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Biomedical Physiology > Endocrine system (W3) > Flashcards

Endocrine system (W3) Flashcards

1
Q

What is the endocrine system?

A

Communication between cells using chemical messengers

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2
Q

Why is the endocrine system usually very slow

A

it relies on the circulatory system as a transportation
- chemical messenger doesn’t all take the correct path

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3
Q

How is the signal normally sustained

A

the signal is in general circulation so it normally can’t be switched off as it might be signalling over shorter distances
- hormone is eventually used

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4
Q

What is an endocrine axes

A

system of communicating between multiple endocrine glands and eventually the target cell

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5
Q

What are the functions of the endocrine system

A
  • homeostasis
  • growth and development
  • regulation of stress responses (acute and chronic)
  • RBC production
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6
Q

How do we classify glands

A
  1. Central (primary)
    - inside the CNS
  2. Peripheral (secondary)
    - outside the CNS
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7
Q

Explain how hydrophilic hormones are classified and give an example

A
  • peptides and biogenic amines
    • transcribed & translated
  • insulin
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8
Q

Explain how hydrophobic homes are classified and give an example

A
  • biogenic amines & steroid hormones
  • thyroid hormones
    • T3/T4 depending on how many iodine atoms are added to the 5 prime carbon
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9
Q

What is the difference between T3 & T4 and both of their functions

A

T3 - missing iodine
T4 - present iodine
- regulate metabolism

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10
Q

What steroid hormones are produced form C27 cholesterol in the adrenal glands

A
  • glucocorticoids
  • mineralocorticoids
  • adrenal androgens
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11
Q

What steroid hormones are produced gonadal adrenal glands

A
  • progestogens
  • androgens
  • estrogens
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12
Q

How can hydrophilic hormones cause a cellular response

A
  • bind to transmembrane receptor
  • induce secondary messenger
  • activate kinase enzymes within a cell
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13
Q

How can HYDROPHOBIC hormones cause a cellular response

A
  • bind to nucelar receptors
  • from ligand dependant transcription factors
  • regulate gene expression …
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14
Q

What is temporal control

A

providing a signal to the organism when its needed

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15
Q

What is positive feedback and give an example

A
  • progression away from et point enhancing effect of stimulus
    CHILDBRITH
  • nerve impulses from cervix transmitted to brain
  • brain stimulates pituitary gland to secret oxytocin
  • oxytocin carried in bloodstream to uterus
  • stimulates uterine contraction and pushes baby towards cervix
  • head of baby pushed against cervix
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16
Q

Explain the process of 1st to 3rd order feedback loops

A

1st order - single feedback loop via a signalling centre
- stimulus is detected by a sense organ not the endocrine gland
2nd - 2 control points (neurone and endocrine gland)
3rd order - 3 control point (additional endocrine gland)

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17
Q

What is the effect of the order feedback loops

A
  1. dampen the stimulus reducing input to sensory organ
  2. act on nay endocrine gland producing the hormones being released
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18
Q

Describe the HPT axis pathway

A

3RD order feedback system
- the release of T3/4 from the hypothalamus
- release of TRH (excitatory)
- cause the anterior pituitary gland to release TSH
- TSH acts on thyroid causing it to release thyroglobulin - T3/T4

19
Q

Why is the HPT axis a 3rd order feedbak system

A
  • T3/T4 act on the stimulus (receptors on hypothalamus and Pituitary gland)
  • pituitary gland also affected
20
Q

Describe the function of the
- outer cortex
- inner medulla of the adrenal glands

A

Outer cortex
- makes corticosteroids

Inner medulla
- filled with chromaffin cells which make catecholamines (make adrenaline)
- derived from neural crest cells

21
Q

What are neural crest cells

A

group of cells which migrate through the early embryo and have neural identity

22
Q

What the function of the Zone glomerulosa (ZG)

A
  • synthesis of mineralocorticoids (aldosterone)
  • reabsorb Na+ ions in kidney by the ANS
  • directly sense potassium ions
  • indirectly sense sodium ions
23
Q

What is a result of increased sodium uptake in kidneys

A

Increased water uptake leading to
- increased plasma volume
- increased blood pressure
increases secretion of potassium ions into urine

24
Q

Describe the RAAS system

A
  1. fall in blood volume/pressure
  2. less blood meaning less sodium sensed by kidney
  3. increased conversion of prorenin to renin active enzyme) which enters the blood
  4. renin converts Angiotensin 1 to 2 by ace
  5. AT2 receptors in ZG stimulate aldosterone synthesis in adrenal glands
25
Q

What is the function of the Zona fasciulata

A
  • synthesises glucocorticoids
  • increase blood plasma glucose concentration
  • chronic stress response
26
Q

Describe how ZF cause negative feedback

A

inhibits non-essential activities and immune system
1. stimulates by ACTH from anterior pituitary gland HPA axis
2. adrenal gland produces cortisol which circulates the blood bound to albumin
3. cortisol causes negative feedback on cortisol releasing hormone from hypothalamus + ACTH from pituitary gland

27
Q

Describe the function of the Zona reticularis

A
  • synthesis adrenal androgens
  • pubertal development
  • simulated by ACTH from HPA axis
28
Q

Describe the function of the medulla

A
  • filled with chromatin cells
  • produce catecholamines (make adrenaline)
29
Q

Describe the process of noradrenaline to adrenaline

A

methylation by PNMT enzyme
- only due to the up regulation (very high level) of glucocorticoids

30
Q

What is adrenal stored as and how is is released

A
  • as granules in the medulla
  • released by the ANS (neural input)
31
Q

Describe the adrenal response to stress

A
  1. bind to GPCR receptors (alpha and beta)
  2. Alpha - modulate intracellular calcium signalling causing contraction
    Beta receptors - adenyl cyclase action, cAMP produced , protein kinase A activated
  3. acute stress response (increase HR …)
32
Q

What 4 hormones do the Islet of Langerhans produce in the pancreas

A
  1. glucagon
  2. insulin
  3. somatostatin & GHIH - function locally to suppress both insulin & glucagon
  4. pancreatic polypeptide- regulates widespread appetite
33
Q

How do beta cells directly measure blood glucose levels

A

2 membrane channels
1. ATP sensitive potassium channel (closes when ATP is bound)
2. Voltage gated sodium channel (open when cell depolarise)

34
Q

Explain how the 2 channels in a beta cell work

A
  1. High glucose level causes it to be transported into cells by GLUT 2 receptors
  2. glucose-kinase converts glucose into glucose-6-phosphate - can enter glycolysis and kerbs cycle
  3. ATP generated binds to channels
  4. potassium can leave cells and cell become polarised
35
Q

Explain how cells respond to insulin

A
  • insulin binds to Tyrosine kinases receptors
    • binding instates single cascade
  • exocytosis of GLUT 4 receptor due to signal cascade
    • GLUT 4 contained in vesicles
  • GLUT 4 put into membrane permit glucose to enter cell
36
Q

What are hormone cell antagonist

A
  • block hormone action, not synthesis
  • doses must be titrated
37
Q

Why must hydrophillic hormones bypass the stomach

A

stomach acid peptidase and proteases enzymes

38
Q

What is Type I diabetes

A

Inuslin dependnat diease
- pancrease not producing insulin

39
Q

What is Type II diabetes

A

Blood glucose to high
- insulin resiustant diabetes
- genetic and environmental inputs
- desensitisation to inslin (pancrease still produing insulin)

40
Q

What is Hyperthyroidism

A
  • overactive metabolsim
  • too much T3/T4
  • brekaing down food into reusable energy too quickly
41
Q

What is Hypothyroidsim

A
  • underctaive metabolism
  • body stops breaking dewn food into usable energy
42
Q

What is Cushing diease

A
  • affecetd pituitary gland producing excessive ACTH
  • adrealn gland also produce excessive cortisol
  • cancer grows in adrenal glands
43
Q

What is Addisons diease

A
  • adrenal insufficiency (primary cortisol and aldosterone)
  • destruction of adrenal cortex
44
Q

How is secondary Addison diease caused

A

damage to pituitary gland

Biomedical Physiology (5 decks)

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