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Year 2- Endocrine System > Introduction to the Endocrine System > Flashcards

Introduction to the Endocrine System Flashcards

1
Q

What is the function of the endocrine system?

A

Integrates and controls organ function by the secretion of hormones

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2
Q

What are hormones?

A

Chemicals released from cells, tissues or glands

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3
Q

How are hormones transported around the body?

A

Blood

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4
Q

What is meant by endocrine commuinication?

A

Hormones travelling through the blood to their target organs/tissues

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5
Q

Describe the difference between neurotransmitters and endocrine hormones.

A

Neurotransmitters- released by nerves, cross the synapse and have local site of action.
Endocrine hormones- released by cell, travel in blood and have a distal site of action

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6
Q

What happens if a chemical is neuroendocrine?

A

Nerves release hormones which enter the blood and travel to target cells

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7
Q

Give an example of a neuroendocrine tissue.

A

Hypothalamus

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8
Q

The response of target cells to a hormone is very specific. However, the same hormone can have different effects in different cells.

For example, what effect does insulin have when it binds in skeletal muscle/adipose tissue?

A

Increases glucose uptake

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9
Q

The response of target cells to a hormone is very specific. However, the same hormone can have different effects in different cells.

For example, what effect does insulin have when it binds in the liver?

A

Increased glycogenesis
Decreased gluconeogenesis

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10
Q

Endocrine glands are ductless.
Exocrine glands are ducted.
How do exocrine glands work?

A

Deliever their secretions to the external environment including the GIT

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11
Q

Give some examples of exocrine secretions.

A

Sweat, bile, saliva

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12
Q

Which type of glands have ducts?

A

Exocrine

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13
Q

Which type gland are ductless?

A

Endocrine glands

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14
Q

What is meant by autocrine secretions?

A

Cells secrete chemicals that bind to receptors on the same cell

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15
Q

Give an example of a type of cell which produces autocrine secretions.

A

Cytokines

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16
Q

What is meant by paracrine secretions?

A

Chemicals diffuse into the ECF to affect neighbouring cells

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17
Q

Give an example of a cell which uses paracrine secretions.

A

Histamine

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18
Q

Which type of hormonal secretions do not travel in the blood?

A

Autocrine and paracrine secretions.

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19
Q

List some of the glands which have a purely endocrine function.

A

Thyroid gland
Adrenal gland
Pituitary gland
Hypothalamus

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20
Q

Do hormones work at high or low concentrayions?

A

Low concentrations

->tiny changes in hormone levels can change function dramatically

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21
Q

Describe the patter of endocrine hormone release.

A

Often released in short bursts

->this means 24hr monitoring is clinically required to get a realistic picture

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22
Q

Name the three classes of hormone/

A

Peptide/protein hormones
Amine hormones
Steroid hormones

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23
Q

Which classification of endocrine hormone is the most common?

A

Peptide/protein hormones

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24
Q

What are peptide/protein hormones composed of?

A

Chains of amino acids

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25
Q

What are amine hormones composed of?

A

All derived from either tryptophan or tyrosine

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26
Q

In reality, only one hormone is derived from tryptophan and the rest come from tyrosine.
What is the one hormone derived from tryptophan?

A

Melatonin

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27
Q

What are steroid hormones dervived from?

A

Cholesterol

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28
Q

Peptide hormones are initially synthesised as what in advance of need?

A

Preprohormones

29
Q

What happens to the preprohomones?

A

Cleaved into prohormones and stored in vesicles until required

30
Q

Where are the preprohormones synthesised?

A

Ribosomes

31
Q

Where are prohormones packaged into vesicles?

A

Golgi apparatus

32
Q

What else is packaged into the vesicles alongside the prohormone?

A

Proteolytic enzymes

33
Q

What role do the proteolytic enzymes play?

A

Breaks prohormone into active hormone and other inactive fragments

->worth noting that sometimes clinically it is more useful to measure the inactive fragments rather than the active ones, often done in measuring C-peptide in diabetes

34
Q

What is C-peptide?

A

Inactive fragment cleaved from insulin prohormone

35
Q

Why is C-peptide measured?

A

Indicated endogenous insulin production from pancreas

->can be measured in plasma or urine

36
Q

How do the levels of C-peptide compare to levels of endogenous insulin and why?

A

Levels of C-peptide usually 5x higher.
This is because insulin is metabolised faster.

37
Q

Why would you measure C-peptide levels and not insulin levels when determining pancreas function?

A

In those w Type 1 diabetes, they will be taking synthetic insulin which will also be measured and does not relate to pancreas function

38
Q

Are peptide hormones water soluble?

A

Yes

->this means they dissolve easily in plasma making these hormones easily transportable in the blood

39
Q

As peptide hormones are water soluble, this means they cannot simply cross cell membranes.
How do they do it?

A

Bind to receptors on the target cell

40
Q

Which type of receptors do most peptide hormones target?

A

G-protein coupled receptor
Tyrosine kinase linked receptors

41
Q

GCPR and tyrosine kinase linked receptors result in what?

A

Phosphorylation of intracellular target proteins, changing their activity.

42
Q

Do peptide hormones generate fast or slow responses?

A

Fast

43
Q

Are water-soluble peptide hormones hydrophobic or hydrophilic?

A

Hydrophilic

44
Q

RECAP- which enzymes phosphorylate target proteins?

A

Kinase enzymes

45
Q

In terms of peptide hormone signal transduction, hormones coupled to which type of receptor leads to rapid responses?

A

G-coupled protein receptors (GCPR)

46
Q

In terms of peptide hormone signal transduction, hormones coupled to which type of receptor leads to slower, long lasting responses?

A

Tyrosine kinase linked receptor

47
Q

RECAP- the majority of amine hormones are dervobed from which amino acid?

A

Tyrosine

48
Q

List some amine hormones.

A

Dopamine, norepinephrine, epinephrine (catecholamines)
Tetraiodothyronine, triiodothyronine (thyroid hormones)

49
Q

Which other type of hormones do catecholamines have similar mechanisms to?

A

Peptide hormones

50
Q

Which other type of hormones do thyroid hormones have similar mechanisms to?

A

Steroid hormones

51
Q

Which type of hormone is synthesised when required and not stored?

A

Steroid hormones

52
Q

Why are steroid hormones only synthesised when required?

A

They are highly lipophilic so cannot be retained within lipid membranes

53
Q

Steroid hormones are poorly soluble in water. Therefore, how are they transported?

A

Bound to proteins such as albumin

54
Q

Describe the onset of action of steroid hormones

A

Slow onset but action lasts much longer than peptide or amine hormones

55
Q

What produces steroid hormones?

A

Gonads (testes and ovaries)
Placenta
Kidney
Adrenal cortex

56
Q

Which type of steroid hormones are produced in the gonads?

A

Sex steroids

57
Q

Which type of steroid hormone are produced by the placenta?

A

hCG
Sex steroids

58
Q

Which type of steroid hormone are produced by the kidneys?

A

Vitamin D3

59
Q

Which type of steroid hormone are produced by the adrenal cortex?

A

Corticosteroids

60
Q

Are steroid hormones lipophilic or hydrophilic?

A

Lipophilic

->this means they can readily cross the plasma membrane and enter cells which means they have intracellular receptors

61
Q

What happens when there is activation of intracellular receptors by steroid hormones?

A

Changes in gene expression which in turns affects protein synthesis

62
Q

There is a small amount of unbound/ free steroid/thyroid hormone.
What can this hormone do that bound hormone cannot?

A

Cross capillary walls to target cells.

->amount of free hormone is a lot less than the amount of hormone bound to protein

63
Q

In order to calculate total plasma hormone levels, what do you need to do?

A

Free hormone = complex (bound) hormone

64
Q

Thyroid hormones act like steroid hormones but are actually which type of hormone?

A

Amine hormones

65
Q

Are thyroid hormones or lipophilic or hydrophilic?

A

Lipophilic

->act like steroid hormones

66
Q

The vast majority of hormone secretion is controlled by which mechanism?

A

Negative feedback

67
Q

Neuroendocrine pathways also respond to which other type of feedback as well as negative feedback?

A

Neural feedback loops

68
Q
A

Year 2- Endocrine System (27 decks)

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