Download Unit 2: Nervous System

Tuesday
2-23-2010
Unit 2 Notes:
Nervous System Basics
(1) Function
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Respond to stimuli
Process information
Communicate
Maintain homeostasis
• Basic Pathway:
Sensory Input  Integrate & Process  Motor
Output
(2) Structure
• Made of:
– Brain
– Spinal cord
– Neurons
– Junctions
• Has a complex organization (hierarchy) of
sensory and motor levels.
(3) Brain & Spine
• Brain divided into lobes
• Spinal cord = communication highway
• All nerves communicate through Spine
• Example: Paralysis
(4) Neuron
• Neuron = Nerve Cell
• Types: Multipolar + Unipolar
• Basic Structural Components:
– Dendrites (Incoming)
– Cell Body (Integrate + Process)
– Axon (Outgoing)
– Myelin Sheath (Insulation + Speed)
– Axon Terminal (Final Destination)
(5) Unipolar Neurons
• Use: Afferent Input (Sensory Input)
• Dendrites connected to sensory organ
• Message sent to cell body  Out Axon
• Message sent out of axon terminal
• FOCUS:
– Get message to CNS
– Let CNS process and decide
(NO need to have cell body right by dendrites)
(6) Multipolar Neurons
• Use: Efferent Output (Motor Output)
• Multi = Lots of extensions coming from cell body
• Cell body directly connected to dendrites
• Dendrites coming from CNS / Efferent path 
effected organ
• FOCUS:
– Organize messages by importance
– Make organs do things
(Important to have cell body right next to dendrites)
(7) Junctions
• Junction = Meeting of Neuron + Neuron or
Neuron + Organ
– A.K.A.  Synapse, Synaptic Cleft
• Nerve Impulse  Axon  Axon Terminal 
Release Neurotransmitter
– Neurotransmitter = Chemical Message
– Causes an effect
– Binds with cell membrane on other side
(8) Nervous System Organization
CENTRAL NERVOUS SYSTEM
PERIPHERAL NERVOUS SYSTEM
(SENSORY / AFFERENT INPUT)
BODY
(INITIAL STIMULUS
/ IMBALANCE)
PERIPHERAL NERVOUS SYSTEM
(MOTOR / EFFERENT OUTPUT)
AUTONOMIC
(INVOLUNTARY)
SYMPATHETIC
(FIGHT / FLIGHT)
SOMATIC
(VOLUNTARY)
PARASYMPATHETIC
(REST & DIGEST)
(9) Sensory Input
• Afferent Input (away
from body)
• Sends message from
body part  Brain
• Initial stimulus or
Imbalance
(10) Central Nervous System (CNS)
• INCLUDES: Brain & Spinal cord
• “Head Honcho”
– Notified of everything, Makes all decisions
(11) Peripheral Nervous System (PNS)
• “Middle Man” / Body Guard: Body—CNS
– Helps organize messages being sent to CNS
and to organs.
• 2 Divisions:
– Sensory/Afferent Input
– Motor/Efferent Output
(12) Motor / Efferent Output
• CNS  Effector Organ
– CNS makes decision
– CNS sends message to release chemical, or
move
– GOAL: Regain Balance / Do What You Want
• 2 Divisions:
– Autonomic Nervous System
– Somatic Nervous System
(13) Somatic Nervous System
• Voluntary Actions
• Skeletal Muscle
• (All other actions are
involuntary)
(14) Autonomic Nervous System
• Involuntary Actions
– Autonomic : Autopilot
– Processes occur naturally without thought
• 2 Subdivisions:
– Parasympathetic
Pathway
– Sympathetic
Pathway
(15) Parasympathetic Pathway
• (Involuntary)
• “Rest & Digest”
• Normal bodily functions:
– Digestion , Excretion
– Lens Contraction, Blinking
– Gas Exchange
– Sleep
(16) Sympathetic Pathway
• (Involuntary)
• “Fight or Flight”
• Bodily Functions during heightened excitement:
– Increased heart rate, respiration
– Increased sweating
– Increased blood flow