7-Hunger & the Chemical Senses

Question 1

How does our blood glucose regulate hunger cues?

Answer 1

low blood glucose will trigger hunger

Question 2

How do we store glucose in the body?

Answer 2

in the form of glycogen
(mostly in the muscles and liver)

Question 3

What happens when our bodies detect an increase in blood sugar?

Answer 3

• high blood glucose
• pancreatic insulin secretion
• uptake of glucose by cells

cells use glucose for:
- immediate energy
- store as glycogen
- store excess as adipose

Question 4

What happens when our bodies detect a decrease in blood sugar?

Answer 4

• liver converts glycogen to glucose
  to increase blood sugar
• if glycogen stores are low, hunger signals begin

Question 5

What is NPY and what does it do?

also which structure detects it

Answer 5

Neuropeptide Y
potent appetite stimulant

detected by the hypothalamus

Question 6

What gives us satiety signals?

Answer 6

• stomach stretch receptors via vagus nerve
• small intestine hormones CCK (cholecystokinin) short term satiety
• high blood glucose detected by liver

Question 7

How do we store energy in our bodies for the long term?

Answer 7

as adipose tissue (fat)

Question 8

Why do we store long term energy as fat?

Answer 8

adipose is more calorie dense

Question 9

Hormones secreted by adipose tissue

name + function

Answer 9

leptin

• reduce appetite

Question 10

Which gene is responsible for leptin production?

Answer 10

the OB gene

without this gene, leptin production stops

Question 11

What happens when an animal is given excess leptin?

Answer 11

they develop leptin resistance and no longer experience as salient effects on their appetite

Question 12

Which behaviours do low leptin levels encourage/signal?

Answer 12

signal us to:
- increase foraging (get more food)
- minimize activity (energy consumption)

Question 13

Does NPY cause cravings for specific things? If so, what?

Answer 13

Yes, increases consumption of:
- sucrose
- sugar alternatives like saccharin which taste like sugar, but with less calories
- carbohydrates (instead of protein and fat)

Question 14

Endogenous opioids

description + effects

Answer 14

naturally occuring category of chemical substances which have morphine like analgesic actions on the body

effects palatability and reward driven feeding

analgesic: pain relief

Question 15

What does Naloxone do with regards to diet/eating?

Answer 15

Blocks opioid receptors

reduces intake of:
- sucrose & saccharin
- saline

Question 16

What does an opioid receptor deficiency cause with regards to diet/eating?

Answer 16

a lower preference towards sugars

Question 17

Facts about taste preferences

Answer 17

• 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)

Question 18

Taste responses in infants
(pair 5 tastes to response)

Answer 18

• neutral –> no response
• sweet –> acceptance
• salty –> acceptance
• bitter –> rejection
• sour –> rejection

Question 19

How does pregnancy affect taste preferences?

Answer 19

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

Question 20

Taste bud anatomy

locations + composed of

Answer 20

2/3 of taste buds on tongue
1/3 on soft palate and throat

50 - 100 taste receptor cells per taste bud

Question 21

Types of taste we can detect and why

Answer 21

sweet: energy rich foods
salty: identify electrolytes
sour: warns against harmful foods
bitter: warns against harmful foods
umami: detects amino acids (glutamate & aspartate)

Question 22

Which areas of the tongue detect which tastes?

Answer 22

The entire tongue can detect all tastes

However, each taste bud may have different proportions of each taste receptor

Question 23

Taste neuro pathway

Answer 23

• taste receptor
• gustatory nerve
• brainstem: medulla
• thalamus
• gustatory cortex & primary somatosensory cortex

Question 24

Which part of the brain is responsible for taste reflexes?

Answer 24

brainstem: medulla

will trigger reflexes like gagging

Question 25

Which part(s) of the brain is/are responsible for taste perception, food texture and smell/flavour?

Answer 25

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

Question 26

Neuro pathways for satiety and feeding behaviour

Answer 26

• thalamus
• hypothalamus & amygdala
  regulates: CCK activity & satiety feelings

Question 27

How is flavour different from taste?

explanation + example

Answer 27

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)

Question 28

What causes our perception of spicy food?

Answer 28

capsaicin activates heat receptors, simulating pain signals

Question 29

How does our nose convert air particles into neural signals indicating smell?

neural pathway from nasal cavity to brain

Answer 29

• 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