Question

33. Which of the following responses is NOT part of sympathetic nervous system activation?

a. increased heart rate

b. increased blood pressure

c. increased digestive activity

d. decreased salivary activity

Answer 1

33. Which of the following responses is NOT part of sympathetic nervous system activation?

a. increased heart rate

b. increased blood pressure

c. increased digestive activity

d. decreased salivary activity

Answer:option c increased digestive activity

Reasoning and explanation for the answer choice:

Activation of the sympathetic nervous system causes release of stress hormones epinephrine and norepinephrine that cause the body to respond to stress. It is responsible for maintaining the perfusion to the vital organs[ like the brain and the heart ]of the body that helps to cope up with the stress.

Sympathetic nervous system activation causes decrease in the digestive activity by the following mechanisms:

1.It decreases the activity of the digestive tract by inhibiting the smooth muscle contraction of the gastrointestinal tract and decreasing the intestinal peristalsis.

2.It  diverts the blood flow from the gastrointestinal tract to the vital organs by causing vasoconstriction and decreasing gastrointestinal blood flow.

3. It decreases the volume of digestive enzymes by inhibiting their production and secretion into the gastrointestinal tract.

Increase in the digestive activity is not a part of the response of the sympathetic nervous system activation.The parasympathetic nervous system is responsible for the increase in the digestive activity and the increase in the salivary and enzyme secretions..Hence this option c increased digestive activity is the answer choice.

The reasons why the other options as the answer choice are incorrect

1.The sympathetic nervous system is responsible for the fight or flight response in the body.

2.The secretion of epinephrine and norepinephrine by the sympathetic nervous system are responsible for the positive ionotropic, chronotropic and dromotropic effects on the heart, The positive chronotropic(rate) effect increases the heart rate,Hence option a increased heart rate .is a part of the sympathetic nervous system activation response and not the correct answer.

3.There is vasoconstriction caused by the epinephrine and norepinephrine that is released in response to the sympathetic nervous system activation,which leads to increase in the blood pressure,The positive ionotropic(contractility) effect of epinephrine and norepinephrine also increases the blood pressure by increasing the cardiac contractility.Hence the option b increased blood pressure is a part of the sympathetic nervous system activation response and not the correct answer.

4. The parasympathetic nervous system is essentially responsible for the rest and the digest  function of the body. The parasympathetic system activation increases the digestive activity of the body and increases the salivary secretions and helps the body to perform the function of digestion. The parasympathetic system activation increases the salivary secretions and aids digestion via the neurotransmitter acetylcholine.

The sympathetic stimulation decreases the salivary activity by

1. by decreasing the production of the salivary enzymes by the acinar cells and

2.decreasing the salivary enzyme secretion.

.Hence option d. decreased salivary activity is a part of response of the sympathetic nervous system activation and so not the correct answer.

Answer Summary: As c increased digestive activity is not caused by the sympathetic nervous system activation, this is the correct answer to the question.

Options a. increased heart rate b. increased blood pressure d. decreased salivary activity are the normal responses to the sympathetic nervous system activation.Hence these are not the answer choices.