L22 The Chemical Senses (Imported from Quizlet)

Oldest, common

The chemical senses are the ________ and most _________ form of sense

Identify food sources, avoid noxious substances, find a mate or mark territories

What are the functions of the chemical senses?

Cravings

What can deficits in nutrients lead to?

The 5 basic tastes

Cortex

Combination of taste, smell and touch (texture) are combined in the _________

Taste buds

What does the lingual papillae contain?

Groups of taste cells

What are taste buds?

Primarily tongue, also cheeks, soft palate, pharynx, epiglottis

What are the taste organs?

Filiform - spiked, no taste buds, sense texture, most abundant

Foliate - ridges

Fungiform - mushrooms, mainly at sides and front

Circumvallate - pimples, large, contain about half of all taste buds

There are 4 types of lingual papillae, what are they and describe their properties

2000-5000

____-____ taste buds

100

~___ chemoreceptive taste cells per taste bud

Sensory transduction by microvilli

What do taste pores allow?

Which membranous receptors are expressed

What does transduction of different stimuli depend on?

Taste cells appear to only respond to one type of stimuli but taste buds contain taste cells which respond to various stimuli

What is the difference between taste cells and taste buds?

Neurotransmitter release across the synaptic cleft

Gustatory afferents are separate cells to the taste cells, what do they require?

Trillion

Odorants as low as a few parts per _________ can be detected

10, 170, 100

Human olfactory epithelium = __cm2

Dog olfactory epithelium = ___cm2

Dogs have ___x more receptors/cm2

Bipolar chemoreceptive neurones

What are the olfactory receptor cells?

Dissolve, mucus

Odorants must ________ in the ______ layer to reach olfactory receptor cells

Within the cilia at the end of the dendrite

Where are transduction machinery found?

The axon of the olfactory receptor cell

What is the primary afferent neuron?

Thin, unmyelinated

The axons are ___, ______________

Replaced

Olfactory receptor cells are regularly ____________

Regularly replaced

Olfactory receptor cells are one of the few types of neurones that are _________ ____________ in adults

350

Around how many odorant receptor proteins (ORs) do humans have?

One odorant receptor

Olfactory receptor cells only express ___ __________ __________

Multiple odorants

One odorant receptor can recognise _________ ___________

The unique combination of odorant receptors that recognise an odorant

What allows us to distinguish specific odours?

G-protein coupled receptors

Odorant receptor proteins (ORs) are _-________ __________ ___________

Golf

Adenylyl cyclase

cAMP

Cyclic nucleotide gated ion channels

Depolarisation

Ca2+-gated Cl- channels

Further depolarisation

Every OR uses the same downstream pathway, what is it?

~3-5%

How much of the entire genome do odorant receptor protein genes comprise?

Golfs

Transduction occurs via ....?

They cannot smell

Golf knockout mice are anosmic, what does this mean?

Action potentials

What do receptor potentials trigger?

Threshold for action potential firing reached

Large enough receptor potential = ?

Large, increased

Intense stimulus = _____ receptor potential = ____________ action potential firing rate

Only one type of olfactory receptor

Each glomerulus of the olfactory bulb receives input from ...?

Carry information from glomeruli to various regions of the brain

What do second order neurones do?