The Human Brain : From Neurone to Nervous System
- Sensory Receptors are nerve endings containing transducers that respond largely to a single specific stimulus, such as probing, changes in temperature or injury.
- Many sensory receptors have specific structures at the terminals of their myelinated axons.
- Other sensory endings concerned with pain and nociception have free nerve endings at the terminals of their unyelinated axons.
- The different types of sensory receptor respond to a particular type of sensory input, and each has its 'private pathway' to the cerebral cortex, where sensations are perceived.
Conscious animals and humans perceive sensations including touch, pain, temperature, vibration, position of the limb, sight and sound that inform them about events in their surroundings or on the skin, and the position of their limbs.
These different sensations are called 'modalities', and perceived sensations occur because messages, i.e. trains of action potentials, are conducted from specific types of sensory receptors in skin, muscles tendons and joints, and the special sense organs - the eye and the ear to the forebrain, and specifically the areas of the cerebral cortex, where specific sensations are perceived.
Key Words : Sensory (afferent) nerves, Types and structures of nerve endings, Rapidy and Slowly adapting receptors, Frequency Code, Thresholds for Sensation, Specificity Theory