Somatosensory System Flashcards
Exam 3
What are the 4 major modalities of the somatosensory system?
- Discriminative Touch
- Proprioception
- Temperature
- Nociception
What is discriminative touch?
Non-painful/damaging touch
What is proprioception?
Awareness of ones own body position
What is nociception?
Pain sensation
Primary afferents
Peripheral axons that innervate things like skin
Aα is in charge of what? What degree of myelination?
Proprioception- thickly myelinated (20 UM)
Aβ is in charge of what? What degree of myelination?
Mechanoreception- decently myelinated (12 UM)
Aδ is in charge of what? What degree of myelination?
Pain & Temperature- lightly myelinated (5 UM)
C is in charge of what? What degree of myelination?
Pain, temp, itch-longer lasting pain- No myelination (1 UM)
What are the three myelinated primary afferents?
- Aα
- Aβ
- Aδ
What shape are Dorsal Root Ganglion?
Pseudo-unipolar cells
The DRG is a collection of ____________
Cell bodies
Where does the central axon send action potentials to?
The CNS
Where does the peripheral axon send action potentials from and to?
From skin to the DRG
Mechanoreceptors detect ______________of skin and other body parts
mechanical stimulation
What are the two types of mechanoreceptors?
- Sensory receptor cell mechanoreceptors
- Sensory neuron mechanoreceptors
How do sensory neuron mechanoreceptors work?
The stretching of receptors cells opens Na+ channels
What are the two adaptions of stimulus?
- Rapid adaptation
- Slow adaptation
What are the two layers of glabrous?
Superficial and deep layes
What is in the superficial layer? (2)
- Meissner’s corpuscle
- Merkel cells
What is in the deep layers?
Pacinian corpuscle
What are the features of a Merkel cell? (3)
- High acuity
- Sensitive to indentation of skin
- Depth of indentation (edges, points, curves)
What is the signaling process of Merkel Cells?
Synaptic vesicles release NT (serotonin)
What are the features of a Meissner Cell?
- Lower acuity than Merkel, higher than Pacinian
- Rapidly adapting (good for timing resolution)
- Respond to low frequency vibrations (brushing against something)
What is the structure of a Meissner cell?
Surrounded by spiral nerve endings
What are the features of a Pacinian corpuscle?
- Very low acuity
- Rapidly adapting (Good for timing resolution)
- Responds to high frequency vibration (earthquakes)
In pain, primary afferents are preferentially sensitive to ___________
noxious/damaging stimulus
What are the three endogenous opioids?
- Enkephalin
- Endorphin
- Dynorphin
What receptors do Endorphins bind to?
Mu
What receptors do Enkephalin bind to?
Delta
What receptors do dynorphin bind to?
Kappa
What is sensitization?
A decrease of threshold, increase in magnitude of response to a previously effective stimulus
What does the first order of the pathway contain? (2 types of neurons)
- DRG Neurons (everything but face)
- Trigeminal sensory neuron (Face)
What does the first order of the pathway do?
Receive input and carry to spinal cord
What does the second order of the pathway do?
Carries from S.C. to the thalamus/medulla
What does the third order of the pathway do?
Carries info from thalamus/medulla to the primary cortex
Where does pain sensation cross over at?
In the Spinal Cord
Where does touch sensation cross over at?
The medulla
What is the faster pathway for pain nociception?
Neospinal tract
What is the slow pathway for pain nociception?
Paleospinal tract
What fibers is discriminative touch sent by?
A-Beta
Pain and temperature are sent by what fibers?
A-Gamma and C
