1.0 CENTRALIZED CONTROL
Centralized control removes contradictions and ensures harmony. The centralised master control of physiological functions is mediated by the nervous system, the endocrine
system, and the immune system. Underlying all these systems is the DNA molecule.
DNA has 6x10E9 bits of information called codons that represent 10E7 genes. Each gene codes
for one protein molecule and it is these molecules that catalyze or mediate the biochemical functions of the body. The functions
of DNA are control of all aspects of cell functioning primarily through protein synthesis and transfer hereditary information
to the next generation. DNA within one organism is quite stable. The processes of mitosis and meiosis occur in millions of
cells daily with few variations in DNA structure. To ensure stability DNA replication is semi-conservative. Mutations are
rare if we consider the billions of DNA-related processes that occur
3.0 THE NERVOUS SYSTEM
The nervous system sends sensory impulses from the periphery to the brain and the spinal cord. It sends motor impulses
from the brain and spinal cord to the periphery. It controls, co-ordinates, and integrates body activity in response to internal
and external environmental stimuli. It correlates sensory information, motor co-ordination, memory, and intellectual function.
Most human activities are not under conscious control. The existence of the autonomic nervous system enables many background
life-sustaining activities to continue without sensory input into the cerebrum.
3.0 THE ENDOCRINE SYSTEM
Hormones secreted in minute amounts and transported by the blood profoundly influence target
organs and tissues. Target tissues have specific receptors for hormones. The hypothalamus-pituitary-target organ axis is one
of the miracles of human biology. It enables the endocrine system to respond to environmental signals, emotions, and thoughts
mediated through the cerebral cortex. The hypothalamus, the pituitary and individual endocrine gland secretions are controlled
by negative feedback. As the product mediated by the hormone accumulates and reaches a certain level, further hormone production
is blocked. Hormones from the hypothalamus and the pituitary affect secretions by other glands. The endocrine system has several
functions: maintaining homeostasis (fluid and end electrolytes), growth and development (tissue growth and sex differentiation),
and adaptation to physiological stresses (fight or flight reaction), reproduction (menstruation and other reproductive processes).
The specific functions of hormones are morphogenesis, metabolic regulation, and functional integration.
4.0 THE IMMUNE DEFENCE SYSTEM
Immune defense is recognition and elimination of non-self (foreign) material.
Non-specific immunity is innate while specific immunity
is acquired. Non-specific immunity may be mechanical barriers like skin or mucous membranes, chemical barriers such as transferrin
or interferon, cells such as natural killer cells, granulocytes, and leukocytes. Specific acquired immunity is based on lymphocytes.
B lymphocytes produce antibodies (humoral immunity) whereas T lymphocytes attack the bacteria directly (cell-mediated immunity).
Cellular immunity is more important than humoral immunity.