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Central Nervous System “CNS” Brain and spinal cord- integrates, processes, and coordinates sensory information and motor commands Peripheral Nervous Sys. “PNS” All neural tissue outside of the CNS Cranial Nerves= Nerves connected to the brain Spinal Nerves= nerves connected to the spinal cord Afferent (sensory)- bring sensory info to CNS from receptors Efferent (motor)- carries motor commands from the PNS to muscles and glands PNS Divisions Somatic N.S.- controls skeletal muscle contractions (both voluntary and involuntary) Autonomic N.S.- automatic regulation of smooth muscle, cardiac muscle, and glandular secretions Neurons Cell body- contains nucleus, bundles of neurofibrils that extend from cell body to form dentrites, cytoplasm contains perikaryon – Organelles that synthesize neurotransmitters – Ribosomes, RER, stain darkly “nissl bodies”, account for gray color of ares containing gray matter – CNS neurons can’t divide!Stem cells are found in the nose and the hippocampus Neuron Structure continued Dendrite- sensitive process that receives info from other neurons Axon- passes electrical impulses (action potential) and ends with synaptic terminals Synapse- area where 2 nerves meet, neurotransmitters are used for communication Neuroglia “glial cells” of CNS Supporting tissue for neurons – Ependymal cells- specialized epithelial tissue that lines the ventricles in the brain, and they help to monitor Cerebrospinal fluid – Astrocytes- largest and most numerous, maintain the blood brain barrier, provide a structural framework for neurons, repair damaged tissue, guiding neuron development, control interstitial fluid Glial cells of CNS cont. Oligodendrocytes- form myelin sheath around axon allowing increase action potential speed, regions w/ a lot of myelinated neurons is called white matter Microglia- small cells that can migrate to clear cellular debris, waste products, etc. Neuroglia of the PNS Neuron cell bodies are clustered together in the PNS= ganglia Satellite cells- surround neuron cell bodies, regulate environment Schwann cells- form a sheath around every axon, can myelinate axons Neural Physiology “how neurons make electricity” Beginning in the brain/or at a sensory receptor, a though or stimulus is applied Na+ rushes into receptor=depolarization – There must be enough Na+ to cause this to happen and that is determined by the strenght of the stimulus or the number of receptors stimulated (a little K+ leaks out) This is an action potential, and electricity is created Neurophysiology The electricity at this point causes the next section at the node Na+ gate to open, and more Na+ rushes into the next section and this causes electricity to jump from section to section – Propogation of nerve impulse – While electricity moves onward, the section of neuron behind it gets repolarized At the end of axon, the Ca+ gates open, this causes a rush of Ca+ which makes the vacuoles contain neurotransmitters to fuse w/ the synaptic knob and open Neurophysiology The neurotransmitter enters the synapse, which cause the Na+ gates to open in the next neuron or effector Repolarization- ATP powers Na+ and K+ pump to reestablish resting potential Nerves can’t be stimulated during repolarization unless a huge stimulus occurs, “you stick your wet finger into an electrical outlet Ready to fire again in .001 sec Chemical Synapses Excitatory neurotransmitters- cause depolarization and promote action potential Inhibitory Neurotransmitters- cause hyperpolarization, and suppress action potential Acetylcholine (Ach)- neuromuscular junction stimulates muscle contraction Other Neurotransmitters Norepinephrine (NE)- widely distributed in the brain, usually has an excitatory response Dopamine- CNS neurotransmitter, has both an excitatory and inhibitory effect – Not enough leads to overstimulation of neurons that control skeletal muscle leading to rigidity “Parkinson’s Disease” Seratonin- CNS, inadequate amount effects attention, emotions, and may be responsible for depression