Reflexes

and

Special SensesSpecial Senses

REFLEXES

• Reflex

- a rapid, predictable and involuntary motor response to stimuli.

• Sources of Stimulus and Classification of Reflexes

A) internal environment

- Autonomic / Visceral reflex

B) external environment

- Somatic reflex

Reflex Arc Mechanism Components

• Receptor organ ( w/ Afferent / Sensory Neuron)

• Communication network (Interneurons / network (Interneurons / Association Neurons))

• Effector organ

(w/ Efferent / Motor Neuron)

Monosynaptic and Polysynaptic Reflex Arcs

Somatic: Spinal Stretch Reflexes

A. Patellar (or Knee-Jerk) Reflex:

Purpose: L2-L4 Assessment

Procedure:

B. Achilles (or Ankle-Jerk) Reflex:

Purpose: Assessment of sacral segments 1 and 2

Procedure:

Somatic: Spinal Stretch Reflexes

Results of Spinal (Stretch) Reflexes

• Hyperflaxia (exaggerated response) resulting

from damaged or diseased motor areas in the

CNS.

• Hypoflaxia (inhibited response) resulting from

the degeneration of the nerve pathways,

voluntary motor control, and other factors

A. Plantar Reflex:

Purpose: Assessment of corticospinal tract damage

Procedure:

Somatic: Superficial Cord Reflex

A. Corneal Reflex:

Purpose: Assessment of trigeminal nerve (cranial nerve V) or brain stem dysfunction

Procedure:

Somatic: Cranial Nerve Reflex

Autonomic Reflex: Pupillary ReflexesComponents:

a) Receptor: Retina of the eye

b) Afferent Fibers: Optic Nerve (Cranial nerve II)

c) Efferent Fibers: Oculomotor Nerve (Cranial nerve III)nerve III)

d) Effector: Smooth muscles of iris

A. Photopupillary (or Pupillary Light) Reflex:

Purpose: Assessment of optic nerve or brain stem

dysfunction

B. Consensual Reflex:

Purpose: Assessment of oculomotor nerve or brain

Autonomic : Pupillary Reflex

Purpose: Assessment of oculomotor nerve or brain

stem dysfunction

Procedure:

Results of Photopupillary and Consensual Reflex:

Autonomic : Pupillary Reflex

Special Senses

A. Visual Function Tests

Retina to Brain

retinaoptic nerve

lateral geniculate

nucleus

visual cortex

A.1. Blind Spot TestA.1. Blind Spot Test

Examples of Blind Spot Test Charts

Blind Spot Chart

A.2. Refraction,Visual Acuity and

Astigmatism TestsAstigmatism Tests

A.1.1. Near Point of Accommodation

• Definition:

• The ability of the eye to adjust its focus in

relation to changes in distance of an object

being viewed (less than 20 feet)being viewed (less than 20 feet)

• Procedure:

Principle of Near Point of Accommodation

Accommodation Test

Accommodation Test

• Interpretation of Results / Clinical Diagnosis:Normal vision – 10 cm; emmetropia

Abnormal:

a) Myopia (“Nearsightedness”) – failure of the parallel light rays to reach the retinal surface.

b) Hyperopia (“Farsightedness”) – the parallel light rays are b) Hyperopia (“Farsightedness”) – the parallel light rays are focused behind the retina.

Ageing Patients: presbyopia “old vison”

• Treatment:Myopia – concave lenses

Hyperopia – Convex lenses

A.1.2. Visual Acuity Test

• Definition:

• The clearness and sharpness of an image

• Procedure:• Procedure:

Visual Acuity Test

(Snellen’s Chart)

Visual Acuity Charts

Visual Acuity

• Interpretation of Results:Ratio is <1 = a person has greater than normal visual

acuity

Ratio is >1 = a person has less than normal visual acuity acuity

• Sample Problem: Patient 1: 20/20

Patient 2: 20/70

• Clinical Diagnosis:>1 Ratio (myopia = “nearsightedness”)

• Definition:

the abnormal curvature in some parts of the

lens and/or cornea

A.1.3. Astigmatism Test

• “Astigma” – not a point

• Procedure:

Astigmatism Test Chart

Astigmatism Test Chart

Test for Astigmatism

• Interpretation of Results:

Normal eyes – all radiating lines are equally dark and

distinct.

Astigmatic Eye – some lines are blurred or appear Astigmatic Eye – some lines are blurred or appear

less dark than the others

A.1.4. Color Blindness Test

Photoreceptors

• Rods – peripheral

region of retina; dim

light; black and white

• Cones – fovea; bright

light; colored; types

a) absorbs red

b) absorbs blue

c) absorbs green

Ishihara’s Color Blindness Test

• Purpose: test for deficiencies in the cones

(color photoreceptor cells)

Ischihara Test Kit

= collection of 38 plates filled with colored dots build the base of this test. The dots are colored in different shades of a color and a number or a line is hidden inside with different shades of an other color.other color.

= Distance from Subject:30 inches (75 cm)

Ishihara Test

Normal Color Vision Red-Green Color Blind

Left Right Left Right

Top 25 29 Top 25 Spots

Middle 45 56 Middle Spots 56

Bottom 6 8 Bottom Spots Spots

AMRWong

AMRWong

Interpretation of Results:

= Conditions:

a) Deuteranopia – absence of green-sensitive

receptors

b) Protanopia - absence of red-sensitive b) Protanopia - absence of red-sensitive

receptors

= These tests are never 100% accurate.

Color deficiency

AMRWong

Color deficiency

People who are "colorblind"

tend to be missing some of

the color-sensitive cones, so

these colors will appear

darker. Few people are

completely colorblind. For those that are color deficient, this is a

graph showing approximate proportions

of each type, based on a study of 5000

Swiss men who wanted to be pilots

BOYS VS. GIRLS

• Color deficiency is common in boys

Different books give different figures, from 5-8

% of boys, 1 boy in about 12-20, or an

average of one boy per classroom has some average of one boy per classroom has some

color deficiency, almost similar to the

percentage of people who are left-handed!

• Color deficiency is rare in girlsThe genes for color vision are on the X chromosome, and because females have 2 X chromosomes, if one is deficient, the other makes up for it. The result is that there are makes up for it. The result is that there are only about 1 in 200+ girls who have color deficiencies, or roughly only one girl in 16 classrooms

More common in Europeans:

It is inherited naturally through the mother,

who may pass on a defective X chromosome.

The actual ratios vary in different populations,

and one book reported that color deficiency is and one book reported that color deficiency is

more common in European stock, and much

less common in Asian and Native American.

(Perhaps northern dwellers during the ice ages

did not need color vision as much and lost it

during a mutation?)

A.1.5. Reflex Activity of the Intrinsic and Extrinsic Eye Musclesand Extrinsic Eye Muscles

1) Accommodation Pupillary Reflex2) Convergence Reflex

• Procedures:

B. Hearing and Equilibrium Tests

Hearing and Conduction Tests

B1. Rinne Test

• compares air conduction to bone-conduction hearing.

Results and Interpretation: • Normal - one will have greater air conduction than bone conduction and

therefore hear the vibration longer with the fork in the air. • Abnormal:

a) Conductive hearing impairment = Bone conduction is the same or greater than the air conduction.

b) Sensineuronal hearing loss = Vibration is heard substantially longer than usual in the air.

* It would also be prudent to perform an otoscopic examination of botheardrums to rule out a severe otitis media, perforation of the tympanicmembrane or even occlusion of the external auditory meatus, which allmay confuse the results of these tests. Furthermore, if hearing loss isnoted an audiogram is indicated to provide a baseline of hearing for future reference.

B2. Weber Test

• A test of lateralization –

Conductive and

Sensorineural Deafness

• Evaluates whether the • Evaluates whether the

sound remains centralized

(normal) or lateralized to

one side (indicative of some

degree of conductive or

sensorineural deafness)

Results and Observations

• The sound is heard in the center of the head or equally in both ears = equal hearing or equal loss of hearing.

Sensorineural deafness of L ear = tone is heard in R ear

Conduction deafness = tone is louder in ear with hearing lossConduction deafness = tone is louder in ear with hearing loss

NOTE: If the patient doesn't hear the vibration at all, attempt again, but press the butt harder on the patient's head.

B3. Romberg Test• Equilibrium is a result of:

1. visual confirmation of position, 2. non-visual confirmation of position (including proprioceptive and vestibular input)

3. a normally functioning 3. a normally functioning cerebellum.

Result: (+) result means that there is pathology in the proprioceptive pathway if a patient loses their balance after standing still with their eyes closed, but is able to maintain balance with their eyes open.

C. Chemical Senses: Taste and

SmellSmell

C.1. Sense of Taste

• Taste buds are found on the – Tongue

– Palate

– Lips– Throat– Throat

Sense of Smell (Olfaction)

Olfactory Epithelium and Bulb

C.1. Sense of Taste and Smell

• Factors affecting taste and smell:

• A) Presence/Absence of moisture

• B) Texture

• C) Olfactory stimulation• D) Temperature• D) Temperature