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2nd year- endocrine OC > Diabetes & Endocrinology Welcome > Flashcards

Diabetes & Endocrinology Welcome Flashcards

1
Q

whats the definition of the endocrine system?

A

A system that integrates and controls organ function via the secretion of chemicals (hormones) from cells, tissues or glands which are then carried in the blood to target organs, distal from the site of hormone synthesis, where they influence the activity of that target organ.

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2
Q

what is the response rate in the endocrine system?

A

Response may be fast (within seconds) e.g. increased heart rate in response to adrenalin, or slow (over days) e.g. increased protein synthesis in response to growth hormone.

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3
Q

what are paracrine chemicals?

A

act local to the site of synthesis, do not travel to distant sites e.g. histamine

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4
Q

what are autocrine chemicals?

A

act on/in the same cell that synthesises the hormone e.g. cytokines

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5
Q

what are exocrine chemicals?

A

released from exocrine glands via ducts to the external environment including the GI tract e.g. saliva, sweat, bile

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6
Q

what is the endocrine communication?

A

Hormones travel in the blood to their target organs/tissues.

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7
Q

how do tissues detect hormones?

A

Tissues detect hormones through the presence of specific receptors for that chemical on/in the cells. No receptor = no response

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8
Q

what is neural communication?

A

Neurotransmitters released from presynaptic neurons travel across the synaptic cleft to the postsynaptic cell to influence its activity. Neurotransmitter is the chemical released by the neuron but, in contrast to hormones, acts locally within the synaptic cleft.

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9
Q

what can the endocrine and nervou system work together to control?

A

The endocrine and nervous systems co-operate intimately to provide further control, particularly for long-term phenomena, e.g. growth.

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10
Q

what is neuroendocrine?

A

endocrine and nervous systems combine. Nerves release hormones which enter blood and travel to their target cells e.g. hypothalamic – posterior pituitary axis

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11
Q

what is the function of hormones?

A

to bring about changes in the activity of their target cells and tissues, (increase/decrease a particular activity).

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12
Q

what are the features of an endocrine hormone?

A

Produced by a cell or group of cells

Secreted from those cells into the blood

Transported via the blood to distant targets

Exert their effects at very low concentrations (act in the range 10-9 -10-12 M)

Act by binding to receptors on target tissues

Have their action terminated, often via negative feedback loops.

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13
Q

classifications of endocrine hormones

A

Peptide or protein hormones – composed of chains of amino acids (most common)

Amine hormones – all derived from one of two amino acids (tryptophan or tyrosine)

Steroid hormones – all derived from cholesterol

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14
Q

what are peptide hormones synthesised as in advance?

A

preprohormone in advance of need then cleaved into pro hormone and stored in vesicles until required

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15
Q

what are preprohormones?

A

contain one or more copies of the active hormone in their amino acid sequence.

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16
Q

what are preprohormones cleaved into?

A

cleaved into smaller units in the endoplasmic reticulum to leave smaller

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17
Q

what are inactive smaller proteins called?

A

prohormones

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18
Q

where are prohormones packaged into?

A

vesicles in the golgi apparatus, along with proteolytic enzymes which break the prohormone down into active hormone and other fragments.

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19
Q

what is C-peptide?

A

the inactive fragment cleaved from the insulin prohormone

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20
Q

why are levels of C-peptide in plasma or urine measured?

A

indicate endogenous insulin production from the pancreas

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21
Q

why are C-peptide typically 5x higher than endogenous insulin?

A

because insulin is metabolised faster

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22
Q

what is the mechanism of action of peptide hormones?

A

Water soluble so dissolve easily in plasma making transport via the blood simple and easy. Water solubility however means cannot cross cell membrane so bind to membrane bound receptors on target cell.

Once bound these receptors generally create relatively fast biological responses (seconds to minutes). Most peptide hormones work via modulating either the GPCR or tyrosine kinase linked signalling pathways. These pathways phosphorylate existing proteins in the cell and modify their function e.g. open or close ion channels, activate or inactivate enzymes.

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23
Q

what do peptide hormones bind with to activate signal transduction?

A

hydrophillic/lipophobic binds to cell surface receptor which is either

G protein couple receptor or tyrosine kinase linked receptor

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24
Q

what does the G protein couple receptor do?

A

Activates 2nd messenger system and/or ion channels leading to modification of existing proteins. Rapid response

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25
Q

what does the tyrosine kinase linked receptor do?

A

alters gene expression. Slower, longer lasting activity

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26
Q

what are amine hormones mostly derived from?

A

amino acid tyrosine

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27
Q

where is the epinephrine released?

A

hormone released by adrenal medulla

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28
Q

what are the two amine hormones derived from tyrosine?

A

catecholamines abd thyroid hormones

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29
Q

what is the only amine hormone that is not dervied from tyrosine?

A

melatonin

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30
Q

where is melatonin derived from?

A

tryptophan

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31
Q

what does melatonin do?

A

regulates circadian rhythm

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32
Q

what is the mechanism of catecholamines similar to?

A

peptide hormones (hydrophilic)

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33
Q

what is the mechanism of action of thyroid hormones similar to?

A

steroid hormones (lipophilic)

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34
Q

what are the three types of catecholamines?

A

Dopamine (CNS neurotransmitter)

Norepinephrine (neurotransmitter)

Epinephrine (hormone released by adrenal medulla)

35
Q

what are the two types of thryoid hormones?

A

thyroxine

triiodothyronine

36
Q

where are the lipids from steroid hormones derived from?

A

cholesterol

37
Q

what is different about steroid hormones?

A

synthesized directly as needed, rather than being stored and released

38
Q

why are steroid hormones synthesised directly as needed?

A

because they are highly lipophilic (lipid soluble) so cannot be retained within lipid membranes. Once synthesized they diffuse across the membrane into the ISF and the blood.

39
Q

where are steroid hormones transported to?

A

Being poorly soluble in water they are transported bound to carrier proteins such as albumin

40
Q

why is steroid hormones bound to albumin?

A

This stabilises their transport through the plasma and protects them from enzymatic degradation, phenomenally increasing their half life (60-90mins vs 2mins for amine hormones).

41
Q

what are steroid hormones produced by?

A

Gonads (testes and ovary) – sex steroids
Placenta - hCG, sex steroids
Kidney - Vitamin D3
Adrenal cortex - corticosteriods

42
Q

are all steroid hormones derived from cholesterol?

A

yes

43
Q

what is the mechanism of action of steroid hormones?

A

Because steroid hormones are lipophilic they cross the plasma membrane easily, both into and out of cells. As such their receptors are located inside cells (cytoplasmic or nuclear receptors) and trigger either activation or repression (inhibition) of gene function within the nucleus = genomic effect.

44
Q

there is a small amount of unbound free steroid/thyroid hormone in the plasma, why is this physiologically important?

A

Only free hormone can diffuse across capillary walls to target cells.

45
Q

what is the law of mass action?

A

dictates that as free hormone leaves the plasma (taken up by cells) more hormone is released from the carriers. Typically only minute quantities of hormone are required for physiological functions.

46
Q

how is the bound:unbound ratio maintained?

A

as steroid taken up; more is released from carrier

allows for a reservoir of hormone ready for action

prolonged activity

bound steroids blocked from entering cells

47
Q

what is the concentration of hormone in the plasma determined by?

A

the balance between secretion and degradation

48
Q

what kind of feedback is present in endocrine pathways?

A

In most endocrine pathways, secretion is responsive to negative feedback reflexes e.g. parathyroid hormone

49
Q

what pathways respond to neural feedback loops?

A

adrenaline

50
Q

what are factors that impact on endocrine function

A

Prolonged exposure to low [hormone]plasma often leads to up-regulation of receptor number

Conversely, prolonged exposure to high [hormone]plasma typically leads to down-regulation of receptor number (decreases tissue sensitivity to hormone).

51
Q

what are permissive effects?

A

the presence of one hormone enhances the effect of another

eg epinephrine causes only modest lipolysis in adipose tissue, but when thyroid hormones are also present, greatly increased lipolysis occurs.

52
Q

what are antagonist effects?

A

The presence of one hormone reduces the effect of another e.g. Growth hormone impairs the response to insulin by decreasing the number of insulin receptors on tissues.

53
Q

what happens when insulin binds to skeletal muscle?

A

Increase glucose uptake

54
Q

what happens when insulin binds to the liver?

A

Increased glycogenesis

Decreased gluconeogenesis

55
Q

what are examples of peptide hormones?

A

TRH, FSH and insulin

56
Q

what hormone does the pineal gland produce?

A

melatonin

57
Q

what are the main effects of melatonin?

A

cricardian ryhythm
antioxidant
immune function

58
Q

what hormones are produced by the hypothalamus?

A

trophic hormones

59
Q

what is the primary target of tropic hormones from the hypothalamus?

A

anterior pituitary

60
Q

what is the main function of trophic hormones from the hypothalamus?

A

release or inhibit pituitary hormones

61
Q

what are the hormones produced by the posterior pituitary?

A

oxytocin and vasopressin

62
Q

what are the hormones produced by the anterior pituitary?

A 
prolactin
GH
corticotropin
thyrotropin
follicle-stimulating hormone
luteinzing hormone
63
Q 
what are the effects of prolactin
GH
corticotropin
thyrotropin
follicle-stimulating hormone
luteinzing hormone
A 
milk production
growth factor secretion and growth metabolism
cortisol release
thyroid hormone synthesis
egg or sperm production
64
Q

what are the hormones that are secreted by the thyroid gland?

A

triiodothyronine and thyroxine

calcitonin

65
Q

what are the mian effects of triiodothyronine and thyroxine

calcitonin

A

metabolism, growth and development

plasma calcium levels

66
Q

what are the hormones produced by the parathyroid gland?

A

parathyroid hormone

67
Q

what are the main effects of the parathyroid hormone

A

regulate plasma calcium and phosphate levels

68
Q

what are the hormones produced by the thymus?

A

thymosin and thymopoietin

69
Q

what are the main effects of thymosin and thymopoietin?

A

lymphocyte development

70
Q

what are the homrones produced by the heart?

A

atrial natriuretic peptide

71
Q

what are the main effects of atrial natriuretic peptide

A

increases sodium development

72
Q

what are the hormones produced by the liver?

A

angiotensinogen and insulin-like growth factors

73
Q

what are the effects of angiotensinogen and insulin-like growth factors?

A

aldosterone secretion
increases blood pressure
growth

74
Q

what are the hormones produced in the stomach and small intestine?

A

gastrin, cholecystokinin, secretin and others

75
Q

what are the main effects of gastrin, cholecystokinin, secretin and others

A

assist digestion and absorption of nutrients

76
Q

what hormone is produced in the pancreas?

A

insulin, glucagon, somatostatin, pancreatic polypeptide

77
Q

what is the main effect of insulin, glucagon, somatostatin, pancreatic polypeptide

A

metabolism of glucose and other nutrients

78
Q

what hormones are secreted in the adrenal cortex?

A

aldosterone, cortisol, androgens

79
Q

what are the main effects of aldosterone, cortisol, androgens

A

sodium and potassium homeostasis
stress response
sex drive in females

80
Q

what are the hormones secreted in adrenal medulla?

A

epinephrine, norepinephrine

81
Q

what are the main effects of epinephrine, norepinephrine

A

fight or flight response

82
Q

what are the hormones secreted in the kidney

A

erythropoietin, 1,25 dihydroxy-vitamin D3

83
Q

what are the effects of erythropoietin, 1,25 dihydroxy-vitamin D3

A

red blood cell production and increase calcium absorption

2nd year- endocrine OC (27 decks)

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