Chapter 38: Respiratory System

What determines whether an organism uses diffusion alone or bulk flow + diffusion?

• Size and environment (aquatic vs terrestrial)

Why can’t large organisms rely on diffusion alone?

• Diffusion is too slow over long distances

What do large organisms use instead of just diffusion?

• Bulk flow + diffusion

What are the 4 steps of gas transport?

1. Ventilation (bulk flow)

2. Gas exchange in lungs (diffusion)

3. Transport in blood/hemolymph (bulk flow)

4. Exchange between blood & cells (diffusion)

What is respiration (gas exchange)?

• Exchange of O2 and CO2 between organism and environment

Where does gas exchange occur in mammals?

• Lungs: alveoli ←→ pulmonary capillaries

• Tissues: systemic capillaries ←→ body cells

Does gas exchange require energy?

• No, it’s passive (diffusion)

What is ventilation?

• Movement of air/water over respiratory surfaces (lungs/gills)

Give examples of ventilation

• Breathing in lungs

• Water flowing in gills

What is the main respiratory organ in fish?

• Gills

What is the structure of gills?

• Lamellae → thin filaments with large surface area & many blood vessels

Why are gills efficient?

• Large surface area of filaments & lamellae + short diffusion distance

What is countercurrent flow?

• Blood flows opposite to water across gills

Why is countercurrent flow efficient?

• Maintains concentration gradient → maximizes O2 uptake

Do fish use countercurrent or concurrent flow?

• Countercurrent flow

What system do insects use for gas exchange?

• Tracheal system

What are spiracles?

• Openings where air enters for insect’s respiratory system

How does oxygen reach cells in insects?

• Directly through tracheae → tracheoles (no blood transport)

What is the main respiratory organ in terrestrial animals?

• Lungs

How are lungs ventilated?

• Negative pressure breathing = air is pulled into the lungs because pressure inside the lungs becomes lower than outside air pressure.

What happens during inhalation?

• Lungs expand → decrease pressure → air flows in

What happens during exhalation?

• Compress lungs → increase pressure → air flows out.

Why don’t we (humans) use full lung capacity at rest?

• Maintains stable gas levels

• Provides reserve

  • Prevents alveoli collapse

What protein carries oxygen in blood?

• Hemoglobin

What are key features of hemoglobin?

• 4 O2 binding sites found in red blood cells

What protein stores oxygen in muscles?

• Myoglobin = 1 binding site

What does the dissociation curve show?

• How hemoglobin binds/releases O2

What happens at high O2 levels (lungs)?

• Hemoglobin binds O2

What happens at low O2 levels (tissues)?

• Hemoglobin releases O2

What drives O2 and CO2 movement?

• Concentration gradients (high → low)

What is the gas movement in lungs?

• O2 = air → blood

• CO2 = blood → air

What is the gas movement in tissues?

• O2 = blood → cells

• CO2 = cells → blood

Does gas exchange require energy?

• No, because it occurs by passive diffusion where gases move high to low concentration