Infant Brain Development

Before birth, the structure of the brain is outlined and constructed according to heredity factors found in the genetic blueprint of DNA. What begins as a simple tube of embryonic tissue develops over nine months into a complex system of intellect, reflexes and emotions. The neuron population that arises before birth comprises all that the brain will ever have.

After birth the fate of the brain is linked to the environment. Good nutrition and a learning environment rich in sensory stimulation helps neurons grow bigger and increase the complexity of synapses. Neurons stimulated over and over again will experience measurable structural changes that form the basis for learning.

The human brain is about 30% of it's adult size at birth. However, it develops very rapidly. Within the next two years it nearly triples in size. Growth in primary sensory, motor and visual areas is remarkable.

During the first year of life myelin is deposited to complete the fatty coating around the major tracks of white matter. The child sits, stands and walks indicating that these neural pathways are functionally complete. At the end of the first year the brain is about 55% of adult size.

At the end of the second year the brain is about 80% of adult size. During the second year the child climbs, steps, and names pictures of objects. They can speak in simple sentences - subject, verb and object.
- (Novitt-Moreno 1995)

The study of brain development in infants is a rather new undertaking. It wasn't until the mid 1960's that physicians and psychologists discovered that the brain of an infant is developed to more than a primative level. Dr. Peter Wolff, a child psychiatrist in Boston, is one scientist who went into homes with newborns and sat for long periods recording every action awake and asleep and discovered some amazing things. Independently, Dr. Heinz Prechtl also studied newborns in Groningen, Holland. Together their research led to key discoveries about infant states of consciousness.

"By recognizing the different states and realizing when they occur and what the expected responses are in each, parents not only can get to know their infants but also can provide most sensitively for their needs."

Parents need to have confidence in their own ability to raise their infant. Marshall and Phyllis Klaus (1985) state the following:

"We believe that the parent's own feelings and sensitivities to the infant's needs and pace form the ideal environment for the infant's natural development to unfold."
"Within us all are amazing inborn systems for communicating, nurturing and surviving."

(Klaus M, Klaus P 1985)

Understanding the Nervous System

The nervous system is comprised of a number of components. These are listed and defined below.

Cell Basic unit of all body systems.

Neuron
A neuron is a cell, but it differs from other types of cells.

It:
conducts impusles
is greatly sensitivite to oxygen deprivation
is important for many vital functions
does not multiply (incurable conditions that are a result of this are paralysis, chronic vegetative states, palsy, blindness)

Dendrite Receives impulses from other neurons and conducts them to the cell body.

Axon Conducts the nerve impulse away and out to the dendrites of other neurons and to muscles and glands.

Synapse Site of contact between the axon of one neuron and the dendrite of another.

Impulse Electric current that is measurable with fine instruments.

Neurotransmitter A chemical that transmits impulses from neuron to neuron. Some are called acetylcholine, epinephron, dopamine, and gamma-aminobutyric acid (GABA).

Myelin Fatty white substance that covers nearly all axons. Must be present to propagate most impulses. The myelin in infants is not yet laid down completely. For example, the development of myelin is one of the factors related to walking.

Myelinization Process of laying down of myelin.

Sheath of Schwann Layer of myelin around axon.

Nodes of Ranvier Gaps in the layer of myelin. Where the sheath of Schwann dips down and comes in contact with axon.

How Does the Nervous System Work?

The nerve impulse travels down the axon until it reaches the synapse causing a release of neurotransmitter from the end of the axon. The neurotransmitter passes through this ultramicroscopic synapatic gap to adjacent dendrites where it triggers a nerve impulse that is then propagated in the second neuron.

The nervous system can be divided into two. These are the central nervous system and the peripheral nervous system. The central nervous system includes the brain and the spinal cord. There are five macroscopic parts of the brain that develop in an embryo. These are the telencephalon, diencephalon, mesencephalon, pons and cerebellum, and the mendulla oblongata.

Telencephalon - Center for highest functions. Most developed in humans. Two major structures: Cerebral hemispheres and basal ganglia - areas for crude motor activity buried deep in cerebral hemisphers. Axons that pass from one hemisphere to the other are called commissural fibers.
Diencephalon - Second division of the brain. Small area between cerebral hemispheres. Two parts: Thalamus (main sensory relay center for the nervous system) and hypothalamus (vital area - temperature control, emotional states, control over autonomic nervous system).
Mesencephalon - Midbrain, smallest part. Mesencephalon, pons, medulla oblongata form the brain stem. Located between diencephalon and the pons. Damage or pressure on the brainstem, especially midbrain, leads to unconsciousness, coma and possibly death.
Pons and cerebellum - Together make up the fourth division of the brain. Cerebellum - many folded structure located under the occipital lobe. Equilibrium, muscle tone and coordination of voluntary muscle activity. Pons - located between the midbrain and the medulla. Separated from overlying cerebellum by a cavity - the fourth ventricle.
Mendulla oblongata - Last division of brain. Becomes continuous with the spinal cord at the foramen magnum. Respiratory and cardiac centers situated in the medulla. Pressure on them due to herniation and increased intracranial pressure can lead to coma and death.

(Liebman M, 1991)

Clearly, the brain is a very complex organ. It is also a dynamic organ in that the number and nature of neurons can be influenced by play activities. Check out some of the ideas!

To learn more about the brain, see the following web site:
Neuroscience for Kids - Explore the Brain and Spinal Cord

References

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Cell	Basic unit of all body systems.
Neuron	A neuron is a cell, but it differs from other types of cells. It: conducts impusles is greatly sensitivite to oxygen deprivation is important for many vital functions does not multiply (incurable conditions that are a result of this are paralysis, chronic vegetative states, palsy, blindness)
Dendrite	Receives impulses from other neurons and conducts them to the cell body.
Axon	Conducts the nerve impulse away and out to the dendrites of other neurons and to muscles and glands.
Synapse	Site of contact between the axon of one neuron and the dendrite of another.
Impulse	Electric current that is measurable with fine instruments.
Neurotransmitter	A chemical that transmits impulses from neuron to neuron. Some are called acetylcholine, epinephron, dopamine, and gamma-aminobutyric acid (GABA).
Myelin	Fatty white substance that covers nearly all axons. Must be present to propagate most impulses. The myelin in infants is not yet laid down completely. For example, the development of myelin is one of the factors related to walking.
Myelinization	Process of laying down of myelin.
Sheath of Schwann	Layer of myelin around axon.
Nodes of Ranvier	Gaps in the layer of myelin. Where the sheath of Schwann dips down and comes in contact with axon.