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Physiology > exocrine system - videos - week 3 > Flashcards

exocrine system - videos - week 3 Flashcards

adrenal glands, blood glucose conc

1
Q

What is the endocrine system

A
  1. cell to cell communication via chemical messenger
  2. travels via circulatory system long distances between gland and target cell - cm to meters
    - slow - min to days - doesn’t always take shortest route
    - sustained signalling, sometimes irreversible - can’t rapidly turn signal of
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2
Q

What is the Endocrine axis ?

A
  • system of communication between multiple endocrine glands
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3
Q

Name three examples of the endocrine axes?

A
  • hypothalamic-pituitary adrenal (HPA)
  • Hypothalamic pituitary gonadal (HPG)
  • hypothalamic-pituitary-thyroid
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4
Q

What are the bodily functions regulated by the endocrine system?

A
  • homeostasis eg. blood glucose - pancreatic hormones
  • growth and development
  • stress acute or chronic
  • red blood cell production
  • organ to organ communication
  • circulatory and digestive system in parts
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5
Q

How to classify endocrine glands?

A

broadly into primary - inside CNS or secondary - outside CNS, in peripheral

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6
Q

Name central glands

A

hypothalamus
pineal gland
pituitary

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7
Q

Name peripheral glands

A

gonad
adrenal
pancreas

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8
Q

What is the only example of a direct feedback loop in the endocrine system?

A

heart produces ANP - blood pressure regulation

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9
Q

What prepares the body for the spike in glucose after having a meal?

A

Stomach produces ghrelin - controls appetite and body mass

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10
Q

How do we classify endocrine hormones?

A

hydrophilic - peptides, biogenic amines

hydrophobic - biogenic amines and steroid hormones

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11
Q

What is an example of a peptide hormone made from a single peptide chain?

A

Insulin

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12
Q

How is insulin produced?

A
  • initially signal sequence removed
  • required for traffic to the Golgi for packaging
  • disulphide bonds across primary chain form a loop
  • C chain removed to create a 2 peptide molecule held by disulphide bonds
  • single insulin gene
  • peptide fold into spiral
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13
Q

What does melatonin come from?

A
  • the neurotransmitter serotonin
  • produced in hour of darkness
  • sleep regulation, seasonal breading
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14
Q

What is the best example for hydrophobic hormones?

A
  • thyroid hormones T3 or T4 - depending on how many iodines added to 5 prime
  • if present T4 - more common, weak
  • if missing T3 - stronger
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15
Q

What other hydrophobic hormones are there?

A

steroid hormones

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16
Q

Which steroid hormones are produced from C27 cholesterol in the adrenal gland?

A
  • glucocorticoids (cortisol - C21)
  • mineralocorticoids (aldosterone - c21)
  • adrenal androgens (DHEA- C19)
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17
Q

Which steroid hormones are produced from C27 cholesterol in the gonadal glands?

A
  • progesterone
  • androgens
  • estrogens
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18
Q

Steroid hormones all originate from…

A

cholesterol via progesterone - hydrophobic ring structure

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19
Q

How do hydrophilic hormones actually create a cellular response?

A
  • bind to transmembrane receptor
  • includes secondary messenger/ion
  • active kinase enzymes within a cell (protein kinase or lipid kinase)
  • alters activity of existing proteins - quick
  • alter gene expression - slow
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20
Q

How do hydrophobic hormones cause a cellular response?

A
  • can pass directly though membrane
  • bind to transmembrane receptor
    . includes secondary messenger
    . activate kinase enzymes within a cell (protein kinase or lipid)
    . alters activity of existing proteins
    . alter gene expression
  • bind to nuclear receptors
    . form ligand dependent transcription factors
    . regulate gene expression via histone mod
    . slower but more sustained changes
    . new gene could be structural or enzymatic
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21
Q

How many control points do direct feedback loops have?

A

single one

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22
Q

What is the best example of a direct feedback loop in mammals?

A

atrial natriuretic peptide (ANP)

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23
Q

What are first order feedback loops?

A

single feedback loop via a signalling centre
eg. sensory neuron - integrating center - neuron - target organ

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24
Q

How many control points do second order feedback loops have?

A

two

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25
Q

What’s the HPT axis?

A

Hypothalamus -> TRH -> anterior pituitary -> TSH -> thyroid -> T3 and T4
(negative feedback loop)

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26
Q

What is the function of the outer cortex of the adrenal gland?

A

makes the corticosteroid hormones

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27
Q

What is the function of the inner medulla of the adrenal gland?

A
  • chromaffin cells
  • make catecholamines (adrenaline)
  • neural crest derived during Embryo development
  • can make neurotransmitter
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28
Q

What is the neural crest?

A

a group of cells which migrate through the early embryo and have neural identity
- can Mae neurotransmitters

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29
Q

Name the layers of the adrenal gland from outer to inner

A

capsule
zona glomerulosa
zona fasciculata
zona reticularis
medulla

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30
Q

What is the capsule ?

A

though outer layer of the adrenal gland

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31
Q

What is the function of the zone glomerulosa?

A
  • synthesis mineralocorticoids
  • aldosterone
  • reabsorption of Na+ ions in kidney
  • increases plasma volume
  • increases blood pressure
  • increases secretion of K+ ions into urine
  • stimulated by changes in ion conc
    -> K ions sensed directly,
    -> Na ions sensed indirectly
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32
Q

Describe the renin-angiotensin-aldosterone- system (RAAS)

A
  • not an endocrine axis - only one gland
  • fall in blood volume- blood pressure
  • less blood = less sodium sensed by kidney
  • increased conversion of protein to renin - enters blood
  • enin converts angiotensionogen to angiotensin 1 (hormone)
  • causes blood vessels to constrict
  • Angiotensin 1 converted to angiotensin 2 by Angiotensin conversion enzyme (ACE)
  • AT2 receptors in ZG stimulate aldosterone synthesis in adrenal gland
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33
Q

Is renin an enzyme of a hormone?

A

active enzyme

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34
Q

name the functions of the zone fasciculata

A
  • synthesis glucocorticoids (cortisol)
  • increases blood plasma glucose conc and NEFAs
  • chronic stress response
  • inhibit non-essential activities and immune system
35
Q

Describe how the zone fasciculata is stimulated by the ACTH form the anterior pituitary gland (HPA axis)

A
  • adrenal gland produces cortisol
  • circulates bound to albumin or cortisol- binding globulin
  • cortisol causes negative feedback on cortisol releasing hormone (CRH) from the hypothalamus
  • also causes negative feedback on ACTH form pituitary gland
  • also impacts metabolic inputs to hypothalamus
36
Q

What is the ACTH interaction with the HPA in the zona fasciculata an example of?

A

third order feedback system

37
Q

What is the function of the zone reticularis?

A
  • adrenal androgens (dehydroepiandrosterone DHEA)
  • metabolised to potent androgens (testosterone and estrogens) in other tissues
  • pubertal development (increased DHEA)
  • later life aging (declines DHEA)
  • stimulated by ACTH form HPA axis
  • circulates bound to albumin and SHBG
  • sulphated DHEA has no affinity for SHBG and becomes water soluble
38
Q

Describe the function of the medulla

A
  • modified sympathetic ANS
  • produce catecholamines (noradrenaline and also adrenaline)
  • 80% adrenaline
  • no endocrine control
39
Q

What are chromaffin cells ?

A

modified neurons with no axons, neural crest derived

40
Q

Where is the adrenaline stored in?

A

granules - sympathetic neural input causes secretion of adrenaline

41
Q

Describe the conversion of noradrenaline to adrenaline

A

methylation by PNMT enzyme
- expression unregulated in chromaffin cells only
- phenyl ethanol-amine N-methyl transferase
(CH2)

42
Q

Describe the the function fo the GPCR receptors in the adrenaline response

A
  • alpha receptors - modulate intracellular calcium signalling, increase intracellular calc causing contraction
  • beta receptors - adenyl cyclase action, cAMO prodded protein kinase activated
43
Q

Describe an acute stress response

A
  • increases blood flow, blood pressure and heart rate (alpha)
  • increases blood glucose conc (beta receptor response)
  • sensitising the CNS (pupil dilation, sweating)
44
Q

How is blood glucose regulated?

A

high blood sugar: promotes insulin release by the pancreas, stimulates glycogen formation in the liver, and glucose uptake form food which lowers blood glucose

low blood sugar: promotes glucagon release from pancreas which stimulates the breakdown of glycogen in the liver producing more glucose

45
Q

What cells can be found in a cross section of the pancreas?

A
  • islet of langerhans surrounded by acinus
  • delta cells - secrete somatostatin
  • alpha cells - secrete glucagon
  • beta cells - secret insulin
    PP cells - secrete pancreatic polypeptide
46
Q

What is the blood glucose concentration?

A

between 4 and 8 mol/litre of blood

47
Q

What is the result of hypoglycaemia?

A

brain function damage if sustained

48
Q

What is the result of hyperglycaemia?

A

changes in osmolality, water retention

49
Q

What else can glucose do that has negative consequences on the body?

A

stick to lipids and proteins which causes kidney, nerve and capillary damage

50
Q

What is the relationship between insulin and glucagon?

A

antagonistic

51
Q

What is the result of anabolic states ?

A

results in polymer synthesis, driven by insulin

52
Q

What is the result of catabolic states?

A

results in polymer breakdown, driven by glucagon

53
Q

What happens in the cells when blood glucose rises?

A

. alpha cells repressed
-> produces less glucagon
-> less glucose produced
. beta cells activated
-> produce insulin -> more glycogen made

54
Q

What happens in the cells when blood glucose rises?

A

. alpha cells activated - produce glucagon - more glucose made
. beta cells repressed
-> reduces less insulin
-> less glycogen made

55
Q

How do cells respond to insulin?

A
  • insulin binds to receptor
  • signal cascade
  • exocytosis
  • glut-4
  • glucose entry permitted
56
Q

What is the secretion of adrenaline form the adrenal gland an example of?

A

a neuroendocrine reflex

57
Q

name hormones that are able to inhibit/ suppress anabolic reactions and stimulate/ upregulate catabolic reactions with the consequence of elevating the plasma glucose membrane

A

cortisol
adrenaline
glucagon

58
Q

What biogenic amines are hormones?

A
  • melatonin
  • adrenaline
  • thyroxine
59
Q

Delta cells synthesise and secrete which hormones?

A

growth hormone inhibitory hormone GIHIH

60
Q

Describe the sequence by which an elevation in plasma glucose conc triggers the exocytosis of insulin form pancreatic beta cells

A
  • glucose enters cell by facilitated diffusion using GLUT2 transporter
  • glucose metabolised by glucokinase to glucose-6-phosphate
  • oxidation of glucose-6-phosphate to pyruvate increases intercellular ATP conc
  • ATP binds to ATP dependent potassium channel causing conformational change that closes ion channel
  • trapping potassium ions inside cell causes depolarisation of the plasma membrane
  • depolarisation of plasma membrane opens voltage-gated calcium channels
  • calcium ions flood into cell to raise intracellular calcium conc
  • secretory vesicles containing insulin fuse with plasma membrane of the cell to release pre-formed insulin molecules into circulation
61
Q

Definea hormone

A

Long distance chemical mediator secreted by an endocrine gland into the blood, which transports it to tis target cell

62
Q

What is the difference between a hormone and a neurotransmitter?

A
  • neurotransmitters are released across a neuromuscular junction or synapse -> short distance
  • hormones are produced by a gland and signal via transport within the circulatory system -> long distance
63
Q

What do you know about the endings of feedback loops?

A

negative - infinite
positive - defined end

64
Q

Describe the example of oxytocin as a positive feedback loop

A
  • initial stimulus: first contractions
  • stretch sensitive neurons in cervix
  • released form posterior pituitary
    -> produced from hypothalamus, stored in vesicles, released from pituitary
  • oxytocin causes uterine muscles to contract
  • after labour, stretch is lost, oxytocin production slows
  • contractions stop
65
Q

What is oxytocin an example of?

A

a neuroendocrine reflex

66
Q

What is a neuroendocrine reflex?

A
  • neurone releases hormone, not a neurotransmitter form the pituitary gland
  • produced in hypothalamus, transported in vesicles along the cell body of pituitary
67
Q

What triggers the adrenaline response?

A

neuronal signal triggers adrenaline release form vesicles in medulla of the adrenal gland which release into the blood

68
Q

What do cells do in response to adrenaline?

A

vasoconstriction, increased heart rate, insulin suppression, amino acid, NEFAs release sensitisation of CNS

69
Q

Why is the adrenaline response useful?

A

fight or flight

70
Q

What is the relationship between melatonin and cortisol?

A
  • pineal gland produces melatonin, adrenal gland produces cortisol
  • have diurnal rhythm regulation
  • balance of the regulates sleep
  • no two people are the same
  • shift workers insomnia - severe disruptions
  • severity depends on work conduction (where)
71
Q

Hyper means what?

A

too much

72
Q

Hypo

A

too little

73
Q

Mia means what

A

in the blood

74
Q

What is the risk with hormone inhibitors?

A

overcompensation risk - patient could instantly switch rom symptoms of excess dosage to deficiency
- does must be titrated

75
Q

What about taking hormones?

A
  • hydrophobic hormone analogues active orally
  • hydrophilic hormones must bypass the stomach due to stomach acid peptidase/protease enzymes
76
Q

diabetes type 1

A
  • insulin dependent diabetes
  • as a result of pancreas not producing insulin
  • cause only partially known
  • blood glucose must be closely monitored
77
Q

diabetes type 2

A
  • blood glucose often too high
  • insulin resistant diabetes
  • both genetic and environmental inputs
  • desensitisation of the insulin receptor
  • caused by high glucose, pancreas produces more insulin, high levels of insulin, low levels of action
78
Q

hyperthyroidism

A
  • grave’s disease - thyroid attacked by immune system and produces T3 and T4 in response
  • diet high in iodine
79
Q

If hyperthyroidism is not a cause of an enlarged thyroid, what is the cause?

A

lack of iodine causes thyroid to grow
elevated TSH also causes growth
produces more thyroid hormone

80
Q

Is pituitary adenoma cancerous?

A

no

81
Q

Treating hyperthyroidism

A
  • pharmacological inhibition of thyroid hormone synthesis
  • radio-iodine
  • surgery - complete or partial removal
  • symptomatic treatments only
82
Q

What is Cushing’s disease?

A
  • pituitary gland benign tumours - excessive ACTH produced
  • adrenal gland prices excessive cortisol
  • cancerous growths of adrenal gland
83
Q

How is Cushing’s disease treated?

A
  • slow removal of steroid medication
  • tumour removal
  • cortisol blockers
84
Q

What is Addison’s disease?

A
  • adrenal insufficiency (primarily cortisol and aldosterone)
  • destruction of the adrenal cortex (normally autoimmune, also cancerous growth or surgical removal)
  • 2ndary: caused by damage to pituitary gland
  • treated by steroid replacement
  • hydrocortisone to replace cortisol
  • DHEA supplements form health food shops

Physiology (18 decks)

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