Lecture 1 Notes- Sensory and Motor Systems 03:33
Taste receptor cells have broad tuning; neurons have tuning functions which tune to
They don’t need single neurons for every different type of orientation because single
neurons can tune themselves to different orientations.
Taste stimuli can either pass directly through ion channels; bind to and block ion
channels or bind to G-protein coupled receptors.
Tastants have certain special sodium channels, which can be blocked by certain
drugs. This is how saltiness works.
Larger anions will inhibit the special sodium channels causing the tastant to
determine the sweet sensation.
In sourness, you have protons entering the cells and inhibiting sodium and
potassium channels as well.
In bitterness, it helps to determine poisons. T1R and T2R are the 2 genes that
produce the proteins for taste receptors.
There are 30 different types of receptors that determine bitter tastes. The purpose
of bitterness is to determine what is poisonous.
Bitterness s based on G-protein coupled receptors. The difference btw sensing
bitterness and sweetness is that there are 2 G-protein coupled receptors which
detect sweetness where as bitterness uses only one G-protein coupled receptor.
Umami uses a similar system to sweetness to determine umami taste.
Cranial nerves go directly into the cranium without passing through the spinal cord
where as other nerves pass through the spinal cord.
Two of these cranial nerves are projected from the tongue to the medulla, which are
the facial nerve and the glossopharyngeal nerves.
VPM deals with sensory information from the head. The primary gustatory cortex;
most conscious perception of taste.
Lesions in the cranial nerves could cause loss of taste perception.
Projections to the brain stem hypothalamus and the basal telencephalon.
Labeled line hypothesis- single line for single types of stimuli; individual taste
receptors for each stimulus.
Population coding- a single neuron itself will not give you any information; you need
an entire range of neurons to determine senses. Example, to perceive the taste
temperature and texture of the food you are consuming all at the same time
requires several neurons.
Olfactory epithelium are responsible for mucus production and chemicals have to be
dissolved in mucus in order to be perceived.