Cardiorespiratory Flashcards
1
Q
What do you regulate to stay alive?
A
- Ultimately, cellular homeostasis
- Requires regulation of blood: pressure, volume, content, temperature
2
Q
What do you control to stay alive?
A
- Behaviour
- Change posture
- Increase strength of contraction
- Vasoconstrict blood vessels
- Reducing energy and exercise intensity
3
Q
Why is cardiopulmonary function important?
A
- Normal life
- Health
- Performance
- Your ability to supply oxygen to cells (and remove metabolites) governs your ability to work/exercise beyond mere seconds
4
Q
How much can oxygen consumption increase by?
A
- 10 fold in sedentary/inactive
- 20 fold in elite athlete
5
Q
What is the respiratory role of the pulmonary system?
A
Primarily to oxygenate blood and eliminate CO2 from cellular respiration. Is mediated by ventilation of alveoli
6
Q
What is the other roles of the pulmonary system?
A
- Acid:base balance
- Blood reservoir
- Heat dissipation
- Filtration to remove thrombi
- Activates, synthesises or catabolises many chemicals in blood
- Aid stabilisation of trunk/thorax in resistance exercise
7
Q
What is respiration and O2 and CO2 transport processes?
A
- Oxidative metabolism, including transport processes:
- Oxygen: Ventilate –> diffuse –> circulate –> diffuse –> mitochondria
- Carbon Dioxide: Mitochondria –> diffuse –> circulate –> diffuse –> ventilate
8
Q
What is hypernoea?
A
Increase ventilation (more breathing)
9
Q
What is hyperventilation?
A
Over breathing (indicated by decreased CO2 in blood)
10
Q
What is the transport process of ventilation?
A
Trachea –> bronchi –> bronchioles –> terminal bronchioles –> alveolar ducts –> alveoli
11
Q
What is the alveoli made up of?
A
Surfactant, epithelial layer (10% width RBC), high blood supply
12
Q
What are the 3 parts of the respiratory cycle?
A
- Inspiration
- Expiration
- Duty Cycle
13
Q
What is inspiration?
A
- Active process
- Diaphragm and external intercostals
14
Q
What is expiration?
A
- Passive at rest process (active in exercise)
- Abdominal muscles + internal intercostals
- 6x more air in 1/6th of the time (during exercise)
15
Q
What is the duty cycle?
A
1/3 at rest, to 1/2 in exercise
16
Q
What is the work of breathing in exercise?
A
- ~3% energy usage at rest
- ~12-24% energy usage at max exercise
17
Q
Why does breathing hard in exercise become a problem?
A
Because of how much energy and blood flow demand just to support your breathing
18
Q
What is the calculation for ventilation?
A
Breathing frequency x tidal volume
19
Q
How much more volume of air can you hold during maximal exercise?
A
Approximately 3x more L/min. (150L/min)
20
Q
What are the measures of ventilatory performance?
A
- FVC - can be smaller than VC because of airway closure
- FEV1 - time dependent, therefore relates well to exercise (normal >80%)
21
Q
What are the mechanics of breathing?
A
- Pleural pressure is the key feature, if airway resistance is low. The bigger the pressure gradient, the more air that will flow in and out
- Can get early airway closure (especially with forced expiration)
- Some elites maximise pleural pressures, and get laryngeal obstruction
22
Q
What are some similarities and differences between airflow and ventilation?
A
- Cardiac output - as exercise gets harder, things start to ramp up and that happens at different times for different people
- Ventilation is more a body size issue
- Cardiac output is more a heart strength issue
- Airflow increased proportionately more than blood flow
- Your lungs move much larger volumes of air than your heart does with blood
23
Q
What are the two keys stages that dictate exchange of oxygen and carbon dioxide between atmosphere and blood?
A
- Alveolar Ventilation
- Mass flow of air
- Driven by pressure gradient of air - Alveolar-blood transfer
- Diffusion flow of each gas
- Driven by pressure gradient of each gas
24
Q
What is tidal volume?
A
Tidal Volume = Alveolar volume + dead space
Vt = Va + Vd
25
What is dead space?
Does not contribute to gas exchange
26
What is anatomic dead space?
- Due to structural, non alveolar volume of respiratory tract
- It didn't make it, still in your airways somewhere
27
What is physiologic dead space?
- Includes ventilation into alveoli that aren't used for gas exchange, because ventilation of those alveoli is greater than perfusion
- It got there but there was no venous blood there to exchange gases with
- Especially in the upper lung
28
What is alveolar ventilation determined by?
Vå = Va x fb = (Vt - Vd) x fb (Lmin-1)
29
What is alveolar ventilation controlled by?
1. Duration
2. Force (by recruitment & neural frequency)
3. Frequency (fb)
4. Resistance (of airways)
30
What do you do if 'panting' is the aim?
Breathe shallow to avoid over-ventilating alveoli
31
How do you increase alveolar ventilation?
Take deeper breaths as this will double the volume and halve the breathing rate so a bigger proportion is going to the alveoli.
32
What is cyclic ventilation due to?
Inherently rhythmic inspiratory neurons in medial medulla which turn themselves off once you've breathed in
33
What are the stimuli that modify the ventilation cycle?
- Several excitatory & inhibitory stimuli
- Neural stimuli
- Humoral stimuli
- Stimuli act directly or indirectly on this "respiratory centre" in medulla
34
What controls ventilation at rest?
Mainly chemoreceptors (detect chemical state of arterial blood)
35
What are central chemoreceptors?
- localised chemosensitive medullary neurons
- show strong CO2 sensitivity (via pH of CSF)
36
What are peripheral chemoreceptors?
- Carotid & aortic bodies
- Have limited sensitivity to: O2, CO2, H+, Tblood
37
Is oxygen or carbon dioxide more sensitive to ventilation?
More sensitive to CO2 than O2
38
What is the ventilatory response during sustainable exercise?
- Phase 1: Rapid increase @ onset
- Phase 2: Exponential
- Phase 3: Plateau (light-to-moderate exercise only)
- Immediate drop with stopping exercise
- Slower, exponential recovery
39
What are the neurogenic factors that dominate in exercise?
1. Central Command (Feedforward control)
- Motor cortex output "spill-over" irradiates medulla
- Contribute especially to phase 1 & 2 of hyperpneoa response to exercise, and to rapid decline at end exercise
2. Muscle 'Ergoreceptors' (Feedback control)
- Mechanoreceptors (esp. early phase 1 & 2)
- Metaboreceptors (chemoreceptors) (esp. to phase 3 = fine tuning)
3. Other ergoreceptors (esp. fine tuning)
- Intercostal & diaphragm spindles
- Heart mechanoreceptors (pressure)
- Lung CO2 (flow)
- Lungs and airways
- Temperature
40
What happens to your ventilation during non-sustainable exercise?
- Rises rapidly
- Disproportional to oxygen use
- Fails to stabilise
- Stays elevated in recovery (likely driven by acidosis in muscle and blood)
41
What happens to your CO2 production during non-sustainable exercise?
- CO2 production rises markedly
- Produce more CO2 than O2 used
- This excess CO2 is produced by way of buffering H+ from muscle: CO2 + H20 --> H2CO3 --> H+ + HCO3
42
What happens to ventilation during resistance exercise?
- Increased expiratory force during exertion
- Block glottis (= valsalva manoeuvre) when heavy efforts
- Functions to stiffen trunk/thorax
- Also increase central venous and arterial pressures
- Surges in brain blood flow
- Increased risk for blackout
43
At a given relative exercise load, athletes have?
- Less increase in ventilation
- Less acidity
Likely due to:
- Decrease in type II fibres
- Increase recruit type I fibres
- Increase H+ buffering
44
What does the extent of gas dissolving into a fluid depend on?
- Pressure
- Solubility
- Temperature
- Time
45
What is fick's law of diffusion?
Gas diffusion rate = Area/thickness x D x (P1-P2)
- Can improve gas exchange by increasing pressure gradient
46
What is dalton's law?
Gas x total pressure of gas mixture = partial pressure
47
What is the partial pressure of O2, CO2 and N2?
- O2: 159mmHg
- CO2: 0.2mmHg
- N2: 600mmHg
48
Is O2 or CO2 more soluble?
- CO2 is 24x more soluble than O2
- CO2 is very soluble, so small pressure gradient will allow equivalent exchange rate
49
What happens to oxygen in a hard working muscle?
When a muscle is working hard, its using a lot of oxygen which reduces the pressure of the oxygen in the local tissue and therefore increases the gradient to drive oxygen down more rapidly
50
How is Oxygen transported in the blood?
- Oxygen is poorly soluble in blood
- Almost all (99%) of O2 is bound to haemoglobin
51
How much of your arterial blood is oxygen?
1/5th
52
How much oxygen is offloaded to tissues at rest?
~25%
53
How much oxygen is offloaded to tissues during exercise?
~80-90%
54
How is the oxygen pressure gradient maintained?
The oxygen will diffuse down its pressure gradient into the solution and then continue to diffuse into the RBC which then gets taken up and bound to hb, therefore it is no longer in the solution which keeps the gradient going. This keeps going until almost every available binding site has been bound (~100% saturated)
55
What are 4 interdependent pulmonary factors that can limit exercise?
1. Desaturation of O2
2. High airway resistance (COPD)
3. Pulmonary pressure effects on cardiac output
4. High work of breathing (respiratory muscle fatigue, increase sympathetic outflow, can limit blood flow to locomotive muscles)
56
Why does arterial blood desaturate during intense exercise?
- Limited ventilation (airway resistance within and outside the thorax)
- Short transit time
- More ventilation: perfusion mismatch at high intensities
- Maybe blood shunting
57
How is CO2 transported?
- 5-10% dissolved in plasma (establishes PCO2, tightly regulated)
- 20% bound to Hb (4 per Hb)
- 60-80% as bicarbonate
58
What is the CO2 equation?
H+ + HCO3 <---> H2CO3 <---> CO2 + H2O
59
What is the bohr effect?
The affiliation of oxygen and haemoglobin
60
In the bohr effect, what will make the curve shift down to right (=favour offload)?
- Increased temperature
- Decreased pH
- Increased CO2
61
What is 2,3 DPG?
- Produced in the RBC as byproduct of glycolysis
- Similar to Bohr effect
- Higher in altitude, exercise, anaemia, females
62
How much oxygen does 1g of haemoglobin carry?
1.34mL of oxygen
63
What's a difference between an acid and a base?
Acids dissociate in solution; release H+. Bases do the opposite
64
What is a buffer?
Chemical and physiological mechanisms that prevent the change in hydrogen ion concentration
65
What is pH important for?
- Important for many biological/physiological functions
- pH is concentration of protons
- pH is logarithmic scale
66
How are CO2 and H+ similar?
- CO2 and H+ are both metabolites
- They are tightly related to each other
- They stimulate breathing
- They both indicate inadequate breathing and/or perfusion
67
What are 3 'buffering' mechanisms?
- Chemical (bicarbonate, phosphate, protein)
- Pulmonary ventilation
- Renal function
68
Whats the relationship between muscles and breathing?
Muscles make you breath more and breathing makes your muscles work harder
69
What is oxygen pressure?
- How it behaves (if in air, how much and therefore how much force it exerts
- So, where it goes, and how quickly (eg. 100mm Hg)
70
What is oxygen concentration?
- How much, in given volume of what it's in
- eg. 200mL/L blood
- Fitness doesn't change your concentration
71
What is oxygen saturation?
- How much, relative to what there could be (=100%)
- eg. 75%
72
Whats the relationship between oxygen pressure, concentration and saturation?
- They are not the same thing but they are related to each other
- Air pressure determines the saturation which determines the concentration
73
What are the functions of the CVS?
- Primarily transport
- Haemostasis
- Has two systems in series: Pulmonary and systemic
- Parallel flow within each system, due to successive branching of vessels
74
What is the relationship of cardiac adjustments to exercise?
VO2 = cardiac output x (CaO2-CvO2) = SV x HR x a-VO2 difference
75
What is a-VO2 difference?
The difference between what went into the tissues and what came out. AKA oxygen extraction (fit people can extract most)
76
What does aerobic power and fitness depend on?
Ability to:
- Increase cardiac output (SV and HR)
- Carry arterial oxygen
- Redistribute blood flow to active muscles
- Extract oxygen from blood in those muscles
77
What are the electrical properties of the Heart and Cardiac cycle?
- Autorhythmicity
- Long Action potentials (separate contractions)
- Electrical conduction system (need to modify the rate the membrane potential reaches threshold)
78
What is the myocardial structure of the heart and cardiac cycle?
- Intercalated discs
- Functional syncytium
- Uniform fibre type (all contract as one unit)
79
What is the metabolic profile of the heart and cardiac cycle?
- Increase mitochondrial 'density' to make a lot of ATP fast
- Use mainly fatty acids at rest
- Lactate under hard exercise
80
What are the phases of the cardiac cycle?
- Systole (contraction): about 1/3
- Diastole (relaxation): about 2/3
- Isovolumetric phases: same volume but still in the phase
81
What are the sex and fitness differences in cardiac output during submaximal exercise?
- 5-10% lower in trained people because they don't need to use as much oxygen (more efficient)
- 5-10% higher in females because less oxygen per unit of blood due to 10-15% less Hb
82
What are the sex and fitness differences in cardiac output during submaximal exercise?
- Can increase 4-5 times in untrained, vs 6-8 times in trained
- Max cardiac output ~20% higher in males (because their heart size is bigger on average)
83
How does SV respond with exercise time?
- Rapid, large increase to plateau due to increased venous return and increase SNS on ventricles
- More of a rise in SV for athletes as they start exercise
- Less rise if arm exercise due to higher BP
- Decreases later with dehydration and heat stress due to less blood centrally coming back to fill the heart to be pumped
84
How does SV respond to exercise intensity?
- Untrained, as it gets tough, you can't keep increasing the blood you pump
- Bit if you are fit, you can increase the blood you pump until you reach your VO2mx
- Need long term training for major effect
85
Why do athletes have lower HR at rest?
Because they can pump more blood per beat
86
How does HR respond with exercise time?
- Rapid, large increase to plateau due to decreased PNS and increase SNS activity on SA node
- Much less rise in athletes due to higher SV
- More rise if arm exercise due to more SNS activity
- Increase later with dehydration and with heat stress due to decreased central blood volume
87
How does HR respond to exercise intensity?
- Rises linearly until 100% VO2mx
- Athletes have lower HR at rest and also less HR rise as a function of absolute work rate
- They reach similar HRmax, but at a much higher work rate
88
Does oxygen extraction increase with exercise intensity?
Yes, greatly
89
Why do you extract more oxygen in exercise?
- Due to redistributing blood (constrict elsewhere and dilating and recruiting locally)
- Increased metabolic activity of muscle (bohr effect and increased pressure gradient of oxygen to mitochondria)
90
What muscle needs more oxygen?
Active muscle needs more oxygen during exercise
91
What are the four ways that active muscle gets more oxygen?
- Local vessels dilate due to metabolites
- Cardiac output increases
- Blood flow redistributed to active muscle
- Increased oxygen extracted from each unit of blood
92
How is net flow to each tissue balanced?
- Is a balance of intrinsic/local and extrinsic/global control
- Extrinsic control mainly by sympathetic nervous system
- Arterioles in each tissue respond differently
93
Whats the equation for VO2?
VO2 = SV x HR x a-vO2 difference
94
What is the purpose of local or intrinsic control of arterial tone?
To make sure the local flow matches the local tissues demand
95
How does local control of arterial tone happen?
- Myogenic: constrict against pressure
- Temperature: Dilate with heat, constrict in cold
- Metabolic: Dilates with increased CO2, H+ and decreased PO2
- Humoral: Nitric oxide in response to hypoxia and shear stress
- The role of these factors depends on where it is
96
What is Ohms law?
Change in pressure = flow x resistance
97
Does radius effect flow?
A small change in radius causes a large change in flow
98
What is the main purpose of extrinsic control of arteriolar tone?
To ensure maintenance of MAP and ensures adequate perfusion of active tissues, especially during a stress response such as exercise
99
What are the mechanisms of extrinsic control of arteriolar tone?
- Neural: SNS; releasing NAd in most arterioles
- Endocrine: eg. SNS; releasing NAd & Ad from adrenal medulla. ADH and ANG-II cause constriction
100
What is blood pressure?
- The pressure exerted against the walls of blood vessels.
- Highest at the start of circulation (ventricles) and lowest at the end (atria)
- It's given by how much blood you can pump by the resistance
101
What is systolic BP?
- Estimates the work of the heart
- Strain against arterial walls
- Appropriate cardiovascular function
- Expect it to increase during exercise
102
What is Diastolic BP?
- The minimum
- Peripheral resistance
- Expect it to have no change or even decrease during exercise
103
What is Mean Arterial Pressure?
- Driving pressure for flow or wall strain
- 2/3 DBP + 1/3 SBP
- DBP + 1/3 Pulse Pressure
104
Why does SBP increase during aerobic/continuous exercise?
Because the heart is working harder and therefore pushing more blood out pre beat to accomodate that.
105
Why does DBP stay the same or decrease during aerobic/continuous exercise?
Because of the resistance - the more muscle you use, you are backing off the resistance so pressure falls quickly
106
Why does SBP increase during resistance exercise?
Because you are contracting the ventricles harder because they are sympathetically activated. So to get any blood out they have to keep generating high blood pressure to do so.
107
Why does DBP increase during resistance exercise?
Because any active muscle is being squashed so there is no recovery phase. Also strong whole-body vasoconstriction
108
What does the rise in blood pressure with resistance exercise depend on?
- Whether a valsalva membrane manoeuvre
- Muscle mass contracted
- Duration of contraction (and fatigue state)
- Relative force of contraction (%MVC)
109
Why is resistance exercise problematic for people with hypertension and CHD?
Increased SBP and HR so increase RPP (rate pressure product)
110
Why is BP higher in arm vs leg exercises?
- Because the arms are working harder as there is less muscle to do the same work
- Therefore you recruit more motor units to activate more sympathetic innervation
- Oxygen extraction is lower because there is less musculature
- You also end up using more glucose in arm exercises
111
112
What happens to BP in recovery?
- BP usually decreases after exercise below pre-exercise values for both normotensive and hypertensive people
- This is called post exercise hypotension
- Possibly due in part to blood pooling in visceral organs or legs and reduced baroreflex control
113
114
How do we control the cardiovascular system during exercise?
- There is a hierarchy of ventilatory control
- Feedforward control dominates early (immediate jump in HR)
- Ergoreceptors maintain a plateau
- Baroreceptors reset to a higher level at exercise onset
