Effects of exercise on CVR

Question 1

what happens during exercise?

Answer 1

• HR increases
  -resp rate increases
  -skeletal muscle blood flow increases
  -tidal volume increases

Question 2

at rest, what is the heart rate most affected by?

Answer 2

parasympathetic (vagal) nervous innervation

Question 3

during moderate exercise what is the heart most affected by?

Answer 3

increased sympathetic nervous innervation

Question 4

The relationship in time between the ECG and the haemodynamic movements of the heart

Answer 4

• Atrial contraction follows P-wave
• Ventricular contraction follows QRS complex

Question 5

what does an arm sphygmomanometer cuff measure?

Answer 5

peak systolic and diastolic pressure

Question 6

what dictates the pressure in arterioles and capillary beds?

Answer 6

mean blood pressure Marked increases in mean blood pressure will increase the probability of spontaneous haemorrhage in the vessels with thinner walls (e.g. capillaries)

Question 7

what is dynamic exercise?

Answer 7

• Running in such a way, where you are still operating aerobically. Using the majority of muscles in your body over many minutes.

The two devices used in the lab are the bicycle ergometer and the treadmill

Question 8

What does the increase in cardiac output during exercise do for mean blood pressure?

Answer 8

During exercise, blood is diverted away from less critical organs like the gut, kidney etc in order to ensure that critical organs have blood flow.

The increased blood flow to lungs and muscles outweighs the decrease to other organs, so TPR is lower overall.

Question 9

What are the effects of static exercise compared to dynamic exercise?

Answer 9

Fall in diastolic pressure is due to the net vasodilation of the arterial tree in the body due to vasodilation in skeletal muscle beds.

As individuals get older, and the elasticity of their blood vessels decreases, the increases in blood pressure of static exercise comes with a risk of haemorrhage or stroke.

Chronic contraction of muscles increases the pressure inside the muscle, and that pressure is enough to squeeze and occlude the arteries running through the muscle. This reduces the lumen size of that vessel. So even though arterioles in the muscle are dilated due to local factors, blood can’t get to them because the artery has been occluded proximally.

Question 10

describe the bruce protocol?

Answer 10

• A cardiovascular stress test. A test which was developed to standardise the exercise regime to ensure that across the profession there was a standard protocol followed which would allow us to make inter-patient comparisons.
• The idea that every 3 minutes, the speed/gradient/resistance of a treadmill or bike was increased and that patients had to increase the work they do over time.
• During that time, the patient’s ECG and blood pressure was monitored

Question 11

chat are the clinical signs from a stress test?

Answer 11

A stress test can reveal areas of poorly perfused myocardium - due to narrowing/occlusion of coronary.Making the heart work harder (increased heart rate) increases oxygen consumption and this cannot be matched by greater delivery of oxygenated blood. Subsequent hypoxia causes electrophysiological changes that are evident as ST segment elevation/depression changes. These reverse after exercise. The subject is also exercise intolerant, i.e. cannot progress through the Bruce protocol significantly.

Question 12

which segment of the ECG is most changed during exercise?

Answer 12

TP length (it shortens, becomes pretty non existent but comes. back with recovery)

Question 13

how does diastolic BP change static exercise, as compared to dynamic exercise?

Answer 13

For equivalent heart rates, diastolic pressure would increase more during static than dynamic exercise.

Question 14

how does the mean blood pressure change in static exercise, as compared to dynamic exercise?

Answer 14

Mean blood pressure is significantly higher during static when to comparative heart rates during dynamic exercise due to the higher diastolic pressure during static exercise

Question 15

how does heart rate change during static exercise as compared to dynamic exercise?

Answer 15

Dynamic exercise at the higher levels of effort can reach very high rates. The maximum heart rate can be estimated at 220-age. During strenuous dynamic exercise, very high heart rates that is maintained for many minutes. Heart rate in static exercise does not reach as high values.

Question 16

how does the ECG trace recorded in static exercise differ from that recorded during dynamic exercise?

Answer 16

In the case of equivalent heart rates, the ECG does not differ significantly. The main phase that is altered during exercise is the time between the T wave of one PQRST complex and the P wave of the next complex.

Question 17

To which phase of the cardiac cycle does the QT interval correspond?

Answer 17

QT interval corresponds to the time between ventricular depolarisation and the ventricular repolarisation corresponding approximately to the duration of the ventricular action potential, i.e. about 250ms at resting heart rates. The QT interval is coincident with the cardiac systole as the cardiac action potential triggers ventricular contraction that lasts approximately the same time.

Question 18

To which phase of the cardiac cycle does the TP interval correspond?

Answer 18

The TP interval corresponds to the diastolic interval, i.e. the time during which the ventricles fills between ejection (systolic) phases.

Question 19

Which phase of the ECG changes more during exercise: the QT interval or the TP interval?

Answer 19

The TP interval is the phase of the ECG that shows the most dramatic decrease during exercise. The QT interval may shorten but by proportionately a significantly lesser degree.