Receptors in animals
Receptors are specialized as neuronal structures to detect diverse stimuli from the internal and external environment.
Receptor specificity
Adequate stimulus is preferred, if large magnitude of stimuli that can provoke response from many receptors.
Some receptors are designated by nature to respond to different stimuli. Example: Nociceptors to detect pain which may be due to temperature, pressure, or chemicals. These are termed as Polymodal receptors.
Receptive field is the region in the sensory surface of afferent neuron which detects the stimuli to generate response upon stimulation.
Mechanism of action of a receptor
Incoming stimuli transduce the membrane potential into the receptor or generator potential. The protein structures within the sensory receptors absorb energy from stimuli to undergo conformational change which in turn activate signal transduction pathway.
This allows change with appropriate voltage gated channel to induce the impulse generation through the proper neurotransmitters. Sensory reception include signal reception, signal transduction, signal amplification, signal transmission to higher centres and perception at the integrating centre.
Properties of Sensory Reception
Primary afferent neuron is the cell whose axon carries the information to higher centres. Sensory receptor cells are present in the sense organs.
Generator potential vs Receptor potential
If the potential developed by sensory receptor which also serve as primary afferent neuron, is termed as Generator Potential.
If sensory receptor cell is different from primary afferent neuron the potential developed in the sensory receptor cell is termed as Receptor Potential. Mechanism of signal transduction varies in each of these situations.
Receptor characteristics
Receptors have the ability to convert other form of energy in to electrical energy i.e. action potential, causes transduction if adequate stimuli is applied.
They have differential sensitivities to different stimuli. The permeability of the receptor is modified and ends up in graded receptor potential.
They show different adaptability to a stimulus and speed of adaption varies with receptors. Each receptor has specific acuity i.e. discriminative ability.