Physiology

Question 1

4 steps of external respiration

Answer 1

Ventilation
Gas exchange between alveoli and blood
Gas transport in blood
Gas exchange at tissue level

Question 2

Ventilation

Answer 2

The mechanical process of moving air between the atmosphere and alveolar sacs

Question 3

Boyle’s law

Answer 3

As the volume of gas increases the force expected by the gas decreases

Question 4

Two forces which make lungs and thorax move together

Answer 4

1. Intrapleural fluid cohesiveness

2. Negative intrapleural pressure - lungs push outwards, chest squeezes inward

Question 5

What does the external intercostal muscle do?

Answer 5

Lift the ribs and move the sternum out

Question 6

alveolar surface tension

Answer 6

Attraction between water molecules at liquid air interference

Question 7

LaPlace Law

Answer 7

P = 2T/r i.e. smaller alveoli have a higher tendency to collapse

Question 8

What is causes respiratory distress syndrome in a newborn

Answer 8

Lack of surfactant

Question 9

3 forces that keep the alveoli open

Answer 9

Transmural pressure gradient
Pulmonary surfactant
Alveolar interdependance

Question 10

2 forces which promote alveolar collapse

Answer 10

Elasticity of stretched pulmonary connective tissue fibres

Alveolar surface tension

Question 11

Accessory muscles of inspiration

Answer 11

Sternocleidomastoid

Scalenus

Question 12

Major muscles of inspiration

Answer 12

External intercostal muscles

Diaphragm

Question 13

Muscles of active expiration

Answer 13

Internal intercostal muscles 
Abdominal muscles (TIRE)

Question 14

Tidal volume

Answer 14

Volume of air entering or leaving the lungs during a single breath

Question 15

Inspiratory reserve volume

Answer 15

Extra volume of air that can be maximally inspired over and above the typical resting tidal volume

Question 16

Inspiratory capacity

Answer 16

Maximum volume of air that can be inspired after a normal expiration

Question 17

Expiratory reserve volume

Answer 17

Extra volume of air that can be actively expired by maximal contraction beyond the normal volume of air after a resting tidal volume

Question 18

Residual volume

Answer 18

Minimum volume of air remaining in the lungs after maximal expiration

Question 19

Vital capacity

Answer 19

Maximum volume of air that can be moved out during a single breath following maximal inspiration

Question 20

Total lung capacity

Answer 20

Maximum volume of air that the lungs can hold = VC + RV

Question 21

Forced Vital capacity

Answer 21

The volume of air that can be forcefully expelled following maximal inspiration

Question 22

Forced Expiratory Volume in 1 sec (FEV1)

Answer 22

The volume of air that can be expelled during the first second of expiration

Question 23

Spirometry results for obstructive lung disease

Answer 23

FVC = Normal
FEV1 = Low
FEV1/FVC% = low

Question 24

Spirometry results for restrictive lung disease

Answer 24

FVC = Low
FEV1 = Low
FEV1/FVC% = Normal

Question 25

What happens to intrapleural pressure during inspiration

Answer 25

Falls - diaphragm moves down

Question 26

What happens to intrapleural pressure during expiration

Answer 26

Rises - diaphragm moves up

Question 27

Compliance

Answer 27

A measure of the effort that has to go into stretching to distending the lungs

Question 28

What decreases pulmonary compliance?

Answer 28

``` Pulmonary fibrosis Pulmonary oedema Lung collapse Pneumonia Absence of surfactant ```

Question 29

Decreased pulmonary compliance on spirometry?

Answer 29

Restrictive

Question 30

Increased compliance

Answer 30

Emphysema - patients have to work harder to get air out of the lungs Age

Question 31

Increase in work of breathing

Answer 31

Decreased pulmonary compliance Increased airway resistance Decreased elastic recoil Increased ventilation

Question 32

Pulmonary Ventilation

Answer 32

Tidal volume x respiratory rate

Question 33

Alveolar ventilation

Answer 33

(tidal volume - dead space) x respiratory rate

Question 34

What represents new air available for gas exchange within the blood

Answer 34

Alveolar ventilation - volume of air exchanged between atmosphere and alveoli per min

Question 35

Ventilation

Answer 35

The rate at which gas is passing through the lungs

Question 36

Perfusion

Answer 36

The rate at which blood is passing through the lungs

Question 37

Alveolar dead space

Answer 37

ventilated alveoli which are not adequately perfused

Question 38

effects of decreased O2

Answer 38

Pulmonary arterioles vasoconstrict | Systemic arterioles vasodilate

Question 39

Effects of increased O2

Answer 39

Pulmonary arterioles vasodilate | Systemic arterioles vasoconstrict

Question 40

Dalton's law

Answer 40

The total pressure exerted by a gas mixture = the sum of the partial pressures of each individual component in the gas mixture

Question 41

Partial pressure of gas

Answer 41

The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied

Question 42

Fick's Law of diffusion

Answer 42

The amount of gas to pass across a tissue per unit time is directly proportional to its area and inversely proportional to its thickness

Question 43

Henry's law

Answer 43

The amount of a given gas in a given type and volume of liquid is proportional to the partial pressure of the gas in equilibrium with the liquid

Question 44

2 forms of O2 present in the blood

Answer 44

1. Bound to haemoglobin - 98.5% | 2. Physically dissolved - 1.5%

Question 45

What is Po2?

Answer 45

the primary factor which determines the % saturation of haemoglobin with O2

Question 46

Oxygen delivery index

Answer 46

DO2I = CaO2 x Cl

Question 47

What is the O2 content of arterial blood determined by?

Answer 47

Haemoglobin conc. | Saturation of Hb

Question 48

Impairment of O2 delivery to tissue

Answer 48

1. Decreased partial pressure of inspired O2 2. Respiratory disease 3. Anaemia 4. Heart failure

Question 49

Means of CO2 transport in the blood

Answer 49

Solution Bicarbonate Carbamino compounds

Question 50

Which is more soluble - CO2 or O2 in blood

Answer 50

CO2 - 20x more soluble

Question 51

How are carbamino compounds formed?

Answer 51

Combination of CO2 with terminal amine groups in blood proteins

Question 52

Haldane effect

Answer 52

Removing O2 from Hb increased the ability of Hb to pick up CO2 and H+

Question 53

The major rhythm generator of respiration

Answer 53

Medulla

Question 54

Which neurones generate breathing rhythm and where are they located?

Answer 54

Pre-Botzinger complex - near upper end of medullary respiratory centre

Question 55

Which neurones are excited in active expiration?

Answer 55

Ventral respiratory neurones

Question 56

What has to be stimulated to terminate inspiration?

Answer 56

Pneumotaxic centre

Question 57

When is the pneumotaxic centre stimulated?

Answer 57

When dorsal respiratory neurones fire

Question 58

Apneusis

Answer 58

Prolonged inspiratory gasps with brief expiration

Question 59

Which part of the brain modifies rhythm of breathing?

Answer 59

Pons

Question 60

Involuntary modifications of breathing

Answer 60

Pulmonary stretch receptors Joint receptors reflex Stimulation of respiratory centre - temp. or adrenaline Cough reflex

Question 61

When are pulmonary stretch receptors activated?

Answer 61

During inspiration, inhibits it - Hering-Breuer reflex

Question 62

Chemical control of respiration variables

Answer 62

Blood gas tension i.e. CO2

Question 63

Location of peripheral chemoreceptors

Answer 63

Carotid bodies and aortic bodies

Question 64

Location of central chemoreceptors

Answer 64

Surface of medulla

Question 65

What do the central chemoreceptors respond to?

Answer 65

THE concentration of H+ ions of the cerebrospinal fluid

Question 66

Which chemoreceptors are involved in the hypoxic drive?

Answer 66

Peripheral