Endocrinology

Question 1

What are the 3 zones of the cortex and what dose each of these zones produce?

Answer 1

Glomerula = Aldosterone ‘salt’

Fascicular = Cortisol ‘suger’

Reticular = Androgens ‘sex’

Question 2

Where has the adrenal medulla been derived from?

a) Ectodermal neural crest cells
b) Endoderm
c) Mesoderm

Answer 2

Adrenal Medulla from ectodermal neural crest cells

Adrenal Cortex from mesoderm

Question 3

Which cells found in the adrenal gland secrete catecholamines?

Answer 3

Chromaffin cells

In the medulla only

Catecholamine eg adrenaline at times of stress for ‘fight/flight’ response

Question 4

Describe the anatomical position of the pituitary gland giving the name of its connection with the hypothalamus

Answer 4

Lies in the sella tunica of the spenoid bone

Below the hypothalamus

Connected by the infundibulum or pituitary stalk

- Contains axons from neurons in the hypothalamus and vessels

Question 5

Give the other names for:

a) Adenohypophysis
b) Neurohypophysis

Answer 5

a) Adenohypophysis = Anterior pituitary
b) Neurohypophysis = Posterior pituitary

Question 6

Briefly explain the embryonical differences betweent the anterior and posterior pituitary gland

Answer 6

Anterior pituitary gland - from an invagination of the pharynx Rathke’s pouch

Posterior pituitary gland - an extension of neural tissue from the hypothalamus

Question 7

What are the two well defined clusters of hypothalamic neurons that have axons which extend down the infundibulum and end in the posterior pituitary near the capillaries?

Answer 7

Supraoptic and paraventricular nuclei

Question 8

The posterior pituitary secretes 2 hormones, for both give:

a) Name
b) Primary nuclei involved
c) Effect of the hormone

Answer 8

Vasopressin - Anti diuretic hormone. Increases BP - Increase Na+ and H20 retention by increasing number of aquaporins & causes vasoconstriction.

Supraoptic nuclei.

Oxytocin - Expression of milk from the glands of the breast to the nipple. Promotes the onset of labour contractions.

Paraventricular nuclei.

Question 9

For the posterior pituitary gland’s hormones (vasopressin and oxytocin) give:

a) Where they are made
b) Mechanism by which they are transported to capillaries

Answer 9

a) Cell bodies of the supraoptic and paraventricular nuclei
b) Hormones in vesicles.

Transported in axoplasm of neurons

Accumulate in the terminal axons in posterior pituitary.

Stimuli generates AP in neurons

Triggers release by exocytosis

Hormones enter capillaries and therefore the circulation

Question 10

Vasopressin binds to G protein coupled 7 transmembrane domain receptors. Give where each of the following receptors are?

a) V1a
b) V2
c) V1b

Answer 10

a) V1a = Vasculature
b) V2 = Renal collecting tubules
c) V1b = Pituitary

Question 11

Describe the feedback loop when there is an excess of water.

Answer 11

Excess of water due to ingestion

Decreased plasma molarity & Increase cellular hydration

Decreased thirst (= less intake) & decreased vasopressin secretion ( = less Na+ and H20 reabsorbed leading to more urine)

= Reduction in total body water volume

Question 12

Give the mechanism of how vasopressin increases blood pressure.

Answer 12

Vasopressin binds to V2 receptors on the basolateral membrane in the collecting ducts of the kidneys

Stimulates intracellular cascade

Aquaporin 2 proteins are synthesised and inserted into the apical membrane

• increases permeability of the renal collecting duct

= More water reabsorbed & decrease in plasma osmolality

Question 13

Describe the feedback of oxytocin starting at

a) Suckling at the nipple
b) Uterus dilation

Answer 13

a) Suckling at the nipple - +ve FB to paraventricular nuclei - AP down neurons to release oxytocin by exocytosis - enters capilaries & circulaiton - contration of smooth muscle in lactating glands of breast Myoepithelial cells of the mammary glands = milk ejection
b) Uterus dilation - +ve FB to paraventricular nuclei - AP down neurons to release oxytocin by exocytosis - enters capilaries & circulaiton - with estrogens causes contractions = labour

Question 14

What is the the median eminence?

Answer 14

• Junction between the hypothalamus and the infundibulum
• Capillaries recombine to give the hypothalamo-pituitary portal vessels (local route of blood from the hypothalamus to the anterior pituitary gland - ensures the hypophysiotropic hormones reach the anterior pituitary with little delay)

Question 15

Give the 6 hormones produced from then anterior pituitary gland

Answer 15

1. Folicle stimulating hormone (FSH)
2. Luteinizing hormone (LH)
3. Growth hormone (GH)
4. Thyroid-stimulating hormone (TSH)
5. Prolactin
6. Adrenocorticotrophic hormone

Question 16

What are hypophysiotrophic hormones?

Answer 16

Hypophysiotrophic hormones = the hypothalmic hormones that regulate anterior pituitary function

3 hormone sequence:

Hypophysiotrophic hormone controls the secretion of the anterior pituitary hormone whcih controls the secretion of a 3rd hormone from the endocrine gland.

(Adaptive, variable feedback & amplification)

Question 17

Give the mechanism by which cortisol can be released into the circulation

Answer 17

Physical/emotional stress

Neural inputs to hypothalamus

Hypothalamus increased corticotrophin-releasing hormone (CRH)

Increase of CRH in hypothalamo-pituitary portal vessels

Anterior pituitary increases adrenocorticotrophic hormone (ACTH) in blood

Adrenal cortex increases cortisol secretion

• Note: Cortisol has -ve feedback on anterior pituitary and hypothalamus to dampen hormonal secretion

Question 18

What are the effects of increased plasma cortisol concentraion during stress?

Answer 18

1. Organic metabolism: Stimulation of protein catabolism, gluconeogenesis, release of glycerol and fatty acids into blood.
2. Enhanced vascular reactivity (maintain vasoconstriction)
3. Protects against the damage of stress
4. Inhibition of inflammation and specific immune responses
5. Inhibition of non-essential functions