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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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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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Simplest type of neural circuit
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regulates reflexes
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rapid involuntary response to stimuli
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integration occurs in spinal cord rather than brain
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Neurons Each Have
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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
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*Glial Cells
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not neurons, help provide and support nerve cells.
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1) Schwann Cells
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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
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ATP drives active transport
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3 Na+ pumped out - 2 K+ pumped in
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Membrane Potential
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V= V(inside) - V(outside)
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resting potential of neuron is -70mV
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Action Potential
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depolarization followed by reploarization.
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increase in membrane potential followed by a decrease
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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
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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