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SGUL - Physiology 1 > Fluid Loss from GI Tract > Flashcards

Fluid Loss from GI Tract Flashcards

1
Q

List some ways in which water is lost in the body.

A
  • defecation, diarrhoea
  • vomiting
  • urination
  • ventilation
  • sweating
  • menstruation
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2
Q

List some different types of diarrhoea.

A
  • OSMOTIC DIARRHOEA
  • SECRETORY DIARRHOEA
  • TRAVELLER’S DIARRHOEA
  • CHRONIC EXUDATIVE DIARRHOEA
  • DERANGED MOTILITY DIARRHOEA
  • PARASITIC CAUSE OF DIARRHOEA
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3
Q

What is osmotic diarrhoea caused by?

A

Decreased absorption of electrolytes and nutrients
→Disaccharidase deficiency
→drug induced

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4
Q

What is secretory diarrhoea caused by?

A
  • Increased secretion of ions from crypt cells
  • Electrolyte absorption is impaired
    →Excessive laxative use, defects in digestion and absorption (infections eg. Cholera)
    →Enterotoxin stimulates adenylate cyclase, increases cAMP and causes Na+ and Cl- and water loss.
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5
Q

What is traveller’s diarrhoea caused by?

A

Bacteria

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6
Q

What is chronic exudative diarrhoea caused by?

A

Inflammatory bowel disease

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7
Q

What is deranged motility diarrhoea caused by?

A
  • Motility of the SI increases
  • Less time for absorption
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8
Q

What is parasitic diarrhoea caused by?

A

Parasites such as Entamoeba histolytica and Giardia lamblia

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9
Q

What is dysentery?

A

Painful, bloody, low volume diarrhoea

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10
Q

Bloody diarrhoea is a cause for concern.

What are some of the causes?

A
  • chronic disease
  • ulcerative colitis
  • neoplasm ( SERIOUS - characteristic of cancer)
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11
Q

What are the consequences of excessive vomiting?

A
  • hyponatremia
  • hypovolemia
  • metabolic alkalosis (due to H+ loss)
  • death
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12
Q

What are the symptoms of excessive vomiting caused by?

A

Loss of water and nutrients

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13
Q

What is lost in vomit?

A
  • food
  • mucus with Na+, K+, Cl-, HCO3-
  • gastric acid
  • in extreme cases, blood
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14
Q

What can trigger damage to intestinal cells in cancer patients?

A

Chemotherapy and radiotherapy

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15
Q

How does serotonin induce vomiting?

A
  • Trigger causes the release of serotonin
  • Serotonin transmits the vomit signal via nerves from the intestines to the brain
  • Stimulates the vomiting centre and induces vomiting.
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16
Q

How can vomiting be averted?

A

Blocking site of action of 5-HT receptors ∴ blocks action of serotonin

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17
Q

What are the consequences of hypovolemia?

A
  • decreased venous return
  • arterial hypotension
  • myocardial dysfunction due to increased myocardial oxygen demand and decreased tissue perfusion
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18
Q

What physiological process causes hypovolemic patients to have acidosis?

A

Anaerobic metabolism

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19
Q

What can acidosis and myocardial dysfunction cause in hypovolemic patients if left untreated?

A

Multiple organ failure

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20
Q

What is the body’s response to water loss?

A
  • aldosterone is released (decreasing sodium excretion)
  • vasopressin is released (decreasing water excretion)
  • cardiovascular and renal adaptations
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21
Q

What effect does dehydration have on calcium levels in the body?

A

Increases calcium levels

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22
Q

What are some symptoms of hypercalcaemia? PART 1

A
  • nausea
  • vomiting
  • loss of appetite
  • constipation
23
Q

What are some symptoms of hypercalcaemia? PART 2

A
  • abdominal pain
  • excessive thirst
  • fatigue, muscle weakness
  • confusion
24
Q

What hormone regulates water loss?

A

ADH

25
Q

What stimuli causes ADH release?

A

Increased osmolarity of body fluids

26
Q

How does ADH work?

A
  • Inserts water channels (aquaporin-2) in collecting ducts of kidney tubules.
  • Increases the permeability of the collecting ducts to H2O
  • Concentrated urine production.
27
Q

What occurs when a patient takes in plain water?

A
  • Decreased blood osmolarity
  • Reduced ADH secretion
  • Removal of water channels
28
Q

What is the consequence of having no water channels in the collecting ducts?

A
  • Decreased permeability of the collecting ducts to water
  • Increased water loss.
29
Q

List some factors that regulate ADH release. With each factor, give a brief reason why. PART 1

A
  • large decrease in blood volume (detected by baroreceptors)
  • severe dehydration - GFR decreases. Reduced water in urine
  • greater water intake: results in high BP which causes increased GFR and increased H2O in urine
30
Q

List some factors that regulate ADH release. With each factor, give a brief reason why. PART 1

A
  • hyperventilation: results in an increased fluid loss (exhalation)
  • vomiting/diarrhoea: causes increased fluid loss from GIT
  • fever, heavy sweating and burns cause large H2O loss
31
Q

What is diarrhoea and what is the criteria for it?

A
  • Increased frequency with increased volume and fluidity of feces
  • 3 unformed stools per 24 hrs
32
Q

Why does diarrhoea occur?

A

Failure of water absorption

33
Q

What are the causes of decreased absorption?

A

→Increased number of osmotic particles
→Increase in rate of flow of intestinal contents
→Abnormal increase in secretions of GIT

34
Q

What increases the rate of secretion in secretory diarrhoea?

A

ACh, substance P, 5-HT and neurotension act via an increase in Ca2+

35
Q

Why can GI stasis promote diarrhoea?

A

→stimulating bacterial growth

36
Q

What condition does entamoeba cause and what is the treatment for it?

A

→asymptomatic dysentery
→ Metronidazole

37
Q

What are the consequences of fluid loss in the GI tract?

A

→Hypovolemia
→Polycythaemia
→Ionic imbalances : poor perfusion of tissues

38
Q

What are the consequences of dehydration?

A

→Nausea
→headache
→cramps
→dizziness

39
Q

What does the renal system do in response to hypervolaemia? PART 1

A

→Increased sodium and water loss due to diarrhoea
→Plasma and venous volume decreases
→Increased activity of the renal sympathetic nervous system
→Increased constriction of renal arterioles

40
Q

What does the renal system do in response to hypervolaemia? PART 2

A

→GFR decreases
→Decreased Na+ and water secretion
→Blood volume increases

41
Q

What are the cardiovascular effects of hypervolaemia? PART 1

A

→Decreased venous return
→Decreases atrial pressure
→Decreased ventricular EDV
→Stroke volume reduces

42
Q

What are the cardiovascular effects of hypervolaemia? PART 2

A

→Cardiac output reduces
→Arterial blood pressure reduces
→These effects stimulate the sympathetic nervous renal system

43
Q

What happens during severe sweating? PART 1

A

→Severe sweating decreases the osmotic salt solution
→Plasma volume decreases
→GFR decreases and plasma osmolarity increases
→This stimulates osmoreceptors in the hypothalamus

44
Q

What happens during severe sweating? PART 2

A

Increase the plasma vasopressin concentration (ADH)
→Plasma aldosterone levels increase due to RAAS system
→ADH inserts water channels within the collecting duct of the tubules and decreased water secretion occurs as it takes up more water

45
Q

Describe how decreased blood volume can cause the RAAS cascade. PART 1

A

→Decreased plasma volume
→Decreased GFR
→Decreases the arterial pressure
→This has a direct effect on the stretch receptors
→Stimulates an increase in renin secretion

46
Q

Describe how decreased blood volume can cause the RAAS cascade. PART 2

A

→Increased plasma renin generates angiotensin II
→Plasma aldosterone secretions increase from adrenal cortex
→Sodium reabsorption increases
→Water reabsorption increases
→Plasma volume increases

47
Q

What is the response to increased K+ concentration?

A

→A decrease in plasma volume
→Increase plasma angiotensin II
→Increased aldosterone from the renal cortex
→Sodium reabsorption increases so sodium excretion decreases
→Water is retained
→Increased K+ excretion

48
Q

What can the RAAS cascade be triggered by?

A

Increased K+ concentration and decreased plasma volume.

49
Q

How does increased water reabsorption occur? PART 1

A

→Decreased plasma volume
→Decreased venous, atrial and arterial blood pressure
→The osmolarity increases
→Osmoreceptors are stimulated
→Hypothalamus causes the secretion of vasopressin

50
Q

How does increased water reabsorption occur? PART 2

A

→Plasma levels increase
→Vasopressin stimulates its receptors on the collecting tubules and insert channels ‘aquaporin 2’
→Increased water reabsorption and decreased excretion

51
Q

How is thirst stimulated?

A

→Hyperosmolarity occurs
→Decreases plasma volume
→Baroreceptors are stimulated
→Increases angiotensin II levels
→This stimulates thirst

52
Q

What does angiotensin II do?

A

→ Stimulate the release of aldosterone

53
Q

What does aldosterone do?

A

→ Promotes reabsorption of Na+, Cl- and H2O

SGUL - Physiology 1 (68 decks)

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