PAIN

WHAT IS PAIN?

• Sensation or discomfort
• Stimulation of nerve endings
• Travels from PNS to CNS

REACTION & THRESHOLD

• How a person reacts to the pain
• Differs from person to person
• Can vary from day to day

WHAT AFFECTS PAIN

• Anatomy of area
• Pain threshold
• Age
• Nationality
• Gender

THE NERVE

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NERVE FIBERS

• Myelinated- rapid conduction
• Unmylenated- slow conduction
• Determines the speed of impulse
• Determines the type of pain perceived

RESTING STATE

• Na+ on the outside
• K+ on the inside
• More negative on inside
• Maintained by permeability (Na+ can't get in)
• Maintained by sodium-potassium pump

EXCITED STATE

• Na+ enters the cell
• K+ exits the cells
• Permeability changes

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KEY POINTS

• Depolarization- ionic concentrations are reversing
• Repolarization- polarity is returned (Na+ on outside)
• Action potential- rapid changes in membrane potential
• Absolute refractory period- membrane can't rexcite
• Relative refractory period- greater stimulus needed to excite