CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

LABORATORY 5: CRANIAL NERVE AND REFLEX TESTING REMINDER:

bring a calculator to class

AND

wear clean socks!!

PART 1 : CRANIAL NERVES Purpose 1. review the general functions of the cranial nerves 2. describe a clinical test for the function of each cranial nerve (see lab manual p 2 and 3) Review of cranial nerve functions:

NAME

FUNCTION

I

II

III

IV

V

VI

VII

VIII

IX

X

XI

XII

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

TESTS OF CRANIAL NERVE FUNCTION One method of assessing neurological damage is to test cranial nerve function. Working with a partner, perform the following tests as instructed that demonstrate cranial nerve function. Your assignment involves determining which cranial nerve(s) is/are assessed by which test. Test A. cranial nerve tested = __________________________________________ Ask the subject to: wrinkle the forehead by looking upward, close the eyelids forcefully while you try to pry them open, show the teeth and to whistle or purse the lips, draw the lower lip and mouth downward while tensing the surface of the skin of the neck, similar to the action that men use while shaving. Test B. cranial nerve tested = __________________________________________ Ask the subject to gaze at a distant point, and compare the size of the two pupils. Gazing far away is important to avoid the pupillary constriction that occurs during the accommodation reflex. As the subject gazes into the distance, move a bright flashlight in from the sides to illuminate each eye separately. The eye into which the light is shining should demonstrate a prompt pupillary constriction. This is the direct pupillary response. The opposite eye should show an equal constriction. This is the consensual pupillary response. Each eye should be tested separately. Test C. cranial nerve tested = __________________________________________ Ask the subject to close their eyes and occlude one nostril. Present to the non-occluded nostril the test stimulus, and ask the subject to sniff and identify the odor if possible. Non-irritating odors such as a stick of gum, ground coffee or tobacco may be used. The other nostril is tested in a similar fashion.

Test D. cranial nerve tested = __________________________________________ Ask the subject to look downwards without changing the position of their head.

Test E. cranial nerve tested = __________________________________________ Ask the subject to look to the side without changing the position of their head (move eyes laterally).

Test F. cranial nerve tested = __________________________________________ Ask the subject to protrude their tongue on the midline past the teeth, and to wiggle it from side to side. In the normal case, the patient will be able to move the tongue on the midline without any deviation.

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

Test G. cranial nerve tested = __________________________________________ Have the subject close his/her eyes. Lightly whisk a piece of dry cotton over the mandibular, maxillary and ocular areas of the face. Check both sides of the face. Have the subject clench his/her teeth and hold one hand firmly under his/her chin, then open their mouth. This tests the motor function of the mandibular branch of this nerve. Test H. cranial nerve tested = __________________________________________ Ask the subject to close his/her eyes and snap your fingers about 1 meter away from the left or right side of the head. Ask her/him to identify the direction from which the sound is coming. Test I. cranial nerve tested = __________________________________________ Ask the subject to cover their right eye and look at your right eye with their left eye. You should be positioned at about an arm's length away from the patient. Utilize your finger as a target by wiggling it and moving it from outside your peripheral visual field to inside. Ask the subject to report when she/he sees it. All four quadrants should be tested (it is most efficient to test at about 45° above and below the horizontal meridian). Essentially, you are testing the patient's peripheral fields against your own. You should be observing for defects that involve one-half of the visual field or one-quarter of the visual field and whether the defect is the same or different in both eyes. Test J. cranial nerve tested = __________________________________________ Ask the subject to dip a swab in quinine solution and apply it to the back of the tongue. Ask the subject to describe the taste Test K. cranial nerve tested = __________________________________________ Place your hands on your partner’s shoulders and ask him/her to raise them against your resistance. Place your hands on each side of your partner’s head and ask him/her to turn the head to each side against your resistance. Test L. cranial nerve tested = __________________________________________ DO NOT DO THIS TEST but see if you can figure out what nerve is involved. In this test, the posterior wall of the pharynx is touched with a tongue depressor. The normal response is contraction of pharyngeal muscles, and elevating the soft palate. The response is called the gag reflex, although gagging may or may not occur. Each side of the pharynx needs to be tested separately.

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

PART 2. REFLEXES Purpose: 1. 2. 3. 4.

To identify and describe the functions of the basic elements of the reflex arc. To explain why reflex testing is an important part of a physical examination. To describe and discuss several types of reflex activities observed in this laboratory. To identify the spinal nerves involved for each of the spinal reflexes investigated in the laboratory.

Clinical reflexes are automatic, predictable muscle movements brought on through known neural circuits when the appropriate receptor is stimulated. They can be used to assess neural development or health. Relexes are initiated when sensory receptors are stimulated and occur when an effector (eg. muscle) responds. SOMATIC REFLEXES Somatic reflexes terminate with the excitation of skeletal (voluntary) muscle. The stimulus for such a reflex may be initiated through excitation of receptors in the skin or mucosae, and are therefore called superficial reflexes, or through excitation of receptors in tendons or in the muscles themselves, and are therefore called deep reflexes. Somatic reflexes may involve turn around (integration) centers in the spinal cord and would therefore be called spinal reflexes or in the brain itself and would therefore be called cranial reflexes. Procedure: For each reflex tested, classify the location of the stimulus (superficial, deep) the location of integration (spinal, cranial) the type of effector excited (somatic, autonomic) Also, describe the observed responses for each reflex and name the muscles and neural pathways involved as much as possible. Work in pairs, taking turns performing each of the tests. 1. Patellar (knee jerk) reflex Have the subject seated on the laboratory bench with legs hanging free or with knees crossed. Locate the patellar ligament by palpation of the patella. The patellar ligament is located just below the kneecap. Tap the patellar ligament sharply with the reflex hammer to elicit the reflexive response. Test both knees and observe the responses. Response: ________________________________________________________

2. Achilles reflex (ankle-jerk response) Have the subject remove shoes. Ask the subject to dorsiflex the foot slightly to increase the tension of the gastrocnemius muscle. Sharply tap the calcaneal tendon and note the results. Response: ___________________________________________________________

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

3. Plantar reflex Have the subject remove a shoe and lie on the laboratory bench with knees slightly bent. The lateral side of the foot should rest on the bench. Draw the handle of the reflex hammer firmly down the lateral side of the exposed sole from the heel to the base of the great toe. Note the response. Response: __________________________________________________________ NOTE: This reflex is commonly tested in infants. Infants will typically show an extensor response. A baby's smaller toes will fan out, and their big toe will dorsiflex slowly. This is known as ‘Babinski’s sign’ and occurs because the corticospinal pathways that run from the brain down the spinal cord are not fully myelinated at this age, The extensor response disappears and gives way to the flexor response around 12-18 months of age. The Babinski’s sign in adults can indicate motor neuron damage to the spinal cord in the thoracic or lumbar region, or brain disease constituting damage to the corticospinal tract.

Complete the following table. Reflex

Receptor stimulated

Site of Integration

Effector

Superficial or Deep

Nerve

Patellar Reflex Achilles reflex Plantar reflex

VISCERAL (AUTONOMIC) REFLEXES Smooth muscle, cardiac muscle and glands are innervated by autonomic nerves. Innervation may be either sympathetic or parasympathetic and may result in excitation or inhibition of action. Autonomic reflexes may be cranial or spinal, superficial or deep. The pupillary reflex that was examined as an assessment of cranial nerve function is an visceral reflex.

Reflex

Receptor

Afferent nerve

Site of Integration

Effector

Efferent Nerve

Pupillary Reflex

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

PART 3: REACTION TIME Purpose: Unlike the other activities, this lab exercise does not test a simple reflex. Rather, this activity is designed to measure your response time to something that you see. The time required for a person to react to a stimulus depends on several factors: • • • • • • •

responsiveness of the sensory receptor nerve conduction velocity synaptic delay number of neurons and synapses involved distance nerve action potential must travel efficiency of neuromuscular transmission speed of muscle contraction

Procedure: 1. Working in groups of two students, get a ruler marked into cm 2. One partner will hold the ruler near the end (highest number) and let it hang down. 3.

Have the other student place his or her hand at the bottom of the ruler (over the 0 measurement) and have them ready to grab the ruler (they should place their fingers approximately 5 mm away from the ruler).

4.

Tell the other person that you will drop the ruler sometime within the next 5 seconds and that they are supposed to catch the ruler as fast as they can after it is dropped. Record the level (in centimeters) at which they catch the ruler. This represents the distance the ruler fell before it was caught. You can convert this distance into reaction time using a graph of data on the following page.

5.

Test the same person 4 times (vary the time of dropping the ruler within the 5 second "dropzone" so the other person cannot guess when you will drop the ruler). Calculate the average distance.

6.

Repeat the test using the test subject’s other hand (eg. if they are right handed, now evaluate distance using the left hand)

7.

Determine reaction time by looking up the average values on the graph generated from data on the following page.

Table 1. Distance ruler traveled in a test of reaction time distance ruler traveled (cm) 1 dominant hand

2

3

4

mean

reaction time (msec)

subject 1 subject 2

nondominant hand

subject 1 subject 2

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

8. Plot a “standard curve”. This is a reference curve generated using known values. An accurate standard curve can be used to extrapolate unknown values. Graph the known relationship between time and the distance a falling object travels using the following data set. Table 2. Relationship between distance an object falls and time

Distance(cm)

5

10

15

20

30

40

60

80

Time (msec)

100

140

170

200

240

285

350

405

9. The reaction times for the dominant and non-dominant hands can then be determined by looking up the mean distance that the ruler traveled (as calculated in table 1) and reading the reaction time off your standard curve above. Put these values in table 1.

10. Did reaction time seem to improve with ‘practice’ th (eg. was it less on the 4 trial than the first)?

Is this a reflex you are testing?

_______________

_______________

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

Table 4 Class reaction time data (msec) in the ruler-drop test Dominant hand

Non-dominant hand

mean

males

females

mean

11. What is the range of reaction times for the class? range = ________________ 12. Using the class data, calculate the mean reaction time for the dominant hand =

__________________

non-dominant hand =

__________________

What is the independent variable in this analysis? ________________________ 13. Based on your observations, does reaction time vary on the dominant vs non-dominant side? _______________ 13. Using the class data, calculate mean reaction time (dominant hand) for males and females Mean reaction time (males)

_________________

Mean reaction time (females)

_________________

What is the independent variable in this analysis? ___________________

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

14. Let’s assume you want to publish the results of this study. Graph the reaction time data in some meaningful way!

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CAMOSUN COLLEGE BIOLOGY 144 (2010) LABS

PART 4. ‘MUSCLE MEMORY’? Performance of a motor skill will improve with practice. Repetition of a motor skill (eg. throwing a javelin, doing a flip-turn in the pool, typing, piano playing, etc.) results in progressive improvement. The term ‘muscle memory’ is sometimes used to describe this effect. Muscle memory is fashioned over time through repetition of a given suite of motor skills until they become automatic. Even everyday activities such as brushing the teeth, combing the hair, or chewing food involve a complex series of neuromuscular events that must be learned. As these movements are reinforced neurologically through repetition, the nervous system ‘learns’ these fine and gross motor skills to the degree that one no longer needs to think about them, but merely to react and perform appropriately. Repeated use of a particular neural pathway is thought to reinforce neuromuscular communication through physiological changes involving the cerebellum and neuromuscular junctions. Read the abstract below which summarizes the results of a study which illustrates this principle. The Impact of Video Games on Training Surgeons in the 21st Century James C. Rosser, Jr, MD; Paul J. Lynch, MD; Laurie Cuddihy, MD; Douglas A. Gentile, PhD; Jonathan Klonsky, MD; Ronald Merrell, MD Arch Surg. 2007;142:181-186. Background Video games have become extensively integrated into popular culture. Anecdotal observations of young surgeons suggest that video game play contributes to performance excellence in laparoscopic surgery. Training benefits for surgeons who play video games should be quantifiable. Hypothesis There is a potential link between video game play and laparoscopic surgical skill and suturing. Design Cross-sectional analysis of the performance of surgical residents and attending physicians participating in the Rosser Top Gun Laparoscopic Skills and Suturing Program (Top Gun). Three different video game exercises were performed, and surveys were completed to assess past experience with video games and current level of play, and each subject's level of surgical training, number of laparoscopic cases performed, and number of years in medical practice. Setting Academic medical center and surgical training program. Participants Thirty-three residents and attending physicians participating in Top Gun from May 10 to August 24, 2002. Main Outcome Measures The primary outcome measures were compared between participants' laparoscopic skills and suturing capability, video game scores, and video game experience. Results Past video game play in excess of 3 h/wk correlated with 37% fewer errors (P