Podcast Beta
Questions and Answers
What initiates the sequence of excitation in the heart?
Which wave on the electrocardiogram corresponds to the depolarization of the ventricles?
During which phase of the cardiac cycle do the AV valves close due to rising ventricular pressure?
What primarily happens during the isovolumetric relaxation phase of the cardiac cycle?
Signup and view all the answers
Which part of the heart's conduction system is responsible for delaying the impulse after it passes from the SA node?
Signup and view all the answers
What event corresponds with the T wave in an electrocardiogram?
Signup and view all the answers
In which phase of the cardiac cycle does the heart experience the lowest blood pressure as blood enters the ventricles?
Signup and view all the answers
Which structure carries the impulse toward the heart apex and ventricular walls?
Signup and view all the answers
What leads to the opening of the semilunar valves during the cardiac cycle?
Signup and view all the answers
What is most likely masked by the larger QRS complex in an electrocardiogram?
Signup and view all the answers
What causes the brief rise in aortic pressure known as h?
Signup and view all the answers
What primarily stimulates the heart's activity?
Signup and view all the answers
Which heart sounds correspond to the closing of the heart valves?
Signup and view all the answers
How is cardiac output (CO) defined?
Signup and view all the answers
What is cardiac reserve?
Signup and view all the answers
What are the components used to calculate cardiac output?
Signup and view all the answers
If heart rate is 75 beats/min and stroke volume is 70 ml/beat, what is the cardiac output?
Signup and view all the answers
Which statement accurately describes the role of the parasympathetic cardioinhibitory center?
Signup and view all the answers
Which of the following best describes stroke volume?
Signup and view all the answers
What is the normal heart sound known as?
Signup and view all the answers
Study Notes
Heart Physiology: Sequence of Excitation
- The Sinoatrial (SA) node, the heart's natural pacemaker, generates impulses approximately 75 times per minute.
- The Atrioventricular (AV) node delays the impulse for approximately 0.1 seconds, allowing the atria to contract and fully fill the ventricles with blood.
- The impulse travels from the atria to the ventricles via the atrioventricular bundle (bundle of His).
- The AV bundle splits into two branches within the interventricular septum, known as bundle branches.
- The bundle branches conduct the impulse towards the apex of the heart.
- The Purkinje fibers, a specialized network of fibers, carry the impulse to the heart apex and ventricular walls, triggering ventricular contraction.
Electrocardiography
- Electrical activity in the heart can be recorded using an electrocardiogram (ECG or EKG).
- The P wave represents atrial depolarization, the electrical signal that initiates atrial contraction.
- The QRS complex reflects ventricular depolarization, the electrical signal that initiates ventricular contraction.
- The T wave represents ventricular repolarization, the return of the ventricles to their resting state.
- Atrial repolarization is masked by the larger QRS complex on the ECG.
Cardiac Cycle
- The cardiac cycle encompasses all events associated with blood flow through the heart.
- Systole refers to the contraction phase of the heart muscle.
- Diastole refers to the relaxation phase of the heart muscle.
Phases of the Cardiac Cycle
- Ventricular filling: Occurs during mid-to-late diastole when heart blood pressure is low, allowing blood to flow from the atria into the ventricles. The AV valves are open, and atrial systole, contraction of the atria, further fills the ventricles.
-
Ventricular systole: Atria relax, and increasing ventricular pressure causes the AV valves to close (lub sound).
- Isovolumetric contraction phase: The ventricles contract but no blood is ejected as the valves are closed.
- Ventricular ejection phase: The pressure in the ventricles exceeds that in the aorta and pulmonary trunk, opening the semilunar valves and ejecting blood.
- Isovolumetric relaxation: Occurs early in diastole when the ventricles relax, and the backflow of blood in the aorta and pulmonary trunk closes the semilunar valves (dup sound).
- Dicrotic notch: A brief rise in aortic pressure caused by the backflow of blood rebounding off the closed semilunar valves.
Extrinsic Innervation of the Heart
- The heart is stimulated by the sympathetic cardioacceleratory center, which increases heart rate and contractility.
- The heart is inhibited by the parasympathetic cardioinhibitory center, which decreases heart rate and contractility.
Cardiac Output (CO) and Reserve
- CO is the volume of blood pumped by each ventricle per minute: CO = HR x SV.
- Heart rate (HR) is the number of heartbeats per minute.
- Stroke volume (SV) is the volume of blood ejected from a ventricle with each beat.
- Cardiac reserve is the difference between resting CO and maximal CO, representing the heart's ability to increase output during exercise or stress.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Explore the key components of heart physiology, including the sequence of excitation that leads to heartbeats. Understand how the Sinoatrial node functions as the natural pacemaker and the role of electrocardiography in monitoring heart activity.
