Lesson 7: Sensory Systems Flashcards
Types of Sensory Receptors
Mechanoreceptors – detect physical deformation caused by mechanical energy (pressure, touch, stretch, motion and sound)
Chemoreceptors –
General receptors – solute concentration
Specific receptors – type of molecule
Electromagnetic Receptors – Detects various forms of electromagnetic energy
Thermoreceptors – detect heat and cold
Pain Receptors (nociceptors) – detect extreme temperatures, certain chemicals and extreme pressure.
Sensory Pathways
All sensory pathways contain four basic functions:
Sensory reception
Transduction
Transmission
Perception
Sensory Reception
The detection of a stimulus by sensory cells
Sensory cells are specialized neurons or epithelial cells.
Some exist alone or clustered in sensory organs such as the eyes and ears.
The term sensory receptor is used to describe not only the sensory cell but also the subcellular structures that
interact with the stimulus.
Sensory receptors may detect stimuli from outside or inside the body.
Transduction
The effect of any stimulus is to open or close ion channels.
This conversion of the stimulus to a change in the membrane potential of the sensory receptor is known as signal transduction.
The change in membrane potential is known as receptor potential and receptor potentials are graded potentials.
Transmission
In many sensory receptors, the transduction of the stimulus into a receptor potential initiates transmission of action potentials to the CNS.
If the sensory receptor is a neuron, it will have an axon that extends into the CNS and it will produce the action potentials
If the sensory receptor is a specialized cell, it will form a synapse with sensory (afferent) neurons and affect the rate at which the afferent neurons produce action potentials.
Perception
Once action potentials reach the brain, circuits of neurons process this input, generating the perception of the stimuli.
Perceptions such as tastes, colours, sounds and smells are constructions in the brain and do not exist outside it.
