alimentary control

Question 1

what are the nerve divisions involved in alimentary control?

Answer 1

somatic (voluntary)
- sensory
- motor
autonomic (involuntary)
- sympathetic
- parasympathetic

Question 2

what are the hormones in the GIT?

Answer 2

• cholecystokinin (CCK)
• gastrin
• gastric inhibitory peptide (GIP)
• secretin

Question 3

where is CCK secreted from and what is its function?

Answer 3

the duodenum endocrine cells
- functions to help digest fats and proteins

Question 4

where is gastrin secreted from and what is its function?

Answer 4

G cells in the stomach
- functions to stimulate HCL by parietal cells

Question 5

what is the function of GIP?

Answer 5

increases insulin secretion

Question 6

what is the function of secretin?

Answer 6

increase HC03 (bicarbonate) from the pancreas

Question 7

where are hormones most active?

Answer 7

at the level of the stomach

Question 8

what is secretory control done by?

Answer 8

entirely neural via some cranial nerves

Question 9

what are the cranial nerves involved with chemical taste and smell secretion control?

Answer 9

taste- 7 and 9
smell- 1

Question 10

what cranial nerve is involved with mechanical chewing secretion control?

Answer 10

loading periodontal ligaments CN 5

Question 11

what are the stimuli involved with salivatory secretion?

Answer 11

• vision
• olfactory (smell)
• mechanical (chewing)
• chemical (taste)

Question 12

what muscles are involved in chewing?

Answer 12

jaw, facial and tongue muscles

Question 13

which cranial nerves are involved in chewing?

Answer 13

5, 7, 12

Question 14

what muscles are involved in swallowing?

Answer 14

jaw, tongue and pharyngeal muscles

Question 15

what cranial nerves are involved with swallowing?

Answer 15

5, 9, 10 and 12

Question 16

what muscles are involved in the oesophagus?

Answer 16

mix of skeletal and smooth muscle

Question 17

what cranial nerve is involved with the oesophagus?

Answer 17

10- vagus

Question 18

what are the functions of the stomach?

Answer 18

• secretion (gastric juice)
• motility (filling, relaxation, mixing, peristalsis, emptying)

Question 19

what are the stimuli of gastric activity?

Answer 19

cephalic phase
- mechanical chewing (muscles of mastication)
- chemical (taste, smell)
- psychic (visual, emotional)
gastric phase- stimulates secretion
- mechanical (distension)
- chemical (food in stomach)
intestinal phase
- mechanical (distension)
- chemical (acid, protein in duodenum)

Question 20

what is distension?

Answer 20

knowing you’re full

Question 21

what are the controls of gastric activity?

Answer 21

cephalic phase
- nerves (long reflex)
gastric phase
- nerves (long & short reflexes)
- hormones (gastrin)
intestinal phase
- nerves (long & short reflexes)
- hormones (GIP and secretin)
- tends to slow gastric emptying

Question 22

short vs long nerve reflexes

Answer 22

long- to brain
short- locally at that site

Question 23

what are the functions of the small intestine?

Answer 23

• absorption
• secretions (intestinal juice)
• motility (mixing, villus movements, segmentation contractions, peristalsis)

Question 24

what are the controls of the small intestine?

Answer 24

mainly by local nerves/short reflexes in response to intra-luminal stimuli

Question 25

describe the role of bicarbonate in pancreatic juice

Answer 25

Intestinal phase
- secretin (released from the duodenum in response to acid to neutralise, stimulates secretion of bicarbonate rich pancreatic juice)
- CCK and VIP- weaker stimulation of bicarbonate

Question 26

what is CCK?

Answer 26

Cholecystokinin (bile sac mover) and mainly works by promoting the digestion of fat and protein. It also is an appetite suppressant.- stimulates secretion of bicarbonate, enzyme rich pancreatic juice

Question 27

what is VIP?

Answer 27

Vasoactive intestinal polypeptide – many functions and production sites but for the gut it breaks down glycogen and relaxes the smooth muscle of the gall bladder and the stomach.

Question 28

where is gastrin released from?

Answer 28

g cells in the stomach, duodenum and pancreas

Question 29

what is the function of gastrin?

Answer 29

increases the secretion of HCl by the parietal cells in the stomach

Question 30

what is GIP?

Answer 30

Gastric Inhibitory Peptide (Polypeptide) – weak inhibition of stomach acid secretion, but actually stimulates insulin secretion, stops death of pancreatic beta cells (insulin producing cells), stimulates glucagon and also accumulation of fat.

Question 31

what are patients with their gallbladder removed advised?

Answer 31

to reduce their fat intake

Question 32

secretion of bile CCK

Answer 32

• Stimulates contraction of gall bladder (gall bladder needed to store bile)
• relaxation of the sphincter of oddi

Question 33

what are the functions of the large intestine and rectum?

Answer 33

• secretions (mucus to protect, water and electrolytes)
• motility (mixing, mass movements- peristalsis and defaecation)

Question 34

describe neural control in the large intestine

Answer 34

• mixing and segmentation is controlled by local reflexes
• long reflexes are triggered by food entering the stomach- increases motility in the intestine
• gastro-ileal reflex- gastric activity increases motility in the ileum
• gastro-colic reflex- gastric activity increases motility on the colon

Question 34

describe neural control in the large bowel

Answer 34

• mixing and segmentation is controlled by local reflexes
• long reflexes are triggered by food entering the stomach- increases motility in the intestine
• gastro-ileal reflex- gastric activity increases motility in the ileum
• gastro-colic reflex- gastric activity increases motility on the colon

Question 35

describe control in the large intestine and rectum

Answer 35

• mainly nueral
• ANS, Vagus, pelvic nerves

Question 36

describe control in the rectum

Answer 36

• ANS control of internal and sphincter
• voluntary control of external sphincter
• somatic nerves

Question 37

what are the two main anal sphincters?

Answer 37

internal and external

Question 38

what is the internal anal sphincter controlled by

Answer 38

parasympathetic fibres which relax involuntarily

Question 39

what type of muscle is the external anal sphincter?

Answer 39

skeletal muscle

Question 40

what controls the external anal sphincter?

Answer 40

somatic nerves from the inferior anal branch of the pudendal nerve- allows conscious control of defecation

Question 41

what are the reflexes which take place is defecation is appropriate?

Answer 41

Relaxation of the external sphincter
Contraction of abdominal wall muscles
Relaxation of pelvic wall muscles
Peristaltic waves then facilitate the movement of faeces through the anal canal.