TUDY OF REFLEXES IN MAN
STUDY OF
REFLEXES IN MAN
When
a part of muscle or skin is stimulated, afferent impulses start from these and
reach a center in some part of central nervous system, from these afferent
impulses descend to motor nerve fibres and resulting in contraction of a muscle
of group of muscles takes place. These reflex responses depend upon the
integrity of the reflex arc and damage to any part of reflex are causes reflex
to disappear.
There
is three classes of reflexes. i) The superficial reflexes, ii) The deep or
Tendon Reflex and iii) The organic reflexes (including the action of the
sphincters)
i) The superficial
Reflexes:
In these, the simple form of reflex action is concerned. If certain part of
skin or mucous membrane is stimulated it results in contraction of certain
muscles. The path of impulse is by sensory nerve fibres to the spinal cord or
to a higher centre in the brain-stem or forebrain, thence by motor nerve fibres
to the muscle.
a) The Planter
Reflex:
flow to Elicit: The muscle of the lower limb should be relaxed and care should
be taken to see that the sole of the foot is warm. Stimulate the other edge of
the sole of the foot by gentle scratching with a pin or fingernail from behind
forwards.
With
a moderate stimulus, the response obtained is flexion of all the toes on the metartarsus
and they are drawn together. There is plantar Flexion of Big toe (The normal flexor
response)
Segments: 5th Lumber and 1st
Sacral
Note: 1.Plantar reflexes are diminished during sleep.
2
In infants, the reflex is brisk and the earliest response is drawing back of
the great toe, followed by extension and spreading out of all toes with
eversion of foot or dorsiflex on the ankle subsequently the knee and ship hip
air flexed (infa. tile response) Extension plantar response.
b. Babinski’s
Sign: (Extensor
Response) resembles the response obtained in infants but with difference of a
few points.
In
is deliberate and obtained with certainly on each stimulation, Extension of
great toe precedes all other movements. It is followed by extension and spreading
out of all toes, dorsiflexion of ankle and flexion of knee and hip.
Note: It is obtained in adults
only in cases if organic disease involving the pyramidal tracts. (U.M.N
paralysis)
c) Epigastric
and Abdominal Reflexes: These are valuable signs as they disappear hen the pyramidal tract of
the some side is affected.
How to Elicit: The person whose reflexes
are to be tested lies on his back and the abdomen is exposed.
A
pin or handle of pen is drawn firmly but lightly across the abdominal wall, on each
side in turn as shown.
This response is brisker in the upper part of
abdomen (Epigastric Reflex).
Note: in infants, it is not
present.
In
adults obesity or laxity of abdominal wall may abolish them.
Absence
or diminution suggests lesion of the pyramidal system.
Segments: Epigastric :
7th to 9th Thoracic.
Abdominal : 11th Thoracic to 1st
Lumbar.
d) Superficial
Reflex Dependent on. Cranial Nerve:
1) Conjuctival
Reflex: It
is elicited by touching the conjunetiva by a wisp of cottonwool or it results
in reflex closure of Eye due to contraction of the orbicular is palpabruxn.
Note: It is protective
phenomenon.
It
is absent in unconsicious persons.
Nerves
Concerned:
5th Cranical (sensory) and 7th Cranial (Motor).
2) Light
Reflex or Pupillary Reflex
How to Elicit: Ask the person to focus on
distant object one eye with one hard and with other hard shine a light from a
torch on the pupil from the sides only not front side.
The
pupil reflexly contracts immediately and then dilates again little and after undergoing
slight oscillations settles down to its normal size.
Note: Each eye should be tested
and do not use very bright light.
Path of Light
Relfex:
Afferent fibers involved are contained in the opti nerve intermediate station
is in corpora quardrigemina. Efferent fibres pass by 3rd nerve through the
ciliary ganglion to the pupil (SP) sphincter.
It
is a protective phenomenon.
It
is a sluggish the person may be semi-conscious.
The
reflex is absent if there is any lesion of the 3rd nerve.
3) Corneal
Reflex: If
cornea is touched by a wisp of cotton wool, it results in rapid closure of
eyelids. This reflex is abolished in coma of any type.
Nerve
concerned:
It depends on the integrity of the 1st division of cranial Afferent and the 7th
cranial (Efferent) nerve.
4) Pharyngeal
Reflex:
irritation of the pharyangeal mucous membrane by a spatula or a swabstick
produces. Constriction of the pharyngeal muscles. It results in producing vomiting
sensation or even vomiting sometimes.
Nerves
Concerned:
Afferent Glassopharyngeal.
Efferent: Vagus and spinal accessory
ii) Deep of
Tendon Reflexes: If a muscles is put on stretch and its tendon is sharply stuck the
contraction of a muscle results. It is known as deep or tendon reflex. They are
known as strength Reflexes.
a) Biceps
Jerk: The
elbow is fixed a right angle and forearm slightly, pronated. Thus, is then
placed over biceps tendon and struck by a percussion hammer, It results in
contraction of biceps causing flexion and slight supination of forearm.
Segments
Cervical: 5th
and 6th
b) Tricps Jerk: Flex the arm at right
angles and support it at the wrist strike the tricpes tendon just proximal to
the point of the elbow. ft results in contraction of the tricps causing
extension of the elbow.
Segments Cervical: 6th and 7th
c) Knee Jerk: The person whose knee jerk
to be tested is asked to sit on a chair or on the edge of the bed and cross one
knee over the other. This way the Quadriceps extensor is lightly stretched and
reflexly tone is increased.
Divert
his attention by engaging him in conversation or ask him to let the leg hand as
if it does not belong to him. Now strike a sharp blow by a percussion hammer on
the patellar Tendon mid-way between the patella its insertion Sudden
contraction of muscles cause the food to be jerked up. The briskness varies in
different individuals, therefore, always compare It with the other side in
health it is hardly ever absent. This procedure known as reinforcement.
Segments: Lumber: 2, 3 and 4
d) Ankle Jerk: Place the lower limb on the
bed everted or slight by flexed with one hand lightly dorsiflexed the foot so
as to put the tendo Achillies on the stretch and with the other hand strike the
latter on its posterior surface. A sharp contraction of the call muscle results.
Segments: Sacral 1 and 2
iii) Organic
Reflexes and Sphincters: This term includes such processes as Respiration Deglutition,
Micturition and Defaecation. They depend on complex muscular movements excited
by increased tension in the wall of the viscus concerned or in case of
respiration. partly by stimulation of a centre in the Medulla.
a) Respiration:
Does not require be tested
b) Deglutition :
Does not need to be specially tested:
c) Defaecation :
Segments: Sacral 4 and 5.
d) Micturition: This reflex act is
voluntarily controlled to a great extent by the higher centres in the brain
normally initiated by a voluntarily efforts but once started becomes a reflex
act difficult to interrupt: the stimulus being distension of bladder with urine
stimulus passes to the cord by way of nervi erigentes and rami communicates:
controlling centre being situated in the lower centre.
at various levels so that although the reflex arc is
left intact, spinal cord and cerebral lesions results in defects in the act micturition.
Nerves: The reflex path is partly
through plexuses in the bladder wall & partly in the pelvic plexuses. There
innervations of these plexuses is from the sympathetic (from lumber 3, 4 and 5
segments) and parasympathetic systems (secral 2 and nervi erigentes).
Knee jerk is tested by different methods as follows
- By crossing one knee over the hanging.
- By freely hanging knee the joint when the patient is sitting near
the edge of the table.
- The lying down or recumbent posture (in sick patients only).
Thus knee jerk should be tested in all the three
positions as mentioned above.
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