1 Postural Control in Multiple Sclerosis: Stability and Complexity Analyses!The nervous system: fundamentals! University of Massachusetts Amherst Department of Kinesiology A B Questions • Why do we need neurons? • What is the structure of neurons? • What is the relation between neuronal form and function • How many neurons and connections does the CNS have? Chemical Diffusion An imaginary organism with sensory cells (S) that control motor cells (M) by releasing a chemical transmitter or hormone into the common fluid space.2 Diffusion time of a chemical signal Neuronal communication through axons and dendrites Figure 1.3 The major light and electron microscopical features of neurons (Part 1) Figure 1.2 Some nerve cell morphologies found in the human nervous system (Part 1)3 Figure 1.2 Some nerve cell morphologies found in the human nervous system (Part 2) Figure 1.6 Visualizing nerve cells and their connections Schematic of a neuron with myelinated axon. The myelin is seen interrupted at regular intervals, at the nodes of Ranvier. (The picture is not to scale – the distance between the nodes of Ranvier is typically of the order of 1 mm, while the cell body might be 20–80 mm in diameter) Cells of nervous system • How many neurons does the brain have? • 100 * 109 (100 billion!) • How many supporting cells? • 300*109 • How many connections? • 1-100,000 per neuron regulate errors,brain —> typing while talking corrective movements4 Figure 1.5 Varieties of neuroglial cells (Part 1) Chemical balance Recent: may have stem cell properties Myelin PNS: Schwann cells Injury: scavenger cells What happens in MS? Multiple Sclerosis Figure 1.7 A simple reflex circuit, the knee-jerk response (Part 1) Figure 1.9 Intracellularly recorded responses underlying the myotatic reflex (Part 2)5 • Think ‘big’ • Think Functionally not structurally Questions • Why do we need neurons • What is the structure of neurons? • What is the relation between neuronal form and function • How many neurons and connections does the CNS
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