Human Anatomy and Physiology : Sympathetic Nervous System

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

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Example Questions

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. 

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