Requirements of Motor Systems ● Sensory feedback from the involved muscles ● Continuously relayed to the cerebellum, basal ganglia, and sensory cortex ● Functioning neuromuscular junction that links nervous system activity with muscle contraction Movement Planning ● Premotor cortex generates a plan of movement ● Primary motor cortex is responsible for execution of a movement
Motor Systems ● Pyramidal motor system ● Originates in the motor cortex ● Provides control of delicate muscle movement ● Extrapyramidal system ● Originates in the basal ganglia ● Provides background for the more crude, supportive movement patterns
What Would You Call … ● A defect causing weakness in both arms? ● A weakness in the right arm and leg? ● Inability to move one leg? ● Inability to move both legs?
Neurons ● Lower motor neuron lesions or infections; peripheral nerve injury ● Neuromuscular junction disorders ● Muscle atrophy or dystrophy Ach Motor endplate ● Dendrites receive stimuli; goes down axon ● Schwann cells make myelin (“white matter”) (PNS); helps increase AP conduction speed ● Motor unit - motoneuron and all of the fibers it innervates What Can Go Wrong With the Motor Unit?
Synaptic Transmission ● What is happening at stages 1–3? ● What will result if you block stage 1? ● Stage 2? ● Stage 3?
Organization of the Spinal Cord ● Dorsal ● Afferent ● Sensory ● Ventral ● Efferent ● Motor
A Woman Developed Polyneuropathy … ● Her spinal nerves were damaged ● She lost the ability to tell where her body was positioned ● She has to look every time she takes a step, to tell where she is moving her feet to What parts of her spinal nerves were damaged? Dorsal or Ventral Nerves?
Disorders of Skeletal Muscle Groups ● Muscular atrophy ● If a normally innervated muscle is not used for long periods, the muscle cells shrink in diameter, lose much of their contractile protein, and weaken ● Muscular dystrophy ● Genetic disorders that produce progressive deterioration of skeletal muscles because of mixed muscle cell hypertrophy, atrophy, and necrosis
Alterations of Neuromuscular Function ● Drugs and agents can alter neuromuscular function by changing the release, inactivation, or receptor binding of acetylcholine ● Curare acts on the postjunctional membrane of the motor endplate to prevent the depolarizing effect of the neurotransmitter – blocks AchRs ● Used during many types of surgical procedures ● Clostridium botulinum blocks acetylcholine release and results in paralysis
Neuromuscular Junction Problems ● Decreased acetylcholine release ● Botulism, caused by Clostridium botulinum ● Decreased acetylcholine effects on muscle cell ● Curare ● Myasthenia gravis ● Decreased acetylcholinesterase activity; acetylcholine has a stronger effect on the muscle cell ● Organophosphates
Myasthenia Gravis ● Myasthenia Gravis is a disorder of transmission at the neuromuscular junction (NMJ) that affects communication
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- Spring '15
- Internal carotid artery, Anterior cerebral artery, Middle cerebral artery