Download Classifications of reflexes

Classifications of reflexes
A) Primitive reflexes and genetic sub-programs
1. Reflex responses to light touch:
Light touch produces a variety of reflex responses, depending upon
the area stimulated and the age of the individual. The motor responses are
most marked in the early months of life.

Grasp reflex (palmar and plantar):
Light touch of the palm or sole produces reflex flexion of the
fingers or toes. The most effective way to elicit the reflex is to slide the
stimulating object, such as a finger or pencil, across the palm or sole from
the lateral border. A beautiful neurological organization of the palmar
grasp reflex has been described, in which finger flexion follows a definite
sequence: “middle - ring – little – index – thumb”.
Chain responses follow the initial reflex producing two further
stages, which are seen best in the palmer reflex. The first follows initial
flexion of the digits and consists of tensing of the flexed muscles to
produce a strong grasp. A strong tonic component at this stage of the
reflex ensures maintenance of the grasp as long as the stimulus persists.
The second stage occurs when traction is exerted by the stimulating
finger or pencil. This is followed by a progressive contraction of the arm
muscles, which is sometimes so strong that the baby can be lifted from
the examination couch. The palmer and planter grasp reflexes are easily
demonstrable in the neonate but then fade rapidly and become seldom
seen after 4 or 5 months of age. Phylogenetically, the reflex is suggested
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to have a survival value by enabling the infant animal to cling to the
mother's fur.
2. Reflex response to pressure and pain:
Although some of the responses to pressure serve a constructive
and functional role (such as the support reaction), the majority has a
protective and survival value (such as the withdrawal response). Many of
these responses are so well ingrained that only the most profound cerebral
depression inhibits them. For example, the persistent absence of balance
response in the neonatal period indicates severe disturbance and a poor
prognosis during infancy and childhood.

Babinski (planter) reflex:
This reflex is one of the fundamental signs of classical neurology.
The stimulus consists of a firm painful stroke along the lateral border of
the sole from heel to toe. The response consists of movement (flexion or
extension) of the big toe and sometimes movement (fanning) of the other
toes. Techniques have been described to elicit the response by stimulating
other areas (e.g. stroking the lateral border of the dorsum of the foot,
squeezing the calf or running the fingers along the anterior border of the
tibia). These maneuvers are most effective when the reflex is
pathologically exaggerated.
The reflex is present throughout life. In the first year or two, the
surface area from which stimuli are effective is quite extensive.
Thereafter, it shrinks until the lateral side of the sole is the principle area
from which a response can be obtained. The motor response is similarly
widespread at first so that movement of all the toes is noticeable and
extension of the big toe usually predominates over the weaker flexion
movement. After this age, however, the motor response becomes more
controlled and restricted.
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3. Reflex responses to kinesthetic stimuli:
Many reflex responses originate from stimuli from the tendons,
muscles and joints. Most of these reflexes are important for the
maintenance of posture and orientation of the body in space.

Tendon reflexes:
These are simple monosynaptic reflexes, which are elicited by a
sudden stretch of a muscle tendon such as occurred when the tendon is
tapped. They are present throughout life and are most useful
diagnostically for the detection of upper motor neuron lesions
(exaggerated response), myopathic conditions (depressed or absent
response) and localization of the segmental lesions of the cord.
Table (1): Spinal cord levels of the tendon reflexes.

Reflex
Cord level
Biceps (elbow)
C5,6
Brachioradialis
C5,6
Triceps
C6,7
Long finger flexors
C8-T1
Hip Abductors
L2,3,4
Quadriceps (knee)
L2,3,4
Gastrocnemius-soleus (ankle)
S1,2
Eye righting (doll’s eye) reflex:
Passive turning of the head of the newborn leaves the eye “behind”
and a distinct time lag occurs before the eyes move to a new position in
keeping with the head position. Within a week or two of birth, this doll’s
eye phenomenon has disappeared as a result of an eye-righting reflex.
Failure of this reflex to appear indicates a cerebral lesion. Although this
reflex is listed with the reflex responses to kinesthetic stimuli, it is
probable that the labyrinthine also has a major influence on the reflex.
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
Head-body and body-head righting reflexes:
As mentioned earlier, various stimuli may produce the same
response. Orientation of the head in relation to the body and vice versa is
so important that it is not surprising to be produced by several righting
reflexes. Some of them arise from kinesthetic stimulation of the muscles
and joints of the neck. As the head is turned, the trunk realigns itself, so
as to remain in normal relationship to the head.
Similarly, turning of the trunk is followed by reorientation of head
position. These righting reflexes are present early in life and during the
second half of the first year of life, as they reinforce the action of the
visual and labyrinthine righting reflexes. A clear understanding of the
righting reflexes is necessary for the treatment of young children with
central neurological disorders. For example, in the case of a child who
cannot roll sideways, it is necessary to study these reflexes to know
whether it is therapeutically better to rotate the head and have the trunk
follow or vice versa.
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4. Reflex responses to visual and auditory stimuli:
As our visual and auditory senses are able to receive stimuli from a
distance, they are well equipped to act as warning mechanisms.
Consequently, many of the reflexes produced by visual and auditory
stimuli have a protective and survival value.

Blink reflex:
A bright light suddenly shone into the eyes, a puff of air upon the
sensitive cornea or a sudden loud noise will produce immediate blinking
of the eyes. There may be associated tensing of the neck muscles, turning
of the head away from the stimulus, frowning and crying. These reflexes
are easily seen in the neonate; and continue to be present throughout life.

Visual righting reflex
Once some visual awareness of orientation has developed, infants
do not readily tolerate distorted views and reflexly attempt to right their
head position in order to correct the view. This visual righting reflex
develops in close association with the labyrinthine righting reflexes.

Auditory orientating reflexes:
A sudden loud and unpleasant noise may produce the blink reflex
or the infant may remain still and show increased alertness. Quieter
sounds usually cause reflex eye and head turning to the side of the sound,
as if to locate it. This auditory orientation reflex is seen first at about 4
months of age. Thereafter, head turning towards sound stimuli occurs and
the accuracy of localization increases rapidly by 9-10 months; the sound
source is located directly within about 5° of accuracy. These reflex
responses are made use of in tests of infants for hearing loss. The pattern
of the localization responses indicates the level of neurological maturity.
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5. Reflex response to labyrinthine stimuli:
The attainment and maintenance of upright postures against gravity
are essential requirements for the successful motor development of the
human infant. The labyrinths are the most important organs concerned
with the development of anti-gravity postures and balance. Movement of
the head in any dimension stimulates the labyrinths; and after the early
weeks of life, it produces the appropriate responses.

Labyrinthine head righting:
Once this reflex developed, the infant’s head is always moved into
a position, in which the vertex is uppermost and the mouth horizontal,
whatever the position of the child. Thus, if the infant is held by the feet
with the trunk and head downward, the head will be extended backwards
in order to get it upright against gravity. Similarly, if the infant is held in
ventral suspension, i.e. horizontally with a hand supporting the trunk, the
head will be extended to achieve an upright posture. The response elicited
in this latter position has been described as the “Landau reflex”.
Labyrinthine head righting is not present at birth but develops
during the early months of life. Its influence is clearly seen in the
progressive ease with which the infant raises his head in the prone
position. In humans, head righting responses also occur in response to
visual stimuli, so that when observing the motor development of infants,
it is difficult to know the relative contributions made by these two head
righting mechanisms. Those children who fail to develop any head
righting ability at all, such as some children with cerebral palsy, are very
disabled in consequence. The development of head righting and the
ability to control the head position irrespective of gravity opens up great
possibilities for further motor development.
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A series of chain reactions ensue as various reflexes influence the
body position and the attitudes and movements of the limbs. For example,
once an infant can raise his head in the prone position, the way is open for
him to crawl. The sequence is as follows: (Head righting - increases in
strength and extent until shoulders are raised - this facilitates forward
movement of arms - support reflex of arms then enables chest to be raised
- this facilitates raising of pelvis - leads to drawing up of knees - then
support reflex enables pelvis to be raised - as security of support
increases, limbs can be freed in succession to develop an alternating
reciprocal movement - crawling is achieved).

Tonic labyrinthine reflexes:
The labyrinths are thought to exert a tonic influence upon the
distribution of muscle tone throughout the body and to control the
balance between the extensor and flexor muscles. It is very difficult to
isolate and study these effects in normal infants but the effects of their
disturbance are very obvious in neurologically damaged infants, many of
whom exhibit dystonic syndromes.
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