Breathing structure and regulation

Question 1

Identify the structures of the respiratory tract and their function

Answer 1

General anatomy
Upper 	
• Nasal cavity: humidifies air
• Pharynx: breathing and swallowing
• Larynx: sound generation

Lower
• Trachea: connects larynx to bronchial tree
• Bronchial tree and alveoli: Type 1 (lining cells) and Type 2 (surfactant)
• Lungs and membranes: (connect membranes of lungs to rib cage)

Question 2

What is ventilation?

Answer 2

· The exchange of air between the lungs and the atmosphere so that oxygen can be exchanged for carbon dioxide in the alveoli.
· When volume of the lungs increases, the pressure, relative to the atmosphere goes down
· Atmospheric air rushes in
· When the volume decreases, the pressure in the lung goes up compared to external pressure

Question 3

Describe gas exchange between the airways and circulation

Answer 3

· Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs
· The walls of the alveoli actually share a membrane with the capillaries in which oxygen and carbon dioxide move freely
· Breathe in = heaps of oxygen in alveoli
· Oxygen molecules go down concentration gradient and attach to red blood cells, which travel back to the heart
· At the same time, the carbon dioxide molecules in the alveoli are blown out of the body with the next exhalation

Question 4

Detail gas transport of Carbon dioxide and Oxygen in the blood

Answer 4

Oxygen:
• 98% of O2 is transported via binding to haemoglobin
• 2% of O2 dissolves in blood

Co2:
Dissolution:
• Small amount of Co2 dissolves in blood

Bound to haemoglobin:
• Some may reversibly bind to haemoglobin to form carbaminohaemoglobin
• Once it reaches lungs, the Co2 is released and removed via expulsion

Bicarbonate buffer system:
• Red blood cells have a special enzyme called carbonic anhydrase
• This enzyme combines Co2 with water to make carbonic acid
• This carbonic acid then dissolves in the blood stream
• However, this decreases the pH of the blood = high acidity

Question 5

Describe the neural control of respiration

Answer 5

• Breathing can be both involuntary and voluntary
• Involuntary respiration is controlled by the brain stem
• Voluntary respiration is mediated by the cerebellum and hypothalamus

Question 6

Describe the chemical control of respiration

Answer 6

• Peripheral chemoreceptors: around the heart in the carotid and aortic parts. It measures o2 levels
• Central chemoreceptors: in medulla measure Co2 and pH
• Low o2 -> Peripheral chemoreceptors -> Medulla -> increases respiration
• High Co2 and acidity -> central chemoreceptors -> Medulla -> increases muscles of expiration

Question 7

Describe the cough and sneeze reflex.

Answer 7

• Deep inspiration
• Close glottis closes airway and compress thorax
• Pressure is built inside
Glottis opens and there is forced expiration