Cardiac function

Question 1

Use Starling’s law of the heart to explain how stroke volume increases during activity.

Answer 1

Greater diastolic filling / preload;
Cardiac muscle stretched / elastic;
Greater / stronger / more powerful / force of contraction;
Increased ejection fraction;

Question 2

What term is used to describe a resting heart rate that is below 60 beats per minute?

Answer 2

Bradycardia / athletes heart

Question 3

How does a lower resting heart rate affect oxygen delivery to muscles?

Answer 3

Less oxygen needed for contractions of heart; More oxygen available for muscle contractions;
Increased heart rate range.

Question 4

Explain how changes in the acidity of the blood cause the heart rate to increase during a game
of football.

Answer 4

Caused by more carbon dioxide being produced;
This is detected by chemoreceptors; Nerve messages are sent to the medulla (oblongata); Sympathetic nervous impulses are sent.
To the Sino-Atrio node / SAN/SA node.
Decrease in parasympathetic / vagus nerve impulses.

Question 5

Use ‘Starling’s law of the heart’ to explain how stroke volume increases when running.

Answer 5

Greater diastolic filling / heart fills with more blood;
Cardiac muscle stretched / elastic;
Greater / stronger / more powerful force of contraction / contractility;
Increased ejection fraction / greater percentage of blood ejected.

Question 6

Explain how the heart controls the rate at which it beats.

Answer 6

Sino–atrial node / SAN / pacemaker;
Causes systole / contraction (of atria);
Atrio–ventricular node / AVN;
Bundle of His / AV bundle;
Purkinje fibres;
To ventricle / ventricle contracts.

Question 7

Briefly explain the terms ‘cardiac output’ and ‘stroke volume’, and the relationship between
them.

Answer 7

Cardiac output – ‘the volume / amount of blood pumped from heart / ventricle
in one minute; Stroke volume – ‘the volume / amount of blood pumped from the heart / ventricle
in one beat; Cardiac output = stroke volume × heart rate / Q = SV × HR.

Question 8

Explain how it is possible for a trained performer and an untrained performer to have the
same cardiac output for a given workload.

Answer 8

Different sized hearts / hypertrophy – trained bigger.
Accept converse, but must be explained.
Different stroke volumes – trained bigger.
Accept converse, but must be explained.
Different heart rates – untrained higher.
Accept converse, but must be explained.
Can only occur at sub maximal workloads;
At higher workloads untrained will not be able to increase their heart
rate sufficiently;
Different physiques / size / mass – untrained bigger.

Question 9

What are the effects of training on resting ‘cardiac output’ and ‘stroke volume’?

Answer 9

Cardiac output stays the same / no effect / no change;

Stroke volume increases / equiv.

Question 10

Explain how rising levels of carbon dioxide cause an increase in cardiac output.

Answer 10

Increases acidity / hydrogen ion concentration / lowers pH / (in blood);
Detected by chemoreceptors;
Impulses / information to cardiac centre / medulla (oblongata);
Increased stimulation of sympathetic nerve / decreased stimulation of
parasympathetic / vagus nerve;
Adrenaline / nor-adrenaline;
To S.A.N. / S.A node / sino-atrial node;
Increase in heart rate;
Increase in venous return;
Increase in stroke volume / ejection fraction;
Starlings Law of the heart.
4

Question 11

During a game, a player’s work rate will vary. Describe how the ‘parasympathetic’ and the
‘sympathetic’ nerve pathways control heart rate during a game.

Answer 11

Controlled by medulla / cardiac centre;
Sympathetic pathway increases heart rate;
By release of adrenaline / noradrenaline;
Increase stroke volume / ejection fraction;
Parasympathetic decreases HR;
By vagus nerve;
Production of Acetylcholine;
(Both) act on sino atrial node / SAN.