Mechanisms of Breathing

World Records – holding breath 8 minutes 58 seconds Breathing Normal Air 17 minutes 4 seconds Breathing Pure Oxygen

Today’s Agenda Breathing Movements Oxygen Transport Carbon Dioxide Transport Maintaining Gas Levels http://www.youtube.com/watch?v=HiT621PrrO0

Review – Name the following:

Review – Name the following:

Breathing Movements What forces air out of our lungs? What causes air to rush into our lungs?

Breathing Movements Pressure differences between atmosphere and the inside of our lungs cause inhalation/exhalation Gases move from an area of HIGH pressure to an area of LOW pressure Inspiration occurs when: pressure inside the lungs < atmospheric pressure Expiration occurs when: pressure inside the lungs > atmospheric pressure

Breathing Movements The pressure inside our lungs can be changed (vs. atmospheric pressure)…but how? The diaphragm is a muscle in your abdomen that controls breathing. The external and internal intercostal muscles move the ribs out and in, respectively.

Inspiration Diaphragm contracts, external intercostals contract, pulling ribs up and out. Chest volume increases Pressure in lungs decreases Pressure difference pulls air into your lungs (like a vacuum)

Expiration (quiet) Diaphragm relaxes (returns to normal), external intercostals relax, moving ribs back down and in. Chest volume decreases Pressures increases Air moves out of the lungs

Expiration (Forced) Diaphragm relaxes (returns to normal), internal intercostals contract, pulling ribs back down and in. Chest volume decreases Pressures increases Forces air out of the lungs

Pleural Membrane/Cavity A sac that surrounds the lungs, the pleural membrane ensures that the lungs will ALWAYS be slightly inflated. This is accomplished by maintaining a lower pressure in the pleural cavity than is in the lungs (even after expiration).

Accidents Happen… Jim was stabbed through the chest, resulting in a punctured pleural cavity. What has happened to the pressures in his lungs? Pneumothorax: a collapsed lung occurs when pressure differences cannot be established due to a puncture to the pleural cavity.

Gas Exchange Overview

Oxygen Transport Oxygen moves from the atmosphere to the alveoli were it diffuses into the blood stream. Oxygen is not very soluble ( doesn’t dissolve easily) in blood… Hemoglobin binds to O2, carries O2 throughout the bloodstream releasing most of it in capillaries which will diffuse into tissues. Hemoglobin  is the iron-containing oxygen-transportmetalloprotein in the red blood cells of all vertebrates[1] (except the fish family Channichthyidae[2] ) and the tissues of someinvertebrates. Hemoglobin in the blood is what transports oxygen from the lungs or gills to the rest of the body (i.e. the tissues) where it releases the oxygen for cell use, and collects carbon dioxide to bring it back to the lun

Oxygen Transport Video http://www.youtube.com/watch?v=WXOBJEXxNEo 2 min.12 sec.

Carbon Dioxide Transport CO2 is the byproduct from cellular metabolism It is transported from tissues into the bloodstream to the lungs where it diffuses to the atmosphere But how? 9% dissolves into the blood 27% binds to hemoglobin 64% of CO2 is converted to H2CO3 (carbonic acid) by an enzyme called carbonic anhydrase (found in the red blood cells)

Carbon Dioxide Transport http://www.youtube.com/watch?v=x26TWL3VKMg

Maintaining Gas Levels During exercise, cellular respiration increases causing CO2 levels to increase Increased CO2 levels in blood stimulates chemical receptors in the brainstem Sends signals to the external intercostal via nerve cells to increase breathing movements Increased breathing flushes CO2 from the body