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HUBS191 > Thyroid, Parathyroid and Adrenal Glands > Flashcards

Thyroid, Parathyroid and Adrenal Glands Flashcards

1
Q

What is the shape of the thyroid gland?

A

Somewhat butterfly like

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2
Q

What is the location of the thyroid?

A

Just below the larynx wrapped around the anterior and lateral surfaces of the trachea

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3
Q

What are the hormones made and secreted by the thyroid gland?

A

Thyroid hormone and calcitonin

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4
Q

What is the thyroid hormone important for?

A

Optimal metabolic rate

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5
Q

What is calcitonin important for?

A

Calcium homeostasis

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6
Q

What is the thyroid gland composed of?

A

Small spherical sacs called follicles

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7
Q

What are follicles surrounded by?

A

Follicular cells (simple cuboid epithelial cells) which is the site of thyroid hormone synthesis

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8
Q

What is found between follicles?

A

Clear cells/c cells which lie in clusters and make the hormone calcitonin

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9
Q

What is made in the thyroid follicles?

A

Thyroglobin (TGB) protein

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10
Q

What reacts with TGB?

A

Iodine which enters the follicle cell from the blood

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11
Q

What do thyroid hormones detach from?

A

Iodised TGB as needed

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12
Q

What are the two forms of thyroid hormone?

A

T3 and T4

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13
Q

What is the active form of thyroid hormone?

A

T3

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14
Q

What is the predominant form of thyroid hormone?

A

T4 but this can be converted into T3

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15
Q

What do T3 and T4 do?

A

Travel bound to a carrier protein (thyroid binding globulin, TBG) to target cells

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16
Q

What is iodine needed for?

A

It must be a part of our diet as it is required for the production of thyroid hormone

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17
Q

What is the storage of thyroid hormone?

A

It is made in abundance and stored until required

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18
Q

How does thyroid hormone travel?

A

Bound to a carrier protein

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19
Q

What does the thyroid hormone do once it reaches the target cell?

A

Detaches from the carrier protein and enters the target cell

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20
Q

What happens once the thyroid hormone is in the cell?

A

T3 binds to the T3 receptor in the nucleus (receptor is already bound to a specific DNA site)

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21
Q

What happens once T3 binds to the T3 receptor in the nucleus?

A

Specific genes are activated to transcribe mRNA

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22
Q

What happens once specific genes are activated to transcribe mRNA?

A

mRNA translation occurs in the cytoplasm and specific proteins are synthesised (e.g. sodium -potassium pump)

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23
Q

What is the response time of the thyroid hormone?

A

45 minutes to days

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24
Q

What is the stimulus for thyroid hormone release?

A

External and internal stimuli lead to CNS input to hypothalamus

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25
Q

What does the input at the hypothalamus cause (thyroid hormone)?

A

Release of thyrotropin releasing hormone (TRH) into the blood

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26
Q

What does thyrotropin releasing hormone do?

A

Cause release of thyroid stimulating hormone (TSH) from the anterior pituitary into the blood

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27
Q

What does thyroid stimulating hormone do?

A

Cause release of thyroid hormones T3 and T4 from the thyroid gland into the blood

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28
Q

What is the effect of thyroid hormones T3 and T4 on the metabolism?

A

Increasing basal metabolic rate by increasing the synthesis and activity of sodium potassium pump

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29
Q

What are the other effects of thyroid hormones T3 and T4?

A

Stimulates growth (fetes and early childhood) and nervous system (alertness and reflexes)

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30
Q

What does the thyroid hormone negatively effect?

A

The production of TRH and TSH in the hypothalamus and anterior pituitary

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31
Q

What is basal metabolic rate?

A

The body’s rate of energy expenditure under basal conditions

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32
Q

What are basal conditions?

A

Person is awake, at physical and mental rest, lying down, no muscle movement, at a comfortable temperature and fasted (12-18hours)

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33
Q

What are the trends in metabolic rate related to age?

A

Basal metabolic rate decreases as age increases (require less energy)

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34
Q

What are the trends in metabolic rate related to puberty?

A

From puberty onwards males tend to have a higher metabolic rate than females

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35
Q

What is the thyroid hormone required for?

A

Normal growth, alertness and metabolism

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36
Q

How does the thyroid hormone effect metabolism?

A

Increases body heat production, stimulates fatty acid oxidation (usage of stored fat) in many tissues, Increases proteolysis and effects glucose

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37
Q

How does the thyroid hormone increase body heat production?

A

Increase oxygen consumption and ATP hydrolysis

38
Q

What is proteolysis and where does it occur?

A

The breakdown of proteins which occurs predominantly in muscle

39
Q

What effects does thyroid hormone have on glucose?

A

Stimulates carbohydrate metabolism (usage of stored glucose), enhances insulin-dependent entry of glucose into cells, increases gluconeogenesis and glycogenolysis

40
Q

What is the overall effect of the thyroid hormone on blood glucose concentration?

A

Does not cause a significant increase in blood glucose as there is a balanced increase in production and uptake by cells

41
Q

How much calcium comes from the diet?

A

1000 mg a day

42
Q

What happens with the consumed calcium?

A

It goes into the digestive tract and some is absorbed into the blood but 350 mg a day is lost in faeces

43
Q

What happens to the calcium in the blood?

A

The kidneys filter the blood, some is lost in urine (650mg/day) while some is reabsorbed into the blood

44
Q

Where other than the diet can calcium also come from?

A

Bones and it can also be laid down by bones

45
Q

What is the overall goal with regards to calcium?

A

Input be equal to output so that the blood calcium concentration is maintained between 8.5 and 11 mg/dL

46
Q

What is calcium essential for?

A

Many physiological functions such as contraction of muscles and release of neurotransmitters

47
Q

What is the major store of calcium?

A

Bone. Immediate adjustments can be made by rapid exchanges of calcium between bone and the blood

48
Q

What does a balance exist between?

A

The constant build up and break down of bone

49
Q

How many hormones are involved in calcium regulation?

A

3

50
Q

What hormones are involved in calcium regulation?

A

Parathyroid hormone (PTH), calcitriol and calcitonin

51
Q

How many parathyroid glands are there?

A

4

52
Q

Where are the parathyroid glands found?

A

On the posterior aspect of the thyroid gland

53
Q

What does the parathyroid gland secrete?

A

Parathyroid hormone which is essential for life

54
Q

What is the stimulus for the parathyroid hormone?

A

Decrease blood calcium concentration

55
Q

What happens when the blood calcium concentration decreases?

A

Parathyroid gland secretes parathyroid hormone

56
Q

What does the parathyroid hormone effect?

A

Kidneys and bone

57
Q

What does parathyroid hormone do to the kidneys?

A

Increase calcium reabsorption into the blood and conversion of vitamin D to calcitriol

58
Q

What effect does increasing calcium reabsorption have?

A

Decreases urinary excretion of calcium

59
Q

What effect does calcitriol have?

A

Increased calcium absorption from food in the intestine

60
Q

What is the effect of the parathyroid hormone on bone?

A

Increase bone breakdown which increases release of calcium into the blood

61
Q

What is the overall effect of the parathyroid hormone?

A

Increasing blood calcium concentration which restores blood calcium towards normal

62
Q

How does the parathyroid hormone show negative feedback?

A

The response decreases the stimulus which means less parathyroid hormone will be secreted

63
Q

What does calcitonin do?

A

Amplifies the effect of parathyroid hormone so it has a negative effect on the production of more calcitriol and makes sure the blood calcium concentration doesn’t get too high?

64
Q

What doesn’t control the calcium regulation pathway?

A

The hypothalamus

65
Q

How is calcitonin found?

A

It is rarely produced naturally but can be delivered a s medication in humans

66
Q

What colour is the cortex of adrenal glands?

A

Yellow

67
Q

What colour is the medulla of adrenal glands?

A

Red or grey

68
Q

Where are the adrenal glands found?

A

Superior to each kidney

69
Q

What is the adrenal gland made up of?

A

Two separate glands

70
Q

What are the two glands the adrenal gland is made up of?

A

Adrenal cortex and adrenal medulla

71
Q

What is the adrenal cortex?

A

The outer region of the adrenal gland which has 3 layers and secretes steroid hormones

72
Q

What hormone does the outer layer of the adrenal cortex secrete?

A

Aldosterone

73
Q

What hormone does the middle layer of the adrenal cortex secrete?

A

Cortisol

74
Q

What hormone does the inner layer of the adrenal cortex secrete?

A

Androgens which have a minor reproductive role

75
Q

What is the adrenal medulla?

A

The central region of the adrenal gland which is part of the sympathetic nervous system and secretes mainly adrenaline

76
Q

What is noradrenaline secreted as part of?

A

The sympathetic nervous system response to stress

77
Q

What does increases adrenaline and noradrenaline from adrenal glands do?

A

Supplements the actions of sympathetic nervous system, particularly in times of stress

78
Q

What type of hormone is adrenaline?

A

A water soluble hormone (catecholamine)

79
Q

What system does adrenaline use?

A

A second messenger system

80
Q

Where is the receptor for adrenaline?

A

Cell membrane

81
Q

What does adrenaline do as a result of the second messenger system?

A

Amplification of the cellular response

82
Q

What is the speed of action of adrenaline?

A

Fast

83
Q

What is the stimulus for adrenaline secretion?

A

Stress

84
Q

What does the hypothalamus stimulate?

A

Sympathetic preganglionic fibres

85
Q

What do sympathetic preganglionic fibres cause?

A

An action potential and acetylcholine binds to the receptor which stimulates the adrenal medulla to secrete adrenaline

86
Q

What does adrenaline do?

A

Travels in the blood to target cells

87
Q

What are the target cells of adrenaline?

A

Skeletal muscle, liver and fat

88
Q

What effect does adrenaline have on the skeletal muscle and liver?

A

Increasing breakdown of glycogen to glucose

89
Q

What effect does adrenaline have on fat cells?

A

Increasing the breakdown of fat to fatty acids

90
Q

What is the overall effect of adrenaline?

A

Makes fuel (glucose and fatty acids) more readily available to cells which increases blood glucose concentration

91
Q

What are some other sympathetic nervous system actions cause by adrenaline?

A

Some systems are activated for physical activity and some systems not crucial doe short term survival are shut down

HUBS191 (29 decks)

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