PHYSIOLOGY 214:
A2 NOTES
,RESPIRATION
The respiratory system exists mainly to supply the body with oxygen (O₂) and remove
carbon dioxide (CO₂)
This is essential because cells need oxygen for Cellular Respiration
Occurs in the mitochondria:
Food + 𝑂2 → 𝐶𝑂2 + 𝐻2 𝑂 + 𝐴𝑇𝑃
ATP is required for:
• muscle contraction
• active transport
• nerve signaling
• protein synthesis
• survival of cells
Without oxygen, ATP production falls and cells fail/ tissues die
INTERNAL VS EXTERNAL RESPIRATION
A. Internal Respiration (Cellular Respiration)
Occurs inside tissues/cells.
Metabolic use of oxygen by cells to produce ATP.
• Happens in mitochondria
• Consumes O₂
• Produces CO₂
• Produces energy (ATP)
Major active tissues
• Brain
• Heart
• Skeletal muscle
Respiratory Quotient (RQ)
𝐶𝑂2 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝑅𝑄 =
𝑂2 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑
Indicates which fuel is being metabolized.
Different nutrients require different amounts of oxygen to break them down, and they
produce different amounts of carbon dioxide.
,So, by looking at the ratio, we can tell whether the body is mainly burning
carbohydrates, fats or proteins
Typical values
Fuel RQ
Carbohydrates 1.0
Protein 0.8
Fat 0.7
B. External Respiration
Refers to all processes involved in moving gases between atmosphere and cells.
, Includes four steps:
1. Ventilation
Movement of air into and out of lungs.
2. Gas exchange in lungs
Diffusion between alveoli and pulmonary capillaries
3. Gas transport in blood
Blood carries O₂ to tissues and CO₂ to lungs
4. Gas exchange at tissues
Diffusion between systemic capillaries & tissue cells
Non-Respiratory Functions of the Respiratory System
The lungs do more than gas exchange.
Functions:
• Helps regulate blood pH
• Heat loss
The respiratory tract transfers heat to the air, so breathing helps cool the body
slightly.
• Water loss
• Speech and vocalization
Air moving through the larynx causes the vocal cords to vibrate - this produces
sound.
• Smell (olfaction)
Odor molecules enter the nasal cavity during breathing and stimulate olfactory
receptors, which send signals to the brain.
• Filters foreign particles
The respiratory tract cleans incoming air.
• Immune defense
• Enhances venous return
Breathing helps blood return to the heart.
GENERAL ANATOMY
The respiratory system is divided into 2 functional parts:
Conducting Zone Moves air.
Respiratory Zone Where gas exchange occurs.
A2 NOTES
,RESPIRATION
The respiratory system exists mainly to supply the body with oxygen (O₂) and remove
carbon dioxide (CO₂)
This is essential because cells need oxygen for Cellular Respiration
Occurs in the mitochondria:
Food + 𝑂2 → 𝐶𝑂2 + 𝐻2 𝑂 + 𝐴𝑇𝑃
ATP is required for:
• muscle contraction
• active transport
• nerve signaling
• protein synthesis
• survival of cells
Without oxygen, ATP production falls and cells fail/ tissues die
INTERNAL VS EXTERNAL RESPIRATION
A. Internal Respiration (Cellular Respiration)
Occurs inside tissues/cells.
Metabolic use of oxygen by cells to produce ATP.
• Happens in mitochondria
• Consumes O₂
• Produces CO₂
• Produces energy (ATP)
Major active tissues
• Brain
• Heart
• Skeletal muscle
Respiratory Quotient (RQ)
𝐶𝑂2 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝑅𝑄 =
𝑂2 𝑐𝑜𝑛𝑠𝑢𝑚𝑒𝑑
Indicates which fuel is being metabolized.
Different nutrients require different amounts of oxygen to break them down, and they
produce different amounts of carbon dioxide.
,So, by looking at the ratio, we can tell whether the body is mainly burning
carbohydrates, fats or proteins
Typical values
Fuel RQ
Carbohydrates 1.0
Protein 0.8
Fat 0.7
B. External Respiration
Refers to all processes involved in moving gases between atmosphere and cells.
, Includes four steps:
1. Ventilation
Movement of air into and out of lungs.
2. Gas exchange in lungs
Diffusion between alveoli and pulmonary capillaries
3. Gas transport in blood
Blood carries O₂ to tissues and CO₂ to lungs
4. Gas exchange at tissues
Diffusion between systemic capillaries & tissue cells
Non-Respiratory Functions of the Respiratory System
The lungs do more than gas exchange.
Functions:
• Helps regulate blood pH
• Heat loss
The respiratory tract transfers heat to the air, so breathing helps cool the body
slightly.
• Water loss
• Speech and vocalization
Air moving through the larynx causes the vocal cords to vibrate - this produces
sound.
• Smell (olfaction)
Odor molecules enter the nasal cavity during breathing and stimulate olfactory
receptors, which send signals to the brain.
• Filters foreign particles
The respiratory tract cleans incoming air.
• Immune defense
• Enhances venous return
Breathing helps blood return to the heart.
GENERAL ANATOMY
The respiratory system is divided into 2 functional parts:
Conducting Zone Moves air.
Respiratory Zone Where gas exchange occurs.
