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Physiology 1 : GI > Consequences of loss of fluid from GI > Flashcards

Consequences of loss of fluid from GI Flashcards

1
Q

What are the sites of water loss?

A 
→Skin 
→Respiratory passageways
→GIT
→Urinary tract
→Trauma 
→Menstrual flow
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2
Q

What is the daily NaCl intake?

A

→ 10.5g in food

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3
Q

What 2 things cause water to be gained?

A

→ Drinking

→metabolism

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4
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

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5
Q

Why does diarrhoea occur?

A

→Failure of water absorption

→Increased secretion of both

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6
Q

What are the causes of decreased absorption?

A

→Increased number of osmotic particles
→Increase in rate of flow of intestinal contents (deranged motility diarrhoea)
→Abnormal increase in secretions of GIT (secretory diarrhoea)

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7
Q

What is the cause of osmotic diarrhoea?

A

→decreased absorption of electrolytes and nutrients
→Disaccharidase deficiency
→drug induced
→malabsorption of galactose

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8
Q

What increases the rate of secretion in secretory diarrhoea?

A

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

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9
Q

What causes secretory diarrhoea?

A

→Excessive laxative use, defects in digestion and absorption (infections eg. Cholera)
→Enterotoxin stimulates adenylate cyclase increases cAMP causes Na+ and Cl- and water loss.

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10
Q

What causes traveller’s diarrhoea?

A

→ Bacteria

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11
Q

What causes chronic exudative diarrhoea?

A

→ Inflammatory bowel disease

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12
Q

What causes deranged motility diarrhoea?

A

→ lack of absorption

→some agents promotes secretion as well as motility

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13
Q

Why can GI stasis promote diarrhoea?

A

→stimulating bacterial growth

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14
Q

What are the two parasites that cause diarrhoea?

A

→Entamoeba histolytica

→Giardia lamblia

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15
Q

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

A

→asymptomatic dysentery

→ Metronidazole

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16
Q

What does giardia cause?

A

→Steatorrhea and abdominal pain

→Maldigestion and malabsorption of lipids, CHOs, vitamin A, vitamin B12, folic acid

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17
Q

What does dysentery cause?

A

→painful
→ bloody
→low volume diarrhoea

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18
Q

What are the consequences of severe diarrhoea?

A

→loss of water, nutrients, Na+, K+ and HCO3-
→Decreased blood volume (hypovolaemia)
→Metabolic acidosis - due to loss of HCO3-

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19
Q

What are the consequences of excessive vomiting?

A 
→Increased salt and water loss
→Severe dehydration
→Circulatory problems 
→Metabolic alkalosis - due to loss of gastric acid HCl 
→Death
20
Q

What is lost in vomit?

A 
→food
→ mucus 
→Na+
→ K+
→ Cl-
→ HCO3-
→ gastric acid
→upper intestinal contents (bile)
→ blood
21
Q

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

A

→Hypovolaemia
→Haemoconcentration/polycythaemia (dehydration) →Increased RBC
→Dehydration
→Ionic imbalances : poor perfusion of tissues
→Malnutrition and increase in mortality

22
Q

What are the consequences of hypovolaemia?

A

→Decreased venous return
→Arterial hypotension
→Myocardial dysfunction due to increased myocardial oxygen demand but tissue perfusion is reduced
→Increased anaerobic metabolism → to acidosis
→Acidosis and myocardial dysfunction → multi organ failure

23
Q

What are the consequences of dehydration?

A 
→Nausea
→headache
→ irrationality
→cramps
→increased temperature
→dizziness
24
Q

What is the bodys response to water loss?

A

→Cardiovascular adaptation
→Renal adaptation
→Behavioral and this stimulates fluid intake when possible

25
Q

What does the renal system do in response to hypervolaemia?

A

→Increased sodium and water loss due to diarrhoea
→Plasma volume decreases
→Venous volume decreases
→Increased activity of the renal sympathetic nervous system
→Increased constriction of renal arterioles
→GFR decreases
→Allows more time for reabsorption to occur if there is water present
→Decreased Na+ and water secretion
→Blood volume increases

26
Q

What are the cardiovascular effects of hypervolaemia?

A

→The decreased venous return
→Decreases atrial pressure
→Decreased ventricular end diastolic volume
→Stroke volume reduces
→Cardiac output reduces
→Arterial blood pressure reduces
→These effects stimulate the sympathetic nervous renal system

27
Q

What happens during severe sweating?

A

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

28
Q

Describe how decreased blood volume can cause the RAAS cascade?

A

→Decreased plasma volume
→Decreased GFR and decreased flow to Macula Densa
→Decreases the arterial pressure
→This has a direct effect on the stretch receptors
→Stimulates an increase in renin secretion
→Increased plasma renin generates angiotensin II
→Plasma aldosterone secretions increase from adrenal cortex
→Sodium reabsorption increases
→Water reabsorption increases
→Plasma volume increases

29
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

30
Q

What can the RAAS cascade be triggered by?

A

→The RAAS cascade can be triggered by increased K+ concentration and decreased plasma volume.

31
Q

How does increased water reabsorption occur?

A

→Decreased plasma volume

→Decreased venous, atrial and arterial blood pressure

→These reflexes are mediated by cardiovascular baroreceptors

→The osmolarity increases

→Osmoreceptors are stimulated

→Hypothalamus causes the secretion of vasopressin

→Plasma levels increase

→Vasopressin stimulates its receptors on the collecting tubules and insert channels ‘aquaporin 2’

→Increased water reabsorption and decreased excretion

32
Q

How is thirst stimulated?

A 
→Hyperosmolarity occurs
→Decreases plasma volume 
→Baroreceptors are stimulated 
→Increases angiotensin II levels 
→This stimulates thirst 
→And stimulates ADH/vasopressin  release
33
Q

What does dehydration lead to?

A

→imbalance of electrolytes in the bloodstream (decreased NaCl and K+ but also increase in Ca2+)

34
Q

What does an increase in Ca2+ cause?

A

→ Hypercalcaemia

35
Q

What does hypercalcaemia cause?

A

→increased risk of kidney stone
→ kidney failure
→ dementia
→arrhythmia

36
Q

What are the symptoms of hypercalcaemia?

A 
→Nausea
→Vomiting
→Loss of appetite
→Constipation
→Abdominal pain
→Excessive thirst 
→Fatigue,lethargy, muscle weakness
→Joint pain and confusion
37
Q

What does ADH stimulate?

A

→Vasopressin (ADH) - stimulates thirst mechanism

38
Q

What leads to ADH release?

A

→Increased osmolarity of body fluids leads to ADH release

39
Q

How does ADH work?

A

→ADH activates the V2 receptors on the renal collecting ducts
→Inserts water channels (aquaporin 2) in collecting duct of kidney
→This increases the permeability of the collecting ducts to H2O and results in concentrated urine production

40
Q

What does the intake of plain H2O do?

A

→Intake of plain H2O leads to a decrease in osmolarity of the blood and interstitial fluid
→This decreases the ADH secretion and the removal of water channels

41
Q

What happens if there are no water channels?

A

→decreased permeability of collecting ducts to water and increased water loss

42
Q

What are the 5 factors that regulate ADH release?

A

→Large decrease in blood volume (detected by baroreceptors)
→2.Severe dehydration: under this condition, GFR decreases causing less H2O in urine
→3.Hyperventilation: results in increased fluid loss (exhalation)
→4.Vomiting/diarrhoea: causes increased fluid loss from GIT
→5.Fever, heavy sweating, and burns cause large H2O loss

43
Q

What does the thirst center in the hypothalamus do?

A

→ Stimulate the desire to drink

44
Q

What does angiotensin II do?

A

→ Stimulate the release of aldosterone 2

45
Q

What does aldosterone do?

A

→ Promotes reabsorption of Na+, Cl- and H2O

Physiology 1 : GI (15 decks)

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