1. Nervous System

2. What are the functions of the nervous system? It receives information about what is happening both internal and external stimuli. It directs the way in which your body responds to this information. It helps maintains homeostasis.

3. What are neurons? The cells that carry information through your nervous system. The message that a neuron carries is called nerve impulses.

4. Structure of a neuron Cell body (nucleus) - contains the nucleus and other cell organelles. Most of the metabolic activity of the cell takes place in the cell body.

5. Structure of a neuron Dendrite – carries impulses from the environment or other neurons toward the cell body. Short branches extension of the cell body.

6. Structure of a neuron Axon - the long fiber that carries impulses away from the cell body. The axon ends in a series of small swellings called axon terminals

7. Structure of a neuron Myelin sheath – an insulating membrane that covers the axon. The nodes increases the speed at which the impulse can travel.

8. Three kinds of neurons Sensory neuron – picks up stimuli from the internal or external environment and converts each stimulus into a nerve impulse.

9. Three kinds of neurons Interneuron – a neuron that carries nerve impulses from one neuron to another. Motor neuron – sends an impulse to a muscle, and the muscle contracts in response.

11. What is a nerve impulse? A nerve impulse travels along a neuron in the form of electrical and chemical signals. It can travel as fast as 120 meters per second!

12. Resting neuron When a neuron is resting (not transmitting an impulse), the outside of the cell has a net positive charge, and the inside of the cell has a net negative charge – resting potential.

13. Sodium-potassium pump

14. Action potential When a neuron is stimulated, positive ions (Sodium ions) rush into the cell. The area inside the cell becomes temporarily more positive than the outside. This reversal of charges is called action potential. As the impulse passes, gates within the potassium channels open, allowing K + ions to flow out - this restores the resting potential

15. Action Potential

16. What is a threshold? Definition: the minimum level of a stimulus that is required to activate a neuron. Any stimulus that is stronger than the threshold will produce an impulse; any stimulus that is weaker than the threshold will produce no impulse. A nerve impulse follows the all-or-none principle: either the stimulus will produce an impulse, or it will not produce an impulse.

17. Synapse The location at which a neuron can transfer an impulse to another cell is called a synapse.

18. Synapse The synaptic cleft, separates the axon terminal from the dendrites of the adjacent cell. Neurotransmitters are chemicals used by a neuron to transmit an impulse across a synapse to another cell.

19. How a neuron transmits a signal? A neuron is stimulated when exceeding it’s threshold – a new impulse begins. Sodium channels open, then action potential is generated. The impulse moves down the axon until it reaches the axon terminal. An impulse reaches the axon terminal, releasing neurotransmitters on the next neuron (synapse).