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Transition Block > Physiology > Flashcards

Physiology Flashcards

1
Q

Where is respiratory rhythm generated

A

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

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2
Q

What part of the brain stem modifies respiration

A

pons

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3
Q

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

A

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

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4
Q

Where are central chemoreceptors located

A

near the surface of the medulla

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5
Q

What do central chemoreceptors respond to

A

the hydrogen in the CSF

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6
Q

Why is CSF less easily buffered than blood

A

contains less protein

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7
Q

Can CO2 diffuse across the blood brain barrier

A

Yes - readily

Hydrogen and carbonate ions do not diffuse easily across the BBB

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8
Q

What will happen to the resp rate when there is hypercapnia

A

Hyperventilation

ie increases

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9
Q

What is the most potent stimulation of resp in most people

A

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

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10
Q

Where are peripheral chemoreceptors situated

A

Carotid and aortic bodies

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11
Q

What do peripheral chemoreceptors sense

A

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

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12
Q

What initiates the hypoxic drive effect

A

peripheral chemoreceptors sensing low PO2 (less than 8kPa)

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13
Q

In what group of patients is their hypoxic drive important

A

COPD due to chronic CO2 retention

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14
Q

In what other circumstances is hypoxic drive important

A

high altitudes

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15
Q

What happens in the hypoxic drive

A

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

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16
Q

What mediated the H+ drive of respiration

A

peripheral chemoreceptors

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17
Q

What does an increase in H+ cause

A

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

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18
Q

In what circumstances may hydrogen ions be increased in the blood

A

DKA

exercise -lactic acidosis

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19
Q

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
A
  1. peripheral chemoreceptors
  2. central chemoreceptors
  3. peripheral chemoreceptors
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20
Q

What reflex guards against hyperinflation of the lungs

A

Herin-breur reflex

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21
Q

What stimulates juxtapulmonary receptors

A

pulmonary circulation congestion and oedema

PE

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22
Q

what stimulated baroreceptors

A

increased ventilation rate in response to low BP

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23
Q

What muscles move the ribs up and out

A

External intercostal muscles

24
Q

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

A

Diaphragm

Phrenic nerve - C3, 4, 5

25
Q

Accessory muscle of inspiration

A

SCM

Scalenus

26
Q

Muscles of active expiration

A

Abdominal muscles

Internal intercostal muscles

27
Q

Major muscle of inspiration

A

Diaphragm

External intercostal muscles

28
Q

What three pressures are important in the lungs

A

Atmospheric and Intra alveolar = usually the same

Intrapleural

29
Q

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

A

less

30
Q

What happens to intra alveolar and intrapleural pressure during inspiration

A

both decrease

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

31
Q

What happens to intra alveolar and intra pleural pressure during expiration

A

both increase

32
Q

In what circumstance is the transmural pressure gradient abolished

A

pneumothorax

33
Q

Forces which keep alveoli open

A

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

34
Q

Forces promoting alveolar collapse

A

Elasticity of stretch pulmonary connective tissue fibres

Alveolar surface tension

35
Q

What stimulation causes bronchoconstriction and what causes bronchodilation

A 
Parasympathetic = constriction
Sympathetic = dilation
36
Q

what diseases cause airway floow restirction

A

COPD and asthma

37
Q

what does increased airway resistance result in

A

expiration is more difficult than inspiration

lungs hyperinflate

38
Q

What happens in dynamic airway compression

A

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

39
Q

What is meant by compliance

A

The effort needed to inflate the lungs

i.e. less compliant lungs require more work to produce a given degree of inflation

40
Q

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

A

pulmonary fibrosis

41
Q

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

A

3 percent

42
Q

What cells line the alveoli

A

Type 1 alveolar cells - single layer

43
Q

O2 partial pressure gradient

A

60mmHg or 8kPa

44
Q

CO2 partial pressure gradient

A

6mmHg or 0.8kPa

45
Q

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

A

increases

46
Q

What is meant by diffusion coeffient

A

solubility of gas in the membrane

47
Q

What results in decreased surface area in the lungs

A

emphysema

lung collapse

48
Q

Increases thickness in lings

A

Fibrosis
Oedema
Pneumonia

49
Q

reduced lung perfusion

A

PE

50
Q

Define cardiac output

A

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

51
Q

What is the resting CO in a healthy adult

A

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

52
Q

Define stroke volume

A

the volume of blood ejected by each ventricle per heart beat

53
Q

Calculate Stroke volume

A

SV= end diastolic volume - end systolis volume

54
Q

What determines the cardiac preload

A

end diastolic volume determined by the venous return to the heart

55
Q

Describe frank starling law

A

“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)

Transition Block (2 decks)

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