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foundations of medicine 3 > physiology > Flashcards

physiology Flashcards

1
Q

what are the 5 components needed for effective gas exchange / respiration

A
  • controller
  • ventilatory pump
  • gas exchanger
  • cardiovasc system
  • enough haemoglobin
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2
Q

what is the role of the respiratory controller

A

determines the rate and depth of breathing via efferent signals sent to the resp muscles from resp centres

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3
Q

where are the respiratory centres found

A

in the brain stem

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4
Q

what is respiration modified by

A

inputs from the pons

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5
Q

where is respiratory rhythm generated

A

medulla

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6
Q

what is the role juxtapulmonary receptors

A

protect against hyperinflation

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7
Q

where are peripheral chemoreceptors found

A

carotid bodies - at the bifurcation of the common carotid arteries
aortic bodies - along the aortic arch

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7
Q

what happens to ventilation in response to decreased blood pressure

A

increased rate of ventilation

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8
Q

what is the role of peripheral chemoreceptors

A

sense tension of oxygen and carbon dioxide and [H+] in the blood

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9
Q

where are central chemoreceptors found

A

near the surface of the medulla of the brainstem

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10
Q

what do central chemoreceptors respond to

A

the [H+] of CSF

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11
Q

what is the most potent stimulant of respiration

A

arterial PCO2 acting through central chemoreceptors
(increased [H+] in CSF)

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12
Q

which part of the respiratory system is activated in hypoxic drive

A

peripheral chemoreceptors

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13
Q

when is hypoxic drive clinically important (2)

A

in patients with chronic CO2 retention
high altitudes

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14
Q

give an example of a condition which causes chronic CO2 retention

A

COPD

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15
Q

what happens when peripheral chemoreceptors are stimulated by increased [H+]

A

hyperventilation to increase the elimination of CO2 from the body

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16
Q

name some factors that can affect the ventilatory pump of respiration

A

neuromuscular weakness
decreased compliance
loss of pressure gradient
increased airway resistance

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17
Q

what condition can cause a loss of pressure gradient across the lungs

A

pneumothorax

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18
Q

name 2 conditions which can cause increased airway resistance

A

asthma, COPD

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19
Q

what is the bucket handle mechanism

A

external intercostal muscle contraction lifts the ribs and moves out the sternum

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20
Q

how is the volume of the thorax increased vertically during inspiration

A

contraction of the diaphragm

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21
Q

what nerve is involved in contraction of the diaphragm

A

phrenic nerve from C3,4 and 5

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22
Q

what are the major muscles of inspiration

A

external intercostal and diaphragm

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23
Q

what are the accessory muscles of inspiration

A

sternocleidomastoid
scalenus

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24
Q

what are the muscles of active expiration

A

internal intercostal muscles
abdominal muscles

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25
Q

what happens to pressure in the lungs during inspiration

A

intra-alveolar drops below atmospheric
intrapleural becomes more negative

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26
Q

which forces keep alveoli open

A

transmural pressure gradient
pulmonary surfactant
alveolar interdependence

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27
Q

which forces promote alveolar collapse

A

elasticity of stretched pulmonary connective tissue fibres
alveolar surface tension

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28
Q

what does parasympathetic stimulation of the airways cause

A

bronchoconstriction

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29
Q

what does sympathetic stimulation of the airway cause

A

bronchodilation

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30
Q

what is the main determinant of airway resistance

A

radius of the conducting airway

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31
Q

what happens to intrapleural pressure during expiration

A

rises

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32
Q

when does dynamic airway compression occur

A

during forced expiration

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33
Q

who do we worry about with dynamic airway compression

A

people with obstructive lung disease

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34
Q

what can be the clinical sign of dynamic airway compression in obstructive lung disease

A

wheeze or prolonged expiration

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35
Q

what is the consequence of dynamic airway compression in a patient with obstructive lung disease

A

airway collapse

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36
Q

what can also make dynamic airway compression worse

A

decreased elastic recoil

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37
Q

what is pulmonary compliance

A

the measure of effort that has to go in to stretching the lungs

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38
Q

what does the wall of an alveolus consist of

A

single layer of flattened type I alveolar cells

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39
Q

name conditions which reduce the surface area for gas exchange

A

emphysema
lung collapse

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40
Q

what is cardiac output

A

the volume of blood pumped by each ventricle per minute

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41
Q

what is the equation for cardiac output

A

stroke volume x heart rate

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42
Q

what is stroke volume

A

the volume of blood ejected by each ventricle per heartbeat

43
Q

what is the equation for stroke volume

A

end diastolic volume - end systolic volume

44
Q

how are changes in stoke volume brought about

A

changes in the diastolic length of myocardial fibres

45
Q

what is diastolic length of myocardial fibres determined by

A

end diastolic volume

46
Q

what is cardiac preload

A

the extent to which the left ventricular wall stretches at the end of diastole, or before systole starts

47
Q

what determines the end diastolic volume

A

venous return

48
Q

what does left sided heart failure cause

A

pulmonary capillary congestion and pulmonary oedema

49
Q

what is the primary factor which determines the percent saturation of haemoglobin with O2

A

PO2

50
Q

effect of anaemia on oxygen saturation curve

A

normal shape but doesn’t reach maximum oxygen saturation

51
Q

what is tidal volume

A

the volume of air entering or leaving the lungs during a breath

52
Q

what is inspiratory reserve volume

A

the extra volume of air that can be maximally inspired above the tidal volume

53
Q

what is inspiratory capacity

A

tidal volume + inspiratory reserve volume
the maximum volume of air that can be inspired at the end of normal expiration

54
Q

what is expiratory reserve volume

A

extra volume of air that can be breathed out after tidal volume

55
Q

what is residual volume

A

the minimum volume of air left in the lungs after maximum expiration

56
Q

what is functional residual capacity

A

the volume of air in the lungs at the end of normal passive expiration

57
Q

what is vital capacity

A

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

58
Q

what is total lung capacity

A

the maximum volume of air that the lungs can hold

59
Q

what is forced expiratory volume

A

volume of air that can be expired during the first second of expiration

60
Q

what is FEV1:FVC ratio normally

A

> 75%

61
Q

what is FEV1:FVC ratio in an asthmatic patient

A

<75%

62
Q

how do we identify the difference between FEV1:FVC ratio in a patient with COPD compared to asthma

A

asthmatic patients will respond to a bronchodilator

63
Q

what classification is used to assess airflow limitation in COPD

A

GOLD (1-4)

64
Q

FEV1:FVC ratio in restrictive lung disease

A

normal as both are low

65
Q

why do people complain of tingling during anxiety/hyperventilation

A

hyperventilation causes respiratory alkalosis
this causes decreased ionised calcium - as it binds to albumin if pH increases
decreased ionised calcium results in increased nerve excitability

66
Q

what does a low pO2 cause the lungs to do

A

pulmonary vasoconstriction

67
Q

why can’t we give excessive oxygen to COPD patients with chronic CO2 retention

A

can lead to hypercapnic respiratory failure

68
Q

what happens to pulmonary compliance in a patient with emphysema

A

increases

69
Q

why do lungs collapse in pneumothorax

A

increased intrathoracic pressure abolishes the transmural pressure gradient

70
Q

physical sign of a pneumothorax

A

hyperresonant percussion and decreased/absent breath sounds

71
Q

how do we calculate oxygen delivery index

A

oxygen content of arterial blood x cardiac index

72
Q

which 2 factors determine O2 content of arterial blood

A

haemoglobin concentration and its saturation with oxygen

73
Q

what is homeostasis

A

maintaining near constant internal environment

74
Q

what is the primary type of homeostatic control mechanisms in the human body

A

negative feedback

75
Q

how do negative feedback mechanisms work

A

oppose initial changes in environment

76
Q

what is the importance of negative feedback loops in the body

A

promote stability by regulation of variables within a narrow range

77
Q

what are the 3 main components of a negative feedback mechanism

A

sensor, control centre and effectors

78
Q

what happens to thermoregulation in fever

A

a cold response raises the body temp to a new set point

79
Q

where can we take an indirect estimate of core body temperature

A

ear drum

80
Q

normal temperature range

A

36-37.5

81
Q

fever range

A

38-40

82
Q

hyperthermia range

A

> 40

83
Q

where can we take a direct estimate of core body temperature (2)

A

rectum or oesophagus

84
Q

hypothermia range

A

<35

85
Q

name the 4 ways in which the body can lose heat

A

radiation
conduction
convection
evaporation

86
Q

name the 3 ways in which the body can gain heat

A

radiation
convection
conduction

87
Q

name some hormones which can increase BMR

A

adrenaline, noradrenaline, thyroxine

88
Q

where is the control centre for thermoregulation

A

hypothalamus

89
Q

where are central thermoreceptors mostly found

A

hypothalamus, abdominal organs

90
Q

where are peripheral thermoreceptors found

A

in the skin

91
Q

what are the effectors in thermoregulation (3)

A

skeletal muscles
skin arterioles
sweat glands

92
Q

what part of the hypothalamus is activated by cold

A

posterior hypothalamic centre

93
Q

which part of the hypothalamus is activated by warmth

A

anterior hypothalamic centre

94
Q

how is set point raised in a fever

A

chemicals from macrophages act as endogenous pyrogens
stimulate the release of prostaglandins from the hypothalamus
hypothalamus initiates mechanisms to heat the body e.g. shivering
temp increases to reach the new set point

95
Q

what is the response of skeletal muscles to warmth

A

decreased tone

96
Q

what is a motor unit

A

a single alpha motor neuron and all the skeletal muscle fibres it innervates

97
Q

what is the functional unit of a muscle

A

sarcomeres

98
Q

what is the name of the thin muscle filament

A

actin

99
Q

what is the name of the thick muscle filament

A

myosin

100
Q

what are actin and myosin arranged into

A

sarcomeres

101
Q

what is a segment of actin and myosin called

A

myofibril

102
Q

where is calcium released from in muscle contraction

A

lateral sacs of the sarcoplasmic reticulum

103
Q

what causes calcium release during muscle contraction

A

action potential in the T tubules

104
Q

what is the role of calcium in muscle contraction

A

binds to troponin on actin filaments
causes tropomyosin to be moved out the wat to uncover cross-bridge binding sites on actin

105
Q

what is the neurotransmitter at the NMJ

A

acetylcholine

106
Q

when is ATP needed in muscles

A

during contraction to power cross bridges
during relaxation to release cross bridges and pump calcium back into the SR

foundations of medicine 3 (6 decks)

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