Nerves: Two types of nerves (which are comprised of Nerve cells, Nerve fibres and an outer covering), Which either originate from and terminate in spinal cord or brain. Many nerves extend from brain/spinal cord-some of which terminate in muscles while others in skin and other organs. Motor nerve is one of the nerves that carry impulses outward from the central nervous system to bring about activity in a muscle or gland. Sensory nerve carries information inward, from an outlying part of the body toward the central nervous system.
Different sensory nerves convey information about taste, touch, pain, temperature etc. to the brain. Sympa-thetic nervous system is one of two divisions of automatic nervous system, having fibres that leave the CNS , via a chain of ganglia close to the spinal cord, in the thoracic and lumbar regions. Its nerves are distributed to sweat glands, salivary glands, blood vessels, lungs, heart, intestines and other abdominal organs and genitals whose functions it governed by reflex action in balance with ‘Parasympathetic Nervous System’.
Blood: Blood is carried to various organs of the body by-
(i) Arteries: These are principal trunk vessels that carry purified blood from heart to even far off stretched distant parts of the body. They have a muscular coating due to which they can contract when torn or cut. They pulsate and carry forward impulsive wave by forcible contraction of the heart. Arterial blood’s colour is scarlet red and when it flows out of the arteries, it gushes, spurts or jets.
(ii) Veins: They are also principal blood carrying vehicles and carry impure blood from distant parts of the body to the heart. They have no muscular coat like the arteries hence, when cut or when blood flows out from them, its colour is dark red, stream flow is constant and continuous.
(iii) Capillaries( Arterioles): They start from where the arterial system ends and venous system begins. They are like tributaries/canals of rivers which carry arterial (pure) blood to cell of the former and collect impure (venous) blood. Blood flows quickly and in spurts from the capillaries.
Lymphatics: These are lymph glands (ducts) in human body, as lymph flows from them- throughout and from each area of body into the heart. Lymph ducts arc like feeding channels to general circulation. Their importance and utility lies in collecting any foreign/ poisonous matters circulating in the blood. They help to divest physical system of all the impurities, and raise and fortify defence mechanism of physical system.
Central Nervous System (CNS): It is the chief controller of our activities. It is situated in the brain and is comprised of:
(i) Cerebral or large brain
(ii) Cerebellum or small brain
(iii) Medula oblangata
(iv) Ports
(v) Spinal Cord
(vi) Nerve-fibres and Nerve-trunks
Its functions are controlled by brain which is supplied by blood. If, for any reason, brain is not supplied with blood, not only its function but also function of whole body will come to a standstill. Confirmation of death is decided and determined by ‘Death of brain’ and not merely by ‘failure of heart’, the reason being that even after heart failure, the body still contains heat.
RESPIRATORY SYSTEM
This consists of Nose, Throat, wind pipe, lungs. Main function of lungs being to let in fresh air (by inhalation of oxygen) and let out harmful and poisonous air (by exhalation of carbondioxide). Lungs have the capacity to expand and contract but, if these two qualities get effected, air cannot be inhaled or exhaled and process of oxygenation of blood cannot be carried on effectively and efficiently, as Heart sends blood to the lungs for purification. After due processing, blood is again sent back to heart for supply to all parts of body. Hence, importance of lungs should never be overlooked and their efficiency maintained by proper and requisite exercises so as to keep them functional.
Diaphragm : It is an important partition-wall between thorax and abdomen, heart and lungs, digestive system. It provides a division between chest and lungs on upper side and alimentary tract on the under side. Its two pillars support the kidneys. Aorta and food pipe (oesophagus) pass through it (from thorax into abdomen), and inferior vena cava and thorax and pass through it from the abdomen, alongwith other vessels and nerves.