Physiology Practical 2

Question 1

what are the elements of the respiratory control system

Answer 1

respiratory control centre
- brainstem

sensorsy
- chemoreceptors ( central and peripheral) and lung receptors

effectors
- respiratory muscles

Question 2

what are the chemoreceptors

Answer 2

central and peripheral

Question 3

what do chemoreceptors do

Answer 3

Monitor the partial pressure of oxygen and carbon dioxide in the arterial blood and relay this information to the respiratory control centre.

Question 4

what is the breakpoint

Answer 4

This is defined as the subjective point where a person feels they cannot breath hold any longer.

Question 5

what is pulse oximetry

Answer 5

A non-invasive method for monitoring a patient’s arterial haemoglobin saturation (SaO2) .

Question 6

describe pulse oximetry

Answer 6

Measures absorbance
Displays the percentage of blood that is loaded with oxygen.
Heart rate is also recorded

Question 7

what happens in the response to carbon dioxide

Answer 7

Arterial PCO2 is the most important stimulus
Most of the stimulus comes from the central chemoreceptors, but the peripheral chemoreceptors also contribute and their response is faster
The response is magnified if the arterial PO2 is lowered

Question 8

what happens in response to oxygen

Answer 8

Only the peripheral chemoreceptors are involved
There is negligible control during normoxic conditions
The control becomes important at high altitude, and in long-term hypoxemia caused by chronic lung disease

Question 9

what are the three main factors controlling breathing

Answer 9

the blood levels of carbon dioxide
the blood levels of oxygen
the state of stretch of the lung tissues.

Question 10

what monitors the oxygen levels in the blood

Answer 10

carotid bodies

Question 11

describe what stretch receptors do

Answer 11

The lungs contain stretch receptors. These are stimulated as we breathe in, and the increased firing of the nerves from these receptors causes the medulla to inhibit further inspiration, and to promote expiration. Similarly, when we breathe out, the decrease in firing of these receptors activates inspiration.

Question 12

how do you measure gas levels in alveolar air

Answer 12

• use a Haldane tube

Question 13

how does a pulse oximeter work

Answer 13

1. Switch on the pulse oximeter by pressing blue button.
2. Place fingertip inside oximeter. Note: ensure that the finger is placed all the way in so that it
   covers the diode inside.
3. Wait for stable reading