Mass activity - occurs throughout the entire body when any area is stimulated, though the activity is most pronounced in the stimulated area.
Specific activities - involve certain limited areas of the body. They include reflexes, which are definite responses to specific sensory stimuli and generalized responses, which use larger groups of muscles that are involved in reflexes and may be aroused by external or internal stimuli.
Some of the physical hazards of infancy are of only temporary significance while others can affect the individual's entire life pattern. The more serious ones are
Unfavorable prenatal Environment - may lead to difficulties in adjusting to postnatal life, like mother being stressed during pregnancy.
Difficult and complicated birth - can cause brain damage. Birth requiring instruments or the fetus lies in a foot first, or a transverse position or a caesarean all these can cause problems.
Multiple births - are usually smaller and weaker than singletons. These babies tend to be born prematurely, which adds to their adjustment problems.
Post maturity - This arises only when the fetus become so large that the birth requires the use of instruments or surgery.
Premature - Causes more neonatal deaths than any other conditions. Brain damages can occur. Anoxia is common since the premature baby's respiratory mechanism in not fully developed, and hence needs three times as much oxygen as full - term infants. Sucking and swallowing reflexes are underdeveloped & hence may require special feeding. Premature affects adjustments not only during infancy but also for many years thereafter.