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BMB_2_15_11 - The Motor System Motor Control...

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Unformatted text preview: The Motor System Motor Control Striated (skeletal) muscle: (Attach to bones to move limbs, somatic processes) Performs voluntary movements. Smooth muscle: (Arteries, stomach, bladder, iris, autonomic processes) Performs involuntary movements. Muscles only Generate force When they Contract So muscles are always arranged in pairs for moving joints in both directions Note tendons which attach muscles to the skeleton Muscles Contract in Response to Acetylcholine (Ach) Cholinergic Motor neurons make these connections Neuromuscular junction M o to r unit Muscles themselves are made of fibers Each fiber contracts in response to Ach induced depolarization Ca2+ enters & triggers formation of cross bridges between actin & myosin Z band: Ends of myofibril subunits Muscles also have sensory transducers imbedded in them Stretch receptors (also called spindles) have a firing rate that indicates muscle length Spinal Reflex Circuit The Stretch Reflex Circuit Another View of the Stretch Reflex Note that some other system sets the initial position of the limb A pool of motor neurons In the spinal cord Serves each muscle These pools form a Topographic map (sort of) Pyramidal motor system Betz Cell (a type of pyramidal neuron) Corticospinal Tract Corticobulbar Tract Extrapyramidal motor system That is......axons do not project thru the medullary pyramids Basal Ganglia Disease Wilson's Disease: Muscular rigidity, tremor, weakness & liver dysfunction due to problems with copper metabolism. GP & striatum affected. Huntington's Disease: Choreiform movements due to loss of neurons within the striatum. Parkinson's Disease: Muscular rigidity, tremor, weakness, etc due to death of of dopamine neurons in substantia nigra. Huntington's Disease Video Parkinson's Disease Parkinson's Disease Stooped posture Tremor Pill-rolling Bradykinesia Shuffle feet Parkinson's Disease: Micrographia Parkinson's Disease Video Cerebellar Function Controls muscle tone to hold posture Monitors positions of body parts and compares with the desired position Adjusts activity of motor cortex and spinal cord to smooth motions Important for the rapid, consecutive, and simultaneous movements Cognitive tasks: attention, emotion, language, motor Sagittal plane Corrective feedback Motor areas of cerebral cortex Thalamus Cortex of cerebellum 4 3 2 1 Motor centers in brainstem Pons Pontine nuclei Direct pathways Sensory signals from proprioceptors in muscles and joints, vestibular apparatus, and eyes Indirect pathways Signals to lower motor neurons Sagittal section through brain and spinal cord Cerebellar Lesion Effects Long Onset Latency Dysmetria Tracking Failures http://www.youtube.com/watch?v=5eBwn22Bnio&feature=related Multiple Motor System Exam 2 is on Feb 24th Questions? ...
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