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Endocrine 0 to Finals > Hormonal Axis Physiology > Flashcards

Hormonal Axis Physiology Flashcards

1
Q

Where does the hypothalamus sit?

A

Above the pituitary gland

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2
Q

What does the anterior pituitary gland secrete?

A
  • Thyroid stimulating hormone (TSH)
  • Adrenocorticotropic hormone (ACTH)
  • Follicle stimulating hormone (FSH) & Luteinising hormone (LH)
  • Growth hormone (GH)
  • Prolactin
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3
Q

What does the posterior pituitary gland secrete?

A
  • Oxytocin (vasopressin)

- Antidiuretic hormone (ADH)

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4
Q

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

A

Thyrotropin releasing hormone (TRH)

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5
Q

What does TRH stimulate?

A

The anterior pituitary to release thyroid stimulating hormone (TSH)

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6
Q

What does TSH do?

A

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

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7
Q

Summary of the thyroid hormonal Axis?

A

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

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8
Q

What organs sense T3 and T4?

A

Sensed by hypothalamus and anterior pituitary

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9
Q

What is the role of T3 and T4 ?

A

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

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10
Q

What does suppressing TRH and TSH result in?

A

Lower amounts of T3 and T4

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11
Q

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

A

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

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12
Q

The level of thyroid hormone is regulated by?

A

Negative feedback

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13
Q

What secretes cortisol?

A

2 Adrenal glands which sit above the kidneys

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14
Q

What is release of cortisol controlled by?

A

Hypothalamus

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15
Q

What is a trigger for cortisol release?

A

Stress

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16
Q

Cortisol is released in a _______ variation?

A

Diurnal variation

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17
Q

What does diurnal variation mean?

A

Increase and decrease at different times of day

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18
Q

When is the cortisol at peak?

A

Early morning (triggers wake up)

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19
Q

When is cortisol low?

A

Late night- triggers sleep

20
Q

What does the hypothalamus release in the adrenal axis?

A

Corticotrophin release hormone (CRH)

21
Q

What does CRH stimulate the release of?

A

Anterior pituitary to release adrenocorticotrophic hormone (ACTH)

22
Q

What does ACTH stimulate the release of?

A

Cortisol from the adrenal gland

23
Q

The series of hormone stimulation on the adrenal hormone axis?

A

CRH > ACTH > Cortisol

24
Q

What is cortisol sensed by?

A

Hypothalamus and anterior pituitary

25
Q

What does cortisol do to hormones?

A

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

26
Q

Actions of cortisol?

A
  • Inhibits immune system
  • Inhibits bone formation
  • Increases metabolism
  • Raises blood glucose
  • Increases alertness
27
Q

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

A

Hypothalamus

28
Q

What does GHRH stimulate?

A

Growth hormone release from anterior pituitary

29
Q

What does GH stimulate?

A

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

30
Q

Where releases IGF-1?

A

Liver

31
Q

Functions of growth hormone?

A
  • Stimulates muscle growth
  • Increases bone density
  • Stimulates cell regeneration & reproduction
  • Stimulates growth of internal organs
32
Q

What releases parathyroid hormone (PTH)?

A

4 parathyroid glands

33
Q

What triggers PTH release?

A

Low serum calcium and low Mg and high serum phosphate

34
Q

What does PTH do?

A
  • 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

35
Q

3 effects of PTH?

A
  • Increased calcium absorption from bone
  • Increase calcium absorption from kidneys
  • Increase calcium absorption from small intestine
36
Q

What do the effects of PTH overall do?

A

Help to raise level of serum calcium

37
Q

What happens when serum calcium is high?

A

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

38
Q

Where is renin secreted from?

A

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

39
Q

What do juxtaglomerular cells do?

A

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

40
Q

What does renin do?

A

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

41
Q

Where is angiotensinogen released from?

A

Liver

42
Q

What does angiotensin 1 convert to?

A

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

43
Q

What does angiotensin cause?

A

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

44
Q

What does angiotensin 2 also stimulate release of?

A

Aldosterone from the adrenal glands

45
Q

Mineralocorticoid steroid hormone acts on?

A

Nephrons in kidneys

46
Q

What is the role of mineralocorticoids?

A
  • Increase Na reabsorption from distal tubule
  • Increase K secretion from distal tubule
  • Increase H secretion from collecting ducts
47
Q

What happens when Na is reabsorbed in the kidneys?

A

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

Endocrine 0 to Finals (14 decks)

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