Lecture 32: feeding and eating

Question 1

***What are the main internal hunger and satiety signals from the body?

Answer 1

1. nucleus of the solitary track in the medulla (NTS) - sense how much blood sugar in the body
2. liver - sends signal to the vagal nerve, enough fat
3. stomach -
4. stetch senses/somatosensory nerve
5. arcuate nucleus of the hypothalamous - receives information from the body, motivations to eat. it includes
   a. leptin - released from body fat
   b. insulin - increase blood sugar
   c. ghrelin - released by the stomach

Question 2

***Describe the major actions of these signals in the hypothalamus and how they relate to anorexia and orexia.

Answer 2

1. lateral hypothalamus - role in drug condition and motivated behaviour; organizes:
   a. orexia - conservation of energy, acquisition of energy, energy reserves, stimulates behaviours and physiological response i.e. feeding or searching for food
2. paraventicular nucleus - important for stress response stimulation of this induces:
   b. anorexia - use of energy, mobilization of energy reserves, catabolic state: fright or flight

Question 3

***How does the mesolimbic dopamine system contribute to appetitte driven by external cues?

Answer 3

• dopamine is not necessarily related to the reward (food). signaling the rat when the food is about to come; prediction signal

mesolimbic importance: not signalling actual reward or pleasure, but it is signaling which things are likely to cause pleasure or reward and motivates behaviour to seek it out.

Mesolimbic dopamine (DA) pathways play a central role in mediating rewarding effects of naturally rewarding stimuli.

• Many “rewarding”stimuli promote dopamine release
from the ventral tegmental area to the nucleus accumbens

• Many abused drugs & addictive behaviors (gambling, eating, shopping) initially promote DA release in n. accumbens & then lead to changes in the homeostasis of DA regulation (required more for same effect)

Question 4

***What role does OFC play in appetite?

Answer 4

OFC - orbitofrontal cortex (orbit of the eye just above the eye)

1.The OFC receives informaton from multple sensory inputs (taste, smell, vision, somatosensory, gustatory, etc)
2, also has reciprocal connections to regions of the brain important for:
a. reward and emotion (stratiu, limbic system)
b. behaviour selection and inhibition (dIPFC)

• IT IS SEEN AS A REGION IMPORTANT FOR LINKING REWARD TO HEDONIC EXPERIENCE AND THEN TO MOTIVATION

• gives people the smell of the banana and vanilla essence
• OFC AND stimulus specific satiety - gives pleasantness, motivation, and placebo pleasantness (water with a labeled that states nicer)

Question 5

***What effect does highly palatable food have on appetite

Answer 5

satiety or disguised fat and carbohydrates preload

more calories = more palatable

reduce the effects of such cues upon satiation causing a larger food intake

Question 6

eating is not about nutrients, it’s about pleasure; and about satisfying a psychological process

Answer 6

eating is not about nutrients, it’s about pleasure; and about satisfying a psychological process