1. The Nervous System: Part One: The Information Super Highway9
The Nervous System: Part One: The Information Super Highway

2. Multimedia Asset Directory
Slide 36 Multiple Sclerosis Animation
Slide 46 Neurosynapses Video
Slide 51 Muscle Contraction Animation
Slide 64 Epidural Placement Video
Slide 80 Spinal Cord Anatomy Animation
Slide 81 Brachial Plexus Animation
Slide 82 Lumbrosacral Plexus Animation
Slide 85 Cervical Spine Injuries Video
Slide 91 Reflex Arc Animation
Slide 113 Carpal Tunnel Syndrome Video
Slide 114 Electroneurodiagnosticians Video

3. Introduction
The nervous system is complex and important to the body’s control system.
The nervous system monitors conditions and takes corrective action, when necessary, to keep everything running smoothly.

4. Introduction
The control systems of your body are the nervous and endocrine systems which receive help from your special senses.
Like any control system, they have a large, complex job that is sometimes difficult to understand. Thus, the systems themselves are perhaps the most complex and vital systems.

5. Learning Objectives
List and describe the components and basic operation of the nervous system.
Contrast the central and peripheral nervous systems.
Define the parts and functions of the nervous tissue.
Discuss the anatomy and physiology of the spinal cord.
List and describe various disorders of the nerves and spinal cord.

6. Pronunciation Guide arachnoid mater (ah RAK noyd MAY ter)
Click on the megaphone icon before each item to hear the pronunciation.
arachnoid mater (ah RAK noyd MAY ter)
astrocytes (ASS troh SITES)
axon (AK sahn)
cerebrospinal fluid (SER eh broh SPY nal)
chemical synapse (SIN naps)
commissures (KAHM ih shoorz)
corticobulbar tract (KOR ti coe BUL bar)
corticospinal tract (KOR ti coe SPY nal)
dendrites (DEN drights)

7. Pronunciation Guide dorsal root ganglion (GANG lee on)
Click on the megaphone icon before each item to hear the pronunciation.
dorsal root ganglion (GANG lee on)
dura mater (DOO rah MAY ter)
ependymal cells (eh PEN deh mall)
epidural space (EPP ih DOO rall)
ganglia (GANG lee ah)
glial cells (GLEE all)
gyri (JIE rie)
meninges (men IN jeez)
microglia (my KROG lee ah)

8. Pronunciation Guide myelin (MY eh lin)
Click on the megaphone icon before each item to hear the pronunciation.
myelin (MY eh lin)
neuroglia (glial cells) (noo ROG lee ah)
nodes of Ranvier (ron vee AYE)
oligodendrocytes (AH li go DEN droe sites)
pia mater (PEE ah MAY ter)
plexus (PLECK sus)
Schwann cells (SHWAN)
somatic nervous system (so MAT ick)
spinocerebellar tract (SPY no ser eh BELL ar)

9. Pronunciation Guide spinothalamic tract (SPY no thol AH mic)
Click on the megaphone icon before each item to hear the pronunciation.
spinothalamic tract (SPY no thol AH mic)
subarachnoid space (SUB ah RACK noyd)
subdural space (sub DOO ral)
sulcus (SULL cus)
vesicles (VESS ih kulz)

10. Parts and Basic Operations
The brain and spinal cord is the central nervous system (CNS) which controls the total nervous system.
Everything outside the brain and spinal cord is part of the peripheral nervous system (PNS).
The input side of the nervous system is the sensory system.
The output side of the nervous system is the motor system.

11. Parts and Basic Operations
The somatic nervous system controls skeletal muscle and mostly voluntary movements.
The autonomic nervous system controls smooth muscle and cardiac muscle, along with several glands.
The autonomic system is divided into the parasympathetic system that deals with normal body functioning while the sympathetic nervous system controls the “fight or flight” response system.

12. Figure 9-1 Organization of the nervous system.

13. Real Life Example
You park your car and get out to visit a friend. As you step on the walk a large dog bounds down the steps barking and snarling at you.
Your sensory system gathers information including; a large unfriendly dog, you are far from the protection of your car, and no one is around to help.
The information goes into your spinal cord and brain and you process the information to make decisions. You are in danger; something must be done!

14. Real Life Example
Your CNS sends directions to your organs to gear up for action via the autonomic nervous system.
Your heart rate, blood pressure, and respiration rate increase. You begin to sweat. More blood is delivered to your skeletal muscles and heart in order to get you fully ready to respond. This is all involuntary, meaning you cannot consciously control it.

15. Real Life Example
Your somatic nervous system readies your skeletal muscles to get you out of there. This is often called the “fight or flight” response and will be discussed later in further depth. If you can control your fear, you back slowly away from the situation. If you are scared witless, you run from the yard as fast as possible. Either way, you can hopefully escape the danger, with your skin and pride intact.

16. Neuroglia
Specialized cells in the nervous system called neuroglia, or glial cells, perform specialized functions.
In the CNS there are four types of glial cells
Astrocytes – metabolic and structural support cells
Microglia – remove debris
Ependymal cells – cover and line cavities of the nervous system
Oligodendrocytes – make a lipid insulation called myelin

17. Neuroglia In the PNS there are two types of glial cells:
Schwann cells – make myelin for the PNS
Satellite cells – support cells

18. Figure 9-2 Glial cells and their functions.

19. Neurons
All of the control functions of the nervous system must be carried out by a group of cells called neurons.
Neurons have many branches and even what appears to be a tail.

20. Neurons Each part of a neuron has a specific function
Body – cell metabolism
Dendrites – receive information from the environment
Axon – generates and sends signals to other cells
Axon terminal – where the signal leaves the cell
Synapse – where the axon terminal and receiving cell meet

21. Figure 9-3 A neuron connected to a skeletal muscle.

22. Classification of Neurons
Neurons can be classified by how they look (structure)
Unipolar – 1 process with a peripheral and central projection
Bipolar – 2 processes, 1 axon and 1 dendrite
Multipolar – many processes
Or what they do (function)
Input neurons are known as sensory neurons.
Output neurons are known as motor neurons.
Neurons which carry information between neurons are called interneurons (inter – between) or association neurons.

23. How Neurons Work
Neurons are a kind of cell called an excitable cell. This simply means that if the cell is stimulated it can carry a small electrical charge.
Each time charged particles flow across a cell membrane, there is a tiny charge generated.
All three muscle types are excitable cells, as are many gland cells.

24. How Neurons Work
Cells are like miniature batteries, able to generate tiny currents simply by changing the permeability of their membranes.

25. Action Potential
A cell that is not stimulated or excited is called a resting cell; it is said to be polarized.
It has a difference in charge across the membrane, being more negative inside than outside the cell.
When the cell is stimulated:
Gates (called sodium gates) in the cell membrane spring open allowing sodium to travel across the membrane.

26. Action Potential When the cell is stimulated:
These sodium bits are positively charged, so the cell becomes more positive as they enter.
A cell that is more positive is called depolarized.
The sodium gates close.
Potassium gates open and potassium leaves the cell, taking its positive charge with it. This is called repolarization.

27. Action Potential When the cell is stimulated:
If the cell becomes more negative than resting it is called hyperpolarized.
Action potential (AP) is the cell moving through depolarization, repolarization, and hyperpolarization.
The cell cannot accept another stimulus until it returns to its resting state, and this time period when it cannot accept another stimulus is called the refractory period.

28. Figure 9-4 Depolarization and repolarization.

29. Local Potentials
Neurons can use their ability to generate electricity to send, receive, and interpret signals.
If you hit your thumb with a hammer, dendrites in your thumb are stimulated by the blow and sodium gates open, sodium flows into the dendrites and they become depolarized. The number of cells affected depends on how hard you hit your thumb.

30. Local Potentials
In local potential the size of the stimulus determines the excitement of the cell. Many sensory cells work via local potentials, which is how your CNS determines the size of the environmental change.
The dendrites carry the depolarization to the sensory neuron cell body, which takes the information and generates an action potential if the stimulus is big enough.

31. Local Potentials
One difference between action potentials and local potentials is that action potentials are “all-or-none,” meaning the depolarization always finishes and is always the same size, while local potentials vary in size depending on the stimulus.

32. Impulse Conduction
The speed of impulse conduction is determined by the amount of myelin and the diameter of the axon.
Myelin is a lipid insulation or sheath formed by the oligodendrocytes in the CNS and Schwann cells in the PNS.
Myelinated nerves look white while unmyelinated nerves are gray.

33. Impulse Conduction
Myelin is essential for speedy flow of AP’s down the axons. In an unmyelinated axon, the AP can only flow down the axon by depolarizing each and every centimeter of the axon (a relatively slow process). In myelinated axons there are nodes located periodically, and only the nodes must depolarize, allowing the impulse to travel quickly as it skips from node to node.

34. Figure 9-5 Impulse conduction via myelinated axon.

35. Clinical Application: Multiple Sclerosis
Multiple sclerosis (MS) is a disorder of the myelin in the CNS. Many areas of myelin are destroyed. In these areas, impulse conduction is slow or impossible. Symptoms of MS differ depending on where the myelin damage occurs. Disturbances in balance, vision, speech, or movement is possible. MS occurs more in women, and patients are usually under 50.

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37. Impulse Conduction and Diameter
The diameter of the axon also affects the speed of the AP flow. The wider the diameter of the axon, the faster the flow of ions.
Myelination and larger diameters allow for a huge difference in speed.

38. Impulse Conduction and Diameter
Small unmyelinated axons have speeds as low as 0.5 meters/second while large-diameter myelinated axons may be as fast as 100 meters/second. That’s 200 times faster!!

39. How Synapses Work
When the AP arrives at the axon terminal, the terminal depolarizes and calcium gates open. Calcium flows into the cell. When calcium flows in, it triggers a change in the terminal.

40. How Synapses Work
There are tiny sacs in the terminal called vesicles which release their contents from the cell when calcium flows in. These vesicles are filled with molecules, called neurotransmitters, used to send the signal from the neuron across the synapse to the next cell in line.

41. Neurotransmitters
The neurotransmitters bind to the cell receiving the signal, opening or closing gates. Some excite the receiving cell and some calm it down.
The last step in the transfer of information is to clean up, removing the neurotransmitter from the synapse to prevent it from binding to the receiving cell.

42. Neurotransmitters
This type of synapse is called a chemical synapse because neurotransmitters carry the information from one cell to another.

43. Figure 9-6 The Chemical Synapse
Figure The Chemical Synapse. Step 1: The impulse travels down the axon. Step 2: Vesicles are stimulated to release neurotransmitter (exocytosis). Step 3: The neurotransmitter travels across the synapse and binds with the receptor site of post synaptic cell. Step 4: The impulse continues down the dendrite.

44. Chemical Synapses and Medications
Our understanding of chemical synapses has lead to several breakthroughs for treating mental illness.
Many medications on the market today are designed to modify synapses.

45. Chemical Synapses and Medications
Selective serotonin reuptake inhibitors (SSRIs) are good examples. These medications prevent the clean up of the neurotransmitter serotonin from synapses, thus increasing the effects of serotonin on the receiving cell.
Many antidepressants and anti-anxiety drugs are SSRIs.

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47. Table 9-1 Selected Common Neurotransmitters.

48. Electrical Synapses
Some cells do not need the chemicals to transmit information from one cell to another.
These synapses are electrical synapses, transferring information freely because they have special connections called gap junctions.
These kinds of connections can exist between any types of excitable cells.
They are found in the intercalated discs between cardiac muscle fibers.

49. The Neuromuscular Junction
The neuromuscular junction is a chemical synapse creating a specialized synapse between somatic (voluntary) motor neurons and the skeletal muscles they innervate.
The surface of the muscles is studded with sodium channels that are ligand gated. These open or close when a molecule binds to a receptor that is part of the channel, like a key fitting into a lock.

50. The Neuromuscular Junction
In the case of skeletal muscles, the ligand is the neurotransmitter acetylcholine, which is released from the terminal of a motor neuron and binds to the surface of skeletal muscle, opening sodium channels and causing the skeletal muscle to depolarize. The muscle then contracts.
Acetylcholinesterase is the enzyme responsible for cleaning up the synapse.

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52. Spinal Cord and Spinal Nerves
The spinal cord is a hollow tube running inside the vertebral column, from the foramen magnum to the second lumbar vertebrae.
The spinal cord is like a sophisticated neural information superhighway.
There are 31 segments, each with a pair of spinal nerves, named for the corresponding vertebrae.

53. Spinal Cord and Spinal Nerves
The spinal cord ends at L2 in a pointed structure called the conus medullaris. Hanging from the conus medullaris is the cauda equina (horses tail), spinal nerves which dangle loosely and float in a bath of cerebral spinal fluid (CSF).
The spinal cord has two widened areas, the cervical and lumbar enlargements, which contain the neurons for the upper and lower limbs respectively.

54. Figure 9-7 The spinal cord.

55. Meninges
The meninges are a protective covering of both the brain and spinal cord.
They help to set up layers that act as cushioning and shock absorbers.
dura mater
outer layer is thick fibrous tissue

56. Meninges
They help to set up layers that act as cushioning and shock absorbers.
arachnoid mater
middle layer is a wispy, delicate layer, resembling a spider web, composed of collagen and elastic fibers acting as a shock absorber and transporting dissolved gases and nutrients as well as chemical messengers and waste products

57. Meninges
They help to set up layers that act as cushioning and shock absorbers.
pia mater
innermost layer, fused to the neural tissue, containing blood vessels that serve the brain and spinal cord

58. Meningeal Spaces A series of spaces are associated with the meninges.
Between the dura mater and the vertebral column is a space filled with fat and blood vessels called the epidural space.
Between the dura mater and the arachnoid mater is the subdural space filled with a tiny bit of fluid.
Between the arachnoid mater and the pia mater is the large subarachnoid space filled with CSF that acts as a fluid cushion.

59. Meningeal Spaces
These three membranes and their fluid-filled spaces, together with the bones of the skull and vertebral column, form a strong protective system against CNS injury.

60. Figure 9-8 The meninges of the brain and spinal cord.

61. Figure 9-8 (continued) The meninges of the brain and spinal cord.

62. Clinical Application: Epidural Anesthesia
Often during labor, or in preparation for a cesarean section, a woman will receive “an epidural.” An epidural is an injection of local anesthesia into the epidural space. The anesthetic is usually delivered via a catheter (small tube). Ideally, epidural anesthesia allows a woman to continue to participate actively in the birth without severe labor pains.

63. Clinical Application: Epidural Anesthesia
Epidural injections of steroids are sometimes prescribed for patients with chronic lower back injuries to relieve pain and inflammation.

64. Click here to view a video on the topic of Epidural Placement.
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65. Internal Anatomy of the Spinal Cord
The spinal cord is divided in half by an anterior median fissure (deep groove) and a posterior median sulcus (shallow groove).
The interior of the spinal cord is then divided into a series of sections of white matter columns and gray matter horns.

66. Internal Anatomy of the Spinal Cord
There are three types of horns: the dorsal horn is involved in sensory functions, the ventral horn involved in motor function, and the lateral horn dealing with autonomic functions. The horns are the regions where the neuron’s cell bodies reside.

67. Internal Anatomy of the Spinal Cord
There are also dorsal, lateral, and ventral columns, the white matter of the spinal cord. These columns act as nerve tracts, pathways, or axons, running up and down the spinal cord to and from the brain.

68. Internal Anatomy of the Spinal Cord
Ascending pathways carry information from your sense of touch to the spinal cord and then to your brain from all parts of the skin, joints, and tendons.
The dorsal column tract carries fine-touch and vibration information to the cerebral cortex.
The spinothalamic tract carries temperature, pain, and crude touch information to the cerebral cortex.

69. Internal Anatomy of the Spinal Cord
Ascending pathways carry information from your sense of touch to the spinal cord and then to your brain from all parts of the skin, joints, and tendons.
The spinocerebellar tract carries information about posture and position to the cerebellum.

70. Internal Anatomy of the Spinal Cord
Descending pathways carry motor information (orders for voluntary movements) from the brain to the spinal cord. The axons from all pathways synapse on motor neurons in the ventral horn.
The corticospinal tract carries orders from the brain to the motor neurons in the ventral horn of the spinal cord.

71. Internal Anatomy of the Spinal Cord
The axons from all pathways synapse on motor neurons in the ventral horn.
The corticobulbar tract carries orders from the brain to motor neurons in the brain stem (more details later).
The reticulospinal and rubrospinal tracts (along with several other tracts) carry information from the brain to the brain stem and ventral horn, which helps to coordinate movements.

72. Internal Anatomy of the Spinal Cord
The commissures, gray and white, connect left and right halves of the cord so the two sides of the CNS can communicate. The central canal is a cavity in the center of the spinal cord filled with CSF.
The spinal roots project from both sides of the spinal cord in pairs, and fuse to form spinal nerves.

73. Internal Anatomy of the Spinal Cord
The dorsal root, with the embedded dorsal root ganglion, a collection of sensory neurons, carries sensory information while the ventral root is motor.

74. Figure 9-9 Internal anatomy of the spinal cord.

75. Spinal Nerves
Nerves are the connection between the CNS and the world outside the CNS.
Nerves are, therefore, part of the PNS.
All nerves consist of bundles of axon, blood vessels, and connective tissue.
Nerves run between the CNS and organs or tissues, carrying information into and out of the CNS.

76. Spinal Nerves
The nerves connected to the spinal cord are called spinal nerves, each named for the spinal cord segment to which they are attached.
All spinal nerves are mixed nerves which means they carry both sensory and motor information.

77. Spinal Nerves
Spinal nerves from the thoracic spinal cord project directly to the thoracic body wall without branching, while all other spinal nerves branch extensively, recombining with nerves from other spinal cord segments before projecting to peripheral structures. These complex branching patterns are called plexuses.

78. Figure 9-10 Spinal cord plexuses.

79. Figure 9-10 (continued) Spinal cord plexuses.

80. Click here to view an animation on the topic of the Spinal Cord
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81. Click here to view an animation on the topic of the Brachial Plexus
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82. Click here to view an animation on the topic of the Lumbrosacral Plexus. The animation may take a moment after clicking to begin playing.
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83. Clinical Application: A Matter of Centimeters
Did you know that the difference between being able to breathe on your own after a spinal cord injury and being dependent on a ventilator is literally a matter of centimeters? One of the nerves that projects from the cervical plexus is a nerve called the phrenic nerve, a motor nerve for your diaphragm, your main breathing muscle.

84. Clinical Application: A Matter of Centimeters
If the spinal cord is damaged below the cervical plexus the phrenic nerve still functions, while an injury between the brain and the cervical plexus blocks the path to the phrenic nerve paralyzing your diaphragm.

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86. From the Streets: Spinal Cord Injuries
Spinal-cord injuries vary in severity:
Cord concussion
Cord contusion
Cord compression
Cord lacerations
Complete transection
Incomplete transection
Cord hemorrhage

87. From the Streets: Spinal Cord Injuries
Several syndromes can develop with spinal-cord injury.
Anterior-cord syndrome
Central-cord syndrome
Brown-Séquard syndrome
Cauda equina syndrome
Spinal shock

88. Figure 9-12 Mechanisms associated with cervical spine, vertebral, and spinal cord injury.

89. Reflexes Reflexes are the simplest form of motor output you can make.
Reflexes are generally protective, involuntary, and usually get bigger as the stimulus gets bigger.
Some familiar reflexes are the patellar reflex, which keeps you vertical, and your startle reflex, which causes you to jump at loud sounds.

90. Reflexes
The amazing thing about reflexes is that they can often occur without your brain being involved, involving only your spinal cord.

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92. From the Streets: Reflexes
Reflex testing can be a useful examination tool.
Stretch reflexes evaluated by tapping on a part of a muscle with a reflex hammer
Table 9-2 illustrates how responses are graded.

93. Table 9-2 Mechanisms associated with cervical spine, vertebral, and spinal cord injury.

94. From the Streets: Reflexes
Decreased reflex (hypoflexia) or absent reflex (areflexia) may result from temporary or permanent damage to:
Skeletal muscles
Dorsal or ventral nerve roots
Spinal nerves
The spinal cord
The brain

95. From the Streets: Reflexes
Increased reflex (hyperreflexia) usually stems from diseases that affect higher centers or descending tracts.

96. From the Streets: Reflexes
Babinski reflex
This reflex should be assessed in all critically ill or critically injured patients
Characterized when the big toe dorsiflexes and the other toes fan out when the bottom of the foot is stroked along the lateral aspect of the sole.

97. Figure 9-13 Abdominal reflex
Figure Abdominal reflex. Gently stroking the skin of the abdomen should cause contraction of the underlying muscles and move the umbilicus toward the location of the stimulation.

98. Figure 9-13 Plantar reflex
Figure Plantar reflex. Stroking the lateral aspect of the plantar surface of the foot should cause plantar flexion of the toes. Dorsiflexion of the great toe and fanning of the other toes following stimulation is considered a positive Babinski reflex, which suggests problems with higher centers within the brain.

99. Common Disorders of the Nervous System: Part I
Peripheral neuropathy
Spinal trauma
Guillain-Barré syndrome
Myasthenia gravis
Botulism
Meningitis
Carpal tunnel syndrome

100. Peripheral Neuropathy
Peripheral neuropathy refers to a number of disorders involving damage to peripheral nerves.
Symptoms vary depending on whether the sensory, motor, or autonomic function is affected.

101. Peripheral Neuropathy
Symptoms include muscle weakness, decreased reflexes, numbness, tingling, paralysis, pain, abnormal sweating, digestive abnormalities, and difficulty controlling BP.
Non-genetic neuropathy can be grouped as systemic disease, trauma, and infection or autoimmune disorders.

102. Spinal Trauma
Even though the spinal cord is protected, it can be damaged by trauma.
The spinal cord can be partially or completely severed, crushed, or bruised. Bruises may resolve with time.

103. Spinal Trauma
Spinal cord injury usually results in paralysis and sensory loss below the injury.
Cervical injury may result in quadriplegia, and if the diaphragm is paralyzed the individual can’t breathe on their own.
Thoracic spinal cord damage and lower causes paraplegia. Patients can move their arms.

104. Guillain-Barré Syndrome
Guillain-Barré syndrome (GBS) is a rapid onset paralysis caused by inflammation of peripheral nerves.
Patients develop weakness and ascending paralysis.
Severe cases require a ventilator to support breathing until paralysis resolves.
The disorder is temporary and many patients require rehabilitation after recovery.

105. Guillain-Barré Syndrome
The cause is unknown, but may be viral infection or autoimmune.

106. Myasthenia Gravis Myasthenia gravis is an autoimmune disorder.
The immune system attacks and destroys acetylcholine receptors at the neuromuscular junction.
Motor neurons continue to release acetylcholine but the receptor number is reduced so motor neurons can’t communicate with skeletal muscles.

107. Myasthenia Gravis
Eye muscles are usually the first affected. Some patients experience difficulty swallowing, chewing, or talking.
The disease is progressive, but the course of disease varies among patients.
Treatment includes cholinesterase inhibitors, corticosteroids, immunosuppressant drugs, and plasma exchange. A few patients spontaneously recover.

108. Botulism
Botulism is a form of paralysis caused by toxins produced by the bacterium Clostridium botulinum.
Botulism can be caused by ingesting the toxin in food or from a wound infection.
The bacteria grows most commonly in improperly prepared canned food, especially home-canned food.

109. Botulism
The toxin keeps neurotransmitters from being released at the neuromuscular junction, causing paralysis.
Initial symptoms include visual disturbances, slurred speech, dry mouth, and muscle weakness. Paralysis will spread to limbs and respiratory muscles.
Botulism is treated with anti-toxin and supportive care.

110. Meningitis
Meningitis is an infection, from either viruses or bacteria, of the meninges.
Bacterial meningitis is a potentially fatal infection.
The bacteria first infect the upper respiratory tract and then travel to the meninges.

111. Meningitis
At-risk patients include the elderly, immunosuppressed, very young children, and college students who live in dorms.
Survivors of meningitis often have severe neurological impairment, including deafness and severe brain damage.
Viral meningitis is a much milder version of the disease and is caused by viruses that enter the mouth before traveling to the meninges.

112. Carpal Tunnel Syndrome
Carpal tunnel syndrome is an inflammation and swelling of the tendon sheathe surrounding the flexor tendon of the palm.
This is a result of repetitive motion, such as typing on a keyboard.
As a result of the inflammation, the median nerve is compressed producing tingling sensations or numbness of the palm and first three fingers.

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114. Click here to view a video on the topic of Electroneurodiagnosticians.
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115. Snapshots from the Journey
The nervous system is the body’s computer. It has a sensory, integration, and motor system. The input and output nerves are in the PNS, and the brain and spinal cord are the SNS.
The tissue of the nervous system is made up of two types of cells: neurons, which send, receive, and process information, and neuroglia, which support the neurons.

116. Snapshots from the Journey
Neurons are excitable cells. They do their jobs by carrying tiny electrical currents caused by changes in cell permeability to certain ions. These tiny electrical currents can be all-or-none responses (action potentials), can change depending on the size of the stimulus (local potentials), can travel down axons (impulse conduction), or can be used to transmit information from one cell to another (synapses).

117. Snapshots from the Journey
Your CNS is surrounded by a three-layered membrane system: dura mater, arachnoid mater, and pia mater, collectively known as the meninges. Cerebrospinal fluid is also contained in the space between the arachnoid and pia maters.

118. Snapshots from the Journey
The spinal cord has 31 segments, each with a pair of spinal nerves. The spinal nerves are a part of the peripheral nervous system.

119. Snapshots from the Journey
The spinal nerves are made of a pair of spinal roots. The ventral root is integral to motor function, and the dorsal root is integral to sensory function. Spinal nerves are mixed; they carry both sensory and motor information.

120. Snapshots from the Journey
A series of tracts run up and down the spinal cord to and from the brain. The tracts going toward the brain carry sensory information to the brain. The tracts coming from the brain toward the spinal cord carry motor information from the brain.

121. Case Study
During the biggest game of his high school football career, Bill, the best wide receiver in the league, leaps high into the air in the end zone to score the game-winning touchdown. A player for the other team hits him hard, knocking him into the goal post. Bill crumples to the ground, unmoving. When the EMT’s get to him, Bill is paralyzed on both sides of his body and in respiratory arrest.

122. Case Study Questions Where is Bill’s injury most likely located?
How can you tell?

123. From the Streets
A 60-year-old female drives to your EMS department because she is experiencing “numbness and tingling” in her hands & fingers. Your patient interview reveals that the complaint has been going on for almost three months and has become worse over the last two weeks. She has a history of diabetes.

124. From the Streets Questions
What division of the nervous system is involved in her condition?
What is the term that describes her feeling of “numbness and tingling”?
What is the most likely diagnosis?
What is her prognosis?

125. From the Streets Questions
What division of the nervous system is involved in her condition? The peripheral nervous system
What is the term that describes her feeling of “numbness and tingling”? Paresthesia
What is the most likely diagnosis? Peripheral neuropathy
What is her prognosis? Peripheral neuropathy is a chronic & degenerative disease process

126. End of Chapter Review Questions
The input side of your nervous system is known as:
Motor
Sensory
Association
All of the above

127. End of Chapter Review Questions
Neurons with a central and peripheral projection are known as:
Unipolar
Bipolar
Multipolar
Northpolar

128. End of Chapter Review Questions
During depolarization ____ ions move ___ a neuron.
K+, out of
K+, into
Na+, out of
Na+, into

129. End of Chapter Review Questions
The ventral root of the spinal cord is:
Sensory
Motor
Association
None of the above

130. End of Chapter Review Questions
Spinal nerves carry what kind of information?
Sensory
Motor
Mixed
Vertebral

131. End of Chapter Review Questions
A spinal injury at T3 would cause:
Paralysis of all four limbs
Paralysis from the waist down
Paralysis in all four limbs and respiratory arrest
Paralysis of the arms

132. End of Chapter Review Questions
Sodium channel blockers, which prevent sodium channels from working, would block what part of the action potential?
Hyperpolarization
Depolarization
Repolarization
Afterpotential

133. End of Chapter Review Questions
Multiple sclerosis is often associated with a decrease in these neuroglia.
Astrocytes
Schwann cells
Oligodendrocytes
Microglia

134. End of Chapter Review Questions
The speed of impulse conduction is determined by _______ and ______.
________ potentials are all or none.
The spinal cord has white matter _______ and gray matter ______.
_______ fluid is contained in the ______ space between the arachnoid mater and pia mater.

135. End of Chapter Review Questions
A ______ is an involuntary, protective movement that is generated without the brain.
The virus polio causes loss of motor function but not of sensory function, because it infects neurons. These neurons are located in the ___________ horn of the spinal cord.

136. End of Chapter Review Questions
Explain the changes in a neuron during an action potential.
List the steps in chemical synaptic transmission.
List the layers of protection around the CNS.
List the types of neuroglia and their functions.
Explain the results of spinal cord injuries in the following locations: C2, T3 and L2.