- Specificity of response-
- Also known as Muller’s law or Muller’s doctrine of specific nerve energies
- A particular receptor gives a particular response only when stimulated by a particular sensation alone- which depends upon the part of brain in which its fibers terminate.
- Sensory Adaptation-
- Also called desensitisation
- It is decline in discharge of sensory impulses when a receptor is stimulated continuously with constant strength
- Depending upon adaptation time receptors can be-
- Phasic: Which get adapted rapidly. Eg. Touch and pressure receptors
- Tonic: Which adapt slowly. E.g., Pain and Cold receptors, muscle spindle.
- Weber Fechner Law-
- It describes response of receptor to increase in strength of stimulus.
- It states that intensity of response of a receptor is directly proportional to logarithmic increase in intensity of stimulus
- R = k log S, where
- k = Constant
- R = Intensity of Response
- S = Intensity of Stimulus
- If stimulus increases 100 times, response increases only double.
- Sensory Transduction
- Conversion of one of energy to another is transduction
- Chemoreceptors convert chemical energy to action potential
- Touch receptors convert mechanical energy to action potential
- Rods and cones convert light energy to action potential
- Receptor Potential-
- Transmembrane potential difference that develops when a receptor is stimulated.
- Also called generator potential.
- Short lived and hence also called transient receptor potential.
- It is non-propagated, i.e., confined within the receptor itself.
- Does not obey all or none law.
- Sufficiently strong receptor potential(10mv) causes development of action potential
- 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.
- E.g. Phantom Limb – In amputated patients, the patient feels the sensation is coming from non-existent leg when the cut end of sensory fibres get somehow stimulated.