changes to the gymnast's cardiac output and stroke volume. 1. (b) (i) What B. Stroke volume increases/equiv. Load Briefly explain the terms 'ability' and 'skill'. (2 marks) What is the relationship between these three time phases? (1 mark). Learn vocabulary, terms, and more with flashcards, games, and other study tools. Describe the relationship between heart rate, cardiac output and stroke Analyse cardiac output, stroke volume and heart rate data for different. The amount of blood your heart pumps is constantly changing to meet the Cardiac output (CO) is the term used to show the amount of blood your heart pumps the contents of more than 2 and a half of these soda bottles every minute. per minute and stroke volume (SV) to describe the volume of blood.
This allows blood to flow from the arteries more easily, thereby preventing the arterial pressure from increasing as blood is injected into it by the ventricle. Frank-Starling Mechanism However, the factor we will be most concerned with is the Frank-Starling mechanism. Unfortunately, it is also the one most difficult to get your mind around. The Frank-Starling mechanism leads to changes in the stroke volume as a result of changes in the end-diastolic volume.
The end-diastolic volume is the volume of a ventricle at the very end of filling and just before systole begins. This can change because the ventricles are flexible and under different circumstances, the amount of blood flowing in during diastole varies.
If less blood flows into the ventricle as it fills, the end-diastolic volume goes down. If more blood flows in, the end-diastolic volume goes up. The Frank-Starling effect is due to the fact that heart muscle fibers respond to stretch by contracting more forcefully.
This is not a passive, elastic effect, but rather due to an increased expenditure of ATP energy.
We are not going to try to explain the cellular basis of this effect. It is not as straightforward as you might think. Thus, if the end-diastolic volume increases, the muscle fibers are lengthened and the ventricle contracts more forcefully, ejecting a greater stroke volume. The figure to the right shows this Frank-Starling effect. What factor alters the filling during diastole?
For the right ventricle, this is the pressure in the right atrium, because this is the pressure that is experienced by the right ventricle as it fills.
Since there is no valve at the entrance to the right atrium, the pressure in the right atrium is necessarily the same as the pressure in the veins at the entrance to the right atrium. This pressure in the large veins at the entrance to the right atrium is called the central venous pressure.
In other words, the central venous pressure is the same at the right atrial pressure, and this is the pressure that determines the filling of the right ventricle and thus its end-diastolic volume.
Stroke Volume and Cardiac Output
The central venous pressure always is only a few mm Hg, but nonetheless it does change enough to significantly affect the stroke volume. In particular, posture changes this pressure and that is the factor with which we are here most concerned. The Effect of Posture on Stroke Volume Recall how voluminous and thin-walled the superior and inferior vena cava are. You probably were able to put two fingers into the superior vena cava of the pig heart.
When a person is lying down, the large veins in the chest are plump with blood.
Stroke volume - Wikipedia
And because these veins are stretched, the pressure in them is higher than when they contain less blood. Consequently, when lying down, the central venous pressure is relatively high, the end-diastolic volume is relatively high and thus the stroke volume is comparatively high. But this changes when we stand. The pressure in the large veins in the legs increases greatly.
For example, one meter below the heart, the effect of gravity adds about 74 mm Hg of pressure. This causes the distensible, voluminous veins to expand, and blood pools in the leg veins.
This reduces the blood in the central veins, and the central venous pressure drops. Because these central veins are very compliant structures, pressure cannot increase again in them until blood flows back into the thorax.
The Effect of Muscle Contraction on Stroke Volume Lying down, of course, is one factor that would increase the amount of blood in the veins in the thorax and thus the central venous pressure. However, another important factor is muscle contraction. If the standing person begins walking, the contractions of the leg muscles squeeze on the leg veins, thereby forcing blood from those veins up into the thorax.
This is called muscle pumping. Thus, as a standing person begins walking, the end-diastolic volume and thus the stroke volume increase. Muscle pumping works on the veins, but not the arteries, because veins are large, highly compliant and the larger ones have valves.
- Relationship Between Heart Rate & Stroke Volume
- Regulation of Cardiac Output
Heart rate is measured by using a stethoscope or by feeling your pulse. Heart rates are classified by exertion levels ranging from resting to maximum rates. Typical resting heart rates vary between 40 beats to 80 beats per minute at rest.
The average resting rate is 70 beats per minute, with elite athletes measuring close to Maximum heart rate measurements are based on your age, subtracting your age from the number Stroke Volume Stroke volume is defined as the amount of blood pumped in one beat. Generally, stoke volume is an estimated measurement.
Actual measurements are performed on heart patients by measuring arterial pressure. Estimated average stroke volume amounts range between 50 to 70ml at rest to to ml during cardio training. Elite athletes have estimated stroke volumes between 90 to ml at rest to to ml during cardio training. Cardiac Output Cardiac output is defined as the total amount of blood circulated throughout your body in one minute.
Cardiac output is measured by multiplying heart rate by stroke volume.