Smell (olfaction). Taste (gustation). Vision. Hearing. Balance (equilibrium). Receptors for these senses are concentrated within special structures – the sense organs.
What are the simplest sensory receptors.
Simplest receptors are the dendrites of sensory neurons. Branching tips of dendrites are called free nerve endings
What happens to all arriving information (background)
All sensory information arrives at the CNS in the form of action potentials in a sensory (afferent) fibre. Arriving information is called a sensation. The conscious awareness of a sensation is called a perception. ~1% of the information provided by afferent fibres reaches the cerebral cortex and our conscious awareness. Most info is screened out at the thalamus.
What are our general senses
Temperature. Pain. Touch. Pressure. Vibration. Proprioception (body position). Receptors for these senses are scattered throughout the body.
Provided by paired olfactory organs. Located in nasal cavity, on either side of nasal septum, inferior to the cribriform plate of ethmoid bone. Olfactory organs consist of olfactory epithelium & olfactory glands.
Process of Olfaction
Step 1) When breathing in, air swirls within the nasal cavity.Step 2) reaching the olfactory organs lipid & water soluble chemicals diffuse into the mucus before stimulating olfactory receptors. Olfactory glands secrete mucus to protect the cilia and olfactory cells from extreme chemical smells. Step 3) Dissolved chemicals interact with receptors – odorant binding proteins – on the cilia surfaces.Step 4) Binding of odorants changes permeability of receptor membrane → action potentials. Step 5) Information is relayed to the CNS, where the smell is interpreted.
what are odorants
chemicals that stimulate olfactory receptors
What is the olfactory bulb
It contains axons which lead to the olfactory nerve.Bundles of axons (CN I) penetrate the cribriform plate of ethmoid bone to reach the olfactory bulb Axons leaving each olfactory bulb travel along olfactory tract to the olfactory cortex of cerebrum, (the hypothalamus) & portions of the limbic system.
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