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HUBS191 > lecture 27 - thyroid, parathyroid & adrenal galnds > Flashcards

lecture 27 - thyroid, parathyroid & adrenal galnds Flashcards

1
Q

What hormones are secreted by the thyroid gland?

A

Thyroid hormone (T3, T4) and calcitonin

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2
Q

What is the location of the thyroid gland?

A

On anterior and lateral surfaces of the trachea, inferior to the larynx

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3
Q

What is the structure of the thyroid gland?

A

Composed of small spherical sacs (follicles) surrounded by follicular cells. Clear/C cells lie in clusters between follicles

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4
Q

What is the function of the follicular cells of the thyroid?

A

Synthesis and storage of thyroid hormones

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5
Q

Where is the hormone calcitonin made?

A

In the Clear/C cells of the thyroid gland.

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6
Q

What type of cell are follicular cells?

A

Epithelial cells

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7
Q

What type of hormone are thyroid hormones?

A

Lipid-soluble hormones

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8
Q

How are thyroid hormones T3 and T4 made?

A

Iodine enters follicular cells and forms complexes with tyrosine from thyroglobulin proteins (TGB) made in the thyroid follicles.

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9
Q

What is the structure of T3 hormone?

A

3 iodine (I) surrounding a tyrosine (Y)

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10
Q

What is the structure of a T4 hormone?

A

4 iodine (I) surrounding a tyrosine (Y)

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11
Q

How are thyroid hormones stored, despite being lipid soluble?

A

T3 and T4 are bound to thyroglobulin (TGB) in follicle cells until they need to be released, when they detach.

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12
Q

What is the active thyroid hormone?

A

T3

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13
Q

What is the more plentiful thyroid hormone?

A

T4

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14
Q

How do T3 and T4 travel via the bloodstream to target cells?

A

Bound to carrier proteins called thyroid-binding globulin (TBG)

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15
Q

What does TGB stand for?

A

Thyroglobulin

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16
Q

What does TBG stand for?

A

thyroid-binding globulin

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17
Q

What are the basic steps of thyroid hormone target cell activation?

A

Hormone travels bound to carrier protein to cell, diffuses across membrane, T3 binds to T3 receptor on mitochondria or in nucleus, complex binds to DNA and genes are activated, transcripted and translated to produce specific proteins.

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18
Q

What is a common protein produced in target cells in response to activation by T3 thyroid hormone?

A

Sodium-potassium pump

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19
Q

What is the response time of target cells to thyroid hormone?

A

4 minutes to several days

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20
Q

What is thyroid hormone required for?

A

Growth, alertness and metabolism

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21
Q

What are the effects of thyroid hormone on metabolism?

A

increased: body heat production, fatty acid oxidation, proteolysis, carbohydrate metabolism.

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22
Q

How does thyroid hormone increase body heat production?

A

Increases the consumption of oxygen, and ATP hydrolysis

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23
Q

What is fatty acid oxidation, in terms of metabolism?

A

Use of stored fat in many tissues

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24
Q

What is proteolysis, in terms of metabolism?

A

Breaking down proteins into amino acids by proteolytic enzymes, predominantly in muscle

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25
Q

Does thyroid hormone increase or decrease blood sugar concentration?

A

Neither - the glucose released by carbohydrate metabolism is used straight away by cells which have advanced uptake.

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26
Q

What two processes, involving glucose, are increased by the thyroid hormone?

A

Gluconeogenesis (synthesis of glucose from non-carbohydrates) and glycogenolysis (breakdown of glycogen into glucose)

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27
Q

How does thyroid hormone affect the entry of glucose into cells?

A

It enhances insulin-dependent entry of glucose into cells.

28
Q

Does the thyroid hormone increase or decrease the basal metabolic rate?

A

Increase

29
Q

How does the thyroid hormone, using a protein, increase metabolism?

A

By increasing the synthesis and transport activity of Na+/K+ pumps.

30
Q

How does basal metabolic rate change as we age?

A

Decreases with age

31
Q

Do males or females have a higher metabolic rate?

A

Males

32
Q

What is the major store of calcium within the body?

A

Bone

33
Q

How are immediate adjustments of blood calcium levels made?

A

By exchanging calcium between blood and bone

34
Q

What are the hormones involved in maintain blood calcium homeostasis?

A

Parathyroid hormone (PTH), calcitrol, calcitonin

35
Q

Where are the parathyroid glands located?

A

Posterior to the thyroid gland, in the neck

36
Q

How many parathyroid glands are there in the body?

A

4 (2 pairs)

37
Q

What effect does parathyroid hormone (PTH) have on the kidneys?

A

Increases calcium reabsorption, converts vitamin D to calcitrol.

38
Q

What is the result of increased calcium reabsorption by the kidneys as a result of PTH?

A

Decreased urinary excretion of calcium

39
Q

What is the result of increased calcitriol production in the kidneys as a result of PTH stimulation?

A

Increased intestinal absorption of calcium from food in the digestive tract

40
Q

What effect does parathyroid hormone have on bone?

A

It increases bone breakdown (osteoclast activity)

41
Q

What is the result of increased bone breakdown due to parathyroid hormone stimulation?

A

Calcium is released from bone into the blood stream.

42
Q

Decreased plasma [Ca2+] would lead to?

A

Increased PTH release

43
Q

Increased plasma [Ca2+] would lead to?

A

Decreased PTH release

44
Q

What is the location of the adrenal glands?

A

On the superior surface of the kidneys

45
Q

How many adrenal glands are there?

A

2 - one on each kidney

46
Q

What are the two glands of the adrenal gland?

A

Adrenal cortex & adrenal medulla

47
Q

What is the outer region of the adrenal glands?

A

Adrenal cortex

48
Q

How many layers make up the adrenal cortex?

A

3

49
Q

What does the outermost layer of the adrenal cortex release?

A

Aldosterone

50
Q

What is the function of aldosterone?

A

Maintains sodium homeostasis

51
Q

What hormone is secreted by the middle layer of the adrenal cortex?

A

Cortisol

52
Q

What does the inner layer of the adrenal cortex secrete?

A

Androgens

53
Q

What is the function of androgens?

A

They have a minor reproductive role

54
Q

What is secreted by the adrenal medulla?

A

Adrenaline

55
Q

What body system is the adrenal medulla involved with (aside from endocrine)?

A

Sympathetic nervous system.

56
Q

What is adrenaline primarily released in response to?

A

Stress

57
Q

Is adrenaline water soluble or peptide soluble?

A

Water soluble - it is an amino acid derivative

58
Q

What ratios of adrenaline and noradrenaline are released by adrenal medulla secretory cells?

A

80% adrenaline, 20% noradrenaline

59
Q

What two pathways are used by sympathetic pre ganglionic fibres to stimulate adrenaline release to effector cells?

A

Fibre either stimulates adrenal medulla cells to secrete adrenaline and noradrenaline, or uses sympathetic postganglionic fibres to rapidly transmit neurotransmitters adrenaline and noradrenaline with ACh at the synapse at the sympathetic chain ganglion.

60
Q

What type of receptors does adrenaline bind to?

A

Membrane receptors

61
Q

Is adrenaline signalling fast or slow, compared to other hormones?

A

Fast

62
Q

What is the overall effect of adrenaline?

A

Make fuel (glucose and fatty acids) more readily available to cells in response to stress.

63
Q

What systems shut down in response to adrenaline aided activation of the sympathetic nervous system?

A

Systems not crucial for short term survival.

64
Q

How is adrenaline released by the adrenal medulla?

A

Acetylcholine from sympathetic pathways bind to receptors, triggering the secretion of adrenaline by the adrenal medulla.

65
Q

What tissues does adrenaline have a metabolic effect on?

A

Skeletal muscle, liver, fat

66
Q

What are the metabolic effects of adrenaline on skeletal muscle and the liver?

A

Increased breakdown of glycogen to glucose (glycogenolysis)

67
Q

What are the metabolic effects of adrenaline on fat?

A

Breakdown of fat to fatty acids

HUBS191 (36 decks)

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