Lecture 7 Motivated decision making Flashcards
(45 cards)
What is thirst an example of?
A Homeostatic system
How does the thirst homeostatic system work?
Thirst is detected by the detection system, and the behavioural correction system adjusts accordingly (drink/ stop drinking)
What are the 3 components of homeostatic system?
1- signalling system
2- detection system
3- Behavioural correction system
How much of the body is fluid?
55% (women)
66% (men)
2/3 is within each cell 1/3 is outside the cell either in blood (20%) and the rest is in between tissues
What are the two thirst signalling systems?
- Intracellular fluid concentration detection
2. Extracellular fluid concentration in blood
What is intracellular fluid concentration detection?
‘Osmotic thirst’ - How much fluid there is in the cell
There needs to be a balance of how much in in/outside
What is extracellular fluid concentration in blood?
‘Hypovolemic thirst’- How concentrated blood is)
Hypo- low
volemic - volume
Where is osmotic thirst detected?
In lateral preoptic area in hypothalamus
What is the hypothalamus involved in?
Many homeostatic and regulatory processes and communicates between endocrine, peripheral and central nervous system.
What is angiotensin
A peptide produced by the kidneys sensing blood concentration
what two systems are involved in hypovolemic thirst?
1- subfornical organ
2- OVLT (Organum Vasculosum of the lamina terminalsi)
What does the subfornical organ do?
- Senses angiotensin (a peptide produced in the kidneys)
- Senses blood concentration
What does the OVLT do?
- Senses angiotensin
- Receives info on blood volume
What do both the subfornical organ and the OVLT have?
Ordinary capillary walls, not blood-barrier walls.
How does motivated drinking behaviour work?
The lateral preoptic are of the hypothalamus, the subforical organ and the OVLT communicate with reward centres
What reward centres are communicated with in motivated drinking?
The orbital frontal cortex and the ventral striatum
What is the anticipatory satiety mechanism for thirst?
The act of swallowing or stomach distention that tells hypothalamus to inhibit the drive to drink
How long does it take for intra and extra cellular fluid concentration to be at optimum level?
15-20 minutes
Why do most humans and animals drink?
Out of habit
What did Harris et al 1993 do?
Gave rats a B1 deficient diet
Gave them 2 foods, one enriched with B1
Rats preferred enriched food.
This did not happen when more choice was available
What happened when rats were fed cafeteria food?
They became obese, even in enriched environments with an exercise wheel.
What are the individual differences with rats being fed cafeteria food?
Some rats gained more weight than others, not all cafeteria rats became obese, but some did
What did B.J Rolls (1981) find?
Gave one food type to satiety to human participants, and then obtained pleasantness ratings for other foods
Much smaller satiety effect for different foods
Variety leads to greater calorie intake
- Offer 1 verus 4 types of sandwich for lunch - Greater intake with 4 types than with 1
What are the major differences between hunger and thirat
Is it adaptive to eat more than immediate needs to ‘bank’ calories as fat
Different types of food needed.
