chemical senses

Question 1

functions of the chemical sense

Answer 1

helps us locate food, asses food safety, derive derive pleasure from eating

Question 2

olfaction

Answer 2

peripheral receptors
olfactory receptor neurons are a component of the olfactory epithelium (1-2 cm area of nasal mucosa in each half of nasal cavity)

olfactory epithelium, unique among sensory systems in that theyre regularly placed, lifespan of 30-0 days and can regenerate after injury, bipolar, cilia within the mucosa

Basal stem cells- gibe rise to new neurons

Question 3

odorant receptors

Answer 3

GPCRs located on olfactory neuron cilia, each neuron only expresses 1 type of odorant receptor, ligand binding–> depolarization

Question 4

olfaction central pathways

Answer 4

olfactory bulb, olfactory neurons project thru cribriform plate to olfactory bulbs where they synapse onto neurons located in clusters (glomeruli)

within each glomerulus is a mitral cell, tuted cell and interneurons,

Question 5

convergence, spatial map, processing

Answer 5

mitral cells take multiple signals from bipolar cells (convergence)

all the neurons that express the same type of receptor converge on one glomerulus (spatial map)

its the combination that causes correct processing

Question 6

olfaction central pathways

Answer 6

olfactory tract

axons of the mitral and tufted cells from the bulb, projects to anterior olfactory nucleus (provides feedback to ipsilateral olfactory bulb), projects via anterior commisure to contralateral olfactory bulb

to primary olfactory cortex (ipsilateral)- medial temporal lobe- uncus

pitiform , periamygdaloid, entorhinal cortex

Question 7

projections fromt he primary olfactory cortex

Answer 7

hypothalamus- physiological aspects of smell (salivation, gastric motility)

limbic structures (amygdala and hippocampus)- emotional and motivational aspects of smell

thalamus- directs attention to stimulus, perception and discrimination of odors

orbital cortex/orbitofrontal cortex/ orbital gyri- flavor

Question 8

most common cause of olfaction

Answer 8

congestion

Question 9

taste sensation

Answer 9

taste= gustatory sensation

flavor= gustatory sense, olfactory sense, general sensation

Question 10

tongue taste

Answer 10

ant 2/3 - CN7 (geniculate ganglion
post 1/3- glossopharyngeal CN9 ( inferior petrosal ganglion)

all terminate in the rostral nucleus solitarius

Question 11

taste peripheral receptor cells in taste buds

Answer 11

taste receptors are epithelial cells

basal cells- stem cells
100s of taste cells per bud
microvilli extend into taste pore, sensory neurons contact taste receptors

bitter salty sweet sour umami

Question 12

taste central path

Answer 12

1st order sensory neurons project to rostral part of solitary nucleus in medulla

2nd order- project to CN motor nuclei/VPM

3rd order- amygdala, hypothalamus and taste cortex- insula