1. 35.2

2.  Controls and coordinates functions throughout the body.  Responds to external and internal messages.  The body’s  communication system

3. Specialized cells of the nervous system Transmit electrical signals called impulses in only one direction. 3 types – sensory neurons-send signals from sensory receptors  brain – motor neurons – send signals from the brain  muscles & glands – interneurons –carry impulses between sensory & motor neurons

4. Axon terminals Nodes Myelin sheath Cell body Axon Dendrites Nucleus

5. Axons – carry impulses away from the cell body Myelin sheath – an insulating membrane surrounding the axon Cell body – where the metabolic activity of the cell takes place Dendrites – carry impulses from the environment to the cell body

6. A nerve impulse is similar to the flow of electrical current through a wire. When the neuron is NOT sending an impulse, the inside is negative and the outside is positive Na+ and K+ ions move across the cell Membrane via the sodium-potassium pump

7. The Moving impulse  An impulse begins when a neuron is stimulated by another neuron or the environment  Action potential - When an impulse is sent the charge reverses inside the cell – it becomes positive  Threshold – the amount of stimulus required to activate the neuron

8. The moving impulse  An impulse begins when a neuron is stimulated strong enough to reach a threshold. The impulse travels rapidly down the axon towards the terminal end.

9. Where impulses are transferred from one neuron to another. Chemicals diffuse across a small gap between the cells Neurotransmitters- are the chemicals that transfer impulses from one neuron to another. Receptors of the neighboring neuron pick up the chemical message, and a new impulse begins. axon Neuro- transmitter Direction of impulse receptor Axon terminal vesicle Dendrite of Adjacent neuron

10. In a fraction of a second after binding to the receptors, the neur0transmitter molecules are released. They are re-absorbed back into the axon terminal

11. What are the 4 parts of a neuron? What is a threshold? How does a message move from one neuron to another? Review questions