Heart - Physiology GPT 1

Question 1

Define autorhythmic cells in the context of the heart.

Answer 1

Autorhythmic cells are specialized cardiac muscle cells that can generate their electrical impulses, regulating the heartbeat.

Question 2

Where is the sinoatrial (SA) node located, and what is its role in establishing heart rhythm?

Answer 2

The sinoatrial (SA) node, also known as the pacemaker, is located in the right atrium and initiates each heartbeat by sending electrical impulses to the atria.

Question 3

Elaborate on the function and location of the atrioventricular (AV) node in the heart.

Answer 3

The atrioventricular (AV) node is located in the interatrial septum and functions as an electrical relay, slowing down the electrical signal to allow the ventricles to fill with blood.

Question 4

What is the pacemaker potential, and how does it contribute to heart rhythm?

Answer 4

The pacemaker potential is the gradual depolarization of the SA node cells that leads to the threshold for firing an action potential. It sets the basic rhythm of the heart.

Question 5

How does the SA node determine the basic heart rhythm, and why is it called the primary pacemaker?

Answer 5

The SA node is called the primary pacemaker because it typically has the fastest intrinsic rhythm and serves as the dominant controller of heart rate.

Question 6

What is the function of the atrioventricular (AV) bundle and its relationship to the ventricles?

Answer 6

The atrioventricular (AV) bundle, also known as the bundle of His, is a bundle of specialized muscle fibers that conducts the electrical impulses from the AV node to the bundle branches.

Question 7

Describe the path of impulse conduction through the AV bundle and bundle branches.

Answer 7

The impulse travels through the AV bundle and its bundle branches to reach the Purkinje fibers in the ventricles.

Question 8

How do conducting cells distribute the contractile stimulus throughout the heart?

Answer 8

Conducting cells distribute the contractile stimulus throughout the heart to coordinate and synchronize the contraction of cardiac muscle cells.

Question 9

What is the significance of Purkinje fibers in the cardiac conduction system?

Answer 9

Purkinje fibers are specialized cardiac muscle fibers responsible for quickly transmitting electrical impulses to the contractile cells of the ventricles, ensuring the coordinated and efficient contraction of these chambers.

Question 10

Explain how the Purkinje fibers transmit electrical impulses to the contractile cells of the ventricles.

Answer 10

Purkinje fibers transmit electrical impulses to the contractile cells by propagating the action potential throughout the ventricles, leading to their contraction.

Question 11

Define bradycardia and discuss the potential causes and consequences of a slow heart rate.

Answer 11

Bradycardia is a slow heart rate, which can result from various causes, including issues with the SA node or damage to the conduction system. It can lead to insufficient blood flow and related symptoms.

Question 12

What is tachycardia, and how does it impact heart rate and cardiac function?

Answer 12

Tachycardia is a fast heart rate, often exceeding 100 beats per minute at rest, and it can be caused by various factors, including stress, certain medical conditions, or stimulants. It can lead to reduced cardiac efficiency.

Question 13

Describe the role of ectopic pacemakers in heart rhythm disturbances.

Answer 13

Ectopic pacemakers are cells or tissues outside the SA node that can spontaneously generate electrical impulses, leading to irregular heart rhythms or arrhythmias.

Question 14

What is an electrocardiogram (ECG), and what specific aspects of heart activity does it record?

Answer 14

An electrocardiogram (ECG or EKG) is a graphical representation of the electrical activity of the heart. It records various aspects of heart activity, including depolarization and repolarization of cardiac cells.

Question 15

Define the P wave in an ECG, and explain when it occurs during the cardiac cycle.

Answer 15

The P wave on an ECG represents atrial depolarization, which occurs as the electrical impulse moves through the atria, leading to atrial contraction.

Question 16

Identify the QRS complex in an ECG, and elucidate its relationship to ventricular depolarization.

Answer 16

The QRS complex on an ECG represents ventricular depolarization, signifying the onset of ventricular contraction.

Question 17

What does the T wave represent in an ECG, and when does it occur in the cardiac cycle?

Answer 17

The T wave on an ECG represents ventricular repolarization, indicating the recovery of the ventricles after contraction.

Question 18

Describe the structure and function of intercalated discs in cardiac muscle cells.

Answer 18

Intercalated discs are specialized structures found in cardiac muscle cells that help hold adjacent cells together, both structurally and electrically. They contain gap junctions for electrical communication.

Question 19

What is the resting membrane potential in cardiac contractile cells, and how does it affect electrical excitability?

Answer 19

The resting membrane potential in cardiac contractile cells is approximately -90 mV, making these cells electrically excitable.

Question 20

Explain the key events in the rapid depolarization phase of the action potential in cardiac cells.

Answer 20

During the rapid depolarization phase of the action potential in cardiac cells, sodium channels open, allowing an influx of sodium ions and initiating depolarization.

Question 21

What is the importance of the plateau phase in the cardiac muscle action potential?

Answer 21

The plateau phase in the cardiac muscle action potential is characterized by the influx of calcium ions and the efflux of potassium ions, which help maintain the depolarized state, enabling sustained contraction.

Question 22

Summarize the three main phases of the action potential in cardiac contractile cells.

Answer 22

The action potential in cardiac contractile cells consists of three main phases: rapid depolarization, plateau, and repolarization.

Question 23

What happens during the rapid depolarization phase of the action potential, and what ion channels are involved?

Answer 23

During the rapid depolarization phase of the action potential, voltage-gated sodium channels open, allowing sodium ions to enter the cell and depolarize it.

Question 24

How do potassium channels contribute to the repolarization phase of the action potential?

Answer 24

Potassium channels play a key role in the repolarization phase of the action potential by allowing potassium ions to exit the cell, restoring the resting membrane potential.

Question 25

What is the significance of calcium channels in the plateau phase of the action potential?

Answer 25

Calcium ions are essential during the plateau phase of the action potential, as they contribute to the prolonged depolarization of the cell, allowing for sustained muscle contraction.

Question 26

Define the refractory period in cardiac contractile cells, and explain its significance.

Answer 26

The refractory period in cardiac contractile cells refers to a period during and after an action potential when the cell is less responsive to stimulation.

Question 27

Differentiate between the absolute and relative refractory periods in cardiac muscle cells.

Answer 27

There are two phases of the refractory period: the absolute refractory period, during which the cell cannot respond to any stimulus, and the relative refractory period, during which a stronger-than-normal stimulus can trigger a response.

Question 28

How does the refractory period prevent tetanus (sustained muscle contraction) in cardiac muscle?

Answer 28

The refractory period prevents tetanus (sustained muscle contraction) in cardiac muscle by ensuring that the heart muscle has enough time to relax and refill with blood between beats.

Question 29

Describe how cardiac contractile cells increase the concentration of calcium ions around myofibrils for contraction.

Answer 29

Calcium ions play a crucial role in cardiac muscle contractions by binding to the regulatory protein troponin, which then allows myosin and actin to interact, leading to muscle contraction.

Question 30

What is the role of calcium in cardiac muscle contractions, and how does it differ from skeletal muscle contraction?

Answer 30

In cardiac muscle, the influx of calcium ions is the primary trigger for muscle contraction. This differs from skeletal muscle, where calcium release from the sarcoplasmic reticulum initiates contraction.

Question 31

How do calcium ions interact with troponin and tropomyosin in the regulation of cardiac muscle contraction?

Answer 31

Calcium ions interact with troponin and tropomyosin to enable the myosin cross-bridges to attach to actin filaments and initiate the sliding of actin and myosin, resulting in muscle contraction.

Question 32

Explain how cardiac contractile cells obtain energy for contractions.

Answer 32

Cardiac contractile cells obtain energy for contractions primarily through aerobic metabolism, which occurs in mitochondria.

Question 33

Describe the roles of mitochondria and myoglobin in cardiac muscle metabolism.

Answer 33

Mitochondria in cardiac muscle cells produce adenosine triphosphate (ATP), the primary energy molecule, through oxidative phosphorylation.

Question 34

How does the demand for oxygen and nutrients in cardiac muscle differ from other tissues?

Answer 34

The demand for oxygen and nutrients in cardiac muscle is high due to the continuous pumping of blood and the need for a constant energy supply. Cardiac muscle has a high density of mitochondria and myoglobin, which helps facilitate energy production and oxygen storage.

Question 35

What are the key phases of the cardiac cycle, and what happens during each phase?

Answer 35

The key phases of the cardiac cycle include atrial systole, isovolumetric ventricular contraction, ventricular ejection, isovolumetric ventricular relaxation, and ventricular filling.

Question 36

How does the volume and pressure within the heart chambers change during the cardiac cycle?

Answer 36

During the cardiac cycle, volume and pressure within the heart chambers change to facilitate the movement of blood from the atria to the ventricles and then into the pulmonary and systemic circulations.

Question 37

Describe the significance of isovolumetric contraction and relaxation in the cardiac cycle.

Answer 37

Isovolumetric contraction and relaxation phases occur when all heart valves are closed, preventing blood from entering or leaving the ventricles.

Question 38

What are the heart sounds S1 and S2, and what events in the cardiac cycle produce these sounds?

Answer 38

Heart sounds are audible events associated with the closure of heart valves. The two main heart sounds are S1 (the “lub” sound) and S2 (the “dub” sound).

Question 39

Explain the conditions that might lead to the production of abnormal heart sounds, such as murmurs.

Answer 39

Abnormal heart sounds, such as murmurs, can occur due to various factors, including valvular defects, stenosis, or regurgitation.

Question 40

Define and describe heart sounds S3 and S4, including their clinical significance.

Answer 40

Additional heart sounds, S3 and S4, may be heard and can indicate underlying cardiac conditions. S3 occurs in early diastole, and S4 occurs in late diastole.

Question 41

What is cardiac output, and how is it calculated using heart rate and stroke volume?

Answer 41

Cardiac output is the volume of blood that the heart pumps per minute and is calculated by multiplying heart rate (beats per minute) by stroke volume (the volume of blood ejected by each ventricle in one beat).

Question 42

Explain the relationship between heart rate and cardiac output.

Answer 42

There is a direct relationship between heart rate and cardiac output. An increase in heart rate leads to an increase in cardiac output, assuming stroke volume remains constant.

Question 43

What factors can influence stroke volume and, consequently, cardiac output?

Answer 43

Stroke volume, the amount of blood ejected from each ventricle with each heartbeat, can be influenced by factors such as preload (end-diastolic volume) and afterload (the pressure the heart must overcome to pump blood).

Question 44

How does the autonomic nervous system regulate heart rate, and what are the roles of sympathetic and parasympathetic divisions?

Answer 44

The autonomic nervous system (ANS) regulates heart rate. The sympathetic division increases heart rate, while the parasympathetic division decreases it.

Question 45

Discuss the influence of hormones, body temperature, and age on heart rate regulation.

Answer 45

Hormones such as epinephrine and norepinephrine can increase heart rate and contractility. Body temperature elevation can also lead to an increase in heart rate.

Question 46

What is the role of venous return in heart rate regulation, and how does the Bainbridge reflex respond to changes in venous return?

Answer 46

Venous return refers to the volume of blood returning to the heart, and it affects stroke volume and, consequently, cardiac output. The Bainbridge reflex responds to changes in venous return and adjusts heart rate accordingly.

Question 47

Explain the concept of preload and afterload and their impact on heart rate and stroke volume.

Answer 47

Preload is the degree of stretch of cardiac muscle fibers just before they contract, and afterload is the pressure the heart must overcome to pump blood. These factors influence stroke volume and, by extension, cardiac output. An increase in preload typically increases stroke volume and cardiac output, while an increase in afterload can reduce stroke volume and cardiac output.