Nervous System Central Nervous System CNS The brain
Nervous System
Central Nervous System • CNS – The brain and spinal chord • Transmit information to the body
Peripheral Nervous System • Neurons that carry information in and out of the CNS
Neurons • • • Neurons – nerve cells that transmit info. Made of a cell body with a nucleus Dendrite – receives signals Axon – transmits signals Synapse – where and axon meets a dendrite. Glia – support cells, that nourish and insulate
Resting Potential • Resting Potential – ion gradient of (+) outside • (-) inside • Sodium and Potassium are moved in and out of the cell by sodium potassium pumps and ion channels. • Sodium is pumped out potassium in, but potassium is allowed to flow back out, creating a positive charge on the outside and a negative charge on the inside of the membrane. **
Action Potential • Action Potential – a stimulus reverses the charge of the membrane. ** • Gated ion channels open allowing sodium to flow in. This reverses the charge of the membrane. • In response, potassium channels open to let potassium out, thus restoring the charge. • Sodium potassium pumps restore the balance.
Conducting Action Potentials • The opening and closing of gated ion channels travels along the membrane of the axon • This causes a reversal of charge to travel down the membrane of the axon. • This is the electrical signal that nerves transmitt
Fast Conduction • Glia can wrap the axon in a layers of membrane insulation called a myelin sheath that acts like wire insulation • Schwann cells do this in the PNS, • oligodendrocytes do this in the CNS
Receiving action Potentials • Action potentials can be received electronically or chemically. • Electronically through another action potential like interaction • Chemically, through a synaptic vesicle releasing a neurotransmitter that flows through a synaptic cleft (synaptic signaling)** • Ex. Endorphins (decrease pain)
PNS organization • Afferent neurons receive information • Efferent neurons cause actions to happen.
Efferent control • Efferent neurons control the motor system and the autonomic system. • Motor system consist of acts you can control. (walking) • Autonomic system consist of acts that are involuntary. (breathing)
Autonomic System • Sympathetic – causes processes to become enhanced (breath faster, pump more blood) • Parasympathtic – causes processes to relax • Enteric division – control digestive activities.
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