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Metabolism, Endocrinology, Haematology > Endocrinology Session 1 > Flashcards

Endocrinology Session 1 Flashcards

1
Q

What do homeostatic mechanisms do?

A

Counteract changes in the internal environment so that conditions remain stable.

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2
Q

What happens when homeostasis fails to happen?

A

Disease

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3
Q

What are the characteristics of a control system?*

A
  • Communication
  • Control centre
  • Receptor
  • Effector
  • Feedback
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4
Q

What is the role of communication?

A

Allows signal release (hormones) or action potentials in the nervous system. Afferent branches signal towards the brain while efferent branches signal the motor output away from the brain.

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5
Q

What is the role of the control centre?

A

Determining the reference set point, analysing the input and producing an appropriate set point.

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6
Q

What are the 2 control centres and what is their involvement?

A
  • Hypothalamus (diencephalon)
    Endocrine system control
  • Medulla oblongata (brain stem)
    Ventilation and cardiovascular system
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7
Q

What is the role of the receptor?

A
  • Required to detect stimuli
  • Specialised nerve endings (chemoreceptors/thermoreceptors/proprioceptors/nociceptors)
  • Communicate via afferent nerves
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8
Q

What is the role of the effector?

A
  • Causing change
  • Receive communication from efferent pathways
  • e.g. sweat glands
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9
Q

What is negative feedback?*

A
  • Response in a way to reverse the direction of change and bring it back to normal.
  • Overshoots set point several times until resting at the set point.
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10
Q

What is a long loop in the negative feedback system?*

A

The last released hormone can feed back on either one of the components of the pathway.

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11
Q

What is a short loop in the negative feedback system?*

A

Hormone feeding back to the first component (eg. TSH to hypothalamus to prevent release of TRH)

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12
Q

What is positive feedback?

A

Stimulus produces a response in which the effect is increased rather than counteracted. Easy to let out of control and can be catastrophic when inappropriate.

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13
Q

What are some examples of positive feedback?

A
  • Blood clotting (failure causes haemorrhaging)

- Ovulation (buildup of FSH releases oocyte)

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14
Q

What is the hypothalamic-pituitary-adrenal system?*

A
  • Hypothalamus, pituitary and adrenal glands
  • Corticotropin released from hypothalamus into local circulation
  • Binds to receptors on anterior pituitary and stimulates adenocorticotrophic hormone release (ACTH)
  • Transported to the cortex of adrenal glands
  • Binds to receptors of zona fasciculata
  • Releases CORTISOL into circulation
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15
Q

What are biological rhythms?*

A
  • Variances in the set point of the control centre during the day
  • ‘Biological clock’ is in the suprachiasmatic nucleus
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16
Q

What keeps the body on a 24-hour cycle?

A

Exogenous zeitgebers (cues from the environment)

  • Light
  • Temperature
  • Exercise
  • Social interactions
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17
Q

What hormone is responsible for setting the circadian rhythm?

A
  • Melatonin

- Released from pineal gland

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18
Q

Why are circadian rhythms clinically important?

A

Cortisol levels vary in patients throughout the day - should be taken into consideration when measuring.

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19
Q

What are the water components in the body?*

A

50-60% of lean body mass

ICF: 2/3, around 28L
ECF: 14L, divided into: 
- Interstitial fluid: 11L
- Plasma: 3L
\+ 2L of red cells to give 5L of blood.
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20
Q

How is osmotic pressure of blood plasma measured?

A

Osmoreceptors in hypothalamus

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21
Q

What is osmolaLity?

A

Numbers of osmoles per Kg of solution

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22
Q

What is osmolaRity?

A

Numbers of osmoles per L of solution

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23
Q

What is an osmole?

A

The amount of substance that dissociates in solution to form one mole of osmotically active particles (eg. 1 mM of NaCl = 2mOsm, 1 from Na and 1 from Cl)

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24
Q

What does one molar of solution contain?

A

One mole of substance in one litre.

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25
Q

What is the reference range for serum osmolality and when is it relevant?

A
  • 275-295mOsmol/kg

- Treating hyponatremia

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26
Q

What is the role of antidiuretic hormone in body fluid homeostasis?*

A
  • High level of osmolality detected so body needs to conserve water
  • Detected by osmoreceptors in hypothalamus (supraoptic and paraventricular nuclei)
  • Posterior pituitary secretes more ADH
  • Increased reabsorption of water from urine into kidney collecting ducts via more aquaporins
  • Normal osmolality returns

And vice versa.

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27
Q

Describe homeostatic control of plasma glucose*

A

Slide 10 :)

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28
Q

What is the endocrine system and what are its products?*

A
  • Collection of glands located throughout the body

- Produces hormones

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29
Q

What are hormones?

A

Chemical signals produced by endocrine glands or tissues that travel in the bloodstream to cause an effect on their target tissues.

30
Q

What are the major endocrine glands?*

A
  • Hypothalamus
  • Adrenal gland
  • Ovaries/testes
  • Thymus
  • Pineal gland
  • Hypothalamus
  • Pituitary gland
  • Thyroid
31
Q

What other organs and tissues produce hormones?

A

Heart: ANP/BNP
Liver: IGF-1
Stomach: Gastrin/ghrelin

32
Q

What is autocrine communication?

A

Hormone signal acts back on the cell of its origin.

33
Q

What is paracrine communication?

A

Hormone signal carried to adjacent cells over a short distance in the interstitial fluid.

34
Q

What is endocrine communication?

A

Hormone signal released into the bloodstream and carried to distant target cells.

35
Q

What is neurocrine communication?

A

Hormone originates in neurone, transported down axon and released into bloodstream to be carried into distant target cells.

36
Q

What are the features of the endocrine system?*

A
  • Hormone signals
  • Chemical nature
  • Conveyed in bloodstream
  • Fast
  • Via receptors
37
Q

What are the features of the nervous system?*

A
  • Signals are neurotransmitters and action potentials
  • Chemical and electrical signals
  • In synapses and axons
  • Act on receptors
  • Slow
38
Q

What are peptide/polypeptide hormones?

A
  • Short chains of amino acids

- Water soluble

39
Q

What are examples of peptide hormones?

A
  • Insulin
  • Glucagon
  • Growth hormone
40
Q

What are glycoprotein hormones?

A
  • Large protein molecules often made up of subunits
  • Have carbohydrate side chains
  • Water soluble
41
Q

What are examples of glycoprotein hormones?

A
  • Lutenising hormone
  • Follicle stimulating hormone
  • Thyroid stimulating hormone
42
Q

What are amino acid derivative hormones?

A
  • From aromatic amino acids
  • Thyroid: lipid soluble
  • Adrenal medulla: water soluble
43
Q

What are examples of amino acid derivative hormones?

A
  • Adrenaline
  • Thyroxine
  • Triiodithyronine
44
Q

What are steroid hormones?

A
  • Cholesterol derivatives

- Lipid soluble

45
Q

What are examples of steroid hormones?

A
  • Cortisol
  • Aldosterone
  • Testosterone/oestrogen
46
Q

Which hormones can be transported in the blood when dissolved in plasma?

A

Adrenaline and peptide hormones

47
Q

Which hormones bind to proteins in the blood for transport?

A

Lipophilic (steroid and thyroid)

  • Thyroid bind to thryoxine binding globulin (TBG)
  • Only FREE form biologically active
48
Q

What are the roles of carrier proteins?

A
  • Increase solubility in plasma
  • Increase half-life
  • Provide a reserve
49
Q

What determines hormone levels in the blood?

A
  • Rate of production (synthesis and secretion)
  • Rate of delivery (blood flow)
  • Rate of degradation (metabolism and excretion)
50
Q

How do hormones exert their effects?*

A
  • Bind to specific receptors

- Response in cell only if cell expresses the receptor for the hormone

51
Q

How do water soluble hormones exert their effects through GPCR?*

A
  • Alpha subunit dissociates
  • Adenylyl cyclase activated
  • Second messenger (cAMP) forms
  • PKA activated
  • PKA phosphorylates target proteins
52
Q

How do water soluble hormones exert their effects through tyrosine kinase?*

A
  • Dimerisation (2 molecules combine)
  • Autophosphorylation of specific tyrosines
  • Recruitment of adapter proteins and signalling complex
  • PKB activated
  • Target proteins phosphorylated
53
Q

What are tropic hormones?

A

Hormones which have endocrine glands as their targets.

54
Q

How do lipid soluble hormones act?*

A

Diffusing across the plasma membrane and binding to intracellular receptors

  • Bind type I/II
  • Receptor binds to specific DNA sequence (HRE/hormone receptor element)
  • Binds in the promoter region of specific genes
  • mRNA produced, so new protein and cellular response
55
Q

How do type I lipid soluble hormones act?*

A
  • Cytoplasmic receptor binds hormone

- Hormone-receptor complex enters nucleus and binds to DNA

56
Q

How do type II lipid soluble hormones act?*

A
  • Hormone enters nucleus
  • Binds to pre-bound receptor on DNA
  • Binding relieves repression of gene transcription
57
Q

What happens when energy intake = energy expenditure?

A

Body weight is stable

58
Q

What happens when energy intake > energy expenditure?

A

Energy stores/fat will increase

59
Q

What happens when energy intake < energy expenditure?

A

Energy stores deplete

60
Q

Where is the satiety centre?*

A

Hypothalamus (arcuate nucleus plays role in controlling appetite)

61
Q

What signals does the primary neurones in the arcuate nucleus process?*

A

Neuronal, nutrient and hormonal signals

  • Synapse with secondary neurones in other regions of hypothalamus
  • Signals integrated to alter feeding behaviour
62
Q

What are the stimulatory neurones?

A
  • Neurones in the arcuate nucleus
  • Contain neuropeptide Y and Agouti-related peptide
  • PROMOTE HUNGER
63
Q

What are the inhibitory neurones?

A
  • Primary neurones in the arcuate nucleus
  • Contain pro-opiomelanocortin (POMC) which yields neurotransmitters like alpha-MSH and beta-endorphin
  • PROMOTE SATIETY
64
Q

What is ghrelin and how does it act?

A
  • Peptide hormone released from stomach wall when it is empty
  • Stimulates excitatory primary neurones in arcuate nucleus
  • Stimulates appetite
  • Release inhibited when stomach full
65
Q

What is peptide tyrosine tyrosine/peptide YY?

A
  • Short peptide hormone released by cells in ileum and colon in response to feeding
  • Inhibits the excitatory neurones
  • Stimulates inhibitory neurones
  • Suppresses appetite
  • If injected into mice, makes them anorexic
66
Q

What is amylin?

A
  • Peptide hormone secreted by beta-cells in pancreas
  • Suppresses appetite
  • Slows gastric emptying
  • Decreases glucagon secretion
67
Q

What is leptin?

A
  • Peptide hormone released into blood by adipocytes
  • Stimulates POMC inhibitory neurones
  • Inhibits AgRP/NPY neurones
  • Suppresses appetite
  • Induces expression of uncoupling proteins in mitochondria
  • Energy released as heat
68
Q

What is insulin?

A

Hormone that suppresses appetite in a similar manner to leptin.

69
Q

How is appetite controlled?**

A

SLIDE 27 KEY

70
Q

What happens when some humans have a loss of leptin gene function?

A
  • Present as overweight
  • Rapid weight loss and remarkable response to leptin injection
  • Will not respond if ‘common’ obesity (leptin resistance)

Metabolism, Endocrinology, Haematology (16 decks)

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