Physiology 🫁 Flashcards
1
Q
what are combined somatic sensations?
A
Both superficial & Deep
- stereognosis
- Vibration senses
2
Q
Test for crude touch
A
Cotton wool test
3
Q
Pathway for pressure sensation
A
Dorsal column medial leminscal system
A side information: Minimal distance in lips is 2 mm
4
Q
where are receptors for vibration sense present?
A
They are present in subcutaneous tissue in the muscle fibers
5
Q
what are types of pain?
A
- Cutaneous
- Deep
- Visceral
6
Q
Definition of cutaneous pain
A
- Pain sensation results from stimulation of pain receptors in skin
7
Q
Test for cutaneous pain
A
Pin prick test
8
Q
Definition of Deep pain
A
- Pain sensation results from stimulation of pain receptors in deep structures
- Like tendon, muscle, joint, ligament & Periosteum
9
Q
Test for Deep pain
A
- squeeze or pinch the muscle of calf or biceps and ask the patient to report as soon as sensation becomes painful.
10
Q
Definition of Visceral pain
A
- then sensation results from stimulation of pain receptors in viscera
11
Q
Type of Pacinian corpuscle receptors
A
(mechano-receptors present in the skin, deep tissues involved in the sensations of touch, pressure and vibrations).
12
Q
Compare between Rapidly adapting receptors & Slowly adapting receptors in terms of:
- Definition
- Example
- Other name
- Physiological significance
A
13
Q
Classification of sensation
A
General:
- Arises from widely distributed receptors all over the body.
Special:
- vision
- taste
- smell
- hearing
- Sense of equilibrium.
Emotional:
- fear
- anxiety
- sadness
14
Q
Com pare between Somatic sensation, Visceral sensation & Sensation organ in terms of:
- Arise from
- Crried by
- Examples
A
15
Q
what is the definition of Touch sensation?
A
- It is a sense or feeling produced by application of light mechanical pressure to the skin
16
Q
what happens if the intensity of touch increases?
A
if the intensity of the stimulus is increased, it is changing into pressure sense
17
Q
what are the types of touch?
A
a) Fine touch.
b) Crude touch.
18
Q
Definition of Crude touch
A
A type of touch sensation which is poorly localized
19
Q
Stimulus in case of Crude touch
A
Diffuses ill defined object, Touching the skin with a piece of cotton or the touch of clothes.
20
Q
Receptors of Crude touch
A
- Free nerve endings & hair end organs or follicle receptors “located in the hair follicles”
21
Q
Afferents of Crude touch
A
- A-δ nerve fibers “5-30 meter/second”.
- C fibers “0.5-2 meter/second”.
22
Q
Pathways of Crude touch
A
Pathway from the body:
- Ventro spino thalamic tract by A delta fibers
- Spino reticular tract by C fibers
Pathway from the face:
- Trigeminal pathway
23
Q
whose transmission is faster, crude or fine touch?
A
The transmission of crude-touch is much slower than fine touch
24
Q
Spatial arrangment of Crude touch
A
the spatial arrangement of the fibers in the pathway is poor
25
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
26
Definition of **Fine touch**
It is a **type of touch** which **informs us** accurately about the **shape, form and site of the tactile stimulus**.
27
Stimulus of **Fine touch**
Well localized object to the skin as tip of pencil, head of a pin, teeth of comb
28
Receprors of **Fine touch**
1. Meissner's corpuscles (rapidly adapting).
2. Merkel's discs (slowly adapting)
29
Afferents of **Fine touch**
A-beta rapidly conducting nerve fibers (30-70 meters/second).
30
Pathway of **Fine touch**
Fine touch impulses are transmitted by **A-beta nerve fibers** which travel through the **Dorsal column – medial lemniscal system (Gracil & Cuneate tracts).**
31
Types of **Fine touch**
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
32
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).
33
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.
34
Afferents of **Pressure sensation**
as fine touch. (G & C)
35
Pathway of **Pressure sensation**
as fine touch. (G & C)
36
Types of **Pressure sensation**
**Deep pressure sense:**
- Discriminate between different weights without lifting them
**Muscle tension sense:**
- Discriminate between different weights with lifting them
37
significance of **Pressure sensation**
- Maintain posture
- Diffrentiate between different weights
38
Defintion of **Vibration sensation**
- It is a **sensation** of **rhythmic pressure changes** produced by the **rapid repetitive stimulation of certain mechanoreceptors**.
39
Stimulus of **Vibration sensation**
It can be produced by placing the base of vibrating tuning fork on the skin over bony prominence
40
Receptors of **Vibration sensation**
i)Meissner's 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.
41
Afferents of **Vibration sensation**
as fine touch (G &C)
42
Pathway of **Vibration sensation**
as fine touch (G &C)
43
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.
44
Receptors of **Proprioceptive sensation**
1) Muscle proprioceptors.
2) Joint proprioceptors.
45
Pathway of **Proprioceptive sensation**
- At conscious level
- At subconscious level
46
Types of **Proprioceptive sensation**
1. Sense of position.
2. Sense of movement.
3. Muscle-tension sense.
4. Deep pressure sense.
47
what are the types of **Fine touch**?
1-Tactile localization
2-Tactile discrimination
3-Stereognosis
4-Texture of materials
48
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.
49
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 person's eyes closed provided that the distance between them is greater than the minimal distance.
50
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
51
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.
52
where is Tactile discrimination more accurate? and why?
- On the extremities than on the proximal parts due to:
1. **Greater number of touch receptors**, and subsequently a **greater number of afferents**
2. **Little convergence** of afferents.
3. **Wide area of cortical representation** and so good analysis and interpretation of sensory information.
53
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.
54
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
55
which type of sense is **Sense of position**?
static sense
56
what does **sense of position** represent?
**conscious orientation** of the **relative position** of the different **parts of the body to each other**.
57
which type of sense is **Sense of movement**?
dynamic sense
58
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**
59
what are receptors of proprioception?
60
Compare between pathway of proprioception at conscious & subconscious level in terms of:
- Center
- Function
- Pathway
61
Definition of **Thermal sensation**
Is the **sensation** that **enables us** to detect **temperature change**, it includes warm and cold sensation.
62
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**.
63
what are the types of thermo-receptors?
- External (peripheral) thermoreceptors
- Internal (central) thermoreceptors
64
Compare between External (Peripheral) thermo-receptors and internal (Central) thermo-receptors in terms of:
- Types
- Location
- Detect
65
Compare between Warm & Cold Receptors in terms of:
- Morphology
- Number
- Afferent fiber
- Discharge impulse between
- Maximum discharge
66
Thermo-receptors at zero degree
all receptors stop discharge and this is one of the methods of anaesthesia.
67
Thermo-receptors at 45 degrees
the person feels **“Paradoxical cold sensation”** due to a brisk discharge from the cold receptors “Paradoxical cold sensations”.
68
Thermo-receptors if temperature is less than 10 degrees
- Stimulate cold pain receptors
69
Thermo-receptors if temperature is more than 45 degrees
Stimulate warm pain receptors
70
what is the mechanism of stimulation of thermo-receptors?
71
what is the type of thermo-receptors?
Biphasic but mainly slowly adapting receptors
72
Adaptation of thermo receptors
73
Neural pathway of thermal sensation
74
Definition of Pain Sensation (Nociceptors)
- Unpleasant sensory and emotional experience associated with actual tissue damage.
75
Physiological significance of Pain Sensation
- Protective sense that direct the person to get rid of injurious stimulus.
76
what are the characters of pain receptors?
77
what is the type of pain receptors?
- They are morphologically one type → free nerve endings.
- They are slowly adapting and even non-adapting receptors.
78
Specifity of pain receptors
- Highly specific → respond to tissue damage & classified
**according to type of painful stimuli into:**
a. Mechanical pain receptor→ to mechanical stimulus.
b. Chemical pain receptor→ to chemical stimuli
c. Thermal pain receptor → respond to excess temperature → (<10°C &>45°C)
d. Polymodal pain receptor → respond to all above painful stimuli.
79
Threshold of pain receptors
high threshold → need strong stimulus that cause tissue damage.
80
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
81
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.
82
Definition of **Pain Threshold**
The lowest intensity of injurious agent needed to stimulate the pain receptors and produced pain sensation.
83
what are the methods of determination of the pain threshold?
1. By pricking the skin with a pin.
2. By compressing the skin against hard objects.
3. Thermal method “more accurate’’ by **applying to skin to a thermostatically controlled metallic rod** (Most of individuals begin to feel pain at 45°C and all feel pain at 47 C and this is known as thermal threshold for pain receptors stimulation).
84
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.
85
what is pain classified into?
86
what is the aim of sensory examination?
- To assess the integrity of sensory pathways
- To localize the site of lesion in central nervous system
87
steps of sensory examination
1. First teach the patient about the test (in his own language), then perform the test.
2. Should done quickly because patient get tired easily.
3. Patient eyes should be closed to eliminate the effect of vision on sensation.
4. Every part of the body should be examined systematically, so as not to miss one single dermatome i.e. done dermatomal.
5. Compare both sides of the body (similar parts).
6. Examine limb by starting distally and move proximally.
7. Outline the boundaries of areas of sensory loss.
8. 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.
88
why should **Sensory examination** be done quickly?
- because patient get tired easily
89
why should the patient eyes be closed during **Sensory examination**?
to eliminate the effect of vision on sensation.
90
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
91
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
92
why you should avoid regulary timed stimuli during **cotton wool test**?
- so that the patient does not anticipate the test
93
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
94
Test for tactile localization (Topognosis)
- apply gently head of pin to the skin ( bilateral, dermatomal, distal to proximal).
95
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.
96
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
97
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.
98
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
99
steps of testing **Sense of position**
- The subject’s 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.
100
Steps of testing **Sense of joint movement**
- The subject’s big toe is passively moved with eyes closed
- He is asked about the feeling of movement, its direction and extent.
101
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.
102
Definition of Reflex Action
- It is an automatic (involuntary) specific response of an organ caused by an adequate sensory stimulus.
103
Pathway of Reflex Action
1) Stimulus
(2) Receptor **Sensory neuron**
(3) CNS (spinal cord) **Motor neuron**
(4) Effector
(5) Response
104
Physiological significance of reflexes
- Its function differs from one reflex to another
e.g. flexion withdrawal reflex is a protective reflex.
105
Clinical significance of reflexes
- It tests the integrity of the pathway (to test for normal CNS function).
- Localization of the site of the lesion.
106
Classification of reflexes
- Systemic/General Reflexes
- Local Reflexes
107
Centre of Systemic/General Reflexes
**Systemic/General Reflexes:**
- Their centers inside CNS
108
centre of Local Reflexes
**Local Reflexes:**
- Their centers outside CNS
109
Types of General/Systemic reflexes
- Conditioned Reflexes
- Unconditioned Reflexes
110
centres of Conditioned & Unconditioned Reflexes
**Conditioned Reflexes:**
- Their centers present in cerebral cortex
**Unconditioned Reflexes:**
- Their centers present in CNS outside cerebral
111
what are Spinal Reflexes?
- They are reflexes whose centers are present in the spinal cord
112
Classification of Spinal Reflexes
They are classified into 3 types:
- Superficial spinal
- Deep spinal
- Visceral spinal
113
Definition of Superficial spinal reflexes
- The receptors of these reflexes are present on the body surface e.g. skin.
114
Examples of Superficial spinal reflexes
- Abdominal reflex.
- Planter reflex.
115
Definition of Deep spinal reflexes
- The receptors of these reflexes are present in deep structures e.g. ms, bone and joints.
116
Examples of Deep spinal reflexes
- muscle stretch reflex or tendon jerk
117
Definition of Visceral spinal reflexes
- The receptors of these reflexes are present in visceral organs.
118
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)
119
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.
120
Center of Plantar Reflex
S1 and S2
121
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.
122
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
123
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
124
Normal Plantar Response and Babinski Sign
PPT
125
Causes of Babinski sign
Physiological and pathological causes
126
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.
127
Pathological Causes of Babinski sign
- UMNL.
- When the cerebral cortical function is depressed as in coma.
128
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.
129
Center of Abdominal reflex
- T7 to T12 segments of the spinal cord
130
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.
131
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.
132
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).
133
Mechanism of tendon jerk
- It is a dynamic type the stretch reflex.
134
Receptor of Tendon Jerk
Nuclear bag fibers of muscle spindle
135
Afferent of Tendon Jerk
1ry endings.
136
Centre of Tendon Jerk
α-MNs of the stretched skeletal muscle
137
Efferent of Tendon Jerk
Thick myelinated type Aα nerve fiber
138
Response in Tendon Jerk
brief contraction followed by rapid relaxation.
139
Examples of Tendon Jerk
- Knee jerk
- Ankle jerk
- Biceps jerk
- Triceps jerk
140
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.
141
Center of Knee jerk
L2,3,4
142
Tendon stimulated in Knee jerk
- Tapping on the patellar tendon
143
Movemnet in Knee jerk
- Extension of the knee
144
Muscle contraction in Knee jerk
- Quadriceps femoris
145
Center of Ankle jerk
- S1-2
146
Muscle tendon in Ankle jerk
- Tapping on tendoachilles
147
Movement in Ankle jerk
Plantar flexion.
148
Contraction of muscle in Ankle jerk
Gastrocnemius and soleus
149
Center of Biceps jerk
C5-6
150
Muscle tendon in Biceps jerk
Tapping on the biceps tendon.
151
Movement in Biceps jerk
Flexion of the forearm.
152
Contaction of muscle in Biceps jerk
Biceps muscle.
153
Center in Triceps jerk
C 6-7
154
Muscle tendon in Triceps jerk
Tapping on the triceps tendon directly.
155
Movement in Triceps jerk
Extension of the forearm.
156
Contraction of muscle in Triceps jerk
Triceps muscle.
157
Summary of tendon jerks
PPT
158
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. Jendrassik's maneuver
2. Distracting patient’s attention
159
Jendrassik's maneuver
- ask the patient to hook his fingers or to clench his teeth → send signals from the contracted ms which stimulating γ-MNs.
160
Distracting patient’s attention
- prevents any voluntary inhibition of the reflex.
161
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
162
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.
163
Assessment of the ms tone by tendon jerk
- In hyperreflexia (exaggerated tendon jerks)→ hypertonia ( ↑ms tone).
- In hyporeflexia (↓ed tendon jerks)→ hypotonia (↓ms tone).
- In areflexia (lost tendon jerks)→ atonia ( lost ms tone).
164
Assessment of the integrity of pathway of stretch reflex by tendon jerk
PPT
165
Assessment of the state of Supraspinal centers by tendon jerk
PPT
166
what are visual reflesex?
1. Corneal reflex
2. Pupillary light reflex
3. Accommodation reflex
167
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.
168
Pathway of corneal reflex
PPT
169
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.
170
Procedure of corneal reflex
1. With a piece of soft cotton, touch the cornea.
2. The response is reflex closure of both eye lids.
171
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).
172
Center of Pupillary Light Reflex
- pretectal nucleus of the same side
173
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
174
Procedure of **Pupillary Light Reflex**
1. Examine the diameter of the 2 pupils of your colleague.
2. Ask him to close his eyes.
3. After 5 min direct the bright light of a torch to one eye.
4. Observe the changes in diameter of pupils of both eyes.
5. Repeat the experiment after instillation of atropine in conjunctival sac.
6. Record your finding and write your comment.
175
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.
176
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.
177
Description of Argyll-Robertson Pupil
- It is a condition in which the pupil does not respond to light reflex but responds to accommodation reflex
178
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.
179
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.
180
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.
181
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).
182
Methods of Measurement of Visual Acuity
There are many clinical methods for stating visual acuity:
1. Charts
2. Counting fingers
3. Hand movement
4. Perception of light
183
Clinical Charts of visaul acuity mesaurment
- Landolt's C charts
- Snellen's letter charts
- Emarah arabic chart
## Footnote
Check PPT
184
Landolt's 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
185
Steps of testing visual acuity by Landolt's 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.
186
Clinical Expression of Visual Acuity
PPT
187
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)
188
what is **Field of vision**?
- It is the part of environment around us which can be seen without moving the eye.
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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.
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Methods of Measurement of Field of vision
- Confrontation test
- Perimeter
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Describe Confrontation test
- It is a rough clinical test.
- The patient's field is compared with that of the examiner (who is supposed to be normal).
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Perimeter
- It maps the visual field and detects any defect in the visual field.
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Importance of determination of visual field
- Help in localization of the sites of lesions in the visual pathway.
## Footnote
Check PPT for lesion in eye **VVVVIIIIPPPP**
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Definition of Colour Vision
- It is the ability of the eye to perceive the different types and characters of colours.
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Mechanism of Colour Vision
TrichromaticTheory (Young- Helmholtz Theory )
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Definition of Colour blindness
It is inability of the subject to discriminate between colours which normal person can recognize.
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Nature of Colour blindness
commonly inherited as a recessive X- linked chromosome).
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what does colour blindess affect more?
Males
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Types of colour blindness
- The suffix "-anomaly" denotes color weakness and -anopia" color blindness.
- The prefixes "prot-=red," "deuter-=green," and "trit-= blue".
1) Anomalous trichromate
2) Dichromats
3) Monochromats
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Symptoms of Anomalous trichromate
- These patients have all three cone systems, but one may be weak.
- So they may have tritanomaly, deuteranomaly, or protanomaly.
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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.
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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.
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Tests of colour vision
- Ishihara chart
- Wool classification & Matching test
- Edrige green lantern test
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Ishihara chart
PPT
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what is **Audition or hearing**?
- sense that allows us to communicate and hence interact with other organisms throughout the world.
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what is **Hearing**?
- ability to perceive certain pressure vibrations in the air and interpret them as sound.
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Types of sound conduction
Air & Bone conduction
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Definition of **Air conduction**
Is the normal way of conduction of sound waves from air to inner ear through tympanic membrane and bony ossicles
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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.
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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.
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Types of deafness
- Conductive deafness
- Sensorineural deafness
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Causes of Conductive deafness
- It results from interference with the proper conduction and amplification of sound waves through the external and middle ears.
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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).
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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.
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Characters of Conductive Deafness
- Air conduction is more affected than bone conduction
- All frequencies are affected equally.
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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.
- Meneier's disease
- Damage of the cochlear nerve or auditory cortex due to severe head injuries or tumors.
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Characters of Sensorineural Deafness
- Both air conduction and bone conduction are affected equally
- Some frequencies are affected more.
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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
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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 → presence of hearing loss or deafness
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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
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what are tuning fork tests?
- Weber test
- Rinnie test
- Schwabach test
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Principle of Weber's test
- It can detect unilateral (one-sided) conductive hearing loss and unilateral sensorineural hearing loss
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Procedure of Weber's test
- A vibrating tuning fork is placed in the middle of the forehead, or on top of the head equi-distant from the patient's ears, in contact with the bone.
- The person is asked to report in which ear the sound is heard louder.
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Interpretation of Weber's test
**Normal person** → hears equally on both sides.
**Conductive deafness** → sound in diseased ear is louder than normal ear
**Perceptive deafness** → sound in normal ear is louder than diseased ear.
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Principle of Rinne test
- to compare bone and air conduction hearing in the same ear
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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
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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; Rinne's 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)
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Principle of Schwabach test
- compare bone conduction of patient with that of physician.
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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
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Results of Schwabach test
- Normal person → patient = physician.
- Conduction deafness (one ear) → patient > physician.
- Nerve deafness (one ear) → patient < physician.
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what does Pure tone audiometry (PTA) test?
- **tests the hearing of both ears**
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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).
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Is each ear tested separately in Pure tone audiometry (PTA) test?
yes
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Procedure of Pure tone audiometry (PTA) test
PPT
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what is **Oto-Accoustic Emission**?
- vibrations created by contractions of the outer hair cells that are located in the cochlea.
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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.
