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Endocrine SOH > Physiology > Flashcards

Physiology Flashcards

1
Q

Communication between glands and other tissues occurs by the secretion of _____ ?

A

Hormones

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2
Q

What is a hormone?

A

A chemical messenger
Signalling molecule produced by endocrine glands
They activate specific receptors

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3
Q

Autocrine hormone

A

Hormone acts on the same cell that produced it

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4
Q

Paracrine hormone

A

Hormone acts on target cells nearby

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5
Q

Endocrine hormone

A

Hormone is distributed in the blood circulation and binds to distant target cells

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6
Q

Hormones involved during short term intense exercise?

A

Adrenaline
Cortisol
Glucagon

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7
Q

Hormones involved during long term for normal growth?

A

GH
Insulin
IGF-1
Sex hormones

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8
Q

What is the function of insulin?

A

Lowers plasma glucose levels and stimulates the uptake of glucose into muscle and adipose tissue where it is stored as glycogen

  • inhibits hepatic glycogenolysis
  • inhibits gluconeogenesis
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9
Q

What is the function of glucagon?

A

Raises plasma glucose levels

  • stimulates hepatic glycogenolysis
  • stimulates gluconeogenesis
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10
Q

Are steroid hormones pre-synthesised or synthesised on demand?

A

Synthesised on demand

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11
Q

What are steroid hormones derived from?

A

Cholesterol

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12
Q

What is the function of carrier proteins?

A

To transport insoluble molecules
They increase the amount of hormones transported in the blood
(eg steroids, T4, T3)

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13
Q

Specific carrier proteins: CBP

A

Binds cortisol in a selective manner

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14
Q

Specific carrier proteins: TBG

A

Binds T4 in a selective manner

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15
Q

Specific carrier proteins: SSBG

A

Binds testosterone and oestradiol

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16
Q

General carrier proteins (2)

A

Albumin

Transthyretin

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17
Q

What is the aim of negative feedback

A

To maintain plasma concentration at a set level

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18
Q

Are hormones secreted at the same rate throughout the day?

A

No

  • there is a diurinal rhythm
  • the secretion rate fluctuates depending on the time of day
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19
Q

Where does hormone elimination occur?

A

Metabolised by the liver

Excreted by the kidney

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20
Q

Name the 3 types of hormone receptor

A

GPCR
Receptor tyrosine kinase
Nuclear receptors

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21
Q

GPCR

A

Dissociation of the G protein complex from the GPCR causes the conversion of GDP -> GTP

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22
Q

Examples of GPCR

A

TSH receptor (thyroid stimulating hormone)

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23
Q

Examples of receptor tyrosine kinase

A

Insulin receptor

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24
Q

Pancreatic islets: function of beta cells?

A

Secrete insulin

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25
Q

Pancreatic islets: function of alpha cells?

A

Secrete glucagon

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26
Q

Pancreatic islets: function of delta cells?

A

Secrete somatostatin

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27
Q

Which energy source are you using when you are running for 4 seconds?

A

ATP

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28
Q

Which energy source are you using when you are running for 15 seconds?

A

Phosphocreatanine

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29
Q

Which energy source are you using when you are running for 4 mins?

A

Free circulating glucose

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30
Q

Which energy source are you using when you are running for 77 mins?

A

Glycogen stores

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31
Q

Which energy source are you using when you are running for 3 days?

A

Fat stores

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32
Q

Cellular structure of the thyroid gland

A

Contains a large follicle
Layer of follicular cells around the follicle
Colloid in the centre

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33
Q

What does the colloid store?

A

Thyroglobulin

Thyroid hormone which is attached to thyroglobulin

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34
Q

What do parafollicular cells secrete?

A

Calcitonin

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35
Q

Synthesis of thyroid hormones

A

Iodine is taken up by follicular cells
Iodine makes its way into the colloid and combines with thyroglobulin tyrosine residues
This forms MIT (monoiodotyrosine) and DIT (diiodotyrosine) and eventually produces thyroid hormones (T3 and T4)

36
Q

2 x DIT = T3 or T4?

A

T4 (thyroxine)

37
Q

(1 x MIT) + (1 x DIT) = T3 or T4?

A

T3 (triiodothyronine)

38
Q

Storage of thyroid hormones

A

In the colloid of the thyroid gland

39
Q

Which substance is required for the synthesis of thyroid hormones?

A

Iodine

40
Q

What happens to thyroid hormone production if the patient is iodine deficient?

A

There is no production of thyroid hormones

41
Q

Thyroxine (T4)

A

The main thyroid hormone

Mainly found bound to plasma proteins

42
Q

Do you measure free (unbound) or bound thyroid hormone levels?

A

Free levels are measured as this is the biologically active form
It is only the free hormones that are available to the tissues

43
Q

Tri-iodothyronine (T3)

A

Produced mainly by the de-ionisation of T4

Mainly found bound to plasma proteins

44
Q

Which thyroid hormone is more potent and why; T3 or T4?

A

T3

- more rapid onset of action

45
Q

Thyroid hormone regulation pathway

A

Hypothalamus releases TRH –>
Stimulates the anterior pituitary gland to release TSH (thyrotropin) –>
thyroid gland releases thyroid hormones (T3, T4)

46
Q

What happens to the thyroid hormone regulation pathway when too much thyroid hormone is produced?

A

Negative feedback occurs

Less TRH is produced, so less TSH, so less thyroid hormones released

47
Q

What happens to the thyroid hormone regulation pathway when not enough thyroid hormone is produced?

A

Positive feedback occurs

More TRH is produced, so more TSH, so more thyroid hormones released

48
Q

Relationship between cold temperatures and thyroid hormone production

A

increased thyroid hormone production

49
Q

Relationship between stress and thyroid hormone production

A

decreased thyroid hormone production

50
Q

Thyroid hormone levels are highest at night - true or false?

A

True

- and lowest at the morning

51
Q

D-iodinase type 1 (D1)

A

Converts T4 -> T3

Found in the liver and kidney

52
Q

D-iodinase type 2 (D2)

A

Converts T4 -> T3 in the tissues

53
Q

D-iodinase type 3 (D3)

A

Found in foetal tissue, placenta, brain

54
Q

What do the 4 parathyroid glands secrete?

A

Para thyroid hormone (PTH)

55
Q

How does TSH allow the release of thyroid hormones?

A

TSH binds to TSH receptor (GPCR) on the surface of thyroid follicular cells. The production of cAMP increases the production of thyroid hormones

56
Q

How do you measure thyroid hormone function?

A

By measuring TSH levels
Normal TSH = normal thyroid function
Increased TSH = Hypothyroid
Decreased TSH = Hyperthyroid

57
Q

Increased TBG levels

A

Increased amount of ‘bound’ thyroid hormone, but less ‘unbound’ thyroid hormone
- therefore there is less thyroid hormone available to the tissues

58
Q

Which type of receptor is the thyroid hormone receptor

A

Nuclear receptor
When T3 is present, mRNA can be produced
When T3 is not present, mRNA cannot be produced

59
Q

Which 2 glands make up the adrenal gland?

A

Cortex (outer layer)

Medulla (inner layer)

60
Q

Adrenal cortex; 3 sub-sections

A

Zona glomerulosa - secretes mineralocorticoids eg aldosterone, controlled by RAS system
Zona fasciculata - secretes glucocorticoids eg cortisol, controlled by anterior pituitary (ACTH)
Zona reticularis - secretes adrenal androgens, controlled by anterior pituitary (ACTH)

61
Q

Adrenal medulla; what does it contain?

A

Contains chromaffin cells, stored and secretes catecholamines (adrenaline, noradrenaline)

62
Q

Where are the adrenal glands located?

A

On top of the kidneys

63
Q

Can hormones secreted from the cortex be stored in the cortex or are they synthesised on demand?

A

Synthesised on demand

64
Q

When is the RAS pathway activated?

A

When there is a decrease in BP

65
Q

What is the RAS system

A

Leads to the release of aldosterone in order to increase BP

66
Q

Hypothalamus-pituitary-adrenal axis

A

Hypothalamus releases CRH –>
anterior pituitary gland releases ACTH –>
Stimulates the adrenal cortex to release cortisol

67
Q

What happens to the hypothalamus-pituitary-adrenal axis when too much cortisol is produced?

A

Negative feedback loop

Hypothalamus releases less CRH, anterior pituitary releases less ACTH, this results in less cortisol release

68
Q

When is the best time to measure cortisol levels?

A

Early morning

- excess cortisol builds up during the night as there is no secretion of cortisol during the night

69
Q

What is cortisol?

A

Stress hormone

Provides a quick source of energy

70
Q

What is prolactin?

A

It acts on breast tissue and when active it allows lactation

71
Q

Which cells secrete prolactin?

A

Lacotroph cells of the anterior pituitary

72
Q

Why is prolactin different from the other anterior pituitary hormones?

A

It is under INHIBITION (instead of stimulation) by dopamine in the hypothalamus

73
Q

Prolactin pathway

A

Hypothalamus releases dopamine –>

this inhibits the anterior pituitary from releasing prolactin

74
Q

What happens in the prolactin pathway when dopamine is not released from the hypothalamus?

A

Anterior pituitary can release prolactin –>

stimulates the mammary glands to lactate

75
Q

What causes raised prolactin levels?

A

Pregnancy, breast feeding
Dopamine antagonists eg metochlopramide
Tumour
Hypothyroidism

76
Q

Growth hormone pathway

A

Hypothalamus releases GHRH –>
Anterior pituitary gland releases GH –>
this stimulates the release of IGF-1 from liver

77
Q

Growth hormone functions

A

Decreases abdominal fat
Increases muscle mass, stamina
Improves cardiac function - decreases cholesterol

78
Q

“trophic” hormones - definition

A

Hormones which act on other endocrine glands

79
Q

Hormones in the posterior pituitary gland? (2)

A

Oxytocin
Vasopressin (ADH)
- produced in the hypothalamus
- stored in the posterior pituitary gland

80
Q

What investigations do you use to assess posterior pituitary gland function?

A

U&E’s

Plasma/urine osmolality

81
Q

Dynamic pituitary function tests - suppression test

A

Carried out if the patient is producing too much hormone in order to try and suppress the hormone production
- hormone level should come down following the suppression test

82
Q

What is implied if the hormone suppression test doesn’t work?

A

Suggests there is a tumour which is producing too much hormone

83
Q

Dynamic pituitary function tests - stimulation test

A

Carried out if the patient isn’t producing enough hormone in order to try and stimulate the hormone production
- hormone level should increase following the stimulation test

84
Q

Examples of hormone stimulation tests

A

Synacthen test

85
Q

What is the synacthen test

A

Synthetic ACTH is given to the adrenal gland to see if there is normal secretion of cortisol

86
Q

What happens to the thyroid gland during pregnancy?

A

It expands which results in increased thyroid hormone production

Endocrine SOH (25 decks)

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