Motivation Flashcards
What is motivation?
- Driving force
- Physical need
- Wanting,liking
What does the hypothalamus maintain?
Maintains homeostasis by regulating three interrelated functions:
- Endocrine secretions
- ANS
- Emotions and drive/behaviour
What is parabiosis and its effect?
Parabiosis is the sharing of blood circulation between animals
This means blood borne signals are shared and can effect the hypothalamus
What is the effect of parabiosis?
EXAMPLE
- A genetically obese mouse ob/ob fat cells do not produce leptin
- When connected to a normal mouse of whoms fat cells do produce leptin, this will lead to a reduction of obesity in the ob/ob mouse
What is the feedback mechanism of fatty tissues?
- Fatty tissue produce leptin when satisfied
- Leptin travels to the brain and signals to the arcuate nucleus to stop eating
What are the VMN and LH important for the regulation of?
VMN and LH important for the regulation of:
- Body weight/food intake
- Blood volume/osmolarity
What does a VMH lesion cause?
Causes a dramatic increase in food intake and body weight
What role does VMH play in?
VMH plays a role in controlling the cessation of eating
What does a LH lesion cause?
Causes a decrease in food intake
What signalling are both VMH and LH related to?
VMH and LH both are related to leptin signalling
What is the arcuate nucleus important for?
It’s important for control of feeding
What is the response to elevated leptin levels?
- Leptin activates arcuate neurons that release alphaMSH and CART peptides
- Neurons then project to regions that orchestrate coordinated responses of humoral, visceromotor and somatic responses
- PVN
- Intermediolateral grey matter of spinal cord
- Lh
Why are alphaMSH and CART anorectic peptides?
Are anorectic peptides because they diminish appetite
What is the response to decreased leptin levels?
-NPY/AgRP neuron of the arcuate nucleus are activated
-These neurons inhibit neurons in the PVN that control the release of TSH and ACTH from the pituitary
-The neurons in the LH are then activated that stimulate feeding behaviour
-Some of the activated LH neurons contain the peptide
MCH
What receptor do both alpha MSH and AgRP act on?
Both act on the MC4 receptor
What do alphaMSH and AgRP do to the MC4 receptor?
- alphaMSH stimulates MC4 receptor
- AgRP inhibits MC4 receptor
What does the MC4 receptor do when activated?
Activation of MC4 receptor inhibits feeding behaviour
What do LH neurons stimulating feeding behaviour contain?
Contain MCH and Orexin
What does MCH do?
Prolongs consumption
What does Orexin do?
Orexin promotes meal initiation
What are the 3 phases of digestion?
- Cephalic
- Gastric
- Substrate
What happens in the cephalic phase?
- Ghrelin is released when stomach is empty
- Ghrelin then activates NPY/AgRP containing neurons in arcuate nucleus
What does the removal of ghrelin secreting cells do?
Removal of ghrelin secreting cells of stomach are thought to cause loss of appetite
What happens in the gastric phase?
- Gastric distension
- CCK release in intestines
- Insulin also released by beta cells of the pancreas
What signals does gastric distension and CCK release send and what does this cause?
Gastric distention and CCK release signals the nucleus of the solitary tract via the vagus nerve to cause satiety
What happens to levels of 5HT in the hypothalamus in the anticipation of food or a meal?
They rise
What is 5HT levels associated with?
Associated with anorexia nervosa and bulimia with depression
What are examples of natural rewards?
- Food
- Water
- Sex
- Nurturing
What are the stages in the addiction cycle?
Acute reinforcement/social drug taking –>Escalating and compulsive use–>Dependence–>Withdrawal–>Protracted withdrawal–>Recovery
What is positive reinforcement?
It is anything added that follows a behaviour that makes it more likely that the behaviour will occur again in the future
What is negative reinforcement?
It is a response or behaviour that is strengthened by stopping, removing or avoiding a negative outcome or aversive stimulus
