglionic fibers into a nearby sympathetic chain ganglion.

(d) carries the preganglionic fibers into a nearby sympathetic chain ganglion.

If the visceral signal from the small intestine does not reach the spinal cord, which structures might be damaged? (a) preganglionic neurons (b) white rami communicantes (c) gray rami communicantes (d) none of the above

(d) none of the above

Visceral motor neurons in the CNS (a) are ganglionic neurons. (b) are in the dorsal root ganglion. (c) have unmyelinated axons except in the lower thoracic region. (d) send axons to synapse on peripherally located ganglionic neurons.

(d) send axons to synapse on peripherally located ganglionic neurons.

Preganglionic fibers of the ANS sympathetic division originate in the (a) cerebral cortex of the brain. (b) medulla oblongata. (c) brainstem and sacral spinal cord. (d) thoracic and lumbar spinal segments.

(d) thoracic and lumbar spinal segments.

In some severe cases, a person suffering from stomach ulcers may need to have surgery to cut the branches of the vagus nerve that innervates the stomach. How would this help the problem?

Cutting off autonomic nervous system stimulation to the stomach through the vagus nerve decreases stimulation of digestive glands, thus reducing their secretion. This may diminish ulcers in the wall of the stomach.

Kassie is stung on the neck by a wasp. Because she is allergic to wasp venom, her throat begins to swell and her respiratory passages constrict. Which would be more helpful in relieving her symptoms: acetylcholine or epinephrine? Why?

Kassie should be treated with epinephrine. This would mimic sympathetic activation, which dilates air passageways in the lungs. The constriction of her respiratory passages would be alleviated.

Describe preganglionic fibers and neurons and postganglionic fibers and neurons.

Preganglionic fibers are short with myelinated axons; preganglionic neurons have their cell bodies in the CNS, and their axons project to ganglia in the PNS. Postganglionic fibers are long and unmyelinated; postganglionic neurons have their cell bodies in ganglia in the PNS, and their axons innervate effector cells.

Where do the preganglionic fibers of the parasympathetic division of the ANS originate?

Preganglionic fibers of the parasympathetic division of the ANS originate in either the brainstem (cranial nerves III, IX, and X) or the sacral spinal cord.

Individuals with high blood pressure may be given a medication that blocks beta receptors. How would this medication help their condition?

Blocking the beta receptors on cells would decrease or prevent sympathetic stimulation of those tissues. This would result in decreased heart rate and force of contraction and relaxation of the smooth muscle in the walls; the combination would lower blood pressure.

Where are intramural ganglia located?

Intramural ganglia are located in the tissues of their target organs.

Name the neurotransmitter released by most postganglionic sympathetic fibers.

Norepinephrine is the neurotransmitter released by most postganglionic sympathetic fibers

Describe sympathetic chain ganglia and collateral ganglia

Sympathetic chain ganglia (paravertebral ganglia) are on both sides of the vertebral column. Neurons in these ganglia control effectors in the body wall, inside the thoracic cavity, and in the head and limbs. Collateral ganglia (prevertebral ganglia) are anterior to the vertebral column. Neurons on these ganglia innervate tissues and organs in the abdominopelvic cavity

How do sympathetic chain ganglia differ from both collateral ganglia and intramural ganglia?

Sympathetic chain ganglia are innervated by preganglionic fibers from the thoracolumbar regions of the spinal cord, and they are interconnected by preganglionic fibers and axons from each ganglion in the chain innervating a particular body segment. The collateral ganglia are part of the abdominal autonomic plexus anterior to the vertebral column. Preganglionic sympathetic fibers innervate the collateral ganglia as splanchnic nerves. Intramural ganglia are part of the parasympathetic division. They are located near or within the tissues of the visceral organs

Why does sympathetic stimulation have such widespread effects?

Sympathetic stimulation has such widespread effects because (1) the extensive divergence of preganglionic fibers in the sympathetic division distributes sympathetic output to many different visceral organs and tissues simultaneously, and (2) the release of E and NE by the adrenal medullae affects tissues and organs throughout the body.

Name three plexuses in the abdominopelvic cavity

The celiac plexus, the inferior mesenteric plexus, and the hypogastric plexus are three plexuses in the abdominopelvic cavity

Where do the nerve fibers that synapse in the collateral ganglia originate?

The neurons that synapse in the collateral ganglia originate in the inferior thoracic and superior lumbar regions of the spinal cord and pass through the sympathetic chain ganglia without synapsing before reaching the collateral ganglia.

Why are the effects of parasympathetic stimulation more specific and localized than those of the sympathetic division?

The parasympathetic division innervates only visceral structures served by some cranial nerves or lying within the thoracic and/or abdominopelvic cavities. The sympathetic division has widespread impact due to extensive collateral branching of preganglionic fibers, which reach visceral organs and tissues throughout the body.

Compare the general effects of the sympathetic and parasympathetic divisions of the ANS.

The sympathetic division of the ANS stimulates metabolism, increases alertness, and prepares for emergency in "fight-or-flight." The parasympathetic division promotes relaxation, nutrient uptake, energy storage, and "rest-and-digest."

The effects of epinephrine and norepinephrine released by the adrenal glands last longer than those of either chemical when released at neuroeffector junctions. Why?

There are no enzymes to break down epinephrine and norepinephrine in the blood and very little in peripheral tissues.

What are visceral reflexes?

Visceral reflexes are the simplest functional units in the autonomic nervous system. They provide automatic motor responses that can be modified, facilitated, or inhibited by higher centers, especially those of the hypothalamus.