motivation Flashcards
what is the purpose of motivated behaviour?
to satisfy a need
ecto vs. homeo therms
amphibians, reptiles, fish are cold blooded
mammals and birds are warm blooded
what do thermoreceptors cause?
- increased firing rate to heat stimuli
- increased firing rate to cold stimuli
where are thermoreceptors located, how are they prioritized?
CNS (hypothalamus)
hypothalamus -> body core -> skin
where are temperature sensitive cells in the hypothalamus located?
preoptic area (POA)
what does the POA do?
regulates temperature
- focuses on the temperature of the brain
what is the carotid artery?
major blood vessel that provides brain blood supply, temperature of this controls brain’s response to heat/cool body
what are the 3 ways that the hypothalamus may respond to changes in set point?
- humoral
- visceromotor
- somatic motor
what is the humoral reaction?
stimulates/inhibits the release of pituitary hormones into the blood stream
what is a visceromotor reaction?
balance of sympathetic and parasympathetic outputs in the ANS
what is a somatic motor output?
directly infuence actions
“what we physically are going to do to get back to set point”
what occurs when there is a lesion to the POA?
loss of thermoregulation
what are the mechanisms behind fever?
pyrogens increase set point which leads to body getting hotter
what is the lipostatic hypothesis?
brain measures and maintains a body fat level against external conditions and leptin might be the signal that lets brain know about fat storage
what does leptin help do?
control eating
how does leptin work?
1) produced by fat, in levels proportional to fat
2) receptors are in arcuate nucleus of hypothalamus
3) periventricular zone detects leptin
4) lateral hypothalalmus incites feeding behaviour
what does a lesion to the lateral hypothalamus cause?
decrease in hunger -> aphagia
what does a lesion to the ventromedial hypothalamus cause?
increase in hunger -> hyperphagia
what does the lateral hypothalamus control?
hunger
what does the ventromedial hypothalamus cause?
satiety
name anorectic peptides?
AMUSHCART
- alphaMSH
- CART
name orexigenic peptides
AMON
- agRP
- MCH
- Orexin
- NPY
anorexic vs. orexigenic peptides
anorexic - decrease appetite
orexogenic - increase appetite
where does leptin bind to leptin receptors?
the arcuate nucleus
what does bariatric surgery do?
decreases the size of the stomach
- leads to long term weight loss
what are the 3 phases of eating?
before, during and after
1) cephalic: sight/smell of food drive eating, parasympathetic NS activated -> secretion of saliva into mouth and digestive juices into stomach
2) gastric: stronger responses as you eat, want food as you are tasting it
3) intestinal: stomach fills, food moves to intestines, nutrients begin to absorb
what promotes eating in the short term?
- the sequence of eating
- ghrelin
what is ghrelin?
what does it activate?
peptide released by empty stomach into blood stream
- activates: NPY and AgRP neurons that increase hunger
what inhibits eating in the short term?
gastric distention
- stretching of stomach walls by food (mechanosensory axons)
- activates vagus nerve which signals to CNS -> inhibits feeding
CCK
- peptide in cells of intestines and enteric system
- activates vagus nerve and supresses feeding
what is prader-will syndrome?
obesity due to high ghrelin levels
hunger vs. full hormones?
ghrelin=hunger
CCK=fullness
when are ghrelin and CCK levels high vs. low?
start eating
- ghrelin=high
- CCK=low
stop eating
- ghrelin=low
- CCK=high
what does THC cause?
- surge in ghrelin levels
what is hypovolemia?
decrease in blood volume that leads to volumetric thirst
what is hyertonicity?
increase of blood tonicity that leads to osmometric thirst
what is ADH, where is it released?
hormone that increases thirst
- released in the hypothalamus
what is the visceromotor response to hypovolemia?
increase sympathetic activity
- constrict blood vessels to increase blood pressure
what is the somatic response to hypovolemia?
increase motivation to seek and consume water
what is angiotensin II detected by?
subfornical organ
diabetes insipidus?
insufficient ADH or kidney response to ADH
- leads to excessive thirst and dilute urine
- water is not retained
Medial preoptic area of hypothalamus?
Responds to temperature and mediates humoral + visceromotor response (NOT somatic motor b/c lateral hypothalamus responsible for this)
Arcuate nucleus of hypothalamus?
Responds to blood levels of leptin and ghrelin
Paraventricular nucleus of hypothalamus?
Involved in long-term regulation of eating (release hypophysiotropic hormones, receives input from arcuate nucleus, affects sympathetic ANS)
Nucleus of solitary tract (gets input from vagus nerve)?
Responds to gastric distension signals of stomach (eating) Responds to mechanoreceptors in blood vessel walls (drinking)
Subfornical organ?
Responds to elevated angiotensin II blood levels (drinking) b/c outside blood brain barrier (BBB)
OVLT?
Responds to tonicity of blood b/c outside BBB
Suprachiasmatic nucleus of PVZ (hypothalamus)?
Mediates circadian rhythms
Supraoptic nucleus of PVZ (hypothalamus)?
Contains magnocellular secretory neurons
What are high solute levels detected by?
Vascular organ of laminate OVLT
