Lab 3: Cranial Nerves and Special Senses

Question 1

How important is the sense of smell to the sense of taste?

Answer 1

very, olfactory receptor are more sensitive to taste receptors

Question 2

Presbyopia

Answer 2

Is a natural age-related condition characterized by the diminished ability to focus on close objects -resulting from the loss of elasticity in the eyes lens (early to mid 40’s)

Question 3

Depth of focus test

Answer 3

Assesses the oculomotor nerves function. Illuminate your lab partners eyes with a pen light and observe the pupils constriction which is a response controlled by this nerve. A disparity in pupil size may suggest a lesion along the nerves pathway. Instruct your lab partner to fix their gaze on an object across the laboratory for two minutes then position a piece of printed material 15 centimeters from their face and note any changes in pupil size.

Question 4

Blind spot test

Answer 4

Identify the blind spot or the optic disc. Hold the figure approximately 45 centimeters from your eyes and close one eye. The X should be positioned in front of the open eye, focus on the X and move the figure slowly towards your face when the dot disappears it has focused on the blind spot

Question 5

Lens elasticity near the point of accomodation

Answer 5

Hold the pointer at arm’s length in front of you and focus on the tip. Move the pointer towards you until the image becomes distorted. Presbyopia occurs in the near point of vision increases beyond 9 inches.

Question 6

Visual Acuity

Answer 6

Use the eye chart. Test each eye individually and both with and without glasses if you wear them. If your visual acuity is less than one (20/40) then you are myopic. If visual acuity is greater than one (20/15) your vision is very good and better than average individual. 20/15 means you can see clearly at 20ft an object that an average person could only see clearly at 15ft.

Question 7

Astigmatism

Answer 7

Astigmatism refers to a mismatch in the curvature of the surface of the cornea and/or the lens. View the chart with one eye and then the other, focusing on the centre of the chart. If some of the lines appear blurred, you have at least some degree of astigmatism

Question 8

colour blindness or colour vision deficiency (CVD)

Answer 8

Use the charts provided to determine if you are colorblind. Remember cones are the visual cells that function in the perception of colour if you are colorblind for any of these, you are deficient in that type of cone

Question 9

3 colours that cones observe:

Answer 9

blue, green, red

Question 10

Depth Perception

Answer 10

Have your lab partner hold a test tube approximately arms length in front of you. With both eyes open insert a pencil into the test tube. Remove it and bring it back close to your body quickly close one eye and try again

Question 11

Eddison is an energetic 4-year-old, he is excited to be starting school and his mom decides to take him for an eye exam. The optometrist performs a test for depth perception and notices several deficits. A visual acuity test shows that acuity is low in the left eye. Addison is given an eye patch and is instructed to place the patch over his functioning eye. What condition do you think Edison has? Why is the patch placed over the functioning I and how will this help restore function?

Answer 11

Edison has lazy eye or ambiopia. This is when the eye and brain have poor communication. The most common cause of lazy eye is an imbalance in the muscles that position the eyes. The patch is placed over the functioning eye to give more stimulus and make the affected I work harder in order to force it to fix itself and form connections

Question 12

How important is binocular vision for depth perception?

Answer 12

Very. it allows us to perceive depth and relationships between objects. Each eye sees slightly different spatial information and transmits these differences to the brain. The brain then uses the discrepancies between the two eyes to judge distance and depth.

Question 13

Trochlear nerve H test

Answer 13

Without moving their head, have the participant draw a letter H shape three times with their finger and follow with their eyes. Then move a pen in the same H shape three times approximately 30 centimeters in front of the participant. A person’s inability to move the eye toward one part of the H may indicate a dysfunction of the extrinsic line muscles or the cranial nerve.

Question 14

Trigeminal Nerve sensory and motor evaluation

Answer 14

Motor aspect: contract the muscles in your jaw and notice the tension at your jaws angle. Sensory aspect: with the individual’s eyes shut, lightly brush different facial areas with a cotton swab and ask them to pinpoint the touched spot. A participant should be able to recognize when you contact the forehead, cheek and chin areas

Question 15

Abducens nerve

Answer 15

This nerve controls the muscle that allows the eye to abduct the lateral rectus. This nerve is assessed when observing the eyes follow the penlight around the field of vision.

Question 16

Bells Palsy

Answer 16

Condition characterized by sudden weakness or paralysis on one side of the face which may result in a drooping appearance, difficulty making facial expressions and other disruptions to normal facial function. This condition is caused by damage to the 7th cranial nerve the facial nerve, which is responsible for controlling muscles of facial expression.

Question 17

Vestibulocochlear Rinne Test

Answer 17

To assess the cochlear portion activate the tuning fork by hitting it on your hand. Move the fork so the end touches the mastoid process behind your ear, your lab partner should tell you when they can no longer hear the buzz sound. Then move the fork through the air outside of the external auditory meatus. With a functioning vestibulocochlear nerve the participant should be able to hear the second part after Step 2. If they do not there may be conductive hearing loss. To assess the vestibular portion place an object on the floor and have the participant bent at the waist and pick them up, did they have difficulty?
Conductive hearing loss = air conduction is better than bone conduction.

Question 18

2 types of hearing loss:

Answer 18

Hearing loss can either be conductive or sensorineural. Conductive hearing loss is a failure in the efficient conduction of sound waves through the outer ear, tympanic membrane, or middle ears. Sensorineural hearing loss is a type of hearing loss in which the root cause lies in the vestibulocochlear nerve, the inner ear, or central processing centres of the brain

Question 19

Weber Test for Conductive or Sensorineural Deafness

Answer 19

Strike a tuning fork and place the handle medially on the participants head. Is the tone heard equally in both ears? If the tone is not heard in one ear then there is sensorineural defect in the non hearing ear. If there is conductive deafness, the sound will be louder in the ear with the defect.

Question 20

Testing glossopharyngeal and vagus nerves

Answer 20

Examining the gag reflex. A reflex that developed as a method to prevent swallowing foreign objects and prevent choking.

Question 21

accessory nerve test

Answer 21

Raise your shoulders and gently resist head rotation. Response should be equal on both sides.

Question 22

Hypoglossal nerve

Answer 22

Stick out your tongue. Can you move it side to side? Is your speech clear or slurred?

Question 23

Why is the cows cornea cloudy?

Answer 23

The eyes become cloudy after death because of the lack of oxygen and circulating blood to them.

Question 24

Once incision into cornea is made, what fluid leaks out and what is its function?

Answer 24

aqueous humor - keep proper ocular pressure (eye pressure) in your eye. The pressure is maintained by having the same amount of fluid come in as the amount of fluid leaving the front of your eye.

Question 25

Why do cows, and other nocturnal and prey animals have a tapetum lucidum? What is its purpose?

Answer 25

reflects/absorbs light for better vision in the dark. Found behind the retina

Question 26

why is the optic disk referred to as the blind spot?

Answer 26

it doesn’t contain any visual receptors, like rods or cones, which are responsible for detecting light

Question 27

5 components of a reflex?

Answer 27

sensory receptor, sensory neuron, interneuron (only polysynaptic reflexes), motor neuron, effector organ

Question 28

There are 2 types of reflexes, somatic and automic. What are they and how are they different?

Answer 28

somatic - activation of skeletal muscles, move body from painful stimulus, keep body from falling/injury
autonomic - no control over. (BP, Co2 level, heart rate)

Question 29

Difference between 2 types of reflex arcs? monosynaptic and polysynaptic

Answer 29

monosynaptic: 1 synapse, motor neuron directly synapses w/sensory neuron
polysynaptic: not direct, interneuron synapses w/sensory neuron then interneuron w/motor neuron (multiple synapses)

Question 30

During patellar tendon reflex test (tap patellar ligament) , what occurs with the knee? What level of spinal cord is tested? What factors will affect the reflex response? Will mental distraction affect the strength of spinal reflex?

Answer 30

extension occurs

lumbar (L2 to L4), femoral nerve

motor neuron damage, fatigues muscle (after sports), conduction rates (weak = weak response)

if they just completed a marathon, they will have a weak response

no, signal goes through spinal cord,, not head (brain)

Question 31

Deep Tendon Reflex Test (tap triceps tendon to cause contraction): What occurs with the elbow - does it go through flexion or extension? What level of spinal cord are you testing?

Answer 31

extension

C7 to C8

Question 32

Withdrawal reflex

Answer 32

The function is to remove a limb from a painful stimulus. This reflex is Polysynaptic, the sensory receptors are pain receptors. Action potential travels along the sensory neurons, synapse with interneuron and then with motor neuron. The motor neuron stimulates muscles that remove the limb from the painful stimulus

Question 33

What are 2 diff types of equilibrium? How are they different?

Answer 33

Static: position of head relative to gravity
Dynamic: movement of head
-both elevated

Question 34

Why do you get sick to your stomach when sea sick?

Answer 34

fluid shifts, disparity in what body detects and what you see in front of you.