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ZA - Endocrine System > Introduction to the Endocrine System > Flashcards

Introduction to the Endocrine System Flashcards

1
Q

Is the endocrine system anatomically continuous?

A

No

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2
Q

Give an example of fast and slow endocrine responses.

A

Fast - Increase in HR due to adrenaline

Slow - Increase in protein synthesis die to Growth Hormone

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3
Q

Give some sites of principle endocrine glands.

A 
Hypothalamus
Pituitary
Thyroid
Parathyroid
Adrenal glands

Renal medulla, renal cortex and in the kidney’s themselves
GI tract
Ovary and testes

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4
Q

What are the features of an endocrine hormone?

A

Produced by a cell/group of cells where is secretes into the blood where it is transported to different targets by binding to target receptors

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5
Q

Do endocrine hormones exert effects at high or low concentrations?

A

Low - range if 10^-9M to 10^-12M

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6
Q

What often terminates the endocrine hormones actions?

A

Neg. feedback loops

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7
Q

What are some other chemicals that endocrine hormones should NOT be confused with?

A

Paracrine

Autocrine

Exocrine

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8
Q

What do paracrine hormones/chemicals do? Give an example of one.

A

They act local to the site of synthesis rather than travel to distal sites like endocrine does

Histamine

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9
Q

What do autocrine hormones do?

Example?

A

They act in/on the same cell that synthesised it

Cytokines

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10
Q

What do exocrine chems do?

Example?

A

Released from exocrine glands via ducts to the external environment (including the GI tract as it is classed as external)

Saliva
Sweat
Bile

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11
Q

What does the endocrine system do in conjunction with the nervous system?

A

Communicates with and controls all body functions

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12
Q

What is the difference between an endocrine hormone and a neurotransmitter?

A

A neurotransmitter acts on the post-synaptic cell to influence its activity but this act is local and not distal

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13
Q

What is a neuroendocrine system?

A

NS and endocrine combines - nerves rleases hormones which enter blood and travel to target cells

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14
Q

Example of a neuroendocrine system?

A

Hypothalamus -posterior pituitary axis

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15
Q

How specific is the response of the target cell to hormones?

A

Very - if the target cell doesn’t have the right receptor, hormones won’t act on it

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16
Q

Can hormones act on different cells with different effects?

A

Yes

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17
Q

Example of a hormone acting on different cells with different effects?

A

Insulin acts on skeletal muscle/adipose tissue to increase glucose uptake

But acts on liver to increase glycogenesis (make glycogen) and decrease gluconeogenesis

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18
Q

What is gluconeogenesis?

A

Synthesising glucose from non-carb substrates like amino-acids

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19
Q

What is glycogenolysis?

A

Breaking down glycogen to form glucose

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20
Q

What are the 3 types of hormone?

A

Peptide
Steroid
Amine

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21
Q

Give examples of a peptide hormone?

A

Insulin
Thyrotropin-releasing hormone
Follicle stimulating hormone

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22
Q

What makes up a peptide hormone?

A

Amino acids

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23
Q

Which type of hormone is most common?

A

Peptide

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24
Q

Describe the sysnthesis of a peptide hormone.

A

An inactive preprohormone is made by ribosomes

Preprohormones have 1 or more copies of the active hormone in the structure, it is then cleaves by the rough ER into a prohormone(s) and is still inactive

Prohormones are then packed into vesicles in the golgi apparatus along with proteolytic enzymes that break the prohormone down into an active hormone and other fragments

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25
Q

Once the preprohormone becomes the hormone, what happens?

A

The hormone and fragments are stored in vesicles til needed - when needed entire vesicle contents emptied into blood

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26
Q

What clinical relevance do the fragments have?

A

Measuring the inactive fragments in plasma is useful to get the exact amount of hormone the body is making

Example - for diabetics who take insulin, measuring insulin in blood is not an accurate way of determining how much insulin the body make, but measuring the fragments - C-peptide - is an accurate way

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27
Q

Is there a 1:1 ratio between c-peptide and synthesised insulin?

A

No since insulin is metabolised faster it is actually 5x higher than c-pep

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28
Q

When the preprohormone become a prohormone - what is the part that is cleaved off called and what is it’s job?

A

Called a signal sequence - it directs the chain to the endoplasmic reticulum

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29
Q

Are peptide hormones hydrophobic/lipophillic or hydrophillic/lipophobic?

A

Hydrophilic/lipophobic

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30
Q

How do they travel in blood?

A

Since hydrophilic they do not need carriers and just dissolve in blood

31
Q

If peptide hormones are lipophobic, what does this mean for its mechanism of action?

A

They can’t cross cell membranes, so must bind to target receptors on the surface of the membrane

32
Q

Do peptide hormones have a generally fast or slow response once bound?

A

Fast

33
Q

What are the 2 pathways used to cause a change in the cell once hormone is bound? What do these pathways cause?

A

G-protein coupled receptors

Tyrosine kinase linked signalling pathways

Both pathways phosphorylate proteins in cell causing a change

34
Q

Explain the G-protein CR pathway

A

Once hormone binds - activates 2nd messenger system (a cascade) and/or opening/closing of ion channels

This leads to modification of proteins and a rapid response

35
Q

Explain the Tyrosine kinase linked receptor

A

Alters gene expression of proteins either activating or de-activating the gene

Is a slower response time

36
Q

Can the GPCR pathway also alter gene expression? If so, how?

A

Yes, the 2nd messengers can alter gene expression

37
Q

What is an issue with peptide hormones?

A

They have a short half life and are vulnerable to degradation - must be continuous secreted to have an effect

38
Q

What are steroid hormones derived from?

A

Cholesterol

39
Q

How are different steroid hormones made if they are all derived from cholesterol?

A

The type of steroid hormone made depends on the fact that different cells have different enzymes synthesizing differing derivatives of cholesterol

40
Q

Are steroid hormones stored?

A

No only made as needed

41
Q

Why are steroid hormones not stored?

A

They are hydrophobic/lipophillic so can’t be kept within the cell membrane

42
Q

How do they travel in blood if they are hydrophobic?

A

Carriers such as albumin

43
Q

What can albumin do for the hormone?

A

Increase half-life of it

44
Q

What hormones does the kidney make?

A

Kidneys make Vit. D3

45
Q

Mechanism of action for steroid hormones?

A

Since they are lipophilic, receptors are inside cell

They alter gene expression - activation or repression which alters protein sysnthesis

46
Q

Steroid hormones have a slow or fast response?

A

Slow when they bind inside cell

Some evidence suggests they can bind on membrane for a rapid effect

47
Q

What are amine hormones derived from?

A

2 amino acids

48
Q

What are the 2 amino acids that amine derives from?

A

Tyrosine

Tryptophan

49
Q

Which of the 2 amino acids makes all but 1 amine hormone?

A

Tyrosine

50
Q

What amine hormone does tryptophan make?

A

Melatonin

51
Q

What does melatonin do?

A

Regulates circadian rhythm

52
Q

What are the 2 subcatagories of amine hormone that tyrosine makes?

A

Catacholamines

Thyroid hormones

53
Q

Name some catacholamines and where they are made

A

Dopamine - brain
Noraadrenaline - neurons
Adrenaline - adrenal gland

54
Q

Mechanism of action for catacholamines?

A

They are hydrophilic/lipophobic so have same mechanism as peptide hormones

55
Q

Are catacholamines vulnerable to degradation?

A

Yes - also need to be continually secreted

56
Q

Name some thyroid hormones.

A

Thyroxine

Triiodothyronine

57
Q

Mechanism of action for thyroid hormones?

A

Hydrophobic/lipophilic so same as steroid

58
Q

Why is it important that there is a small amount of unbound free steroid/thyroid hormone in plasma at any given time?

A

Only unbound can cross membrane
So a ratio exists between bound and unbound and is constantly maintained.

Example - free hormone degrades due to short half life or binds to receptor = bound hormone to unbind = more homrone produced to replace bound hormone lost

59
Q

What is the law of mass action?

A

As free hormone leaves the plasma more hormone is released from carriers

60
Q

Bound:unbound ratio favours what side?

A

Bound is higher

61
Q

In health does the level of free hormones remain constant or vary?

A

Constant

62
Q

How much hormone is needed for a repsone?

A

Minute amounts

63
Q

How is total plasma hormone conc calculated?

A

Free hormone + complex bound hormone

64
Q

What type of hormone carriers are there?

A

Specific - corticosteroid binding globulin (only binds to one hormone)

Non-specific - albumin

65
Q

How are hormones removed from body?

A

Excreted or metabolically transformed via liver and kidneys

66
Q

What hormones are excreted easily?

A

Peptide and catacholamines since short half life

67
Q

What hormones take longer to excrete?

A

Steroids and thyroid hormones since they are protein bound

68
Q

What are 2 ways hormone secretion is controlled?

A

Neg feedback loops - high levels of hormone feeds back and stops production

Neural feedback loops - sympathetic response causes adrenaline secretion

69
Q

What happens when there is a prolonged exposure of low hormone conc. on a cell?

A

The cell will make more receptors to increases sensitivity to the hormone

70
Q

What happens when there is a prolonged exposure of high hormone conc. on a cell?

A

The cell decrease its receptors which in turn decreses sensitivity to the hormone

71
Q

This change in tissue sensitivity can affect receptors for other hormones too - T or F

A

True - Can have permissive or antagonistic effects

72
Q

Explain a permissive effect

A

The presence of one hormone enhances the effect of another

For example adrenaline causes a lower rate of lipolysis in adipose tissue than when adrenaline and thyroid hormone are combined = greater lipolysis

This is because the presence of thyroid hormone causes cell to make more adrenaline receptors - thyroid hormone has no effect on lipolysis but is permissive to adrenaline

73
Q

Hormones are released in short bursts and conc. varies widely. Why is this clinically relevant?

A

A single reading may be misleading - need to monitor over 24 hrs

74
Q

Look at full hormone table on slide

A

Ok

ZA - Endocrine System (21 decks)

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