Somatosensory Flashcards
vibration, two point discrimination, proprioception
dorsal column
proprioception and muscle status
spinocerebellar tracts
Which sensory receptors are pressure sensitive?
ruffinis endings, pacinian corpuscles, Krause’s bulbs
Which sensory receptors are for fine touch?
Meissner’sm Merkels, root hair plexi
which sensory receptors are for temp/pain
free nerve endings
How are somatosensations transmitted?
1st neuron comes from sensation > 2nd neuron synapse is either in the spinal cord or brain nuclei> 3rd synapse is in thalamus > relayed to fourth synapse somewhere in cortex
pseudounipolar neurons with cell bodies in a dorsal root or cranial nerve ganglion, a central process that terminates in the spinal cord or brainstem, and a peripheral receptive ending in someplace such as the skin, a muscle, or a joint
sensory receptor
pacinian corpuscle
skin, joint capsule, vessel and mesentery walls, periosteum
1 axon
very rapidly adapting
large receptive field
vibration, pressure, proprioception (conscious and non-conscious)
meissner corpuscle
located in non-hairy skin
2-5s axon per MC
low threshold
rapidly adapting
very small receptive field
40% of mechanoreceptors in hand
detect mainly fine, discriminative touch and vibration
Merkels
located in skin
1 axon per cell
multiple cells per axon
low threshold
slow adapting
small receptive field (better spatial resolution)
25% of mechanoreceptors in hand
pressure
ruffini corpuscle
located in skin
1 axon per cell
low threshold
slow adapting
small receptive field
stretching of skin
thermoreceptors adaption
Painful cold = limited adaptation
Cool = rapid adaptation (A&)
Warm = rapid adaptation (C)
Painful heat = limited adaptation (A&, C)
TRPV let these ions in
Ca and Na
neurotransmitters, peptides, lipids, proteases, neurotrophins, cytokines, chemokines. prostaglandins, K +, H +, histamine, bradykinin, serotonin, NGF. Bind to..
inflammatory soup bind to nocioceptors
where do mechanorecptors project
lamina II through VI medially
Where do A& and C fibers project?
Lamina I through V laterally
What is path of lateral or anterior spinothalamic tracts
Sensory nerve axons from DRG enters into Lissauer’s tract and travels 2-3 spinal levels (↑ or ↓)
synapses on 2nd neuron in dorsal horn (lamina I,V)
axon of 2nd neuron crosses to the other side of the spinal cord in the white anterior commissure
then enters either:
1) Anterior Spinothalamic if crude touch/pressure
2) Lateral spinothalamic if pain or temp
where does 3rd synapse occur in the latera/anterior spinothalamic tracts?
the VPL of thalamus
How is pain/temp pathway in head different?
Axons of the DRG neurons relaying pain and temperature sensation from the head and neck (CN5, 7, 9, 10) synapse in the Spinal nucleus of V (Spinal trigeminal nucleus).
The axons of the Spinal nucleus of V neurons cross the midline in the medulla and coalesce to form the Ventral Trigeminothalamic tract and synapse in the Ventral posterior medial (VPM) thalamic nucleus.
How does PAQ manage pain?
periaqueductal gray receives information from the hypothalamus, amygdala, and cortex
send signals to the raphe nucleus, and the reticular formation
From these nuclei, second-order signals are transmitted down the dorsolateral columns in the spinal cord to a pain inhibitory complex located in the dorsal horns of the spinal cord.
enkephalin (type of endorphin) and serotonin are the primary neurotransmitters
from Ib afferents, increases muscle tension
golgi tendon
Where do the dorsal medial lemniscus pathways cross before 3rd neuron?
Fasciculus Gracilis synapse onto the 2nd neuron in the Nucleus Gracilis . Fasciculus Cuneatus synapse onto the 2nd neuron in the Nucleus Cuneatus
The 2nd neuron CROSSES the midline as the internal arcuate fibers in the medulla and coalesce to form the medial lemniscus to the other side of the brain
synapses on the 3rd neuron in the VPL nucleus of the thalamus then to the 4th neuron in the somatosensory cortex
How is vibration, two point discrimination, and proprioception relayed from the head?
Axons of the trigeminal ganglion neurons relaying touch sensation from the head enter the brainstem and synapse in the main sensory nucleus of V in the pons. Those axons either:
1- cross the midline in the pons as the Ventral Trigeminothalamic tract and synapse in the Ventral posterior medial (VPM) thalamic nucleus.
2- ascend without crossing as the Dorsal Trigeminothalamic tract in the Ventral posterior medial (VPM) thalamic nucleus.
What info does cerebellum receive?
nonconscious from Muscle spindle afferents (Ia) and Golgi tendon organ afferents (Ib). This information about muscle tension goes to the cerebellar hemisphere (coordinates muscle movement—same side of the body).
