1. Sodium-Potassium Pump 1. A form of Active transport 2. ATP (energy) is needed because the flow of ions goes against the natural concentration gradient (high to low). 3. Ions move from areas of low concentration to high concentration. 4. Sodium ions are pumped into a cell across the plasma membrane, while potassium ions are pumped out of the cell. 5. 3 Na + go in, 2 K + come out creating an action potential (re-polarizes the membrane)

3. Action Potential 1. If the action potential (nerve impulse) starts, it is propagated over the entire axon 2. The sodium-potassium pump restores the original configuration of the nerve cell (negative). 3. The impulse continues to move toward the cell body 4. Impulses travel faster when fibers have a myelin sheath 5. Refractory period – nerve re-polarizes and can not react

5. Neurotransmitters 1. More than 25 different kinds have been identified 2. Acetylcholine (Ach), dopamine, seratonin, and norepinephrine (NE) are the most well known ones 3. Drugs are available for people with imbalances/ diseases that enhance or block their transmission. 4. Can be inhibitory or excitatory

6. Sensory Neurons Motor Neurons 1. Carry impulses from the sensory receptors 2. Sensory receptors include the cutaneous (skin) sense organs and proprioreceptors (detect stretch, tension, balance) 3. Unipolar 1. Information carried from the CNS 2. Innervate muscles and glands 3. Multipolar Functional Classification of Neurons

7. Interneurons 1. Known as association neurons 2. Lie between sensory neurons and motor neurons 3. Carry messages from one side of the brain or spinal cord to the other 4. Multipolar

8. Neuron Classification

9. Structural Classification of Neurons Bipolar Neurons- one axon and one dendrite Unipolar Neurons- have a short single process leaving the cell body

10. Multipolar neurons- many dendrites leaving the cell body and a single axon

11. Physiological Terms 1. Irritability- ability to respond to a stimuli 2. Conductivity- ability to transmit an impulse 3. Polarization- the inside of cells have fewer positive ions than outside the cell; the condition of the plasma membrane at rest

12. The Reflex Arc 1. A reflex is defined as a rapid, predictable, and involuntary responses to stimuli 2. Reflex arc – direct route from a sensory neuron, to an interneuron, to a motor neuron

13. Simple Reflex Arc

14. Types of Reflexes 1. Autonomic Reflexes include: a. Smooth muscle regulation b. Heart and blood pressure regulation c. Regulation of glands d. Digestive system regulation 2. Somatic Reflexes- reflexes involving the activation of skeletal muscles