MCAT Biology : Sympathetic and Parasympathetic Divisions

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #56 : Divisions Of The Nervous System

Sympathetic nervous system reactions are associated with which of the following?

Possible Answers:

Pupil dilation and increased heart rate

Pupil constriction and decreased heart rate

Pupil dilation and decreased heart rate

Pupil constriction and increased heart rate

Correct answer:

Pupil dilation and increased heart rate

Explanation:

The sympathetic nervous system is associated with the "fight or flight" response. Some bodily responses include pupil dilation, increased heart rate, increased perspiration, increased blood flow to muscles, relaxation of the bladder, and decreased digestion.

Example Question #57 : Divisions Of The Nervous System

Which of the following is a parasympathetic nervous system response?

Possible Answers:

Restrict blood flow to excretory system.

Increase digestive activity

Increase blood flow to skeletal muscle

Increase heart rate

All of these are effects of parasympathetic stimulation

Correct answer:

Increase digestive activity

Explanation:

The correct answer is an increase in digestive activity. The parasympathetic nervous system is involved in "rest and digest" functions. This includes a lowering of heart rate, lowering of blood flow to skeletal muscle, and an increase in digestive functions. The incorrect answers are all responses of the sympathetic nervous system.

Example Question #58 : Divisions Of The Nervous System

You are watching a scary movie with a friend. You look over and note that they are slightly sweating and their eyelids are elevated more than normal. Which part of the nervous system is responsible for this observed reaction?

Possible Answers:

Sympathetic nervous system

Peripheral nervous system

Central nervous system

Parasympathetic nervous system

Correct answer:

Sympathetic nervous system

Explanation:

Your friend is exhibiting the "fight or flight" response, which is mediated by the sympathetic nervous system. Release of norepinephrine by sympathetic postganglionic neurons causes pupil dilation, increased heart rate, and the release of epinephrine from the adrenal medulla.

In contrast, the parasympathetic nervous system is responsible for the "rest and digest" response, which stimulates the digestive tract and lowers heart rate.

Example Question #59 : Divisions Of The Nervous System

A study finds that subjects have difficulty reading small text when subjected to an electric shock. What phenomenon explains this result?

Possible Answers:

The sympathetic nervous system has been activated, causing subjects' pupils to dilate

The parasympathetic nervous system has been activated, causing subjects' pupils to dilate

The parasympathetic nervous system has been activated, causing subjects' pupils to constrict

The sympathetic nervous system has been activated, causing subjects' visual integration to deteriorate

The sympathetic nervous system has been activated, causing subjects' pupils to constrict

Correct answer:

The sympathetic nervous system has been activated, causing subjects' pupils to dilate

Explanation:

Administration of an electric shock would stimulate the release of epinephrine, which would result in activation of the sympathetic nervous system. The sympathetic nervous system is activated in response to short-term stressors and triggers the "fight or flight" response. One result of this response is dilation of the pupils, causing more light to enter and, in theory, enhancing the ability to visually perceive dangers and threats. Dilation of the pupils, however, also results in difficulty focusing on objects very close to the eye, making it difficult to read during sympathetic stimulation.

Example Question #60 : Divisions Of The Nervous System

Which of the following is a correct description of the sympathetic and parasympathetic nervous systems?

Possible Answers:

The sympathetic system is a division of the somatic system, while the parasympathetic system falls under the autonomic system.

The sympathetic and parasympathetic systems derive from both the somatic and autonomic systems.

The sympathetic system is a division of the autonomic system, while the parasympathetic system falls under the somatic system.

Both the sympathetic and parasympathetic systems are divisions of the autonomic system.

Both the sympathetic and parasympathetic systems are divisions of the somatic system.

Correct answer:

Both the sympathetic and parasympathetic systems are divisions of the autonomic system.

Explanation:

The sympathetic (fight or flight) and the parasympathetic (rest and digest) systems control bodily processes that are involuntary, or autonomic. Somatic refers to voluntary actions, which are not controlled by either the sympathetic or parasympathetic systems.

Example Question #1 : Sympathetic And Parasympathetic Divisions

Which of the following pairs describing the sympathetic and parasympathetic nervous systems accurately portray their roles?

Possible Answers:

Sympathetic—vagus nerve, fight or flight

Parasympathetic—epinephrine and norepinephrine, rest and digest

Sympathetic—vagus nerve, rest and digest

Parasympathetic—epinephrine and norepinephrine, fight or flight

Sympathetic—epinephrine and norepinephrine, rest and digest

Parasympathetic—vagus nerve, fight or flight

Sympathetic—epinephrine and norepinephrine, fight or flight

Parasympathetic—vagus nerve, rest and digest

Correct answer:

Sympathetic—epinephrine and norepinephrine, fight or flight

Parasympathetic—vagus nerve, rest and digest

Explanation:

The sympathetic nervous system (fight or flight) releases epinephrine and norepinephrine which activates adrenergic receptors throughout the body, causing bronchodilation, vasodilation to skeletal muscles, and vasodilation to coronary arteries. The parasympathetic nervous system (rest and digest) acts in the opposite manner, slowing the heart rate via the vagus nerve. 

Example Question #1 : Sympathetic And Parasympathetic Divisions

The relaxation of bronchial smooth muscle is stimulated by what type of neuron?

Possible Answers:

Parasympathetic motor neurons

Parasympathetic postganglionic neurons

Sympathetic preganglionic neurons

Somatic motor neurons

Sympathetic postganglionic neurons

Correct answer:

Sympathetic postganglionic neurons

Explanation:

Relaxation of bronchial smooth muscle is an involuntary process, which is accomplished by the autonomic system rather than the somatic. It is also a part of the "fight or flight" response, which relates to the sympathetic system. Postganglionic neurons directly stimulate target tissues, while preganglionic neurons stimulate postganglionic neurons.

Example Question #2 : Sympathetic And Parasympathetic Divisions

The optic nerve is formed from the axons of all retinal ganglion cells. The optic nerves from each eye join at the optic chiasm and eventually enter either the left or right optic tract. The optic tract projects to three subcortical areas. One is the lateral geniculate nucleus, which is responsible for processing visual information. One is the pretectal area, which produces pupillary reflexes based on information from the retina. Finally, the superior colliculus uses the information from the retina to generate eye movement.

When light is shone upon one eye, it causes constriction of the pupil in both eyes. Constriction of the eye in which the light is shone is the direct response while constriction of the other is known as the consensual response. The pupillary reflexes are mediated through retinal ganglion neurons that project to the pretectal area which lies anterior to the superior colliculus. The cells in the pretectal area project bilaterally to preganglionic parasympathetic neurons in the Edinger-Westphal nucleus. This is also known as the accessory oculomotor nucleus. The preganglionic parasympathetic neurons in the Edinger-Westphal nucleus send axons through the oculomotor nerve to innervate the ciliary ganglion. The ciliary ganglion's postganglionic neuron innervates the smooth muscle of the pupillary sphincter.

Why is the area of optic disc also called the 'blind spot'?

Possible Answers:

 Light is unable to reach this small area of the retina

This area is free of photoreceptors 

Color vision is not available at this retinal location

It refers to the resulting pathology that occurs with inflammation of the head of the optic nerve (optic neuritis); a complication involved in various disease processes, most commonly Multiple Sclerosis.

This is the region where ganglion cells leave the retina

Correct answer:

This area is free of photoreceptors 

Explanation:

This area is free of photoreceptors. The blind spot is the area on the retina where the optic nerve bundle leaves the eye. That is not the reason why the area is termed the blind spot. The region is blind because it has no photoreceptors. If there are no photoreceptors to be found, there can be no transduction of light into a visual image.

Example Question #3 : Sympathetic And Parasympathetic Divisions

Both the sympathetic and the parasympathetic nervous systems are essential for homeostasis and for survival. For example, when we are trying to run away from a threat, the sympathetic nervous system is in full effect to allow us to escape from danger. However, when there is no obvious threat, the parasympathetic nervous system tends to be more in control. 

There are similarities and differences between the sympathetic and the parasympathetic nervous systems. In preganglionic nerve fibers, both the sympathetic and the parasympathetic nervous system utilize the neurotransmitter acetylcholine. Closer to the target organ, the parasympathetic nervous system remains dependent on acetylcholine whereas norepinephrine and epinephrine are the predominant neurotransmitters utilized by the sympathetic nervous system. 

When norepinephrine and epinephrine bind to their receptors, different effects are carried out based on the type of receptor, affinity, and location of the receptor. For example, epinephrine has a higher affinity for the beta-2 receptor. When epinephrine binds to the beta-2 receptor, common effects include vasodilation and bronchodilation. Norepinephrine has a stronger affinity for the alpha-1, alpha-2 and beta-1 receptors. When norepinephrine binds to its receptor, common effects on the body include vasoconstriction (alpha-1), increased heart rate (beta-1) and uterine contraction (alpha-1).

James is interested in studying the effects of neurotransmitters based on the location, receptor, and mechanism. While experimenting, he was able to identify a particular neurotransmitter as being released directly onto the target cell. Which of the following is the most plausible pairing of neurotransmitter with the neuron type releasing the hormone?

Possible Answers:

Postganglionic neurons releasing epinephrine

Preganglionic neurons releasing norepinephrine 

Postganglionic neurons releasing acetylcholine

Preganglionic neurons releasing epinephrine

Preganglionic neurons releasing acetylcholine

Correct answer:

Postganglionic neurons releasing acetylcholine

Explanation:

The question states that the neurotransmitter was released directly onto the target cell. Since the neurotransmitter was released directly onto the target cell, the neuron releasing the hormone must have been postganglionic. Sympathetic postganglionic neurons release norepinephrine/epinephrine further away from the target cell whereas parasympathetic postganglionic neurons release acetylcholine on the target cell. Therefore, the neurotransmitter being released must have been acetylcholine.    

Example Question #4 : Sympathetic And Parasympathetic Divisions

The brain is a very delicate structure with little room to move around. Surrounding the brain and the spinal cord are three protective layers in addition to the skull and the vertebral column. Directly surrounding the brain and spinal cord is the pia mater. Following the pia mater is the arachnoid mater. Between the pia mater and the arachnoid mater is the sub-arachnoid space where the cerebrospinal fluid circulates. Finally, the protective layer is the dura mater is loosely attached to the arachnoid mater but is strongly associated with the skull bone.

Depending on the type of injury, a certain type of vein and/or artery are more susceptible to injury. For example, the meningeal artery and vein run through the foramen spinosum and travel between the two layers making up the dura mater. As the artery and the vein are traveling in between the dura mater, there is a vulnerable region at the temple. A strike to the temple region could rupture these vessels and result in a epidural hematoma. 

Traveling from the cerebral cortex to the venous dural sinus (located at certain regions between the two layers of the dura mater) is the cerebral vein. When an injury results in the dura mater shifting away from the arachnoid mater, the cerebral vein could rupture and lead to a subdural hematoma.

A hematoma that affects both the brain and spinal cord could affect which part of the nervous system?

I. Sympathetic nervous system

II. Parasympathetic nervous system 

III. Enteric nervous system 

Possible Answers:

III only

I and II only

III only

I, II, and III

I only

Correct answer:

I, II, and III

Explanation:

The brain and the spinal cord makes up the Central nervous system (CNS). The CNS is broken down into the sympathetic and the parasympathetic branches. The enteric nervous system (nervous system innervating the digestive tract) is a portion of the parasympathetic nervous system.  

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