Chapter 3 - Homeostatic Regulation: Normal Function and Stress Responses

Question 1

The book divides homeostatic regulation into five layers beginning at the lower levels in the system. Can you name them?

Answer 1

1. Organs and their local reflexes
2. Autonomic and endocrine messengers
3. Brainstem regulation
4. Hypothalamic regulation
5. Inputs from higher brain centers

Question 2

The primary hypothalamic nucleus that regulates endocrine and autonomic components of the fight-or-flight response during stress is the …

Answer 2

paraventricular nucleus (PVN)

Question 3

How can the neurosecretory cells of the PVN react to hormones?

Answer 3

The PVN is in contact with the third ventricle.

Question 4

Two stress-related peptides secreted by the hypothalamus to stimulate the pituitary are …

Answer 4

1. Corticotropin-releasing factor (CRF)

2. Arginine vasopressin (AVP).

Question 5

At the anterior pituitary, AVP and CRF cause the secretion of …

Answer 5

adrenocoricotriopic hormone (ACTH) and beta-endorphin.

Question 6

ACTH reaches which target in the body?

Answer 6

ACTH reaches the adrenal cortex.

Question 7

ACTH reaches the adrenal cortex and causes…

Answer 7

causes an increased rate of synthesis and release of cortisol.

Question 8

HPA.

Answer 8

Hypothalamic-pituitary-adrenocortical axis.

Question 9

The endocrine response during stress has two parallel arms. Which?

Answer 9

1. The adrenoocortical response

2. The adrenomedullary response

Question 10

The adrenal medulla is activated by …

Answer 10

The adrenal medulla is activated by sympathetic preganglionic fibers.

Question 11

The adrenal medulla is activated by sympathetic preganglionic fibers originating in …

Answer 11

The adrenal medulla is activated by sympathetic preganglionic fibers originating in the brainstem nucleus of the solitary tract of the spinal cord.

Question 12

During states of stress, the adrenal medulla secretes …

Answer 12

During states of stress, the adrenal medulla secretes epinephrine and norepinephrine into the circulation.

Question 13

In general, the action of epinephrine …

Answer 13

In general, the action of epinephrine reinforces the actions of the sympathetic nerves.

Question 14

What seems to be the role of norepinephrine during stress responses?

Answer 14

Although norepinephrine also enters the bloodstream from the adrenal gland, its actions on target tissues are negligible.

Question 15

Unlike epinephrine, which acts mainly during states of stress, cortisol functions to …

Answer 15

Unlike epinephrine, which acts mainly during states of stress, cortisol functions to maintain homeostasis during normal states of activity and also during periods of stress.

Question 16

What happens to animals deprived of their adrenal cortex (where cortisol is synthesized)?

Answer 16

They’re difficult to keep alive.

Question 17

Addison’s disease causes an insufficiency of adrenal function. What are the symptoms?

Answer 17

Poor salt and water balance, low blood pressure, and other forms of autonomic dysfunction.

Question 18

In the absence of cortisol, epinephrine would be less effective at its target tissues. Why?

Answer 18

Cortisol is necessary for the normal synthesis and function of both alpha and beta-adrenoreceptors.

Question 19

What is cortisol’s diurnal rhythm?

Answer 19

Cortisol secretion shows a very pronounced diurnal rhythm that is integral to its functioning in homeostasis. Cortisol output reaches a peak before awakening, usually about 6:00 a.m. in normal sleepers, and its levels drop slowly until about noon, when a small rise occurs during the midday meal. Cortisol levels vary over the afternoon hours and then decline to a low point during sleep in the early morning hours.

Question 20

How does cortisol affect the hippocampus?

Answer 20

The hippocampus is recognized as the primary site of cortisol’s negative feedback. When cortisol is absent, tonic activity in the hippocampus stimulates the PVN, causing it to release high levels of CRF. When cortisol levels are high, this tonic activity is depressed in the hippocampus.

Question 21

Experimental animals deprive of the adrenal cortex react how during stress?

Answer 21

Because of cortisol’s essential regulatory functions, animals who lack the hormone are prone to death during periods of stress. It is an indication that cortisol during acute stress serves to prevent an overactive stress response from threatening the homeostasis of the individual.