AP Biology : Understanding the Sympathetic and Parasympathetic Divisions

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #1 : Understanding The Sympathetic And Parasympathetic Divisions

The __________ nervous system will __________ the body's heart rate by releasing acetylcholine.

Possible Answers:

parasympathetic . . . reduce

parasympathetic . . . increase

sympathetic . . . reduce

sympathetic . . . increase

Correct answer:

parasympathetic . . . reduce

Explanation:

The parasympathetic nervous system is responsible for the "rest and digest" responses. The sympathetic nervous system, on the other hand, performs the "fight or flight" responses. This question, however, really hinges on knowing the effect of acetylcholine on cardiac muscle. The release of acetylcholine slows the heart rate.

Parasympathetic neurons will only use acetylcholine. Sympathetic neurons signal each other with acetylcholine (preganglionic neurons), but elicit their effects by releasing norepinephrine on their target cells (postganglionic neurons). The effect of norepinephrine on the heart would increase heart rate.

Example Question #2 : Understanding The Sympathetic And Parasympathetic Divisions

Which division of the nervous system increases digestive and urinary activity?

Possible Answers:

Central nervous system

Sympathetic nervous system

Somatic nervous system

Parasympathetic nervous system

Correct answer:

Parasympathetic nervous system

Explanation:

The nervous system has two principle divisions for function and two principle divisions for structure. Structurally, there are the central and peripheral nervous system divisions. Functionally, there are the somatic and autonomic divisions. Within the autonomic nervous system are the sympathetic and parasympathetic divisions.

The somatic nervous system is responsible for voluntary actions, namely the innervation of skeletal muscle. The autonomic nervous system is responsible for all involuntary actions, including smooth muscle contraction, glandular stimulation, and other functions. The parasympathetic nervous system is responsible for the "rest and digest" actions of involuntary organs, increasing digestive and excretory activity. In contrast, the sympathetic nervous system is responsible for the "fight or flight" response, suppressing these activities and stimulating epinephrine release.

Example Question #3 : Understanding The Sympathetic And Parasympathetic Divisions

When stimulated, the vagus nerve slows down heart rate. We can assume that the vagus nerve is classified under which branch of the nervous system?

Possible Answers:

Neuroglia

Sympathetic nervous system

Somatic nervous system

Parasympathetic nervous system

Central nervous system

Correct answer:

Parasympathetic nervous system

Explanation:

Neuroglia are the support cells of the nervous system, and do not conduct action potentials. The central nervous system is composed of only the brain and spinal cord; not nerves. The somatic system controls voluntary movements, so heart rate would not be under its control. The sympathetic nervous system is commonly assigned the "fight or flight" responses, while the parasympathetic nervous system is responsible for "resting and digesting." Since the body is returning to a rested state by lowering heart rate, we would assign this action to the parasympathetic nervous system.

Example Question #4 : Understanding The Sympathetic And Parasympathetic Divisions

Which of the following is not a function of the sympathetic nervous system?

Possible Answers:

Breakdown of glycogen to glucose

Stimulation of digestion/peristalsis

Dilation of pupils

Dilation of bronchi

Acceleration of heartbeat

Correct answer:

Stimulation of digestion/peristalsis

Explanation:

The sympathetic nervous system is responsible for regulating the body's "fight-or-flight" response. Physiological changes produced by the sympathetic nervous system include accelerated heartbeat, dilated bronchi and pupils, glucose breakdown, and inhibited digestion. As a result, when the sympathetic nervous system is active, digestion and its associated involuntary contractions are inhibited—not stimulated.

Example Question #5 : Understanding The Sympathetic And Parasympathetic Divisions

Fight or flight is a decision that all animals must make when confronted with a threat. Regardless of which one, an animal chooses, it will activate the sympathetic nervous system, instead of the parasympathetic nervous system. Which of the the following answers contain actions that will happen in a fight or flight situation?

Possible Answers:

Constricts pupils, secretes epinephrine and norepinephrine, and contracts bronchi

Contracted bladder, relaxed bronchi, simulated salivation

Relaxed skeletal muscle, inhibited digestive activity, dilated pupils

Constricted pupils, accelerated heart rate, contracted bladder

Dilated pupils, accelerated heart rate, relaxed bladder

Correct answer:

Dilated pupils, accelerated heart rate, relaxed bladder

Explanation:

"Dilated pupils, accelerated heart rate, relaxed bladder" is the correct answer here because it is the only choice is entirely comprised of sympathetic nervous system actions. Some red herrings in the other answers is the fact that constricted pupils is a parasympathetic action, as is stimulation of the salivary gland.

Example Question #6 : Understanding The Sympathetic And Parasympathetic Divisions

Upon being approached by a bear in the wilderness, you notice your heart beat faster. Which part of the nervous system is responsible for this feeling?

Possible Answers:

Sympathetic nervous system

Parasympathetic nervous system

Somatic nervous system

Enteric nervous system

Correct answer:

Sympathetic nervous system

Explanation:

The sympathetic nervous system is one branch of the autonomic nervous system in the body. The autonomic nervous system is not under conscious control. The sympathetic system is responsible for our "fight or flight" response. An increase in heart rate when presented with the dangers of being around a bear is due to the sympathetic nervous system. The increase in heart rate is your body's way of increasing blood supply to the body to help you escape ("flight") from the bear and return to safety.

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