Lecture 14: Respiratory Physiology I

Question 1

What are the functions of the respiratory system?

Answer 1

• Provides O2 and eliminates CO2
• Filters, warms and humidifies the air we breath
• Communication - sound production
• Sense of smell
• pH regulation
• Microbial defence
• Production of chemicals
• Thermoregulation

Question 2

What is the primary principle of ventilation ?

Answer 2

Air moves from an area of high pressure to an area of low pressure

Question 3

How does the air we breath move in and out of our lungs?

Answer 3

Pressure gradient - which are established by changes in size of the thoracic cavity - produced by contraction and relaxation of respiratory muscles

• Pressure gradients allow the flow of air btw compartments, a pressure difference is made between the lungs and atmosphere by changing lung volume
• Changing volume changes pressure
• volume changes —> pressure changes —> pressure equalisation and gas flow

Question 4

How are inspiration and expiration achieved ?

- in terms of pressure gradients

Answer 4

• To achieve INSPIRATION the higher pressure must be OUTSIDE the body
• To achieve EXPIRATION the higher pressure must be INSIDE the body

Question 5

What occurs during inspiration?

Answer 5

• Diaphragm and external intercostal contract
• Thorax expands –> increase in thoracic volume
• Lungs expand –> increase in volume and DECREASE in in PRESSURE
• results in air rushing INTO the lungs, air moves from the outside into the lungs

Question 6

What occurs during expiration?

Answer 6

• Inspiratory muscles relax
• Diaphragm moves upwards –> causing a decrease in thoracic volume and lung volume
• Results in an INCREASE in pressure
• causing air to be forced out of the lungs

Question 7

How is expiration a passive process?

Answer 7

it is driven by elastic recoil

• –> recoil back to resting volume which increase pressure and air is exhaled
• Accessory muscle can be used to assist expiration

Question 8

What muscles are used for inspiration?

Answer 8

• Diaphragm
• External intercostals

Air drawn into lungs, lungs expand, pectoralis minor muscles, intercostal muscles and diaphragm contract and the diaphragm flattens

Question 9

What muscle are used for expiration?

Answer 9

• Internal intercostals - FORCED expiration only
• Abdominals
  PASSIVE PROCESS
  Air forced out of the lungs, lungs contract - inspiration respiratory muscles relax and the daiphragm moves up
  Accessory muscles assist in FORCED expiration and inspiration

Question 10

How do you calculate daltons law?

Answer 10

partial pressure = fraction of individual gas x total gas pressure

Question 11

What is Boyles law?

Answer 11

At constant temperature, the volume of a gas varies inversely with absolute pressure
- if you increase volume - you decrease pressure