Spinal Cord Reflexes Part 2 Flashcards
Sensory pathway for Pain, temperature, and crude touch. Formed by the:
-Paleospinothalamic System (Protopathic Pain & Crude touch - can feel something but can’t tell if it’s smooth/rough): Anterior Spinothalamic Tract
-Neospinothalamic System (Pain & temperature): Lateral Spinothalamic Tract
Anesthesia will cause loss of pain, temperature, and crude touch sensation
Anterolateral System
Forms the Lateral Spinothalamic Tract.
-Carries sharp/pricking pain that is easily localized (Epicritic)
-Also helps you judge temperature as being hot vs cold, etc.
-Fairly fast pathway
-Fairly new tract developmentally
Neospinothalamic System
Nociceptors → Dorsal Root → Dorsolateral Fasciculus (Tract of Lissauer) → Lamina I (posteromarginal nucleus) → Lamina II & III (Substantia Gelatinosa) → Lamina IV & V (Nucleus Proprius) → FIBERS CROSS in the Anterior White Commissure → Lateral Spinothalamic Tract forms and ascends on the contralateral side → VPL of the Thalamus → Internal Capsule → Postcentral Gyrus
Lateral Spinothalamic Tract
Carries A delta fibers for fast pain
Lateral Spinothalamic Tract
Lesion causes loss of detection of pain/temperature on the contralateral side. Loss of function will be from that level on down; above it is ok
Lateral Spinothalamic Tract
Fiber pathway that goes up and down for a segment or two before eventually going up to the brain. Fairly fast pathway.
-Only located in the Pain & Crude Touch pathways (Neo, Paleo, and Archi)
-Also called the Dorsolateral Fasciculus
-Terminates in Lamina I (Posteromarginal Nucleus)
Lissauer’s Tract
The primary receiving area for feeling pain & temperature.
-Primary Somatosensory Cortex
Postcentral Gyrus
Tract that carries epicritic & protopathic pain, temperature, and crude/fine touch
-Carries A Delta & C fibers
-Pain & temperature of the face
-Part of the Neospinothalamic System
Trigeminothalamic Tract (TTT)
Nociceptors → Trigeminal Nerve (CN V) gives off fibers that originate in the Trigeminal Ganglion → Spinal Tract V → Spinal Nucleus V → FIBERS CROSS and ascend via the Contralateral Trigeminothalamic Tract (TTT) → VPM of the Thalamus → Internal Capsule → Postcentral Gyrus
Trigeminothalamic Tract (TTT)
Nociceptors & Pressure Receptors → Dorsal Root → Dorsolateral Fasciculus (Tract of Lissauer) → Lamina I (Posteromarginal Nucleus) → Lamina II & III (Substantia Gelatinosa) → Lamina IV & V (Nucleus Proprius) → FIBERS CROSS in the Anterior White Commissure → Anterior Spinothalamic Tract on the contralateral side → Reticular Formation to Diffuse Thalamic Nuclei, Periaqueductal Gray, and/or VPL of the Thalamus → Internal Capsule → Postcentral Gyrus, Cingulate Gyrus, & Insular Cortex
Anterior Spinothalamic Tract
Lesion in this pathway will cause loss of detection of pain & Crude touch on the contralateral side. Loss of function will be from that level on down; above it is ok
Anterior Spinothalamic Tract
-Carries C Fibers (protopathic pain - difficult to localize)
-Has lots of collateralizing off, with some fibers going to the Reticular Formation, some going to the Periaqueductal Gray, and the rest going up to the Thalamus to project to the Cerebral Cortex
-Not as important as the Lateral Spinothalamic Tract
Anterior Spinothalamic Tract
A very old pathway developmentally (found early in the life of an embryo). Very slow pathway (lots of synapses and structures)
-Multisegmental, Bidirectional (some go up/some go down, takes a while to get to the brain), and Diffuse
-Found in the Propriospinal Tract (Fasciculus Proprius): the one outlined in brown around the border of the Gray Matter
-Carries Protopathic Pain (Deep, aching pain: C Fibers) and Crude Touch
-Some fibers travel in the MLF (the extension of the vestibulospinal system that gives off collaterals to the motor nuclei of CN III, IV, and VI)
Archispinothalamic System
What are the two modulating areas for pain?
1) Substantia Gelatinosa
2) Periaqueductal Gray
Nociceptors & Pressure Receptors → Dorsal Root → Dorsolateral Fasciculus (Tract of Lissauer) → Lamina I (posteromarginal nucleus) → Lamina II & III (Substantia Gelatinosa) → Lamina IV & V (Nucleus Proprius) → Propriospinal Tracts (Fasciculus Proprius) where fibers are mixed (Some cross and some don’t cross) → Reticular Formation to the Diffuse Thalamic Nuclei, Periaqueductal Gray, Hypothalamus, and/or VPL of the Thalamus → Internal Capsule → Postcentral Gyrus, Cingulate Gyrus, & Insular Cortex
Archispinothalamic System
Function is to monitor the Kinesthetic senses, also called Conscious Proprioception.
-Discriminative touch: can tell where you’re being touched, and if it was rough/smooth
-2 point Discrimination: can tell the difference between two points that are applied to your skin
-Vibratory Sense: tuning fork applied to Mastoid Process
-Stereognosis: can tell what something is without looking at it
-Kinesthetic Sense: knowing where your limbs are in space without looking at them
Dorsal White Columns
Involved with fine tactile stimulation & conscious proprioception of the Upper Limbs and Upper Trunk.
-Located laterally in the Dorsal White Columns
-Begins at about T4-T8 and runs up
Fasciculus Cuneatus
Involved with fine tactile stimulation & conscious proprioception of the Lower Limbs & Lower Trunk.
-Located medially in the Dorsal White Columns
-Present throughout the entire spinal cord
Fasciculus Gracilis
Separates the Fasciculus Cuneatus from the Fasciculus Gracilis.
-Generally not found past T8 since we don’t need it below that
Dorsal Intermediate Sulcus
Peripheral Tactile & Proprioceptive Receptors → Dorsal Root (A Beta Fibers) → Fasciculus Gracilis (LE & LT) OR Fasciculus Cuneatus (UE & UT appearing at T4-T8) in the Medulla → Nucleus Gracilis OR Nucleus Cuneatus → FIBERS CROSS and are now called Internal Arcuate Fibers → Medial Lemniscus → VPL of the Thalamus → Internal Capsule → Postcentral Gyrus
Dorsal White Columns Pathway
-Carries A Beta Fibers
-Very high speed pathway; minimal synapses
-Conscious Proprioception
Dorsal White Columns Pathway
Lesion in this causes loss of ability to detect 2-point discrimination, kinesthesia, etc.
-No perception of impulses from the lesion on down
-Loss of sensation is Ipsilateral to the injury (pathway doesn’t cross until the Medulla)
Dorsal White Columns Pathway
First Order Neurons of the Dorsal White Columns Pathway
Start at the Dorsal Root Ganglion and project to Nucleus Cuneatus or Nucleus Gracilis
Second Order Neurons of the Dorsal White Columns Pathway
Begin in the Nucleus Cuneatus/Gracilis, cross and ascend on the Contralateral side as the Medial Lemniscus and project to the Thalamus
