Lecture 7

Question 1

Satiety?

Answer 1

Feeling of fullness

Question 2

What is control of food intake regulated by?

Answer 2

Glucose levels
Hormones: leptin (produced in adipose tissue), ghrelin (stomach), insulin (pancreas), glucagon (pancreas)
Stretch receptor in GI tract
Stress, body temp, look of food

Question 3

Well fed/absorptive state?

Answer 3

Increased glucose -> glycogen synthesis -> insulin secretion (enhances glucose uptake, reduces blood glucose)

Question 4

Post-absorptive state?

Answer 4

Decreased glucose -> hormone glucagon causes breakdown of glycogen, creation of new glucose (gluconeogenesis), ketones produced as source of energy

Question 5

What hormone released when hungry (decreased glucose/fat/protein)?

Answer 5

Ghrelin - sends signal to lateral hypothalamus (appetite centre) in brain: need to eat

Question 6

What hormone released after meal (increased glucose/protein/fat)?

Answer 6

Leptin - sends signal to medial hypothalamus (satiety centre), also signals from GI tract (mechanical input)

Question 7

How does meal size influence gastric emptying?

Answer 7

More food = longer digestive phase (slow to begin then faster): don’t want dumping effect into small intestine

Question 8

How do calories influence gastric emptying?

Answer 8

High calories = delay gastric emptying

Question 9

How does fat content influence gastric emptying?

Answer 9

Fat in duodenum (first part of small intestine) -> fundus relaxes -> reduces intragastric pressure, high fat meal = feel full for longer, prolongs elevation of pH in stomach

Question 10

Central nervous system?

Answer 10

Brain and spinal cord

Question 11

Peripheral NS?

Answer 11

Connects CNS to limbs/organ

Question 12

Autonomic NS?

Answer 12

Division of PNS influencing function of organs

Question 13

Enteric NS?

Answer 13

Intrinsic NS of GI tract (myenteric plexus + submucosal plexus)

Question 14

What are CNS and ENS connected by?

Answer 14

Vagus nerve (runs from brain stem to abdomen, primary route for gut bacteria transmitting info to brain)

Question 15

Role of afferent (sensory receptor) neurons?

Answer 15

Carry nerve impulses from receptors/sense organs to CNS

Question 16

Role of efferent (motor/effector) neurons?

Answer 16

Carry nerve impulses from CNS to effectors (muscles/glands)

Question 17

Role of myenteric plexus?

Answer 17

Motor - influences muscle activity

Question 18

Role of submucosal plexus?

Answer 18

Sensory - influences secretory activity, receives signals from epithelium/stretch receptors

Question 19

Segmentation?

Answer 19

Facilitates food mixing (circular muscles)

Question 20

Peristalsis?

Answer 20

Muscle contraction move food along tract (longitudinal muscles)

Question 21

Gut transit time?

Answer 21

12-48 hours (too fast - less absorption of nutrients, too slow - poor gut health)

Question 22

Drugs that affect drug transit time?

Answer 22

Antacids, anticholinergics, antihypertensives: can cause constipation
Loperamide: decrease peristalsis, target = opioid receptors
Tegaserod: stimulates motility through activation of receptors in ENS
Antibiotics: can result in antibiotic-resistant organisms -> diarrhoea