Chemical Senses
Chemical Senses
OLFACTION
The sense of smell.
Begins with the detection of molecules suspended in the air
Olfactory stimuli
Must be soluble in fat
Taken through the nostrils and circulated within the nasal cavities connected to the nostrils.
Olfactory epithelium
Thin sheet of cells which contain neural receptors for olfaction
Contains olfactory receptor cells and glia-type support cells that produce mucus
Also contains basal cells which give rise to new receptors when needed
Olfactory receptor cells
Regularly die and replaced in a cycle approximately four to six weeks.
Are bipolar: 1. Branch 1 – reaches out to the surface of the epithelium. Cilia extend from the end of this branch into the mucus that covers the epithelium. Molecules dissolved in the mucus bind and interact with these cilia. The binding of the odorant molecule to a receptor site on a cilium begins in a process resulting to the influx of sodium and calcium into the receptor neuron. 2. Branch 2 –extends to the olfactory bulb. These fibers collectively form the olfactory nerve (CN I) which makes its way into the olfactory bulb.
We use approximately 1000 types of receptor cells to distinguish thousands of different smells.
An individual receptor cell provides general information, but the sorting out the qualities of the odorant molecule is left to higher levels in the brain.
Mammals – have a secondary group of receptors that do not respond to typical odorants, but to pheromones such as compounds found in urine.
Glomeruli
Olfactory bulb structures where approx. 25,000 olfactory receptor axons form synapses on about 100 olfactory neurons.
Olfactory pathways
Axons from olfactory receptor cells -------- glomeruli -------- olfactory bulb (via CN I) ---------- olfactory tracts ----------- olfactory cortex ------------medial dorsal nucleus of the thalamus ---------- insula --------- orbitofrontal cortex
TASTE
For perception of taste, temperature,
OLFACTION
The sense of smell.
Begins with the detection of molecules suspended in the air
Olfactory stimuli
Must be soluble in fat
Taken through the nostrils and circulated within the nasal cavities connected to the nostrils.
Olfactory epithelium
Thin sheet of cells which contain neural receptors for olfaction
Contains olfactory receptor cells and glia-type support cells that produce mucus
Also contains basal cells which give rise to new receptors when needed
Olfactory receptor cells
Regularly die and replaced in a cycle approximately four to six weeks.
Are bipolar: 1. Branch 1 – reaches out to the surface of the epithelium. Cilia extend from the end of this branch into the mucus that covers the epithelium. Molecules dissolved in the mucus bind and interact with these cilia. The binding of the odorant molecule to a receptor site on a cilium begins in a process resulting to the influx of sodium and calcium into the receptor neuron. 2. Branch 2 –extends to the olfactory bulb. These fibers collectively form the olfactory nerve (CN I) which makes its way into the olfactory bulb.
We use approximately 1000 types of receptor cells to distinguish thousands of different smells.
An individual receptor cell provides general information, but the sorting out the qualities of the odorant molecule is left to higher levels in the brain.
Mammals – have a secondary group of receptors that do not respond to typical odorants, but to pheromones such as compounds found in urine.
Glomeruli
Olfactory bulb structures where approx. 25,000 olfactory receptor axons form synapses on about 100 olfactory neurons.
Olfactory pathways
Axons from olfactory receptor cells -------- glomeruli -------- olfactory bulb (via CN I) ---------- olfactory tracts ----------- olfactory cortex ------------medial dorsal nucleus of the thalamus ---------- insula --------- orbitofrontal cortex
TASTE
For perception of taste, temperature,