Textbook Question
Which of the following is not an effect of thyroid hormones?
a. Regulation of the metabolic rate
b. Promotion of growth and development
c. Thermoregulation
d. Synergism with the parasympathetic nervous system
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16. The Endocrine System
The Hypothalamus and Pituitary Gland
Problem 17
Textbook Question
Which of the following statements about the adrenal medulla is false?
a. Secretion from the adrenal medulla is triggered by ACTH and the sympathetic nervous system.
b. The adrenal medulla consists of glandular epithelial cells.
c. The adrenal medulla is a modified postsynaptic sympathetic ganglion.
d. The products of the adrenal medulla prolong the effects of the sympathetic response.
Verified step by step guidance1
Step 1: Begin by identifying the role and structure of the adrenal medulla. The adrenal medulla is the inner part of the adrenal gland and is responsible for secreting catecholamines (epinephrine and norepinephrine) in response to stress.
Step 2: Understand the mechanism of secretion. The adrenal medulla is stimulated by the sympathetic nervous system, specifically by preganglionic sympathetic neurons releasing acetylcholine. It is not directly triggered by ACTH (adrenocorticotropic hormone), which primarily affects the adrenal cortex.
Step 3: Examine the cellular composition of the adrenal medulla. It consists of chromaffin cells, which are modified postsynaptic sympathetic neurons, not glandular epithelial cells. This is a key distinction.
Step 4: Review the function of the adrenal medulla's secretions. The catecholamines (epinephrine and norepinephrine) released by the adrenal medulla enhance and prolong the effects of the sympathetic response, such as increasing heart rate and blood pressure.
Step 5: Compare each statement in the problem to the information above. Identify the false statement by noting that the adrenal medulla does not consist of glandular epithelial cells, making option 'b' the incorrect statement.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Adrenal Medulla Function
The adrenal medulla is the inner part of the adrenal glands and plays a crucial role in the body's fight-or-flight response. It secretes catecholamines, primarily adrenaline (epinephrine) and norepinephrine, which enhance the body's ability to respond to stress by increasing heart rate, blood flow, and energy availability.
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Sympathetic Nervous System
The sympathetic nervous system is part of the autonomic nervous system that prepares the body for stressful or emergency situations. It activates the adrenal medulla, leading to the release of hormones that amplify the body's physiological responses, such as increased heart rate and blood pressure, to prepare for rapid action.
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Hormonal Regulation
Hormonal regulation involves the control of physiological processes through hormones released into the bloodstream. In the context of the adrenal medulla, hormones like ACTH (adrenocorticotropic hormone) can influence its activity, although the primary trigger for catecholamine release is the sympathetic nervous system, highlighting the interplay between neural and hormonal signals.
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