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Neurology Chapter 14
Motor System 4, Cortical Level
Term | Definition |
---|---|
Prefrontal Cortex | -Most anterior part of cortex -respons 4 manipulating discrete & skilled volun movements thru planning & innervation of muscles -Important in learning new motor task (i.e. child learning to tie shoes) -Site of sequencing, reasoning, thinking, planning |
Signs of prefrontal Cortex lesion | Difficulty with sequencing and planning |
Premotor Cortex | -Gives rise to 30% of Motor Fibers -Info from thalamus, cerebellum, basal ganglia -Has some skilled patterns which are well learned or have become AUTOMATIC (like tying shoes after you've already learned) |
Signs of premotor Cortex lesion | -Lesions here show problems w/ automatic motor task like brushing teeth and tying shoes. -Lesion(s) in the here in the left hemisphere (often extending into Broccas area) are often associated with verbal apraxia |
Primary Motor Cortex | -Initiation of movement -30% of motor fibers -2% of the motor fibers are from Betz Cells which are large to support long axons -Two major tracts come from here: Corticospinal tract and Corticobulbar tract |
Corticospinal tract | -Voluntary Movements -Comes from upper two thirds of primary motor cortex, premotor cortex and sensory cortex -Goes through Corona Radiata to Internal Capsule and Pes Pedunculi in the Midbrain and then to the spinal cord |
Corticobulbar tract | -Responsible for the movement Facial and Associated Muscles (tongue, larynx) –These fibers project to cranial nerve nuclei which give rise to cranial nerves in brainstem) -Comes from the inferior 1/3 of the motor cortex and adjacent to corona radiata |
Primary Sensory Cortex | -Gives rise to the last 40% of motor projections -Project through motor cortex with modulation of sensory information |
Supplementary Motor Area | -From upper two thirds of primary motor cortex, premotor cortex and sensory cortex -Goes through Corona Radiata to Internal Capsule and Pes Pedunculi in the Midbrain and then to the spinal cord |
Lesions in corticospinal tract result in | -symptom of spastic hemiplegia |
Lesions in corticobulbar fibers result in | -symptom of paralysis of facial, lingual, palatal and laryngeal muscles. -Lesion to bilateral nuclie result in less paralysis |
Upper Motor Neuron Lesion | -Flaccid paralysis followed by spastic hemiplegia (aka. Hyper contracted) -Increased Muscle Tone - + Babinski Sign test (toes fan out) -Hyperreflexias -Loss of Abdominal Reflexes -Alternating Hemiplegia (Occurs with lesions in the brainstem) |
Lower motor neuron Lesion | -Eliminates function of the motor unit, if spinal nerve cut off no more info going to muscles for movement -weakness of muscles & reduces tendon reflexes -Muscle tone is flaccid -Seen in muscular dystrophy & myasthenia gravis -Absent/reduced Babinski |