3.6.1.3 Control of heart rate

What is the primary function of the sinoatrial node (SAN) in the heart?

• To delay the electrical impulse

• To act as the heart's natural pacemaker

• To conduct impulses to the ventricles

• To increase heart rate during exercise

Answer explanation

The sinoatrial node (SAN) is the heart's natural pacemaker, generating electrical impulses that initiate the heartbeat. This makes it crucial for maintaining the heart's rhythm, unlike the other options which describe different functions.

Where is the atrioventricular node (AVN) located in the heart?

• In the right atrium

• In the left atrium

• Between the atria and ventricles

• In the right ventricle

Answer explanation

The atrioventricular node (AVN) is located between the atria and ventricles. It plays a crucial role in the heart's electrical conduction system, coordinating the timing of atrial and ventricular contractions.

What is the role of Purkyne tissue in the heart?

• To initiate the heartbeat

• To delay the electrical impulse

• To conduct electrical impulses rapidly to the ventricles

• To regulate blood pressure

Answer explanation

Purkyne tissue conducts electrical impulses rapidly to the ventricles, ensuring coordinated contraction and efficient pumping of blood. This is crucial for maintaining a proper heartbeat rhythm.

Which of the following best describes myogenic stimulation?

• Heartbeat initiated by external nerves

• Heartbeat initiated by the heart muscle itself

• Heartbeat controlled by hormones

• Heartbeat regulated by blood pressure

Answer explanation

Myogenic stimulation refers to the heart's ability to initiate its own heartbeat through the heart muscle itself, rather than relying on external nerves, hormones, or blood pressure regulation.

What is the primary role of chemoreceptors in the cardiovascular system?

• To detect changes in blood pressure

• To detect changes in blood pH and carbon dioxide levels

• To regulate heart rate directly

• To control the contraction of the heart muscle

Answer explanation

Chemoreceptors primarily detect changes in blood pH and carbon dioxide levels, which are crucial for regulating respiratory and cardiovascular functions, rather than directly regulating heart rate or blood pressure.

Where are pressure receptors, also known as baroreceptors, primarily located?

• In the brain

• In the carotid arteries and aorta

• In the ventricles of the heart

• In the lungs

Answer explanation

Baroreceptors, or pressure receptors, are primarily located in the carotid arteries and aorta. They detect changes in blood pressure and help regulate cardiovascular function.

How does the autonomic nervous system influence heart rate?

• By directly stimulating the heart muscle

• By releasing hormones into the bloodstream

• By adjusting the rate of electrical impulses from the SAN

• By changing the volume of blood in the heart

Answer explanation

The autonomic nervous system influences heart rate by adjusting the rate of electrical impulses from the sinoatrial node (SAN), which acts as the heart's natural pacemaker, regulating how fast the heart beats.

Which part of the autonomic nervous system is responsible for increasing heart rate?

• Parasympathetic nervous system

• Sympathetic nervous system

• Central nervous system

• Peripheral nervous system

Answer explanation

The sympathetic nervous system is responsible for the 'fight or flight' response, which includes increasing heart rate to prepare the body for action. In contrast, the parasympathetic nervous system decreases heart rate.

What effect does the parasympathetic nervous system have on heart rate?

• It increases heart rate

• It decreases heart rate

• It has no effect on heart rate

• It causes irregular heartbeats

Answer explanation

The parasympathetic nervous system primarily functions to decrease heart rate by promoting relaxation and reducing the body's stress response, making 'It decreases heart rate' the correct choice.

Which of the following is an effector in the control of heart rate?

• Sinoatrial node

• Atrioventricular node

• Heart muscle

• Purkyne tissue

Answer explanation

The heart muscle is the effector that responds to signals from the sinoatrial and atrioventricular nodes, contracting to pump blood and thus directly controlling heart rate.