THE SPINAL CORDUNIT 3, Packet 2

OBJECTIVES:-learn the names of spinal nerves and the order from cervical to caudal-understand the basic structure of the spinal cord-understand how medical personnel test for spinal cord injuries

THIS PACKET BELONGS TO __________________________________________________________. IF YOU FIND THIS PACKET PLEASE RETURN IT TO MS. SIFANTUS IN ROOM 345

OR TO THE SCIENCE DEPARTMENT, ROOM 365. THANK YOU!

Rather than a Reading Guide, please refer to Chapter 13 for help answering questions and labeling diagrams.

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NOTES: THE SPINAL CORD

I. Protection:a.

b.

c.

d.

II.

II. Plexuses

III. Spinal Cord and Spinal Nerve Anatomy

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IV. Two Types of Ascending Pathways send Sensory Info to Brain:a) Anterolateral Spinothalamic

b) Posterior Column Medial Lemniscus

V. Descending Pathways Send Info from the Brain to the Body

VI. Spinal cord injuries

VII. Spina bifida-

What is a Reflex?

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Homework: Answer the following questions.1. Why are reflexes important? In other words, why do medical professionals test reflexes?

2. Dermatomes are the pattern of spinal nerves that innervate the skin. How would you use this to determine spinal cord damage?

3. An elderly person complains to his doctor that he is having trouble controlling his urinary bladder. The doctor finds nothing wrong with the bladder itself. What could the problem be? Be specific-where is the problem located?

4. Polio infects the central nervous system. A person with polio has lost the use of his leg muscles. In which area of his spinal cord would you expect the virus-infected motor neurons to be?

CASE STUDY: A Case of Spinal Cord Injury, byDavid F. Dean, Dept of Biology, Spring Hill College

Introduction: Jason Hendrix is a 21-year-old senior at the University of Delaware, majoring in economics. While on spring break in Florida, Jason was involved in a one- vehicle motorcycle accident. In the accident, Jason was thrown from his bike to the pavement, landing on his back. A police officer witnessed the accident and immediately called for medical assistance. Emergency

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personnel arrived within minutes, and upon recognizing the seriousness of Jason’s back injury, immobilized his neck and secured him to a rigid board prior to transporting him to the emergency room of the nearest hospital.

When he arrived at the hospital, Jason was conscious and complained of pain in his lower back. Upon examination by the emergency room personnel, Jason was found to have numerous abrasions and contusions, and loss of both sensation and motor control of his legs. After he was stabilized, a complete neurological exam was performed to assess and localize Jason’s injury. The neurological exam revealed the following:

Jason demonstrated normal or near normal strength in flexing and extending his elbows, extending his wrists, and when flexing his middle finger and abducting his little finger on both hands. However, he exhibitedno movement when medical personnel tested his ability to flex his hips, extend his knees, and dorsiflex his ankles. Stretch reflexes involving the biceps, brachioradialis, and triceps muscles were found to be normal, while those involving the patella and ankle were absent. In addition, Jason was found to have normal sensitivity to pin prick and light touch in areas of his body above the level of his inguinal (groin) region, but not below that region of the body.

Questions

1. Describe the functional anatomy of the spinal cord using the following terms: white matter, gray matter, tracts, roots, and spinal nerves.

2. Define the terms reflex and spinal reflex, and identify the components of a reflex arc.

3. Define the term spinal cord injury (SCI) and state its prevalence.

4. Define the terms neurological level, tetraplegia (quadriplegia), and paraplegia.

5. Define the terms dermatome and myotome and explain how each relates to SCI.

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6. Define the term stretch reflex and describe how such reflexes are used to anatomically localize SCI.

7. Based upon the results of Jason’s neurological exam, what is the neurological level of his SCI?

8. Discuss the management of SCI and the factors that determined the prognosis for this condition.

Image Credit: Detail of The Injured Mason by Francisco de Goya, –. Oil on canvas. Museo del Prado, Madrid, Spain. Copyright © by the National Center for Case Study Teaching in Science.Originally published // at http://www.sciencecases.org/spinal_cord/spinal_cord.aspPlease see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

LAB #1: REFLEX LAB A reflex is an involuntary response to a stimulus, which begins with a sensory

input, continues through one or more neuronal synapses, and terminates in a motor reaction. The pathway is known as a reflex arc. Many types of reflexes can be found in the body, reflexes ranging from the automatic production of saliva upon seeing food to the automatic movement of a body part in the presence of pain. Reflexes can be simple- involving one synapse or complex, involving 2 or up to 200 synapses! Some reflexes involve only the spinal cord, whereas others are processed in the brain.

Reflexes can be innate or acquired. An innate reflex is genetically or developmentally programmed. Innate reflexes are good indicators of normal development in infants. Examples include suckling, chewing, and tracking objects with the eyes as well as the withdrawal reflex. Acquired reflexes are complex learned motor patterns. Most of you have learned how to drive. Stepping on the brake when you see a person step off the curb is an acquired reflex-you (hopefully) learned when you took

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driving lessons. A skateboarder who adjusts his/her body position when skateboarding to maintain balance is using an acquired reflex.

Reflexes can also be somatic or visceral. A somatic reflex is a stretch reflex of the tendon or the patellar ligament. These are important because they can keep you from falling down the stairs or ripping tendons. A visceral reflex is controlled by the autonomic nervous system. For example, if someone shines a light in one of your eyes, both of your pupils will constrict. Another visceral reflex is urination. When the urinary bladder is full, it stimulates the internal sphincter. After the age of 2 or so (varies a lot!) you develop voluntary control over your external sphincter so you can control when you urinate.

A simple, light tap to a tendon can stimulate contraction of a skeletal muscle. The responding reflex can provide information about the reflex and spinal cord areas associated with specific muscles.

The patellar reflex or knee jerk, is performed by tapping the patellar ligament. Under normal conditions, contraction of the quadriceps femoris muscle will cause extension of the leg. Damage to the second, third, or fourth lumbar segments of the spinal cord or to the afferent and efferent nerves will block the reflex.

The Achilles reflex, or ankle jerk, is performed by tapping the Achilles tendon. Under normal conditions, contraction of the gastrocnemius and soleus muscles will cause extension of the foot. Damage to the first or second sacral segments of the spinal cord or nerves of the posterior leg muscles will block the reflex.

The plantar flexion or Babinski reflex , is performed by stimulating the outer sole of the foot. Under normal conditions extension of the foot occurs in individuals under 6 months of age because the ‘nerve pathways’ have not fully developed. A positive Babinski Reflex in those over 6 months most likely have corticospinal tract lesions-not a good sign.

The triceps reflex is performed by tapping the tendon of the triceps. Under normal conditions, extension of the forearm will occur. This indicates proper functioning of the sixth, seventh, and eighth cervical segments of the spinal cord.

The biceps reflex is performed by tapping the biceps tendon. Under normal conditions, flexion of the forearm will occur. This indicates proper functioning of the fifth and sixth cervical segments of the spinal cord.Spinal Cord Myotomes (http://www.apparalyzed.com/myo-dermatomes.html)Myotomes: relationship between spinal nerve and muscle Dermatomes: relationshihp between spinal nerve and skin

Each muscle in the body is supplied by a particular level or segment of the spinal cord, and its corresponding spinal nerve. This is approximately the same for every person. See the list below to help you determine which spinal nerves are stimulated when you test the various reflexes.

C3,4, and 5 supply the diaphragmC5 supplies the shoulder muscles and the muscle we use to bend the elbowC6 supplies muscle that bends wristC7 muscles that straighten the elbow

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C8 bends the fingersT1 spreads the fingersT1-12 supplies the chest wall and abdominal musclesL2 bends the hipL3 straightens the kneeL4 pulls the foot up (flexes the foot)L5 wiggles the toesS1 extends the foot (pulls the foot down)S3, 4, and 5 supply the bladder, bowel and sex organs, and anal and other pelvic muscles

PART I. Draw a diagram of a simple reflex diagram. Apply your best artistic skills.

PART II. Perform the following procedures with your partner.

PROCEDURE A: PATELLAR REFLEX 1. Have your laboratory partner sit on a table and let his or her leg hang free. 2. Using the medial side of your hand, tap the patellar tendon just below the knee. 3. Lack of a response might indicate damage to which spinal nerve?

__________________ PROCEDURE B: ACHILLES REFLEX

1. Have your laboratory partner kneel on a stable chair while letting the feet hang free over the edge of the chair.

2. Using your hand again, tap the Achilles tendon. 3. Lack of a response might indicate damage to which spinal nerve? _________________

PROCEDURE C: BABINSKI REFLEX

1. Have your laboratory partner sit on a table and let the leg hang free. 2. Using a plastic pen cap, lightly stimulate the outer margin of the sole (from the

heel to the toe). 3. Note the response: _________________________________________4. Lack of a response might indicate damage to which spinal nerve?

______________________ PROCEDURE D: TRICEPS REFLEX

1. Place your laboratory partner's elbow in your left hand; using your hand, tap the triceps tendon.

2. Lack of a response might indicate damage to which spinal nerve? ______________________

PROCEDURE E: BICEPS REFLEX

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1. Have your laboratory partner rest his or her arm on the arm of a chair. Place your thumb on the biceps tendon and tap your thumb.

2. Lack of a response might indicate damage to which spinal nerve? ______________________

PROCEDURE F: EYE REFLEXES, ETC

1. Ask your partner to sit quietly with eyes closed and glasses removed. With your middle finger, sharply tap the glabella (flattened portion of the forehead) and observe the results. Look for eye movements. Observations:

PROCEDURE G (OPTIONAL) ABDOMINAL REFLEX1. Stroke the skin starting superior to the umbilicus and to the side or just

inferior to the belly button. 2. Which group of spinal nerves do you think innervate this area?

______________________

IF YOU HAVE TIME…a. Have your partner place his/her hand between the eyes while looking

straight forward. Shine the light in one eye and record what happens in the OTHER eye. Record Observations:

ANALYSIS QUESTIONS1. What is the difference between a somatic and visceral reflex? Explain. List at least one example of a somatic reflex and one visceral reflex.

2. What is the difference between an innate and an acquired reflex? Which of the above reflexes do you think is an innate reflex? An acquired reflex?

3. Label the diagram of the spinal cord with the spinal nerves (cervical 1---, Thoracic 1---, etc) and the reflexes that can be tested to indicate damage to that part of the spinal cord. Be specific. For example, L3-patellar reflex. BE NEAT! Extra credit- find one reflex that we did not test.

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SPINAL CORD TAKE HOME ‘QUIZ’ HONOR: Answer all questions. Write legibly! REGULAR CREDIT: Choose 4 questions. BE SPECIFIC IN YOUR ANSWERS. NAME THE SPINAL NERVE THAT IS AFFECTED, IF APPROPRIATE. USE EXAMPLES WHEN APPROPRIATE.

1. An epidural block is a procedure that physicians use to anesthetize the lower part of the body. It is often performed for women who are giving birth. Where do physicians insert the needle and why is it inserted at that spot?

2. a) What is the evolutionary advantage for having reflexes? b) Use a specific reflex in your explanation. c) Why do doctors test reflexes?

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3. Two patients admitted to the emergency room were in a car accident. One of the patients was dead on arrival (DOA) after having sustained a severed spinal cord at the level of C2. The other patient suffered a similar injury, but at the level of C6 and is still alive. Explain briefly, in terms of the origin and function of the phrenic nerves, why one injury was fatal and the other was not.

4. Evil Kneivel’s son (who even remembers his name anyway) was attempting to ride his motorcycle up a ramp and jump over 28 Hummers when the sleeve of his kylar jacket got caught on a fence post, spinning him around and slamming him into an ice pick which sliced a 3 inch deep gash at the location of his 5th cervical spinal nerve, right side. What’s your diagnosis? (he lived by the way)

5. Harry was having a regular checkup with his doctor who tapped his knee with a little hammer. Why did he do that? Harry had no response. Should we be worried?6. Mabel was attacked by a swarm of mosquitoes, yet she was unable to feel any itching. At first she thought “Well good! Those doggoned mosquitoes don’t bother me!” But, then she realized she couldn’t feel anything when her sister was tickling her feet. Odd, she thought! What diagnosis can you give poor Mabel? Mabel can walk, so it’s not because she is paralyzed.

7. Sven (ya!) entered the hospital with a blinding headache and fever. Immediately the doctor on call ordered a spinal tap/puncture. Why? What does he suspect Sven has?

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