why do we breathe?

Question

in relation to carbon dioxide forcing us to take a breath

Answer 1

to get oxygen to breathe

Answer 2

Simple . . . Carbon dioxide as you know is a product of catabolism. CO2 then diffuses out of cells and into the venous system, where it enters red blood cells. Red blood cells possess an enzyme called "carbonic anhydrase" which combines CO2 and water to form H2CO3. H2CO3 can dissociate into HCO3- and H+, and these two species diffuse from the red blood cell, and become dissolved in the plasma.

The HCO3- ion is transported to the lungs, where it is converted back into CO2 before it crosses into the alveoli, and is expired thereafter. The H+ ions stay in circulation, where the plasma is to be maintained at a certain pH. When the pH drops below a certain level (because of too much CO2, and thus too much H+), chemoreceptors are stimulated. These chemoreceptors are cells in the carotid arteries (and also in the medulla) that detect increased H+ ion concentration, and send AFFERENT nervous impulses to the respiratory control center (via the glossopharnygeal nerve/CN IX) in the pons and the medulla. The pons and medulla then send EFFERENT signals through the spinal cord, to C3-C5 region, where they exit and contribute to the phrenic nerve. The phrenic nerve innervates the diaphragm, and drives inspiration.

Note that while CO2 content in blood (H+ content technically) is the major stimulator of respiration, if the partial pressure of oxygen (PO2) drops below 60 mmHG (normally around 100), this too stimulates chemoreceptors (in the carotid only, NOT in the medulla!!). In severe hypoxia, this supercedes any other respiratory controls!!!!

Answer 3

By breathing we obtain oxygen that is carried by the blood to our cells, where the oxygen combines with glucose in the biochemical process we call cellular respiration, which releases ENERGY for ALL our bodily functions. As waste products, this reaction liberates carbon dioxide that is exhaled into the atmosphere.
You don't breath, no oxygen, no ENERGY, you die

Answer 4

oxygen is the last electron acceptor in the electron transport chain.

Answer 5

to survive