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Deep pressure is perceived mainly by the Pacinian corpuscles. Examine the demonstration slide of a Pacinian corpuscle. Each corpuscle is an egg-shaped structure consisting of many concentric layers of tissue. Embedded within this structure is a free nerve ending. When the corpuscle is deformed by pressure, an action potential is initiated in the nerve ending. Pacinian corpuscles are found in many areas of the body, including the skin, the mesenteries surrounding the gut, and joint capsules. The Pacinian corpuscles in joints provide the CNS with information on the position of the joints. As such they play an important role as proprioceptors.
You should realize that sensory receptors are not evenly distributed over the surface of the body. Some areas such as the fingertips are more sensitive to touch; these areas have higher densities of sensory receptors, that is, more receptors per unit area.
This is the Paccinian Corpuscle
A cell that responds to one such stimulus by initiating an action potential is called a receptor cell. Receptor cells are transducers: they convert energy in one form – such as light, heat or sound – into energy in an electrical impulse in a neurone. Receptor cells are often found in sense organs; for example, light receptor cells are found in the eye, and sound receptor cells are found in the ear. Some receptors, such as light receptors in the eye and chemoreceptors in the taste buds, are specialised cells which detect a specific type of stimulus and influence the electrical activity of a sensory neurone. Other receptors, such as some kinds of touch receptors, are simply the ends of the sensory neurones themselves.
Structure of a Typical Myelinated Neuron
The Nerve Impulse
The Nerve Impulse
What is the Reflex Arc?
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