spinal cord tracts

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Sensory System of the Spinal Cord

- carries infor frm the body to the CNS (S-A-D)
- when info reaches creebral cortex it is percieved & integrated, then interpreted & given meaning

______________ info from semicircular canals and ______________ info from the joints are transmitted to ________________ and ______________ and processed so it can be sent automatically to the SC and muscles.

vestibular; proprioceptive; brainstem centers; cerebellum

Types of Sensation we are concerned with in PT:

- pain & temp
- proprioception
- stereognosis
- touch

Purposes for Performing a Sensory Assessment:

- determine level of sensory feedback affecting mvmt
- provide basis for initiating a program of desensitization
- determine need for instruction in techniques to compensate for sensory loss (i.e. visual)
- assure patient saftey and prevent secondary complications
- determine over time effects of rehab

Exteroceptors:

- reposnsible for superficial sensations recieved via skin and subcutaneous tissue
- responsible for perception of pain, temp, light touch and pressure

Proprioceptors:

- responsible for deep sensations via joints, muscles, tendons, ligaments, and fascia
- responsible for position sense, mvmt (kinesthesia) sense, and vibration

Cortical

- combination of both exteroceptive and propiroceptive receptors, AND cortical sensory association areas
- responsible for stereognosis, 2 pt discrimination, barognosis, graphesthesia, tactile location, recognition of texture, and bilateral simultaneous stimulation

Stereognosis

the ability to recognize objects by touching and manipulating them

Two Point Discrimination

being able to determine two separate contact points of touch on skin

Barognosis

ability to perceive weight

Graphesthesia

Ability to identify letters, numbers, or shapes drawn on the skin

Anterolateral Spinothamalic Tracts

- carry pain, temp, tickle, touch
- located lateral and ventral aspect of SC
- info enters dorsal root of SC, then ascends or descends for 1 or 2 spinal segments before synapsing with spinal interneuron in the dorsal horn
- spinal interneuron crosses to opposite side of SC & ascends up to the thalamus via the spinothamalic tract where thalamus percieves pain
- fibers go from thalamus to parietal lobes

Lesion of lateral spinothamalic tract will result in:

loss of pain and temp sensation below the level of the lesion on the opposite side of the lesion

T/F: Destruction of the parietal lobes does not cause loss of pain recognition.

False
-

Dorsal Column-Medial Lemniscal System

- concerned with discriminative sensations (i.e. touch, pressure, vibration, mvmt, position sense)
- carries conscious proprioception, vibration & discriminative touch
- sensory info descends on the same side of the SC (if felt on the RLE, it enters R side of SC & ascends up R side of SC to medulla where it crosses over to the opposite side, then goes up to thalamus & parietal lobes.
Posterior Columns also called:
- Fasciculus Cuneatus (UE) and Fasciculus Gracilis (LEs)
- Dorsal Column Leminiscal System

Discriminative touch

- stereognosis, 2 pt discrimination, graphesthesia, etc.

SpinoCerebellar Tracts

- unconscious proprioception (considered unconscious b/c they go to cerebellum
- aides in smooth coordination of motor mvmt; combines with vestibular info to produce muscle tone, balance, and coordination
- enter dorsal root & acsend on same side of SC up to same side of cerebellum, so they never cross

Lesion in the SpinoCerebellar tracts will result in:

loss of unconscious proprioception belwo level of lesion on same side as lesion

Motor System of the Spinal Cord

- initiates mvmt
- maintains mvmt
- controls mvmt

2 Divsion of the Motor System of the SC

- Voluntary Division:
- Corticospinal tract (cortex to SC)
- Corticobulbar tract (cortex to brainstem)
- Involuntary Division:
- Extrapyramidal system

Corticospinal Tract

-cortex to SC
- originates in motor neuron in frontal lobe
- axons descend through the internal capsule to brainstem
- from brainstem to medulla
- 90% cross at the medulla and enter SC at the lateral corticospinal tract

Lateral Corticospinal Tract

- passes to all SC levels
- synapse with intermediary neuron in anterior horn cell at each SC level
- responsib;e for contralateral voluntary fine mvmt

Ventral Corticospinal Tract

- comprised of the 10% of the corticospinal tract that does not cross at the medulla
- cross at SC segment
- responsible for ipsilateral voluntary mvmt

Corticobulbar Tract

- cortex to brainstem
- axons descend through internal capsule to brainstem
- terminate at brainstem in the appropriate cranial nerve nuclei on opposite side of the brainstem

Motor System Components:

- frontal lobe
- descending tracts
- basal ganglion
- cerebellum
- motor neurons in SC
- muscles

Upper Motor Neuron System:

first neuron (cell body & axon) of either the corticobulbar or corticospinal component of the voluntary motor system
- originates in the frontal lobes & continues downward until it synapses with the LMN
- LMN may either be the motor neuron of the cranial nerve or large motor neurons in the anterior horn region of the SC

Lower Motor Neuron System:

- axon synapses directly with skeletal muscle
- anterior horn cell = alpha motor neuron located in the anterior horn of gray matter of the SC
- anterior horn cell is the LMN of the voluntary system to the extremities

Gamma Motor Neuron

- smaller motor neuron also located in the anterior horn cell region
- axons synapse with muscle fibers of the muscle spindle system
- not under direct voluntary control

Corticospinal tracts have a suppressor system located anterior to the precentral gyrus that acts as:

an inhibitor for the LMN to prevent them from over-discharging when responding reflexively to sensory stimuli.

Extrapyramidal Tracts:

- involved in coordination of mvmt, posture, equilibrium, reflexes, locomotion, and complex mvmt
- modulation and regulation of anterior horn cells via ndirect or "extrapryamidal" activity without directly innervating motor neurons

Extrapyramidal System - Motor Tracts

- Tectospinal
- Rubrospinal
- Reticulospinal
- Vestibulospinal
- Olivospinal

Tectospinal Tract

- controls contralateral postural mm tone associated with auditory/visual stimuli

Rubrospinal Tract

- controls motor input of gross postural tone

Reticulospinal

- facilitates and inhibits voluntary mvmt and mm tone

Vestibulospinal Tract

- controls ipsilateral gross postural adjustments subsequent to head mvmts

Olivospinal Tract

- facilitates mm tone

Babinski Sign

- most important sign to indicate lesion of corticospinal tract
- elicited by stroking the lateral aspect of the plantar surface of the foot beginning at the heel and moves forward to ball of foot, then across medially across the base of the great toe
- No lesion: toes flex
- If lesion present in corticospinal tract of that side: great toe extends backward are other toes flair laterally

Most important component of the Babinski Sign:

extensor mvmt of the great toe

Fasciculations:

viable quiverings of a dying muscle fasicle (group of muscle fibers) caused by increased sensitivity

Flaccidity:

severe reduction in tone
- loss of muscle stretch reflexes

Hypotonia:

decreased tone from normal

Spasticity:

increase in tone after a lesion in UMN pathways due to loss of inhibition on the reflex arc from descending impulses
- feel resistance with PROM: tone increases if speed of passive range increases

Determining sensory deficits:

a sensory level is valuable in determining if there is spinal cord disease
- the sensory level on examination is usually 1-2 spinal cord segments below the actual spinal cord lesion

sensory deficit from a spinal nerve lesion:

will be in the dermatome distribution

sensory deficit from a peripheral nerve lesion:

will be in the distribution of that peripheral nerve

sensory deficit from polyneuropathy:

will have a "stocking and glove" distribustion because the longest axons are the most affected

Sympathetic fibers exit the spinal cord between:

C7-L1 (progressively higher cord injures cause increasing problems aith autonomic dysfunction

Parasympathetic fibers exit the spinal cord between:

S2-S4

Injury to corticospinal tract or dorsal columns result in:

ipsilateral paralysis or loss of light touch, proprioception and vibration

Injury to Spinothamalic tract causes:

contralateral loss of pain and temp

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