Physiology ๐ซ Flashcards
what are combined somatic sensations?
Both superficial & Deep
- stereognosis
- Vibration senses
Test for crude touch
Cotton wool test
Pathway for pressure sensation
Dorsal column medial leminscal system
A side information: Minimal distance in lips is 2 mm
where are receptors for vibration sense present?
They are present in subcutaneous tissue in the muscle fibers
what are types of pain?
- Cutaneous
- Deep
- Visceral
Definition of cutaneous pain
- Pain sensation results from stimulation of pain receptors in skin
Test for cutaneous pain
Pin prick test
Definition of Deep pain
- Pain sensation results from stimulation of pain receptors in deep structures
- Like tendon, muscle, joint, ligament & Periosteum
Test for Deep pain
- squeeze or pinch the muscle of calf or biceps and ask the patient to report as soon as sensation becomes painful.
Definition of Visceral pain
- then sensation results from stimulation of pain receptors in viscera
Type of Pacinian corpuscle receptors
(mechano-receptors present in the skin, deep tissues involved in the sensations of touch, pressure and vibrations).
Compare between Rapidly adapting receptors & Slowly adapting receptors in terms of:
- Definition
- Example
- Other name
- Physiological significance
Classification of sensation
General:
- Arises from widely distributed receptors all over the body.
Special:
- vision
- taste
- smell
- hearing
- Sense of equilibrium.
Emotional:
- fear
- anxiety
- sadness
Com pare between Somatic sensation, Visceral sensation & Sensation organ in terms of:
- Arise from
- Crried by
- Examples
what is the definition of Touch sensation?
- It is a sense or feeling produced by application of light mechanical pressure to the skin
what happens if the intensity of touch increases?
if the intensity of the stimulus is increased, it is changing into pressure sense
what are the types of touch?
a) Fine touch.
b) Crude touch.
Definition of Crude touch
A type of touch sensation which is poorly localized
Stimulus in case of Crude touch
Diffuses ill defined object, Touching the skin with a piece of cotton or the touch of clothes.
Receptors of Crude touch
- Free nerve endings & hair end organs or follicle receptors โlocated in the hair folliclesโ
Afferents of Crude touch
- A-ฮด nerve fibers โ5-30 meter/secondโ.
- C fibers โ0.5-2 meter/secondโ.
Pathways of Crude touch
Pathway from the body:
- Ventro spino thalamic tract by A delta fibers
- Spino reticular tract by C fibers
Pathway from the face:
- Trigeminal pathway
whose transmission is faster, crude or fine touch?
The transmission of crude-touch is much slower than fine touch
Spatial arrangment of Crude touch
the spatial arrangement of the fibers in the pathway is poor
Does Crude touch inform the CNS accurately?
the impulses not inform the C.N.S accurately about the size & site of the crude-touch stimulus
Definition of Fine touch
It is a type of touch which informs us accurately about the shape, form and site of the tactile stimulus.
Stimulus of Fine touch
Well localized object to the skin as tip of pencil, head of a pin, teeth of comb
Receprors of Fine touch
- Meissnerโs corpuscles (rapidly adapting).
- Merkelโs discs (slowly adapting)
Afferents of Fine touch
A-beta rapidly conducting nerve fibers (30-70 meters/second).
Pathway of Fine touch
Fine touch impulses are transmitted by A-beta nerve fibers which travel through the Dorsal column โ medial lemniscal system (Gracil & Cuneate tracts).
Types of Fine touch
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
Definition of Pressure sensation
It is a sensation produced by the application of heavy mechanical stimuli to the skin (which can cause deformation of the different skin layers).
Receptors of Pressure sensation
a) Rapidly adapting receptors (Pacinian corpuscles).
b) Slowly adapting receptors (Ruffini multi-branched nerve endings); present in the deeper layers of the skin and responsible for the continuous information of the C.N.S about the pressure stimuli which play a role in the orientation of body position.
Afferents of Pressure sensation
as fine touch. (G & C)
Pathway of Pressure sensation
as fine touch. (G & C)
Types of Pressure sensation
Deep pressure sense:
- Discriminate between different weights without lifting them
Muscle tension sense:
- Discriminate between different weights with lifting them
significance of Pressure sensation
- Maintain posture
- Diffrentiate between different weights
Defintion of Vibration sensation
- It is a sensation of rhythmic pressure changes produced by the rapid repetitive stimulation of certain mechanoreceptors.
Stimulus of Vibration sensation
It can be produced by placing the base of vibrating tuning fork on the skin over bony prominence
Receptors of Vibration sensation
i)Meissnerโs corpuscles: can respond to frequencies to frequencies up to 200 cycles/second.
ii)Pacinian corpuscles: can respond to frequencies to frequencies up to 700 cycles/second.
Afferents of Vibration sensation
as fine touch (G &C)
Pathway of Vibration sensation
as fine touch (G &C)
Definition of Proprioceptive sensation
Is a sense that allows us to know the position and movement of every part of the body specially joints and limbs.
Receptors of Proprioceptive sensation
1) Muscle proprioceptors.
2) Joint proprioceptors.
Pathway of Proprioceptive sensation
- At conscious level
- At subconscious level
Types of Proprioceptive sensation
- Sense of position.
- Sense of movement.
- Muscle-tension sense.
- Deep pressure sense.
what are the types of Fine touch?
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
what is the definition of Tactile localization (topognosis)?
- It is the ability of the person with his eyes closed to perceive and determine accurately the site of a single point of fine touch.
Definition of Tactile discrimination (2 point discrimination)
Its the ability of the person or central nervous system to discriminate 2 points of fine touch applied simultaneously to the skin with the personโs eyes closed provided that the distance between them is greater than the minimal distance.
what is Minimal (Threshold) distance?
it is the distance between 2 points of fine touch below it the points are felt as a single point whereas at or above it the 2 points are felt as separate points
what does Minimal (Threshold) distance equal?
It equals 1 mm at tip of tongue, 3 mm at tip of fingers, 70 mm at the back.
where is Tactile discrimination more accurate? and why?
- On the extremities than on the proximal parts due to:
- Greater number of touch receptors, and subsequently a greater number of afferents
- Little convergence of afferents.
- Wide area of cortical representation and so good analysis and interpretation of sensory information.
what is the definition of Stereognosis?
Is the ability of the person with his eyes closed to recognize a familiar object by touching it e.g. recognition of a key, a pen or a coin.
what is the definition of Determination of texture of materials?
- Is the ability of the person with his eyes closed to recognize the nature of an object/textiles e.g. glasses and wood
which type of sense is Sense of position?
static sense
what does sense of position represent?
conscious orientation of the relative position of the different parts of the body to each other.
which type of sense is Sense of movement?
dynamic sense
what does Sense of movement represent?
means conscious orientation of the changes in the relative position of the different parts of the body to each other as regard, onset, termination, direction and the rate or velocity of this change
what are receptors of proprioception?
Compare between pathway of proprioception at conscious & subconscious level in terms of:
- Center
- Function
- Pathway
Definition of Thermal sensation
Is the sensation that enables us to detect temperature change, it includes warm and cold sensation.
Distribution of Cutaneous thermo receptors
- Number of cold receptors is greater than the number of warm receptors by about 3- 10 times.
- They are distributed in a punctuate fashion where, certain areas of skin contain warm receptors only and others contain cold receptors only with thermally insensitive areas in between.
what are the types of thermo-receptors?
- External (peripheral) thermoreceptors
- Internal (central) thermoreceptors
Compare between External (Peripheral) thermo-receptors and internal (Central) thermo-receptors in terms of:
- Types
- Location
- Detect
Compare between Warm & Cold Receptors in terms of:
- Morphology
- Number
- Afferent fiber
- Discharge impulse between
- Maximum discharge
Thermo-receptors at zero degree
all receptors stop discharge and this is one of the methods of anaesthesia.
Thermo-receptors at 45 degrees
the person feels โParadoxical cold sensationโ due to a brisk discharge from the cold receptors โParadoxical cold sensationsโ.
Thermo-receptors if temperature is less than 10 degrees
- Stimulate cold pain receptors
Thermo-receptors if temperature is more than 45 degrees
Stimulate warm pain receptors
what is the mechanism of stimulation of thermo-receptors?
what is the type of thermo-receptors?
Biphasic but mainly slowly adapting receptors
Adaptation of thermo receptors
Neural pathway of thermal sensation
Definition of Pain Sensation (Nociceptors)
- Unpleasant sensory and emotional experience associated with actual tissue damage.
Physiological significance of Pain Sensation
- Protective sense that direct the person to get rid of injurious stimulus.
what are the characters of pain receptors?
what is the type of pain receptors?
- They are morphologically one type โ free nerve endings.
- They are slowly adapting and even non-adapting receptors.
Specifity of pain receptors
- Highly specific โ respond to tissue damage & classified
according to type of painful stimuli into:
a. Mechanical pain receptorโ to mechanical stimulus.
b. Chemical pain receptorโ to chemical stimuli
c. Thermal pain receptor โ respond to excess temperature โ (<10ยฐC &>45ยฐC)
d. Polymodal pain receptor โ respond to all above painful stimuli.
Threshold of pain receptors
high threshold โ need strong stimulus that cause tissue damage.
Distribution of pain receptors
Widely distributed all over the body:
a. More abundant in the skin.
b. Present in deeper structures (muscles - joints - periosteum).
c. Viscera contains a smaller number of pain receptors and even this few numbers are concentrated in serous membranes e.g. peritoneum, pleura, pericardium & meninges of the brain.
d. Absent from: Liver, lung, brain & bone
when do diseases that affect the viscera start causing pain?
- The diseases affecting the parenchyma of organs, may not produce pain early, but lateral when they invade the serous covering they cause severe pain.
Definition of Pain Threshold
The lowest intensity of injurious agent needed to stimulate the pain receptors and produced pain sensation.
what are the methods of determination of the pain threshold?
- By pricking the skin with a pin.
- By compressing the skin against hard objects.
- Thermal method โmore accurateโโ by applying to skin to a thermostatically controlled metallic rod (Most of individuals begin to feel pain at 45ยฐC and all feel pain at 47 C and this is known as thermal threshold for pain receptors stimulation).
Feeling of pain in different people
- Most people feel pain at similar points but differ in their reaction to pain.
- Pain threshold is not the same in all individuals.
what is pain classified into?
what is the aim of sensory examination?
- To assess the integrity of sensory pathways
- To localize the site of lesion in central nervous system
steps of sensory examination
- First teach the patient about the test (in his own language), then perform the test.
- Should done quickly because patient get tired easily.
- Patient eyes should be closed to eliminate the effect of vision on sensation.
- Every part of the body should be examined systematically, so as not to miss one single dermatome i.e. done dermatomal.
- Compare both sides of the body (similar parts).
- Examine limb by starting distally and move proximally.
- Outline the boundaries of areas of sensory loss.
- In all tests, move from areas of sensory loss to areas of normal sensations since it is easier to the patient to detect when a sensation becomes increased than when it diminishes.
why should Sensory examination be done quickly?
- because patient get tired easily
why should the patient eyes be closed during Sensory examination?
to eliminate the effect of vision on sensation.
why should you move from areas of sensory loss to areas of normal sensation during Sensory examination?
- since it is easier to the patient to detect when a sensation becomes increased than when it diminishes
Steps of cotton wool test
- Ask the patient to close his eye
- Touch the skin with a small piece of cotton wool or soft brush or tissue paper
- Ask him to say yes every time he is touched
- Avoid regularly timed stimuli so that the patient does not anticipate the test
- Examine each dermatome
- Avoid dragging or moving the cotton wool across the skin or tickling the patient because moving the cotton wool will stimulate tickle sensation
- Outline the borders of any abnormal area of sensations
- Compare sensation of touch in a hairy areas and non-hairy areas of the skin
why you should avoid regulary timed stimuli during cotton wool test?
- so that the patient does not anticipate the test
why you should avoid dragging or moving the cotton wool across the skin during cotton wool test?
- because moving the cotton wool will stimulate tickle sensation
Test for tactile localization (Topognosis)
- apply gently head of pin to the skin ( bilateral, dermatomal, distal to proximal).
Test for tactile discrimination (2 point discrimination)
- Apply the two points of a blunt compass simultaneously to the skin and record the least distance between the two points which gives a sensation of two points being touched and not one.
- Compare tactile discrimination at the finger tips with that of the hand, forearm and arm.
Test for stereognosis
- Put any familiar object in the hand of the subject e.g. coin, key or pen)
- With eyes closed ask him to identify it
- Repeat the experiment by changing the object
steps of testing pressure sensation
- Place the hand of the subject on the table with the palm upwards.
- Using the weights provided, investigate the least difference in weight which can be appreciated by the subject e.g. first apply the 50 grams weight and then the 60 grams weight.
- Ask the subject which weight is heavier? If the difference is appreciated, try the 50 and 55 gm. weights and so on.
- Check the test by putting down the same weight for comparison.
- Ask the subject to compare different weights while his hand is unsupported to test muscle tension.
steps for testing vibration sensation
- Ask the patient to close his eyes
- Apply the end of a tuning fork (128 Hz) to the superficial bones in the forearm, leg or to any part of the body e.g. toe tips, medial or lateral malleoli, tibial tuberosity, lower end of radius and ulna, olecranon, and clavicle
- Check that patient reports feeling of vibration or thrill
- Ask the patient to identify as soon as the tuning fork stops
- Compare left and right sides
steps of testing Sense of position
- The subjectโs big toe or thumb is flexed or extended with eyes closed
- Then the subject is asked about the position of the joints or to place his other limb in a similar position.
Steps of testing Sense of joint movement
- The subjectโs big toe is passively moved with eyes closed
- He is asked about the feeling of movement, its direction and extent.
steps in testing thermal sensation
- Touch the skin of different regions of the arm and face with a test tube containing water at 20oC (cold) and at 42oC (warm).
- Prepare two test tubes one containing water at 36oC and the other at 38oC and test whether the subject can distinguish which is colder or warmer, when they are applied to the skin once simultaneously and another time successively.
- Investigate the least difference in temperature which can be recognized. Compare this threshold difference in various regions of the skin.
Definition of Reflex Action
- It is an automatic (involuntary) specific response of an organ caused by an adequate sensory stimulus.
Pathway of Reflex Action
1) Stimulus
(2) Receptor Sensory neuron
(3) CNS (spinal cord) Motor neuron
(4) Effector
(5) Response
Physiological significance of reflexes
- Its function differs from one reflex to another
e.g. flexion withdrawal reflex is a protective reflex.
Clinical significance of reflexes
- It tests the integrity of the pathway (to test for normal CNS function).
- Localization of the site of the lesion.
Classification of reflexes
- Systemic/General Reflexes
- Local Reflexes
Centre of Systemic/General Reflexes
Systemic/General Reflexes:
- Their centers inside CNS
centre of Local Reflexes
Local Reflexes:
- Their centers outside CNS
Types of General/Systemic reflexes
- Conditioned Reflexes
- Unconditioned Reflexes
centres of Conditioned & Unconditioned Reflexes
Conditioned Reflexes:
- Their centers present in cerebral cortex
Unconditioned Reflexes:
- Their centers present in CNS outside cerebral
what are Spinal Reflexes?
- They are reflexes whose centers are present in the spinal cord
Classification of Spinal Reflexes
They are classified into 3 types:
- Superficial spinal
- Deep spinal
- Visceral spinal
Definition of Superficial spinal reflexes
- The receptors of these reflexes are present on the body surface e.g. skin.
Examples of Superficial spinal reflexes
- Abdominal reflex.
- Planter reflex.
Definition of Deep spinal reflexes
- The receptors of these reflexes are present in deep structures e.g. ms, bone and joints.
Examples of Deep spinal reflexes
- muscle stretch reflex or tendon jerk
Definition of Visceral spinal reflexes
- The receptors of these reflexes are present in visceral organs.
Examples of Visceral spinal reflexes
- Micturition reflex (its center is S2,3,4)
- Defecation reflex (its center is S2,3,4)
- Erection reflex (its center is S2,3)
Definition of Plantar Reflex
- Scratching the sole of the foot along its lateral margin from the heel toward the toes causes a plantar flexion of all the toes.
Center of Plantar Reflex
S1 and S2
procedure of Plantar Reflex
- Raise the heel of the subject with your left hand.
- Then scratch the outer edge of the sole of the foot with your nail or your key.
- The big toe and the other toes show plantar flexion.
What is Babinski sign?
Scratching the sole of the foot along its lateral margin from the heal toward the toes causes:
- Dorsiflexion of the big toe
- Separation (or fanning out) of the other four toes
what causes Dorsiflexion of the big toe and/or
Separation (or fanning out) of the other four toes?
Dorsiflexion of the big toe:
- due to pyramidal tract lesion
Separation (or fanning out) of the other four toes:
- due to extrapyramidal tract lesion
Normal Plantar Response and Babinski Sign
PPT
Causes of Babinski sign
Physiological and pathological causes
Physiological Causes of Babinski sign
Newly born infants:
- during the 1st few months of their life due to incomplete myelination of pyramidal tract.
Normal adults:
- during deep sleep or during general anesthesia.
Pathological Causes of Babinski sign
- UMNL.
- When the cerebral cortical function is depressed as in coma.
Definition of Abdominal reflex
- Stroke the skin over the abdomen outward toward the umbilicus to the upper and lower abdominal quadrants leads to contraction of underlying muscles. This is indicated by the movement of the umbilicus.
Center of Abdominal reflex
- T7 to T12 segments of the spinal cord
Procedure of Abdominal reflex
- Patient should be supine and relaxed.
- Using a stick or key or head of a pin a brisk but light stroke is given in medial directions across the upper and lower quadrants of the abdomen from outward toward the umbilicus
- The normal response is the contraction of the underlying muscle, with the umbilicus moving laterally and up or down depending on the quadrant tested.
Significance of Abdominal reflex
- This reflex is lost in pyramidal tract lesion or UMNL
- It is non-specific, because it is lost also in abdominal surgery, repeated pregnancy and age.
Definition of Tendon Jerk
- It is a brief contraction of a skeletal ms to sudden stretch produced by tapping its tendon sharply & strongly (using a reflex hammer).
Mechanism of tendon jerk
- It is a dynamic type the stretch reflex.
Receptor of Tendon Jerk
Nuclear bag fibers of muscle spindle
Afferent of Tendon Jerk
1ry endings.
Centre of Tendon Jerk
ฮฑ-MNs of the stretched skeletal muscle
Efferent of Tendon Jerk
Thick myelinated type Aฮฑ nerve fiber
Response in Tendon Jerk
brief contraction followed by rapid relaxation.
Examples of Tendon Jerk
- Knee jerk
- Ankle jerk
- Biceps jerk
- Triceps jerk
Procedure of Tendon Jerk
1) The muscle group to be tested must be exposed.
2) The muscle group to be tested must be in a neutral position (i.e. neither stretched nor contracted) (= semiflexed & in dependent position).
3) The tendon attached to the muscle(s) which is/are to be tested must be clearly identified.
4) Strike the tendon with a single, brisk, stroke.
Center of Knee jerk
L2,3,4
Tendon stimulated in Knee jerk
- Tapping on the patellar tendon
Movemnet in Knee jerk
- Extension of the knee
Muscle contraction in Knee jerk
- Quadriceps femoris
Center of Ankle jerk
- S1-2
Muscle tendon in Ankle jerk
- Tapping on tendoachilles
Movement in Ankle jerk
Plantar flexion.
Contraction of muscle in Ankle jerk
Gastrocnemius and soleus
Center of Biceps jerk
C5-6
Muscle tendon in Biceps jerk
Tapping on the biceps tendon.
Movement in Biceps jerk
Flexion of the forearm.
Contaction of muscle in Biceps jerk
Biceps muscle.
Center in Triceps jerk
C 6-7
Muscle tendon in Triceps jerk
Tapping on the triceps tendon directly.
Movement in Triceps jerk
Extension of the forearm.
Contraction of muscle in Triceps jerk
Triceps muscle.
Summary of tendon jerks
PPT
How could we reinforce tendon jerk?
- The response of the tendon jerks can be reinforced by facilitating the spinal centers.
- This can be done by either:
1. Jendrassikโs maneuver
2. Distracting patientโs attention
Jendrassikโs maneuver
- ask the patient to hook his fingers or to clench his teeth โ send signals from the contracted ms which stimulating ฮณ-MNs.
Distracting patientโs attention
- prevents any voluntary inhibition of the reflex.
Clinical Significance of Tendon Jerk
- Localization of spinal cord lesions
- Assessment of the ms tone
- Assessment of the integrity of pathway of stretch reflex
- Assessment of the state of Supraspinal centers
Localization of spinal cord lesions by tendn jerk
- Loss of TJ means the lesion in its center e.g. ankle jerk is lost in sacral region lesion.
Assessment of the ms tone by tendon jerk
- In hyperreflexia (exaggerated tendon jerks)โ hypertonia ( โms tone).
- In hyporeflexia (โed tendon jerks)โ hypotonia (โms tone).
- In areflexia (lost tendon jerks)โ atonia ( lost ms tone).
Assessment of the integrity of pathway of stretch reflex by tendon jerk
PPT
Assessment of the state of Supraspinal centers by tendon jerk
PPT
what are visual reflesex?
- Corneal reflex
- Pupillary light reflex
- Accommodation reflex
Definition of Corneal Reflex
- It is reflex closure of both eyes on touching the cornea of one eye with any foreign body. e.g. piece of cotton results in reflex blinking of both eyes.
Pathway of corneal reflex
PPT
Significance of corneal reflex
Physiological:
- It is protective that protect cornea from foreign bodies.
Medical or clinical:
- It is used to detect the pathway integrity and to test for functions of trigeminal and facial nerves.
Procedure of corneal reflex
- With a piece of soft cotton, touch the cornea.
- The response is reflex closure of both eye lids.
Definition of Pupillary Light Reflex
- Exposure of one eye to light leads to reflex constriction of that eye (direct light reflex) and also the other eye (indirect or consensual light reflex).
Center of Pupillary Light Reflex
- pretectal nucleus of the same side
what explains The consensual light reflex?
- The consensual light reflex is explained by the partial decussation at the optic chiasma and the bilateral innervation of the edinger westphal nuclei form each pretectal nucleus
Procedure of Pupillary Light Reflex
- Examine the diameter of the 2 pupils of your colleague.
- Ask him to close his eyes.
- After 5 min direct the bright light of a torch to one eye.
- Observe the changes in diameter of pupils of both eyes.
- Repeat the experiment after instillation of atropine in conjunctival sac.
- Record your finding and write your comment.
Significance of Pupillary Light Reflex
Physiologically:
- it is a protective reflex controls the amount of light entering the eye.
Medically:
- it is important for diagnosis and localization of lesions in the pathway of the reflex.
what causes Argyll-Robertson Pupil?
- due to lesion in the pretectal nucleus of the midbrain as in syphilis/or syringomyelia of the aqueduct of Sylvius which destroy the crossing fibers.
Description of Argyll-Robertson Pupil
- It is a condition in which the pupil does not respond to light reflex but responds to accommodation reflex
definition of Accommodation Reflex (near reflex)
- It is the process in which the optical system of the eye is adjusted to see the near objects.
Changes occuring in the eye during Accommodation Reflex (near reflex)
- Miosis of both eyes.
- Increase lens convexity of both eyes.
- Medial convergence of both eyes.
Definition of Visual Acuity
- It is the ability of the eye to see the fine details of the object or to discriminate between 2 points in the visual field.
Principle of measurement of visual acuity
- The eye can discriminate between 2 points when the 2 points stimulate 2 cones separated by unstimulated one.
- In this condition the 2 points form a visual angle of about 1 min (1/60 of degree).
Methods of Measurement of Visual Acuity
There are many clinical methods for stating visual acuity:
- Charts
- Counting fingers
- Hand movement
- Perception of light
Clinical Charts of visaul acuity mesaurment
- Landoltโs C charts
- Snellenโs letter charts
- Emarah arabic chart
Check PPT
Landoltโs Chart
- Consists of 7 rows of incomplete circles with the openings of the circles in different directions.
- The opening of the biggest circle makes a visual angle of 1 min at a distance of 60 m.
- The openings in the lower rows of circles make the same angle at distances of 36 m, 24m, 18m, 12m, 9m and 6 meters respectively
Steps of testing visual acuity by Landoltโs C charts
- Good illumination for chart.
- The chart is placed at a distance of 6 meters from the tested person.
- He is asked to see the site of opening of each circle.
- Start with big circle then move downward to small ones.
- If he see the last row at 6 meters, his VA 6/6.
- If he cannot see the last row, but he can see row above it, his VA IS 6/9, then 6/12, 6/18. 6/24, 6/36, and 6/60.
Clinical Expression of Visual Acuity
PPT
what are other methods to measure visaul acuity?
Counting fingers:
- Ability to count fingers at a given distance.
Hand movements:
- Ability to distinguish a hand if it is moving or not in front of the face of the patient.
Perception of light:
- Ability to distinguish if the eye can perceive any light.(If no perception of light = totally blind)
what is Field of vision?
- It is the part of environment around us which can be seen without moving the eye.
Types of Field of vision
- Monocular: field of one eye only. Objects in this field form images on one retina.
- Binocular: fields of both eyes together.
Objects in this field form images on one or both retinae.
Methods of Measurement of Field of vision
- Confrontation test
- Perimeter
Describe Confrontation test
- It is a rough clinical test.
- The patientโs field is compared with that of the examiner (who is supposed to be normal).
Perimeter
- It maps the visual field and detects any defect in the visual field.
Importance of determination of visual field
- Help in localization of the sites of lesions in the visual pathway.
Check PPT for lesion in eye VVVVIIIIPPPP
Definition of Colour Vision
- It is the ability of the eye to perceive the different types and characters of colours.
Mechanism of Colour Vision
TrichromaticTheory (Young- Helmholtz Theory )
Definition of Colour blindness
It is inability of the subject to discriminate between colours which normal person can recognize.
Nature of Colour blindness
commonly inherited as a recessive X- linked chromosome).
what does colour blindess affect more?
Males
Types of colour blindness
- The suffix โ-anomalyโ denotes color weakness and -anopiaโ color blindness.
- The prefixes โprot-=red,โ โdeuter-=green,โ and โtrit-= blueโ.
1) Anomalous trichromate
2) Dichromats
3) Monochromats
Symptoms of Anomalous trichromate
- These patients have all three cone systems, but one may be weak.
- So they may have tritanomaly, deuteranomaly, or protanomaly.
Symptoms of Dichromats
- These are individuals with only two cone systems.
- They may have protanopia, deuteranopia, or tritanopia.
- Dichromats can match their color spectrum by mixing only two primary colors.
Symptoms of Monochromats
- It is a rare condition where only one cone system is present.
- Monochromats match their colour spectrum by varying the intensity of only one.
Tests of colour vision
- Ishihara chart
- Wool classification & Matching test
- Edrige green lantern test
Ishihara chart
PPT
what is Audition or hearing?
- sense that allows us to communicate and hence interact with other organisms throughout the world.
what is Hearing?
- ability to perceive certain pressure vibrations in the air and interpret them as sound.
Types of sound conduction
Air & Bone conduction
Definition of Air conduction
Is the normal way of conduction of sound waves from air to inner ear through tympanic membrane and bony ossicles
Definition of Bone conduction
- is the conduction of sound to the inner ear through the bones of the skull.
- In bone conduction, a vibrating device is placed on the mastoid process. The vibration over the bone is directly conducted to the cochlea.
Definition of Deafness
- Deafness means partial or complete hearing loss.
- Partial loss of hearing is often called hearing loss rather than deafness.
- Deafness can occur in one or both ears.
- It is manifested by decrease in the acuity of hearing or increase in the threshold of hearing.
Types of deafness
- Conductive deafness
- Sensorineural deafness
Causes of Conductive deafness
- It results from interference with the proper conduction and amplification of sound waves through the external and middle ears.
Causes of Sensorineural deafness
- It results from a lesion in the receptive part of the inner ear or the auditory pathway (basilar membrane, organ of Corti, auditory nerve or auditory cortex).
Causes of Conductive Deafness
(In details)
Causes in the external ear:
- Obstruction of the ext. meatus by accumulation of wax, foreign body, inflammation or tumour.
Causes in the middle ear:
- Tympanic membrane perforation
- Middle ear inflammation (acute and chronic otitis media).
- Bony ossicles otosclerosis
- Eustachian tube obstruction as in common cold.
Characters of Conductive Deafness
- Air conduction is more affected than bone conduction
- All frequencies are affected equally.
Causes of Sensorineural Deafness
(In detail)
Damage of hair cells due to:
- Prolonged use of antibiotics e.g. streptomycin.
- Prolonged exposure to high intensity sounds as in airports and noisy factories.
- Meneierโs disease
- Damage of the cochlear nerve or auditory cortex due to severe head injuries or tumors.
Characters of Sensorineural Deafness
- Both air conduction and bone conduction are affected equally
- Some frequencies are affected more.
what are hearing tests?
Whispered voice test:
- detect the presence of hearing impairment.
Tuning Fork tests
- differentiate between types of deafness
Pure Tone Audiometery (PTA)
- Detect the presence of deafness
- Differentiate between types
- Determine the degree of hearing loss and speech discrimination
Procedure of Whispered voice test
- The normal person can hear whisper voice at 6 meters and sound of normal conversation up to 12meters.
- When the person needs shorter distances to hear theses sounds โ presence of hearing loss or deafness
Frequencies of tuning fork? and which is the most common?
- The frequency of fork maybe 128, 256, 512, 1024, 2048.
- The most common frequency used is 512 Hz
what are tuning fork tests?
- Weber test
- Rinnie test
- Schwabach test
Principle of Weberโs test
- It can detect unilateral (one-sided) conductive hearing loss and unilateral sensorineural hearing loss
Procedure of Weberโs test
- A vibrating tuning fork is placed in the middle of the forehead, or on top of the head equi-distant from the patientโs ears, in contact with the bone.
- The person is asked to report in which ear the sound is heard louder.
Interpretation of Weberโs test
Normal person โ hears equally on both sides.
Conductive deafness โ sound in diseased ear is louder than normal ear
Perceptive deafness โ sound in normal ear is louder than diseased ear.
Principle of Rinne test
- to compare bone and air conduction hearing in the same ear
Procedure of Rinne test
- Gently tap the tuning fork (tap it on a book or on your knee or elbow).
- Place it on mastoid process (bone conduction; BC) until the subject reports that he no longer hears vibration
- then held it in air next to ear (air conduction; AC) asking the person to report when sound is no longer heard
Interpretation of Rinne test
- Normal hearing persons will note air conduction twice as long as bone conduction (AC >BC; Rinne positive)
- With conductive hearing loss, bone conduction sound is heard longer than or equally as long as air conduction (BC >AC; Rinneโs negative)
- With sensorineural hearing loss, air conduction is heard longer than bone conduction in affected ear, but less than 2:1 ratio (reduced +ve Rinne)
Principle of Schwabach test
- compare bone conduction of patient with that of physician.
Procedure of Schwabach test
- Strike a 512 Hz tuning fork softly and place it on the mastoid of patient and then place it on mastoid process of physician
Results of Schwabach test
- Normal person โ patient = physician.
- Conduction deafness (one ear) โ patient > physician.
- Nerve deafness (one ear) โ patient < physician.
what does Pure tone audiometry (PTA) test?
- tests the hearing of both ears
Device used in Pure tone audiometry (PTA)
A machine called an audiometer is used to produce sounds at various intensity (measured in decibels) and frequency (measured in Hz).
Is each ear tested separately in Pure tone audiometry (PTA) test?
yes
Procedure of Pure tone audiometry (PTA) test
PPT
what is Oto-Accoustic Emission?
- vibrations created by contractions of the outer hair cells that are located in the cochlea.
Procedure of Oto-Accoustic Emission testing
- The identification and recognition of sounds of different frequency is thereby amplified.
- The outer hair cell contraction generates a vibration within the cochlea that is retrogradely transduced to the middle ear. There, it is transduced by the ossicles to the eardrum, that is brought to vibration.
- These vibrations create sounds that can be recorded in the ear canal.
- These sounds are soft, but potentially audible,
infrequently amounting to as much as 30 dB SPL.For detection of these OAEs, normal middle ear function is mandatory. - OAEs are generated only when the organ of Corti is in normal or near normal condition and their presence, therefore, is indicative of normal middle ear and cochlear function.
