The Somatosensory System Flashcards
(25 cards)
What is a two-point discrimination test?
informs receptive field density, receptive field size, computing power, special neural mechanisms
What is receptive field size and adaptation dynamics for Meissner’s corpuscle
Small and rapidly adapting - fine touch and vibration
What is receptive field sizes and adaptation dynamics for Pacinian corpuscle
Large and rapidly adapting - deep pressure and vibration
What is receptive field size and adaptation dynamics for Merkel’s disk
Small and slowly adapting - touching texture
What is receptive field size and adaptation dynamics for Ruffini’s ending
Large and slowly adapting - skin stretch, movement, position
What are the four types of primary sensory afferent axons and their main functions?
A alpha - proprioception of skeletal muscle
A beta - mechanoreceptors of skin
A delta - pain and temperature
C - pain, temp,and itch
What are dermatomes?
an area of the skin corresponding to a single spinal nerve
How do shingles highlight dermatomes?
a shingles rash appears in a certain dermatome, highlighting it
How is somatic sensory information from the face area is being processed?
large mechanoreceptors axons from the face -> principal sensory trigeminal nucleus (pons) -> crosses over -> thalamus - > S1 (face area)
Which cranial nerve is involved in processing from the face?
Trigeminal nerve (CN5)
What is homunculus?
cortical somatotopy
What is ‘barrel cortex’?
areas in S1 region which directly correlate to whisker
How can one demonstrate that blocking glutamate transmission can stop activation of one of the barrels?
using CNQX and AP5 can block glutamate transmission of a single barrel without affecting the others
Can somatic sensory cortical map get reorganized with a loss of a digit or an overly extensive use of a digit?
yes, adjusted use of digits leads to reorganization of somatosensory cortex
What are some of the chemicals that mediate pain?
substance P
What are first and second pains?
First pain activates A delta fiber which is myelinated and very fast.
Second pain activates C fiber which is much slower
What is hyperalgesia?
extreme sensitivity to pain.
primary - substance P release lowers pain threshold
secondary - convergence facilitation
What is the major difference between the ascending spinothalamic and dorsal lemniscal pathways?
They’re used for different sensations.
dorsal lemniscal pathway decussates in the thalamus. spinothalamic decussates in the spinal cord
What is a top-down modulation of pain?
neurons of PAG send signal to raphe nuclei to dorsal horns of spinal cord to depress the activity of nociceptive neurons
What areas of the brain are involved in top-down modulation?
Midbrain (PAG) -> Medulla (Raphe Nuclei) -> Spinal Cord (Dorsal Horn)
What receptors are responsible for thermal sensations?
Thermoreceptor TRP channels of varying sensitivity
Ad and C fibers coupled to cold receptors.
C fibers coupled to hot receptors
Is temperature pathway similar to pain pathway?
yes, the organization is the same. use A delta and C fibers. decussate in spinal cord.
How can we distinguish between temperature and pain pathways?
both are spinothalamic
what senses use the spinothalamic pathway?
some touch, temperature, pain
