Two divisions of Peripheral NS:1. Afferent sensory pathways - involves thesensory organs like eyes, ears..Neurons carry action potentialfrom sense organs to CNSAlso called sensory division
Two divisions of Peripheral NS:1. Afferent2. EfferentMotor pathways - system thatinnervates muscles, effectororgans, and glands.Also called motor division
Action potential – electrical signal thattravels along a neuron.
Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS) transmits action potential from CNS to skeletal muscles conscious, voluntary control
Divisions of the Efferent Nervous System:1. Somatic Motor Nervous System (SMNS)2. Autonomic NS carries stimulus from theCNS to the smoothmuscles, cardiac muscles, andglandsInvoluntary, unconscious
Divisions of the autonomic system:1. Sympathetic system•prepares body for physical activity•increases heart rate, bloodpressure, blood glucose levels•Prepares for “flight or fight”
Divisions of the autonomic system:1. Sympathetic system2. Parasympathetic:Regulates resting and nutritionallyrelated functionsIncludesdigestion, urination, defecationSlows down heart, etc. after “Fightor Flight” response
NS at a Cellular level:2 types of cells: 1. Neurons = functioning cell
Three parts of neurons (nerve cells):A. cell body contains the nucleus of cellB. dendrites –short, branched extensions of cellbodyreceive nerve impulses and conductthem toward the cell body
Three parts of neurons (nerve cells):A. cell bodyB. dendritesC. axonone long extension which carriesimpulses away from cell body to othercellshillock where the cell body ends andaxon begins
Axon continued:Is wrapped in a substance calledmyelin produced by neuroglial cellsmyelin speeds up impulsedMyelin is called Schwann in PNSand oligodendrocyte in CNSGaps in myelin called nodes ofRanvier
Axon continued :Axons vary in lengthAxon splits into collateralaxons and then end inpresynaptic terminals
Nerve impulses travel from the dendrite to body to axon.Collateral Axons
Mature neurons cannot undergo mitosis.They are parenchymapermanent cells!! TAKE CARE of them!!
But, Mrs. Crawfordhow can I take care ofthem?Get plenty ofsleep, avoid lots ofTV, avoidcaffeine, alcohol, drug
Well, how manyneurons do I have?It is believed you havearound 100 billion,some will die just dueto natural causes(about 7,000/day)
NS at a Cellular level continuedCan classify neurons based on their structure - how many processes they have (dendrites and axons):
1.Unipolar –one process with a cell body that hangs off to the side2.Bipolar – two processes an axon and a single dendrite with the cell body in middle3. Multipolar –only one axon with many dentrites.