Olfactory-Smell

Olfactory epithelium

Consists of 3 kinds of cells: Olfactory receptor cells Supporting cells Basal cells - Occupies the superior part of nasal cavity. - Covers the inferior surface of the cribriform plate - Extends along the superior nasal concha

Olfactory receptor cells

Olfactory epithelium FIRST-ORDER neurons of the olfactory pathway. - Each one is a bipolar neuron with an exposed knob shaped dendrite and axon coming out through the cribriform plate and ending in the olfactory bulb.

Olfactory Nerve pathway 2

- Axons of olfactory bulb neurons extend posteriorly and form olfactory tracts. - Some axons of olfactory tract project to the primary olfactory area of the cerebral cortex (where awareness of smell begins). - Other axons project to the limbic system and hypothalamus. -- These cause our emotional and memory-evoking responses to odor. - From primary olfactory area, pathways also go to the frontal lobe. -- Here in the orbitofronal area is the region for odor identification and discrimination (right side is stonger for sensing). - Olfactory sensations are the ONLY sensation that reach the cerebral cortex without first synapsing in the thalamus.

Smell information

- Olfactory sensations are the ONLY sensation that reach the cerebral cortex without first synapsing in the thalamus. -Women have keener sense of smell than men, especially during ovulation. -Smoking impairs smell.

Olfactory Nerve pathway

40 bundle of unmyelinated axons of olfactory receptors extend through about 20 olfactory foramina in the cribriform plate of ethmoid bone. - These 40 bundles of axons make the right and left Olfactory (I) nerve. - Olfactory nerve ends in the paired masses of gray matter called olfactory bulbs in the brain. -- within the olfactory bulbs, the axon terminals of olfactory receptors form synapses with the dendrites and cell bodies of olfactory bulb neurons in the olfactory pathway. continues...

Hyposmia

A reduced ability to smell. - Affects 50% of people over 65 - Affects 75% of people over 80 -caused by neurological damage, smoking too much, alzheimer or parkinson's disease, drugs; especially antihistimines, analgesics, steroids.

Smell/Olfaction

Chemical sense. - Arise from interactio of molecules with smell receptors. -10 million-100 million receptors.

Odorants

Chemicals that have an odor can stimulate the olfactory hairs called....

Supporting cells

Olfactory epithelium - Columnar epithelial cellss of the mucous membrane lining the nose. - Provide physical support, nourisment and electrical insulation for olfactory receptors. - Help detoxify chemicals that come into contact with olfactory epithelium. - Innervated by autonomic neurons within branches of facial (VII) nerve which is stimulated by specific chemicals. --Impulses in this nerve stimulate the lacrimal glands in eyes and nasal mucous glands, resulting in tears and runny nose after inhalation of products such as ammonia.

Basal cells

Olfactory epithelium - Stem cells located between the bases of supporting cells. - They continuously undergo cell divsion to make new olfactory receptors-which only live for a few months. --- interesting since olfactory receptors are neurons and mature neurons typically do not regenerate.

Olfactory bulbs

Paired gray matter found in brain. Located in the frontal lobes of cerebrum and lateral to the crista galli of ethmoid bone. - within these, the axon terminals of olfactory receptors form synapses with the dendrites and cell bodies of olfactory bulb neurons in the olfactory pathway

Olfactory hairs

Parts of olfactory receptor cells that respond to inhaled chemicals. - Cilia that projects from the dentrite. (transduction is the conversion of stimulus energy into a graded potential in a sensory receptor).

Transduction

The conversion of stimulus energy into a graded potential in a sensory receptor.

Oflactory glands (Bowman's gland)

Within connective tissue that supports epithelium. - Produce mucus that is carried to the epithelium surface by ducts. - This mucus secretion mositens the suface of olfactory epithelium and dissloves odorants to transduction can happen. - Innervated by autonomic neurons within branches of facial (VII) nerve which is stimulated by specific chemicals. --Impulses in this nerve stimulate the lacrimal glands in eyes and nasal mucous glands, resulting in tears and runny nose after inhalation of products such as ammonia.