Gas Exchange (Humans)

Question 1

What is the pathway of air down the lungs?

Answer 1

• It enters the mouth
• It goes down the trachea
• Into the bronchi
• Into the bronchioles
• Into the alveoli
• It diffuses into the bloodstream

Question 2

What is the process of inspiration?

Answer 2

• The external intercostal muscles contract, internal intercostal muscles relax
• The ribs are pulled up and out
• The diaphragm contracts and flattens
• The volume of the thorax increases
• The pressure in the thorax decreases
• Air is forced into the lungs due to the pressure difference

Question 3

What is the process of expiration?

Answer 3

• The external intercostal muscles relax, internal intercostal muscles contract
• The ribs are pushed down and in
• The diaphragm relaxes and returns to its dome shape
• The volume of the thorax decreases
• The pressure in the thorax increases
• Air is forced out of the lungs due to the pressure difference

Question 4

How are alveoli adapted for gas exchange?

Answer 4

• High surface area to volume ratio for diffusion
• 1 cell thick alveolar wall for short diffusion distance
• Good ventilation maintains a steep concentration gradient of high oxygen and low carbon dioxide in the air in the lungs, increasing the rate of diffusion
• A rich blood supply due to dense capillary networks maintains a steep concentration gradient of high carbon dioxide and low oxygen in the blood supplied, increasing the rate of diffusion

Question 5

How does smoking cause emphysema and what happens?

Answer 5

• Smoking weakens alveoli walls
• The alveoli are damaged and the walls of the alveoli collapse
• This causes there to be less alveoli
• This means that there is much less surface area for gas exchange, so less gas exchange occurs
• The body receives less oxygen, and the individual can suffer from shortness of breath and fatigue

Question 6

How does smoking cause bronchitis and what happens?

Answer 6

• Chemicals in smoke damage cilia
• The cilia stop working
• Mucus cannot be wafted out of the airways
• This causes a build up of mucus
• Bacteria build up and reproduce
• This leads to constant infections = Bronchitis

Question 7

What is the effect of nicotine?

Answer 7

• Narrows blood vessels, leading to increased blood pressure
• It is also highly addictive
• Can increase your risk of heart attack/stroke

Question 8

What is the effect of carbon monoxide?

Answer 8

• It binds to haemoglobin, reducing your capacity to carry blood
• It means your heart and lungs have to work harder
• This can increase your risk of heart attack/stroke

Question 9

How does smoking cause lung cancer?

Answer 9

• Carcinogens in smoke like tar cause mutations
• These mutations lead to changes in DNA
• These can lead to uncontrolled cell division, resulting in a tumour

Question 10

What happens when a person has coronary heart disease and what causes it?

Important

Answer 10

• Cholesterol/fat builds up within artery walls, narrowing their lumens and increasing blood pressure
• Blood clots form
• The coronary artery is blocked
• The heart receives less blood and oxygen, and an individual can experience angina
• This causes the body to receive less oxygen
• The body has to start respiring anaerobically, producing lactic acid
• The heart muscle does not have enough oxygen to respire, leading to a heart attack

Question 11

Outline an experiment to investigate the effects of exercise on breathing rate

Answer 11

• Measure the number of breaths per minute for person A at rest
• Have them exercise for a set time, and then immeadiately after measure their number of breaths per minute
• Compare results
• Repeat step 2 every minute after exercise to measure the rate that it returns to normal
• Repeat this for different people, or wait until their breathing returns to normal and repeat for the same person

Question 12

Why does breathing increase after exercise?

Answer 12

• More muscular contractions
• More respiration in muscle cells
• More oxygen needed, and more carbon dioxide produced
• More gas exchange must happen
• This means more breathing must happen

Question 13

Why does breathing still occur after exercising even though we have stopped?

Answer 13

• Lactic acid built up needs to removed, which requires oxygen
• More carbon dioxide needs to be removed
• Oxygen debt