Endocrine Response to Stress

Question 1

What is the structure of the Adrenal gland (from top to bottom)

Answer 1

Capsule
Zona glomerulosa
Zona fasciculata
Zona reticularis
Adrenal medulla

Question 2

What does the Zona glomerulosa produce

Answer 2

Minercorticoids -> Aldosterone

Question 3

What does the Zona fasciculata produce

Answer 3

Glucocorticoid -> Cortisol

Question 4

What does the Zona reticularis produce

Answer 4

Sex steroids -> Androgens

Question 5

What does the Adrenal Medulla produce

Answer 5

Catecholamines -> Adrenaline/Noradrenaline

Question 6

What is Adrenaline synthesised from?

Answer 6

Tyrosine

Question 7

What is the Catecholamine Biosynthetic Pathway?

Answer 7

Question 8

What enzyme converts Tyrosine to L-dopa?

Answer 8

Tyrosine Hydroxylase

Question 9

What cell is Adrenaline synthesised in?

Answer 9

Chromaffin cells of renal medulla

Question 10

What are the steps of Adrenaline MoA?

Answer 10

1. Adrenaline attaches to Adrenergic receptor -> activates G proteins
2. G proteins -> promote adenylyl cyclase -> prod. cyclic AMP
3. Cyclic AMP activates PKA
4. PKA mediates fight/flight

Question 11

Synthesis of Adrenal cortex steroids

Answer 11

Question 12

Describe the steps of the Hypothalamic-Pituitary-Adrenal (HPA) axis

Answer 12

1. Stress -> Parvocellular neuron releases CRH (cortico-trophin releasing hormone)
2. CRH -> produces ACTH (a posterior pituitary hormone)
3. ACTH binds to Adrenal cortex -> stimulates steroid hormone production -> increases activity of steroidogenic enzymes
4. Cortisol feeds back to Hypothalamus -> suppresses ACTH and CRH production

Question 13

Describe the cortisol MoA steps

Answer 13

1. Cortisol binds to Cytosolic Glucocorticoid receptors
2. Cortisol-receptor complexes -> bind to specific DNA sites (GRE)
3. Alters expression of specific genes
4. Proteins synth. in response to cortisol vary depending on the type of cell

Question 14

How does cortisol travel in blood?

Answer 14

• bound to CBG

Question 15

Cortisol metabolic actions

Answer 15

Question 16

Does cortisol have antiinflammatory and immunosuppressive actions?

Answer 16

Yes

Question 17

Does cortisol have anti-reproductive actions?

Answer 17

Yes -> decreases function of reproductive axis at hypothalamic, pituitary and gonadal levels

Question 18

What is Addison’s Disease? and what are symptoms? what is the treatment? what is it usually caused by?

Answer 18

= Adrenal insufficiency
Symptoms:
- weakness
- fatigue
- loss of weight and appetite
- low BSL
- low BP (bc less aldosterone so upsets Na+/K+ balances in blood)
Treatment:
- oral administration of glucocorticoids and minerocorticoids
Causes:
- autoimmune disease

Question 19

What can excess cortisol lead to?

Answer 19

Cushing’s syndrome

Question 20

What is Cushing’s caused by? what effects can it cause?

Answer 20

Causes:
- Cortisol-secreting tumour in adrenal gland (primary)
- ACTH-secreting tumour of anterior pituitary (secondary)
Effects:
- bone strength dimishes
- muscles weaken
- fat on the face, back and belly
- weakened immune system

Question 21

What are the 3 phases of the General Adaptation Syndrome

Answer 21

1. Alarm reaction (6-48 hours)
2. Resistance (>48 hours)
3. Exhaustion (>1-3 months)

Question 22

What are the characteristics and significance of the Alarm reaction stage?

Answer 22

Characteristics:
- stimulation of sympathetic adrenal medulla axis -> release of Adrenaline
Significance:
- fight/flight response

Question 23

What are the characteristics and significance of the Resistance stage?

Answer 23

Characteristics:
- ACTH-glucocorticoids increased
- adrenaline decreased
Significance:
- adaptation to the given stressor increases but decreases to additional stressors

Question 24

What are the characteristics and significance of the Exhaustion stage?

Answer 24

Characteristics:
- symptoms of alarm stage reemerge
- glucocorticoids still increased
Significance:
- depletion of resources brings on diseases and disorders