Control of food intake

Question 1

Describe the volume of the stomach when we have not eaten (fasting)

Answer 1

In an empty stomach, the volume is small.

50ml

Question 2

What happens to the stomach when we begin to eat food?

Answer 2

The fundic area of the stomach enlarges to accommodate food. NO and Vasoactive intestinal polypeptide allow this to happen.

1.5L

Question 3

What motion allows the stomach to empty?

Answer 3

We get contraction of the antrum area of the stomach

Question 4

What hormone stimulates appetite?

Answer 4

Ghrelin

Question 5

What causes the stomach to relax when we swallow food?

Answer 5

Co-ordinated by:

1. Receptive
2. Adaptive
3. Feedback relaxation

Inhibitory vagal fibres release acetycholine that activate the enteric pathways that release NO, PACAP, VIP and ATP to relax the muscle

Question 6

In order to relax what do fats and lipids release in order for the stomach to relax to it can receive food?

Answer 6

CCK

Question 7

What is vagotomy and what does it cause?

Answer 7

A surgical operation in which one or more branches of the vagus nerve are cut, typically to reduce the rate of gastric secretion (e.g. in treating peptic ulcers).

Reduces accommodation and gastric compliance

Question 8

Define Hunger

Answer 8

Discomfort caused by lack of food and the desire to eat – a strong physiological craving/drive for food/sensation of emptiness in the stomach

Question 9

Define appetite

Answer 9

Psychological desire/drive to satisfy the body’s needs of food; a hunger-stimulated response

Question 10

Define satiety

Answer 10

State of being full after eating food (joyous moments – no longer need to continue eating)

Question 11

Define aphagia

Answer 11

The inability or refusal to swallow

Question 12

Define Hyperphagia/polyphagia

Answer 12

An abnormal desire for food (extreme unsatisfied drive to eat)

Question 13

What is food intake controlled by?

Answer 13

It is controlled by the Hypothalamic control

Question 14

Give 2 reasons for differences in BMI?

Answer 14

Genes (70%)

How much we eat and its composition

Question 15

Foods are metabolised at different times in the day:

Carbs

Fats

When are they metabolised?

Answer 15

• Carbohydrates metabolised during the day
• Fats metabolised at night
• Hypothalamus responds to the switch between carbohydrate and fat metabolism

Question 16

What else can appetite be influenced by?

Answer 16

Family gatherings, food palatability, emotional, habitual, and circadian factors

Question 17

How does the hypothalamus control food intake?

Answer 17

• The base of the hypothalamus has several nuclei that regulate energy homeostasis
→ Control the appetite; size of helping, and our ingestive behaviour

Question 18

What is the satiety centre in the body?

Answer 18

Hypothalamus (ventromedial nuclei - wall of paraventricular)

Question 19

What happens when we get stimulation of ventromedial nuclei?

Answer 19

Aphagia

Question 20

What happens when we get lesions of ventromedial nuclei?

Answer 20

Hyperphagia (an increased appetite or excessive hunger)

Question 21

Where is the thirst centre located?

Answer 21

Lateral hypothalamus

Question 22

Do opioids increase appetite

Answer 22

Yes

Question 23

What does the dorsomedial nucleus control (DMN)?

Answer 23

Modulates energy intake (hunger centre)

Question 24

What does the release of NPY cause and where does it act?

Answer 24

DMN and increases feeding

Question 25

What does the Paraventricular nucleus (PVN) do?

Answer 25

Modulates feeding behaviour

Question 26

NPY, opioids, and GABA all do?

Answer 26

Increase feeding, GABA has mixed effects

Question 27

What does leptin do? (1)

Answer 27

Decreases food intake

Question 28

What is the Suprachiasmatic nucleus and what does it control?

Answer 28

• Human body clock is located in the suprachiasmatic nuclei

* Perception of the light-dark cycle (circadian rhythms)? Appetite or the sensation of hunger → mood/drive to eat

Question 29

What is the amyloid nucleus and what is its role?

Answer 29

• A role for medial amygdaloid nucleus in feeding
• behaviour has been proposed
It is a sub-region of the amygdaloid complex;
Participates in the regulation of food intake

Question 30

What do Ligands: 5-HT (via 5-HT2C and 5-HT1A) do? (2)

a and fi

Answer 30

Decreases appetite

Question 31

What does the release of 5-HT, dopamine and GABA cause?

Answer 31

Decreases appetite

Question 32

What does zimelidine do?

Answer 32

Inhibits the reuptake of 5 - HT from the synaptic cleft, allowing 5-HT to persist in the Synaptic cleft

Question 33

What other inputs control feeding behaviour?

Answer 33

• Orexigenic and anorexigenic neurotransmitters have been found in the hypothalamus
• Orexigenic neurotransmitters: ↑appetite
• Anorexigenic neurotransmitters: ↓ appetite

Question 34

Higher functions can modulate the CNS and peripheral cues what does this cause as a result?

Answer 34

inhibition or stimulation of food intake

Question 35

What overall factors affects how much we eat?

Answer 35

• Food preferences
• Emotions
• Environment
• Life style
• Circadian rhythm – limits food intake to certain times (in some people)
• Individual-based requirements (e.g., neural, metabolic, and hormonal) may alter feeding behaviour

Question 36

What receptors does blood glucose stimulate?

Answer 36

Stimulates gluco-receptors in hypothalamus

Question 37

What do glucostat receptors detect

Answer 37

o ↓[glucose]blood →induces hunger

o ↑[glucose]blood → induces satiety

Question 38

Why do diabetic patients feel hungry despite ↑[glucose]blood?

Answer 38

• Cold environments stimulate feeding while hot environments inhibit appetite
• Afferent input
• Distension of a full stomach inhibits appetite; contraction of an empty one stimulates appetite

Question 39

Describe what happens when the pancreas releases?

Answer 39

1. Insulin is released.
2. Transported to the brain capillaries
3. Causes a catabolic reaction so we get reduced food intake and reduce body fat/ or an anabolic reaction occurs and we get increased food intake and increase body fat
4. Produces white fat

Question 40

Describe the regulation of energy homeostasis

Answer 40

On image

Question 41

Where is leptin produced?

How does it work?

What are the results of leptin secretion?

Answer 41

• Fat cells (adipocytes) secrete leptin (16kDa protein) - gene expressed mainly in adipocytes
• Controls fat stores by operating a feedback mechanism between adipose tissue and brain
• ↑ adipose tissue size → ↑ leptin secretion: High correlation of leptin levels with body fat in humans and animals
• Administration of leptin can decrease food intake, induce weight loss and increase energy expenditure

Question 42

Where is ghrelin released?

When are ghrelin levels high and low?

What does release of gherlin increase?

When can ghrelin be inhibited by?

Answer 42

• Released by stomach, pancreas, adrenals in response to nutritional status
 Circulating levels of ghrelin ↑ preprandially and ↓ after a meal
• Increases central orexins, e.g. NPY, and AgRP (generate hunger signals)
• Secretion of ghrelin can be inhibited by leptin
• Suppresses the ability of leptin to stimulate anorexigenic factors
• Could loss of ghrelin activity determine the success of gastric bypass?
• Leptin and ghrelin act reciprocally on food intake
• Stimulation of their receptors in hypothalamus → changes in food intake

Question 43

Where is Obestatin released and what does it cause?

Answer 43

• Produced by epithelial cells of stomach
• Encoded by ghrelin gene, but it opposes the effects of ghrelin on food intake
Suppresses food intake (suppresses appetite; ↓ body weight gain)
Antagonises ghrelin-induced food intake (and growth hormone secretion)
• Obestatin mediates its effects via different receptors to ghrelin
• Imbalance of ghrelin and obestatin may have a role in obesity?
[Decreased ghrelin/obestatin ratio characterise obesity in women?]