The Endocrine System

Question 1

What does the endocrine system regulate?

Answer 1

Development, growth, reproduction, parturition, lactation, metabolism, BP, blood ion conc, behaviour

Question 2

What is endocrine signalling?

Answer 2

Signalling mediators are released into the bloodstream from endocrine cells
- Enables cell signalling across long distances to target tissues
- Slow
- Specific to receptors but not tissues
- Endocrine glands do not have ducts

Question 3

Where are endocrine cells located?

Answer 3

• Close proximity to capillary beds
• Found in endocrine tissues or glands

Question 4

What are hormones?

Answer 4

Signalling mediators
Can be:
- Protein e.g. insulin
- Amino acid derived e.g. adrenaline
- Steroid e.g. estradiol

Question 5

What does the type of hormone influence?

Answer 5

Its cells membrane permeability

Question 6

How are peptide hormones synthesised?

Answer 6

From amino acids

Question 7

How are AA derived hormones synthesised?

Answer 7

Derivatives of tyrosine
Requires specific enzymes

Question 8

How are steroid hormones synthesised?

Answer 8

Metabolites of cholesterol
Requires specific enzymes

Question 9

How are peptide hormones released?

Answer 9

Secretory granules by exocytosis

Question 10

How are AA derived hormones released?

Answer 10

Vesicles via exocytosis
(except thyroid hormone)

Question 11

How are steroid hormones released?

Answer 11

Lipid soluble so can cross membranes directly

Question 12

Where do peptide and AA derived hormones bind to receptors?

Answer 12

On cell surface membrane
(except thyroid)

Question 13

Where do steroid hormones bind to receptors?

Answer 13

Diffuse into cells and bind to intracellular/nuclear receptors

Question 14

What is the response time of peptide and AA derived hormones?

Answer 14

Seconds to minutes
(except thyroid)

Question 15

What is the response time of steroid hormones?

Answer 15

Hours to days

Question 16

What are the 7 classic endocrine glands?

Answer 16

Anterior and posterior pituitary
Thyroid
Parathyroids
Adrenals (cortex and medulla)
Ovaries
Testes
Endocrine pancreas

Question 17

What are the endocrine tissues?

Answer 17

Hypothalamus
Kidneys
GI tract
Heart
liver
Adipose tissue

Question 18

What could locally acting hormones be classed as?

Answer 18

Paracrine factors or neuropeptides

Question 19

What is the adenohypophysis?

Answer 19

Anterior lobe of pituitary gland
Develops from an upward projection of the pharynx

Question 20

What is the neurohypophysis?

Answer 20

Posterior lobe of pituitary gland
Develops from a downward projection of the brain

Question 21

How are hormones released from adenohypophysis?

Answer 21

• Neurohormones released into portal system
• Releasing hormones move in bloodstream into anterior pituitary
• Stimulates troph cells within anterior pituitary
• Depending on the releasing hormone - acts on different troph cells to release different tropic hormones - go round body in systemic circulation

Question 22

What is the structure of the adenohypophysis?

Answer 22

Smaller diameter hypothalamic neurones with shorter axons that terminate on blood vessels around pituitary stalk

Question 23

What is the structure of the neurohypophysis?

Answer 23

• Hypothalamus has lots of different nuclei within it
• Cell bodies sit in the hypothalamus in the different nuclei
• They send axonal projections down through the pituitary stalk and into posterior pituitary

Question 24

How are hormones released from the neurohypophysis?

Answer 24

Neural hormones released from the large diameter neurones directly into systemic circulation

Question 25

What hormones are released by the neurohypophysis?

Answer 25

ADH, Oxytocin

Question 26

What hormones are released by adenohypophysis?

Answer 26

In response to releasing hormones: - Growth hormone - TSH - FSH, LH - Prolactin

Question 27

What does the thyroid gland release?

Answer 27

T3 and T4 AA derived hormones

Question 28

What is required for the synthesis and release of thyroid hormones?

Answer 28

Hypothalamic pituitary hormones Iodine

Question 29

How are thyroid hormones transported?

Answer 29

Facilitated diffusion

Question 30

What does thyroid hormone bind to?

Answer 30

Nuclear receptors - bind to DNA and regulate transcription

Question 31

What does thyroid hormone regulate?

Answer 31

Metabolism Development and growth

Question 32

What hormone does the parathyroid gland secrete?

Answer 32

Parathyroid hormone (PTH) (peptide hormone)

Question 33

What does PTH regulate

Answer 33

Vital parameters of plasma calcium and phosphate Targets - bone, kidneys, intestines

Question 34

What is the plasma calcium -ve feedback loop?

Answer 34

Plasma [Ca2+] sensed by chief cells - Increased [Ca2+] Causes decreased PTH release - Decreases kidney tubule reabsorption (so more Ca2+ excreted) - Decreases bone Ca2+ resorption - Decreases intestinal Ca2+ absorption Eventually lowers plasma [Ca2+]

Question 35

What are the parts of the adrenal gland?

Answer 35

Adrenal medulla Adrenal cortex

Question 36

What does the adrenal medulla secrete?

Answer 36

Chromaffin cells release adrenaline by exocytosis in vesicles

Question 37

What is the adrenal medulla a target of?

Answer 37

The ANS

Question 38

What does the adrenal cortex secrete?

Answer 38

Steroid hormones Glucocorticoids e.g. cortisol (from zona glomerulosa) Mineralocorticoids e.g. aldosterone (from zona fasciculata)

Question 39

What do beta cells release?

Answer 39

Insulin

Question 40

What do alpha cells release?

Answer 40

Glucagon

Question 41

What hormones do the ovaries release?

Answer 41

Steroid hormones - oestrogen and progesterone from cells within the developing follicles - Can switch between +ve and -ve feedback

Question 42

Which cells produce testosterone?

Answer 42

Leydig cells in the testes - Testosterone stimulates protein synthesis - can lead to development and growth