Control of Heart Rate

What is the correct order of electrical activity during a cardiac cycle?

• AVN -> SAN -> Bundle of His -> Purkinje fibres

• SAN -> AVN -> Bundle of His -> Purkinje fibres

• AVN -> Purkinje fibres -> SAN -> Bundle of His

• SAN -> Bundle of His -> AVN -> Purkinje fibres

Chemoreceptors in the carotid bodies are triggered by

• oxygen concentration

• Na+ concentration

• blood pH

• blood glucose concentration

The ____ acts as the heart's pacemaker.

• AVN

• Bundle of His

• cardiac myogenic tissue

• SAN

The wave of electrical activity in the sinoatrial node causes the ventricles to contract.

• True

• False

Slowing down the heart rate is the job of the...

• parasympathetic nerve

• sympathetic nerve

• trigeminal nerve

• vagus nerve

Sensory input from the baroreceptors in the aorta is fed to the ______ in the brain.

• Cerebellum

• Cerebrum

• Hypothalamus

• Medulla oblongata

In addition to increased heart rate, an increased concentration of CO₂ will lead to...

• a decrease in blood pressure

• an increase in respiratory rate

• a decrease in respiratory rate

• an increase in salivation

SAN activity immediately leads to... [2]

• the atrioventricular valves opening

• semilunar valve

• atrial systole

• atrial diastole

• ventricular systole

Movement of blood in the heart is from

• low -> high pressure

• high -> low pressure

Why doesn't the SAN send the entire heart contracting at the same time? [2]

• The Purkinje fibres prevent the contraction of ventricular walls

• Chambers that are not stretched are unable to contract

• Non-conducting tissue prevents immediate contraction of ventricles

• The AVN delays the impulse, allowing the ventricles to fill