respiratory system

define association (in terms of haemoglobin)

the combining of oxygen with haemoglobin to form oxyhaemoglobin. 

define dissociation (in terms of haemoglobin)

the release of oxygen from haemoglobin. 

define oxyhaemoglobin (in terms of haemoglobin)

a bright red substance formed by the combination of haemoglobin with oxygen, present in oxygenated blood. 

define haemoglobin

a red protein responsible for transporting oxygen in the blood of vertebrates. Its molecule comprises four subunits, each containing an iron atom bound to a haem group. 

define saturation (in terms of haemoglobin)

the extent to which haemoglobin in the blood is bound with oxygen 

define external respiration

the process of exchanging gases between the alveoli in the lungs and the blood 

define internal respiration

the exchange of gases, between the body's tissue cells and the blood 

define partial pressure

the pressure exerted by an individual gas held in a mixture of gas.  

define diffusion

the movement of gases across a membrane down a gradient from an area of high pressure (or conc) to an area of low pressure (or conc) 

define diffusion gradient

the difference in areas of pressure (or conc) from one side of a membrane to the other.  

define pulmonary ventilation

the inspiration and expiration of air from the atmosphere behind us.

define gaseous exchange

the extraction of oxygen from the air into the blood stream and then into the muscle tissues

define breathing frequency

the number of breaths taken per minute.

what percent of blood is plasma and what percent is blood cells?

blood consists of:

• 55% plasma

• 45% blood cells

what percent of blood combines with haemoglobin to produce oxyhaemoglobin and what happens to the rest?

• 97% combines with haemoglobin to produce oxyhaemoglobin (HbO2)

• the other 3% is dissolved within the blood plasma

how is carbon dioxide transported in the blood?

• 70% dissolved in water and carried as carbonic acid

• 23% combines with haemoglobin to create carbaminohaemoglobin

• 7% dissolved in blood plasma

define tidal volume

Tidal volume is the volume of air inhaled or exhaled in one normal breath.

define minute ventilation

Minute ventilation is the total volume of air inhaled or exhaled per minute.

resting and maximal value for breathing frequency

• resting = 12 - 16

• maximal = 40 +

resting and maximal for tidal volume

• resting = 0.5 litres

• maximal = 3-5 litres

resting and maximal for minute ventilation

• resting = 6-8 litres

• maximal = 200+ litres

how does external respiration work at rest?

• Occurs in the alveoli of the lungs

• O₂ diffuses from alveoli → capillary blood

  • High O₂ in alveoli, low O₂ in blood

• CO₂ diffuses from capillary blood → alveoli

  • High CO₂ in blood, low CO₂ in alveoli

• Diffusion gradients are moderate

• Meets low oxygen demand at rest

how does external respiration work during exercise?

• Breathing rate and depth increase

• O₂ diffuses from alveoli → blood at a faster rate

  • Steeper gradient due to ↓blood O₂

• CO₂ diffuses from blood → alveoli at a faster rate

  • Steeper gradient due to ↑blood CO₂

• Ensures sufficient oxygen supply to working muscles

how does internal respiration work during rest?

• Occurs at muscle capillaries

• O₂ diffuses from blood → muscle cells

  • High O₂ in blood, low O₂ in muscles

• CO₂ diffuses from muscle cells → blood

  • High CO₂ in muscles, low CO₂ in blood

• Diffusion gradients are small

• Matches low metabolic demand

how does internal respiration work during exercise?

• Muscles increase aerobic respiration

• O₂ diffuses rapidly from blood → muscles

  • Very steep gradient due to ↓muscle O₂

• CO₂ diffuses rapidly from muscles → blood

  • Very steep gradient due to ↑muscle CO₂

• Increased temperature and CO₂ maintain steep gradients

• Supports increased energy production

what are the partial pressures at external respiration at rest?

• PO2 in alveoli = 100

• PO2 in blood capillaries = 40

• so diffusion of O2 goes from alveoli to blood capillaries

• PCO2 in alveoli = 40

• PCO2 in blood capillaries = 45

• so diffusion of CO2 goes from blood capillaries to alveoli

what are the partial pressures at internal respiration at rest?

• PO2 in muscle cell = 40

• PO2 in blood capillaries = 100

• so diffusion of O2 goes from blood capillaries to muscle cell

• PCO2 in muscle cell = 45

• PCO2 in blood capillaries = 40

• so diffusion of CO2 goes from muscle cell to blood capillaries

what are the partial pressures at internal respiration during exercise?

• PO2 in muscle cell = 5

• PO2 in blood capillaries = 100

• so diffusion of O2 goes from blood capillaries to muscle cell

• PCO2 in muscle cell = 80

• PCO2 in blood capillaries = 40

• so diffusion of CO2 goes from muscle cell to blood capillaries