Respiratory Physiology 2.2-mechanisms of breathing

Question 1

What is Boyle’s law?

Answer 1

Boyle’s Law states that the pressure exerted by a gas is inversely proportional to to its volume (P a 1/V).
Note that gases (singly or in mixtures) move from areas of high pressure to areas of low pressure.

Question 2

What is Dalton’s law?

Answer 2

Dalton’s Law states that the total pressure of a gas mixture is the sum of the pressures of the individual gases.

Question 3

What is Charles Law?

Answer 3

Charles Law states that the volume occupied by a gas is directly related to the absolute temperature (v a T)

Question 4

What is Henry’s Law?

Answer 4

Henry’s Law states that the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid

Question 5

How does breathing happen?

Answer 5

thoracic cavity changes volume

Question 6

What does Boyle’s law mean?

Answer 6

increased volume leads to decreased pressure
decreased volume leads to increased pressure
Gases always move from high pressure to low pressure

Question 7

What muscles does inspiration use?

Answer 7

The muscles of inspiration include the diaphragm, external intercostals, (and under heavy respiratory load) sternocleidomastoids and scalenes

Question 8

What muscles does expiration use when we want to forcibly expire?

Answer 8

internal intercostal and abdominal muscles

Question 9

What does the diaphragm separate?

Answer 9

abdominal and thoracic cavity

Question 10

Where are the internal and external intercostal muscles?

Answer 10

muscles that run between the ribs

Question 11

How do the sternocleidomastoids and scalenes move?

Answer 11

act on upper ribs and clavicle to lift them up for expansion of chest wall

Question 12

What are the muscles of expiration?

Answer 12

the internal intercostal muscles and the abdominal muscles

Question 13

Where are external and internal intercostal muscles in relation to one another?

Answer 13

internal intercostal muscles run in opposite direction underneath the external intercostal muscles

Question 14

What happens when internal intercostal muscles contract?

Answer 14

pull ribcage downwards and inwards

Question 15

What cavity do the abdominal act on when they contract?

Answer 15

abdominal cavity and reduce volume

Question 15

How is expiration brought about?

Answer 15

organs get pushed up against the diaphragm.
And then diaphragm gets pushed up into the thoracic cavity (by pushing diaphragm upwards) and we decrease the volume of the thoracic cavity.

Question 15

How do we inspire?

Answer 15

Diaphragm contracts, increasing superior and inferior dimensions of the lungs.
The phrenic nerve innervates the diaphragm and it causes the diaphragm to contract.
When the diaphragm contracts it flattens down.
So by flattening down, we end up increasing the volume of the thoracic cavity.
If we increase the volume of the thoracic cavity, we decrease the pressure.
If decrease pressure below atmospheric pressure- air flows from high pressure to low pressure.

Question 15

How do we expire?

Answer 15

phrenic nerve stops innervating the diaphragm and the diaphragm stops contracting and relaxes to dome shape.
And thoracic cavity volume is reduced and increases pressure to above atmospheric pressure.
And air leaves lungs.

Question 16

Mechanisms of the exterior intercostals?

Answer 16

through action on the sternum ‘pump handle’ - increase volume of thoracic cavity in the anterior and posterior dimensions

through actions on ribs ‘bucket handle’- increase in volume of thoracic cavity in the lateral dimensions

Question 17

What happens when internal intercostal muscles are employed?

Answer 17

actively pull the ribcage down and the sternum in

Question 18

Summary of the mechanics of breathing?

Answer 18

Inspiration: airways are pulled open by physical forces of inspiration - less resistance.
Expiration: airways are compressed by physical forces of expiration

Question 19

What happens during asthma?

Answer 19

Inappropriate constriction of the bronchial smooth muscle- which narrows the airways and increases resistance.
Aggravated during expiration because those airways are being compressed anyway

Question 20

What is Intra-thoracic (Alveolar) pressure?

Answer 20

pressure inside the thoracic cavity (pressure inside lungs)
May be negative or positive relative to the atmospheric pressure.

Question 21

What is a positive and negative pressure?

Answer 21

positive- more than atmospheric pressure
negative- less than atmospheric pressure

Question 22

What is intra-pleural pressure?

Answer 22

the pressure inside the pleural cavity, typically negative compared to atmospheric pressure (in healthy lungs)

Question 23

What is transpulmonary pressure?

Answer 23

difference between alveolar pressure and intra-pleural pressure.
Transpulmonary pressure should always be positive because intrapleural pressure should always be negative.

Pt= Palv-Pip

Question 24

Describe alveolar pressure throughout the inspiratory phase and expiratory phase ?

Answer 24

inspiratory phase- the pressure inside lungs is always less than the atmospheric pressure

expiratory phase- the pressure inside lungs is greater than atmospheric pressure and air moves out of the lungs

Question 25

What happens when alveolar pressure is the same as atmospheric pressure?

Answer 25

get no movement of air

Question 26

What happens to intrapleural pressure during expiration and inspiration?

Answer 26

negative throughout breathing cycle
inspiration- intrapleural pressure becomes more negative- chest wall leading the expansion of the thoracic cavity (pulls parietal pleura from visceral) and decrease pressure
expiration- becomes less negative. as chest wall contracting as its following the elastic recoil of the lungs and the two get compressed