BIOL 1051H Chapter Notes - Chapter 16: Skin Allergy Test, Receptive Field, Sensory Neuron
Sensory Physiology
There are three basic types of sensory receptors, cells that are capable of changing as a
result of stimulation from environmental changes. The three types are mechanoreceptors (those
that respond to physical stimulation), chemoreceptors (those that respond to chemicals) and
photoreceptors (those that respond to light). The table below lists a fourth type, the pain
receptor. However, this is essentially a chemoreceptor as it responds to chemicals released by
damaged cells.
All of these receptors are capable of responding to stimuli in a narrow range of
situations. Some sensory systems have many different types of receptors, such as cutaneous
receptors, and some systems rely on very few receptor types, but variation in the receptors
ability to be triggered by environmental stimuli, such as rods and cones in the retina of the eye.
By interpreting the firing patterns of neurons associated with these different types of receptors,
the brain is capable of sorting through the noise and interpreting patterns that provide us with
usable information about our environment.
For example, there are many types of cutaneous (skin) sensory receptors that respond
to physical stimulation. However, the type of stimulation may vary. We can detect heat, cold,
pressure, prick, pull, etc. This variation is due to the variety of receptors found in the skin as well
as interpretation of a variety of receptor types being activated at the same time.
However, not all parts of the body are created equally when it comes to sensitivity. Most
animals encounter their worlds head first. Consequently, most of our special senses are located
in our heads (hearing, taste, smell, sight). As it turns out we also have more touch receptors in
our faces than in most other parts of our bodies. However, our hands are the most sensitive
parts of our bodies. There are more nerve endings on finger tips than elsewhere so we are able
to sense touch with much greater accuracy than other areas of our bodies. This brings up the
idea of a receptive field. In terms of touch receptors, a receptive field would be the area of skin
served by a single receptor.
One way of measuring the receptive field of touch receptors on skin is the pin prick test.
(The face to face class does this in lab). Here two pins are attached to a device that can move
them different distances apart. The pins are gently placed on an area of skin while the subject is
not watching. The pins are moved from far apart to close together and repeatedly placed on the
subject’s skin until the subject can no longer detect two pricks, but instead senses only one. The
distance between the pins is the size of the receptive field picked up by sensory receptors.
Special Senses: Sight The eye is the organ that detects light. This organ possesses
specialized receptors called photoreceptors which can absorb the energy in light and translate
this into neural impulses sent to the brain. Like other receptors these photoreceptors only
Document Summary
There are three basic types of sensory receptors, cells that are capable of changing as a result of stimulation from environmental changes. The three types are mechanoreceptors (those that respond to physical stimulation), chemoreceptors (those that respond to chemicals) and photoreceptors (those that respond to light). The table below lists a fourth type, the pain receptor. However, this is essentially a chemoreceptor as it responds to chemicals released by damaged cells. All of these receptors are capable of responding to stimuli in a narrow range of situations. By interpreting the firing patterns of neurons associated with these different types of receptors, the brain is capable of sorting through the noise and interpreting patterns that provide us with usable information about our environment. For example, there are many types of cutaneous (skin) sensory receptors that respond to physical stimulation. We can detect heat, cold, pressure, prick, pull, etc.
