‫بسم هللا الرحمن الرحيم‬
‫﴿و ما أوتيتم من العلم إال قليال﴾‬
‫صدق هللا العظيم‬
‫االسراء اية ‪58‬‬
Neurophysiology of
Sensations
By
Dr. Abdel Aziz M. Hussein
Assist Prof. of Physiology
Central
Nervous
System
(CNS)
Peripheral
Nervous
System
(PNS)
Cervical
Thoracic
Lumbar
Sacral
Cocygeal
• NS has 3 main functional divisions;
a) Sensory division of NS:
• Detects changes in internal and external environments
and informs the CNS about them.
b) Motor division of NS:
• Initiates and controls the activities of skeletal muscles
• Controls the activities of plain muscles, cardiac muscles
and even glands.
c) Intellectual division of NS:
• Consciousness, memory, learning, thoughts, emotions
Centers
Tracts
Afferents
Receptors
1) Def.,
• Sensation is a conscious perception of particular feeling caused
by stimulation of certain type of receptor by its adequate
stimulus.
2) Classifications:
Sensations
General
Special
Organic
1) Special sensations:
• Vision, hearing, taste, smell and equilibrium
2) General sensations:
• Arise from receptors distributed allover the body
• Are classified into;
a) Somatic sensations: from somatic structures e.g. skin
b) Visceral sensations: from viscera
3) Organic senses: e.g. thirst, hunger and sexual desire
Def,
• These sensations arise from somatic structures of all
the body i.e. skin and deep tissues e.g. sk ms
Types:
• They include according to their adequate stimulus:
1. Mechanoceptive sensations: 2 types;
– Tactile e.g. touch, pressure, and vibration
sensations.
– Proprioceptive sensations e.g. sense of position
and movement
2. Pain sensation.
3. Thermal sensation; cold and warm.
Def.,
• Feeling produced by application of light
mechanical pressure to the skin
Types:
• They include 2 types :
1. Crude touch
2. Fine touch
Def.,
• Poorly localized touch sensation produced by touching
the skin with diffuse ill defined object e.g. a piece of
cotton or the touch of clothes.
Receptors:
• Free nerve endings
• Hair end organs
Pathway:
• Ventral or anterior
spinothalamic tract
Def.,
• Highly localized touch sensation produced by
application of a well localized object to the skin e.g. a
tip of a pencil or a head of a pin or teeth of a comb.
Receptors:
• Meissner's corpuscles
• Merkel's discs
Pathway:
• Dorsal column medial
leminiscal system or
gracile and cuneate
tracts
Types:
• It includes :
1. Tactile localization: is the ability to localize the point
of touch with eyes closed
2. Tactile discrimination : is the ability to perceive 2
points of touch with eyes closed as 2 separate
points of touch
3. Stereognosis: is the ability to recognize a familiar
object e.g. key with eyes closed
Pressure:
• It is a feeling produced by the application of heavy
mechanical stimuli to the skin
Vibration :
It is a feeling of rhythmic pressure changes produced by
the rapid repetitive stimulation of certain
mechanoreceptors e.g. Pacinian and Meissner's
corpuscles
It is tested by use of tuning fork
Pathway: both sensations are carried by Gracile and
Cuneate tract
Def :
• Feeling produced by stimulation of proprioceptors in
skeletal muscle and joints
• Or It is the conscious perception of the position and
movements of the different parts of the body,
particularly the limbs and joints.
• Types:
a) Static or sense of position
b) Dynamic or sense of movement of joints
Pathway: Dorsal column medial leminiscal
system or Gracile and Cuneate tract
Significance:
• The brain and other motor centers e.g. basal ganglia,
cerebellum use this information in the control of
posture and movements
N.B.
• Maintaining the body equilibrium or balance needs
discharge from 3 kinds of receptors;
1. Proprioceptors of foot
2. Visual receptors
3. Vestibular receptors (Crista in semicircular canals
and macula in utricle and saccule) in inner ear
Crista
Amuplaris
Macula
Def :
•Unpleasant sensory and emotional experience
associated with actual tissue damage.
Significance:
•Pain is a protective mechanism for the body.
•It occurs whenever the tissues are damaged and it
initiates protective reflex for removing the injurious
stimulus
Receptors:
•Free nerve endings
Pathway: lateral spinothalamic tract
Types:
• According to its source;
1. Cutaneous pain: pain comes from skin
2. Deep pain: pain comes from deep tissues e.g.
skeletal muscle, joints, ligaments, and tendons and
bone
3. Visceral pain: pain comes from viscera e.g. stomach
• According to its characters;
1. Fast pricking pain
2. Slow burning pain
Sensation
Pain
Crude touch
Fine touch
Deep pressure
Vibration
Proprioception
Tool used
Pin
Receptors
Free nerve endings
Pathway or
tract
Lateral
spinothalamic
tract
Cotton wool Free nerve endings Ventral
and hair end organs spinothalamic
tract
compass or Meissner's
Dorsal column
pencil or coin corpuscles
(gracile and
Merkels disc
cuneate tract)
Different
•Pacinian
Dorsal column
weights
•Ruffini endings
(gracile and
cuneate tract)
Tuning fork
•Pacinian
Dorsal column
•Meissner’s
(gracile and
corpuscles
cuneate tract)
Finger or toe •Muscle spindle
Dorsal column
of the patient •Pacinian corpuscles (gracile and
•Golgi tendon organs cuneate tract)
Def.
• Is the impairment of nerve functions due to high blood
glucose
Manifestations:
Sensory Neuropathy - Symptoms
Motor Neuropathy Symptoms
Autonomic Neuropathy Symptoms
Neuropathy - Signs
Glove and stock Hypoesthesia
Painless nature of diabetic
foot disease
Sensory nerve damage
THANKS