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physiology > GI > Flashcards

GI Flashcards

1
Q

why do we need the GI tract?

A

To make ATP
To make new cell parts (building blocks)
To maintain cellular function – cell division and growth and repair.

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2
Q

what are the two types of digestion.

A

chemical and mechanical.

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3
Q

retropulsion

A

stomach - the backward movement of bolus to make the pieces smaller to then fit through the pylorus to the duodenum.

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4
Q

propulsion

A

stomach - the movement of food forward.

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5
Q

the digestion of carbs

A

physical digestion – polysaccharides (starch) many.
Chemical digestion – monosaccharides.

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6
Q

the digestion of lipids.

A

Physical digestion – triglycerides
Chemical digestion – 2x fatty acids and monoglycerides.

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7
Q

the digestion of protein.

A

Physical digestion – protein (many)
Chemical digestion -amino acids short peptides.

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8
Q

accessory organs in digestion.

A

Salivary gland – helping food go down
Liver – production of bile salts,
Gall bladder – storing bile
Pancreas – pancreatic juices enzymes.

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9
Q

how does the CNS regulate the GI tract?

A

parasympathetic - increased digestion, stimulates motility and secretion.
sympathetic - inhibits motility and secretion.

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10
Q

how does the enteric nervous system regulate the GI tract?

A

self-contained system.
able to function independently of the CNS. web of neurons that stimulate motility, secretion and absorption.

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11
Q

how do hormones regulate the GI tract.

A

GI tract is the largest endocrine organ in the body.
hormones secreted by endocrine cells throughout the intestinal tract. e.g gastrin - stimulates acid production in stomach. stimulates gastric motility.

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12
Q

mouth

A

Chewing – physical breakdown of food.
Saliva – lubrication – for swallowing and easy passage of food.
Salivary amylase enzyme – initial chemical breakdown of carbohydrate.
Dissolves food – allpws tasting.

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13
Q

Esophagus

A

Transport of materials to the stomach. Food is moved via peristalsis. Sphincter between esophagus and stomach (lower esophageal sphincter) prevent acid reflux.

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14
Q

Stomach

A

Storage – relaxation of smooth muscles allows volume to increase without change in pressure. Must be able to store a meal or two to allow time for the food to be physically and chemically digested.

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15
Q

chemical digestion.

A

Only protein in stomach. Stomach secrete acid and pepsin.
Acid unfolds the protein structure. Pepsin will then chop up the unfolded protein inot polypeptides.

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16
Q

anticipation - cephalic phase.

A

Function: Prepare the stomach for the arrival of food.
Responds to: Seeing, smelling, tasting or thinking about food
Triggers: Activation of the Central nervous system (brain) ↑Parasympathetic Nervous System Activity
- Release of the hormone (gastrin) from cells in the stomach Outcome: ↑ Secretion of mucus, acid and pepsin from cells in.

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17
Q

Race - Gastric (stomach) phase: food arrives in stomach

A

Function: Maximise physical digestion and begin protein chemical digestion
Responds to: Stretch, ↑pH, undigested food (esp protein)
Triggers: Activation of the Enteric nervous system ↑ Release of gastrin
Outcome: ↑ Secretion of mucus, acid and pepsin ↑ Mixing waves

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18
Q

Handover – Intestinal phase: stomach → intestine

A

Function: Slow controlled release of food to small intestine.
Responds to: Stretch of the SI wall, ↓pH (acid), lipids (fat) and carbohydrates in the intestine
Triggers: Release of SI hormones.
Outcome: Inhibition of the enteric nervous system innervating stomach ↓ Secretion of acid and pepsin ↓ Mixing waves.

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19
Q

How does exercise impact Gastric Emptying?

A

High Intensity Exercise
|
↑↑Sympathetic NS Activity & ↓Parasympathetic NS Activity
|
Reduction in neural and hormonal control
|
Delayed gastric emptying.

20
Q

Small intestine

A

completion of chemical digestion, absorption of 90% of nutrients
First part is the – duodenum = ‘doorman’ works with accessory organs for digestion and absorption of nutrients.

21
Q

Duodenum

A

HCO3 (bicarbonate) and mucus secretion.
- Protects the SI from stomach acid.

22
Q

Pancreas digestive enzyme

A
  • Chemical digestion of protein, fat and carbohydrate.
23
Q

Small Intestine – Chemical digestion

A

Chemical digestion of – Carbohydrates, protein and fat
Pancreas secretes (releases) enzymes into the duodenum:
Amylase - carbohydrate digesting enzyme
Proteases - protein digesting enzyme
Lipase - fat digesting enzyme.

24
Q

amylase.

A

carbohydrate digesting enzyme.
starch - disaccharide (2).

25
Q

Proteases

A

protein digesting enzyme. polypeptides (20) to small polypeptides (10). breaks up the long chains of protein.

26
Q

lipase

A

fat digesting enzyme.
triglycerides (3) - 2x fatty acid and monoglyceride.

27
Q

Small Intestine – Brush Border Enzymes

A

The rest of the small intestine.
Chemical digestion of carbohydrates and proteins is finished by brush border enzymes.
Carbohydrates: Disaccharides monosaccharides.
Protein: Small Polypeptides Amino acids + short peptides (2-3).

28
Q

Segmentation

A

Rhythmic contraction and relaxation * but no set pattern.
Important for chemical digestion * mixes the digested food with pancreatic enzymes * increases contact with intestinal wall/brush border.
But: * does not move chyme through intestine * not physical digestion (because this has already been finished by the stomach).

29
Q

The GI Tract – Large Intestine (Colon)

A

Absorption of vitamins, electrolytes and water * Microbial fermentation (flatus) * Forms and stores faeces, comprising of: * bacteria * old epithelial cells * undigested food matter * fibre * a little bit of water

30
Q

carbs break down.

A

Polysaccharides (most)
*Glycogen (liver) and starch (plants)

Disaccharides (some)
* Sucrose

Monosaccharides (a little)
*Glucose

the small intestine will only ababsorbsorp monosaccharides.

31
Q

the small intestine cell structure.

A

Lumen= inside tube of small
intestine (with digested food)
Apical Membrane = cell side
exposed to digested material
(lumen side)
Basolateral membrane = cell
side exposed to interstitial fluid
(blood side).

32
Q

sodium concentration gradient in carbs absorption.

A

Sodium concentration gradient
High = outside cells
Low = inside cells
Sodium electrical gradient
* Positive = outside cells
* Negative = inside cells
= Sodium electrochemical
gradient

33
Q

how is glucose absrobed.

A

apical membrane - Sodium-coupled secondary active
transport
* Movement of Na+ down its
concentration gradient to
drives glucose transport
against its concentration
gradient.

Basolateral membrane
* Facilitated diffusion
* Glucose transporter drives
glucose transport down its
gradient

both driven by the sodium electrochemical gradient.

34
Q

how does water follow carb absorption?

A

By osmosis
* Movement of water from an
area of lower solute
concentration to higher
solute concentration.

35
Q

rehydration fluids - maximise isosmotic fluid uptake.

A

Na+ & glucose in drinks/rehydration fluids
–Oral rehydration salts
*25 g sugar + 3 g salt per litre of water
–6 level tsp sugar, ~0.5 tsp salt

36
Q

Rehydration Fluids – Sports Drinks

A

Maximise isosmotic fluid uptake:
* Na+ & glucose in drinks/rehydration fluids.
Gatorade 60 g sugar + 4.9 g salt /litre
◼12 tsp sugar, 1 tsp salt

37
Q

digestion journey of protein.

A

acid + pepsin in the stomach - polypeptides - proteases - small polypeptides - brush boarder enzymes - amino acids (1) and short peptides (2-3).

38
Q

Protein absorption.

A

uses sodium electrochemical gradient.

Apical Membrane
* Sodium-coupled secondary
active transport

Basolateral Membrane
* Facilitated diffusion
* Amino acid transporter

39
Q

fat digestion journey.

A

triglycerides - lipase, bile slats - free fatty acids (2) and monoglyceride (1). to absorb fats must be broken into small droplets and emulsified.

40
Q

how can fat be absorbed as a lipid.

A

is a lipid so water insoluble. bile salts go both ways Water loving head (hydrophilic)
and Lipid loving tale (hydrophobic). breakdown into smaller ‘droplets’ via segmentation = Emulsification. Bile surrounds droplets and form micelles.

41
Q

fat absorption into the blood.

A

micelle - simple diffusion into the small intestine cells. the bile slats are released (reasbosrped and recycled). monoglycerides and fatty acids reassembled into triglycersides and other lipids. repackaged into chylomicrons (special form of fat).

42
Q

how does blood flow effect absorption?

A

decreases absorption

43
Q

why do we get stitch?

A

If you have food in your stomach → ↑blood flow to digestive tract and ↓blood flow to diaphragm → diaphragm cramping and causing a side stitch in the area.

  • Ligaments that connect your diaphragm to internal organs are overstretched → causes spasms.
  • Friction between the membranes that line your abdominal wall and the membrane that line your abdominal organs.
44
Q

The Gut Microbiome – The Effect of Diet

A
  • Diet plays a large role in
    determining what kinds of
    microbiota live in the colon.
  • The type and amount of
    protein, fat and
    carbohydrates present in the
    diet have been widely found
    to influence the composition
    of the gut microbiota in the
    body.
45
Q

The Gut Microbiome – The Effect of Exercise

A

More exercise.
More bacterial diversity.
Better health.

physiology (11 decks)

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