Physiology

Question 1

Where is respiratory rhythm generated

Answer 1

In the resp centres in the brain stem - MEDULLA specifically for rhythm generation

Question 2

What part of the brain stem modifies respiration

Answer 2

pons

Question 3

Where do the resp centres receive stimulation from and as such modify breathing in response to these signals.

Answer 3

Central and peripheral chemoreceptors
Higher brain centers e.g.. cerebral cortex
Stretch receptors in the bronchi and bronchioles
Juxtapulmonary receptors
Joint receptors
Baroreceptors

Question 4

Where are central chemoreceptors located

Answer 4

near the surface of the medulla

Question 5

What do central chemoreceptors respond to

Answer 5

the hydrogen in the CSF

Question 6

Why is CSF less easily buffered than blood

Answer 6

contains less protein

Question 7

Can CO2 diffuse across the blood brain barrier

Answer 7

Yes - readily

Hydrogen and carbonate ions do not diffuse easily across the BBB

Question 8

What will happen to the resp rate when there is hypercapnia

Answer 8

Hyperventilation

ie increases

Question 9

What is the most potent stimulation of resp in most people

Answer 9

Increases hydrogen ions in the CSF due to arterial CO2 increase results in firing of central chemoreceptors and stimulates ventilation to ‘blow off’ the CO2 and reduce the hydrogen ion conc in the CSF

Question 10

Where are peripheral chemoreceptors situated

Answer 10

Carotid and aortic bodies

Question 11

What do peripheral chemoreceptors sense

Answer 11

The tension of oxygen and CO2 and hydrogen ions in the bloods

Question 12

What initiates the hypoxic drive effect

Answer 12

peripheral chemoreceptors sensing low PO2 (less than 8kPa)

Question 13

In what group of patients is their hypoxic drive important

Answer 13

COPD due to chronic CO2 retention

Question 14

In what other circumstances is hypoxic drive important

Answer 14

high altitudes

Question 15

What happens in the hypoxic drive

Answer 15

peripheral chemoreceptors sense low levels of PO2 and act to increase ventilation

Question 16

What mediated the H+ drive of respiration

Answer 16

peripheral chemoreceptors

Question 17

What does an increase in H+ cause

Answer 17

hyperventilation to blow off CO2 to reduce hydrogen ion conc in blood

Question 18

In what circumstances may hydrogen ions be increased in the blood

Answer 18

DKA

exercise -lactic acidosis

Question 19

Summarise which receptors play a main role in the following:

1. Decreased arterial blood
2. Increased arterial CO2 and therefore increased hydrogen ions in CSF
3. Increased arterial hydrogen ions

Answer 19

1. peripheral chemoreceptors
2. central chemoreceptors
3. peripheral chemoreceptors

Question 20

What reflex guards against hyperinflation of the lungs

Answer 20

Herin-breur reflex

Question 21

What stimulates juxtapulmonary receptors

Answer 21

pulmonary circulation congestion and oedema

PE

Question 22

what stimulated baroreceptors

Answer 22

increased ventilation rate in response to low BP

Question 23

What muscles move the ribs up and out

Answer 23

External intercostal muscles

Question 24

What muscle increases the volume of the thorax vertically and what nerves supply it

Answer 24

Diaphragm

Phrenic nerve - C3, 4, 5

Question 25

Accessory muscle of inspiration

Answer 25

SCM | Scalenus

Question 26

Muscles of active expiration

Answer 26

Abdominal muscles | Internal intercostal muscles

Question 27

Major muscle of inspiration

Answer 27

Diaphragm | External intercostal muscles

Question 28

What three pressures are important in the lungs

Answer 28

Atmospheric and Intra alveolar = usually the same | Intrapleural

Question 29

Is the intra pleural pressure usually more of less than atmospheric pressure

Answer 29

less

Question 30

What happens to intra alveolar and intrapleural pressure during inspiration

Answer 30

both decrease but intra pleural pressure is always less than intraalveolar pressure = transmural pressure gradient

Question 31

What happens to intra alveolar and intra pleural pressure during expiration

Answer 31

both increase

Question 32

In what circumstance is the transmural pressure gradient abolished

Answer 32

pneumothorax

Question 33

Forces which keep alveoli open

Answer 33

Transmural pressure gradient Surfactant (which opposes alveolar surface tension) Alveolar inter dependence

Question 34

Forces promoting alveolar collapse

Answer 34

Elasticity of stretch pulmonary connective tissue fibres | Alveolar surface tension

Question 35

What stimulation causes bronchoconstriction and what causes bronchodilation

Answer 35

``` Parasympathetic = constriction Sympathetic = dilation ```

Question 36

what diseases cause airway floow restirction

Answer 36

COPD and asthma

Question 37

what does increased airway resistance result in

Answer 37

expiration is more difficult than inspiration | lungs hyperinflate

Question 38

What happens in dynamic airway compression

Answer 38

The rising pleural pressure during active expiration compresses the alveoli and airway Pressure in airway makes it more difficult for air to leave the lungs Doesn't cause problems in normal people but can be a problem in asthma etc

Question 39

What is meant by compliance

Answer 39

The effort needed to inflate the lungs | i.e. less compliant lungs require more work to produce a given degree of inflation

Question 40

Name a condition in which there is decreased compliance of the lungs

Answer 40

pulmonary fibrosis

Question 41

How much of your total energy is required to be expended in quiet breathing

Answer 41

3 percent

Question 42

What cells line the alveoli

Answer 42

Type 1 alveolar cells - single layer

Question 43

O2 partial pressure gradient

Answer 43

60mmHg or 8kPa

Question 44

CO2 partial pressure gradient

Answer 44

6mmHg or 0.8kPa

Question 45

What happens to the rate of gas exchange in the lungs as the partial pressure gradients increase

Answer 45

increases

Question 46

What is meant by diffusion coeffient

Answer 46

solubility of gas in the membrane

Question 47

What results in decreased surface area in the lungs

Answer 47

emphysema | lung collapse

Question 48

Increases thickness in lings

Answer 48

Fibrosis Oedema Pneumonia

Question 49

reduced lung perfusion

Answer 49

PE

Question 50

Define cardiac output

Answer 50

Volume of blood pumped by each ventricle per minute is known as the CO

Question 51

What is the resting CO in a healthy adult

Answer 51

5 litres per minute (70ml SV x 70 bpm= 4900ml)

Question 52

Define stroke volume

Answer 52

the volume of blood ejected by each ventricle per heart beat

Question 53

Calculate Stroke volume

Answer 53

SV= end diastolic volume - end systolis volume

Question 54

What determines the cardiac preload

Answer 54

end diastolic volume determined by the venous return to the heart

Question 55

Describe frank starling law

Answer 55

“the more the ventricle is filled with blood during diastole (END DIASTOLIC VOLUME), the greater the volume of ejected blood will be during the resulting systolic contraction (STROKE VOLUME)