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3MB Transition Block > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

Water balance in the body is controlled by

A

Anti-Diuretic Hormone (ADH) (aka Arginine Vasopressin)

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2
Q

ADH is produced by __________ and released by ____________

A

Hypothalamus
Posterior pituitary

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3
Q

ADH acts specifically in…..

A

Distal convoluted tubule (DCT) and collecting ducts (CD)

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4
Q

ADH acts through a ______________ to increase the transcription and insertion of ________________ to the apical membrane of the DCT and CD cells causing permeability of DCT and CD to _________

A

G-protein coupled receptor
Aquaporin–2 channels
Increase

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5
Q

Increased plasma osmolality would cause _______ release of ADH while decreased plasma osmolality would ________ ADH release

A

Increased
Decreased

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6
Q

Increase in DCT and CD permeability allows water to move ____________________, out of the nephron and back into the bloodstream, thus normalising ________________ and increasing ________________.

A

Down its concentration gradient
Plasma osmolality
Total blood volume

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7
Q

Large amount of ADH in volume leads to _____________ urine

A

Small volume of concentrated

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8
Q

Small amount of ADH in volume leads to _____________ urine

A

Large volume of diluted

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9
Q

Urine concentration/dilution measured as…

A

Urine osmolality

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10
Q

Concentrated urine has ________ osmolality while dilute urine has _______ osmolality

A

High
Low

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11
Q

Sodium balance in the body is mainly controlled by….

A

Mineralocorticoid activity of steroid

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12
Q

Mineralocorticoid activity is….

A

Na+ reabsorption in the renal tubules in exchange for K+/H+

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13
Q

Give examples of steroids with mineralocorticoid activity

A

Aldosterone (the main one)
Cortisol

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14
Q

Too much mineralocorticoid activity causes Na _______ while too little mineralocorticoid activity causes Na ______

A

Gain
Loss

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15
Q

Sodium (Na) is the most abundant cation in the _______________

A

Extracellular fluid (ECF) compartment

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16
Q

The normal plasma sodium concentration in ECF is __________, while the intracellular fluid (ICF) concentration is approximately _____________

A

135-145 mmol/L
10-12 mmol/L

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17
Q

Maintaining transmembrane concentration gradient of Na+ is necessary for……

A

Generating the resting membrane potential and for action potential propagation

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18
Q

Sodium is the main osmotic solute in the ECF, meaning that…..

A

Water travels in the direction of increasing sodium concentration via osmosis

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19
Q

Na+ intake determined by ____________ and excretion determined by _______________

A

Dietary intake and absorption in the colon and distal small bowel

Urinary excretion but also insensible losses, particularly in the sweat and faeces

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20
Q

Urinary sodium concentration is highly variable, depending on the……

A

Amount of reabsorption occurring in the nephrons

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21
Q

Majority of sodium reabsorption occurs in the…

A

Proximal Convoluted Tubule (PCT)

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22
Q

_______________________ allow for sodium reabsorption in the DCT

A

Apical Na+/Cl+ cotransporter

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23
Q

At any part in the nephron Na+ is driven across the basolateral membrane via…

A

Na-K-ATPase pumps

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24
Q

Which transporter is stimulated by aldosterone in order to increase Na reabsorption?

A

Apical ENaC in the collecting duct

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25
Q

In renal artery stenosis, there is reduced perfusion of the kidneys due to the partial arterial occlusion. Which downstream hormone would increase in quantity as a result of this?

A

Aldosterone

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26
Q

What are the 2 kinds of stimuli for ADH release

A

Osmotic → in health
Non-osmotic → in disease

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27
Q

Give examples of non-osmotic stimuli that cause ADH release

A

Hypovolaemia/hypotension
Pain
Nausea/vomiting

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28
Q

Hypotension and hypovolaemia stimulate _____________________

A

Activation of the sympathetic nervous system

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29
Q

Renal sympathetic nerve activity causes increased reabsorption of sodium in the PCT by activation of ___________________. This increases ___________, thereby ________________________, maintaining homeostasis.

A

a1 and a2 adrenoceptors
Fluid retention
Intravascular volume and blood pressure

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30
Q

Reduced renal perfusion and/or reduced sodium delivery to the nephron stimulates ________________________

A

Renin release from granular cells of the juxtaglomerular apparatus

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31
Q

Renin release leads to the production of ____________, which ____________.

A

Angiotensin II
Stimulates aldosterone secretion.

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32
Q

RAAS activation causes angiotensin II to stimulate __________________ and aldosterone to _________________

A

The Na+/H+ antiporter in the PCT
Increases the expression of ENaC in the CD

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33
Q

Raised blood volume stimulates myocytes to release ______ and _______ which promote _______________

A

ANP
BNP
Natriuresis (urinary excretion of sodium)

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34
Q

ANP and BNP act to reduce aldosterone secretion (from the adrenal glands) and renin secretion (from the juxtaglomerular apparatus), thereby _________________________

A

Decreasing sodium reabsorption in the DCT and CD

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35
Q

Addison’s caused by ___________ thus not enough _______ made so decreased ________

A

Adrenal insufficiency
Steroids
Mineralocorticoid

36
Q

Decreased mineralocorticoid activity in Addisons causes kidneys to be unable to _______ thus Na is loss from _______ decreasing the _______ volume meaning the patient is clinically dehydrated

A

Retain enough sodium
ECF
ECF

37
Q

Why do patients with Addisons have excess pigmentation

A

Excess pigmentation reflects excess ACTH from pituitary

ACTH molecule contains sequence for MSH within it

ACTH is degraded by proteases eventually exposing MSH

38
Q

ADH secreted in response to non-osmotic stimulus causes slow ___________ that is distributed over _________________ so patients clinical volume status is remarkable

A

Water retention
All body compartments (ICF as well as ECF)

39
Q

Diabetes insipidus is a….

A

Disruption of pituitary or pituitary stalk so ADH not secreted from posterior pituitary

There is no ADH to act on kidneys to cause water to be reabsorbed

Lots of pure water lost in urine so [Na] is high reflecting the H20 deficit

40
Q

In diabetes insipidus, there is no…

A

ADH to act on kidneys to cause water to be reabsorbed

41
Q

Mx of diabetes insipidus

A

Exogenous ADH (desmopressin) to replace ADH that the pituitary can’t make/release

42
Q

Pituitary gland function is regulated by the _________ which is connected to it via the _________

A

Hypothalamus
Pituitary stalk

43
Q

Pituitary stalk comprises of the….

A

Portal blood capillaries and nerve fibres

44
Q

What are the anterior pituitary hormones?

A

TSH (Thyroid Stimulating Hormone)
ACTH (Adrenocorticotrophic Hormone)
LH (Luteinising Hormone)
FSH (Follicle stimulating hormona)
GH (Growth hormone)
Prolactin

45
Q

What are the posterior pituitary hormones?

A

ADH
Oxytocin

46
Q

Function of TSH

A

Act on the thyroid gland to elicit secretion of thyroid hormones

47
Q

Function of ACTH

A

Acts specifically on the adrenal cortex to elicit secretion of cortisol

48
Q

Function of LH and FSH

A

Act cooperatively on the ovaries in women and the testes in men to stimulate sex hormone secretion and reproductive processes

49
Q

Function of GH

A

Acts directly on many tissues to modulate metabolism

Metabolic fuels (e.g. glucose, free fatty acids) in turn modify GH secretion

50
Q

Function of prolactin

A

Acts directly on the mammary glands to control lactation

Gonadal function is impaired by elevated circulating prolactin concentrations

51
Q

Prolactin release is inhibited by _______ while its release is most strongly stimulated by_________

A

Dopamine aka PRL-inhibitory factor (PIF)
Suckling

51
Q

Prolactin (PRL) is produced by the ___________ of the anterior pituitary gland

A

Lactotroph cells

52
Q

Causes of hyperprolactinoma

A

Stress
Drugs
Seizures
Primary hypothyroidism
Prolactinoma
Idiopathic hypersecretion

53
Q

Idiopathic hypersecretion of prolactin can be identified through….

A

A rise in serum prolactin following administration of TRH or metoclopramide

54
Q

Serum potassium concentration is usually kept within….

A

3.5-5.3 mol/L

55
Q

T or F: Potassium loses mirror potassium intake

A

True

56
Q

Which 2 factors are important in determining potassium excretion

A

Glomerular filtration rate
Plasma potassium concentration

57
Q

Severe hyperkalaemia defined as…

A

> 7.0 mmol/L

58
Q

What can cause hyperkalaemia in the body

A

Decreased excretion of Na+
Increased intake of Na+
Redistribution of Na+ out of cells

59
Q

Where is potassium most reabsorbed in the body?

A

Proximal Convoluted Tubule

60
Q

Which channel is mainly responsible for potassium reabsorption in the thick ascending limb?

A

NKCC2 transporter

61
Q

Which channel is mainly responsible for reabsorption of Potassium from the lumen into the cell in the distal convoluted tubule?

A

H+-K+-ATPase

62
Q

Which channel is mainly responsible for the transportation of potassium ions into the cell from the bloodstream in the late distal convoluted tubule and collecting duct?

A

Sodium-Potassium ATPase

63
Q

What is the mechanism of the NKCC2 cotransporter in the nephron?

A

It pumps Na+, K+ and 2Cl- into the cell from the lumen

64
Q

What effect do renal outer medullar K+ (ROMK) channels have on K+ in the nephron?

A

Allow for movement of K+ into the lumen by creating a positive voltage which provides a driving force for the passive reabsorption of K+

65
Q

Which metabolic abnormality is seen as a consequence of potassium depletion?

A

Hypokalaemia alkalosis

66
Q

ECG changes seen with hyperkalaemia

A

Tall tented T waves
Widening of the QRS complex
Increased PR interval
Flattened/absent P waves

67
Q

What can cause decreased excretion of potassium

A

Renal failure
Hypoaldosteronism → e.g. Addison’s disease

68
Q

High tubular K+ concentration stimulates _________________ which leads to an __________ of K+ channel on apical membrane. This results in an ___________ of K+ into the lumen

A

Na+/K+-ATPase
Increased permeability
Increased secretion

69
Q

____________ stimulates ____________ in the basolateral membrane which stimulates ____________ & ____________ in the apical membrane, leading to increased K+ secretion.

A

Aldosterone
Na+/K+-ATPase
K+ channels & ENaCs

70
Q

What can cause redistribution of potassium out of cells

A

Metabolic acidosis
Potassium released from damaged cells
Insulin deficiency
Psudohyperkalaemia
Hyperkalaemic periodic paralysis

71
Q

Redistribution of K+ causes…

A

H+ is reabsorbed into the cells to try and decrease the pH, so K+ is excreted to maintain electrical equilibrium thus causing hyperkalaemia

72
Q

What effect will alkalosis have on K+ in the extracellular fluid (ECF)?

A

Decrease in the concentration of K+ in the ECF

73
Q

Where does insulin act in order to exert its effect on potassium levels in the blood?

A

Na+/K+-ATPase

74
Q

Clinical features of hypothyroidism

A

Lethargy / tiredness
Weight gain
Cold intolerance
Dryness and coarseness of skin and hair
Constipation
Bradycardia
Subfertility
Galactorrhoea

75
Q

Causes of hypothyroidism

A

Autoimmune destruction of the thyroid gland (Hashimoto’s disease)
Radioiodine or surgical treatment of hyperthyroidism
TSH deficiency
Congenital defect
Iodine deficiency

76
Q

Primary hypothyroidism is the…

A

Failure of the thyroid gland itself

77
Q

T or F: The demonstration of an elevated TSH concentration is usually diagnostic of primary hypothyroidism

A

True

78
Q

How to differentiate between primary and secondary hyperlipidaemia

A

Primary → Not due to an identifiable underlying disorder
Secondary → Disorder is the manifestation of some other disease

79
Q

Thyroid gland is responsible for…

A

Regulating the body’s metabolic rate via hormones it produces

79
Q

Metabolic processes increased by thyroid hormones include….

A

Basal Metabolic Rate
Gluconeogenesis
Glycogenolysis
Protein synthesis
Lipogenesis
Thermogenesis

80
Q

How does thyroid glands increase metabolic processes

A

Increasing the size and number of mitochondria within cells

Increasing Na-K pump activity

Increasing the presence of β-adrenergic receptors in tissues such as cardiac muscle

81
Q

What are the steps of thyroid hormone synthesis (ATE ICE)

A

Active transport of iodide into follicular cell

Thyroglobulin is formed in follicular ribosome

Exocytosisof thyroglobulin into the follicle lumen

Iodination of the thyroglobulin

Coupling of MIT and DIT

Endocytiosis of iodinated thyroglobulin back into follicular cell

82
Q

T or F: T3 and T4 are fat soluble

A

True

83
Q

T3 and T4 are mostly carried by…

A

Thyronine binding globulin (TBG) and albumin → which are plasma proteins

84
Q

What are the effects of cortisol?

A

Immunosuppression
Anti-inflammatory
Protein and afat metabolism
Regulate mood, behaviour and cognition
Lipolysis in adipose tissue
Increase plasma glucose by breaking proteins into amino acids
Stimulate gluconeogenesis in the liver
Bone metabolism
Regulate calcium absorption from GI tract

85
Q

Cortisol MoA

A

Binds intracellularly to the glucocorticoid receptor (GR) in the cytoplasm

3MB Transition Block (10 decks)

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