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Question#1:

What
is sensory modality?Explain the types of sensory modality?

Answer:

Sensory modality or stimulus modality is the
perception of a stimulus .

                              OR

It is the way to sense  a stimulus .

It is one of the aspects of stimulus .

For example when the receptors of cold or heat are
stimulated by respective stimulus ,registration of temperature modality
occur.The type  and location of a sensory
receptor  that is stimulated by
respective stimulus is  very important
for sensation coding.All types of 
sensory modality work  combinely
to enhance the stimulus when it is needed.

Types
of sensory modality:

Sensory modality includes

1.Light

2.Sound

3.Temperature

4.Taste

5.Pressure

6.Smell

The
light modality:

Light is the stimulus modality for vision .Our eye
is capable of sensing a small portion of electromagnetic light ranging from 380
nm to 760 nm.For th perception of light stimulus,refraction of  light occur so  that it 
hits the retina directly . In eye ,this refraction is the result of
combine action of  iris ,lens and cornea.
The photoreceptor cells of retina converts this transduction of light into
neural activity .The eye is capable of sensing light due to a photopigment
molecule mainly Rhodopsin ,which is usually pink in colour and bleached in this
process.The  ability of human to see
colour is due to the three different types of cone cells in the retina  that contain different photopigments.Each
cone cell is specialized to recognize a specific wavelength (420,530 and 560nm)
or primary colours red ,blue and green.The brain then sort out the wavelength
and colours depending upon the stimulation of respective cone.

2.
Sound modality:

Hearing is the stimulus modality for sound . Sound
is produced by the  change in pressure of
air.The vibrating object produce sound  by
compressing  the air molecule when it
moves towards a point and by expanding the air molecules when it moves away
from a point .Frequency of sound is measured in hertz.Humans are able to
recognize a sound ranging from 30 to 2000 hertz.

Ear drum is stimulated by the vibration in the air
.It collects and send them to the receptor cells .The ossicles connected to the
eardrum pass these vibration to the fluid filled organ cochlea.Due to these
vibrations the stirrup part of cochlea exerts pressure on the oval window.Then
vibrations pass through the liquid of cochlea where sensory organs sense them.

3.Taste  modality :

 In mammals
,the taste receptor cells are present on the taste buds and in
pharynx.Perception of taste is generated by the combination of many sensory
inputs .

4.
Temperature modality:

recognize the change of temperature .

5.
Pressure OR Touch modality:

This modality helps the organisms to understands
their environment .Touch stimulus have to travel  a long distance to reach the brain .Perception
of pressure occur due to mechanoreceptor in the skin.

6.
Smell modality:

This is also clled olfaction .Neuroepithillium  in the nostrils contains the receptors that
detect the smell molecule . synapses of these neurons occur at the olfactory cranial
nerve ,which in turn send message to the brain from where signals are sent to
the olfactory cortex .

Question
#2:

What
is chemoreception ?Give at least two examples of chemoreception?

Chemoreception:

It is the perception of  chemical stimuli from the internal and
external environment  of  an organism.This is the basic characteristics
of each living organism or cell.It helps the organisms to maintain the
homeostasis .

Examples
of chemoreception:

Taste
sense:

Taste is the example of chemorecption which detects substances
like food ,minerals,poisons etc.

Human have taste buds to detect the taste stimuli.Taste
stimuli is deal  by .the pheromones
detection system

 

Smell
sense:

Human have the olfactory system for the sensation of
smell .Its perception occur when the odorant molecules attach to  the specific sites of the olfactory receptors
present in nasal activity.They collect at the structure glomerulus which
transmit messages to the olfactory bulb of brain .

 

 

 

 

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