Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

SGUL - Physiology 1 > Introduction to Function and Control of The Alimentary Tract > Flashcards

Introduction to Function and Control of The Alimentary Tract Flashcards

1
Q

What are the digestive functions of the stomach?

A
  • Accomodation and storage
  • Mechnical and enzymatic breakdown
  • Delivery of chyme to the duodenum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the role of the stomach during storage of digestive products.

A
  • Acts as a reservoir in which unmixed food is stored, during Stage 1 of digestion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

How does the fundus allow large volumes of food storage?

A
  • Relaxes
  • Vagal reflex inhibits smooth muscle tone.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the purpose of the antral region of the stomach?

A

Mechanical degradation of food before mixing it with gastric secretions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the role of the colon/rectum during storage of digestive products.

A

Storage of indigestive residues and faecal matter occur before excretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the storage of gastric secretions.

A

Stores 2-3 litres of gastric juice aiding in digestion and absorption of food.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Where are mucous gastric secretions released from and what are they needed for?

A
  • Secreted by goblet cells and mucous neck cells
  • Acts as a barrier that protects the stomach and colon and prevents trauma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the purpose of lipase gastric secretions?

A

Hydrolysis of triglycerides to fatty acids and glycerol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Where are pepsin gastric secretions released from and what are they needed for?

A
  • Secreted by peptic cells as pepsinogen
  • Aids protein digestion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where are HCl gastric secretions released from and what are they needed for?

A
  • Secreted by parietal cells
  • Important for defence of the gut
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Where are intrinsic factor gastric secretions released from and what are they needed for?

A
  • Secreted by parietal cells
  • Aids Vitamin B12 absorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the pancreatic secretions into the gut.

A
  • Secreted from cells in the mucosa
  • Chemical acts locally on adjacent cells via the interstitial fluid.
    e.g somatostatin, which inhibits gastric release in the stomach.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

List some exocrine secretions that aid in digestion that are released from the salivary glands.

A
  • Mucous
  • Lipase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

List some exocrine secretions that aid in digestion that are released from the gastric glands.

A
  • HCl
  • Pepsin
  • Mucous
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

List some exocrine secretions that aid in digestion that are released from the pancreas.

A
  • Bicarbonate ions
  • Enzymes (eg. amylase, lipase, carboxypeptidase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

List some exocrine secretions that aid in digestion that are released from the liver.

A
  • Bile salts
  • Bile acids
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are endocrine secretions?

A
  • Synthesised by ductless glands and enter the blood stream
  • Travel to target tissue(s) and bind to specific receptors to elicit their effects.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Give examples of endocrine secretions and where they are secreted from.

A
  • GASTRIN: G-cells in antrum of stomach
  • SECRETIN and PANCREOZYMIN-CHOLECYSTOKININ: duodenal mucosa
  • INSULIN: β-cells of pancreas
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What do endocrine, exocrine and paracrine secretions allow?

A
  • Active digestion
  • Control of digestion and gastric motility
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the point of absorption?

A
  • Nutrients from digestion must be transported across the intestinal epithelium into the blood (eg. glucose, amino acids, etc.) or lymph via lacteals (fats/lipids) so they can be used for physiological processes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where does most fluid absorption occur?

A

Small intestine and colon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What causes the pathogenesis of diarrhoea?

A

Disorders of fluid secretion and absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is motility?

A

Movements of the muscular wall (mostly smooth muscle except extreme ends of upper oesophagus/rectum)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is motility needed for?

A
  • movement from one region to another (law of gut); mass evacuation
  • mechanical degradation (eg. gastric antrum)
  • mixing lumen contents (eg. small intestines)
  • transport of nutrients, water and of urea and electrolytes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What are the different methods of excretion of drugs and other products of metabolism?

A
  • saliva
  • bile
  • faeces
  • vomit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

How are indigestible food residues excreted?

A

Faeces

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How is the gut vulnerable to pathogen exposure?

A
  • Interface with the ‘contaminated’ external environment
  • Intestine is the largest mucosal surface in the body and exposed to the heaviest burden of environmental antigens.
  • Breaches in the barrier cause toxins to enter the blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What different defence mechanisms does the gut have? PART 1

A
  • sight, smell and taste alerts to harmful food substances
  • vomit reflex
  • HCl kills most harmful bacteria
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What different defence mechanisms does the gut have? PART 2

A
  • mucous secretions
  • neutral bacterial flora prevents the colonisation of harmful bacteria
  • aggregation of lymphoid tissue (eg. Peyer’s patches) mount responses to food-borne antigens - analyse and response to pathogenic microbes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Where are Peyer’s patches located?

A
  • Lamina propria layer of the mucosa
  • Extend into submucosa of ileum.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe the metabolic function of the gut.

A
  • Liver involved in carbohydrate, nitrogen and lipoprotein metabolism
  • Liver involved in production of bile and excretion of bilirubin.
32
Q

What is the effect of parasympathetic innervation of the gut?

A

Stimulates salivation

33
Q

What is the effect of sympathetic innervation of the gut?

A
  • inhibits salivation
  • relaxes the bladder
  • contracts the rectum
34
Q

Describe the three types of reflexes involved in the relaxation of the fundus.

A
  • RECEPTIVE (mechanical stimulation of the pharynx - mechanoreceptors, sight)
  • ADAPTIVE (vagal innervation, {NO,VIP}, tension of the stomach)
  • FEEDBACK (nutrients, CCK)
35
Q

What are receptive, adaptive and feedback-relaxation of the stomach mediated by?

A
  • Mediated by NANC mechanisms (i.e. inhibition involving NO, VIP, etc.)
  • Reflex chains involving noradrenaline release
36
Q

What happens when the stomach is ready to receive food?

A
  • Noradrenaline is released from the sympathetic nerve fibres
  • Stomach relaxes
37
Q

What is PACAP and what has it been shown to do?

A
  • Pituitary adenylate cyclase (AC)-activating peptide
  • Isolated from the pituitary
  • Stimulates AC activity in the anterior pituitary.
38
Q

Where is PACAP found?

A
  • Brain
  • Gut (in the myenteric and submucosal ganglia).
39
Q

What does PACAP do?

A
  • Neuronal regulation of gastric acid secretion (contributing to intestine motility)
  • Relaxation of colonic smooth muscle
  • Stimulates pancreatic secretion (causing insulin and glucagon secretion)
40
Q

Describe the steps of food movement through the stomach. PART 1

A
  • Ripples of contraction move the food towards the antrum (thicker muscle layer).
  • Pyloric sphincter is often relaxed, but closes upon the arrival of the peristaltic wave.
  • Chyme repulsion causes the opening of the pyloric sphincter.
41
Q

Describe the steps of food movement through the stomach. PART 2

A
  • Small, partially digested material is squirted through the pyloric sphincter into the duodenum.
  • Repulsion of antral contents allow for mixing/grinding.
42
Q

What are the different types of control of the alimentary tract?

A
  • endocrine
  • paracrine
  • neural
  • metabolic
43
Q

Describe the endocrine control of the alimentary tract. PART 1

A
  • When the stomach is distended, neurons are stimulated, releasing GRP, which acts on G cells to release gastrin.
  • This travels through blood and affects enterochromaffin-like cells (EMF cells) and parietal cells.
44
Q

Describe the endocrine control of the alimentary tract. PART 2

A
  • ECL cells release histamine, which promotes acid secretion from parietal cells.
  • Acetylcholine also affects ECLs and parietal cells in a similar manner.
45
Q

What do the hormones produced by the gut have in common?

A

They are proteins

46
Q

Describe the paracrine control of the alimentary tract.

A
  • Paracrine agents go to target tissues via the interstitial fluids.
47
Q

What stimulates somatostatin release? What is its effect?

A
  • Increased H+ stimulates D cells, which release somatostatin.
  • Acts on G cells to inhibit the release of gastrin.
48
Q

Describe the neural control of the alimentary tract. PART 1 - THE VAGO-VAGAL REFLEX

A
  • Reflex in which both the afferent (‘sensory’) and efferent (‘motor’) axons are in the vagus nerve trunk.
  • Reflex circuit within the GIT.
49
Q

Describe the neural control of the alimentary tract. PART 2 - THE VAGO-VAGAL REFLEX

A
  • Pathway is via the brain stem (medulla).
  • Refers to reflex control of responses to gut stimuli via the NTS and DMVN.
50
Q

Describe the neural control of the alimentary tract. PART 1 - ENS/LOCAL REFLEX

A

Two nerve fibres are intrinsic to the gut:
1. Myenteric Plexus (Auerbach’s plexus): motor function (P + S)
2. Submucosal Plexus (Meissner’s plexus): intestinal secretions (only P)

*P = Parasympathetic/ S = Sympathetic

51
Q

Describe the neural control of the alimentary tract. PART 2 - ENS/LOCAL REFLEX

A
  • Regulate GI functions entirely within the wall of the gut.
  • Connected to the CNS via the parasympathetic and the sympathetic fibres
  • Effects mediated by enteric nervous system
52
Q

What is the difference between the Auerbach’s plexus and Meissner’s plexus?

A
  • Auerbach’s plexus has both parasympathetic and sympathetic input
  • Meissner’s plexus has only parasympathetic fibres and provides secretomotor innervation to the mucosa nearest the lumen of the gut.
53
Q

Give an example of how the innervation of the gut recognises food in the system.

A
  • When there is food in the oesophagus, it will stimulate mechanoreceptors.
  • Will send impulses to the brain and back via the vagal afferent (and efferent) fibres.
54
Q

What is the colo-colonic reflex?

A
  • Presence of food or food products/distension of the stomach increases colon motility
  • Due to the stretch in the stomach and by-products of digestion in the small intestine.
55
Q

How does stimulation of the sympathetic nervous system influence colon motility?

A

Decrease colon movement.

56
Q

How does stimulation of the parasympathetic nervous system influence colon motility?

A

Increase contraction in the proximal colon so greater motility

57
Q

How does stimulation of the sympathetic nervous system affect Auerbach’s plexus?

A

Decreased gastric motility and secretion.

58
Q

How does stimulation of the parasympathetic nervous system affect Auerbach’s plexus?

A

Increased gastric motility and secretion

59
Q

Describe the metabolic control of the alimentary tract.

A
  • Rate of emptying is dependent upon the material’s ability to be absorbed.

THIS IS WHY:
Carbohydrates are emptied quickly into the duodenum.
Proteins are slow-emptying, while fats are even slower.

60
Q

How do fatty acids lead to decrease in gastric emptying?

A

Increasing the contractility of the pyloric sphincter.

61
Q

Describe the peristalsis of the alimentary tract.

A
  • Wave of propulsive contractions that moves contents of the gut towards the anus.
  • Slower in the large intestine when compared to the small intestine.
62
Q

Describe the regulation of movement in the alimentary tract.

A
  • Distention initiates the contraction
  • Vagal inhibitory and excitatory fibres control movement.
63
Q

What happens when peristaltic waves pass over the stomach?

A

Luminal material is forced into the duodenum

64
Q

What does the vagal reflex inhibit?

A

→ Smooth muscle tone
→ Mechanoreceptors
→ Fundic relaxation

65
Q

Where is the antral region?

A

→ Lower region of the stomach

66
Q

How can the gut initiate its own responses?

A

→ It has an enteric nervous system which can initiate its own responses to gut stimuli without higher functions of the brain

67
Q

What are the contractions initiated by?

A

→ Excitatory reflexes and mediated by ACh or substance P

68
Q

What are relaxation effects mediated by?

A

NO/VIP

69
Q

What are splanchnic nerves?

A

Sympathetic fibres

70
Q

When does receptive relaxation occur?

A

→ Which happens by mechanical stimuli
→ Food is expected in the stomach
→ Sphincter relax to allow food to enter

71
Q

Why is CCK being released?

A

→ Due to lipids being in the food

72
Q

What does CCK do?

A

→ Decreases feeding because relaxation is occurring

73
Q

What does CCK promote?

A

→ Bile secretion
→ Gall bladder contracting

74
Q

What is the sieving effect?

A

→ Viscous and solid matter are retained in the stomach
→pylorus can detect the size of food particles, 1-2mm are passed through
→anything larger goes back to the antrum for grinding.

75
Q

When is the vago-vagal reflex active?

A

→ during the receptive relaxation of the stomach in response to swallowing

76
Q

What are the neurotransmitters used in the plexuses?

A

→ ACh, NO, NA, 5-HT, GABA and ATP

77
Q

How does the bolus get moved along?

A

→ Contractions are initiated by excitatory activity mediated by substance P and AcH
→ The circular muscles have to relax in front and contract behind
→Longitudinal muscles are contracted

SGUL - Physiology 1 (68 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions