Nervous Circuits Reverend Dr David C.M. Taylor School of Medicine

 To use our understanding of the case to  Be able to distinguish between upper and lower motor neuron lesions  To gain an understanding of the spinal reflexes  To start to understand the control of movement Our objectives in this plenary

 Experienced one-sided weakness in her arm and face  In principle the problem could lie in the periphery (spinal motor neurones etc.,)  Or it could lie centrally (with the motor neurones or pathways that control the spinal motor neurones) Mrs Webster

 We need to distinguish between upper and lower motor neurones.  Upper motor neurones are in the motor cortex  Lower motor neurones are in the spinal cord - think about the knee jerk reflex So?

 The descending fibres cross in the medulla en route to the spinal cord Upper motor neurones This image of an homunculus has been removed to avoid breach of copyright

Pathway This image of descending motor pathways has been removed to avoid breaching copyright

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Knee jerk reflex stretch receptor in muscle contraction of muscle spinal motor neurone

Tap tendon just below patella stretch muscle activate receptors extensor contractsextensor  mn Renshaw cellinhibitory interneurones flexor relaxesflexor  mn Monosynaptic Reflex

Simple withdrawal reflex

More fully…

Full crossed extensor reflex

Simple scheme Plan Execute Cortical association areas MovementIdea Premotor and motor cortex

Overview of control Plan Execute Basal ganglia Cortical association areas Lateral cerebellum intermediate cerebellum MovementIdea Premotor and motor cortex