Somatosensory System

17 views15 pages
Published on 6 Oct 2011
School
UTSG
Department
Physiology
Course
PSL201Y1
1. General principles of sensory physiology
2. The somatosensory system
Sensory system deals with what you perceive through touch,
smell, sound, vision and hearing. This is all possible due to the
existence of specialized sensory receptors that can detect specific
energy from the environment. An example are photoreceptors found in
the eyes to detect light.
1. General principles of sensory physiology
A) Receptor physiology
The sensory receptors are specialized nerve endings or a
separate cell that detects a sensory stimulus such as touch. Instead of
post synaptic protein receptors, we have sensory receptors that
receive signal from the outside (touch, vision etc.). These signals will
be transmitted to the CNS. The sensory receptors are embedded in
sensory cell membranes. They detect specific signals. The receptors
proteins of the sensory cells will change shape when specific energy
(chemical, mechanical) is received which will allow a chain of events to
occur. How does this signal get transmitted? We know that there
needs to be the generation of an action potential at some point to
transmit the signal to the brain. For example, for touch, there is
pressure applied to the skin. This pressure opens ion channels in the
membrane of the sensory neurons and generate depolarizing current.
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The actual sensory neuron does not have to generate an action
potential if there is the release of vesicles containing
neurotransmitters. The stimulus changes the membrane potential of
the sensory receptor cell and opens calcium channels which in turn
trigger the release of vesicles. The signal is eventually carried to the
CNS. The next cell in line will produce an action potential which will
carry the signal to the CNS. The depolarizing current caused by the
stimulus does not produce any action potential. The current travels
throughout the membrane passively, depolarizing the membrane
sufficiently which allow influx of calcium ions, triggering the exocytosis
of vesicles. We have a sensory cell releasing vesicles to the
neighboring neuron and then this neuron produces an action potential.
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Receptor potential is the change in membrane potential in response to
a stimulus acting on a sensory receptor. Receptor potentials are
graded potentials so they degrade. They cause depolarization which is
caused by the opening and closing of ion channels. If the receptor
potential is greater than threshold, it can generate action potentials
that will eventually reach the CNS.
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Document Summary

General principles of sensory physiology: receptor physiology. The sensory receptors are specialized nerve endings or a. Sensory system deals with what you perceive through touch: general principles of sensory physiology, the somatosensory system smell, sound, vision and hearing. This is all possible due to the existence of specialized sensory receptors that can detect specific energy from the environment. An example are photoreceptors found in the eyes to detect light. separate cell that detects a sensory stimulus such as touch. Instead of post synaptic protein receptors, we have sensory receptors that receive signal from the outside (touch, vision etc. ). These signals will be transmitted to the cns. The sensory receptors are embedded in sensory cell membranes. The receptors proteins of the sensory cells will change shape when specific energy (chemical, mechanical) is received which will allow a chain of events to occur.