B3.1 Flashcards
Gas Exchange
Gas Exchange in Animals
Gas Exchange
Driven by diffusion of molecules from high conc. to their low conc across an exchange surface.
Gas Exchange in Animals
Concentration Gradients
The difference in conc. of substances between locations - needed for diffusion to occur.
Gas Exchange in Animals
Aveolus
- Located in lungs, microscopic spheres (aveoli) of 1 cell thick, tissue wall bubbles.
- Covered in capillary blood supply
Gas Exchange in Animals
Surfactant
- Lines the inner surface of each alveolus.
- Is a phospolipid & protein monolayer film.
- Made by type 2 pnuemocyes
- Helps keep alveoli open and expanded for gas exchange.
- Surrounds wall of aveoli with phospholipid tails facing up, meaning aveoli’s walls won’t stick during an exhale, reduces surface tension that could cause H2O behind the surfactant to lead to lung collapse.
Gas Exchange in Animals
Bronchioles
- Air travels down a single tube (trachea) which then divies into 2 bronchi that travel to the lung.
- Bronchi then divide into many small tubes with the alveoli at the end of them (best way to deliver air)
- These small tubes are bronchioles.
Gas Exchange in Animals
Properties of Gas Exchange Surfaces
- Very thin (ideally 1 cell thick) for short distances.
- Moist for gases to dissolve.
- Large SA:V ratio for more rapid diffusion.
- Higher permeability of membrances.
Gas Exchange in Animals
SA:V of Large vs Small Organisms
- Larger animals have larger volumes, constituting for larger no. interior cells that are far removed from the external environment.
- Larger organisms and their low SA:V ratio prevent cell exchange directly with environment, thus have organs to obtain and transport gasses.
Gas Exchange in Animals
Conc. Gradients in Fish
- Fish swallow water, and thus dissolved oxygen.
- They pump this oxygen over thier gills which have blood supply running through them.
- Water moves along the gills with a higher conc. gradient than the blood travelling in the oxygen direction.
- Water maintains high oxygen conc. in the alveoli than the blood of the gills, causing O2 to diffuse into them (capillaries).
- This is done by ventilation, as O2 conc. drops, fish exhale and replace when the CO2 levels rise in blood.
Gas Exchange in Animals
Conc. Gradients in Land Animals
- Each alveolar wall is 1 cell thick & surrounded by a capillary, whose wall is also 1 cell thick.
- Allows for short distance for efficient diffusion.
- Many small alveoli allows for higher SA:V, and increases blood supply access.
- Surfactant prevents alveoli walls from attracting and collapsing it.
Ventilation
What is Ventiliation?
- Exchange of air between the lungs and the environment.
- Inhalation brings in O2, exhalation releases CO2.
- Frequent ventiliation maintains conc. gradients.
Ventilation
Inspiration?
- Process of inhalation
1. Based on CO2 levels, the Diaphragm is signalled to contract.
2. At the same time, external intercostal muscles signalled to contract, pulling up and out.
3. Lung volume increases.
4. Due to Boyle’s law (increased pressure correspond to decreased volume and vice versa), pressure drops in lungs.
5. Air moves in since outside air pressure is higher.
Ventilation
Expiration
- Process of Exhalation.
1. Diaphragm relaxes, pulling back up.
2. External Intercostel muscle relaxes, pulling in and down. Intercostal mucle can contract further pulling the ribs down (a big exhale)
3. Lung Volume decreases.
4. Lung pressure increases.
5. Air is pushed out the airway.
Ventilation
Diaphragm
- A thin, dome shaped mucle that sits below the lungs.
- Attatched to the lungs, rib cage and spine.
- The contraction & relaxtion of the diaphragm enables volume of the lung to change and faciliate breathing.
Ventilation
Patrial Vacuum
- Change in pressure, when the lungs increase in volume which causes a decrease in pressure due to the change of volume.
- Causes air to move into the lungs from the environment.
Ventilation
Spirometer
- Measures the amount of air breathed in and out & how quickly you breathe out.
Ventilation
Tidal Volume
- The volume of fresh air that is inhaled and exhaled during a typical resting breathing pattern.
- Not a maximum potentional of our lungs.
Ventilation
Inspiratory Reserve Volume
- Volume of air that a person could inhale forefully beyond the normal tidal volume.
Ventilation
Expiratory Reserve Volume
- The volume of air we could exhale beyond the normal tidal volume.
- Not as lage as the inspiratory volume as we retain a small residual volume after a large inhale –> protective way to retain some air in lungs at all times.
Ventilation
Vital Capcacity
- Potential lung volume during a deliberate/ forced inhale/ exhale.
- We have a large vital capaicity, an important adaptation for activities (swimming eg.,)
- The sum of the inspiratory reserve volume, tidal volume & expiratorty reserve volume. DOESN’T include small residual volume.
Ventilation
Boyle’s Law - Pressure & Volume
- An increase in volume leads to a decrease in pressure, vice versa.
- Explains how expanding the volume of the lungs reduces the pressure, which reduces the pressure to LOWER than the atmospheric pressure, cuasing air to move in during inhalation.
- Increase in pressure by reducing volume is caused by exhalation.
Ventilation
Role of Intercostal Muscles
To adjust the ribcage.
* External Intercostal muscles expand the ribcage when the contract. When relaxed, then reduce the volume of the lungs for exhalation to occur.
* Internal Intercostal muslces contract to further shrink the lungs (forced exhale)
Haemoglobin
What is Haemoglobin?
- The oxygen transport protein found IN red blood cells. It’s a conjugated protein with 4 polypeptide subunits, each with a Haem group made of Iron.
- The haem group is the binding site of oxygen –> each haemoblogin can transport 4 O2 molcules.
- Each red blood cells has many haemoglobins.
Haemoglobin
Saturation of Haemoglobin
- Refers to how many O2 molecules are bound to haemoglobin.
- Each subsequent O2 added makes it easier for the next one to bind.
Haemoglobin
Cooporative binding?
- Each O2 molecule that binds to Haemoglobin makes it easer for the next one.
- Due to shape changes in the protein that increase the potentional/ affinity for the next O2 to bind, i.e O2 is most attracted to a haemoglobin with 3 O2 already bound.