24: Endocrine 1

Question 1

What is endocrinology?

Answer 1

The study of hormones, their receptors and their intracellular signalling pathways

Question 2

What are hormones?

Answer 2

Hormones are chemical messengers produced in one location and transported to a second location (target cells) where they exert their effects. Hormones often reach their targets via the bloodstream. They act at low concentrations

Question 3

What are the principal functions of the endocrine system>

Answer 3

Maintain homeostasis -a stable environment in the face of a changing external environment. Example; dehydration

Regulation of growth and development

Control energy storage and use

Mediate the body’s response to environmental cues

Question 4

What occurs with an autocrine hormone

Answer 4

Hormone loops back to itself (target cell is same cell) to create a response

Question 5

What occurs with a paracrine cell?

Answer 5

Cell A —> Hormone —> Cell B —> Response

Question 6

What occurs with an endocrine cell?

Answer 6

Cell A –> hormone –> bloodstream –> hormone —> Cell B —> response

Question 7

What occurs with a neurocrine cell?

Answer 7

Cell A releases hormone via the axon of the cell –> hormone moves along bloodstream —> Targe cell B –> Response

Question 8

What is the chemical classification of peptides?

Answer 8

Less than 50 amino acids

Question 9

What is the chemical classification of proteins?

Answer 9

More than 50 amino acids

Question 10

What is the chemical classification of amines?

Answer 10

Derivatives of tyrosine (amino acids)

Question 11

What is the chemical classification of steroids?

Answer 11

Synthesised from cholesterol

Question 12

What is the chemical classification of prostaglandins?

Answer 12

Synthesised from arachidonic acid

Question 13

Describe the synergistic effects of hormones

Answer 13

Thyroid hormone by itself releases little or no fatty acid to adipose tissue cells

Epinephrine by itself only releases a small amount of fatty acid to adipose tissue cells

However, when you combine epinephrine and thyroid hormone together, you get a large amount of fatty acids released

This is as thryroid hormone increases receptors for epinephrine

Question 14

Describe the role of melatonin.

Answer 14

“the hormone of darkness”

The pineal gland releases melatonin into the blood stream, it then feeds back on SCN as a Zeitgaber (“time giver”) signal

Question 15

Describe hypothalamic control of anterior pituitary hormone secretion

Answer 15

slides

Question 16

Describe the pathway for positive control of growth hormone secretion

Answer 16

GHRH —> Growth hormone –> Liver –> Insulin-like growth factor 1 –> Somatosatin neurons (periventricular nucleus)

Question 17

Describe the negative control of growth hormone secretion. (inhibition)

Answer 17

Somatostatin (SS) inhibits the release of growth hormone. Insulin growth factor 1 goes back to the GHRH

Question 18

Describe the control of growth hormone secretion.

Answer 18

G protein coupled receptor

Slides

Question 19

What are the indirect growth effects of growth hormone?

Answer 19

Stimulates the growth of bones, muscles and other tissues by stimulating cell division (mitogenesis) via insulin-like growth factor (IGF -1)

Question 20

What is the direct effect of growth hormone

Answer 20

Stimulates protein synthesis (in muscle)

Question 21

What are direct metabolic effects of growth hormone>? (2)

Answer 21

Increases blood glucose by stimulating glucose synthesis (in liver) and inhibiting cellular uptake of glucose

Increases triglyceride breakdown and free fatty acid mobilisation in adipose tissue

Question 22

Describe the pattern of growth hormone secretion

Answer 22

-Growth hormone secretion is pulsatile and follows a diurnal pattern

Question 23

Describe the control of hormones on the posterior pituitary gland

Answer 23

Slides

Question 24

What hormones are secreted by the posterior pituitary gland?

Answer 24

• Vasopressin

- Oxytocin

Question 25

What are roles of vasopressin?

Answer 25

• Is secreted in response to increased plasma osmotic pressure or decreased blood volume
• Inhibits urine production (diuresis) in the kidney
• Causes blood vessle contraction (vasoconstriction)

Question 26

What are the roles of oxytocin?

Answer 26

• Acts upon the kidney to promote sodium excretion (natruiresis)
• Increases release of atrial natruiretic factor from the heart
• Contacts mammary ducts for milk let-down during suckling
• Causes uterine contraction during delivery

Question 27

What causes diabetes insipidus?

Answer 27

Secretion of vasopressin is impaired or absent.

So the person would become dehydrated and require a lot of water