Neuro Exam II: Motor, Sensory Reflexes Flashcards
The Motor System of the brain
- organization
- Motor Cortoex (the precentral gyrus in the frontal lobe)
- motr tracts: carry the information (corticobublar(CN) or corticospinal)
- spinal roots: speciifcally the anterior horn in which they leave
- motor neurons
- to the target organ
The Motor Cortex
location
somatotopic organzation
arising spinal tracts
Motor Cortex
- the pre-central gyrus in the frontal lobe (BA: 4)
- signals come from the prefrontal cortex to the motor cortex
Somatotopic organization
- the lower extremities are towards the middle: medial
- the upper extremities & face: lateral
Collectively, the signals travel on pyramidal tracts (because they pass & deccusate at the pyramids in the medulla)
- the corticobulbar tract
- the corticospinal tract
these are efferent nerve fibers of UMN that travel from teh cortex and terminate either in the brainstem (bublar) or in the SC
Corticospinal Tract Pathway
Corticobulbar pathway
corticospinal
from the motor cortex
to the medulla
cross at the pyramids to the contralateral side
travel down to their SC level
synpase at the SC level in the anteriro (ventral) horn
go to target organ
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corticobulbar
from the pirmary motor cortex
to the midbrain & lower medulla
medulla oblongata of the BS specifically
travel through their nuclei (innervate ipslateral and contralateral CN)
UMN and LMN
UMN: upper motor neruon
- those which travel from the motor cortex/BS
- travel to and synpase with a LMN at the BS (if bulbar) or SC (peripheral nerves)
UMN lesion: hyperreflexia, hypertonia
LMN: lower motor neurons
- those which are from the spinal cord (anterior/ventral) horn that travel to teh anterior roots & to the peripheral nerves
- they’re terminated at the NMJ and their target muscle
LMN lesion: weakness, parlysis of the ipsilateral side, hypotonia and decrease or absenct DTR
Sensory System organiaion & pathway
spinothalamic path and dorsal path
Afferent organ
peripheral nerve travels to the spinal nerve
to the spinal pathways (spinothalamic or posterior/dorsal column)
to the sensory cortex in the parietal lobe (BA:1,2,3)
Spinothalmic
- the pain, temperature and crude touch pathway
- travels from the peripherl nerve
- into the SC: synpases and crosses over at the SC level
- travels up to the contralateral sensory cortex
Posterior Column/Dorsal Column
- teh vibration, proprioception and light touch
- travels from teh peripheral nerve
- to the SC: and up
- crossed over and synpases at the level of the medulla
- (travels in the form of the nucleus gracilis or nucleu cuneatus)
Organization of the Spinal cord
- where is white and grey matter
- afferent and efferent fibers are where
Spinal Cord
- the grey matter in the interior: the butterfly shape
- the white matter is the edges: the axons of the nerves
Afferent/Sensory Nerves
- Dorsal root: carry afferent from the peripheral nerves
- DRG: from the doral root & contains the bodies of the primary sensory nerurons which traveled through particular nerves & participate in sensory modualtion and pain transmission (DRG: cell bodies of the peripheral nerve)
- dorsal column: carry the interneuronal signal from the dorsal root & peripheral nerves & DRG into the SC & the axons collect into this long pathway up to the brain
Efferent/Motor Nerves
- Anterior(ventral) horn: the cell bodies for these LMNs which then go out to the target
- anterior root: the efferent nerve motor fibers pass ventrall here and leave the SC this way
Somatotopic organization of the SC tracts
Dorsal Column tract
- sits posteriorly (dorsal) & has the LE more medial and the UE more lateral
Lateral Spinothalamic Tract (pain and temp)
- sits laterally & has the UE more medial then the LE
Ventral Spinothalmic Tract (light touch)
-sits ventral/anterior (small)
Lateral Corticospinal Tract
- sits laterally and has UE more medial than the LE
Ventral Corticospinal tract
- sits ventral and has some motor control (small)
Landmark Dermatomes to know
C3
T4
T10
L1
L3
L4
L5
S1
C3: Front of neck
T4: nipple line
T10: umbilicus
L1: inguinal/groin
L3: does not go belwo the knee
L4: knee to medial malleolus
L5: anteriorn shin/ankle & foot (dorsum)
S1: lateral shin/calf, ankle and foot, lateral malleolous and sole
Upper Cervical Spine
Nerves
C1-C4 = cervical plexus
C1n = geniohyoid & thyrohyoid
C1-2 = rectuc capitus anterior and lateralius
C1-3: longus capitus
C2-3: SCM
C1-3: ansa cervicalis (to the omohyoid, sternohyoid and sternothyroid)
C3-4: levator scapula, trapezius & scalence
C3-5: Phrenic n = to the diaphgram & anterior scalenes
Axillary Nerve
nerve roots
sensory innervation to what
motor to what
Nerve Roots: C5-6
To: the teres minor and the deltoid
motor test: shoulder abduction
sensory: upper lateral cutaneous nerve (the skin over the deltoid)
Radial Nerve
nerve roots
Motor innervation
sensory innervation
Radial Nerve: C5-T1
innervates: triceps brachii & extensor forearm muscles (for wrist)
Motor testing: wrist extension & tricep extension
Sensory
- most of the posterior forearm
- lateral dorsum of the hand
- dorsal aspect of fingers 3-5
Musculocutaneous Nerve
- roots
- motor innervation
- sensory innervation
Musculocutaneous nerve
Roots: C5-7
Motor innervation
- the anterior arm muscles (biceps brachii, coracobrachialis & brachilais)
- test: via elbow flexion
Sensory Innervation
- lateral cutaneous nerve of teh forearm & lateral aspect of the forearm
Median Nerve
Roots
Motor Innervation
Sensory Innervation
Median Nerve: C6-T1
Motor Innervation
- flexor & pronator mucles in the anterior forearm (pronator quadraus, flexor digitorum profundus, flexor pollicus longus)
- thenar muclse and lumbricals
- test = wrist flexion, thumb adduction, pinching & interosseous testing (abdut fingers against pressure)
Sensory Innervation
- palmar cutaneous branch (lateral palm)
- digital cutaneous branch ) digits 1-2 & 1/3 of 3) from palmar surface
Ulnar Nerve
roots
motor innervation
sensory innervation
Ulnar Nerve: Roots C8-T1
Motor Innervation
- anterior forecarm, flexor muslces and intrinsic hand muscles (except those from the median nerve: lumbricals and thenar)
- test = wrist flexion & hand interosseous testing
Sensory Innervation
- medial 1/2 of the palmer aspect of the 3rd and 4th and 5th digit
how to accurately test dermatomes for sensory loss
common complaints
- radicaulr pain (burning, tingling, numbness and aching)
test
- pin prick and light touch sensations in the dermatomal pattern
Femoral Nerve
Roots
Motor Innervation
Sensory Innervation
Femoral Nerve: L2-L4
Motor Innervation
- thigh muscles which flex the hip (iliacus, sartorius, pecineus)
- thigh muscles which extend the knee (quadraceips femoris)
- test = knee extension
Sensory Innervation
- cutaneous branches to anterior medial thigh
- cutaneour bracnhes to the medial side of teh leg and foot