Cardiovascular and respiratory responses to exercise Flashcards
(72 cards)
1
Q
types of exercise
A
- dynamic or isometric
- aerobic or anearobic
- large muscle mass or small muscle mass
2
Q
what could everyday tasks be classified as for patients with cardiorespiratory diseases
A
high-intensity or maximal exercises
3
Q
VO2
A
oxygen consumed
4
Q
VCO2
A
carbon dioxide produced
5
Q
how is VO2 and VCO2 determined in exercise
A
amount of muscle activity
blood flow & ventilation are coupled to metaboliism
6
Q
what determines method of ATP maintenance?
A
- metabolic status
- energy requirements
7
Q
what happens to VO2 during exercise
A
increases
8
Q
who will have greatest VO2max
A
highly trained atheletes
- endurance
9
Q
tidal volume during exercise
A
- increases as minute ventilation increases
- increases linearly up to 6 times resting value
- will level off at ~50% vital capacity
10
Q
what maintains gaseous exchange at all times
A
residual lung volume
11
Q
why is there always residual lung volume
A
to allow for gas exchange
12
Q
what is residual lung volume
A
air in the lungs
13
Q
how are elevated pulmonary ventilations achieved
A
- linearly increases in tidal volume
- non-linear increases in breathing rate
14
Q
when does ventilation response to exercise
A
synchronous with exercise onset
- not a reflex response to altered chemistry
- not feedback mechanism
15
Q
humoral changes during exercise
A
- adrenaline released from adrenal medulla
- induces vasoconstriction at viscera
- vasodilation at skeletal muscle
- increases heart rate
- bronchodilator
- glycogenolysis in liver
16
Q
what happens to K during exercise
A
K from depolarised muscle cells can increase to levels considered dangerous if muscles were at rest
17
Q
PaCO2 and PaO2 during exercise
A
change very little if at all.
- PaO2 may rise a little due to decreased PaCO2 or fall due to limitation in diffusion
- PaCO2 will fall a little at high VO2 as pH increases
18
Q
One of the most important observations in ventilatory response to exercise
A
expected rise in PACO2 does not occur with rise in metabolism during exercise
19
Q
PACO2
A
partial pressure of alveolar gas
Alveolar are close to arterial blood sample so good measure
20
Q
PACO2
PaCO2
A
PACO2 partial pressure alveolar gas
PaCO2 partial pressure arterial gas
21
Q
4 hypotheses for regulation of respiratory responses to exercise
A
- central command or feedforward must account for at least fast component of response
- afferent signals from muscles passing up spinal chord my produce feedback control - dog experiments support this but paraplegics don’t
- signals from peripheral chemoreceptors detecting pH changes play some role. Even though PACO2 remains constant, slight oscillations may be detected, or changes in sensitivity. But their removal only mildly alters phase 2
- lactate, potassium and adrenaline all stimulate peripheral chemoreceptors and may play a role
22
Q
respiratory responses work in
A
parallel
- if one signal is removed, the others will work to compensate and keep respiration rate constant
23
Q
change in blood flow during exercise
A
changes from spending 0.8 seconds in pulmonary capillary at rest to only 0.2 seconds during exercise
- less time to load oxygen
- large reserve usually sufficient to complete oxygenation
24
Q
changes in cardiac output
cardiocentric
A
from 5l/min at rest up to 30l/min in intense exercise
25
cardiac output =
cardiocentric
heart rate x stroke volume
26
changes in heart rate during exercise
HR often rises with one beat during transition from rest to work = before feedback could do so
- provides evidence for central command or feedforward
- increases rapidly in first 10-20 secs then slowly increase
27
what provides evidence for feedforward or central command of response to exercise
HR increases within one beat of onset, which is too quick for feedback mechanism
28
frank-starling's mechanism showing cardiac output matched to demand
- heart automatically pumps all venous return back to arteries
- dog's exercise performance was not impaired by cardiac denervation
29
cardiac output =
tissuecentric
(arterial BP - central venous BP)/ total peripheral resistance
- arterial BP ~90mmHg
- central venous BP ~3mmHg
TPR can be changed to alter CO without changing BP
30
changes in cardiac output
tissuecentric
total peripheral resistance is altered to change flow/CO without changing BP
31
precapillary sphincters
- functional unit of the capillary bed with precapillary branching off directly from the arteriole
- important for directing blood to tissue that need it most and reducing blood flow to inactive tissues
- needed 'cus limited blood
32
muscle vasodilation during exercise
- resting muscle has a low blood flow and only a few capillaries open at a time
- exercise causes more capillaries to open, higher blood velocity & double the fall in oxygen saturation
- muscle oxygen consumption can increase more than 40 times
- capillary recruitment also reduces diffusion distance
33
blood flow in resting muscle
- resting muscle has a low blood flow and only a few capillaries open at a time
34
what changes blood flow in muscle during exerise
vasodilation
35
changes to muscle capillairies in exercise
- capillary recruitment
- more capillaries open
- higher blood velocity
- double fall in oxygen saturation
= muscle oxygen consumption increase more than 40 times
36
muscle oxygen consumption during exercise
can increase more than 40 times
37
blood flow redistribution during exercise
CO increases with exercise intensity and blood flow is redistributed
- skeletal muscle large proportion
- skin blood flow increases for thermoregulation
38
changes in blood flow to skin during exercise
rest: 9% 500ml
light exercise 16% 1500ml
heavy exercise: 12% 1900ml
39
changes in blood flow to skeletal muscle during exercise
rest: 21% 1200ml
light exercise 47% 4500ml
heavy exercise: 71% 12500ml
40
what exercise types changes BP most
heavy resistance magnifies change in BP more compared to dynamic aerobic
41
changes in BP and HR in isometric exercise
- hand grip at 30% maximal voluntary contraction
- modest HR increase
- large BP increase
42
changes in BP and HR in dynamic exercise
- large HR increase to maximal values
| - little change in BP
43
CV control during exercise
controlled by autonomic nerve supply :
- parasympathetic
- sympathetic
- adrenaline
44
autonomic nerve supply to the heart =
- parasympathetic
- sympathetic
- adrenaline
45
parasympathetic control of heart during exercise
via vagus nerves, which act via muscarinic acetylcholine receptors
- mainly produce bradycardia
helps to slow the increased HR
46
sympathetic control of heart during exercise
- via the superior, middle and inferior nerves via beta 1 adrenoreceptors
- produce tachycardia and increased contractility
- releases neurotransmitter noradrenaline
47
control of circulating adrenaline on heart during exercise
- circulating adrenaline from medulla
- also act of beta 1 adrenoreceptors
- tachycardia and increase contractility
48
what do afferent signals do to heart during exercise
strong evidence they play a part in feedback control of HR and BP
K+ and H+ are probably sense in the muscle
49
what does evidence suggests may also play a role in controlling BP and HR
afferent signals from muscle involved in feedback control, most likely from sensing K+ and H+ in muscle
50
tachycardia
abnormally rapid heart rate
51
bradycardia
abnormally slow heart rate
52
summary of CV responses to exercise
- peripheral circulation determines venous return by controlling the perfusion of each tissue
- the heart matches cardiac output to venous return
- blood pressure response depends on the kind, duration and intensity of exercise
- there is evidence for central command, feedforward & humeral mechanisms that are all integrated to regulate responses
53
variations of VMAX
- generally lower in women than men
- tends to increase up to the of 20
- slowly declines after 20 yrs
- maintaining active lifestyle can delay decrease
- results vary by testing method
- often greater in load bearing exercises
54
what can VMAX indicate
long-term energy system capacity
55
method of VMAX measurement
increments exercise test to exhaustion
e.g on a treadmill
method of testing should be tailored to indivual requirement. e.g running for a runner, cycling for a cyclist
56
what is H+ from exercise buffered by
bicarbonate
57
glycolysis during exercise causes increases in
lactate and H+
58
how is H+ buffered
H+ + HCO3 -> H2CO3 -> CO2 + H2O
- needs presence of carbonic anhydrase
59
when does minute ventilation increase disproportionately to VO2
ventilatory threshold
When lactate and H+ begin to increase and buffered by bicarbonate and CA
60
what does the ventilatory threshold predict
lactate threshold, from the ventilatory response during incremental exercise
61
what happens to majority of lactate at lower outputs
pyruvate dehydrogenase and shuttle system enzymes metabolise the majority
62
what happens lactate at higher power outputs
- ATP demands exceed aerobic provisions
- glycolytic flux must increase
- therefore lactate production is increased
- lactate is increased at greater rate than it can be metabolised
- lactate accumulates in venous blood
= lactate threshold
63
what is considered a high power output
>60% VO2max
64
lactate threshold
when lactate is produced at a greater rate than shuttle system enzymes and pyruvate dehydrogenase can metabolise it. Occurs at high power exercise, when glycolysis used for energy bc ATP provisions are insufficent
65
what limits exercise
- CV performance is the usual limit not CR
- ventilatory flows are usually lower than highest attainable value
- partial pressure of oxygen; even though muscle mitochondria can work at as low as 0.15kpa, there must be a diffusion gradient from blood to cell
- VMAX corresponds with HR
66
example VT
3.04L/min
67
example LT
43.5 ml/kg/min
68
Effects of training on CR response
- increase total lung capacity to more than 8l e.g endurance divers, wind musicians
- increase VO2max to more than 85ml/kg/min
- decrease resting HR to less than 40bpm
- increase stroke volume from bigger heart, trained muscle!!
69
how does diffusing capacity for oxygen at rest change with training
doesnt
70
max stroke volume changes with training
| ml
normal: 104
training: 120
olympians: 167
71
max CO changes with training
| ml
normal: 30
training: 23
olympian: 30
72
VMAX changes with training
| l/min
normal: 3
training: 4.2
olympian 5.4
