1. As a result of the coordinated structures and functions of organ systems, the internal environment of the human body remains relatively stable (Homeostatic) despite changes in the outside environment.

2. Nervous System Students know how the nervous system mediates communication between different parts of the body and the body’s interactions with the environment.

3. Neuron There are three types Sensory Interneurons Motor (effector)

4. Neuron

5. Neuron is name of the cell Cell body: nucleus, cell reactions Dendrites: carry impulses to cell body Axon: carry impulses away from cell body Axon terminals: at end of axon Myelin: 80% lipid insulate axon Node: gaps in the myelin where the impulse jumps across

6. Nerve A bundle of axons form a nerve

7. Reflex Involves all three neurons and the spinal cord

8. Transmitting electrochemical impulses Resting potential-not receiving or transmitting a signal Neuron is positive on the outside and negative on the inside (polarized) Outside has Na+ Inside has K+ and negatively charged proteins

9. Impulse An electrochemical change of the cell membrane 1. Stimulus causes the membrane to become permeable to Na+ 2. Na+ (sodium) ions rush into cell-depolarized 3. K+ (potassium) rush out of cell-repolarized This is called an action potential.

10. Refractory Period Period of time when neuron cannot send another signal because the Na + is on the inside and the K + is outside. Neuron must be back at the resting potential in order to send another impulse.

11. Sodium-potassium pump Reestablishes the concentrations of Na+ on the outside and K+ on the inside. This must occur to put the membrane back to resting potential.

12. Content Vocabulary Threshold—minimum level of a stimulus required to start an impulse Synapse—gap between neurons Neurotransmitter—chemical that stimulates another neuron