Lecture 19 - Hormones of the Stress Response

Question 1

Describe the role of the SNS, adrenal medulla, and adrenal cortex in triggering the stress response.

Answer 1

The amygdala reacts to threat, causing the hypothalamus to activate the SNS, releasing epinephrine via the adrenal medulla. The adrenal cortex releases cortisol for continued alertness

Question 2

General Adaptation Syndrome

Answer 2

Describes the stress response in terms of the body’s ability to resist a stressful environment. It divides a response to a stressor into 3 temporal phases.

Phase 1: alarm reaction (mobilize resources)
Phase 2: resistance (cope with stressor)
Phase 3: exhaustion (reserves depleted)

Question 3

Alarm phase of the GAS model

Answer 3

The alarm phase can start within seconds and lasts for up to 1 hour.

Occurs in the adrenal medulla which produces epinephrine, norepinephrine (both contribute to increased physical activity and alertness), alongside sympathetic activation

Question 4

Resistance/recovery phase of the GAS model

Answer 4

Occurs in the adrenal cortex which produces glucocorticoids.

The resistance/recovery phase begins 1hour after stressor onset

Question 5

Exhaustion phase of the GAS model

Answer 5

Occurs under conditions of severe and prolonged stress (weeks to months)

Question 6

How does HPA mediate the recovery phase?

Answer 6

It mediates the slower recovery (or resistance) by:

• Delaying onset (1hr): it takes longer for hormones to bind to target cells -> takes longer to see physiological change
• Prolonging duration (hours): because hormones circulate in the bloodstream, causing effects to last longer

Question 7

What are the effects of glucocorticoids?

Answer 7

They influence nutrient mobilization. Glucocorticoids are glucose-sparing and perform:
- Gluconeogenesis (in the liver)
- Lipolysis in adipocytes
- Enhancement of lipid uptake (non-CNS tissues)

Question 8

What is chronic stress and what does it cause?

Answer 8

Chronic stress response is triggered when moderate stress is sustained over weeks to months. It causes persistent hypercortisolaemia and will cause changes to the alarm phase response for new stressors

Question 9

How does chronic hypercortisolemia disrupt the HPA axis?

Answer 9

Chronic stress damages the hippocampus, suppressing its activity of inhibiting CRH. Amygdala enhances CRH release, leading to more ACTH and glucocorticoids

Question 10

How does the HPA wing help with the stress response?

Answer 10

It directs available nutrients and energy reserves to organ systems that are needed for short term survival