Human Anatomy and Physiology : Peripheral Nervous System

Study concepts, example questions & explanations for Human Anatomy and Physiology

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Example Questions

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Example Question #1 : Peripheral Nervous System

Which of the following is a feature of the sympathetic nervous system?

Possible Answers:

Sympathetic fibers exit the spinal cord by dorsal roots of spinal nerves

Sympathetic stimulation causes dilation of blood vessels in the skin of the back and limbs

Some sympathetic fibers pass through the paravertebral ganglia of the sympathetic trunk; other sympathetic fibers synapse there

Some sympathetic fibers leave the central nervous system (CNS) by specific cranial nerves

Correct answer:

Some sympathetic fibers pass through the paravertebral ganglia of the sympathetic trunk; other sympathetic fibers synapse there

Explanation:

The sympathetic nervous system is one of two divisions of the autonomic nervous system; it is responsible for the "fight or flight" response and is involved in homeostasis. Some sympathetic fibers pass through the paravertebral ganglia of the sympathetic trunk, while other sympathetic fibers synapse there.

Parasympathetic nerves are associated with cranial nerves, and the dilation of blood vessels in skin of the back and limbs (the sympathetic system constricts these vessels). Preganglionic neurons originate in the thoracolumbar region of the spinal cord (T2 to L1) then travel to a paravertebral ganglion or prevertebral ganglion, where they synapse with a postganglionic neruon. The paravertebral ganglion are found throughout the length of the spinal cord, including the cervical, thoracic, lumbar, and sacral areas. 

Example Question #41 : Neural Physiology

Which group of neurons releases the neurotransmitters epinephrine and norepinephrine?

Possible Answers:

None of these secrete epinephrine or norepinephrine

Postganglionic neurons in the parasympathetic nervous system

Preganglionic neurons in the parasympathetic nervous system

Preganglionic neurons in the sympathetic nervous system

Postganglionic neurons in the sympathetic nervous system

Correct answer:

Postganglionic neurons in the sympathetic nervous system

Explanation:

The sympathetic nervous system is typically associated with "fight or flight" responses in the body. When you think of stressful situations, it helps to think of adrenaline (or epinephrine) being used by the body. The postganglionic neurons of the sympathetic nervous system will release the neurotransmitter epinephrine or norepinephrine, which will then attach to adrenergic receptors on the effector organ to initiate the sympathetic action.

The neurons of the parasympathetic nervous system and the preganglionic neurons of the sympathetic nervous system use acetylcholine.

Example Question #1 : Peripheral Nervous System

What is the primary neurotransmitter in sympathetic postganglionic neurons?

Possible Answers:

Dopamine

Glycine

Acetylcholine

GABA

Norepinephrine

Correct answer:

Norepinephrine

Explanation:

Norepinephrine is the neurotransmitter that is released by the postganglionic neuron, and stimulates sympathetic responses in effectors. Acetylcholine is the primary neurotransmitter in post ganglionic neurons in the parasympathetic nervous system. Dopamine, GABA, and glycine are other transmitters used by the nervous system, but are not the primary neurotransmitter of the postganglionic sympathetic neurons.

Example Question #1 : Peripheral Nervous System

Which of the following is true when moving from the transverse colon to the descending colon?

Possible Answers:

Parasympathetic innervation changes from pelvic splanchnics to vagus innervation

Sympathetic innervation changes from the thoracic splanchnics to lumbar splanchnics

Venous drainage changes from draining to the portal system to draining to the inferior vena cava

Blood supply changes from superior mesenteric artery to the celiac trunk 

Correct answer:

Sympathetic innervation changes from the thoracic splanchnics to lumbar splanchnics

Explanation:

As one moves from the transverse colon to the descending colon, the sympathetic innervation changes from the thoracic splanchnics to the lumbar splanchnics.

Pelvic splanchnic nerves provide parasympathetic innervation of pelvic and genital organs, including the distal third of the transverse colon, the descending colon, the sigmoid colon, and the rectum rectum. The proximal two thirds of the transverse colon, and the rest of the proximal gastrointestinal tract receives parasympathetic innervation from the vagus nerve.

The superior mesenteric, inferior mesenteric, and iliac arteries provide blood supply for the large intestine. The celiac trunk does not provide blood supply to the large intestine. Branches of the superior mesenteric artery mainly perfuse the transverse colon, while branches of the inferior mesenteric artery mainly perfuse the descending colon. Venous drainage mirrors colonic arterial supply, with both the superior and inferior mesenteric veins joining the hepatic portal vein. 

Example Question #1 : Peripheral Nervous System

How is the parasympathetic branch of the autonomic nervous system organized?

Possible Answers:

Long preganglionic fiber, long postganglionic fiber

Short preganglionic fiber, short postganglionic fiber

Short preganglionic fiber, long postganglionic fiber

Long preganglionic fiber, short postganglionic fiber

Correct answer:

Long preganglionic fiber, short postganglionic fiber

Explanation:

Cell bodies of preganglionic neurons are located in the central nervous system (CNS); they synapse onto autonomic ganglia. Parasympathetic ganglia are located in or near the effector organs giving them long preganglionic fibers and short postganglionic fiber. Sympathetic ganglia are located in the paravertebral chain, thus they have short preganglionic fibers and long postganglionic fibers.

Example Question #1 : Parasympathetic Nervous System

What neurotransmitter is used by the preganglionic and postganglionic neurons of the parasympathetic nervous system, respectively?

Possible Answers:

preganglionic uses acetylcholine; postganglionic uses acetylcholine

preganglionic uses norepinephrine; postganglionic uses acetylcholine

The parasympathetic system only has a preganglionic neuron, which uses acetylcholine as its neurotransmitter.

preganglionic uses norepinephrine; postganglionic uses norepinephrine.

preganglionic uses serotonin; postganglionic uses acetylcholine.

Correct answer:

preganglionic uses acetylcholine; postganglionic uses acetylcholine

Explanation:

The parasympathetic nervous system acts oppositely to the sympathetic nervous system, by signaling the activation of relaxation and digestion (increased blood flow to digestive system, pupil constriction, lower heart rate and blood pressure). The parasympathetic nervous system signal is transmitted to the body through a preganglionic neuron and a postganglionic neuron. Both of these use acetylcholine in the parasympathetic nervous system.

Example Question #1 : Help With Parasympathetic Postganglionic Physiology

Which of the following statements is true concerning the autonomic nervous system?

Possible Answers:

Both the sympathetic and parasympathetic divisions use epinephrine

Parasympathetic postganglionic neurons are found closer to the effector than sympathetic postganglionic neurons

Only the parasympathetic division has signals originating from the spinal cord

The autonomic nervous system is voluntarily controlled

The cranial nerves are considered part of the autonomic nervous system

Correct answer:

Parasympathetic postganglionic neurons are found closer to the effector than sympathetic postganglionic neurons

Explanation:

The autonomic nervous system can be divided into the sympathetic and parasympathetic nervous systems. Although both divisions have target organs and tissues, the parasympathetic postganglionic neurons are usually much closer to the effector organ than sympathetic postganglionic neurons.

The autonomic nervous system is under involuntary control, while the somatic nervous system is under voluntary control. Only sympathetic postganglionic neurons use epinephrine; most autonomic neurons use acetylcholine. Both divisions include neurons that originate from the spinal cord. The cranial nerves have both sensory and motor functions, meaning that they can be involved in either somatic or autonomic innervation.

Example Question #1 : Peripheral Nervous System

Which cranial nerves are part of the visceral efferent parasympathetic in the peripheral nervous system (PNS)?

Possible Answers:

III, VII, IX, and X

III, VII, VIII, and IX

VII, IX, and X

III, VII, IX, and XI

VII and IX

Correct answer:

III, VII, IX, and X

Explanation:

The cranial nerves that are part of the visceral efferent parasympathetic in the PNS are III, VII, IX, and X. Cranial nerve III (oculomotor) travels to the ciliary ganglion and supplies the pupil of the eye for constriction. Cranial nerve VII (facial) travels to the pterygomandibular and submandibular ganglion and supplies the lacrimal and salivary glands. Cranial nerve IX (glossopharyngeal) travels to the otic ganglion and supplies the Parotid gland. Lastly, cranial nerve X (vagus) travels to the Prevertebral plexus and thoracic plexus in order to supply the gut, heart, and enteric system.

Example Question #3 : Help With Parasympathetic Postganglionic Physiology

Atropine is a molecule that is an antagonist to muscarinic cholinergic receptors. Based on your knowledge of autonomic nervous system physiology, how would you expect the pupils to respond to topical administration of atropine?

Possible Answers:

The iris sphincter muscles would experience a relaxed paralysis

There will be no change in pupil size because the pupils do not have muscarinic receptors

The iris sphincter muscles would experience a contracted paralysis

You will observe miosis (pupil constriction)

You will observe mydriasis (pupil dilation)

Correct answer:

You will observe mydriasis (pupil dilation)

Explanation:

The pupillary sphincter muscles contain muscarinic cholinergic receptors that help the eyes to respond to parasympathetic tone. When this parasympathetic signal is blocked (antagonized) via atropine, you will observe a "sympathetic response" at the level of the pupil. In this scenario, you would observe the sympathetic response of pupil dilation. Hint: "aTROP'ine" and "seeing a TROPical setting" both cause your pupils to dilate nice and wide!

Example Question #4 : Help With Parasympathetic Postganglionic Physiology

Which of these is a feature of the parasympathetic nervous system?

Possible Answers:

Some parasympathetic fibers pass through the paravertebral ganglia, others synapse there

Parasympathetic stimulation causes dilation of blood vessels in the skin of the limbs

Some parasympathetic fibers leave the CNS by specific cranial nerves

The parasympathetic nervous system does not involve the spinal cord or spinal nerves

Correct answer:

Some parasympathetic fibers leave the CNS by specific cranial nerves

Explanation:

The parasympathetic nervous system conserves energy and is thus know as the "rest and digest" system. It slows heart rate, increases salivation, lacrimation, urination, deification, digestion, and sexual arousal. The nerves of the parasympathetic system arise in the CNS. Specific nerves include cranial nerves, including the oculomotor nerve, facial nerve, glossopharyngeal nerve, and vagus nerve.

In the sympathetic nervous system some sympathetic fibers pass through the paravertebral ganglia, and others synapse there.

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