Lecture 12 Flashcards
Briefly explain how the semicircular canals work in the inner ear.
As the head moves, otoliths in the fluid bend the hair cells, which depolarizes the cells. These hair cells provide input to vestibular nerve cells.
What are the four types of sensory neurons used for somatosensation?
Tactile, Pain, Temperature, and Proprioception
Define tactile.
Response to being touched. Includes Ruffini ending, Meissner’s corpuscle, Pacinian corpuscle. Pacinian corpuscle is the deepest layer.
Define Pain.
Response to noxious stimuli.
Define Temperature.
Response to hot/cold.
Define Proprioception.
Response to position or mechanical movement of the muscle/joint. “Golgi Tendon Organ”
How are somatosensory neurons connected from the skin to brain?
Sensory receptors in the skin travel to the spinal cord (dorsal root ganglion) and then to the brain.
What is a dermatome?
A dermatome is a skin area that provides input to a single sensory nerve
Where does somatosensory information go in the brain and how is it represented? (hint: homunculus)
Somatosensory information is represented in the somatosensory specifically the postcentral gyrus.
Skin areas that are needed for tactile information have a lot more representation in this brain area than others such as the lips or hands.
Briefly describe the phantom limb phenomenon
Phantom limb is when a limb such as the hand is amputated but the area of cortex that represents the hand is still intact.
There are three ways phantom limb sensations can happen:
1. spontaneous activity in the ‘hand’ area of somatosensory cortex
2. stimulation of nerves in the cut wrist
3.the ‘hand’ area can be “taken over” by the ‘face’ area.
Describe the pain reflex arc… does it require the brains input?
Sensory neurons that sense pain send their signals to the spinal cord which in turn sends their signals back to the muscles to contract away from the aversive stimulus. This pain reflex arc does
not involve the brain but signals for pain also go to the brain.
Which neurotransmitter is released in response to pain? What are the post synaptic cells it is released onto? (a picture may be helpful here)
Substance P is the pain neurotransmitter and sensory neurons release substance P onto spinal cord neurons.
What endogenous neurotransmitter inhibits the release of substance P?
The body has its own analgesic process to inhibit pain (gate theory). The endogenous neurotransmitter that inhibits substance P release is the endorphin (endogenous morphine),
Enkephalin. Descending spinal cord neurons from the brain release enkephalin onto the axon terminals of the sensory neurons inhibiting the release of substance P.
If you have endogenous neurotransmitter that limits substance P, why do you still continue to feel pain?
When you are injured and still feel pain it is because prostaglandins and inflammation increase the sensitivity of pain neurons allowing them to still respond.
What is the vestibular system?
It is involved in our sense of balance.
