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Structure of the nervous system • @ Macroscopic level – Brain & nerves • @ Microscopic level – Neurons & Glial Cells Macroscopic: Divisions of the Nervous System Central (inside skull & spine) Brain Spinal Cord Peripheral (outside skull & spine) Nerves Central Nervous System Brain Divisions of the human brain Specialization of function Different regions of the brain are associated with different function Ouch! That hurts, dude! Spinal Cord Reflex Spinal cord lesion - Would sensation be abolished by: - a spinal cord lesion? - polio? - Would the reflex be abolished by: - a spinal cord lesion? - polio? Peripheral Nervous System Somatic System: - controls voluntary muscle Autonomic System: - controls glands & internal organs - has two subcomponents - Sympathetic (adrenaline): arousal - Parasympathetic: calm Figure 3.28 The Autonomic Nervous System Levels of Investigation Brain Areas (visual system) Cells (neurons) Molecules (neurotransmitters) Microscopic level: Neurons Neurons: Its many shapes & sizes 11 Neuron: basic parts Cell Body Dendrite Axon Axon Cell membrane Synaptic cleft football field Campus wide a street long as Philly - Ohio thick as pinky finger thick as thumb axon terminals # synapses 10.000 (same number as Villanova students) Some axons are wrapped burrito-style by fatty cells (glial cells) - increases speed at which neurons communicate) - white in color (white matter vs gray matter - is destroyed by multiple sclerosis Neuron: its physiology What makes neurons different from other cells? Neurons process and transmit electrical impulses Neuron’s cell membrane is electrically charged (interior is more negative) Neurons influence each other’s charge (‘communicate’) 13 How do neurons process and transmit electrical impulses? A. dendrites receive input from other neurons B. axon sends neural impulse to axon terminal C. a neurotransmitter (NT) is release and makes contact with another neuron (synapse) 14 Synapse Communication Steps • NT is released from pre-synaptic neuron • NT binds to receptors in post-synaptic neuron • Opens Na+ channels • Sodium rushes in (activation) • If enough Na+ rushes in => depolarization (action potential) • NT released by postsynaptic neuron Pre-synaptic neuron Post-synaptic neuron Other important facts Various Neurotransmitters (NT): - Dopamine Adrenaline Serotonin Acetylcholine For each NT,various receptors - nicotine & muscarine Drugs can act by - modifying amount of NT, or - binding to receptor (nicotine) The net effect on neuron could be: - activation (action potential) - inhibition Cells of the Nervous System Glia (Greek=glue) – Many types (oligodendrocites, schwann cells, astrocytes, and microglia) – More prevalent than neurons (10:1) Complexity of CNS • 1011 (100 billion) neurons • each neuron interacts with 1,000 -7000 others • => 100 -500 trillion connections (that’s a big #) • Many other factors: – Neurotransmitters – Receptors – Genes, Glial cells etc. Glial Cells • Functions: support, immunology (defense), nutrition for neurons, guide migration of neurons during development, maintain ion balance, etc. • Form myelin which helps the speed of the action potential. In Multiple Sclerosis, the myelin is broken down and axons become less efficient. Copyright © Allyn & Bacon 2004 Copyright © Allyn & Bacon 2004 Blood-brain barrier Basal ganglia lesion (hiperdensities) due to increased bilirubin in newborn (kernicterus) Movement disorder Spared images Figure 3.3 The Nervous System Figure 3.24 Spinal Column, Ventral View Vertebra of Spinal column Figure 3.26: Spinal Cord Cross Section Figure 3.25 The Spinal Cord