The Nervous System

1. The Nervous System

2. Two Main Parts • The Central Nervous System • Consists of the Brain and Spinal Cord • The Peripheral Nervous System • Nerve cells that send messages between the central nervous system and the rest of the body

3. Neurons • Nerve cells, called neurons, run through our entire bodies. • Neurons send and receive messages • Each of us has over 100 billion neurons • Most of our neurons are found in the brain

4. Components of a Neuron • Think of Neurons like trees • Including Branches, Trunk, and Roots • Neurons can lay alongside each other like two trees in a forest • Unlike trees neurons can lay end to end as well, i.e. the “roots” are intertwined with the branches.

5. Components of a Neuron

6. Components again…. • Cell Body: Produces energy that fuels the activity of the cell. • Dendrites:“The Branches” receives information from other neurons and passes the message through the cell body.

7. Components are FUN!! • Axon: “Trunk” carries information away from the cell body. • Myelin: A fatty white substance that insulates the axon and speeds the communication. • Axon Terminal: “Roots” End of the axon; send messages to another neurons dendrites.

8. How they Communicate

9. How they Communicate • Synapse: Junction between the axon terminals of one neuron and the dendrites of another. • Messages can only travel in one direction.

10. Neurotransmitters • Neurotransmitters: Chemical stored in sacs within the axon terminal. • Neurons communicate by sending different neurotransmitters between cells.

11. Spinal Cord • Column of nerves about as thick as a thumb. • Spinal Reflexes: automatic response Exp: touching a hot stove.

12. Somatic Nervous System • Transmits sensory messages to the central nervous system. • Activated by touch • Exp: Change in temperature, but also includes changes in body position i.e. posture and balance

13. Autonomic Nervous System • Regulates the bodies vital functions • Includes things like heartbeat, breathing, digestion, and blood pressure. • There are two divisions of Autonomic functions.

14. Sympathetic System • Known as the “Fight or Flight” response. • Prepares the body to either confront a situation or run away. • Exp: Attacked by a mugger

15. Parasympathetic Nervous System • Normalizes the body after a stressful event. • Brings down heart rate, blood pressure, and breathing. • Sympathetic=Stress Parasympathetic=Peace