38 - Exercise Physiology

Question 1

What is the difference between dynamic and stable exercise?

Answer 1

Dynamic - rhythmical movement and contraction and relaxation of muscle
Static - maintained for a long length of time e.g lifting

Question 2

What is the immediate source of energy for muscle function

Answer 2

Creatine phosphate
catalysed by creatine kinase
(uses no oxygen)

Question 3

What is the non-oxidative source of energy for muscle

Answer 3

Glycotic pathway
Excess pyruvate converted to lactic acid
Lactic acid build up
= Ph drop

Question 4

What is the oxidative source of energy for muscle

Answer 4

Requires oxygen

- oxygen phosphorylation

Question 5

What is VO2 at rest

Answer 5

(Volume of oxygen consumed at rest)

250ml/min (70kg person )

Question 6

How much oxygen is consumed/minute for each kg of body mass

Answer 6

3.6ml O2

Question 7

VO2 max

Answer 7

maximum oxygen consumption is reached at steady exercise

Reflects the aerobic physical fitness of the individual

Question 8

Fick equation

Answer 8

VO2 = Q x (CaO2-CvO2)

Question 9

What does Q, CaO2, CvO2 stand for

Answer 9

Q - cardiac output
CaO2 - arterial oxygen content
CvO2 - venous oxygen content

Question 10

What is the anaerobic threshold

Answer 10

The point where lactate begins to accumulate in the bloodstream
Lactic acid is being produced faster than it can be metabolised - determines fitness and varies individuals

Question 11

What does exercise do to increase HR

Answer 11

reduced activity of parasympathetic and increased sympathetic nerves

Question 12

What does exercise do to increase stroke volume

Answer 12

Increases venous return
Increased EDV - increased SV via starling’s law
Sympathetic activity has positive inotropic response on the heart

Question 13

How does the heart adapt to sustained increases in blood pressure

Answer 13

Increases muscle mass - hypertrophy ( increase in myocyte size)
Can be physiological (reversible) or pathological (irreversible)

Question 14

Compare an athletes heart and a failing heart

Answer 14

Athletes heart - increased muscle mass, normal cardiac function, reversible
Failing heart - increased muscle mass, reduced cardiac function, irreversible, cell death and fibrosis

Question 15

What is the difference between blood flow to skeletal muscle at rest and during exercise

Answer 15

At rest – 20-25%

During exercise – 80-90%

Question 16

What is the the role of alpha adrenoreceptors in the redistribution of blood flow during exercise

Answer 16

constrict the vessels in the gut and cause vasoconstriction of veins.

Question 17

What is the the role of beta 1 adrenoreceptors in the redistribution of blood flow during exercise

Answer 17

(found in the heart) act to increase the rate and force of myocardial contraction

Question 18

What is the the role of beta 2 in the redistribution of blood flow during exercise

Answer 18

act to relax the muscle and increase ventilation and oxygen uptake and cause vasodilation of blood vessels, especially those supplying skeletal muscle

Question 19

What is the local control of blood flow during exercise

Answer 19

Tissue factors - adenosine and inorganic phosphates, carbon dioxide, hydrogen ions (H+) and potassium ions (K+) released from contracting muscles.
Endothelial mechanisms – NO

Question 20

What happens to skin blood in moderate exercise

Answer 20

Skin blood flow increases (part of the thermoregulation response)

Question 21

What happens to skin blood in intense exercise?

Answer 21

vasoconstriction takes over and blood redirected to skeletal muscles at the expense of the cooling action (i.e. temperature will rise).

Question 22

What are the blood pressure changes during exercise?

Answer 22

MABP only rises slightly
Decreases in TPR are offset by increases in CO
Increased force of ventricular contraction (increased SV) causes an increase in systolic pressure.
In dynamic exercise the diastolic pressure stable or even decreases.

Question 23

How are the body’s need for oxygen met during exercise

Answer 23

Increased pulmonary minute ventilation

Oxygen extraction in tissues

Question 24

What is rest pulmonary ventilation and what can it increase to during exercise?

Answer 24

Rest pulmonary ventilation - 8 l/min
Heavy exercise - increase to 100 l/min or more.

At the start of exercise, PV increases and rises till it reaches a steady state appropriate to the work being done

• At moderate work rates the steady state ventilation is directly proportional to the work done as measured by the oxygen consumption
• However during severe exercise the increase in ventilation is disproportionately large in relation to oxygen uptake (limiting factor).

Question 25

How is an increase in ventilation achieved

Answer 25

Rise in respiratory rate and tidal volume

Question 26

What is the pathway of oxygen from atmosphere to mitochondria during exercise ?

Answer 26

Uptake of O2 in lungs (pulmonary ventilation)
Delivery of O2 to muscle (blood flow and O2 content)
Extraction of O2 from blood (delivery and PO2 gradient between blood/cell/mitochondria)

Question 27

What happens to the arteriovenous difference in o2 content?

Answer 27

Rises so increases in gradient driving oxygen diffusion

Question 28

What happens to the PaO2 in the arterioles and venous blood?

Answer 28

Arterial blood - decreases slightly

Venous blood - decreases but paCO2 increases

Question 29

What happens to the Hb-O2 binding affinity during exercise?

Answer 29

Decreases so oxygen delivery is increased

- increased CO2, increased H+, increased local/tissue temperature

Question 30

What is excess post-exercise oxygen consumption?

Answer 30

Increase in rate of oxygen intake following strenuous exercise - necessary to eliminate oxygen debt

Question 31

What does a denervated carotid body do?

Answer 31

Slower ventilatory response than a normal subject