The Somatosensory System Flashcards
What 4 sub-senses are in the somatosensory system?
1.) Touch
2.) Pain
3.) Temperature
4.) Body location/Proprioception
Where does touch sensation occur?
The skin
What is the skin?
A combination of hairy and glabrous areas
What are 6 touch mechanoreceptors?
1.) Pacinian Corpsucle
2.) Merkel’s Corpsucle
3.) Ruffini’s Ending
4.) Meissner’s Corpsucle
5.) Free Nerve Ending
6.) Hair Follicle Recpetors
What is the largest touch mechanoreceptor?
Pacinian Corpsucle
What do hair follicle receptors do?
Respond to gross movement of the hair
Why are there so many types of mechanoreceptors?
There are many types of touch sensations to be transduced
Touch receptors vary in sensitivity to what 3 ways?
1.) Movement frequency
2.) Touch pressure
3.) Receptive field
What are receptive fields?
Areas on the skin to which an individual mechanoreceptor is sensitive
What is two-point discrimination?
How close do 2 points have to be to be perceived as one touch?
What is adaptation?
Duration of sustained touch time before mechanoreceptor stops responding
What is the role of a Pacinian Corpsucle?
Responds to compression and then release on the capsule that surrounds the axon
How do somatosensory neurons respond to movement?
Mechanosensitive ion channels respond to movement by opening Na+ or Ca2+ channels
How do somatosensory axons travel?
Travel from mechanoreceptor to spinal cord; enters SC through dorsl root ganglia
How many pairs of spinal nerves are there?
31
What is a dermatome?
The territory of touch sensitivity for each spinal nerve
What is the benefit of dermatome areas overlapping?
If one dorsal root is severed, the person does not lose all touch sensation in that dermatome region
What is the dorsal column-medial lemniscal pathway?
A distinct pathway that carries touch sensation up the SC to the brain (different from pain and temperature pathways)
What is the dorsal column-medial lemniscal pathway?
1.) Ascends up the dorsal column of the SC
2.) Terminates at dorsal column nuclei near the base of the medulla
3.) Axons then decussate to opposite side of the brain
4.) Ascend through medial lemniscus in brainstem
5.) Synapse with ventral posterior nucleus of the thalamus
6.) Project and terminate at the primary somatosensory cortex
Cranial nerve touch sensation reflects activation of which 4 cranial nerves?
1.) Trigeminal
2.) Facial
3.) Glossopharyngeal
4.) Vagus
Where is the primary somatosensory cortex located?
On the post-central gyrus in the parietal lobe
Which of Brodmann’s areas contain the primary somatosensory cortex?
Areas 1-3
What is somatotopy?
The map of the body’s touch sensations onto the brain
What does the inferior portion of the primary somatosensory cortex represent?
Pharynx, tongue, jaw
