10/28 - Sensory System- Central Processing Flashcards
DRG NEURON:
Proprioception Peripheral process:
Large diameter, heavily myelinated axons carry information from muscle spindles/joint receptors
DRG NEURON:
Touch, Vibration Peripheral process:
Slightly smaller diameter, myelinated axons, carry information from cutaneous receptors
Enters through dorsal root and courses directly to posterior column where they ascend to the brainstem forming the fasciculus gracilis or fasciculus cuneatus.
DRG NEURON’s Central process
TOUCH Modalities
Low Threshold Cutaneous,
Joint & Muscle Receptors.
Touch, Pressure, Vibration, Fine Form and Texture Discrimination, Form Recognition of 3-dimensional objects (Stereognosis)
Conscious Awareness of Body Position (Proprioception)
Limb Movement In Space (Kinesthesia)
Proprioception
Conscious Awareness of Body Position
Stereognosis
Form Recognition of 3-dimensional objects
Input From Lower Limb & Trunk (T6-S5) Forms the ___ .
Fasciculus Gracilis
Input From Upper Limb & Trunk (C1-T5) Forms the ____ .
Fasciculus Cuneatus
TOUCH PATHWAY
1ST ORDER NEURON:
DORSAL ROOT GANGLIA CELLS
Primary afferent axons enter via dorsal root to enter ipsilateral posterior column.
Below T5 only fasciculus gracilis.
Above T5, 2 tracts – fasciculus gracilis (FG) and fasciculus cuneatus (FC).
TOUCH PATHWAY:
2ND ORDER NEURONS
2ND ORDER NEURONS ARE IN CAUDAL MEDULLA IN N. GRACILIS AND N. CUNEATUS.
Axons arising from neurons in these nuclei CROSS the midline and form the MEDIAL LEMNISCUS.
TOUCH PATHWAY:
3RD ORDER NEURON
3RD ORDER NEURON IN THALAMUS (VENTRAL POSTERIOR LATERAL NUCLEUS, VPL).
Axons arising from these neurons project to primary sensory (parietal) cortex
1st-order sensation neurons will always be in a ganglion.
EITHER a DRG or TRIGEMINAL Ganglion (or other cranial nerve ganglion).
Axons from the MAIN SENSORY NUCLEUS, carrying touch information from the ____, cross the midline and join the ______ in the PONS.
Axons from the MAIN SENSORY NUCLEUS, carrying touch information from the FACE, cross the midline and join the MEDIAL LEMNISCUS in the PONS.
Axons from the _____, carrying touch information from the FACE, terminate in the _____.
Axons from the MAIN SENSORY NUCLEUS, carrying touch information from the FACE, terminate in the VPM of the THALAMUS.
UNCROSSED TRIGEMINAL AXONS
Small number of axons remain uncrossed as the dorsal trigeminal tract.
These carry information from the inside of the oral cavity and end in VPM.
Their significance is unknown.
Do the axons from the spinal trigeminal nucleus (pain and
temparature) join the medial leminiscus?
NO.
Axons from the MAIN SENSORY NUCLEUS, (touch from the FACE) join the MEDIAL LEMNISCUS.
What tract is conserned with the Location and Intensity of pain & temperature sensory input
SPINOTHALAMIC TRACT
1st ORDER NEURON of the
SPINOTHALAMIC TRACT
DORSAL ROOT GANGLIA CELLS.
Primary afferent axons enter via dorsal root and SYNAPSE
on neurons in the superficial portion of the dorsal horn
2nd ORDER NEURON of the
SPINOTHALAMIC TRACT
NEURONS IN DORSAL HORN OF SPINAL CORD AT ALL LEVELS.
Axon CROSSES MIDLINE and forms spinothalamic
(anterolateral) tract in the anterior half white matter of the spinal cord.
3rd ORDER NEURON of the
SPINOTHALAMIC TRACT
NEURONS IN THALAMUS VPL (VENTRAL POSTERIOR LATERAL NUCLEUS).
Axons arising from these neurons project to primary
sensory (parietal) cortex and insular cortex.
SPINOTHALAMIC TRACT
Carries Discriminative Aspects of Pain/Temperature:
Location & Intensity of sensory input.
PAIN PATHWAYS FROM THE FACE:
1st ORDER NEURONS
Axons enter in the pons and descend via the Spinal Trigeminal Tract to the medulla where they synapse on 2nd order neurons in the Spinal Trigeminal Nucleus.
PAIN PATHWAYS FROM THE FACE:
2nd ORDER NEURONS
Axons of 2nd order neurons, located in Spinal Nucleus of V,
CROSS the midline and join the Contralateral Spinothalamic Tract as it courses rostrally through the pons and midbrain
Axons from trigeminal nucleus terminate in ventral posterior
medial (VPM) nucleus of the thalamus.
Postcentral-Gyrus
= Primary Sensory Cortex
= S1 of the Parietal Lobe
More posterior gyri of the Parietal Lobe are involved in what?
sensory association
More posterior gyri involved in sensory association areas specialize in what?
spatial orientation and directing attention.
On the somatotopic map, sensory input from what body parts are centralized in the deep fissure that separates the 2 hemispheres?
lower extremeties: feet, toes, legs, genitals
Moleunculus
The mole sensory cortex maps the area of the appendages very precisely and in such a way that a cross section of that part of the brain looks almost like a 2-dimensional image of the appendages.
Information Flow in the Somatosensory Cortex
> > > Brainstem via Ascending pathways (Trigeminal, Medial Lemniscus, Spinothalamic tract, etc.)
> > > to VPM/VPL
to S1 (primary sensory cortex) or SA (association areas).
Area 3:
Basics
Obligatory first step in cortical processing of somatosensory information.
The primary part of the primary cortex.
Intensity, localization….