1. Cardiovascular System

Question 1

Impact of physical activity on people’s health

Answer 1

• regular physical activity keeps the heart healthy so it has a positive impact on heart disease
• it lowers bad ‘LDL’ cholesterol levels and significantly increases good ‘HDL’ cholesterol levels

Question 2

Stroke volume (starlings law, ejection fraction)

Answer 2

• the volume of blood pumped out by the heart ventricles in each contraction
• resting stroke volume is bigger for elite performers
• SV increases by 40-60% of maximum effort when the intensity increases. Once a performer reaches this point, SV plateaus because the ventricles do not have as much time to fill up with blood due to an increased HR

Starlings law:
•increased venous return > greater diastolic filling of the heart > cardiac muscles stretched > more force of contraction > increased ejection fraction

-starlings law explains how stroke volume increases during exercise. This occurs when there is an increase in venous return, which leads to greater diastolic filling, so the cardiac muscle is stretched. Consequently, a more powerful force of contraction takes place, which increases the ejection fraction and therefore increases the stroke volume.

Ejection fraction- refers to the percentage of blood pumped out the left ventricle per beat.

Question 3

Heart rate (elite performers, bradycardia, hypertrophy)

Answer 3

• the number of times a heart beats per minute.
• as the intensity of the exercise increases, so does the HR. Maximum heart rate= 220-age
• a trained performer had a greater HR range because their resting HR is lower and maximum HR increases. Regular exercise causes hypertrophy of the heart, resulting in an increase in stroke volume and maximum cardiac output, leading to bradycardia (a lower HR of below 60 bpm)

Question 4

Heart rate responses to maximal and sub maximal exercise

Answer 4

A. Anticipatory rise due to hormonal action of adrenaline which causes the SAN to increase HR

B. Sharp rise in HR due mainly to anaerobic work

C. Heart rate continues to rise due to maximal workloads stressing the anaerobic systems

D. Steady state as the athlete is able to meet the oxygen demand with oxygen supply

E. Rapid decline in HR as the exercise stops

F. Slower recovery as the body systems return to resting levels; HR needs to remain elevated to rid the body of waste products, for example lactic acid

Question 5

Cardiac output

Answer 5

Cardiac output, Q, is the amount of blood bubbles out by each ventricle per minute, where: Q=SV x HR

-cardiac output stays the same at rest for both a trained and u trained performer. During exercise, maximum cardiac output increases due to an increase in HR and in SV. Cardiac output will increase as the intensity of exercise increases until maximum intensity is reached and then it plateaus. During exercise the increase in maximum cardiac output will have huge benefits for the trained performer because the hey will be able to transfer more blood, and therefore more oxygen, to the working muscles.

Question 6

Cardiac conduction system

Answer 6

• heart muscle is described as being myogenic because the beat originated in the heart muscle itself with an electrical signal in the SAN. from the SAN of he electrical impulse spreads through the walls of the atria causing them to contract (atrial systole). The impulse then passes through the AVN, where it is delayed for approximately 0.1 seconds to enable the atria to fully contract. The impulse then travels through the bundle of HIS own high divides into two branches into the purkinje fibres, which spread the impulse throughout the ventricles, causing them to contract.
• SAN is a small mass of cardiac muscles fund in the wall of the right atrium that generates the heart beat. It is more commonly called the pacemaker

Question 7

Factors affecting the change in the rate of the conduction system (neaural control and hormonal control)

Answer 7

-the conduction system makes sure that the HR increases during exercise to allow the working muscles to receive more oxygen. The rate at which impulses are fired from the SAN can be controlled by both neural and hormonal mechanisms.

Question 8

Neural control mechanism

Answer 8

• involves the sympathetic nervous system, which stimulates the heat to beat faster, and the parasympathetic nervous system, which returns the heart to its resting level. These two systems are co-ordinated by the cardiac control centre located in the level. These two systems are located in the medulla oblongata of the brain
• medulla oblongata= most important part of the brain because it regulates mechanisms that keep us alive

•the sympathetic nervous system speeds up the HR and the parasympathetic system slows it down

-the cardiac control centre is stimulated by chemoreceptors, baroreceptors and proprioreceptors, and then sends an impulse through either the sympathetic system to the SAN to increase the HR or the parasympathetic system to the SAN to decrease HR

> CHEMORECEPTORS- detect increase in blood carbon dioxide -> cardiac control centre -> sympathetic system -> SAN increases in HR

> BARORECEPTORS- detect an increase in BP -> cardiac control centre -> parasympathetic system -> SAN decreases in HR

> PROPRIORECEPTORS- detect an increase in muscle movement -> cardiac control centre -> sympathetic system -> SAN increases HR