What are Reflexes?
A reflex action is an involuntary response to a particular stimulus. Reflexes exist to keep us safe, for example, the reflex action of withdrawing your hand if you accidentally touch a hot or sharp object. This is an automatic reaction that protects your hand from damage, and occurs much faster than if you were to move consciously.
What are Infant reflexes?
Primitive (infant) reflexes are automatic movement patterns that are seen in normal infants but not in healthy adults. These intrinsic reflexes function even before birth, and continue to aid development in infants. They help the fetus maintain the correct position in utero, help progress during a vaginal birth, and provide the first breath of life. In a newborn, they train the bladder and bowel to function automatically, and have a crucial role in assisting feeding.
As a child’s brain develops there is less of a need for infant reflexes. They should not persist into adulthood and can contribute to physical and cognitive problems. Reflexes use information from the skin and body that passes through nerves into the spinal cord. Here they form an arc that can coordinate a movement in response to a stimulus. This reflex arc can function without the information about the stimulus passing up to the brain. As normal child development occurs, and the frontal lobes of the brain grow, signals are sent from the brain to the spinal cord to suppress the infant reflexes. Healthcare staff often test these reflexes to check there is healthy development of a child’s nervous system.
Infant reflexes which re-emerge in adulthood indicate a problem in the nervous system.
Some examples of Infant Reflexes
The following are some of the normal reflexes seen in newborn babies:
- Root reflex. A reflex that is seen in newborn babies and helps the baby find the breast or bottle to begin feeding. When the baby’s cheek or lip is touched, the baby will automatically turn their head and open their mouth to follow and “root” toward the stimulus. In a baby who is breastfed, this reflex disappears around three weeks
- Suck reflex. Rooting helps the baby become ready to suck. When the roof of the baby’s mouth is touched, the baby will begin to suck. This reflex does not begin until about the 32nd week of pregnancy and is not fully developed until about 36 weeks. Premature babies may have a weak or immature sucking ability because of this. Babies also have a hand-to-mouth reflex that goes with rooting and sucking and may suck on fingers or hands.
- Moro reflex. The Moro reflex is sometimes referred to as the startle reflex. The reflex is mostly seen when an infant is startled by a loud, sudden noise. It can also occur with a sudden change in head position, or when the temperature changes abruptly. The baby responds by extending the head and legs and the arms jerk up and out with the palms up and thumbs flexed. Then the arms are brought together, the hands clench into fists, and infant begins to cry loudly. This reflex can normally be seen up to three months of age, though may last up to six.
- Tonic neck reflex. The asymmetrical tonic neck reflex is also known as the
fencing reflex as the infant’s position resembles that of a professional
fencer. When a baby’s head is turned to one side, the arm on that side
stretches out and the opposite arm bends up at the elbow. The tonic neck
reflex lasts about 6 to 7 months. - Palmar Grasp reflex. This reflex is present at birth, but can also be observed on ultrasound of a fetus as early as 16 weeks! Stroking the palm of a baby’s hand causes the baby to close their fingers in a strong grasp. The grasp reflex lasts to 6 months of age.
- Babinski reflex. (plantar reflex) When the sole of the foot is firmly stroked from heel to toe a characteristic response occurs. The big toe bends back toward the top of the foot and the other toes fan out. If a child’s nervous system develops normally, the reflex will actually reverse by three years old. In adults, stroking the sole of the foot causes the big toe to flex downwards.
- Step reflex. A newborn who is held upright with their feet almost touching a hard surface, moves as if they are attempting to walk. The step reflex helps proper development of the leg muscles and movement, and makes it easier for the baby to learn to walk when the time comes.
