The Nervous System

1. The Nervous System Medical Biology Mission Hills High School

2. Functions of the Nervous System • Sensory • Integrative • Motor

3. Divisions of the Nervous System • The nervous system is divided into - Central Nervous System (CNS), containing the brain and spinal cord - The Peripheral Nervous System (PNS), containing the nerves and ganglia

4. The Peripheral Nervous Systemcontains… • cranial nerves which arise from the brain • Spinal nerves which arise from the spinal cord as well as many branches

5. Nerve Tissue • The nerve tissue is composed of two types of cells: -neurons, which conduct impulses, and… -neuroglia which support the neurons

6. Neurons • Structural and functional units of the nerve system • Perform sensory, integrative and motor functions -sensory: ability to sense (receive) information -Integrative: ability to process the information received and arrive at a desire to respond. -Motor: ability to initiate a response with body movement or secretion of a product.

7. Lots of types of neurons

8. Structure of neurons • Each contain a cell body with a nucleus • Numerous dendrites: receive and send information to the cell body • A single axon: moves impulse from dendrites and body to dendrites or body of other neurons.

10. 5 3 1 2 4

12. 1. Cell Body • Part of the neuron that contains the nucleus

13. 2. Nucleus • The nucleus is the control center of the cell and contains the genetic information in the form of DNA

14. 3. Dendrites • Dendrites carry impulses (from another cell’s axon tips) toward the cell body

15. 4. Axon • The axon carries impulses away from the cell body.

16. 5. Axon Tip(s) • The axon tips release chemicals that enable the impulse to cross the synapse Axon Tips

17. 6. Synapse • The space between the axon tip and the next dendrite. It is also called the synaptic cleft.

18. Label and tell the function of each neuron part

19. Myelin in PNS and CNS • Axons in large peripheral nerves contain a fatty, supportive sheath called myelin sheath • Presence of myelin makes nerve tissue appear white (white matter) • In CNS spinal cord, unmyelinated nerve tissue appear gray (grey matter)

20. What makes up the brain, the spinal cord or your peripheral nerves? • Neurons are “the cell” • Cell body • Nucleus • Axon • Dendrite • What do you think surrounds the cell? • What other organelles would be needed?

22. How are neurons connected? • Synapses!!

23. Why are neurons connected?

24. More neuron connections!

25. Close up look at your synapse (The Gray Matter) AXON What is this in the membrane? The synapse - where the action happens Transport protein The next cell’s plasma membrane

26. How does the Synapse carry the signal? 1. impulse travels down the axon (The White Matter) • Vesicles with neurotransmitters move toward the membrane • Neurotransmitters are released and diffuse toward the next cell’s plasma membrane 4. The chemicals open up the transport proteins and allow the signal to pass to the next cell

27. The synapse carries a signal from cell to cell 1 3 4 2

28. There are lots of proteins and chemicals in your body to do the work Why is it important that it is an electrical current?

29. How many synapses are in one neuron? 1,000 to 10,000!!

30. What do you think can change neurons and their connections? • Accidents • Drugs • Alcohol • Disease

31. Drugs and alcohol bind important receptors on neurons

32. Repeated binding causes the neuron to die

33. Drugs = neuron death

34. Alcohol damages dendrites - can repair after abstinence Alcohol blocks receptors and slows down transmission

35. 100 Billion or so neurons - what’s the problem with some of them dying? • Cells multiply all the time - will your neurons? • Does everyone react the same way to accidents, or drugs and alcohol? • Do all organisms react the same to all stimulus? • Which of your activities use your neurons?

36. What if neurons die here? or here or here or here or here