Question

Choose one of the sensory systems and explain how that system transforms energy or matter into a signal that the nervous system understands. Please describe the environmental signal itself, the organ which takes in said signal, and the pathways involved in ensuring the signal reaches the brain as well as which brain structures receive the signal.

Answer 1

OLFACTORY SYSTEM

Olfactory receptors are located on yellowish pigmented olfactory mucus membrane.these receptors are bipolar neurons.each neuron has a short and thick dendrite with expanded end called ad olfactory rod.from these rods 10-20 cilia projects to the surface of mucosa.

The environmental signal here is SMELL.and organ involved in its perception is NOSE.

the odoriferous(odour producing) substance combines with the receptors on the surface of cilia.the receptors has G protein and this causes activation of G protein by removal of its alpha subunit. This causes activation of adenylyl cyclase enzyme which convert ATP to cAMP.cAMP activates a gated sodium channel that leads to opening of the gates which leads to entry of large numbers of sodium ions ito the receptor cell cytoplasm. This cause membrane potential to increase and produce an action potential that passes through olfactory nerve.

From olfactory nerve the PASSAGE of action potential is,

Olfactory nerve-->pierce cribriform plate of ethmoid-->reach olfactory bulb-->synapse with mitral and tufted cells-->axons of mitral and tufted cells forms olfactory striae

Olfactory stria are 3 in number.

*medial striae(axons of tufted cells)-They cross midline in anterior commissure to form synapses with granule cells in opposite olfactory bulb.

*lateral striae(axons of mitral cells)-Runs to olfactory cortex of same side.

*intermediate striae-Ends in olfactory tubercle.

Here OLFACTORY CORTEX(including anterior olfactory nucleus, piriform cortex, amygdala, olfactory tubercle, and entorhinal cortex) is the brain structure receiving signals.