Properties of Receptor Potential

Properties of Receptor Potential

Receptor potential has two important properties.

i. Receptor potential is nonpropagated; it is confined within the receptor itself

ii. It does not obey allornone law.

Significance of Receptor Potential

When receptor potential is sufficiently strong (when the magnitude is about 10 mV), it causes development of action potential in the sensory nerve.

Receptor and types of receptor


Mechanism of Development of Receptor Potential

Pacinian corpuscles are generally used to study the receptor potential because of their large size and anato mical configuration. These corpuscles can be easily dissected from the mesentery of experimental

animals. In the pacinian corpuscle, the tip of the nerve fiber is unmyelinated. This unmyelinated nerve tip ions enter the interior of core fiber. This produces a mild depolarization, i.e. receptor potential.

Generation of Action Potential in the Nerve Fiber

Receptor potential causes development of a local circuit of current flow, which spreads along the unmyelinated part of nerve fiber within the corpuscle. When this local circuit of current reaches the first

node of Ranvier within the corpuscle, it causes opening of voltagegated sodium channels and entrance

of sodium ions into the nerve fiber. This leads to the develop ment of action potential in the nerve fiber.

LAW OF PROJECTION

When a sensory pathway from receptor to cerebral cortex is stimulated on any particular site along its

course, the sensation caused by stimulus is always felt (referred) at the location of receptor, irrespective of site stimulated. This phenomenon is known as law of projection.

Examples of Law of Projection

i. If somesthetic area in right cerebral cortex, which receives sensation from left hand is

stimulated, sensations are felt in left hand and not in head.

ii. Sensation complained by amputated patients in the missing limb (phantom limb) is the best example

of law of projection. For example, if a leg has been amputated, the cut end heals with scar formation.

The cut ends of nerve fibers are merged within the scar. If the cut end of sensory fibers are

stimulated during movement of thigh, the patient feels as if the sensation is originating from nonexistent

leg. Sometimes, the patient feels pain in nonexistent limb. This type of pain is calledphantom limb pain.

SPECIFICITY OF RESPONSE – MÜLLER LAW

Specificity of response or Müller law refers to the response given by a particular type of receptor to a

specific sensation. For example, pain receptors give response only to pain sensation. Similarly, temperature receptors give response only to temperature sensation. In addition, each type of sensation depends upon the part of the brain in which its fibers terminate. Specificity of response is also called Müller’

Properties of Receptor Potential

Receptor potential has two important properties.

i. Receptor potential is nonpropagated; it is confined within the receptor itself

ii. It does not obey allornone law.

Significance of Receptor Potential

When receptor potential is sufficiently strong (when the magnitude is about 10 mV), it causes development of action potential in the sensory nerve.

Mechanism of Development of Receptor Potential

Pacinian corpuscles are generally used to study the receptor potential because of their large size and

anato mical configuration. These corpuscles can be easily dissected from the mesentery of experimental

animals. In the pacinian corpuscle, the tip of the nerve fiber is unmyelinated.

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