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Endocrine System > Introduction COPY > Flashcards

Introduction COPY Flashcards

1
Q

Define the endocrine system

A

A system that controls organ function via the secretion of hormones that are carried in the blood to a distal target organ from the site of hormone synthesis

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2
Q

What is paracrine signalling?

A

Acts on cells nearby to the site of hormone synthesis

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3
Q

What is autocrine signalling?

A

Acts on the same cell that synthesises it

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4
Q

What is exocrine signalling?

A

Usually secreted through ducts onto a surface

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5
Q

How does tissue detect hormones in circulation?

A

Presence of hormone specific receptors extra/intracellularly

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6
Q

What effect will hormones have on tissue without any receptors?

A

No effect

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7
Q

What is neuroendocrine signalling?

A
  • The co operativity of the endocrine and nervous system
  • The direct release of a hormone packaged in a neurotransmitter vesicle into the bloodstream
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8
Q

Give an example of different responses to the same hormone on two different areas in the body

A

Insulin

  • Skeletal muscle/adipose tissue = increased glucose uptake
  • Liver = increased glycogenesis and decreased gluconeogenesis
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9
Q

What are the 6 typical features of an endocrine hormone?

A
  1. Produced by cells
  2. Secreted into the blood
  3. Transported to different targets
  4. Exert effects at very low conc.
  5. Act by binding to receptors on the targets
  6. Have their action controlled (usually by negative feedback loops)
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10
Q

What are the 3 types of hormone?

A

Peptide

Steroid

Amine

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11
Q

What makes up peptide hormones and how can their structure vary?

A

Chains of amino acids

Can be very long or short

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12
Q

When are peptide hormones made and how are they stored?

A

Made before they’re required

Stored in vesicles

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13
Q

What is the preprohormone?

A

The initial protein

Very large

Inactive

Can contain one or more copies of the active hormone

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14
Q

What happens to the preprohormone?

A

It is cleaved into smaller units in the RER into prohormones (still inactive)

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15
Q

What happens to the prohormone?

A

Packaged into vesicles in the golgi

Proteolytic enzymes are packed with it that cleave it to activate it

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16
Q

When a response occurs, what happens to the vesicles containing the hormone?

A

ALL vesicle contents, including the inactive fragments, are released

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17
Q

How do peptide hormones illicit a response?

A

Water soluble

Bind to G protein coupled receptors or tyrosine kinase receptors

These phosphorylate proteins and modify their function

18
Q

What are steroid hormones made from?

A

Cholesterol

19
Q

When are steroid hormones synthesised?

A

When they are required

They can’t be stored due to their lipophilic nature

20
Q

How are steroid hormones transported in the blood?

A

Bound to carrier proteins (usually albumin)

These complex bound molecules are not active

21
Q

What steroids do the gonads produce?

A

Sex steroids

22
Q

What steroids are produced by the placenta?

A

hCG (human chorionic gonadotrophin)

Sex steroids

23
Q
A
24
Q

What steroid is produced by the kidneys?

A

Vitamin D3

25
Q

What steroids are produced by the adrenal glands?

A

Corticosteroids

26
Q

How do steroids carry out their effect on the target cell?

A

Can readily cross cell membrane

Receptors usually cytoplasmic/nuclear and play a role in gene expression and therefore protein synthesis

27
Q

How fast is the steroid response?

A

Fairly slow

28
Q

What happens to the complex bound hormone as more free hormone leaves the bloodstream?

A

It too leaves its carrier and leaves the bloodstream

29
Q

What are amine hormones made from?

A

Tryptophan (only melatonin)

Tyrosine

30
Q

What two subdivisions of amine hormones can be produced from tyrosine?

A

Catecholamines

Thyroid hormones

31
Q

What do catecholamines have a similar effect to

A

Peptide hormones

32
Q

What do thyroid hormones have a similar effect to?

A

Steroid hormones

33
Q

What does hormone concentration in the blood depend on?

A

Secretion levels

Removal

34
Q

How are most hormones removed from the blood?

A

By the kidneys (excretion)

Metabolic transformation

35
Q

Which hormones are easily excreted and therefore have a short halflife?

A

Catecholamines

Peptides

36
Q

Which hormones are not readily excreted and therefore have a longer halflife?

A

Steroids

Thyroid hormones

37
Q

How are most hormonal pathways controlled?

A

Through negative feedback loops

38
Q

What systemic effect does prolonged exposure to high hormone levels have?

A

Reduction in the number of receptors

39
Q

What systemic effect does prolonged exposure to low hormone levels have?

A

Increase in the number of receptors

40
Q

Describe permissive effects?

A

Prolonged exposure to one hormone effects the response to a different hormone

Endocrine System (90 decks)

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