Respiration:
The HCO3-,
carbamino compounds, and dissolved CO2 are transported in venous
blood to pulmonary capillaries and alveoli. The low pCO2 in alveoli
will cause a shift of CO2 from erythrocytes and plasma into the
alveoli. On the other hand, the high pO2 in alveoli cause a shift of
oxygen into the plasma and erythrocytes.
The respiration is regulated by central chemoreceptors located in medulla that sense change in pH of CSF and peripheral chemoreceptors located in carotid artery and aorta that sense change in pH in blood, in both case caused by excess or deficit CO2 or change in pO2 causing hyperventilation or hypoventilation as required.
Exchange of oxygen and carbon
dioxide in lungs between alveolar air and blood is called external respiration,
in contrast to internal respiration occurring at tissue level. Blood (RBC) will
take oxygen from lungs to tissue and carbon dioxide from tissue to the lungs
for exhalation.
The respiration is regulated by central chemoreceptors located in medulla that sense change in pH of CSF and peripheral chemoreceptors located in carotid artery and aorta that sense change in pH in blood, in both case caused by excess or deficit CO2 or change in pO2 causing hyperventilation or hypoventilation as required.
Respiratory response to acid-base perturbations:
The respiratory system responds
immediately to change in acid-base status. The response becomes maximum once
the central and peripheral chemoreceptors are fully stimulated. E.g. in metabolic
acidosis plasma pH decreases, so hyperventilation occurs due to stimulation of
peripheral chemoreceptors and plasma pCO2 decreases (When HCO3-
decreases pCO2 decreases, i.e., regulatory response occurs in one
direction). During metabolic alkalosis, pH in plasma increases, this cause
depression of peripheral chemoreceptors and thus there is hypoventilation which
will retain CO2 in circulation.
No comments:
Post a Comment