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Nervous System - Coggle Diagram
Nervous System
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Action Potential
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when its reached, cells respond by returning to resting potential -70mV by process of repolarization
At the end of repolarization a slight overshoot called hyperpolarization occurs in which potential dips below -70mV
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Finally the Na+/K+ pumps moves Na+ ions back out of cell, and K+ back into cell
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Cranial Nerves
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the first pair arises from the cerebrum and the second pair from the thalamus, but most arise from the brainstem
Spinal Nerves
31 pairs, all except the first pair are mixed nerves
each arises from two roots: a sensory dorsal root, and a motor ventral root
Each dorsal root and doral root unite to form a spinal nerve which extends out of the vertebral canal through the intervertebral foramen
Autonomic Nervous System
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Helps maintain homeostasis, responds to emotional stress, and prepares the body for strenuous activity
Controls heart rate, blood, pressure, breathing rate, body temperature
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General Functions
Sensory Function
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Information travels from receptors to sensory neurons, which transport information into the CNS
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Impulse Conduction
Refractory period: limits frequency of action potentials; ensures the impulse is only transmitted in one direction-down the axon
Continuous Conduction: occurs in unmyelinated axons; conduct impulses sequentially over the entire length of their membrane
Saltatory Conduction: occurs in myelinated axons; the mylein sheath insulates axons from ion movement across the cell membrane
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Tissues
Neurons
Sensory(afferent) neurons: conduct impulses from peripheral receptors to the CNS; usually unipolar, although some are bipolar
Interneurons(association or internuncial neurons):multipolar neurons lying within the CNS that form links between other neurons
Motor(efferent) neurons: multipolar neurons that conduct impulses from the CNS to peripheral effectors(muscle& glands)
Neuroglia
Astrocytes lie between blood vessels and neurons; functions: structural support; formation of blood-brain barrier, protecting brain tissue from chemical fluctuation and prevents entry of many substances
Peripheral nervous system: Schwann Cells: the myelin-producing neuroglia of the PNS; Satellite cells: provide protective coating around cell bodies of neurons in the PNS
Reflex Behavior
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Withdrawal Reflex
occurs in response to touching something painful, such as stepping on a tack
involves sensory neurons, interneurons, and motor neurons
Divisions
Sympathetic:Short preganglionic fibers in the sympathetic division arise from neurons in the gray matter in the thoracic and lumbar regions of the spinal cord
Parasympathetic: long preganglionic fibers in the parasympathetic division arise from the brainstem and sacral region of the spinal cord
Neurotransmitters:chemical messengers in a synapse, that convey an electrical impulse from a neuron to another cell