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Semester 2 (1st year) > Wk 17 > Flashcards

Wk 17 Flashcards

1
Q

What are the normal routes of fluid intake into the body? (and their values)

What are the normal routes of fluid loss from the body? (and their values)

A

Oral + Metabolic = 2500mL/ day

Faeces= 200 mL
Sweat= 100mL
Urine= 1400mL
Insensible loss= 800mL

Output comes to about 2500mL as well

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2
Q

Where is B12 absorbed?

A

Large Intestine

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3
Q

There’s more fluid secreted into the GIT than absorbed (more absorbed in the SI but in the LI it mostly absorbs water), where does the fluid that is lost go into?

A

Faeces

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4
Q

What reflex allows some discrimination of the rectal contents and prevents unexpected voiding?

A

Anal sampling reflex

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5
Q

What are the 3 most common causes of faecal incontinence?

A

Structural anorectal abnormalities (sphincter trauma or fistula etc)

Neurological disorders (spinal cord injury, MS)

Altered bowel habits (diarrhoea, IBD, drugs)

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6
Q

What are the 3 main types of diarrhoea?

A

Secretory

Osmotic

Exudative/ inflammatory

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7
Q

What are the causes of secretory diarrhoea? 4

A

Bacteria like cholera (Cl- pumped into lumen)

Some laxitives (castor oil- increase intestinal secretion)

Some drugs (caffeine increases intestinal secretion)

Neuroendocrine tumours (particularly carcinoma of pancreatic islets because large amounts of VIP enhance intestinal secretion)

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8
Q

What are the main causes of osmotic diarrhoea? 2

A

Ingestion of a non-absorbable molecule

Malabsorption

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9
Q

What are the main causes of exudative diarrhoea? 2

A

Infections (ebola, e.coli, salmonella)

IBD

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10
Q

What is the term for when someone has blood associated with diarrhoea?

A

Dysentery

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11
Q

What is the term for the passage of fresh blood through the anus (associated with lower GIT bleeding- haemmorhoids or diverticulitis)?

A

Heamatochezia

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12
Q

What is the term for blood noticed on the toilet paper? (associated with anal fissures or haemmorhoids)

A

Haematopapyrus

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13
Q

What are the 2 centres in the brain that control the vomiting reflex?

A

1) Vomition centre (neural pathway)

2) Chemoreceptor trigger zone (humoral pathway)

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14
Q

Where is the vomition centre?

Where does it receive information from?

A

Medulla

Receives info from

  • CTZ
  • Visceral afferents from GIT (irritation, GIT distention)
  • Visceral afferents from other organs (bile duct or heart)
  • Afferents from other centres in the brain (odours, fear, vestibular disturbance- motion sickness)
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15
Q

Where is the CTZ?

Is it inside or outside BBB?

The chemoreceptors here detect multiple chemical emetic stimuli such as…

What happens after CTZ is excited?

A

Within the brainstem, just under floor of 4th ventricle

Outside blood brain barrier

Emetic drugs (ipecac)
Uremia
Ketoacidosis
Hypoxia

Excitatory signals are then forwarded to vomition centre

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16
Q

What are the 2 main electrolytes that are outside cells?

What are 4 electrolytes that are inside cells?

A

Outside= Na and Cl (salty outside)

Inside= K, Mg, Phosphate, Sulphate

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17
Q

What is an isotonic solution (in relation to a cell)

A

When movement of water into and out of cell is the same

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18
Q

What is a hypotonic solution (in relation to ECF of a cell)

What is a hypertonic solution (in relation to ECF of a cell)

A

When ECF is hypotonic, the conc of solutes is higher inside the cell so water moves into cell= cell swells

When ECF is hypertonic, the conc of solutes is higher outside the cell so water leaves the cell and it shrinks

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19
Q

What is dehydration in relation to ECF and cells?

A

Excessive loss of water from ECF –> Solute conc is higher in ECF than cells [hypertonic solution] –> water leaves cells to go out into ECF by osmosis –> cells shrink

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20
Q

What is osmolarity?

What is osmolality?

A

The conc of a solution (expressed as total number of solute particles per litre of solution Osm/L)

The conc of a solution (expressed as the total number of solute particles per kg of solvent Osm/kg)

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21
Q

What is the most abundant ion in ECF and main determinant of plasma osmolality?

What 3 functions does it regulate?

A

Sodium!

It regulates heart, nerve and muscle functions

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22
Q

What is the osmotic shift when there is hyponatraemia?

What are the 3 main causes of hyponatraemia?

A

Low blood sodium means there is an osmotic shift from the ECF to the ICF

Vomiting/ diarrhoea
Kidney excretion
Drinking too much water

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23
Q

What is the major ICF ion?

A

Potassium!

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24
Q

What is the main hormonal control of K?

A deficiency in this hormone leads to what?

A

Aldosterone (tells kidneys to excrete K)

Hyperkalaemia

25
Q

How does acidosis affect K?

How does alkalosis affect K?

A

Acidosis causes a shift of K+ ions from ICF to ECF (in exchange for H+ ions)== hyperkalaemia

Alkalosis causes a shift of K+ into cell so more H+ can be released= hypokalaemia

26
Q

What are the main 2 ions in gastric juice?

A

Na and Cl

27
Q

What is transcellular movement of water and electrolyte absorption and secretion through GIT?

What is paracellar?

A

Transcellular is through cells and water channels (aquaporins)

Paracellular is between cells through tight junctions

28
Q

Tight junctions are looser where and tighter where?

A

Looser in the upper SI and tighter in lower SI and colon

29
Q

How does diarrhoea affect bicarb?

A

Massive loss of HCO3- in diarrhoea so cells GIT cells secrete HCO3- in lumen which leads to low HCO3- in blood which leads to acidosis

30
Q 
Blood analysis in patients with severe dehydration after diarrhoea...
Bicarb? 
Blood acidosis or alkalosis? 
Hyper or hypokalaemia? 
Hyper or hypochloremia? 
Loss or normal Na+ 
High or low creatinine?
A

Bicarb depletion

Blood acidosis (due to loss of bicarb)

Hypokalaemia (due to loss of K+ in diarrhoea)

Hyperchloraemia (due to increased exchange with bicarb)

Loss of Na

High creatinine (due to low ECF vol so low renal blood flow so low GFR)

31
Q

Blood analysis in someone who has had excessive vomiting…

Acidosis or alkalosis?

Hyper or hypochloraemia?

Hyper or hypokalaemia?

High or low creatinine?

A

Metabolic alkalosis (due to increased plasma bicarb relative to the H+ loss)

Hypochloraemia (due to loss of Cl- in vomit)

Hypokalaemia

High creatinine (due to low GFR)

32
Q

What are the 2 immune cells/tissues along the GIT?

A

GALT- Gut associated lymphoid tissue

Peyer’s patches

33
Q

Peyer’s patches are nodules of what in the wall of the small intestine?

They house _____ immune cells and facilitate immune responses against gut pathogens

They contain __ cells which lack microvilli and allow exposure to gut pathogens

A

Lymphoid tissue

Adaptive

M

34
Q

M cells are the site of __ cell priming by ____ _____ ______ cells

M cells stimulate the development of ____-_____ __ cells

A

T cell priming by antigen presenting dendritic cells

Antibody-producing B cells

35
Q

___ CD4 T helper cells are all throughout the ____ ____ of the SI and LI

They protect against what?

A

TH1
Lamina Propria
Protect against viruses

36
Q

____ CD4 T helper cells are elevated in the _____ and the _____ and they protect against what?

A

TH17

Duodenum and jejunum

Protect against bacteria and fungus

37
Q

FOXP3 T-reg cells are all throughout the SI and colon and they do what?

A

They dampen the immune response to limit damage

38
Q

CD8 cytotoxic intraepithelial lymphocytes (IELs) are highest where in the GIT?

They sit within the ______ _____ and respond rapitly to antigen stimulation

What is the benefit of them?

A

Proximal SI

Mucosal epithelium

They are less reactive than CD8 T cells so there is less uncontrolled inflammation and also they are good at killing viral infected cells

BUT

They can induce barrier breach during inflammation which is bad

39
Q

Where are IgA producing plasma cells in the GIT and what do they do?

A

They are present throughout the SI and elevated in the colon

They produce IgA which is secreted into the mucus of the lumen

The IgA binds to target microbes within the gut lumen for immune recognition

40
Q

What cells samle food and microbial antigens?

What do they activate if there is no threat?

What do they activate if they sense a threat?

A

Dendritic cells

T-reg cells to dampen immune response

Antigen specific T-helper cells such as TH1 and TH17

41
Q

Rotavirus….

Infects epithelial cells of the GIT which are lost into the lumen, this causes what?

What is essential to counteract dehydration?

A

Causes a reduced absorptive ability of the immature cells to absorb sugar, salts and water so you get diarrhoea and dehydration

Fluid and salts

42
Q

What is the incubation period of Noravirus?

How many hours does it last?

Virus invades and destroys _____ and ____ villus epithelium and this leads to decreased absorption of what from the bowel lumen?

A

12-48 hours

12-60 hours (half a day to 2 and a half days)

middle and upper

Decreased absorption of Na and water

43
Q

Clostridium botulinium…

Where are toxins produced?

Toxins are absorbed in the blood and block neurotransmission of _______ _____

What are the symptoms? 3

A

Food or in the gut

Peripheral nerves

Paralysis, muscle weakness and resp arrest

44
Q

What is the bacteria that gives people food poisoning if they eat undercooked pork?

What is the food poisoning that occurs when rice cools to room temp and is reheated?

A

Clostridium perfringens

Clostridium cereus

45
Q

Which bacteria can be spread by flies?

What are the symptoms?

A

Shigella

39 fever and crampy abdo pain first, then diarrhoea and dysentery

46
Q

What is the treatment for Helminths (Parasitic worms)?

A

Albendazole

47
Q

Autonomic NS control of GIT motility and secretions…

Parasymp stimulation releases ___ onto __ receptors in the GIT –> increases ____ plexus activity –> increases GIT motility and secretions

Too much GIT mobility= ____

A

Ach onto M3 receptors

Increases enteric plexus

Too much= diarrhoea

48
Q

GIT motility and secretions cont…

Sympathetic stimulation releases ___ or ___ onto __, __, or __ ______ receptors in the GIT which inhibits _____ plexus activity= ___________

Too little GIT motility=

A

NA or Adrenalin onto a1, a2 or B2 adrenergic receptors

inhibits enteric plexus= relaxation of smooth muscle and decreases GIT motility

Constipation

49
Q

3 approaches for severe acute diarrhoea?

A

1- anti-infective agents (antibiotics)

2- fluid and electrolyte replacement

3- use of spasmolytic (reduces smooth muscle spasm) or other antidiarrhoeal agents (opiods)

50
Q

Enteric neurons express high levels of opiod receptors (some are also on secretory cells of GIT)…

What does stimulation of u-opioid receptors do?

What does stimulation of delta opioid receptors do?

A 
u= decrease GIT motility 
delta= decrease secretions
51
Q

What is the main opiod receptor agonist that we give for anti-diarrhoea?

It stimulates ____ receptor –> inhibits ___ release –> ___ longitudinal and circular smooth muscle of GIT –> _____ GIT motility

(May also do what?)

A

Loperamide (Imodium)

u-opioid receptor

inhibits Ach release

Relaxes muscle

Decreases motility

May also reduce GIT secretions

52
Q

What type of diarrhoea are bile acid sequestrants used for?

What is the one we use called?

How does it work?

A

Chronic diarrhoea

Cholestyramine

Binds to bile salts

53
Q

Where is the CTZ?

A

In the area postrema, which is on the floor of the 4th ventricle and outside the BBB

54
Q

What is the receptor for…

Serotonin?

Dopamine?

Acetylcholine?

Cannabinoids?

Substance P?

A

Serotonin= 5HT receptor

Dopamine= Dopamine D2 receptor

Ach= Muscarinic M1 receptor

Histamine= Histamine H1 receptor

Cannabinoids= CB1 receptor

Substance P= neurokinin NK1 receptor

55
Q

Ondansetron is a ______ ___ receptor antagonist

Serotonin is released by _______ cells in the SI in response to chemo

‘____s’ inhibit 5HT receptors on ____ afferents in periphery and prevent the signal to CNS

Inhibit 5HT receptors in CTZ and Solitary Tract Nucleus centrally which prevents activation of _____ centre

A

serotonin 5HT

Enterochromaffin cells

‘Setrons’ vagal

emetic

56
Q

Metaclopramide and domperidone are _______ receptor antagonists

Inhibit ______ __ _____ in CTZ and STN

How do they stimulate GIT motility?

Where else do they have (weak) antagonist action?

A

Dopamine

Dopamine D2 receptors

Stimulate GIT motility because blocking Dopamine receptors causes the stimulation of Ach on M3 receptors on GIT smooth muscle

Weak antagonist action at 5HT receptors

57
Q

What is the main Neurokinin NK1 (substance P) receptor antagonist?

How does it work?

What is it used for?

A

Aprepitant

Block the effects of sustance P in the CTZ and STN (Solitary tract nucleus)

Chemo induced sickness and post-op sickness

58
Q

What are the 2 main histamine H1 receptor antagonists?

Most effective for what?

Blocks effects of ____ in _____ afferents and ____ __ receptors in ___

A

Promethazine and cyclizine

Mositon sickness and vestibular disturbances

Histamine
Vestibular
Histamine H1 receptors
STN (Solitary tract nucleus)

59
Q

What is the most common Muscarinic M receptor antagonist?

Most effective for what?

Block the effects of ___ in _____ afferents

A

Hyoscine hydrobromide (Kwels)

Motion sickness and vestibular disturbances

Ach in vestibular afferents

Semester 2 (1st year) (13 decks)

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