2. Neurons

3. Neurons are highly specialized cells. A neuron has four parts. 1. cell body has nucleus and organelles 1 Cell body 2. dendrites receive impulses as signals (message) 2 dendrites 3. axon carries impulses as signals 3 axon 4 4. terminal converts electrical impulses to chem. signals terminal

4. Resting Potential Defined: Neuron at rest Neuron Exterior: – Positive charge – Mainly Na + outside the cell Neuron Interior: – Negative charge – K + inside the cell

5. Action Potentional Defined: a moving electrical impulse. –generated by a stimulus. –Na + enters, and cell becomes + charged. –K + leaves, and area of + charge moves.

6. imp ulse

7. Na + K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ negative impulse K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+ K+K+

9. Synapse Defined: Gap between neurons Problem: Impulse cannot cross the gap Solution: Impulse converted into chemical molecules that stimulate the next cell, called neurotransmitters Steps: – Impulse reaches neuron’s end – Vesicle releases neurotransmitters – Neurotransmitters attach to neighboring neuron – New impulse created

11. impul se Impulse stimulates a vesicle, which contains neurotransmitters Vesicle exits the cell and dissolves End of one cell Start of another cell

12. imp ulse Neurotransmitters cross the synapse and attach to receptors of a neighboring neuron Neurotransmitters stimulate a new impulse End of one cell Start of another cell

13. Feet Brain ….

14. Impulse causes the muscles to stretch and contract…this causes MOVEMENT! Motor neurons reach the muscles