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Physiological Psychology 41363
Outline 6
The biopsychology of eating and drinking
I. Eating
A. We need to eat for 2 reasons:
1. construct and maintain our own organs (building)
2. obtain energy for muscular movement and warmth
B. Short-term storage - cells in liver convert glucose to glycogen and store it:
this process is stimulated by insulin: glucose levels fall, inhibit insulin and
stimulate secretion of glucagon
C. Long-term storage - fat (adipose tissue) stored more precisely as triglycerides
D. Why do we start eating a meal?
1. social and environmental factors
2. Need for a variety of nutrients
A. children / cafeteria diet
B. sensory - specific satiety: sick of single food
C. conditioned taste aversion
3. Depletion of nutrients
A. homeostasis
B. What signals depletion of nutrients?
1. Glucostatic theory - body defends a glucose set point: glucose utilization
-diabetes mellitus
2. Lipostatic theory - level of body fat is kept constant
E. What stops a meal?
1. oral cavity - sham feeding studies
- intragastric feeding
2. stomach - pylorous cuff
3. small intestine - cholecystokinin (CCK)
F. Connections between stomach and brain
1. neural mechs - vagus nerve
2. calories signaled by nonneural means
G. Neural mechanisms of eating
1. two areas of the hypothalamus - the lateral hypo and the vetromedial
hypo (VMH):
a. lateral hypo - "hunger center"
b. VMH - "satiety center" - paraventricular nucleus.
H. Eating disorders
1. Obesity
2. Anorexia nervosa
3. Bulimia
II. Drinking behaviors
A. drink to maintain body's fluid levels
-two responses to water deficits
1. drink
2. vasopressin - diabetes insipidus
B. fluid levels must be maintained in four fluid compartments in the body
1. intracellular (70%) - fluid portion of cytoplasm
2. interstitial (26%)
3. intravascular
4. CSF
C. isotonic - concentration of solutes in neighboring compartments is relatively
the same
hypertonic
hypotonic
D. 2 types of thirst
1. Osmometric - occurs when tonicity of interstitial fluid increases:
-osmoreceptors in the anteroventral third ventricle (AV3V) and the
OVLT - lesions to these areas result in no longer drinking
2. Volumetric - occurs when volume of blood decreases
- renin which enters blood and converts angiotensinogen to
angiotensin: also receptors located in the heart that can
stimulate thirst: subfornical organ