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Human physiology > Endocrine system 1 > Flashcards

Endocrine system 1 Flashcards

1
Q

What is a hormone?

A

A chemical messenger secreted direclty into bloodstrema from (ductless) endocrine glad

Target cell/tissue some distance fram glad

Exocrine (ducts) - e.g. salivary, sweat etc

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2
Q

What are the 5 intracellular messengers in the body?

A
  • Endocrine
  • Autocrine
  • Paracrine
  • Neuroendocrine
  • NTs
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3
Q

What are endocrine messengers?

A

e.g. insulin –> released from islets of langerhans (pancreas); act on liver, adipose, skeletal muscle

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4
Q

What are autocrine messengers?

A

Substance secreted by a cell that travels short distance in the interstitual fluid & acts on the same cell

e.g. Protaglandins

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5
Q

What are paracrine messengers?

A

Released from one cell, travels short distance in interstitual fluid to neighbouring cell

e.g. Somatostatin on insulin secretion

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6
Q

What are neuroendocrine messengers?

A

Hormone stored in axon terminal, when required will be released to act on another cell

e.g. oxytocin & ADH (from pituitary gland)

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7
Q

What are the types of hormones?

A
  • Peptide hormones
  • Steroid hormones
  • Hormones derived from tyrosine
  • Eicosanoids
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8
Q

What are peptide hormoens like?

A

Chains of amino acids (e.g. TRH or LH/FSH)

Incl those from hypothalamus, anterior & posterior pituitary, pancreas

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9
Q

What are steriod hormones?

A

Derived from cholesterol

Incl cortisol, aldosterone (adrenal cortex) & sex hormones (gonads)

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10
Q

What are hormones derived from tyrosine?

A

Thyroid hormones & catecholamines (adrenal medulla)

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11
Q

What do the differences in chemical structures reflect?

A

Reflects the ways which the types of hormones are synthesised, stored, transported & used

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12
Q

What are the stages of peptide hormone synthesis?

A
  • Starts w a gene, this is translated & syntheised
  • It moves across the RER
  • First thing made is a preprohormone, a molecules that signals to the cell that this specific molecule need processing & packaging as it needs to be exported

-The “pre” signal is cleaved and tells the cell whether it needs either - the protein to be folded, disulfide bonds made or glycosylation

-Additional processing happens in the in the golgi, before this the hormone is not mature

-Hormone is then stored until it needs to be released upon arrival of stimulus

-Exocytosis = fusion with the plasma membrane, and hormone release

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13
Q

What are the stages of steroid hormone synthesis?

A
  • Precursor molecule (cholesterol based)
  • Cholesterol converted by a number of enzymes, makes the steroid hormone
  • Can readily pass through the lipid bilayer as it is lipid based - cannot be contained
  • Hormone passes out of membrane via simple diffusion into bloodstream
  • If you need more hormone, you just increase the synthesis of hormone
  • Do not like the hydrophilic environment of water so they must be transported by plasma proteins
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14
Q

What is the solubility of peptide hormones?

A

Hydrophillic

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15
Q

What is the solubility of steroid & thyroid hormones?

A

Lipophilic

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16
Q

Do peptie hormones bind to plasma proteins?

A

No, they’re as free hormones

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17
Q

Do steroid hormones & thyroid hormones bind to plasma proteins?

A

Yes

However are weak, reversible bonds

18
Q

What is the half life of peptide hormones?

(Time taken for the initial amt to fall by 50%)

A

Minutes

Don’t last long due to proteases that break down peptides in the bloodstrean as it is unbound

19
Q

What is the half life of steriod & thyroid hormones?

(Time taken for the initial amt to fall by 50%)

A

Hours - days

20
Q

What is an unbound (plasma proteins) hormone like?

A

It is biologically active

21
Q

What is a bound (plasma proteins) hormone like?

A

Hormone binding delays metabolism, provides a circulating resevoir of hormones

22
Q

Describe peptide hormone action:

A
  • Plasma membrane receptors carry the hormones thru –> either TYROSINE KINASE or G-PROTEIN COUPLED RECEPTORS
  • Activates signal transduction process - mediates a response on the INSIDE relating to hormone on OUTSIDE
  • e.g. glucagon receptor - cAMP
23
Q

Describe steroid hormone action:

A
  • Passes thru the membrane via diffusion
  • It binds to a promoter for a certain gene
  • Intracellular receptors act as hormone-regulated transcription factors
  • Genomic method –> either inc or decrease gene expression
  • Recently plasma membrane receptors have also been found
24
Q

How is hormone release regulated?

A

By feedback regulation –> consequence of a process acts to regulate the rate at which the process occurs

Endocrine feedback is not simple - there will be various feedback loops in a process

25
Q

What is negative feedback?

A

Concequence negatively controls process (maintain a set point)

26
Q

What is positive feedback?

A

Consequence enhances or amplifies the process further

27
Q

What are the 3 types of regulation of hormone release (endocrine feedback)?

A
  • Simple
  • Neuroendocrine reflex
  • Dinural (day-night) or circadian (around a day) rhythm
28
Q

What is simple endocrine feedback?

A

Involvement of hypothalamic & pituitary tropic hormones

29
Q

What is neuroendocrine reflexes?

A

Input from higher centres

30
Q

Look at the endorine axis diagram:

A

This is the example of simple feedback

31
Q

What is the exocrine axis?

A

Interactions between the hypothalamus, the pituitary and peripheral endocrine gland, showing feedback regulation

32
Q

What does dinural rhythm control?

A

Dinuarl rhythm of cortisol plasma levels

Peak early morning, trough in late evening

33
Q

What are 3 endocrine disorders?

A

1) Hormone excess (hypersecretion)

2) Lack of hormone (hypo secretion)

3) Decreased target-cell responsiveness –> At level of receptor or downstream enzyme

34
Q

Give an example of a hormone excess condition

A

Cushing’s syndrome –> excess cortisol

35
Q

What is the primary cause of Cushing’s syndrome?

A

Excess cortisol

36
Q

What is the secondary defect causing Cushing’s syndrome?

A
  • Tumour in anterior pituitary - producing too mcuh ACTH which leads to too much cortisol being produced
  • Ectopic ACTH producing tumour - secretes lots of ACTH, means lots of cortisol
37
Q

What is the treatment for a hormone deficiency?

A

Hormone replacement

38
Q

What is the treatment for hormone excess?

A

Drugs to block production

39
Q

What is the treatment for decreased target-cell responsiveness?

A

Drugs to enhance cellular response to hormone

40
Q

What is the treatment for a tumour causing hormone issues?

A

Radiotherapy or surgery

Human physiology (43 decks)

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