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Pathological reflexes:
Babinski’s
sign: there is dorsiflexion of great toe & fanning of other
toes. Seen in UMN lesion, also in infants &
normal persons with deep sleep.
Spinal cord:
Extends
from foramen magnum to 1st lumbar vertebra.
Length
– 45 cm in male & 43 cm in females.
Below the lumbar enlargement, the
spinal cord rapidly narrows to a cone shaped termination called
Conus medullaris.
Spinal corresponds to 31 pairs of
spinal nerves. (C-8; T-12; L-5; S-5; C-1)
Grey matter
is the collection of nerve cell bodies, dendrites & parts of
axons.
White matter
is a collection of myelinated & nonmyelinated nerve fibers.
Neurons in the grey matter of
spinal cord
Neurons in Anterior gray horn
Alpha motor neurons; Gamma motor
neurons & Renshaw cells
Neurons in lateral gray horn
Intermediolateral
horn cells
Neurons in posterior gray horn
Substania
gelatinosa of Rolando; Marginal cells; Chief sensory cells &
Clarke’s column of cells.
Ascending tracts of Spinal cord:
|
Situation |
Tract |
Function |
|
Anterior white funiculus |
Anterior spinothalamic
tract |
Crude touch sensation |
|
Lateral white funiculus |
Lateral spinothalamic tract |
Pain & temperature
sensation |
|
Ventral spino cerebellar
tract |
Subconscious kinesthetic
sensations |
|
Dorsal spino cerebellar
tract |
Subconscious kinesthetic
sensations |
|
Spinotectal
tract |
Concerned with spinovisual
reflex |
|
Fasiculus
dorsolateralis |
Pain & temperature
sensations |
|
Spinoreticular
tract |
Conciousness
& awareness |
|
Spinoolivary
tract |
Proprioception |
|
Spinovestibular
tract |
Proprioception |
|
Posterior white funiculus |
Fasciculus
gracilis |
Tactile sensation
Tactile localization
Tactile discrimination
Vibratory sensation
Conscious kinesthetic
sensation
stereognosis |
|
Fasciculus
cuneatus |
Descending tracts of Spinal
cord:
|
Situation |
Tract |
Function |
|
Pyramidal tracts |
Anterior corticospinal
tract |
Control voluntary movements
Forms upper motor neurons |
|
Lateral corticospinal tract |
|
Extra Pyramidal tracts |
Medial longitudinal
fasciculus |
Coordination of reflex
ocular movement
Integration of movements of
eyes & neck |
|
Anterior vestibulospinal
tract |
Maintenance of muscle tone
& posture
Maintenance of position of
head & body during acceleration |
|
Lateral vestibulospinal
tract |
|
Reticulospinal
tract |
Coordination of voluntary &
reflex movements.
Control of muscle tone.
Control of respiration &
blood vessels. |
|
Tectospinal
tract |
Control of movement of head
in response to visual & auditory impulses.
|
|
Rubrospinal
tract |
Facilitatory
influence on flexor muscle tone. |
|
Olivospinal
tract |
Control of movements due to
proprioception. |
Effect of upper motor neuron &
lower motor neuron lesion:
|
|
Effects |
upper motor neuron |
lower motor neuron lesion |
|
Clinical observation |
Muscle tone |
Hypertonic |
Hypotonic |
|
Paralysis |
Spastic type of paralysis |
Flaccid type of paralysis |
|
Wastage of muscle |
No wastage |
Present |
|
Superficial reflexes |
Lost |
Lost |
|
Plantar reflex |
Abnormal – babinski’s sign |
Absent |
|
Deep reflexes |
Exaggerated |
Lost |
|
Clonus |
Present |
Lost |
|
Clinical confirmation |
Electrical activity |
Normal |
Absent |
|
Muscles affected |
Groups of muscles are
affected |
Individual muscles are
affected |
|
Fascicular twitch in EMG |
Absent |
present |
Action of sympathetic &
parasympathetic divisions of ANS:
|
Effector
organ |
Sympathetic division |
Parasympathetic division |
|
Eye |
Ciliary
muscle |
Relaxation
|
Contraction |
|
Pupil |
Dilatation |
Constriction |
|
Lachrymal secretion |
Decrease
|
Increase |
|
Salivary secretion |
Decrease in secretion &
vasoconstriction |
Increase in secretion &
vasoconstriction |
|
GIT |
Motility |
Inhibition |
Acceleration |
|
Secretion |
Decrease
|
Increase |
|
sphincters |
constriction |
Relaxation
|
|
Gall bladder |
Relaxation
|
contraction |
|
Urinary bladder |
Detrusor
muscle |
Relaxation
|
contraction |
|
Internal sphincter |
Constriction
|
Relaxation
|
|
Sweat glands
|
Increase in secretion |
- |
|
Heart rate & force
|
Increase
|
decrease |
|
Blood vessels
|
Constriction of all blood
vessels except those in heart & skeletal muscle |
Dilatation |
|
Bronchioles |
Dilatation
|
Constriction
|
Resting membrane potential of
various cells of the body.
·Resting membrane potential of a
skeletal muscle is -90mV.
·Resting membrane potential of a
smooth muscle is -50 to -75mV.
·Resting membrane potential of a
cardiac muscle is -85 to -95mV.
·The resting membrane potential in
the nerve fiber is -70mV.
·The resting membrane potential in
the rods is -40mV.
·The resting membrane potential of
inner ear cell is -60mV.
Brain stem: (medulla oblongata,
Pons & Midbrain)
·Pathway for ascending &
descending tracts b/w brain & spinal cord.
·Important centers for regulation
of vital functions in body.
Medulla oblongata
·Respiratory centers: inspiratory
& expiratory.
·Vasomotor center: B.P & Heart
rate.
·Deglutition center: Pharyngeal &
Oesophageal stage.
·Vomiting center: induce vomiting.
·Superior & inferior salivatory
nuclei: controls secretion of saliva.
·Cranial nerve nuclei: nuclei of
10, 11 & 12 cranial nerves.
·Vestibular nuclei:
Pons
·Bridge b/w medulla & midbrain.
·Forms pathway connecting
cerebellum with cortex.
·Nuclei of 5 to 8th
cranial nerve.
·Pneumotoxic
& apneustic centers for regulation of respiration.
Midbrain: (Consist
of 2 parts Tectum &
cerebral peduncles)
·Tectum:
center for light & auditory reflexes.
·Cerebral peduncles: control of
muscle tone
·Control of complex & skilled
muscular movements, movement of eye balls
Thalamus:
Ovoid mass of gray matter,
situated B/L in diencephalons)
·Relay center: for sensations
(also called functional gateway).
·Center for integration of sensory
impulses: determining the quality of sensations(discriminative &
affective nature)
·Center for sexual sensations.
·Role in arousal & alertness
reactions.
·Center for reflex activity
·Center for integration of motor
functions.
Hypothalamus:
·Control the secretion of Ant. &
Post Pituitary hormones & adrenal cortex & medulla.
·Control of Autonomic nervous
system; Heart rate; B.P; Body temp; Food intake (satiety, hunger
&thirst); water balance; sleep & wakefulness.
·Role in behaviour & emotional
changes.
·Regulation of sexual function &
response to smell.
·Role in circadian rhythm.
Cerebellum:
·Vestibulocerebellum:
regulates tone, posture & receiving impulse for vestibular
apparatus.
·Spinoncerebellum:
regulates tone, posture & equilibrium by receiving impulses from
proprioceptors in muscles, tendons
& joints, tactile receptors,
visual receptors & auditory receptors.
·
Corticocerebellum:
concerned with the integration & regulation of well coordinated
muscular activities.
·Different parts are represented
in an upright manner in cerebellum. (opp: in cerebrum)
Basal ganglia: (concerned
with motor activities of extra-pyramidal system)
·Control of voluntary motor
activity, muscle tone, reflex muscular activity, associated
movements.
·Role in arousal mechanism.
Cerebral
cortex:
|
Frontal lobe |
Pre central cortex
(Post. Part) |
Primary motor area
(concerned with initiation of
voluntary movements & speech) |
Area 4
– center for movement |
|
Area 4S
– suppressor area. Inhibits movements initiated by area 4.
|
|
Pre motor area |
Area 6
– concerned with coordination of movements initiated by area
4. |
|
Area 8
– frontal eye field. |
|
Area 44 & 45(broca’s area)
– motor area for speech. |
|
Supplementary motor area |
Concerned with co-ordinated
skilled movements. |
|
Pre –frontal
cortex
(Ant. Part) |
Silent area or association
area
Center for higher functions –
emotion, learning, memory. |
Area – 9 to 14, 23, 24, 29 &
32.
Center for planned action.
Seat of intelligence.
Personality of individual. |
|
Parietal lobe |
Somesthetic
area I |
Area 1
– concerned with sensory perception |
|
Area 2 & 3
– integration of these sensations. Spatial recognition.
Recognition of intensity, similarities & diff. B/W stimuli |
|
Somesthetic
area II |
Concerned with perception of
sensation. |
|
Somesthetic
association area |
Synthesis of various
sensations perceived by S.Area-I. Stereognosis.
|
|
Temporal lobe |
Primary auditory area |
Area 41, 42 & wernicke’s area
– concerned with perception of auditory impulses, analysis
of pitch, determination of intensity & source of sound |
|
Auditopsychic
area |
Area 22
– interpretation of auditory sensation |
|
Area of equilibrium |
Maintenance of equilibrium
|
|
Occipital lobe |
Primary visual area |
Area 17
– perception of visual impulse |
|
Visual association area |
Area 18
- Interpretation of visual impulses |
|
Occipital eye field
|
Area 19 -
Movements of eye
|
Limbic system:
(It is a group of cortical & sub
cortical structures which form a ring around the hilus of
cerebral hemisphere)
·Regulation of olfaction,
autonomic functions (B.P, water balance & body temp).
·Control of circadian rhythm.
·Regulation of sexual function.
·Role in emotional state, memory &
motivation.
·Retention of recent memory.
·Most developed
part of Limbic System —
Hippocampal formation
·Major efferent from Limbic
system goes to — Mid brain reticular formation.
·Main function of Limbic
system is to — Control the emotional behaviour.
Proprioceptors:
(These are receptors which give
response to change in the position of different parts of the
body).
·Muscle spindle: gives response to
change in length of muscle.
·Golgi
tendon organ: gives response to change in force developed in
muscle.
·Pacinian
corpuscle: pressure receptor in fascia, tendon & joints.
·Free nerve endings:
Vestibular apparatus:
·Give response to rotatory
movements or angular acceleration of the head.
·Responsible for detecting the
position of head during different movements.
EEG: (ELECTROENCEPHOLEGRAM)
·Alpha rhythm:
Frequency: 8 to 12 waves / sec
Amplitude: 50µU.
Most marked in parieto-occipital
area.
Obtained in inattentive brain as
in drowsiness & light sleep.
·Beta rhythm:
Frequency: 15 to 60 waves / sec
Amplitude: 5 - 10µU.
Recorded during mental activity
or mental tension or arousal state.
·Delta rhythm:
Frequency: 1 to 5 waves / sec
Amplitude: 20 - 200µU.
Seen in tumour, epilepsy,
increased intracranial pressure & mental depression.
·Theta rhythm:
Frequency: 4 to 8 waves / sec
Amplitude: 10µU.
Seen in children below 5 years.
SLEEP:
·Sleep
requirement:
Newborn infants: 18 to 20 hours.
Growing children: 12 to 14 hours.
Adults: 7 to 9 hours.
Old persons: 5 to 7 hours.
·Types
of sleep:
|
Rapid eye movement sleep(REM) |
Non rapid eye movement
sleep(NREM) |
|
Eye balls move
|
Absent |
|
Dreams occur |
Absent |
|
Muscle twitching
|
Absent |
|
20 to 30% of sleep |
70 to 80% of sleep |
·Normal amount of C.S.F. in man is
150 C.C,
·Sympathetic
nervous system is controlled by —
Posterior hypothalamic nuclei
·Parasympathetic
nervous system is controlled by —
Anterior nuclei and part of middle nuclei of hypothalamus.
EYE:
§Refractory power
is measured in dioptre (D).
§Refractory power of cornea is
42D.
§Refractory power of lens is 23D.
§Refractory power of eye at rest
is 59D.
§Focal length
of cornea is 24mm.
§Focal length of lens is 44mm.
§The wave lengths of visible light
are approximately 397 to 723 nm.
§There are about 6 million cones &
12 million rods in human eye.
§Rods are responsible for dim
light or night vision or scotopic vision.
§Cones
are responsible for colour vision, sensitive to day light &
acuity of vision.
§Rhodopsin
is the photosensitive pigment of rods cells.
§Photosensitive pigment in cones
are
o Porpyropsin
– Red
o Iodopsin
– Green
o
Cyanopsin
– Blue
§
Electroretinogram
is the instrument to record the electrical basis of visual
process.
§
Test for visual acuity
– snell’s chart (distant vision) & Jaeger’s chart (near
vision).
§
Test for color blindness –
Ishihara’s colour chart.
§
Mapping of visual field –
perimetry.
§
Nearest point
at which the object is seen
clearly is about 7 to 40cm.
§
Farthest point
is infinite.
§
Myopia
(short sightedness) is corrected by concave lens.
§
Hypermetropia
(long sightedness) is corrected
by convex lens.
§
Astigmatism
is corrected by cylindrical lens.
§
Presbyopia
is corrected by convex lens.
EAR:
§
Ear is sensitive to sound between
1000 to 4000Hz range.
§
Hairs cells in organ of corti are
the receptors for auditory sensation.
§
Sound becomes painful above
140db.
§
Auditory centers – 41, 42 & also
auditopsychic area 22.
TONGUE:
§
Sense organ of taste sensation is
taste buds.
§
There are about 10,000 taste buds
& each taste bud is replaced in every 10 days.
§
Each taste bud consists of 4
types of cells and is supplied by about 50 nerve fibres.
§
Receptors are type III cells of
taste buds.
§
Taste center – opercular insular
cortex (lower part of post central gyrus).
§
Bitter taste has very low
threshold – 1 in 2,000,000.
§
Sweet taste has high threshold –
1 in 200.
§
Locations of taste buds are:
sweet – tip; salt – dorsum; sour – side; bitter – posterior.
SMELL:
§
Olfactory mucus consists of 10 to
20 million olfactory receptor cells.
§
Human nose can distinguish 2000
to 4000 different odours.
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