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Nervous System
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How It Works Sensory input - detection of stimulus
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Integration - processing in the brain
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Motor Output - response in other body part
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Central Nervous System brain and spinal cord
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Peripheral Nervous System Afferent System (sensory) - receives input from body receptors and transmits signals to CNS
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Efferent System (motor) - carries signal from CNS to body
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Efferent (Motor) Division
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Somatic System responds to external and internal stimuli by sending signals to skeletal muscles (voluntary)
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Autonomic System involuntary. signals to smooth muscle, cardiac, and organs
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1) Sympathetic Nervous System - prepares body for stress, affected by epinephrine
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2) Parasympathetic Nervous System - restores body back to normal
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Reflex Arc
Simplest type of neural circuit |
regulates reflexes |
rapid involuntary response to stimuli |
integration occurs in spinal cord rather than brain |
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Neve Signals
Neurons Each Have |
enlarged cell body, axon, dendrites |
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body- nucleus and organelles |
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axon- conducts signals from one neutron to next |
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dendrites- receives signals and sends to cell body |
*Glial Cells |
not neurons, help provide and support nerve cells. |
1) Schwann Cells |
wrap around axon of a neuron to provide insulation (high lipid content) |
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form myelin sheath |
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gaps between them are called Node of Ranvier |
Na+ / K+ Pump
ATP drives active transport |
3 Na+ pumped out - 2 K+ pumped in |
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Membrane Potential |
V= V(inside) - V(outside) |
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resting potential of neuron is -70mV |
Action Potential |
depolarization followed by reploarization. |
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increase in membrane potential followed by a decrease |
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Phases
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Phase 1: RESTING STATE before neuron receives stimulus (-70mv)
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Na+ channels closed
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K+ channels closed
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Phase 2: THRESHOLD depolrization stimulus opens Na+ channels
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reaches threshold (-50mV)
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Phase 3: DEPOLARIZATION depolarization opens all Na+ channels, positive feedback
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Phase 4: REPOLARIZING after peak action potential (+30mV)
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K+ channels begin to open (flow of K+ depolarizes cell)
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Na+ channels begin to close
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Phase 5: UNDERSHOOT K+ channels close very slowly (-80+)
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Synapse
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Synapse cell junction that controls communication between neuron and other body cells
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Electrical Synapse rapid transmission. Current from presynaptic cell flows through postsynaptic cell
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channels between adjacent cells
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Chemical Synapse synaptic cleft - gap separating cells
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synaptic vesicles - sacs at synaptic terminal containing neurotransmitters
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presynaptic membrane depolarized. Ca2+ channels open. Stimulates exocytosis of synaptic vesicle
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Neurotransmitters excitation or inhibition effect
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Acetylcholine - triggers muscle contractions, hormones, wakefulness, memory. Most common
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Endorphins - released during pleasure or stress
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