1. THE BREATHING MECHANISM

2. THE MECHANISM OF BREATHING
The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside.
INHALATION
1.  Diaphragm moves down, forcing air into airways
2.  Intercostal muscles contract, enlarging cavity even more
3.  Membranes move with the contractions
4.  Surface tension in alveoli and surfactant keep them from collapsing
5. Other muscles can force a deeper inhalation

3. THE MECHANISM OF BREATHING
The action of breathing in and out is due to changes of pressure within the thorax, in comparison with the outside.
EXHALATION
1.  Diaphragm moves up, forcing air out
2.  Intercostal muscles relax, shrinking the cavity
3.  Membranes move with the contractions
4.  Surface tension in alveoli keep them from collapsing
5.  Other muscles can force a deeper exhalation
ATMOSPHERIC PRESSSURE = 760 mmHg
Pressure is necessary for breathing, which is why it is difficult to breathe in high altitudes and also why a punctured lung can be dangerous.

4. INHALED AIR VS EXHALED AIR
FACTORS
INHALED AIR
EXHALED AIR
Oxygen [ ]
 21%
 16%
Carbon Dioxide [ ]
 .04%
 5%
Nitrogen [ ]
 78%
Dryness
 Drier
 Moist
Temperature
 Colder or Warmer than 37◦C
 Warm ~37◦C
Cleanliness
 Dirtier
Cleaner
(May contain bacteria & viruses)

5. BREATHING VS RESPIRATION
BREATHING: the act of bringing air in and out of lungs; consists of inhalation and exhalation ** Is an EXTERNAL mechanical process** CELLULAR RESPIRATION: when glucose and oxygen combine to produce carbon dioxide, water and ATP energy. ** Is an INTERNAL chemical process**

6. BREATHING RATE
The rate at which we inhale and exhale is controlled by the respiratory center, the Pons Medulla, within the Medulla Oblongata in the brain.
Inspiration occurs due to increased firing of inspiratory nerves and also the increased recruitment of motor units within the intercostal and diaphragm
Our lungs are prevented from excess inspiration due to stretch receptors within the bronchi and bronchioles which send impulses to the Pons when stimulated.
Exhalation occurs due to a sudden stop in impulses along the inspiratory nerves  
Breathing rate is all controlled by chemoreceptors within the main arteries which monitor the levels of Oxygen and Carbon Dioxide within the blood. If oxygen saturation falls, ventilation accelerates to increase the volume of Oxygen inspired.

7. BREATHING & HOMEOSTASIS
If oxygen saturation falls, breathing accelerates to increase the volume of Oxygen inspired.
If levels of Carbon Dioxide increase a substance known as carbonic acid is released into the blood which causes Hydrogen ions (H+) to be formed. An increased [ ] of H+ in the blood stimulates increased breathing rates.
Note: Breathing faster will increase the rate of oxygen is brought in and the rate at which cellular respiration occurs at. Carbon Dioxide levels primarily control the rate of breathing NOT oxygen.

8. BREATHING & HOMEOSTASIS
Initial Condition
12-20 Breaths per minute
Trigger/Cause
Heavy Exercise
Homeostatic Change:
Oxygen in blood increases
CO2 in blood decrease
Homeostatic Change:
Oxygen in blood decreases
CO2 in blood increase
Effector & what it does:
Inspiratory nerves fire more often to increase the rate of breathing - causing an increase in breathing
Sensors:
Chemoreceptors in the Aorta/other blood vessels respond to increase in CO2
Coordinating Center:
Pons Medulla

9. GAS EXCHANGE
GAS EXCHANGE: This refers to the process of Oxygen and Carbon Dioxide moving between the lungs and the blood
Occurs by diffusion*
MOVEMENT OF OXYGEN
Blood in the capillaries surrounding the alveoli has a lower concentration of Oxygen than the air in the alveoli which has just been inhaled.
Both alveoli and capillaries have walls which are only one cell thick and allow gases to diffuse across them.
MOVEMENT OF CARBON DIOXIDE
The blood in the surrounding capillaries has a higher concentration of CO2 than the inspired air due to it being a waste product of cellular respiration.
CO2 diffuses the other way  capillaries  alveoli exhaled

10. CONDITIONS NEEDED FOR GAS TRANSPORT
MOIST
So that gases can pass through the walls
2. THIN MEMBRANE
So that gases can dissolve and pass into the blood and cytoplasm of cells
3. CONCENTRATION GRADIENT
So that gases can move by diffusion (from high [ ] to low [ ] )
4. PRESSURE GRADIENT
So that gases can be pushed in the direction they need to move (from high press. to low press.)

11. GAS TRANSPORT O2 is needed for cells to undergo cellular respiration
(Glucose + O2CO2 + ATP + Water)
CO2 is a byproduct of cellular respiration & must be expelled from the body
HEMOGLOBIN: Is a chemical found inside red blood cells that can carry gases. Hemoglobin has 4 binding sites where oxygen, carbon dioxide, hydrogen ions & carbon monoxide can be carried.

12. GAS TRANSPORT OXYGEN TRANSPORT Dissolved in the blood plasma (3%)
Attached to hemoglobin as oxyhemoglobin (97%)
Hb+O2  HbO2
CARBON DIOXIDE TRANSPORT
Dissolved in the blood plasma (9%)
Attached to hemoglobin as Carbaminohemoglobin (27%)
Hb+CO2  HbCO2
As a combination of hydrogen ions dissolved in the blood or hydrogen ions on hemoglobin (64%)

13. GAS TRANSPORT CARBON MONOXIDE
When given the opportunity, Carbon Monoxide (CO) will bind to hemoglobin 200x more tightly than Oxygen can, making it difficult for our body to acquire & transport what we need.
Even if there is plenty of oxygen present, CO will be chosen over O2 by the hemoglobin, essentially leading to death.
CO is a colorless, odorless gas that is a by-product of combustion reactions (starting your car, heating your home, fires)

14. NERVOUS CONTROL OF BREATHING