The Nervous System

1. The Nervous System

2. 1 Cell body Neurons are highly specialized cells. • A neuron has three parts. • cell body has nucleus and organelles

3. 2 dendrites Neurons are highly specialized cells. • A neuron has three parts. • cell body has nucleus and organelles • dendrites receive impulses as signals (message)

4. 3 axon Neurons are highly specialized cells. • A neuron has three parts. • cell body has nucleus and organelles • dendrites receive impulses as signals (message) • axon carries impulses as signals

5. Schwann cell, makes up myelin sheath, which insulates axons • Neurons have other structures to transmit signals.

6. synapse • Schwann cell, makes up myelin sheath, which insulates axons • Neurons have other structures to transmit signals. • Synapse, which is the gap between neuron and next cell

7. axon terminal • Schwann cell, makes up myelin sheath, which insulates axons • Neurons have other structures to transmit signals. • synapse, which is the gap between neuron and next cell • Terminal is where the signal leaves

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

9. It is generated by a stimulus. • Na+ enters, and cell becomes positively charged. • K+ leaves, and area of positive charge moves. • An action potential is a moving electrical impulse.

10. impulse

11. Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ K+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ K+ Na+ K+ K+ K+ K+ K+ K+ K+ K+ K+ K+ negative impulse K+ K+ K+ K+ K+ K+ K+ Na+ K+ Na+ K+ K+ K+ K+ K+ K+ Na+ K+ K+ K+ Na+ K+ K+ K+ K+ K+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ K+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+ Na+

13. 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

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

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

17. Brain …. …. …. …. Feet

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