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23 Cards in this Set
- Front
- Back
Grey and White Matter parts, CNS vs PNS
and exception |
Grey matter - cell body - cortex, nucleus (CNS group of cell bodies), or Ganglion (PNS group of cell bodies)
White matter - myelinated axon. Nerves (PNS) or Tracts (CNS). Grouped into fasciculus/funiculus EXCEPTION: Basal ganglia are major subcortical nuclei in the brain (CNS) but called ganglion still |
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Lemniscus and Peduncle
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Lemniscus is a flat or ribbon-like fiber tract
Peduncle is a massive group of fibers that can be multiple tracts together - gross feature not a pathway |
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Tract naming
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Origin to destination
i.e. corticospinal (cortex to spineal cord), mamillothalamic (mamillary bodies to thalamus), spinocerebellar (spinal cord to cerebellum), corticobulbar (cortex to brain stem) |
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"Big Four" Pathways and general function
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Corticospinal tract - voluntary motor
Dorsal column/medial lemniscus - fine touch (discriminative/non painful), vibration, conscious proprioception (knowing where limbs are in dark) Spinocerebellar tract (dorsal) - unconscious proprioception Spinothalamic tract - pain and temperature |
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What four things can C6 refer to
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Spinal cord level
vertebral segment dermatome ("sensory level") Myotome ("motor level") |
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Corticospinal tract pathway start to finish
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First order neuron (upper motor neuron) originates in precentral gyrus (motor)
Passes through internal capsule and 90% decussates (passes to other side gradually) in CAUDAL MEDULLA to lateral corticospinal tract 10% or so undecussated and go to anterior corticospinal tract Synapse on second order neuron (lower motor neuron) in ventral gray of cord Second motor neuron innervates muscle *Internal capsule is just a landmark NOT part of path. |
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Motor Homonculus
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Motor innervation to body around precentral gyrus. Based on complexity not size.
Goes toes to trunk then shoulder and elbo then wrist to hand to pinky finger to thumb Then to neck then brow then eyelid, eyeball, face, lips, jaw then Jaw, tongue, swallowing Dispraportionately high amount for HANDS, FACE and SWALLOWING Buried more medial than toes area is an area muscles for genital sphincters or voluntary anal sphincters ALL VOLUNTARY MOTOR |
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Upper and Lower Motor Neuron with Sensory Neuron connections
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Upper Motor Neuron - motor cortex to ventral gray horn. Modulatory influence on stretch reflex ar
Lower Motor Neuron - ventral grey horn to NMJ, EFFERENT of stretch reflex arc, MAINTAINS TONE Sensory Neuron - Stretch receptor in muscle and tendon. MAINTAINS TONE, AFFERENT of arc. Synapses with lower motor neuron and Brain and muscle. |
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Neurons that maintain tone of a muscle
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Lower Motor Neuron and Sensory Neuron
Upper can modulate the influence |
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Maintenance of Tone in Upper Motor, Lower Motor, and Sensory Neuron
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Input from stretch receptors causes lower motor neuron to supply tonic stimulation to the muscle
The upper motor neuron modulates this and tends to "override" the tonic signal from sensory neuron |
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Reflex Arc Upper Motor, Lower Motor, and Sensory Neuron
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Afferent Sensory Neuron detects sudden stretch
Signal is strong and results in strong response from lower motor neuron Strong signal usually overcomes mild cortical input from UMN |
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Upper Motor Neuron Lesion Signs and Why
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Spastic paresis - paralysis or weakness due to the hypertonia, contracture is the extreme
Hypertonia Hyperreflexia - exaggerated reflex No muscle atrophy - constant workout Positive Babinski test Because loss of voluntary UMN signal and modulation of tone and reflexes by UMN, circuit of Sensory and LMN is unchecked so exaggerated LMN response |
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Lower Motor Neuron Lesion Signs and Why
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Flaccid paresis/parlysis
Muscle fasciculations - due to random firing, mini twitches (vs constant contract) Hypotonia - gooey Hyporeflexia Muscle atrophy - less tone = less exercise Negative Babinski Because loss of LMN for voluntary movement, and loss of efferent component of reflex arc and tone pathway. Only works when actively tell it (UMN override) to work so no tone and loss of strength and function |
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Babinski's Sign
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Stimulation to sole of foot leading to toes curling downward.
ABNORMAL FINDING If toes curl upward (dorsiflex) suggests UMN inhibition is removed (UMN lesion) and POSITIVE BABINSKI |
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Spasticity and Clonus
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Spasticity - increased muscle tone and increased reflex contraction (UMN)
Clonus - rhythmic contractions (shaking) and relaxations seen when a spastic muscle is stretched |
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Corticospinal Tract Injury signs in a) Cortical stroke
b) Brainstem stroke c) Cervical cord injury d) Lumbar cord injury e) Large lumbar cord injury Spinal Shock caveat |
UMNs synapse at different levels, will see normal signs if lesion is below synapse level (ie. already LMN started and axon left). LMN signs AT site of lesion (b/c damages LMN there) and UMN lesions below lesion (b/c LMN is fine and UMN is not modulating)
a) All UMN signs b) All UMN signs c) No signs to arms (depending on level; low cervical this case), LMN (hypotonia, flaccid paralysis) to hands, and UMN (hypertonia, hyperreflexia) to torso, legs and feet d) No signs to arm, hand, torso, LMN signs to legs and UMN signs to feet e) Covers more area, can have normal till legs and feet both having LMN signs b/c the LMN is damaged Spinal shock - the initial period after an injury, areas BELOW where UMN signs are expected may INITIALLY present as HYPOTONIC, HYPOREFLEXIVE (ie. LMN signs) BUT reflexes and tone gradually RETURNS in exaggerated form of UMN lesion. Can take days to weeks. May incorrectly estimate level |
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Dorsal Columns/Medial Lemniscus Path
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Discriminating Touch, Conscious Proprioception
Starts at receptor, first order neuron axon enters cord at tract of Lissaur, Legs run in fasciculus gracilis (medial dorsal funiculi), arms run in fasciculus cuneatus (lateral dorsal funiculi) Synapse on nucleus gracilis and nucleus cuneatus (caudal medulla) 2nd order neuron leaves nucleus, decussates immediately and continues to thalamus (as medial lemniscus- ribbon like). 3rd order neuron runs from thalamus to post central gyrus (sensory cortex) - end of functional system. Can walk up dermatome to test |
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Sensory Homonculus difference
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Same order around as motor homonculus. area for genitals and sphincters is larger though (buried inside)
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Dorsal (Posterior) Spinocerebellar Tract
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Unconscious Proprioception
Involves Clarke's Column - T1-L3 level. Below runs with fasciculus gracilis (dorsal funiculi) then synapses in Clark's Column. 2nd order neuron joins dorsal spinocerebellar tract At level of Clark's column synapses in it and joins dorsal spinocerebellar tract ABOVE Clark's column when enters runs with fasciculus cuneatus and synapes in lateral cuneate nucleus (caudal medulla) and projects to ipsilateral cerebellum Lateral cuneate nucleus is kind of like a branch of clark's column but runs separately. Goes to cerebellum though NO REAL DECUSSATION - goes to ipsilateral cerebellum |
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Spinothalamic Tract Path
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Tract gives more info than others and can resolve localization of lesion ambiguities
Pain and Temperature First order neurons originate in pain receptors, enter cord at tract of Lissaur, synapse in substantia gelatinosa or nucleus proprius almost immediately Second order neuron crosses anterior white commisure rising about 1-2 levels and then form contralateral spinothalamic tract to thalamus 3rd order neuron from thalamus projects to cortex (technically tract ends at thalamus but projects to cortex) |
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Best of Big 4 tract to resolve localization of lesion ambiguities
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Spinothalamic Tract
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Decussation level of Spinothalamic Tract, Corticospinal Tract, Dorsal Column/Medial lemniscus
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Spinothalamic - almost immediately as enter cord, occuring at every level
Corticospinal Tract - ALL together at caudal MEDULLA Dorsal Columns - ALL together at same level |
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Spinothalamic Findings for
a) Cord Transection between L2-L3 b) Cord Hemisection between L2-L3 |
a) complete loss of pain and temperature below L2 BIL
b) Injury loss of pain and temperature only on OPPOSITE side of injury (b/c crosses over AND retained L3 (b/c crosses anterior commisure while rising so L3 preserved ideally if lesion is only in spinothalamic tract (L3 axon would still be in commisure) Ipsilateral pain and temp preserved |