THE NERVOUS SYSTEM (Part 1)

1. THE NERVOUS SYSTEM(Part 1)

2. Central Nervous System • Communication and coordination system of the body • Set of intellect and reasoning • Consists of the brain, spinal cord, and nerves

3. Neurons (Nerve Cell) • Transmits a message from one cell to another • Has a nucleus, cytoplasm, and cell membrane

4. Parts of a Neuron • Dendrites • Axon • Neurilemma (myelin sheath)

5. Dendrites • Carries the impulse to the cell body • May be one or many

6. AXON • Axon carries impulses away from cell body • Only one axon on each neuron

7. Neurilemma (Myelin Sheath) • Covering that speeds up the nerve impulse along the axon • Myelin is a fatty substance that protects the axon • Myelin is called white matter

8. Afferent (Sensory) neurons emerge from the skin or sense organs and carry messages from all parts of the body to the brain and spinal cord Efferent (Motor) neurons carry messages from the brain and spinal cord to muscles and glands Types of Neurons

10. Types of Neurons (continued) • Interneurons (Associative) - carry impulses from sensory neurons to motor neurons • Synapse – space between neurons, messages go from one cell to the next

11. Nerve Impulse • Stimulus creates an impulse • Impulse travels into the neuron on the dendrite and out on the axon • At the end of the axon a NEUROTRANSMITTER is released • Neurotransmitter carries the impulse across the synapse to the next dendrite

12. Nerve Impulse

13. Divisions of the Nervous System • Central Nervous System (CNS) – consists of brain and spinal cord • Peripheral Nervous System (PNS) – cranial and spinal nerves

14. Divisions of Nervous System (continued) Autonomic Nervous System • includes peripheral nerves and ganglia, • Supplies heart muscle, smooth muscle and secretory glands • Controls involuntary body functions

15. The Brain • 3 pounds mass of soft nervous tissue • 100 billion neurons • Composed of white and gray matter • Adequate blood supply is needed, brain tissue will die in 4-8 minutes without oxygen

16. Coverings of the Brain • Protected by the skull, cerebrospinal fluid, and three membranes called meninges. • DURA MATER – outer brain covering, lines the inside of the skull, tough dense fibrous connective tissue

17. Coverings of the Brain (continued) • ARACHNOID – middle layer of meninges that resembles fine cobweb. • PIA MATER – covers the brain’s surface, comprised of blood vessels held together by connective tissue “The meninges PAD the brain” Pia; Arachnoid; Dura

18. Cerebrospinal Fluid • Space between arachnoid and pia mater is filled with CEREBROSPINAL FLUID (CSF) • Acts as a liquid shock absorber and source of nutrients for the brain • Is a clear, colorless fluid

19. Ventricles of the Brain • Brain has 4 cavities filled with CSF called CEREBRAL VENTRICLES 1. Have right and left lateral ventricle 2. Third ventricle – behind and below the lateral ventricle 3. Fourth ventricle is below the 3rd, in front of the cerebellum and behind the pons and medulla oblongata.

20. Ventricle of the Brain (continued) • CSF is produced by a structure called the CHOROID PLEXUS. • Choroid Plexus is a network of blood vessels lining the ventricles which helps in the formation of CSF

21. Blood-Brain Barrier (BBB) • Choroid plexus capillaries prevent substances (like drugs) from penetrating brain tissues • Makes infections, like meningitis, difficult to cure

22. Blood Brain Barrier (continued) • BBB can be broken down by: • Hypertension • Not fully formed at birth • Exposures to microwaves • Radiaton • Infections • Trauma, Ischemia, Inflammation

23. Lumbar Puncture • AKA Spinal Tap is a diagnostic test for examination of CSF • Removal of 5 to 20 ml of CSF from spinal canal • Needle puncture is between the 3rd and 4th lumbar vertebrae

24. To Be Continued