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Endocrine Physiology > Introduction to Endocrine > Flashcards

Introduction to Endocrine Flashcards

1
Q

Definition of endocrine system

A

A system that integrates and controls organ function via the secretion of chemicals (hormones) from tissues or glands, which are then carried in the blood to the target organs distal from the site of the hormone synthesis where they influence the activity of the target organ

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2
Q

What do hormones cause in the target organ?

A

A change in activity

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3
Q

Different types of chemicals in the body

A

Paracrine chemicals
Endocrine chemicals
Autocrine chemicals
Exocrine chemicals

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4
Q

Where do paracrine chemicals act?

A

Local to the site of synthesis, do not travel to distant sites

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5
Q

Example of a paracrine chemical

A

Histamine

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6
Q

Where do exocrine chemicals act?

A

Released from exocrine glands via ducts to the external environment including the GI tract e.g. saliva, sweat, bile

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7
Q

Where do autocrine chemicals act?

A

Act on/in the same cell that synthesises the hormone

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8
Q

Example of an autocrine chemical

A

Cytokine

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9
Q

How do tissues detect hormones?

A

Through the presence of specific receptors for that chemical on/in the cells.

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10
Q

Where can receptors be for the hormones?

A

Either outside the cell or within the cell

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11
Q

What are neurotransmitters released from?

A

Presynaptic neurones

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12
Q

Where do neurotransmitters travel?

A

From presynaptic neurones
across the synaptic cleft
To postsynaptic cell to influence its activity

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13
Q

Where do neurotransmitters act?

A

Locally within the synaptic cleft

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14
Q

What two systems co-operate intimately to provide further control particularly for long term phenomena e.g. growth?

A

Endocrine and nervous systems

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15
Q

When the endocrine and neuro systems combine, what occurs?

A

Nerves release hormones which enter the blood and travel to their target cells (distal site)

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16
Q

Example of a neuroendocrine system

A

Hypothalamic posterior pituitary axis

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17
Q

Example of a neuroendocrine hormone

A

Adrenaline

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18
Q

Function of hormones / Neurotransmitters

A

Bring about changes in the activity of their target cells and tissues (increase or decrease in a particular activity)

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19
Q

What does the pineal gland produce?

A

Melatonin

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20
Q

What does the hypothalamus produce?

A

Trophic hormones

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21
Q

What is the primary target of trophic hormones?

A

Anterior pituitary

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22
Q

What does the posterior pituitary produce?

A

Oxytocin

Vasopressin (ADH)

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23
Q

What does the anterior pituitary produce?

A 
Prolactin 
Growth hormone
Corticotrophin (ACTH)
Thyrotropin 
FSH
LH
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24
Q

What is another name for growth hormone?

A

Somatotropin

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25
Q

What does the thyroid gland produce?

A

Triiodothyronine
Thyroxine
Calcitonin

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26
Q

What does the parathyroid gland produce?

A

Parathyroid hormone

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27
Q

What does the thymus gland produce?

A

Thymosin

Thymopoietin

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28
Q

What hormone does the heart produce?

A

ANP

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29
Q

Function of ANP

A

increases Na excretion

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30
Q

What hormones does the liver produce?

A

Angiotensinogen

Insulin-like growth factors

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31
Q

What hormones does the pancreas produce?

A

Insulin
Glucagon
Somatostatin
Pancreatic polypeptide

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32
Q

What does the adrenal cortex produce?

A

Aldosterone
Cortisol
Androgens

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33
Q

What does the adrenal medulla produce?

A

Epinephrine / norepinephrine

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34
Q

What hormones do the kidneys produce?

A

Erythropoietin

1,25-Dihydroxy-vitamin D3 (calciferol)

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35
Q

What hormone does the skin produce?

A

Vitamin D3

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36
Q

What hormones do the testis produce?

A

Androgens

Inhibin

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37
Q

What hormones do the ovaries produce?

A

oestrogen
progesterone
inhibin
Relaxin (pregnancy)

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38
Q

How much endocrine hormone is needed to bring about a response?

A

Endocrine hormones exert their effects at very low concentrations because the receptors have a very high affinity for the hormone and therefore do not need a lot of hormone to bring about a response

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39
Q

How do endocrine hormones often have their actions terminated?

A

Via negative feedback loops

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40
Q

Where do endocrine hormones get metabolised?

A

Liver

Kidneys

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41
Q

What Is the release of endocrine hormones controlled by?

A

Negative feedback loops

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42
Q

Types of endocrine hormones

A

Peptide/protein hormones
Steroid hormones
Amine hormones

43
Q

Different structures of peptide/protein hormones

A

Composed of chains of amino acids
Can be very short e.g. 3 amino acids long (TRH)
Can be very long e.g. FSH

44
Q

What are all steroid hormones derived from?

A

Cholesterol

45
Q

Examples of steroid hormones

A

Oestrogen

Progesterone

46
Q

What are amine hormones derived from?

A

One of two amino acids - either

  • Tryptophan
  • Tyrosine
47
Q

What is the only amine hormone is derived from tryptophan?

A

Melatonin

48
Q

What amine hormones are derived from tyrosine?

A

All other amine hormones apart from melatonin

49
Q

Examples of peptide hormones

A

TRH
FSH
Insulin

50
Q

When are peptide hormones synthesised?

A

In advance of need

51
Q

Where are peptide hormones stored and until when?

A

Vesicles until required

52
Q

What is the initial protein of peptide hormones called and what is it produced by?

A

Preprohormone

Produced by ribosomes

53
Q

Features of the preprohormone

A

Large and inactive so no endocrine function in that form

54
Q

Where are preprohormones cleaved and what are they cleaved into?

A

In the RER

Into small but still inactive proteins called prohormones

55
Q

What happens to prohormones?

A

Packaged into vesicles in the Golgi apparatus, along with proteolytic enzymes

56
Q

What do the proteolytic enzymes stored with the prohormones do?

A

Break the prohormone down into active hormone and other fragments

57
Q

Hormones and fragments after the breakdown of prohormones are stored where and until when?

A

Stored in vesicles in the endocrine cells

Until release is triggered where all vesicle contents are released into the plasma

58
Q

What is the release of all vesicle contents (inactive and active fragments) called?

A

Co-secretion

59
Q

How can inactive fragments in the plasma be useful clinically and how? Then give an example

A

They can be measured
They tend not to be metabolised as quickly as hormones and so can be detected clinically
C peptide in diabetes

60
Q

What is C peptide?

A

The inactive fragment cleaved from the insulin prohormone

61
Q

What does C peptide measurement indicate?

A

Endogenous insulin production from the pancreas (produced in equal amounts)

62
Q

C peptide levels compared to insulin levels and why

A

C peptide levels are approx. 5x higher than endogenous insulin release levels
Because insulin is metabolised faster

63
Q

Solubility of peptide hormones

A

Water soluble

64
Q

Where can water soluble hormones move?

A

Dissolve easily in plasma so transport via the blood is simple and easy
Cannot cross cell membrane

65
Q

Where are the hormone receptors for peptide hormones?

A

Membrane bound receptors on outside of cells

66
Q

Speed of peptide hormone reactions once bound to the receptors

A

Fast (secs - mins)

67
Q

Peptide hormone pathways

A

GPCR (G-protein coupled receptors) signalling pathway

Tyrosine kinase linked signalling pathway

68
Q

Other names for hormones being water soluble

A

Hydrophilic

Lipophobic

69
Q

How does a peptide hormone activating a G protein coupled receptor work?

A

2nd messenger system activation and / or ion channels
Modification of existing protein
Rapid response

70
Q

How does a peptide hormone activating a tyrosine kinase linked receptor work?

A

Alters gene expression

Slower, longer lasting activity

71
Q

What may 2nd messengers also do in peptide hormone reactions?

A

Alter gene expression

72
Q

When are steroid hormones synthesised?

A

Directly as needed

73
Q

Solubility of steroid hormones and what this means for their storage

A

Highly lipophilic / lipid soluble

So cannot be retained within lipid membranes and so cannot be stored

74
Q

How are steroid hormones transported in the blood?

A

Bound to carrier proteins such as albumin

75
Q

Function of carrier proteins transporting steroid hormones

A

Stabilises their transport through the plasma

Protects them from metabolic enzymatic degradation - massively increasing their half life

76
Q

Examples of steroid hormones and what they are produced by..

A

Gonads - sex steroids
Placenta - hCG, sex steroids
Kidneys - vitamin D3
Adrenal cortex - corticosteriods

77
Q

How is which specific steroid hormone is derived from cholesterol determined?

A

By different cells having different enzymes synthesising different derivatives of cholesterol

78
Q

Where are receptors for steroid hormones found?

A

Inside cells (cytoplasmic or nuclear receptors)

79
Q

What do steroid hormones do once bound to receptors and what is this called?

A

Triggers either activation or repression (inhibition) of gene function within the nucleus
Genes control the synthesis of proteins so these hormones either increase of decrease protein synthesis
This is called the genomic effect

80
Q

What does the relatively slow process of steroid hormones cause?

A

A lag time between hormone release and biological effect (hours to days) but the effect persists for around the same time

81
Q

Examples of amine hormones

A

Dopamine
Norepinephrine
Epinephrine

82
Q

Where is dopamine released from?

A

The brain

83
Q

Where is norepinephrine released from?

A

Neurones

84
Q

Where is epinephrine released from?

A

The adrenal medulla

85
Q

Function of melatonin

A

Regulates circadian rhythm

86
Q

What is the only amine hormone not derived from tyrosine and what is it derived from?

A

Melatonin - derived from tryptophan

87
Q

Two types of amine hormones derived from tyrosine

A

Catecholamines

Thyroid hormones

88
Q

Mechanism of action of catecholamines

A

Similar mechanism to peptide hormones as they are HYDROPHILIC

89
Q

Mechanism of action of thyroid hormones

A

Similar mechanism to steroid hormones as they are LIPOPHILIC

90
Q

What is the physiologically important fraction of steroid/thyroid hormones in the plasma? Why?

A

The small amount of unbound free steroid/thyroid hormone

Because only free hormone can diffuse across capillary walls to target cells (lipophilic)

91
Q

What is the free hormone : hormone-protein complex ratio of steroid hormones much in favour of?

A

Bound hormone

92
Q

What is an important fact of the level of free (active) hormone of the lipophilic hormones in the plasma?

A

The levels remain constant

93
Q

What does the Law of Mass Action dictate?

A

As free hormone leaves the plasma (taken up by cells) more hormone is released from the carriers

94
Q

Equation for total plasma hormone in lipophilic hormones

A

Total plasma (hormone) = free hormone + complexed hormone

95
Q

Types of carrier protein in the plasma for steroid/thyroid hormones

A

Specific = corticosteriod binding globulin

Non specific = albumin

96
Q

What does the reservoir of steroid in the plasma result in?

A

Prolonged effect

97
Q

What does the concentration of hormone in the blood depend on?

A

Rate of secretion

Rate of removal

98
Q

How are hormones removed and where does this occur?

A

Excretion or metabolic transformation

Mainly occurs in liver and kidneys

99
Q

Which types of hormones are excreted quickly and easily due to their short half life? (mins - hours)

A

Catecholamines

Peptide hormones

100
Q

Which types of hormones take hours and days to excrete or metabolise and why is this?

A

Steroid hormones
Thyroid hormones
Because they are protein bound

101
Q

What happens to the target cells after prolonged exposure to a low hormone concentration in the plasma?

A

Up regulation

= increase in no. of hormone receptors on the target tissues

102
Q

What happens to the target cells after prolonged exposure to high concentration of the hormone in the plasma?

A

Down regulation

= decrease in the receptor number on target tissues

103
Q

Definition of permissive effects

A

The presence of one hormone enhances the effects of another

104
Q

Definition of half life

A

Time taken for the plasma concentration to fall by one half

Endocrine Physiology (8 decks)

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