B. SENSORY PHYSIOLOGY
1.Concious perception of internal/external environment.
2.Receiver of the sensory stimulus – actually the dendrite end of a neuron. Its job is to take the sensory stimulus and turn it into an electrical signal (nerve impulse) that can travel along the neuron.
3.Since the receptor generates a change in the membrane potential, the receptor makes a generator potential – which is the term for its depolarization.
4.Although the brain interprets the sensation, it projects the sensation back to the location of the stimulus so that it is as though you feel with your fingers not your brain. Adaptation occurs for all sensations except pain. If the stimulus is unchanging, the receptors stop responding – e.g. like not noticing a particular odor after awhile. Afterimage is when the receptor is still responding for a SHORT time after the stimulus is gone. Try this by staring at a light then closing your eyes. You can still see the light for a short period of time because the receptros are still responding. Modality is the ability to tell one sensation from another (e.g. temp. from pressure)
5.If the receptor is external, it is an exteroceptor, internal is an enteroceptor, joints have proprioceptors.
6.Mechanoreceptors respond to physical changes (touch, pressure), nociceptors recpond to pain, thermoreceptors respond to hot/cold and chemoreceptors respond to chemicals (e.g. CO2)
7.The ability to tell 2 closely spaced points as distinct and separate points. The denser the receptors, the better your 2 point discrimination. Lateral inhibition is sharpening of the sensation. If receptors in the center are strongly stimulated and ones toward the periphery are weakly stimulated, the stronger pathway inhibits the weaker pathway.
8.The area served by a receptor. Receptor fields are small where you are sensitive (e.g. lips) and receptor fields are large where you are not very sensitive (e.g. back of thighs).
9.Touch receptors are Meissner’s or Touch corpuscles. They are located near the surface of the skin and respond to light touch. The Pacinian or Lamellated corpuscles are deeper and respond to pressure. Repeated stimulation of tactile receptors leads to vibration. Thermoreceptors are free nerve endings (not encapsulated) and so are pain receptors. Keep in mind that if you over stimulate any receptor you can get a pain sensation (e.g. extreme cold).
10.This occurs when you interpret visceral pain incorrectly as surface/somatic pain. For example, your brain thinks that your left arm and shoulder hurt when it is really visceral pain from your heart.
11. Muscle spindles are skeletal muscle cells with a neuron ending wrapped around it that respond to stretch of the muscle. Golgi tendon organs are located in the tendon and respond to contraction of the muscle. These two receptors work together to provide your brain with “muscle sense” or proprioception. If you close your eyes and have your elbow bent, you know it is bent without looking at it. This is do to proprioception.