Applied Physiology

Question 1

How do laxatives work?

Answer 1

e. g. Epsom salts

- Poorly absorbed so add osmotic pressure in lumen so drag water out to help liquify stool

Question 2

What do bacterial agents target to cause diarrhoea?

Answer 2

Loosen tight junctions in intestinal epithelial

Question 3

Where is Na absorbed and how?

Answer 3

• Jejunum
• Co-transport with glucose via SLGT-1
• Exchange with H+

Question 4

Where is K absorbed and how?

Answer 4

• Paracellular absorption throughout small intestine - via solvent drag as Na pulled in…
• Secreted in colon - aldosterone

Question 5

How is Ca absorbed and how?

Answer 5

• Passive (paracellular) in jejunum + ileum
• Active transport (transcellular) in duodenum via TRPV channels
  = regulated by calcitriol + requires intracellular buffer calbindin

Question 6

How is Fe absorbed?

Answer 6

• Ferric (Fe3+) = dietary form reduced to ferrous (Fe2+)
• Fe2+ either
  1. Sequestered as ferritin
  2. Transported out + complexed as transferrin

Question 7

Which is absorbed and secreted between Cl- and HCO3-?

Answer 7

Cl- absorbed

HCO3- secreted

Question 8

What stimulates enteric (NANC) neurons and EC cells?

Answer 8

Cl- secretion

Question 9

What sitmulates D cells and enteric neurons?

Answer 9

Na+ and Cl- absorption

Question 10

What influences motility in the small and large intestine?

Answer 10

1. Enteric NS
   - Myenteric plexus - motor
   - Submucosal plexus - sensory, affects secretary activity
2. Autonomic NS
   - PSNS increases motility
   - SNS decreases motility

Question 11

Which are the excitatory NT’s in gut motility?

Answer 11

ACh

Sub P

Question 12

Which are the inhibitory NT’s in gut motility?

Answer 12

VIP

NO

Question 13

What are the basic types of postprandial movement in the SI?

Answer 13

• Individual villi
• Pendular
• Segmentation
• Peristaltic
• Migrating motility complex during fasting

Question 14

What is motility in intestines enhanced and inhibited by?

Answer 14

• Enhances by gastrin

- Inhibited by secretin

Question 15

What is the role of interstitial cells of cajal (ICC)?

Answer 15

• Form part of SIP syncytium = Smooth muscle cells
  Interstitial cells of Cajal
  Platelet-derived growth factor receptor alpha-positive cells
• ICC’s display pacemaker activity due to IC release of Ca
• Depolarisations transmitted to smooth muscle cells via gap junctions = slow waves = propagate in antral direction

Question 16

Which motility influencing mediators are released from cells in gut wall?

Answer 16

• NANC: VIP` relaxes smooth muscle
• Enteric neurons: enkephalins regulate peristaltic reflex
• EC cells: serotonin activates local motor reflex
• N cells in ileum: release neurotensin in response to fat = decreases motility
• L cells in distal ileum: release GLP-1 in response to glucose + fat
• M cells in duodenum: release motilin in response to fat + acid = increases sensitivity of SM to intrinsic nervous activity, stimulates gastric emptying + migrating motility complex

Question 17

What is entry at ileocecal junction regulated by?

Answer 17

• Relaxes by ileal distension

- Increases in tone by colon distension

Question 18

What electrolyte and water absorption is their in the colon?

Answer 18

Na actively transported
(aldosterone)
Cl- exchanged with HCO3-

Question 19

Summarise the movements in the colon

Answer 19

• Segmental mixing - circular SM, haustrations
• Propulsive - initiated by intrinsic reflex pathways, enhances by vagal neurons, gastrin + CCK increase colon excitability

Question 20

What muscles make up the anal canal?

Answer 20

• Internal sphincter - smooth muscle

- External sphincter - skeletal muscle

Question 21

What control causes walls of sigmoid colon and rectum to contract?

Answer 21

PS

Question 22

What allow rectum to straighten?

Answer 22

Pelvic floor muscles