Something about d special senses...

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Something about d special senses...

Post  aalina on Fri May 02, 2008 2:07 pm

Err...
I got myself confused dis morning while reading Tortora...
Hahaha... (-.-")

Nway, I got 1 Q...
Wat does it mean y 1st order neuron??
I tot I understand fully wat it meant until I read sum confusing sentences in Tortora...
Let me just quote it 4 u ppl...

4m page 577 of Tortora 11th Edition, section Anatomy of Taste Buds and Papillae...
"...the gustatory receptor cells synapse with dendrites of the first-order neurons that forms the first part of the gustatory pathway. The dendrites of each first-order neuron branch profusely and contact many gustatory receptor cells..."

4m page 576 of Tortora 11th Edition, section The Olfactory Pathway...
"...the terminals of olfactory receptors - the first-order neurons - form synapses with the dendrites and cell bodies of second-order neurons in the olfactory pathway."

I guess all of u shud oredy awared of dis...
D olfactory epithelium n taste buds haf 3 types of cells; olfactory receptor cells(olfactory epithelium) o gustatory receptor cells(taste buds); supporting cells n basal cells... Rite?

So, if the olfactory receptor cells is d 1st-order neuron, then y gustatory receptor cells is not consider as d 1st-order neuron as well??...
Or, did I miss-interpret d meaning in Tortora??
Or izit sum typing error??
Or wat??
drunken
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1st order neurone....

Post  fazrul_9588@yahoo.co.uk on Fri May 02, 2008 4:33 pm

from what i understand

reference: pg 586 general properties of receptor, anatomy and physiology, k saladin

receptor act as transducer which convert one energy to other energy... Receptor can be a neurone itself for example touch, pain and smelling. That why we can called the olfactory receptor is 1 st order neurone as the receptor itself is a neurone.

the other type of receptor is epithelial cell which act as receptor, not the neurone itself for example hearing and taste... hearing is using hair cell as receptor but the 1st order neurone is cochlear nerve.. for the taste sensation, gustatory cell act as receptor and it will synapse at base of the cell to the 1st order neurone either nerve facial (VII) or glossopharyngeal nerve (IX).. thus we cann't called the receptor as 1 order neurone...

hopefully this explanation make u clear about it and if there is mistake, let me know to correct myself...

thanks..

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Re: Something about d special senses...

Post  Will*I*AM on Fri May 02, 2008 5:53 pm

thanks a lot for the good explanatioin!
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sensory receptors

Post  malina ramlan on Fri May 02, 2008 7:15 pm

assalamualaikum.

as far as i know, the sensory receptors can be divided into 3 groups structurally. one is free nerve endings of the first sensory neuron such as to transmit impulse for pain, thermal etc. then we have the encapsulated nerve endings of the first sensory neuron (vibration, pressure, touch) and the last one is separate receptor cells that forms synapse with first order sensory neurons.

now the one that you're asking is about the 3rd group of neurons. the gustatory receptor cells in taste buds are separate or specialized cells that will form synapse with the first order sensory neurons. lets recap back the definition of first order neurons. neurons that transmit impulse from somatic receptors to spinal cord or brain stem, or easier, from the PNS to the CNS.

the transmission can be via the cranial nerves or the spinal nerves. back to the specialized cell, the gustatory cells will undergo an increase of receptor potential. receptor potential is different from graded potential because it will not cause firing of action potential upon reaching treshold. since it is generated in a separate cell (but is closely related to the first order neuron), an increase of receptor potential will happen upon increased stimulus intensity. this will trigger the release of neurotransmitter from synaptic vesicles when the treshold is reached. since the cells forms synapse with the first order neuron, the release of neurotransmitter will cause the production of post synaptic potential at the first order neuron to which the impulse of taste is conveyed to the CNS and ultimately to the primary gustatory area in the brain at the base of the postcentral gyrus just superior to the lateral cerebral sulcus (area 43).

other examples of this type of sensory receptor is like hair cells for hearing and photoreceptors (rod and cone cells) in the retina.

I love you study well everyone!!!
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Re: Something about d special senses...

Post  aalina on Sat May 03, 2008 7:59 am

Thanx Fazrul...
Thanx Mal...
4 d gud explaination.

I guess I understand dy...
Hahaha... ;P
Besides, Cindy con4m it wif me too.
She say like wat Fazrul n Mal say there. Very Happy
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