Where are ideas about movement formed?
where does planning (organization of movement) occur
Pre motor cortical areas: -premotor cortex (lateral) -supplementary motor area (medial and going over longitudinal fissure) Areas are active prior to movement.
Parietal association cortex
Area behind the central gyrus (areas 5 and 7 -brodman) -integrated picture of where your body is lined up (proprioception) + visual input. -Lets ou know where you are in relation to the environment. -invovled with planning areas of brain = coordinate movement. Signals to pre central cortex which sends signals down the spinal cord.
lesions in motor planning areas (premotor cortical areas or the posterior parietal cortex) -diffuclty using body part to perform complex voluntary actions. -contralateral - no obvious muscle weakness, no paralysis, no alteration in tone. no decreased reflexes. -They just can't organize movement ex. pour water into a cup. -they can't plan a movement
Who is in charge of the "execute" part of motor movement?
primary motor cortex (precentral gyrus) -origin of corticospinal tract
Large Betz cells
Lamina layer 5 in primary motor cortex -project directly to motor neurons (no interneurons)
What type of connection do Corticospinal tract neurons have with motor neurons ?
Direct connection to motor neurons - -enable fine movements -- finger muscles.
What is the somatotopical organization of the pre central gyrus?
-Lower extremity are most medial. -Trunk -upper extremity is most lateral
Where is the corticobulbar tract in relation to the pre central gyrus?
superior to the sylvan fissure and in the pre central gyrus. (Broadmann area 4)
Does the motor cortex "code" for specific muscles?
no. it codes for purposeful movements. (slide 8 -- experiments with monkeys) 1. stimulation to one site elicits completely different sets of muscle patterns depending on start position 2. motor cortex codes for endpoints (goals) of movements.
Corticospinal tract (overall tract)
(Aka Pyramidal track) -Starts in precentral gyrus and traces down brainstem (ventral surface of brain). -decussates at bottom of medulla (pyramidal decussation) -travesl down spinal cord and innervates motor neurons directly or indirectly
Where does the corticospinal tract originate?
Area 4 of Bodmann but there are also inputs from area 6 (rostral), 3,1,2 (all are caudal).
What path does the corticospinal tract take (in cortex) to start heading down to brainstem?
Posterior limb of the internal capsule
Does the corticospinal tract decussate?
yes. pyramidal decussation. -caudal medulla. =lateral corticospinal tract
Does all the corticospinal tract decussate?
no. 10% of tract does not decussate. -forms the anterior corticospinal tract
Arrangement of motor neurons going to thumb as it goes from pre central gyrus --> thumb
-thumb is most lateral in precentral gyrus. - It is most anterior and medial structure when it hits the caudal medulla. -after it hits the caudal medulla it continues as the most medial structure in both the lateral and anterior corticospinal tracts.
Based on the location of the lateral corticospinal tract… what (general) types of muscles will it innervate
since it is lateral to the ventral horn: -distal muscles
Based on the location of the anterior corticospinal tract… what (general) types of muscles will it innervate
since it is ventral to the ventral horn: -promixal muscles
What happens if there is stroke in the middle cerebral artery?
- can affect the posterior internal capusl. -Everything would be affected. So if right middle arterial artery was blocked --> affect corticospinal tract for left side of the body --> contralateral hemiparesis.
Typical features of stroke of middle meningeal artery?
-head tilted -Paresis of lower facial muscles -upper limb is flexed -lower lim is extended -foot is inverted
Lateral corticospinal tract projects into what?
Projects directly or indirectly to motor neurons and motor interneurons in the lateral vernal horn to distal muscles
Anterior corticospinal tract projects into what?
Remains ipsilateral in ventral column Projects bilaterally to motor neurons and interneurons in medial ventral horn (to proximal and trunk muscles)
Where are deficits of corticospinal tract if lesion happens above the caudal medulla?
Affects contralateral side of body
Lesions in the spinal cord will affect who?
symptoms on the same side of the lesion below the level of the lesion.
What are some deficits associated with lesion of Corticospinal tract
-loss of skilled movement -Babinski sign -Upper motor neuron syndrom
projects ipsilaterally (some bilaterally) to medial alpha-motor neurons throughout length of spinal cord. They contribute to posture and gait-related movements (proximal muscles) -activated by premotor cortex (planning) Also control autonomic centers and receives output from cerebellum
What is function of mesencephalic and rostral pontine reticular formation
modulates forebrain activity
Caudal pontine and medullary reticular formation
premotor coordination of lower somatic and visceral motor neuronal pools. (pons--> down) -goes all the way down spinal cord to control proximal and trunk muscles
Pontine retriculospinal tract
Mainly ipsilateral ---facilitates extensors: soleus, back muscles
Medullary reticulospinal tract
Mainly ipsilateral --some bilateral -inhibits extensors
Elaborate sensory system that helps monitor head position, movement, and acceleration -helps keep balance -medial and lateral vestibular system
Medial vestibular system -originates?
Arises from CN #8 : arises in rostral medulla--medial vestibular nucleus -goes only to cervical layer --> head and neck -projects bilaterally to control head position in response to acceleration -also controls eyes
Lateral vestibular system -originates? -travels where?
Arises from CN #8 : lateral ponto-medullary junction -- lateral vestibular nucleus -ipsilateral and travels all the way down the body -synapses with medial LMNS -- proximal muscles (facilitate extensors)
arises in superior collicus (midbrain) and projects contra laterally in the medialwhite matter to the medial ventral horn of CERVICAL SPINAL CORD (only goes to this level). Orientates head movement in response to visual or auditory stimuli. -helps coordinate eyes in addition to head
originates in red nucleus of midbrain. -gets input from cerebellum too. Travels with the LCST to control hand movements (in lateral feniculus) -flexor muscles! Only projects in cervical cord.
what are the lateral pathways talked about in this lecture?
Lateral corticospinal tract Rubrospinal tract
What are the medial pathways talked about in this lecture
2 reticulospinal tracts (contralateral) 2 Vestibulospinal tracts (contralateral) tectospinal tract (contralateral) Anterior corticospinal tract (ipsilateral/bilateral)
upper motor neuron syndrome effects
lesion can produce an initial "spinal shock" -- complete shut down of spinal circuits that can last some days. Then this is followed by UMN syndrome - weakness -no atrophy or mild atrophy -no fasciculations -increased reflexes -increased tone (looks tight/ spastic)
who do upper motor neurons project to? What do they control?
control alpha-motor neurons directly or indirectly. -control the excitability of spinal reflexes
UMN disorder that causes an increase in muscle tone -- increased resistance to passive movement (move hand/wrist) -more resistance in beginning of movement vs. end. -velocity dependent -- if go fast = more resistance. - loss of descending inputs = increased firing rate of alpha or gamma motor neurons.
ex. 4+ or 5+ on tendon (patellar/ achillies) or any tendon
reflex so strong that muscle contracts a number of times in a 5-7 hz oscillation
Flick fingernail downward. Causes rebound extension of finger and flexion + adduction of thumb.
extent of hyprtonia depends on area of brain damage 1. lesion above midbrain 2. lesion below midbrain
1. Decorticate lesions: Upper extremeties flex, LE extended -rubrospinal tract still helping out 2. Decerebrate lesions: all limbs extended -hit rubrospinal tract (facilitates flexion)
What are the CN that have lower motor neuron components?
CN#3,4,5 (jaw dropping),6,7,9,10, 11
CN #7 is tested in two parts
1. Upper neuron: close eye, raise eyebrows 2. retract mouth * in brainstem there is an upper part of the nucleus that goes to the upper part of the face and a lower part of nucleus that goes to a lower part of face.
Corticobulbar tract -originates? -path? - important thing to know about CNs. -Lesions causes what?
originates in precentral gyrus -travels down next to corticospinal tract -goes through genu of internal capsule and is more medial in cerebral peduncle. -ends in brainstem (bulb). Originates CN bilaterally except for CN 7. -upper portion is bilateral -lower portion is contralateral only! CN 12 is also mostly contralateral Lesions to one corticobulbular tract = paralysis to contralateral lower face.
Causes of upper motor neuron syndrome
-trauma -stroke -Multiple Sclerosis -Amyotrophic Lateral Sclerosis (ALS) -Cerebral palsy
What motor deficit would you expect if someone had stroke to lateral cortex (arms and face)
contralateral lower-face and arms.
motor effects when there is a Lesion in internal capsule
-affects lower contralateral face as well as entire body.
-pure motor hemiparesis
common with lacunar strokes
*recall that all motor pathways pass through internal capsule!
Effect of a Stroke in area of lower limb placement (cortex)
loss of motor/sensory in lower contralateral limb -- leg.
Effect (motor) of lesion in spinal cord
Ipsolateral deficit (because pathway has already crossed and is goin gdown to innervate motor neurons on the same side.