Neuroendocrinology (recap)

Question 1

Describe how the nervous system works

Answer 1

Nervous system uses neurotransmitters to relay messages from one nerve to another or from a nerve to a tissue

Question 2

Describe how the endocrine system works

Answer 2

Endocrine system releases hormones into blood to circulate to
tissues

Question 3

What do endocrine glands do?

Answer 3

Release hormones directly into the blood (ductless)

Question 4

What is the effect of hormones on a tissue determined by?

Answer 4

The effect of a hormone on a tissue is determined by the plasma concentration and the number of active receptors

Question 5

What is plasma hormone concentration determined by?

Answer 5

1. Rate of secretion of hormone from endocrine gland
2. Rate of metabolism or excretion of hormone
3. Quantity of transport proteins
4. Changes in plasma volume

Question 6

What does the magnitude of hormone effect depend on?

Answer 6

1. Concentration of the hormone
2. Number of target receptors on the cell
3. Affinity of the receptor for the hormone

Question 7

What is ‘downregulation’?

Answer 7

Decrease in receptor number in response to high concentration of hormone (e.g., age & -receptors).

Question 8

What is ‘upregulation’?

Answer 8

Increase in receptor number in response to low
concentration of hormone

Question 9

What are the mechanisms of hormone action?

Answer 9

1. Activation of genes to alter protein synthesis.
   * Steroid hormones.
2. Activating ‘second messengers’ in the cell via G protein.
3. Altering membrane transport.
   * Insulin via tyrosine kinase.

Question 10

What are the ‘second messengers’ in the cell?

Answer 10

• Cyclic AMP.
• Ca2+.
• Inositol triphosphate.
• Diacylglycerol.

Question 11

What is the relationship between the hypothalamus and the pituitary gland?

Answer 11

Hypothalamus controls secretions from pituitary gland

Question 12

Where is ADH secreted from and what does it do?

Answer 12

• Secreted from the posterior pituitary gland.
• Reduces water loss from the body to maintain plasma volume.
• Favours reabsorption of water from kidney tubules to capillaries.

Question 13

What is ADH release stimulated by?

Answer 13

1) high plasma osmolality
2) low plasma volume
* Due to sweat loss without water replacement

Question 14

How does ADH concentration change during exercise?

Answer 14

Increases during
exercise >60% VO2
max to maintain plasma
volume.

Question 15

Where is aldosterone secreted from and what does it do?

Answer 15

• Secreted from the adrenal cortex
• Control of Na+ reabsorption and K+ secretion
• Na+/H2O balance
• Regulation of blood volume and blood pressure

Question 16

What stimulates aldosterone release?

Answer 16

• Increased plasma K+ concentration (negative feedback loop)
• Decreased plasma volume

Question 17

Describe the renin-angiotensin-aldosterone system.

Answer 17

Decrease in plasma volume leads to decreased BP at the kidney, or an increase in sympathetic nerve activity. This causes renin to be released leading to angiotensin I (ACE converts to angiotensin II) which triggers aldosterone release increasing Na+ reabsorption.