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The Nervous System

The Nervous System. 2 categories in nervous system. Central nervous system (CNS) – brain, spinal cord Peripheral nervous system (PNS) – nerves outside CNS. 2 divisions of PNS – somatic (voluntary), autonomic (involuntary). http://lumen.georgetown.edu/faculty/che3/bvl/images/nervous.jpg.

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The Nervous System

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  1. The Nervous System

  2. 2 categories in nervous system. • Central nervous system (CNS) – brain, spinal cord • Peripheral nervous system (PNS) – nerves outside CNS. • 2 divisions of PNS – somatic (voluntary), autonomic (involuntary)

  3. http://lumen.georgetown.edu/faculty/che3/bvl/images/nervous.jpghttp://lumen.georgetown.edu/faculty/che3/bvl/images/nervous.jpg

  4. Autonomic divided into 2: 1sympathetic (during stress), 2parasympathetic (normal functioning)

  5. http://www.drstandley.com/images/nervous5.bmp

  6. Nerve Tissue • 2 types of cells: 1neurons (responsive cells that conduct impulses at fast speeds) 2neuroglia (support, maintain neurons)

  7. http://www.greenspine.ca/media/neurons_and_glial_cells.jpg

  8. 5 types of neuroglia • 1astrocytes (anchor neurons) • 2ependymal (form cerebrospinal fluid) • 3microglia (eat invading microorganisms) • 4oligodendrocytes (provide insulation around CNS – myelin) • 5Schwann cells (insulation around PNS)

  9. http://www.nrc-cnrc.gc.ca/education/images/bio/gallery/pl_astrocytes.jpghttp://www.nrc-cnrc.gc.ca/education/images/bio/gallery/pl_astrocytes.jpg

  10. Neuron made up of… • 1cell body (cytoplasm, nucleus, organelles) • 2dendrites (branching extensions from cell body – receive impulses) • 3axons (conducts impulse away from body)

  11. http://pami.uwaterloo.ca/~gsdharwa/b_c_i/neuron.gif

  12. Axons enclosed with Schwann cells forming layers rich in fat. • Provides insulation – myelin. • Insulation not continuous (gaps – nodes of Ranvier)

  13. http://www.sirinet.net/~jgjohnso/neuronsandsynapsel.gif

  14. Gray matter is made of unmyelinated fibers – shorter with no myelin • White matter is made of myelinated fibers – can be longer and have myelin

  15. http://cache.eb.com/eb/image?id=54745&rendTypeId=4

  16. Types of Neurons • Structurally, 3 different types. • 1Multipolar – many dendrites – carry impulses to skeletal muscle. • 2Bipolar – single dendrite, single axon – special sensory areas (ears, eyes) • 3Unipolar – one nerve fiber (from skin to spinal cord)

  17. http://homepage.psy.utexas.edu/homepage/class/Psy332/Salinas/Cells/multipolar.gifhttp://homepage.psy.utexas.edu/homepage/class/Psy332/Salinas/Cells/multipolar.gif

  18. Functionally, 3 different types of neurons. • 1Sensory (afferent) – carry from body to CNS) • 2Association (interneurons) – links between neurons • 3Motor (efferent) – from CNS to body

  19. http://www.nsbri.org/HumanPhysSpace/focus7/f7-290.jpg

  20. Impulse Transmission • Difference in voltage across cell membranes. • Openings in membrane are called ion channels. They regulate movement of ions. • Greatest influence – Na+, K+

  21. http://www2.montana.edu/cftr/images/IonChannel2.gif

  22. Sodium-potassium pump – transports sodium out of cell, potassium inside. • Causes concentration gradient – ions actively move across cell membrane through ion channels • Every 3 Na+ pumped out, 2 K+ back in.

  23. Outside of the membrane accumulates positive ions (potassium leaks out faster) • Resting membrane potential – no impulses are transmitted

  24. Potential on inside -70 mV. • Change in membrane permeability to sodium – ions flow outward; inside becomes more positive – depolarization (+ 30 mV) • Restored to normal – repolarization – potassium inward through ion channels, sodium channels close.

  25. Depolarization followed by repolarization – impulse sent down axon. • Nerve impulse – wave of ion reversals (changing charge of membrane)

  26. http://scienceblogs.com/clock/upload/2006/06/ActionPotential.jpghttp://scienceblogs.com/clock/upload/2006/06/ActionPotential.jpg

  27. Myelinated fibers- Conduct impulses faster than nonmyelinated fibers • Node of Ranvier – gaps in axon of myelinated fibers • Impulse jumps across myelin sheath from node to node – fastest conduction in body.

  28. http://www.getbodysmart.com/ap/nervoussystem/celltypes/menu/image.gifhttp://www.getbodysmart.com/ap/nervoussystem/celltypes/menu/image.gif

  29. Types of Stimuli • All-or-none – either impulse conducted or not. • Threshold – minimum strength of stimulus needed for action potential. • Subthreshold – no action potential. • Series of subthreshold – summation (lead to action potential)

  30. http://www.octc.kctcs.edu/gcaplan/anat/images/Image370.gif

  31. Gap between adjacent neurons - Synapse • Neuron that sends impulse – presynaptic neuron; recieves impulse – postsynaptic neruon • Axon of presynaptic – bulb with synaptic vescicles (contains neurotransmitters)

  32. Synaptic Cleft – Small space between the terminal end of an axon and the next neuron or muscle.

  33. http://www.colorado.edu/intphys/Class/IPHY3430-200/image/figure7m.jpghttp://www.colorado.edu/intphys/Class/IPHY3430-200/image/figure7m.jpg

  34. 2 effects of neurotransmitters • 1Excitatory – increase membrane permeability to sodium ions (cause action potential) – accetylcholine, norepinephrine • 2Inhibitory – lowers chance of impulse crossing synapse – endorphins, GABA (inhibit pain)

  35. http://www.ainenn.org/images/bio-sinapse.PNG

  36. Central Nervous System • 1Spinal cord – from base of brain to 1st, 2nd lumbar vertebrae. • Enters through foramen magnum of skull. • Protected by vertebral column, fluid, and meninges (layers of membrane)

  37. Direction of Impulses • Ascending tract (up towards brain)– sensory information • Descending tract (away from brain)– motor information • Spinal cord also serves for reflexes – rapid response to emergency.

  38. Reflex arc • Reflex arc- Receptor (generates action potential) sends message along sensory neuron to CNS (spinal cord). • Examples: Withdrawal reflex, patellar reflex, vomiting- smooth muscle reflex, heart rate- cardiac muscle reflex

  39. http://webanatomy.net/anatomy/reflex_arc.jpg

  40. The Brain • 3 major regions: 1forebrain, 2midbrain, 3hindbrain. • Forebrain – cerebrum, diencephalon • Midbrain – below diencephalon • Hindbrain – pons, medulla oblongata, cerebellum. • Brain stem – midbrain, pons, medulla

  41. http://www.dhushara.com/book/brainp/brainil/brain.jpg

  42. Cerebrum • Cerebrum – higher brain – conscious thought, memory, learning. • Divided into left and right cerebral hemispheres. • Wrinkled structure (convolutions) – result from rapid growth during development.

  43. http://www.web-books.com/eLibrary/Medicine/Physiology/Nervous/cerebrum_lobes.jpghttp://www.web-books.com/eLibrary/Medicine/Physiology/Nervous/cerebrum_lobes.jpg

  44. Foldings project upward – gyri; downward – sulci. • Deep grove – fissure; 2 major ones – longitudinal (divides hemispheres), transverse (cerebrum from cerebellum)

  45. http://cas.bellarmine.edu/tietjen/HumanBioogy/giri_and_sulci.gifhttp://cas.bellarmine.edu/tietjen/HumanBioogy/giri_and_sulci.gif

  46. Peripheral Nervous System • Nerves, ganglia, sensory receptors. • Communication between CNS and other areas of body. • Nerve – composed of more than 1 type of tissue; responsible for transporting nerve impulses.

  47. http://www.nrc-cnrc.gc.ca/education/images/bio/gallery/pl_nerve.jpghttp://www.nrc-cnrc.gc.ca/education/images/bio/gallery/pl_nerve.jpg

  48. Nerves with… • sensory fibers – afferent nerves • motor fibers – efferent nerves • both – mixed nerves • Ganglia – clusters of neurons outside CNS

  49. http://content.answers.com/main/content/wp/en/f/f0/ReflexArc1.jpghttp://content.answers.com/main/content/wp/en/f/f0/ReflexArc1.jpg

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