RESPIRATION
Respiration is the act of breathing.
Inhalation or inspiration refers to the intake of air
into lungs.
Exhalation or expiration refers to
breathing out or the movement of gases from the lungs to the atmosphere.
Ventilation is also used to refer to the movement of
air in and out of the lungs.
Diffusion the movement of oxygen and carbon
dioxide between the alveoli and the red blood cells
Perfusion is the distribution of red blood cells to and
from the pulmonary capillaries.
Types of
breathing:
1
Costal
(thoracic) breathing
2
Diaphragmatic
(abdominal) breathing
Involves the contraction and relaxation of
the diaphragm, and it is observed by the movement of the abdomen, which occurs
as a result of the diaphragms contraction and downward movement.
Mechanics and
Regulation of Breathing:
During inhalation, the respiratory centre sends impulses
along the phrenic nerve causing the diaphragm contracts (flattens), the n s
move upward and outward, and the sternum moves
outward, thus enlarging
the thorax and permitting the lungs to expand.
It is an active process. During a normal, relaxed
breath, a person inhales 500 ml of air. This amount is referred to as the tidal
volume.
During exhalation, the diaphragm relaxes, the ribs move
downward and inward, and the sternum moves inward, thus decreasing the size of
the thorax as the lungs are compressed. Normally breathing is carried out
automatically and effortlessly. It is an passive process.
A normal adult inspiration lasts I to 1.5 seconds, and
expiration lasts 2 to 3 seconds.
Respiration is controlled b (a) respiratory centers in
the medulla oblongata and the pons of
the brain and (b) çhemoreceptors
located centrally in the medulla and peripherally in the carotid and aortic
bodies.
These centers and receptors respond to changes in
the concentrations of oxygen (02 ) , carbon dioxide (C02 ) , and hydrogen (H+ )
in the arterial blood.
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