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Cardiorespiratory (MEDI301) > Week 3-4 > Flashcards

Week 3-4 Flashcards

1
Q

What factors affect heat storage?

A

Metabolism - work - evaporation +/- conduction +/- convection +/- radiation

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2
Q

What is conduction?

A

The transfer of heat to a moving gas or liquid

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3
Q

What are the effectors to decrease temperature?

A

Skin blood vessels (dilate)
Sweat glands
Endocrine tissue
Behaviour

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4
Q

What are the effectors to increase temperature?

A 
Skin blood vessels (constrict)
Arrector pili muscles
Skeletal muscles
Endocrine tissue
Behaviour
Brown adipose tissue
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5
Q

Where are the central chemoreceptors found?

A

Hypothalamus (preoptic anterior hypothalamus)
Spinal cord
Viscera
Great veins

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6
Q

Where are the peripheral thermoreceptors?

A

Skin, oral and urogenital mucosa

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7
Q

How is temperature information conveyed to the brain?

A

Spino-thalamo-cortical pathway > discriminative temperature sensation
Spino-reticulo-hypothalamic pathway > thermoregulation

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8
Q

What pathway is responsible for discriminative temperature sensation?

A

Spino-thalamo-cortical pathway

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9
Q

What pathway is responsible for sensation for thermoregulation?

A

Spino-reticulo-hypothalamic pathway

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10
Q

What is the classical model of thermoregulation?

A

Proposes a set point for temperature control:

The hypothalamus compares temperature signals to a set point

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11
Q

What is non-shivering thermogenesis?

A

Heat is produced by brown adipose tissue, via mitochondrial uncoupling

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12
Q

What 3 factors does stroke volume depend on?

A

Preload
Contractility
Afterload

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13
Q

What is preload?

A

The degree of stretch of cardiomyocytes prior to contraction

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14
Q

What influences contractility?

A

Sympathetic nerve activity

Frank-Starling mechanism

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15
Q

Core body temperature range?

A

36 - 37.5’C

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16
Q

When can core body temperature measurements vary?

A

Time of day (cooler in evening)
Time of month (higher in luteal phase)
Age
Pathology

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17
Q

What is the role of thermoregulation?

A

Maintain core body temperature

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18
Q

What 3 factors are the rate of evaporation dependent on?

A

Temperature and relative humidity
Amount of skin surface
convective currents around the body

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19
Q

The majority of central thermoreceptors are…

A

Warm-sensitive neurons

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20
Q

The majority of peripheral thermoreceptors are…

A

Cold-sensitive neurons.

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21
Q

How do cold-sensitive peripheral thermoreceptors transmit impulses?

A

Via thin myelinated A-delta fibres

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22
Q

How do warm-sensitive peripheral thermoreceptors convey impulses?

A

Via unmyelinated C fibres

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23
Q

What are TRPs?

A

Transient receptor potential ion channels: a superfamily of proteins expressed in cell membranes.
Subtypes for specific temperature ranges

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24
Q

Where does information from skin afferents (cold and warm) enter the spinal cord?

A

Dorsal horn (lamina I)

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25
Q

Outline the spino-reticulo-hypothalamic pathway (for thermoregulation)

A

Second-order neurons (lamina I)
> lateral parabrachial nucleus reticular formation
» median preoptic nucleus (hypothalamus)

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26
Q

What is sweating activated by?

A

Sympathetic cholinergic nerves

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27
Q

How is vasodilation achieved to regulate the core body temperature?

A

Initially: withdrawal of noradrenergic sympathetic vasoconstriction
Later: cholinergic sympathetic nerves

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28
Q

What happens if heat loss mechanisms fail?

A

Heatstroke
Seizures
Brain, liver and kidney damage
Death (extreme)

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29
Q

How is vasoconstriction achieved to regulate the core body temperature?

A

Adrenergic sympathetic nerves

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30
Q

What is piloerection?

A

Goosebumps

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31
Q

How is piloerection evoked?

A

By an increase in sympathetic neural discharge to skin: alpha-1-adrenergic response

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32
Q

Where is brown adipose tissue located?

A 
Supraclavicular region
Neck
Mediastinum
Para-aortic region
Supra-renal region
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33
Q

What does brown adipose tissue do regarding thermoregulation?

A

Is the site of non-shivering thermogenesis: the cells make heat via mitochondrial uncoupling

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34
Q

Approximately how much ATP is stored in the body?

A

250g

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35
Q

What are the 7 factors affecting the maximal oxygen consumption rate?

A 
Age
Genetics
State of physical health
Environment
Mode of activity performed
Gender
Intensity and volume of training
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36
Q

What are the 3 adjustable factors affecting the maximal oxygen consumption rate?

A

State of physical health
Mode of activity performed
Intensity and volume of training

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37
Q

What are the 3 physiological determinants of the maximal oxygen consumption rate?

A

Lungs
Heart
Muscle

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38
Q

What is the Fick Principle?

A

An equation determining the maximal oxygen consumption rate:

V.O2max = cardiac output x (difference on the contents of O2 in the arterial and venous blood)

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39
Q

What determines cardiac output?

A

Heart rate x stroke volume

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40
Q

What is stroke volume dependent on?

A

Contractility and end-diastolic volume

Negatively by afterload?

41
Q

What is an ionotrope?

A

An agent that alters the force/strength of a muscular contraction

42
Q

What ionotropes contribute to increased contractility of the heart?

A

Catecholamines: noradrenaline and adrenaline

Beta-agonists

43
Q

What is blood pressure dependent on?

A

Cardiac output x total peripheral resistance

44
Q

What contributes to an increase in heart rate up to 100bpm?

A

Vagal withdrawal

45
Q

What contributes to an increase in heart rate above 100bpm?

A

Sympathetic drive

46
Q

What contributes to an increase in end-diastolic volume, and hence to an increase in stroke volume (during exercise)?

A

Venoconstriction in splanchnic vessels
Skeletal muscle pump
Respiratory pump

47
Q

What 3 factors contribute to increased cardiac contractility during exercise?

A

Increased circulating catecholamines (NE and E)
Increased sympathetic nerve activity
Increased heart rate (Bowditch effect, minimal)

48
Q

What changes in blood pressure occur during moderate intensity exercise?

A

Increase in systolic,
Decrease in diastolic,
Slight increase in Mean Arterial Pressure

49
Q

What direct and indirect vasodilatory influences occur in skeletal muscle during exercise?

A

Increased H+/lactate
Increased K+
Increased CO2, decreased O2
Endothelial-derived vasodilator factors e.g. nitric oxide

50
Q

How is O2 extraction increased in exercising muscle?

A

Increased capillary density
Increased myoglobin
Increased mitochondrial density
Increase in oxidative enzymes (making ATP)

51
Q

What are the 5 core components considered when designing a cardiorespiratory exercise programme?

A 
Mode
Intensity
Frequency
Duration
Progressive

Also safety

52
Q

What is sarcopenia?

A

Muscle loss with ageing

53
Q

Role of muscular/medium arteries

A

Allow vessels to regulate blood supply by constricting or dilating (smooth muscle)

54
Q

Outline the vasodilator theory of local response to low oxygen

A

Decreased oxygen concentration in blood
> increased vasodilator substance formation
» increased diffusion of vasodilators to interstitial fluid
»> decreased resistance at local precapillary sphincters and metarterioles

55
Q

What is reactive hyperaemia?

A

Blood flow is blocked to a tissue. Increased vasodilatory metabolites > decreased resistance
When blood flow is restored, large compensatory blood flow is received due to vasodilated capillary bed.
Causes increased stress on endothelium&raquo_space; release of NO&raquo_space;> further dilation

56
Q

What is active hyperaemia?

A
  1. Increased metabolic demand due to increased tissue activity
  2. Vasodilator substances formed by metabolism
  3. Vasodilation > decreased resistance&raquo_space; increased blood flow
57
Q

Outline the oxygen/nutrient demand theory of local response to low oxygen

A

Oxygen is required for smooth muscle contraction, therefore if there is too little oxygen in the blood, the smooth muscle will dilate resulting in lower resistance

58
Q

What are the 2 theories regarding acute local control of blood flow?

A

Vasodilator theory

Oxygen/nutrient demand theory

59
Q

What are 2 examples of the vasodilator theory of local response to low oxygen?

A

Reactive hyperaemia

Active hyperaemia

60
Q

In which tissues is autoregulation of local blood flow especially important?

A

Brain

Heart muscle

61
Q

Outline the metabolic theory of autoregulation of blood flow

A
  1. Increased blood pressure
  2. Increased blood flow
  3. Decreased metabolite concentration
  4. Decreased vasodilation
  5. Increased resistance
  6. Decreased blood flow
62
Q

Outline the myogenic theory of autoregulation of blood flow

A

Sudden stretch of vessel wall
> stretch opens Ca++ channels
» smooth muscle contracts

63
Q

What 3 mechanisms/reflexes affect contractility of the heart muscles?

A

Bainbridge reflex
Bowditch effect
Frank-Starling mechanism

64
Q

Explain the Frank-Starling Mechanism

A

Increase in venous return
> increased volume of blood in ventricles after diastole
» increased cardiac contractility
»> increased cardiac output

65
Q

Explain the Bainbridge Reflex

A

Increased atrial pressure
> increased cardiac contractility
» increased heart rate

66
Q

Explain the Bowditch Effect

A

Increased heart rate (during exercise)

> increased contractility

67
Q

How is cardiac contractility decreased?

A

Parasympathetic (vagal) STIMULATION

Sympathetic INHIBITION

68
Q

How is cardiac contractility increased?

A

Catecholamines and beta-agonists
Sympathetic STIMULATION
Increased venous return (Frank-Starling Mechanism)
Increased heart rate during exercise (Bowditch Effect)
Increased atrial pressure (Bainbridge Reflex)

69
Q

Vasoconstrictor nerve terminals release predominantly which chemical?

A

Norepinephrine

70
Q

How does norepinephrine act to contract smooth muscle and vasoconstrict?

A

Acts on alpha adrenergic receptors of smooth muscle

71
Q

What effect does sympathetic stimulation have on the adrenal medulla?

A

Stimulates the secretion of epinephrine and norepinephrine

72
Q

Explain the volume reflex

A

Stretching of the atria
> kidney arterioles dilate, increasing fluid filtration
» hypothalamus reduces ADH production

73
Q

What’s the difference between atherosclerosis and arteriosclerosis?

A

Atherosclerosis - a blood vessel is partially or totally occluded due to plaque formation in the vessel wall.
Arteriosclerosis - the elasticity of the blood vessel walls is reduced, resulting in a reduction of the Windkessel effect

74
Q

How is afterload increased? What effect does it have?

A

Constricting blood vessels

> impairs pumping

75
Q

Define oxygen consumption (VO2)

A

The amount of oxygen taken up by the lungs.

76
Q

Define cellular oxygen consumption

A

The amount of oxygen taken up/used by the cells

77
Q

When are oxygen consumption and cellular oxygen consumption equal?

A

When the body is at a steady state.

78
Q

Define maximum oxygen consumption (VO2max)

A

The maximal amount of oxygen the body can take up

79
Q

The endothelium has a role in…

A 
Mechanics of blood flow
Regulation of coagulation
Leukocyte adhesion
Vascular smooth muscle growth
Barrier to transvascular diffusion of liquids and solids
80
Q

What are the 3 classifications of capillaries based on permeability?

A

Continuous
Fenestrated
Sinusoidal

81
Q

What are sinusoidal capillaries?

A

Capillaries with a large diameter and large fenestrae

Present in liver especially

82
Q

What are intercellular clefts and what is their function in capillaries?

A

Channel between 2 adjacent endothelial cells

Transport of water and soluble ions

83
Q

What are caveolae and what is their function in capillaries?

A

Plasmalemma vehicles - vesicles made of caveolins (proteins associated with cholesterol and sphingolipids)
Transport larger molecules e.g. proteins, can form vesicular channels

84
Q

What is caveolin?

A

A protein associated with cholesterol and sphingolipids

Makes caveolae

85
Q

What are the 4 mechanisms for long-term local blood pressure regulation?

A

Angiogenesis
Collateral circulation
Eutrophic remodelling of small blood vessels
Hypertrophic remodelling of large blood vessels

86
Q

How does collateral circulation contribute to long-term local blood pressure regulation?

A

New blood vessels formed around a blocked vessel

Dilation of existing collaterals

87
Q

Explain hypertrophic remodelling of large blood vessels due to increased blood pressure.

A

Increase in size and number of vascular smooth muscle cells

Cross-linking of collagen and fragmentation of elastin in ECM

88
Q

Give examples of vasodilatory metabolites associated with local control of blood flow

A 
Adenosine (from ATP degradation)
Adenosine phosphates
CO2
K+ ions
H+ ions (from lactic acid)
89
Q

What is net filtration pressure in a capillary determined by?

A

+ Capillary pressure
+ Interstitial colloid osmotic pressure
- Interstitial fluid pressure
- Plasma colloid osmotic pressure

90
Q

What is the Starling hypothesis?

A

That the net filtration across a capillary wall is approximately zero i.e. that the filtration and reabsorption is approximately equal

91
Q

What are the 3 elements making up the interstitium?

A

Solid (collagen, proteoglycan fibres)
Gel (like plasma)
Liquid (small channels)

92
Q

What is the function of the lymphatic system?

A

Reabsorb extravascular proteins, colloids etc. and return to circulation

93
Q

What is peripheral vascular disease?

A

Atherosclerosis of peripheral arteries resulting in stenosis/thrombosis/embolism/aneurysm

94
Q

Name 4 retinal vascular diseases

A

Haemorrhage
Cotton wool spots
Microaneurysm
Retinal artery occlusion

95
Q

Define lymphoedema

A

Swelling of the tissue due to inadequate lymphatic drainage.

Doesn’t have to be lymphatic, can be due to any imbalance of Starling forces

96
Q

Name 3 primary lymphoedema conditions

A 
Distal obliteration (ankle, onset at puberty, affects females)
Proximal obliteration (leg, any age)
Congenital hyperplasia (leg, at birth and progressive)
97
Q

What are the current treatments for lymphedema?

A

Exercise
Massage
Pneumatic compression
Compression garments

98
Q

What signals govern the cardiac output during constant workload exercise?

A
  1. central command, vagal withdrawal, muscle pump, sensory nerve activity due to movement
  2. vasodilation in active muscle, stimulation of cardiovascular system (vasodilator factors)
  3. baroreceptor reflex stabilisation

Cardiorespiratory (MEDI301) (3 decks)

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