7-Hunger & the Chemical Senses Flashcards
How does our blood glucose regulate hunger cues?
low blood glucose will trigger hunger
How do we store glucose in the body?
in the form of glycogen
(mostly in the muscles and liver)
What happens when our bodies detect an increase in blood sugar?
- high blood glucose
- pancreatic insulin secretion
- uptake of glucose by cells
cells use glucose for:
- immediate energy
- store as glycogen
- store excess as adipose
What happens when our bodies detect a decrease in blood sugar?
- liver converts glycogen to glucose
to increase blood sugar - if glycogen stores are low, hunger signals begin
What is NPY and what does it do?
also which structure detects it
Neuropeptide Y
potent appetite stimulant
detected by the hypothalamus
What gives us satiety signals?
- stomach stretch receptors via vagus nerve
- small intestine hormones CCK (cholecystokinin) short term satiety
- high blood glucose detected by liver
How do we store energy in our bodies for the long term?
as adipose tissue (fat)
Why do we store long term energy as fat?
adipose is more calorie dense
Hormones secreted by adipose tissue
name + function
leptin
- reduce appetite
Which gene is responsible for leptin production?
the OB gene
without this gene, leptin production stops
What happens when an animal is given excess leptin?
they develop leptin resistance and no longer experience as salient effects on their appetite
Which behaviours do low leptin levels encourage/signal?
signal us to:
- increase foraging (get more food)
- minimize activity (energy consumption)
Does NPY cause cravings for specific things? If so, what?
Yes, increases consumption of:
- sucrose
- sugar alternatives like saccharin which taste like sugar, but with less calories
- carbohydrates (instead of protein and fat)
Endogenous opioids
description + effects
naturally occuring category of chemical substances which have morphine like analgesic actions on the body
effects palatability and reward driven feeding
analgesic: pain relief
What does Naloxone do with regards to diet/eating?
Blocks opioid receptors
reduces intake of:
- sucrose & saccharin
- saline
What does an opioid receptor deficiency cause with regards to diet/eating?
a lower preference towards sugars
Facts about taste preferences
- taste preferences typically center around identifying nutritional/non-toxic foods
- taste preferences are universal in infants
- determined by lower regions of the brain (evolutionarily older)
Taste responses in infants
(pair 5 tastes to response)
- neutral –> no response
- sweet –> acceptance
- salty –> acceptance
- bitter –> rejection
- sour –> rejection
How does pregnancy affect taste preferences?
Increased taste sensitivity
(likely to avoid toxic foods that the fetus is more sensitive to)
Likely why woman tend to have greater taste sensitivity than men
Taste bud anatomy
locations + composed of
2/3 of taste buds on tongue
1/3 on soft palate and throat
50 - 100 taste receptor cells per taste bud
Types of taste we can detect and why
sweet: energy rich foods
salty: identify electrolytes
sour: warns against harmful foods
bitter: warns against harmful foods
umami: detects amino acids (glutamate & aspartate)
Which areas of the tongue detect which tastes?
The entire tongue can detect all tastes
However, each taste bud may have different proportions of each taste receptor
Taste neuro pathway
- taste receptor
- gustatory nerve
- brainstem: medulla
- thalamus
- gustatory cortex & primary somatosensory cortex
Which part of the brain is responsible for taste reflexes?
brainstem: medulla
will trigger reflexes like gagging
Which part(s) of the brain is/are responsible for taste perception, food texture and smell/flavour?
frontal and insular lobes: gustatory cortex –> taste
parietal lobe: primary somatosensory cortex –> feel & texture of food
frontal lobe: orbital cortex –> combine taste and smell to discern flavour
Neuro pathways for satiety and feeding behaviour
- thalamus
-
hypothalamus & amygdala
regulates: CCK activity & satiety feelings
How is flavour different from taste?
explanation + example
taste is less specific than flavour, taste is largely sensed by the tongue whereas our sense of smell is responsible for flavour
eg: two jellybeans will both taste sweet but differ in flavour (cherry vs green apple)
What causes our perception of spicy food?
capsaicin activates heat receptors, simulating pain signals
How does our nose convert air particles into neural signals indicating smell?
neural pathway from nasal cavity to brain
- odourants dissolve in nasal mucus
- olfactory cilia help odourant bind to
- olfactory receptor cell (10-20 cilia per cell) converts to electric signal
-
olfactory bulb: glomeruli axons which send signals to other brain regions:
- limbic system
- temporal lobe: primary olfactory cortex
- frontal lobe: orbital cortex
