ramla a. sandag – jailani, m.d. physiology department kkuh
TRANSCRIPT
RAMLA A. SANDAG – JAILANI, M.D.RAMLA A. SANDAG – JAILANI, M.D.
Physiology departmentPhysiology department
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Somatosensory system (Somatovisceral Sensory System)
- transmits sensations from receptor organs
in the skin, muscles, joints and viscera
to the brain.
*Two )2( main pathways:
1 .Posterior )Dorsal( Column Lemniscal tract
- fine touch, two-point discrimination , vibration and position sensations,
fine pressure
2 .Spinothalamic )Anterolateral( tract - pain and thermal sensations, crude
touch, crude pressure, tickle and itch
OBJECTIVES:
To be able to reasonably acquire the skill of testing the following general sensation:
1 .tactile sensations – light touch, pressure, tactile
localization and discrimination2 .joint position sense
3 .recognition of size, shape, weight forms and
textures of objects 4 .vibration sense5 .pain sensations
6 .temperature sense
REQUIREMENTS:
Cotton wools Thin bristles
Calipers, pins or disposable toothpicks
Test tubes with warm and cold water
Flat base tuning forks Different weights
TACTILE LOCALIZATION:
1 .Ask the subject to close her eyes.
2 .Touch different parts of the body with cotton wool.3 .Ask her to acknowledge
whether she feels the touch and ask her to locate the
exact area touched.4 .Note whether there is
abnormality like hypoaesthesia or hyperaesthesia.
* Hypoaesthesia – touch sensation is reduced. * Hyperaesthesia – sensations produced is
either painful, irritating, or tingling.
Spinothalamic tract interruption
- increase touch threshold - decrease in no. of touch
spots in the skin
- slight touch deficit - normal touch localization
Dorsal columns destroyed
- vibration and proprioception sense are lost
- increase touch threshold - no. of touch-sensitive areas in the
skin - impaired localization of touch
sensation
TWO-POINT DISCRIMINATION:
1 .Ask the subject to close her eyes.
2 .With the calipers wide apart, touch two areas of the back of the hand.3 .Ask the subject to say
whether she feels two points of touch or a
single point.
4 .Now decrease the distance between two limbs of the
caliper and measure in millimeter)mm( the minimum
distance that can be recognized as two distinct
points.
*Two-point threshold – is the minimum distance at which two
points of contact can be felt.
– is impaired in: dorsal column and parietal
cortical )somatosensory cortex( lesions5 .Determine two-point threshold in the
following areas – palm of the hand, fingertip, leg and back of
the neck.
RECOGNITION OF SIZE, SHAPE AND FORMS:
1 .Ask the subject to close her eyes.
2 .Place any common object like coins, keys, pen, etc .
in her palm and ask her to identify the object without
looking towards it.
* Stereognosis – ability to recognize objects.
* Astereognosis – loss of recognition of objects.
– early sign of damage to cerebral
cortex. – if without defect in touch and
pressure sensation ( Parietal lobe lesion posterior
to postcentral gyrus)
RECOGNITION OF WEIGHT DISCRIMINATION:
1 .Ask the subject to close her eyes and place her
hand on the table.2 .Place different weighs
in his hands.3 .Ask her to indicate if
she could identify the variations in the weights
placed on her hand.
Weight discrimination – the ability to assess the
weight of an object.
* An increase in intensity of stimuli is transmitted
to the brain in the form of : a. an increase in the number of
afferent fibers stimulated
b. increased frequency of action potentials in
these fibers
… These two features are perceived as an
indication of the strength of the stimulus.
VIBRATION SENSE:
1 .Ask the subject to close her eyes.
2 .Strike the tuning fork ( 128 – 250 cps )and place
it successively over identical body areas on each side of
the body.3 .Ask the subject to acknowledge
whether she feels the vibration and whether it is of the same
intensity on the two sides.
4 .Proceed from the upper part of the body downwards – the clavicle, tip of the shoulder, elbow, wrist ,
dorsum of the hand, anterior chest wall, anterior
superior iliac spine, patella, tibial tuberosity ,
lateral and medial malleoli and the base of the
big toe.5 .Test if the subject can accurately identify
when the vibration stops.
Vibration – a pattern of rhythmic pressure stimuli
… receptors involved: touch receptors especially
Pacinian corpuscles … pathway: dorsal column … degeneration occurs in:
- poorly controlled diabetes - pernicious anemia
- some vitamin deficiencies
JOINT POSITION SENSE:
1 .Ask the subject to close her eyes.
2 .Hold her finger or toe and make it up and down and ask her to recognize: a. movement of the joint
by saying NOW b. direction of the fingers
whether up or down.
PAIN SENSATION:
* SUPERFICIAL … With the prick of
a pin, elicit the sensation of pain
on a willing partner.
*PRESSURE
… Put pressure on deep structures such as
muscles, tendoachilles or bones, superior
orbital margin, etc and ask her whether she
feels pain.
TEMPERATURE SENSE:
1 .With two test-tubes containing warm and
cold water, touch at different sites of the body of your subject.
2 .Ask her to identify the temperature differences.