Hormonal Axis Physiology

Question 1

Where does the hypothalamus sit?

Answer 1

Above the pituitary gland

Question 2

What does the anterior pituitary gland secrete?

Answer 2

• Thyroid stimulating hormone (TSH)
• Adrenocorticotropic hormone (ACTH)
• Follicle stimulating hormone (FSH) & Luteinising hormone (LH)
• Growth hormone (GH)
• Prolactin

Question 3

What does the posterior pituitary gland secrete?

Answer 3

• Oxytocin (vasopressin)

- Antidiuretic hormone (ADH)

Question 4

What hormone does the hypothalamus release in the thyroid hormone axis?

Answer 4

Thyrotropin releasing hormone (TRH)

Question 5

What does TRH stimulate?

Answer 5

The anterior pituitary to release thyroid stimulating hormone (TSH)

Question 6

What does TSH do?

Answer 6

Stimulates thyroid gland to release triiodothyronine (T3) and thyroxine (T4)

Question 7

Summary of the thyroid hormonal Axis?

Answer 7

Hypothalamus releases TRH (thyrotropin releasing hormone)
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This stimulates the anterior pituitary to release thyroid stimulating hormone (TSH)
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This stimulates the thyroid gland to release triiodothyronine (T3) and thyroxine (T4)
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T3 & T4 suppress the release of TRH and TSH, resulting in lower amounts of T3 and T4
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Lower levels of T3 & T4 offer LESS suppression of TRH and TSH
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Therefore more TSH and TRH are released, equalling a rise in T3 and T4
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This is negative feedback

Question 8

What organs sense T3 and T4?

Answer 8

Sensed by hypothalamus and anterior pituitary

Question 9

What is the role of T3 and T4 ?

Answer 9

Suppress the release of TRH and TSH, resulting in lower amounts of T3 & T4

Question 10

What does suppressing TRH and TSH result in?

Answer 10

Lower amounts of T3 and T4

Question 11

What happens when there are lower levels of T3 and T4?

Answer 11

Offer less suppression of TRH and TSH, therefore more TSH and TRH are released equalling a rise in T3 and T4

Question 12

The level of thyroid hormone is regulated by?

Answer 12

Negative feedback

Question 13

What secretes cortisol?

Answer 13

2 Adrenal glands which sit above the kidneys

Question 14

What is release of cortisol controlled by?

Answer 14

Hypothalamus

Question 15

What is a trigger for cortisol release?

Answer 15

Stress

Question 16

Cortisol is released in a _______ variation?

Answer 16

Diurnal variation

Question 17

What does diurnal variation mean?

Answer 17

Increase and decrease at different times of day

Question 18

When is the cortisol at peak?

Answer 18

Early morning (triggers wake up)

Question 19

When is cortisol low?

Answer 19

Late night- triggers sleep

Question 20

What does the hypothalamus release in the adrenal axis?

Answer 20

Corticotrophin release hormone (CRH)

Question 21

What does CRH stimulate the release of?

Answer 21

Anterior pituitary to release adrenocorticotrophic hormone (ACTH)

Question 22

What does ACTH stimulate the release of?

Answer 22

Cortisol from the adrenal gland

Question 23

The series of hormone stimulation on the adrenal hormone axis?

Answer 23

CRH > ACTH > Cortisol

Question 24

What is cortisol sensed by?

Answer 24

Hypothalamus and anterior pituitary

Question 25

What does cortisol do to hormones?

Answer 25

Suppress the release of CRH and ACTH, resulting in lower amounts of cortisol

Question 26

Actions of cortisol?

Answer 26

- Inhibits immune system - Inhibits bone formation - Increases metabolism - Raises blood glucose - Increases alertness

Question 27

Where is growth hormone releasing hormone (GHRH) released from?

Answer 27

Hypothalamus

Question 28

What does GHRH stimulate?

Answer 28

Growth hormone release from anterior pituitary

Question 29

What does GH stimulate?

Answer 29

Release of insulin-like growth factor 1 (IGF-1) from the liver

Question 30

Where releases IGF-1?

Answer 30

Liver

Question 31

Functions of growth hormone?

Answer 31

- Stimulates muscle growth - Increases bone density - Stimulates cell regeneration & reproduction - Stimulates growth of internal organs

Question 32

What releases parathyroid hormone (PTH)?

Answer 32

4 parathyroid glands

Question 33

What triggers PTH release?

Answer 33

Low serum calcium and low Mg and high serum phosphate

Question 34

What does PTH do?

Answer 34

- Increases the activity and number of osteoclasts in bone, causing reabsorption of Ca from bone into blood therefore increasing serum calcium concentration - Stimulates increase in calcium reabsorption in kidneys- meaning less calcium in urine -Stimulates kidneys to convert Vit D3 into calcitriol (active form of Vit D3) which PROMOTES Ca absorption from food in the small intestine

Question 35

3 effects of PTH?

Answer 35

- Increased calcium absorption from bone - Increase calcium absorption from kidneys - Increase calcium absorption from small intestine

Question 36

What do the effects of PTH overall do?

Answer 36

Help to raise level of serum calcium

Question 37

What happens when serum calcium is high?

Answer 37

Suppresses release of PTH (via negative feedback) reducing serum calcium level

Question 38

Where is renin secreted from?

Answer 38

Juxtaglomerular cells that sit in afferent (some efferent) arterioles in the kidneys

Question 39

What do juxtaglomerular cells do?

Answer 39

Sense the BP in vessels they secrete more renin in response to LOW BP and secrete less renin in response to HIGH BP

Question 40

What does renin do?

Answer 40

Enzyme which acts to convert angiotensinogen (released by liver) into angiotensin 1

Question 41

Where is angiotensinogen released from?

Answer 41

Liver

Question 42

What does angiotensin 1 convert to?

Answer 42

Angiotensin 2 in the lungs with the help of angiotensin converting enzyme (ACE)

Question 43

What does angiotensin cause?

Answer 43

Vasoconstriction by acting on blood vessels, resulting in increased Blood pressure

Question 44

What does angiotensin 2 also stimulate release of?

Answer 44

Aldosterone from the adrenal glands

Question 45

Mineralocorticoid steroid hormone acts on?

Answer 45

Nephrons in kidneys

Question 46

What is the role of mineralocorticoids?

Answer 46

- Increase Na reabsorption from distal tubule - Increase K secretion from distal tubule - Increase H secretion from collecting ducts

Question 47

What happens when Na is reabsorbed in the kidneys?

Answer 47

Water follows it by osmosis, leading to increase intravascular volume & subsequently BP