Spinal Cord Reflexes Part 2

Question 1

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

Answer 1

Anterolateral System

Question 2

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

Answer 2

Neospinothalamic System

Question 3

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

Answer 3

Lateral Spinothalamic Tract

Question 4

Carries A delta fibers for fast pain

Answer 4

Lateral Spinothalamic Tract

Question 5

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

Answer 5

Lateral Spinothalamic Tract

Question 6

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)

Answer 6

Lissauer’s Tract

Question 7

The primary receiving area for feeling pain & temperature.
-Primary Somatosensory Cortex

Answer 7

Postcentral Gyrus

Question 8

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

Answer 8

Trigeminothalamic Tract (TTT)

Question 9

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

Answer 9

Trigeminothalamic Tract (TTT)

Question 10

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

Answer 10

Anterior Spinothalamic Tract

Question 11

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

Answer 11

Anterior Spinothalamic Tract

Question 12

-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

Answer 12

Anterior Spinothalamic Tract

Question 13

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)

Answer 13

Archispinothalamic System

Question 14

What are the two modulating areas for pain?

Answer 14

1) Substantia Gelatinosa
2) Periaqueductal Gray

Question 15

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

Answer 15

Archispinothalamic System

Question 16

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

Answer 16

Dorsal White Columns

Question 17

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

Answer 17

Fasciculus Cuneatus

Question 18

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

Answer 18

Fasciculus Gracilis

Question 19

Separates the Fasciculus Cuneatus from the Fasciculus Gracilis.
-Generally not found past T8 since we don’t need it below that

Answer 19

Dorsal Intermediate Sulcus

Question 20

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

Answer 20

Dorsal White Columns Pathway

Question 21

-Carries A Beta Fibers
-Very high speed pathway; minimal synapses
-Conscious Proprioception

Answer 21

Dorsal White Columns Pathway

Question 22

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)

Answer 22

Dorsal White Columns Pathway

Question 23

First Order Neurons of the Dorsal White Columns Pathway

Answer 23

Start at the Dorsal Root Ganglion and project to Nucleus Cuneatus or Nucleus Gracilis

Question 24

Second Order Neurons of the Dorsal White Columns Pathway

Answer 24

Begin in the Nucleus Cuneatus/Gracilis, cross and ascend on the Contralateral side as the Medial Lemniscus and project to the Thalamus

Question 25

Third Order Neurons of the Dorsal White Columns Pathway

Answer 25

Start at the Thalamus and project to the Internal Capsule and Cerebral Cortex (postcentral gyrus)

Question 26

Fourth Order Neurons of the Dorsal White Columns Pathway

Answer 26

Neurons in the Cerebral Cortex

Question 27

You aren’t aware of what your proprioceptors are doing. Ex: When walking normally, you don’t have to think about every step. It just comes naturally to you.

Answer 27

Unconscious Proprioception

Question 28

Peripheral tactile & proprioceptive receptors → Dorsal Root (A Beta fibers) → Lamina VI (Nucleus Dorsalis-Clarke, C8-L1) → Posterior Spinocerebellar Tract (ipsilateral) → Inferior Cerebellar Peduncle → Cerebellar Cortex

Answer 28

Posterior Spinocerebellar Tract

Question 29

-Carries A Beta Fibers
-Happens all within one axon. Very streamlined and fast.
-Ispilateral pathway (no crossing)
-Found in the lateral edge of white matter

Answer 29

Posterior Spinocerebellar Tract

Question 30

Peripheral tactile & proprioceptive receptors → Dorsal Root (A Beta fibers) → Lamina VI (Nucleus Dorsalis-Clarke, C8-L1) → Anterior Spinocerebellar Tract (mixed - some fiber cross/some don’t cross) → Superior Cerebellar Peduncle → Cerebellar Cortex (fibers that had crossed before now cross back over to the ipsilateral side before entering the cerebellar cortex)

Answer 30

Anterior Spinocerebellar Tract

Question 31

Lesion to these pathways (2) is ipsilateral to loss of unconscious proprioception

Answer 31

Posterior or Anterior Spinocerebellar Tracts

Question 32

Fibers arrive at the Cerebellum → Dentate Nuclei of the Cerebellum originates new axons that CROSS OVER to the CONTRALATERAL brainstem → Ventrolateral (VL) Nucleus of the Thalamus → Internal Capsule → Precentral Gyrus (primary motor cortex)

Answer 32

Cerebello-Thalamo-Cortical Pathway

Question 33

Cerebellar Cortex injury is _______ to symptoms

Answer 33

Contralateral

Question 34

Fibers originate from the Cerebral Cortex → Pontine Nuclei (via the Internal Capsule) → FIBERS CROSS → enter Cerebellum via Middle Cerebellar Peduncle

Answer 34

Cortico-Ponto-Cerebellar Tracts