Physiology of olfaction

Ability to smell is olfaction.

Olfaction processincludes different cells and their pathways:

1. Olfactory tract
2. Olfactory bulb
3. Mitral cells
4. Olfactory cells
5. Glomerulus
6. Sustentacular cells
7. Bowmen’s capsule
8. Olfactory cilia

• Olfactory cilia are sensory receptors that respond according to the chemical stimuli it received.
• Cilia reacts to stimuli and activate olfactory cells
• Bowmen’s gland produce mucous
• Now, axons of olfactory nerve pass towards olfactory bulb

Olfactory bulb lies over cribiform plate

• Secondary olfactory cells called mitral and tufted cells carry odorant and transmit it to olfactory tract.
• Olfactory tract transmit smell into three sites of brain

1. Frontal cortex: conscious
2. Hippocampus : odor memory
3. Hypothalamus and amygdale: emotional and motivational

Excitation of olfactory cells

• Olfactory membrane when received odorant then it get diffuse to mucus
• This bind to receptor protein
• Receptor protein get bound with G-protein which activate adenylyl cyclase
• Here, ATP converts into AMP this opens sodium ions channel
• Now, action potential generate this excites olfactory nerve and it passes to CNS.