7. Appetite

Question 1

Central regulation of appetite

Integration of tonic and episodic signals

Answer 1

NUCLEUS TRACTUS SOLITARUS

a nerve pathway in the brainstem/ hindbrain that carries signals to the ARC in the lateral hypothalamus area

Coordinates reflex to food, is it food, is it good??

Question 2

Long term regulators

Answer 2

Tonic signals

Insulin from pancreas
Lepton from fat cells

Both of these secrete in proportion to fat cells (in the fatter you are, the more you produce)

Act directly on neurones in ARC
have an inhibitory effect on NPY and AgRP Neurones which normally promote food intake

Excite POMC and CART neurones which normally inhibit food intake

Both usually inhibit food intake, balance affects drive to eat. Therefore both are satiety signals

There are increased levels of these in obese people due to more fat cells. So why don’t they stop eating. Resistance, desensitisation

Question 3

NPY and AgRP neurones

Answer 3

In the ARC

inhibited by insulin and lepton

They normally promote food intake

Therefore effect of hormones is to indicate satiety and reduce intake

Question 4

POMC and CART neurones

Answer 4

ARC neurones

Excited by insulin and lepton

They normally inhibit food intake

Therefore net result is to indicate satiety and reduce intake

Question 5

Blundell

Answer 5

2007

When tonic signals are weak, episodic signals also become ineffective

Resulting in no satiety signals!

(In diabetes tonic signals are weak due to desensitisation and resistance, therefore episodic signals also absent. No satiety signals so keep eating)

Question 6

Secondary neurones in the hypothalamus

Homeostatic regulation

Answer 6

Paraventricular nucleus: coordinated neuroendocrine functions and autonomic function such as gastric motility

Ventromedial hypothalamus: satiety and motivation

Lateral hypothalamic area: behavioural and cognitive response- hunger

Question 7

Top down control

Answer 7

Hypothalamus (corticolimbic) functions are mediated by the PFC

Right PFC is associated with inhibition and restraint

Question 8

DelParigi et al

Answer 8

2007

Successful dieters show increases right PFC activation when presented with palatable food

Question 9

Berridge

Answer 9

2009

Components of food reward

Learning,
Liking
Wanting

Question 10

McClure et al

Answer 10

Emotion memory is an important factor in deciding food preference

This is exploited by advertising agencies

Question 11

Grill and Norgen

Answer 11

1978

Facial expressions to nice and nasty tastes
Similar reactions amongst mice and humans

Nice- tongue protrusion
Nasty- gapeing

Feature of implicit liking- shown by even decerebrate animals, in hindbrain

? Innate, feature to enable us to indicate food preferences to ensure we get the right nutrients and also to indicate if food may be bad for us ie poison

Question 12

Yeomans

Answer 12

2002

Implicit liking is controlled by opioids neurotransmitters

Found that naltrexone decreased consumption of palatable food

Question 13

Kringelbach

Answer 13

2004

Explicit liking is a conscious experience in the PFC
Option pathways found in the PFC

Question 14

Implicit liking

Answer 14

Controlled by hindbrain

Option transmitters

Question 15

Explicit liking

Answer 15

Controlled by the PFC along opioid pathways

Question 16

Implicit wanting

Answer 16

Dopamine pathways from VTA to NaCC are most crucial for wanting

Question 17

Volkow et al

Answer 17

1999

The amount of dopamine for optimal reward varied between people

People may overeat because they do not get enough stimulation ‘self medication’

Question 18

Wang et al

Answer 18

2001

Obese people have reduced amount of dopamine receptors due to resistance.
Therefore they eat more to get the same stimulation

Obese people also have increased activation of reward areas to high calorie food. This may act as a motivator to consume it

Brain studies show less grey matter in PFC for obese people- therefore less top down modulation. Less inhibition

Question 19

Short term signals

Answer 19

Episodic signals/ regulators

Sensory input triggers: CEPHALIC PHASE RESPONSE
Central and peripheral responses BEFORE ingestion: salivation, increased gastric motility and insulin secretion etc

Post ingestive hormones: generated by presence of nutrients in the gut. Many different ones- system redundancy. Indicate satiety
Some work directly on the Arcuate nucleus

Some hormones stimulate the vagus nerve- to the brainstem

Most signals are inhibitory

Question 20

Blundell 2006

Answer 20

Quote this paper if saying Anything about tonic or episodic signals

Tonic signals reflect the metabolic state of adipose tissue. If you’re fat, you don’t need to eat because you have enough energy therefore more insulin to give satiety signals

Episodic signals generated by the act of eating. Rise and fall with eating
Most,y arise from GI tract

Integration of these reflects the brains recognition of the dynamic state of energy stores- by the NTS

Rate of gastric emptying is an important action of these