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SGUL - Physiology 1 > Blood Pressure And Kidneys > Flashcards

Blood Pressure And Kidneys Flashcards

1
Q

What is the relationship between salt intake (Na) and blood pressure?

A

The higher the Na intake , the higher the blood pressure.

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2
Q

Why are Na levels linked to blood pressure? PART 1

A
  • Na is the major electrolyte of the extracellular fluid volume (ECFV).
  • Increased blood volume leads to ventricular filling and increased stroke volume.
  • Stroke volume is a major determinant of cardiac output.
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3
Q

Why are Na levels linked to blood pressure? PART 2

A

Regulating Na levels affects blood volume, which makes it a long-term control of blood pressure.

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4
Q

How does the CVS control Na levels? PART 1

A
  • change in Na+ intake so change in ECFV
  • activates afferent pathways (such as cardiac volume receptors, baroreceptors, renal arterial pressure)
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5
Q

How does the CVS control Na levels? PART 2

A
  • activates efferent pathways (neuronal, such as the sympathetic nervous system, hormonal, such as RAAS or ANP, or haemodynamic: changing GFR, pressure natriuresis)
  • changes renal Na+ output
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6
Q

How does the RAAS affect Na levels in the blood?

A
  • Aldosterone causes water retention in the kidney by reabsorbing more Na+ back into circulation.
  • Increased RAAS activity, increased Na reabsorption.
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7
Q

List some factors that stimulate renin release.

A
  • decreased BP and decreased renal blood volume
  • decreased Na levels in the macula densa
  • sympathetic nerve activation of β1 adrenoreceptors
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8
Q

Describe the role of aldosterone in the kidney.

A
  • Acts at steroid receptors inside cells
  • Increases the expression of ENaC and the Na/K pump.
  • Increases Na reabsorption at distal tubular sites so increased renal K excretion.
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9
Q

What is the result of excess aldosterone and why?

A

Hypokalaemia.
→ K+ into the cell via Na+/K+ pump
→ K+ passively diffuses out of the cell into the lumen of tubule

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10
Q

Summarise the renal effects of ANP.

A
  • natriuresis (increased Na excretion)
  • diuresis (increased water excretion)
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11
Q

Summarise the vascular effects of ANP.

A

Vasodilation by the stimulation of PKG in vascular smooth muscle cells, decreasing systemic BP

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12
Q

Summarise the hormonal effects of ANP

A

decreases renin and aldosterone secretion

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13
Q

What system does ANP oppose?

A

RAAS

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14
Q

Describe pressure natriuresis.

A
  • Rise in medullary capillary pressure
  • Increases fluid filtration and interstitial pressure
  • Prevents tubular reabsorption.
  • Increase in renal Na+ excretion due to a rise in renal arterial pressure
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15
Q

Why does GFR not increase during natriuresis?

A

Renal arterial pressure doesn’t increase GFR
- Due to autoregulation

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16
Q

What is the clinical importance of the control of blood pressure by the kidney?

A

If uncontrolled, can cause hypertension

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17
Q

When is hypertension present?

A
  • Systolic pressure > 140 mmHg
  • Diastolic pressure is > 90 mmHg.
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18
Q

What are the two types of hypertension?

A
  • Primary/ essential (unknown cause, > 90% of the cases)
  • Secondary (identifiable cause, 5-10% of cases),
19
Q

What are some secondary causes of hypertension?

A
  • excess renal Na re-absorption
  • Liddle’s Syndrome
  • Conn’s Syndrome
  • renal artery stenosis
20
Q

What may essential hypertension involve?

A

Abnormal handling of Na+ balance

21
Q

What is Liddle’s Syndrome?

A

Genetic form of high blood pressure associated with the epithelial Na+ sodium channel (ENaC)

22
Q

How does Liddle’s Syndrome lead to hypertension?

A
  • increases ENaC activity
  • increases renal Na retention
  • suppresses renin/aldosterone
23
Q

What is Conn’s Syndrome?

A

Overproduction of aldosterone by an adrenal gland tumour (adenoma)

24
Q

How does Conn’s Syndrome lead to hypertension?

A
  • increased renal Na reabsorption, due to increased ENaC
  • increased ENaC increases Na/K ATPase, which increases K excretion
  • ECFV expansion, which decreases renin secretion
25
Q

How does Addison’s Disease affect blood pressure?

A
  • Insufficient release of aldosterone
  • Chronic Na loss.
  • Large decrease in ECFV
  • Causes severe hypotension
26
Q

Describe renal artery stenosis.

A

Abnormal narrowing of the vessel.

27
Q

How does renal artery stenosis affect hypertension?

A
  • Decrease in renal artery pressure
  • Decreases blood flow.
  • Stimulates renin secretion, which stimulates Angiotensin II production.
  • Angiotensin II increases aldosterone and vasoconstriction
  • Leads to Na retention and high blood pressure.
28
Q

Describe factors thay may lead to essential hypertension.

A
  • Genetic predisposition
  • Environmental factors (such as lifestyle: exercise, diet: salt intake, alcohol, diabetes)
29
Q

Equation for BP?

A

CO x TPR

30
Q

What is short term control of blood pressure?

A

Baroreceptors

31
Q

How does sodium balance affect ADH?

A
  • Changes in osmolarity
  • ADH release
  • H2O moves through ADH stimulated aquaporin channels in collecting duct
32
Q

Why does resuscitation fluid not cause hypernatremia?

A

→ It is isotonic
→ Na+ cannot cross cell membranes
→ fluid will expand the ECFV

33
Q

What is the effect of retained sodium the same as?

A

→ adding isotonic fluid
→ It draws an equivalent amount of water with it
→ Increase in blood pressure

34
Q

How is Na+ sensed in the body?

A

→ A change in ECFV occurs
→ Stretch and pressure receptors in CVS detect this

35
Q

How is sodium removed from the body?

A

→ Sweat/faeces
→ Regulated renal excretion

36
Q

What are mammals designed to do with Na+?

A

Conserve it

37
Q

Where is the macula densa?

A

Region of contact between the afferent arteriole and the distal tubule of the same nephron

38
Q

What are renin-secreting juxtaglomerular cells?

A

Modified smooth muscle cells along the afferent arteriole

39
Q

What is aldosterone and where is it synthesized and what is it released by?

A

→ Steroid hormone
→synthesized in the zona glomerulosa of the adrenal gland
→ released by the action of angiotensin II

40
Q

Where does aldosterone act?

A

→ Nuclear receptors mainly on DCT cells

41
Q

How does the Na+/K+ pump work to retain Na+?

A

→ Na+/K+ pump actively pumps sodium out
→ Low intracellular concentration of Na+
→ creates a diffusion gradient from the lumen of the tubule of the DCT
→ Na+ diffuses in via the eNAC
→ Na+ does not stay in the cell because the Na+/K+ pump is taking the Na+ out

42
Q

Where is ANP found?

A

Specialised cardiac myocytes

43
Q

What is ANP released in response to?

A

→ Increased cardiac filling pressures

44
Q

What is the relationship between pressure and Na+ excretion?

A

→ The higher the pressure the higher the concentration of Na+ in the urine

SGUL - Physiology 1 (68 decks)

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