The HumanNervousSystem

Neuron- A Nerve Cell

Cell bodyContains the nucleus and other

organellesDendrites

Receive stimuliConduct impulses toward the cell

bodyAxon

Carries impulses away from the cell body

Axon Structure

Myelin sheathInsulating coat of plasma

membranesSections of sheath are called

“Schwann Cells”Unmyelinated axons carry impulses

much slower than myelinated axons

Nodes of RanvierBare axonal membrane between

Schwann cells

The Synapse

Synapse The gap between nerve cells

NeurotransmitterChemicals that carry nerve signals across the synapse

Reflex Arc

The reflex arc responds to a stimulus without the immediate involvement of the brain

Central Nervous System(CNS)

• Brain• Spinal Cord

Cerebrum

Directs voluntary movementSensory processingLanguage and communicationLearning and memory

Cerebellum

Regulates sense of balanceCoordinates voluntary muscle movement

Medulla Oblongata

BreathingHeart rateBlood pressureSwallowing and digestion

Peripheral NervousSystem (in blue)

Peripheral Nervous System

• Sensory Division–Bring information to the

CNS

• Motor Division–Carries signals away from

the CNS• Somatic (voluntary) nervous

system controls skeletal muscle action• Autonomic nervous system

(involuntary) controls organ systems and smooth muscle

Divisions of the Autonomic Nervous

System• Sympathetic– Stress responses (Fight or

Flight)• Pupils dilate• Mouth dries up (saliva

decreases)• Heart rate increases• Blood flow to skeletal muscle

increases

• Parasympathetic– Relaxation response

• Heart rate slows• Pupils constrict• Stimulates salivation• Digestive processes

stimulated