Question

Describe the four postural reflexes that maintain body alignment and equilibrium?

Answer 1

Postural reflexes are responsible for the subconscious maintenance of the body’s posture when movement and position is altered and they ensure that the body remains upright and aligned. It is the effects of gravity on the body which triggers their response and so these reflexes do not begin to develop until after the baby is born. All but one of the postural reflexes arise from/are found in the midbrain.

The postural reflexes are divided into two groups – the righting reflexes and the equilibrium reactions. If only the head is misaligned, the righting reflexes will suffice; if the body is threatened to be moved beyond its base, then the equilibrium reactions will necessary.

1. Righting reflexes: The righting reflexes develop after birth and remain for life. They help the body to respond to rapid loss of balance and assist with integrated movements of the head on the trunk. The righting reflexes help take the maturing child through the developmental milestones of head control, rolling, sitting, crawling and standing.

• Neck righting reflex: The first of the righting reflexes to appear is the neck righting reflex. It is present at birth in a normal full term baby and strongest at about three months of age. It is triggered by stretching of the neck muscles when there is rotation of the head or movement of the cervical/neck spine. With the baby in supine/on his back, if the head is turned to one side, the whole body will follow, until it is brought into alignment with the head.
• The Labyrinthine Head Righting Reflex (LHRR): This is one of the most important of the righting reflexes. It emerges fully at about two months of age and enables the baby to start lifting his head in prone/on his tummy. Head lifting from supine/on his back develops more slowly than the lifting in prone. Head control is a vital skill and, without it, normal physical development is seriously compromised. A newborn baby has no head control at all. At four weeks, a baby in prone/on his tummy can lift his head for a moment or two. By 12 weeks of age, a baby on his tummy should be able to hold his head up and prop himself up on his forearms. By 24 weeks, his head control is strong and he can hold his weight on extended/straight arms. At 24 weeks, he will raise his head in anticipation of being pulled up. The LHRRs are strongest at ten months. They are responsible for maintaining the head in an upright position with eyes facing forward and level with the ears. It is reflex triggered by the position of the otoliths in the labyrinths of the ear and somatosensory inputs. These set off postural adjustments to restore the head to a normal position as the body moves. LHRR operates in both forwards and backwards and side to side directions when the body is upright.
• The Oculo-head righting Reflex (OHRR): This reflex is mediated in the cortex and requires intact vision and enough light in which an object can be seen. It will not function with the eyes closed or in the dark. For our eyes to operate usefully, we need stable head control, especially when the body and head move, and also the ability to fix our gaze and follow an object. The OHRR will maintain the required stability of the head, whilst the body moves, allowing the gaze to remain focused and fixed.
• The body righting reflex: The body righting reflex is also known as the body-on-body reflex. It appears at about seven months of age and is the response of the body to pressure stimulation. The body will right itself independently of the head, so this reflex modifies the neck righting reflex. It plays a role in helping the child to move from sitting to standing.

2. Segmental rolling reflex: The segmental rolling reflex develops at about six months of age and is a mature adaptation of the neck righting reflex and the body righting reflex. As its name suggests, rather than the body moving as one block, rotation/turning appears to take place about a central axis of the body and the shoulder and pelvis move separately. If the rolling movement starts with head rotation, the shoulders will follow, and then the pelvis. The movement can also be initiated from the opposite direction, at the pelvis. Rolling usually starts at about six months – supine to prone will be first and prone to supine a couple of months later. Once these movements are fully mastered, the segmental rolling reflex will not be used for this purpose but will be activated to smooth out movements such as running and jumping later on.
3. The Landau reflex: The Landau reflex is not a primitive reflex because it is not present at birth and it is not a true postural reflex because it should not persist beyond the age of a year. Many class it as a righting reflex but it may best be described as a bridging reflex. It is present from about three months until twelve months of age, although traces may be seen up to three and a half years until full reflex integration has taken place. When the baby is held in ventral suspension/supported under the tummy, the head, spine and legs will extend and he will fly like an airplane. In prone, the Landau helps with extensor/straightening tone. When the child can lift his head and chest, he is being prepared for movements such as crawling and getting into standing. If the Landau persists, the child may have retained primitive reflex(es) and poor development of balance.
4. The Parachute Reflex: The parachute reflex emerges at about eight months and is the last of the postural reflexes to appear. It is a defensive response and involves the arms being used in protective extension. If the infant is held in suspension and suddenly moved towards the floor, his arms straighten as if to prevent him from falling. The propping reaction is a similar response with the action being to the side. This can be tested from about seven months in a seated child who is tilted to one side – his arm will extend to protect him from falling to that side.