The Nervous System

I.  Divisions

  1. Central Nervous System
  2. Consists of the brain and spinal cord
  3. Brain
  4. Protected by cranium
  5. Centers of thought
  6. Weighs about 3 lbs
  7. Constantly receives messages from senses
  8. Uses all this information to form ideas, decisions, and give commands to the body
  9. Communicates with most of the body through spinal cord
  10. 12 pairs of cranial nerves
  11. Branch directly off brain
  12. Eyes, ears, mouth, face, scalp
  13. Spinal cord
  14. thick bundle of nerves
  15. attaches to brain at brain stem
  16. spinal nerves pass through gaps in vertebrae
  17. 31 pairs of spinal nerves
  18. tapers off at upper portion of lumbar region
  19. 10 pairs of nerves pass through lumbar vertebrae and sacrum
  20. Meninges
  21. triple layer of protection on spinal cord and brain
  22. outer layer - dura mater
  23. one of strongest tissues in body
  24. flexible, protective layer
  25. middle layer – arachnoid
  26. thin fibers like spider’s web
  27. 3-D network around brain
  28. cerebrospinal fluid circulates in fibers and acts like cushion if you bump your head
  29. inner layer - pia mater
  30. delicate layer that lays against brain and cord
  31. 2 kinds of nerve cells
  32. glial cells - support and insulate the cell
  33. neurons
  34. actual cell
  35. very different from other cells
  36. Neurons
  37. long fibers that branch out
  38. cell body
  39. contains nucleus
  40. most of cytoplasm
  41. dendrites
  42. branching structure
  43. receives messages
  44. myelin sheath – fatty substance that surrounds and protects fibers
  45. axon
  46. long extension
  47. carries impulse away from cell body
  48. axon terminals
  49. hair like ends
  50. end of the axon
  51. myelin sheath
  52. protective layer
  53. formed around axon
  54. node of Ranvier
  55. gaps in the myelin sheath
  56. allow better transmission
  57. Schwann’s cells
  58. produce myelin
  59. located in myelin sheath
  60. types of neurons
  61. sensory - take information from body to brain
  62. motor - take message from brain to body
  63. interneurons
  64. only found in central nervous system
  65. relay information between neurons
  66. Gray matter
  67. largely cell bodies of neurons
  68. lack myelin (which is white)
  69. White matter
  70. mostly axons and glial cells (myelin coated)
  71. Nerve cell bodies found only in
  72. Brain
  73. spinal cord
  74. ganglion - mass of cell bodies
  75. large nerve mass called a plexus
  76. these plexus better control muscles (like in hands)
  77. automatic nervous system
  78. cranial and spinal nerves control body’s functions
  79. heart beat, breathing, digestion
  80. frees your mind to think on other things
  81. every organ and gland needs to be turned on or off at times - this control comes from hypothalamus of brain
  82. sympathetic - generally turns on system
  83. increases heart rate, breathing, blood supply
  84. for emergency situation or increases activity, stress
  85. parasympathetic - generally turns off syste
  86. slows it back down
  87. blocks action of sympathetic
  88. Stomach is opposite
  89. Peripheral Nervous System
  90. Cranial and Spinal nerves
  91. bundles of nerve fibers (axons)
  92. branch off from brain and spinal cord
  93. sciatic nerve
  94. longest nerve in body
  95. runs from base of spinal cord to leg
  96. 12 pairs cranial nerves
  97. 31 pairs spinal nerves - each pair supply body part
  98. most nerves carry both types of fibers – motor and sensory
  99. sensory carries from body to brain
  100. motor carries from brain to body
  101. cell bodies of sensory fibers located in ganglia outside spinal cord
  102. enter through rear nerve root
  103. cell bodies of motor fibers located in gray matter of spinal cord
  104. leave spinal cord through front root
  105. all impulses travel up and down through spinal cord

II.  How Nerves Work

  1. Function of Typical Nerve
  2. Sensory nerve fibers carry information
  3. up skin
  4. To spinal cord
  5. To brain
  6. Brain processes the information
  7. Temperature
  8. Pressure
  9. Pain
  10. Brain passes information
  11. Down spinal cord
  12. Through motor nerve fibers
  13. Tells muscle or body how to react
  14. Structure of nerve
  15. Nerve consists of bundles of nerve fibers
  16. Nerves are embedded in connective tissue
  17. In bundles lie nerve fibers (axons)
  18. imbedded among glial cells
  19. protected by myelin sheath
  20. each axon is either motor or sensory - never both
  21. Blood and lymph and cushioning of fatty tissue help to nourish and protect fibers
  22. Nerve Cells
  23. Majority of nerve tissue is glial cells
  24. Neurons are the only cells responsible for nerve impulse
  25. They do not reproduce - never replaced
  26. Alcohol and drugs kill cells that will never be replaced
  27. Dendrite pick up information
  28. Passes through cell body
  29. Information travels out through the axon
  30. they are surrounded by special glial cells called Schwann cells
  31. these produce myelin sheathing which acts as insulation on electrical wire
  32. there are gaps in the Schwann cells called nodes of Ranvier
  33. myelinated axons transmit impulses faster than those with no covering
  34. why does some have no covering?
  35. areas that allow exchanging of positive and negative charges to the nerve
  36. How neurons work
  37. Electrochemical process
  38. Nerve cell at rest - ion pumps give it a slightly negative charge
  39. Cell membrane has billions of voltage sensitive gates that transmit nerve impulses
  40. When one is opened by a signal (change in charge) causes a chain-reaction and they all open
  41. Electrochemical impulse races along nerve
  42. After impulse passed, cell goes back to original balance
  43. Synaptic Transmission
  44. Axons of sensory neurons and interneurons usually end in synapse
  45. enclosed junction between axon of one neuron and dendrites of another
  46. When impulse reaches synapse - special chemical is released known as neurotransmitter into synapse
  47. When sensors in receiving neuron detect the neurotransmitter it generates electric signal
  48. The message is passed along the neurons
  49. Peripheral nerves constantly relaying messages to and from the central nervous system
  50. In central nervous system things don’t automatically fire, they process the info and determine what to do
  51. Inhibitors of nerve impulses
  52. Local anesthetic - novacain - blocks nerve impulses
  53. Botulinum B toxin
  54. powerful poison
  55. most deadly type of food poisoning
  56. one of most toxic substances known to man
  57. destroys a protein inside motor nerve synapses preventing motor discharge - causing paralysis
  58. when it reaches muscles involved in breathing - death by suffocation
  59. Botox

Doctors warn patients of 'backstreet Botox' dangers

Ian Sample, science correspondent Wednesday November 22, 2006 The Guardian

Doctors have urged patients to avoid "backstreet" Botox treatments after four people were hospitalised

following injections with an unlicensed product.

The patients were admitted to hospital with life-threatening botulism days after receiving injections from a batch

of botulinum toxin A not approved for human use.

The patients, who received between four and six injections into muscles around the eyes, forehead and nose, quickly developed severe fatigue and neurological problems and had to be put on ventilators to support their breathing. Each was given an antidote and spent a minimum of 40 days in hospital.

Interviews with the patients revealed they had received the injections at a private clinic which had acquired a 100 microgramme vial of pure botulinum A neurotoxin, clearly labelled as suitable only for laboratory research.

Further investigations revealed that one of the patients was a doctor working at the clinic despite having had his medical licence revoked. He had diluted the neurotoxin before injecting it into himself and three patients.

The incident is described in the Journal of the American Medical Association by doctors at the US Centres for Disease Control and Prevention in Atlanta. The researchers believe the patients may have received up to 2,857 times the amount of toxin believed to be lethal if injected directly into the bloodstream.

"These patients would have died if they had not been put on life support. It's a wake-up call to physicians that this stuff is out there," said study leader Chris Braden. "During this investigation we've learned about a rather surprising grey or black market for this type of product," he added. Writing in the journal, the doctors said there was an urgent need for fresh controls to ensure research-grade botulinum toxin was only shipped to laboratories that could prove their credentials.

They estimated that the vial obtained by the clinic contained enough botulinum toxin to kill 14,286 adults.

The doctor responsible for administering the injections has since been jailed for three years.

In August, British health inspectors announced a crackdown on beauty clinics after evidence emerged that clients had been disfigured by rogue operators offering improperly administered Botox injections, laser therapy and anti-wrinkle skin fillers.

Faulty injections of Botox can paralyse the wrong muscles, but the effect is usually temporary.

  1. Reflex Action
  2. Simplest nerve pathway is a reflex arc
  3. as few as 2 or 3 nerve cells
  4. short circuit - allows impulses to bypass the brain when a speedy response is necessary
  5. Purpose - to prevent severe damage to tissues
  6. How it works
  7. sensory neurons transmit pain to interneurons in spinal cord
  8. interneurons transmit emergency signal to appropriate motor neurons
  9. body part is jerked away from danger
  10. by the time the parietal section of brain registered pain, you already had jerked away from object

III.  The Brain

  1. 3 Main Parts
  2. Cerebrum - upper part that coordinates thought, memory, and learned behaviors
  3. Cerebellum - lower back part that helps control balance and coordinate voluntary muscle activity
  4. Brain stem - connects the brain to the spinal cord and controls involuntary muscles and activities of autonomic nervous system
  5. The Incredible Design of Brain
  6. Contains about 100 billion neurons each linked to an average of 100,000 other forming more than 10,000,000,000,000,000 connections
  7. Packing all that into a 3 pound brain is like taking all the telephone systems of the world and putting them into a thimble
  8. It is beyond comprehension
  9. Evolution or intelligent design?
  10. Cerebrum
  11. Consciousness, memory, voluntary actions, thinking, and intelligence
  12. Largest part of the brain - divided into right and left hemisphere
  13. split in half by longitudinal fissure
  14. right hemisphere
  15. controls left side body (left-handed)
  16. see big picture
  17. music, artistic, 3-D perception, intuition, imagination
  18. left hemisphere
  19. controls right side (right-handed)
  20. see details
  21. science, math, language, logical thinking
  22. Corpus Callosum - two hemispheres communicate through here
  23. Gray and White matter in Cerebrum
  24. gray matter
  25. made up mostly of cell bodies
  26. lack the white myelin coating
  27. most located in cerebral cortex
  28. outer layer of cerebrum
  29. about 1/8 inch thick
  30. convolutions (deep grooves)
  31. allow for maximum amount of gray matter in limited amount of space
  32. you have about 16 square feet of surface area (about size of beach ball)
  33. white matter
  34. interior of the brain
  35. bundles of myelin-covered nerve fibers
  36. messages generated in cortex travel along nerve fibers to other areas of brain, spinal cord, or body parts
  37. messages also travel to the cortex of the brain from the sense organs so they can be acted upon
  38. Cerebral lobes
  39. through observation of injury, neurosurgery in the 1960’s, now brain mapping they can tell what happens in each lobe
  40. frontal lobe
  41. front - personality, judgment, and self-control
  42. back - motor area of voluntary skeletal muscles
  43. parietal lobe - analyze senses of body and handle actions
  44. occipital lobe - eye sight
  45. temporal lobe - hearing, taste, smell
  46. Cerebellum - muscle coordination
  47. Location and structure
  48. 2nd largest part of brain
  49. behind the brain stem and below occipital lobe of cerebrum
  50. right and left hemisphere
  51. gray and white matter
  52. convolutions are smaller
  53. cortex of cerebellum more dense
  54. Function and purpose
  55. coordinates skeletal muscle activity
  56. relieves the cerebrum from so much work
  57. don’t have to think about walking, driving, brushing your teeth
  58. swimming
  59. uses about every skeletal muscle
  60. when learning cerebrum things about every movement so you won’t drown
  61. as you become more coordinated your cerebellum is being trained
  62. when you are good cerebellum does the work without you thinking about it
  63. Brain Stem - Involuntary Functions
  64. Located between the cerebrum and spinal cord
  65. all nerve cells that go from brain to spinal cord go through this
  66. 3 parts
  67. medulla oblongata
  68. pons
  69. midbrain
  70. Medulla oblongat
  71. lowest part of brainstem
  72. centers that regulate and monitor
  73. breathing
  74. temperature
  75. blood pressure
  76. heartbeat
  77. other vital functions
  78. it triggers sneezing and swallowing
  79. all major pathways (sensory and motor) cross over here giving you right brain - left hand
  80. The pons
  81. just above medulla
  82. Latin word for bridge
  83. links cerebrum to cerebellum
  84. regulates breathing
  85. helps coordinate some eye movement and facial expressions
  86. The midbrain
  87. above the pons
  88. nerve centers in the midbrain help movement of both eyes, adjust pupils to respond to light, help lens to focus
  89. The Master Switch - reticular formation
  90. network of neurons
  91. causes you to wake up - switch on cerebral cortex
  92. causes you to go to sleep - switches off cerebral cortex
  93. keeps you alert and attentive to your surroundings
  94. puts you on high alert when you hear a sudden, loud noise or feel pain to help protect you from danger
  95. if damaged a person may slip into comma (prolonged state of unconsciousness)
  96. keeps your body upright and balanced when not moving
  97. Limbic System - Coordinating Emotions
  98. Several structures lying in the brain core
  99. Coordinate the activity in different parts of your brain
  100. Generate and regulate emotions and desires in coordination with incoming sensory info and the powers of reason in the cerebrum
  101. The organs
  102. Thalamus
  103. located at core of brain
  104. acts like a switchboard sending signals from the reticular formation and sensory nerves to the right place on cerebral cortex
  105. hypothalamus
  106. right below thalamus
  107. control unit for automatic systems
  108. automatic nervous system through the brain stem
  109. endocrine system through the pituitary gland
  110. monitors temperature, pressure, composition of blood and makes adjustments
  111. responsible for physical effects of emotions like rage and fear
  112. directs adrenals to release adrenaline
  113. increases heart rate
  114. pupils dilate
  115. digestion slows
  116. body readies itself for emergency
  117. gives physical desires like hunger and thirst
  118. hippocampus
  119. processes factual memories for storage
  120. amygdala
  121. at back end of hippocampus
  122. generates emotions and helps process emotional memories

IV.  Neurological Health

  1. Caring for the Nervous System
  2. Controlling habits
  3. Unhealthy food you eat, alcohol, cigarettes can destroy your nervous system
  4. Caffeine - too much stimulant
  5. Loud noises - can lead to sensorineural deafness