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Questions and Answers
What is the primary function of the sinoatrial node (SAN) in the heart?
What is the primary function of the sinoatrial node (SAN) in the heart?
How does the atrioventricular node (AVN) contribute to the heart's electrical conduction?
How does the atrioventricular node (AVN) contribute to the heart's electrical conduction?
Which structure prevents direct electrical activity from the atria to the ventricles?
Which structure prevents direct electrical activity from the atria to the ventricles?
What regulates the firing rate of the sinoatrial node (SAN)?
What regulates the firing rate of the sinoatrial node (SAN)?
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What type of receptors are involved in detecting high and low blood pressure?
What type of receptors are involved in detecting high and low blood pressure?
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Which of the following statements accurately describes cardiac muscle?
Which of the following statements accurately describes cardiac muscle?
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The coordinated contraction of the heart muscle is primarily due to which component of the conducting system?
The coordinated contraction of the heart muscle is primarily due to which component of the conducting system?
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What is the role of chemoreceptors in heart function?
What is the role of chemoreceptors in heart function?
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What is the primary role of receptors in monitoring blood composition?
What is the primary role of receptors in monitoring blood composition?
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Which segment of an ECG is indicative of ventricular repolarization?
Which segment of an ECG is indicative of ventricular repolarization?
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What occurs during the systolic phase of the cardiac cycle?
What occurs during the systolic phase of the cardiac cycle?
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How is cardiac output (CO) calculated?
How is cardiac output (CO) calculated?
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What does the QRS complex represent in an ECG?
What does the QRS complex represent in an ECG?
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What characterizes diastole in the cardiac cycle?
What characterizes diastole in the cardiac cycle?
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In the context of the autonomic nervous system, which neurons are involved in sending impulses to the SAN?
In the context of the autonomic nervous system, which neurons are involved in sending impulses to the SAN?
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What does the term 'end systolic volume' refer to?
What does the term 'end systolic volume' refer to?
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Study Notes
Heart Rate Control
- The heart's rhythmic beating is controlled by cardiac muscle.
- Heart rate regulation involves the brain and the autonomic nervous system.
- Cardiac muscle is myogenic meaning it can contract and relax without nerve signals.
Intended Learning Outcomes
- Describe the position and function of the heart's conducting system (SA and AV nodes, AV bundle, bundle of His and Purkinje fibres).
- Describe the regulation of heart rate.
- Describe a normal ECG reading (PQRST) and relate it to the conducting pathway.
- Explain the cardiac cycle including systole and diastole.
- Define cardiac output, stroke volume, end diastolic volume and end systolic volume.
Control of Heart Rate
- Cardiac muscle controls the regular beating of the heart.
- The brain and autonomic nervous system regulate heart rate.
Cardiac Muscle
- Cardiac muscle (myogenic) can contract and relax independently without nerve impulses.
- This pattern of contraction controls the heartbeat.
Conducting System of the Heart
- Electrical activity starts in the sinoatrial node (SAN).
- The SAN acts as a pacemaker, setting the heartbeat rhythm.
- Electrical signals are sent to atrial walls, causing atrial contraction.
- A band of non-conducting collagen tissue prevents signals from directly reaching ventricles.
- Electrical signals are transferred to atrioventricular node (AVN).
- The AVN introduces a slight delay before signals pass to the bundle of His, ensuring atrial emptying before ventricular contraction.
Regulation of the Heartbeat
- The cardiovascular (CV) center in the brain receives input from higher brain centers, sensory receptors (proprioceptors, chemoreceptors, baroreceptors).
- Output to the heart regulates heart rate.
- Cardiac accelerator nerves (sympathetic) increase heart rate and contractility.
- Vagus nerves (parasympathetic) decrease heart rate.
- The rate at which the SAN fires is unconsciously controlled by the medulla oblongata.
Control of Heart Rate Involves the Brain and Autonomic Nervous System
- The sinoatrial node (SAN) generates electrical impulses to contract the cardiac muscles.
- The rate at which the SAN fires is unconsciously controlled by the medulla oblongata.
- The rate adjusts to respond to internal stimuli.
Stimuli Detected by Receptors Cause Heart Rate to Speed up or Slow Down
- Pressure receptors (baroreceptors) and chemical receptors (chemoreceptors) detect stimuli.
- The medulla process information, sending impulses to the SAN along sympathetic or parasympathetic neurons.
ECG Related to Conducting System
- The P wave in an ECG represents atrial depolarization spreading through the atria.
- The QRS complex represents rapid ventricular depolarization through the ventricles.
- The T wave represents ventricular repolarization.
- During the plateau period of depolarization, the ECG tracing is flat.
Cardiac Cycle
- The cardiac cycle is a continuous sequence of atrial and ventricular contraction and relaxation.
- Blood moves continuously throughout the body.
- Volume and pressure changes in the atria and ventricles occur during different stages.
Define Systole and Diastole
- Systole is the period of contraction, wherein the heart pumps blood.
- Diastole is the period of relaxation, during which chambers fill with blood.
Define Cardiac Output and Stroke Volume
- Cardiac output (CO) is the volume of blood ejected by a ventricle in one minute.
- Stroke volume (SV) is the volume of blood ejected by a ventricle in one contraction.
- CO = SV x HR (heart rate).
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Description
This quiz focuses on the mechanisms of heart rate control and the functions of cardiac muscle. It covers the heart's conducting system, normal ECG readings, and the cardiac cycle. You will also learn about important terms like cardiac output and stroke volume.
