The Nervous System - Receptors

Receptors in the Nervous System

Receptors are specialised cells that detect changes in the environment, also referred to as stimuli. These changes can be external (e.g. temperature) or internal (e.g. blood glucose levels).
The receptors send information about these changes to the central nervous system (CNS), resulting in a response from the body. This information is transmitted as electrical signals called nerve impulses.
There are different types of receptors, each sensitive to a different form of stimulus. For instance, rod and cone cells in the eyes react to light, chemoreceptors in the nose sense chemicals in the form of smells, and thermoreceptors in the skin detect changes in temperature.
Pacinian corpuscles are mechanoreceptors present in your skin, joints, and other tissues. They respond to mechanical pressure such as vibration or pressure changes, transforming these mechanical stimuli into electrical signals.
Another example is photoreceptors (rod and cone cells) located in the retina of the eye. Rod cells enable vision in dim light but do not distinguish colours, while cone cells allow us to see colours but require bright light.
Chemoreceptors, found in areas like the nose and taste buds, respond to chemical stimuli. In the nose, they detect volatile chemicals we perceive as smells. In the tongue, they recognise dissolved chemicals as various tastes.
Sense organs like the eye, ear, and skin contain various types of receptors. They are responsible for our five senses: sight (eyes), hearing and balance (ears), taste and smell (mouth and nose), and touch, temperature, and pain (skin).
The process of converting a form of energy (e.g. light, sound, chemical, etc.) into electrical energy in the form of nerve impulses is called transduction.
The sensitivity of receptors plays a crucial role in how strong a response is. Threshold stimulus is the minimum intensity of stimulus required to generate a nerve impulse.
Accommodation is a process of adaption by receptors to constant stimulation resulting in decreased response. This prevents overload of the nervous system by unnecessary information.
Most receptors are connected to sensory neurons, but some are part of a neuron, for example, dendrites of sensory neurons.
Each receptor has a reception field. The smaller it is, the more sensitive the region is to the stimulus. The size of receptive fields varies for example, fingertips have very small, dense receptor fields which results in high sensitivity.