Question

10.9 Sharpening of senses through lateral inhibition
10.10 Mechanism of sense of taste for Salty & Sour
10.11 Cranial nerves that convey sense of gustation(taste)
10.12 Mechanism of function of sense of smell(olfaction) receptors(G-protein

Answer 1

10.9: SHARPENING OF SENSES THROUGH LATERAL INHIBITION:

• lateral inhibition is a phenomenon in which a neuron's response to a stimulus is inhibited by the excitation of neighboring neuron
• it makes neurons more sensitive to spatially varying stimulus compared to spatially uniform stimulus
• this happens because the neuron getting stimulated by spatially uniform stimulus is also inhibited by neighbors that are not excited
• the action potential are not spread from excited neurons to neighboring cells

10.10 : MECHANISM OF SENSE OF TASTE FOR SALTY AND SOUR:

• taste buds are small receptors of taste which are scattered all over the dorsal surface of the tongue
• sour taste is primarily caused by acids, mainly due to presence of H⁺ ion
• salt taste is elicited by ionized salts, largely by Na⁺ ion in foods
• more the concentration of these ions in foods, more the taste sensation
• the entry of H⁺ and Na⁺  ions into the cell excites the receptors by opening of specific ion channels and depolarization of the nerve
• an action potential is generated which carry sensations to gustatory cortex via cranial nerves

10.11 : CRANIAL NERVES THAT CONVEY SENSE OF TASTE:

• VII - facial nerve carries sensation from anterior 2/3rds of the tongue
• IX- glosopharyngeal nerve carry sensations from posterior 1/3 rd of tongue
• X- vagus nerve carry sensation from back of mouth

10. 12 : MECHANISM OF OLFACTION :

• olfactory epithelium in the superior part of nostril
• olfactory epithelium consists of olfactory cells which are bipolar nerve cell receptors for smell
• the olfactory substances diffuse in the olfactory epithelium and bind to receptors activating them via G-protein coupled membrane receptors - cyclic AMP pathway causing changes in action potential
• the changes in action potential excite the olfactory neuron and olfactory nerve
• the olfactory nerve carries gustatory stimuli to gustatory cortex through the olfactory tract where the signals are processed

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