• a sensory system is a part of nervous system responsible for processing
sensory information. It enables us to detect changes within our own body
and in our environment.
• The information about the changes within the body is used to maintain
homeostasis.
• a sensory system consists of sensory receptors that receive stimuli from
external or internal environment, neural pathway that conducts information
from the receptors to the brain (i.e., the ascending or sensory tracts in the
spinal cord) and parts of the brain, that deal primarily with processing the
information (i.e., somatosensory cortex) in the parietal lobe.
• The commonly recognized sensory systems are those for vision, hearing,
touch, taste and olfaction.
• all sensory receptors are similar in basic structure. The simplest and most
primitive type of sensory receptor is a single unspecialised sensory or
afferent neuron with its receptor endings meant for detecting stimuli. It is
called primary sense cell e.g., olfactory cells. It is also called 1 st order
neuron.
• Secondary sense cells or 2nd order neurons are modified epithelial cells
that form synaptic connections, via interneurons with the sensory neurons,
and transmit impulses to the cNS e.g., mammalian taste buds.
• The most complex sensory receptors, are called sensory organs. They
consist of numerous sense cells, sensory neurons (1st order, 2nd order, 3rd
order neurons and so on) and associated accessory structures, e.g., eye and
ear have a level of complexity of sense organs.
Sensory Receptors
Class XI
Analysis of various PMTs from 2009-2014
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