Motivation and Decision-Making Flashcards
Motivation
The internal state that causes an animal to behave in a certain way
Examples of biological motivations
*Thirst
*Hunger
*Mate-seeking
*Territorial Defence
Examples of Human motivations
*Biological
*Physiological
A change in responsiveness to a given stimulus may be due to…
*Maturation
*Learning
*fatigue
*Change in motivational state
Describe the homeostatic models of motivation?
To maintain homeostasis, a system requires a detection mechanism to note any deviation from an ideal value or set point ;
it must be able to mobilise the organism to make changes to return it to the ideal value, and it must also have some way to recognise when the desired change occurs and feed back to stop the mobilisation process.
Function of the Hypothalamus
- monitors changes in internal environment
-initates activity (both physiologcal and behavioural) to rectify imbalance
What is the hypothalamus connected to?
has connections to
*cerebral cortex
*Posterior parts of the brain
*Pituitary
It has a rich blood supply
What happens when thirsty?
*When depleted of water, body fluids are
hyperosmotic (saltier than normal), causing shrinkage of specialised neurons ( osmoreceptors ) in the lateral hypothalamus which causes increased rate of firing
*this activates neural circuits that cause
thirst and drinking behaviour
What are the physiological effects of thirst?
physiological effects: Release of antidiuretic
hormone (ADH) from posterior pituitary, stimulates kidney to retain water
Experimental evidence for key role of hypothalamus in thirst
*When a region of the lateral hypothalamus is electrically stimulated or has concentrated solutions introduced into it, goats respond by drinking
* If the lateral hypothalamus of a rat is damaged it does
not drink even when severely dehydrated
Hunger
*a strong motivation to seek out and
ingest food
*the state experienced by an animal as
the satiety from a previous meal wanes
Satiety
*terminates feeding behaviour , even if
food is still available
“feeeding centre” of hypthalamus
Lateral hypothalamus
“Satiety centre” of hypothalamus
ventromedial nucleus
Describe evidence of hunger/satiety
–Damage to the
ventromedial nucleus (VMN; satiety centre “)
causes rats to feed excessively
–electrical stimulation of VMN depresses feeding
–Damage to or stimulation of an area of the lateral hypothalamus
feeding centre “) has the reverse effects
Leptin
produced by adipose tissue, suppresses appetite
PYY (peptide YY)
secreted by small intestine
after meals, suppresses appetite
insulin
rise in blood sugar causes
pancreas to secrete insulin
- physiological role, also
acts on the brain to
suppress feeding
ghrelin
secreted by stomach wall, triggers feelings of hunger
Explain mice with mutant ob gene
Mice with mutant ob gene eat voraciously and grow much larger than normal
ob gene codes for leptin
How is the stomach involved in the control of feeding?
e.g. Stomach fullness inhibits feeding.
Blowfly larva: Distension of gut signals satiety,
CNS inhibits feeding reflex
What is food intake influenced by?
*Smell, taste, texture of food
*Amount of food available
*Stress, anxiety, depression, boredom
*Social custom, habit