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ENDOCRINE > A. HORMONAL MECHANISMS > Flashcards

A. HORMONAL MECHANISMS Flashcards

1
Q

what does endocrine mean

A

internal/inside

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2
Q

what does exocrine mean

A

external/outside

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3
Q

what is a endocrine hormone

A

a chemical messenger secreted directly into the bloodstream from (ductless) endocrine gland which targets cell/tissue some distance from endocrine gland
DON’T LEAVE THE BODY

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4
Q

what is a exocrine hormone

A

a chemical messenger released through a duct or opening to body surface from exocrine gland (eg - sweat or salivary gland)

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5
Q

example of endocrine intercellular messenger in body

A

insulin which is released from islets of Langerhans (pancreas), enters bloodstream and acts on liver, adipose tissue, skeletal muscle which are are the 3 main metabolic organs in the body

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6
Q

what are autocrine hormones

A

released by cell into interstitial fluid and then acts on same cell

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7
Q

example of autocrine intercellular messenger in body

A

prostaglandins

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8
Q

what are paracrine hormones

A

released by cell, travels a short distance in interstitial fluid and then targets neighbouring cells

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9
Q

example of paracrine intercellular messenger in body

A

somatostatin on insulin secretion

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10
Q

what are neuroendocrine hormones/neurohormones

A

released from nerve cell/neuroendocrine cell along axon into bloodstream and then act on target cell

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11
Q

example of neuroendocrine intercellular messenger in body

A

oxytocin and arginine vasopressin (antidiuretic hormone) secreted from posterior pituitary gland

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12
Q

what are neurotransmitters

A

released from neurone, cross synaptic cleft and act on another neurone

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13
Q

example of neurotransmitter intercellular messenger in body

A

acetylcholine

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14
Q

what are peptide hormones

A

chains of amino acids and includes those released from hypothalamus, anterior and posterior pituitary, pancreas and GIT

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15
Q

what are steroid hormones

A

derived from cholesterol (in membrane) and includes cortisol, aldosterone (adrenal cortex) and sex hormones (gonads)

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16
Q

what are hormones derived from tyrosine

A

thyroid hormones and catecholamines (adrenal medulla)
eg - Adr, NA, dopamine

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17
Q

what are eicosanoids

A

prostaglandins

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18
Q

peptide hormone synthesis

A

NUCLEUS
- gene to mRNA by transcription
- mRNA to protein by translation

RER AND RIBOSOMES
- preprohormone which undergoes protein folding, disulphide bonding, glycosylation and ‘pre’ signal is cleaved

GOLGI COMPLEX
- prohormone which undergoes additional processing and cleavage

SECRETORY GRANULES
- hormone is packaged into granules, stored until released upon arrival of stimulus and then released by exocytosis

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19
Q

what is exocytosis

A

fusion with plasma membrane and hormone release

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20
Q

how do you increase the rate of peptide hormone release

A

increase the rate of exocytosis

21
Q

steroid hormone synthesis

A

(no gene involved)
- there is a precursor molecule (cholesterol-based) and biosynthetic enzymes in SER and mitochondria
- the hormone is not stored
- the hormone is lipophilic so can pass easily through membrane
- not soluble in blood (aq) so makes weak, reversible bonds with plasma proteins
- hormone is released by simple diffusion

22
Q

how do you increase the rate of steroid hormone release

A

increase steroid hormone production

23
Q

what are peptide hormones half life

A
  • minutes due to proteases in plasma
  • the unbound/free hormone is biologically active
24
Q

what are steroid hormones half life

A
  • hours to days
  • protected by plasma proteins
  • metabolism is delayed and therefore there is a circulating reservoir of hormones and it can’t interact with target
25
Q

peptide hormone action

A

Act on plasma membrane receptors as they are hydrophilic

  1. GPCR
    eg: glucagon via GS, adenylyl cyclase/cAMP
    - hormone binds to GPCR, effector then signal transduction occurs
  2. tyrosine kinase receptor
    eg: insulin
    - hormone binds to receptor and signal transduction occurs

signal transduction causes a physiological response where there is altered activity of enzymes or ion channels or altered expression of specific proteins

26
Q

steroid hormone action (and thyroid hormones)

A

Act on intracellular receptor as they are lipophilic

  1. cytosolic receptor
    - hormone binds to receptor and then the complex binds to promoter region of DNA
    - DNA to mRNA, increased or decreased gene expression causing changes to proteins and biological effects
  2. nuclear receptor
    - hormone diffuses into nucleus

intracellular receptors act as hormone-regulated transcription factors

27
Q

how long does steroid hormone action take

A

hours/days as changing gene transcription but if there are plasma membrane receptors which will cause a faster effect

28
Q

where are hormones metabolised

A
  • by enzymes in liver, kidney or blood
  • small proportion by target tissues
  • excreted in urine or faeces
29
Q

how does feedback regulation regulate hormone release

A

consequence of a process acts to regulate the rate at which the process occurs

30
Q

what is negative feedback

A

consequence negatively controls process to maintain a set-point
(the basis of homeostasis)

31
Q

what is positive feedback

A

consequence enhances or amplifies process further
(not homeostasis)
ie - chemical reaction which causes heat to be released, explosion?

32
Q

example of simple regulation to regulate hormone release

A

beta-cell gland releases insulin from islets of Langerhans which targets liver/skeletal muscle/adipose tissue and causes a decrease in glucose concentration

33
Q

example of feedback regulation in which the hypothalamic and pituitary tropic hormones are involves (endocrine axis)

A

if there is too high a level of peripheral hormones, negative feedback on anterior pituitary gland which decreases amount of tropic hormone released

34
Q

what is the endocrine axis

A

interactions between the hypothalamus, pituitary and peripheral endocrine glands showing feedback regulation to maintain physiological homeostasis

35
Q

how does neuroendocrine reflexes cause regulation of hormone release

A

input from higher centres in brain

36
Q

example of a neuroendocrine reflex

A

increased production of cortisol due to feedback regulation of cortisol (stress hormone) production

37
Q

how does diurnal (day-night) or circadian (around a day) rhythm cause regulation of hormone release

A
  • cortisol levels are normally high in the morning and trough in the late evening
  • with diseases there is a different pattern
  • use when sampling for clinical or experimental reasons
38
Q

what causes endocrine disease caused by hypersecretion

A

tumour or immunological factor (Graves’ disease)

39
Q

what causes endocrine disease caused by hyposecretion

A

genetic deficiency of enzyme making hormone, immunological attack, destruction by disease, surgical removal

40
Q

what causes endocrine disease caused by decreased target-cell responsiveness

A

at level of receptor or downstream enzyme

41
Q

what is primary endocrine disease

A

associated with gland making the hormone

42
Q

what is secondary endocrine disease

A

due to another condition or abnormal hypothalamic-pituitary secretion of tropic hormone

43
Q

example of hypersecretion endocrine disease

A

Cushing’s syndrome (excess cortisol)
primary defect - tumour in adrenal cortex making too much
secondary defect - tumour in anterior pituitary producing too much ACTH
or due to a different condition with an ectopic ACTH-producing tumour

44
Q

how to investigate endocrine disorders

A
  1. signs and symptoms
  2. endocrine investigations (hormone levels)
  3. imaging: tumour?
45
Q

endocrine investigations

A

1) single point (base-line blood tests)
2) dynamic provocative tests to check integrity of feedback control

stimulation tests (used for hypo secretion)
- failure to stimulate indicates hormone insufficiency (confirmatory test)

suppression tests (used for hyper secretion)
- failure to suppress indicates autonomous secretion (tumour)

46
Q

how to treat hormone deficiency

A

hormone replacement

47
Q

how to treat hormone excess

A

drugs to block production or to block hormone receptor (antagonist)

48
Q

how to treat decreased target-cell responsiveness

A

drugs to enhance cellular response to hormone

49
Q

how to treat a tumour

A

radiotherapy or surgery

ENDOCRINE (17 decks)

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