Cardiovascular System Quiz 2

Questions and Answers

What are the two types of myocytes in cardiac muscle, and what are their primary functions?

The two types of myocytes in cardiac muscle are contractile cells, which are responsible for contraction, and pacemaker cells, which initiate depolarization spontaneously.

Describe the role of the sinoatrial (SA) node in the cardiac conduction system.

The sinoatrial (SA) node acts as the heart's natural pacemaker, generating electrical impulses that initiate the heartbeat.

What happens at the atrioventricular (AV) node during the cardiac conduction process?

At the AV node, the electrical impulses pause for about 0.1 seconds, allowing the atria to finish contracting before the ventricles begin to contract.

How do the bundle branches contribute to the conduction of impulses within the heart?

The bundle branches conduct impulses through the interventricular septum, ensuring that the electrical signal reaches both ventricles simultaneously. Signup and view all the answers

Explain the function of the subendocardial conducting network in the heart.

The subendocardial conducting network, also known as Purkinje fibers, depolarizes the contractile cells of both ventricles, leading to their contraction. Signup and view all the answers

Why can't tetanic contractions occur in cardiac muscles?

Tetanic contractions cannot occur in cardiac muscles due to the longer absolute refractory period, which allows the heart muscle to fully relax between beats. Signup and view all the answers

What is the role of the sinoatrial (SA) node in the cardiac conduction system?

The sinoatrial (SA) node generates electrical impulses that initiate the heartbeat and set the heart rate at approximately 75 beats per minute. Signup and view all the answers

Explain the benefit of having a longer action potential and contraction duration in cardiac muscles.

The longer action potential and contraction duration in cardiac muscles allow for sustained contraction, ensuring effective ejection of blood. Signup and view all the answers

What happens if the SA node becomes defective?

If the SA node becomes defective, a mechanical pacemaker may be implanted to regulate the heart rate artificially. Signup and view all the answers

Describe the pathway of electrical impulses from the SA node to the ventricles.

The electrical impulses generated by the SA node travel through the internodal pathway to the AV node, pause briefly, then proceed to the AV bundle and down the bundle branches before reaching the Purkinje fibers in the ventricles. Signup and view all the answers

Study Notes

Basic Cardiac Anatomy

Heart consists of two types of myocytes: contractile cells for contraction and pacemaker cells for initiating electrical impulses.
Pacemaker cells can spontaneously depolarize, initiating heartbeats without nervous input.

Skeletal Muscle vs. Cardiac Muscle

Cardiac muscle has a longer absolute refractory period compared to skeletal muscle, preventing tetanic contractions.
This long refractory period allows for efficient blood ejection and sustained contractions.

Electrical Activity and ECG

The sinoatrial (SA) node is the primary pacemaker, generating impulses at a rate of 75 beats per minute.
Atrioventricular (AV) node has a firing rate of 40-60 beats per minute; ventricular cells fire at 30 beats per minute.
ECG measures the heart's electrical activity, recording a composite of all heart cell potentials rather than a single action potential.
Leads in a 12-lead ECG provide a comprehensive view of the heart's activity from multiple angles.

Cardiac Cycle

The ECG shows different waves and segments including P wave (atrial depolarization), QRS complex (ventricular depolarization), and T wave (ventricular repolarization).
The PR interval is approximately 0.2 seconds, indicating the time taken for impulse transmission from atria to ventricles.

Heart Rate and Regulation

Normal heart rate ranges from 60 to 100 beats per minute; bradycardia is defined as a rate below 60, and tachycardia is above 100.
The Rule of 300 can be used to estimate heart rate by dividing 300 by the number of large boxes between QRS complexes on the ECG.

Rhythm and Abnormalities

Normal sinus rhythm originates from the SA node, with P waves preceding every QRS complex.
Heart blocks include first-degree (PR interval >0.2 seconds), second-degree (two types), and third-degree heart blocks.
Atrial fibrillation and ventricular tachycardia indicate abnormal rhythms; ventricular fibrillation results in disorganized electrical activity and chaotic ECG patterns, common in acute heart attacks.

Description

This quiz covers key concepts of the cardiovascular system, focusing on basic cardiac anatomy, the differences between skeletal and cardiac muscle, and the cardiac cycle. It also explores the correlation of electrical activity with ECG and how cardiac output is regulated.