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CR2-L38-Exercise physiology

Terms in this set (43)

What are the two types of exercise?
dynamic and static
what is dynamic exercise
rhythmical movement of joints and contraction and relaxation of muscles. E.g. Swimming, running
what is static exercise
maintained contraction for a length of time. E.g. lifting
What are the three sources of energy that support skeletal muscle function?
- Immediate
- Non-oxidative (anaerobic)
- Oxidative (aerobic)
Where does the immediate source obtain it's ATP from?
Creatine catalysed by creatine kinase into phosphocreatine
what is phosphocreatine also known as
creatine phosphate - provides a store of high-potential phosphate
what is VO2
volume of oxygen consumed
What is the normal VO2 at rest in a 70kg person?
How is it calculated?
250ml/min
3.6 ml O2/(min x kg
When is VO2 max reached?
When oxygen consumption remains at a steady state despite an increase in workload
What is VO2 max?
highest peak oxygen uptake that an individual can obtain during dynamic exercise using large muscle groups during a few minutes performed under normal conditions at sea level
What would VO2 max be in COPD and elite endurance athletes?
10-20ml 02/(minxkg)
80-90ml 02/(minxkg)
What is the anaerobic threshold (lactate threshold)?
Point where lactate begins to accumulate in the bloodstream
How does the CVS respond during exercise?
Rise in cardiac output (SV and HR)

Redistribution of cardiac output to the active muscles
Describe how HR and stroke volume is increased during exercise?
sympathetic increases HR and mobilisation of blood from great veins (vasoconstrict)
Explain the increase in stroke volume during exercise?
Increased venous return
Increased EDV (preload)
Increased SV
Sympathetic has a positive inotropic response to the heart
Difference in SV and HR changes during exercise
SV reaches max levels at moderate exercise intensity. So further increases in CO are achieved through HR changes
How does the heart adapt in the long term to increased BP? What causes this? (2 ways)
Increase muscle mass;
Physiologically - Pregnancy/exercise
Pathologically - Disease such as hypertension
Why do athletes get bradycardia?
Volume induced cardiac hypertrophy in athletes increases resting end diastolic volume and SV.
At rest how much of cardiac output is directed towards muscle?
20-25%
1l/MIN
During exercise how much of CO is directed towards muscle?
90%
22L/min
name the three adrenergic receptors that play an important role directing blood flow from non-essential organs to skeletal muscle
alpha adrenoreceptors
- beta 1 adrenoreceptos
- beta 2 adrenoreceptors
role of alpha adrenoreceptors during exercise
constrict the vessels in the gut and cause vasoconstriction of veins
role of beta 1 adrenoreceptors during exercise
act to increase the rate and force of myocardial contraction
role of beta 2 adrenoreceptors during exercise
act to relax the muscle and increase ventilation and oxygen uptake and cause vasodilation of blood vessels supplying skeletal muscles
Describe the local factors effect on redistribution of blood?
Nitric oxide acts to relax smooth muscle cells and this causes dilation of blood vessels
Give some examples of tissue factors released during exercise?
Adenosine and inorganic phosphates, carbon dioxide, H+ ions
Describe distribution of blood flow to the skin during moderate exercise?
blood flow increases - thermoregulation
distribution of blood to the skin during intense exercise?
vasoconstriction takes over and blood redirected to skeletal muscles at the expense of the cooling action
Summary of redistribution...
What happens to total peripheral resistance during exercise?
Reduces to a third of at rest level
equation for MAP
MAP = (CO x SVR) + CVP
Does MABP change during exercise? Explain why?
Reduces slightly, as TPR decrease is offset by increases in CO
What happens to systolic and diastolic pressure during exercise?
Systole increases - because of an increased force of ventricular contraction

Diastolic decreases from the TPR decrease
What is pulmonary ventilation during rest and exercise?
8l/min
100l/min
How is an increase in ventilation achieved?
Via a rise in respiratory rate and tidal volume
What happens to the partial pressure of oxygen in arterial blood at high levels of exercise?
Declines
As the 02 consumption rises the pp02 in mixed venous blood falls and the ppCO2 rises
What happens to oxygen affinity during exercise? What shifts the curve?
shift to right, due to higher CO2/acidity in blood. Therefore o2 is more easily unloaded at tissues
Why is there an 02 deficit at the beginning of exercise?
As 02 consumption doesn't rise quickly enough to match the energy requirements
What is excess post-exercise oxygen consumption (EPOC)?
Increase in the rate of 02 intake following strenuous activity, necessary to eliminate the oxygen debt
What is the O2 used for which is required for o2 debt?
resynthesising ATP and creatine phosphate (oxidative pathway)
resynthesising glucose and glycogen
What are the factors that regulate CVS response to exercise?
Signals from higher brain levels
How does the central command regulate CVS activity in exercise?
Modulates baroreceptor reflex sensitivity

Receives feedback from increased activity in afferent nerves from exercising limbs

metaboreceptors respond to changes in metabolite conc (mainly pH and K+)
Where are signals for increase in ventilation initiated?
Motor activity from pre-motor area of the cerebral cortex

CO2 major driver for ventilation - chemoreception - carotid body

Increase in neural input from joints

Increased plasma potassium concentrations provide stimulus to peripheral chemoreceptors
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