THE MECHANICS OF BREATHING

BREATHING

Breathing

• change in air pressure in lungs

• Air moves from high pressure to low pressure

BREATHING

• controlled by two major muscles:

• Intercostal muscles - between ribs

• Diaphragm – below chest cavity

INSPIRATION (INHALING)• diaphragm contracts & moves down• intercostals pull up and out• increases the volume of the chest

cavity• lowers pressure in lungs• air rushes in through nose & mouth to

fill alveoli

EXPIRATION (EXHALING)

• diaphragm and intercostals relax

• ribs are pulled down and inward

• Creates increased pressure in lungs

• air to rushes out• respiratory pearson.notebook

LUNG CAPACITY

• regular breathing does not use the full capacity of lungs

• have reserves for various situation.

LUNG CAPACITY

LUNG CAPACITY

Tidal Volume (TV)– volume of inhaled and exhaled in a normal breath.

Inspiratory Reserve Volume (IRV) – additional volume that can be taken in

Expiratory Reserve Volume (ERV) – additional volume that can be forced out

LUNG CAPACITYVital Capacity (VC) – total volume of gas that can

be moved in or out of the lungs

VC = TV+IRV+ERV

Residual Volume (RV) – amount remaining after a full exhalation

- prevents lungs from collapsing

Total Lung Capacity (TLC) – total volume in lungs at one time

Regulation of Breathing• usually unconscious• brain sends nerve impulse to muscles to

contract/relax

• controlled by CO2 levels in blood

• CO2 diffuses into plasma in blood

• forms H2CO3 in water

• build up of H2CO3 lowers blood pH

• causes brain to send impulse to increase BR so CO2 gets exhaled

Homeostasis – maintaining internal stable conditions