Question

For EACH of the 5 senses you must include:

- Organ

- Receptor (sensory cell)

- Details on how the brain decodes the message

Answer 1

Ans. Let us first take into account the 5 senses we have been empowered with. These are vision, hearing, smelling, touch and receiving taste of food. For each of these senses, specific sense organs associated with the nervous system carries out these definite functions.

VISION: The sense organs are a pair of eyes. The sensory cells are rod cells and cone cells present in retina of eyes. The rod cells perceive the sense of brightness, while the cone cells perceive the sense of color. There are three types of cone cells - red, green and blue. These cells perceive the sense of vision and transduce the light signal into electrical signal of bipolar neurons. The neurons combine to form optic nerve, which relays these signals to lateral geniculate body of thalamus and then crosses at optic chiasma, and from there to striate cortex of the cerebrum. The signals relayed from two eyes overlap at the visual field. This overlapped image is our field of vision and it gives us the sense of sight.

HEARING: The sense organs are a pair of ears. The sensory cells are hair cells of cochlea. The chambers of cochlea are filled up with fluids. The vibration of these fluids due to sound waves striking the cochlear membrane causes the movement of this fluid and thereby movement of hair cells present in cochlea. The movement of cochlea converts the mechanical signal to electrical signal of neurons. The auditory nerves relay these signals to dorsal and ventral cochlear nucleus and olivary nucleus. From there, the signals are relayed to lateral lemniscus and medial geniculate body of thalamus, and thereby to auditory cortex.

SMELLING: The sense organ is nose. The sensory cells are nociceptors of olfactory bulb of nose. These cells receive the sense of smell and olfactory nerves relay the signal to amygdala and medial olfactory area of cotex.

TOUCH: The sense of touch is received by various receptors underlying the skin. The touch sense like pressure is received by Pacinian corpuscles beneath the skin. These mechanical stress are transduced to electrical signals of neurons associated with these cells. These informations are relayed through corticospinal tract to cerebral cortex.

TASTE: The sense of taste is received by taste buds of tongue. The facial nerves and glossopharyngeal nerves transduce these chemical signals to electrical signals and relay these signals to the ventromedial posterior nucleus of thalamus. The information is relayed from there to gustatory cortex of cerebrum.