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Questions and Answers
What structure is responsible for preventing the heart from being susceptible to tetanus?
What structure is responsible for preventing the heart from being susceptible to tetanus?
The heart pumps blood throughout the body while only using two chambers.
The heart pumps blood throughout the body while only using two chambers.
False
What is the physiological basis for heart sounds?
What is the physiological basis for heart sounds?
The closure of heart valves.
The heart beats approximately _____ times in a year.
The heart beats approximately _____ times in a year.
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Match the following heart chambers with their primary functions:
Match the following heart chambers with their primary functions:
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What is the primary function of coronary circulation?
What is the primary function of coronary circulation?
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Cardiac action potentials are similar to those of skeletal muscle tissue.
Cardiac action potentials are similar to those of skeletal muscle tissue.
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What is the purpose of the heart valves?
What is the purpose of the heart valves?
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What is the primary function of pericardial fluid?
What is the primary function of pericardial fluid?
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The epicardium is the outermost layer of the heart wall.
The epicardium is the outermost layer of the heart wall.
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What type of tissue makes up the myocardium?
What type of tissue makes up the myocardium?
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The pericardial cavity is located between the parietal and _____ layers.
The pericardial cavity is located between the parietal and _____ layers.
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Match the following heart wall layers with their descriptions:
Match the following heart wall layers with their descriptions:
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What is the approximate weight of the heart in males?
What is the approximate weight of the heart in males?
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The apex of the heart points slightly to the right.
The apex of the heart points slightly to the right.
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What is the function of the fibrous pericardium?
What is the function of the fibrous pericardium?
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The heart is located in the __________ of the thoracic cavity.
The heart is located in the __________ of the thoracic cavity.
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Which part of the heart is formed by the left ventricle?
Which part of the heart is formed by the left ventricle?
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The anterior surface of the heart is deep to the sternum.
The anterior surface of the heart is deep to the sternum.
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Match the aspects of the pericardium with their descriptions:
Match the aspects of the pericardium with their descriptions:
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The __________ is the surface of the heart that faces the right lung.
The __________ is the surface of the heart that faces the right lung.
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Which part of the cardiac conduction system is known as the pacemaker of the heart?
Which part of the cardiac conduction system is known as the pacemaker of the heart?
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Cardiac muscle cells can only take in calcium from the sarcoplasmic reticulum.
Cardiac muscle cells can only take in calcium from the sarcoplasmic reticulum.
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How many signals does the SA node fire per minute on average?
How many signals does the SA node fire per minute on average?
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The cardiac conduction system is essential for maintaining the heart's _____ .
The cardiac conduction system is essential for maintaining the heart's _____ .
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Match the following components of the cardiac conduction system with their functions:
Match the following components of the cardiac conduction system with their functions:
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During which phase does the signal travel more slowly?
During which phase does the signal travel more slowly?
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The human heart beats approximately 60 times per minute.
The human heart beats approximately 60 times per minute.
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The signal in the cardiac conduction system travels towards the apex of the heart along the _____ branches.
The signal in the cardiac conduction system travels towards the apex of the heart along the _____ branches.
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What is the main way to control cardiac output?
What is the main way to control cardiac output?
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Cardiac muscle tissue is under voluntary control.
Cardiac muscle tissue is under voluntary control.
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What neurotransmitter is released by the vagus nerves to decrease heart rate?
What neurotransmitter is released by the vagus nerves to decrease heart rate?
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The _____ system is responsible for the fight or flight response.
The _____ system is responsible for the fight or flight response.
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Which receptor senses changes in blood pressure?
Which receptor senses changes in blood pressure?
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Norepinephrine is the hormone that decreases heart rate.
Norepinephrine is the hormone that decreases heart rate.
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Match each type of receptor with its function:
Match each type of receptor with its function:
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The _____ nervous system decreases heart rate by releasing acetylcholine.
The _____ nervous system decreases heart rate by releasing acetylcholine.
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Which ion primarily maintains the resting membrane potential in animal cells?
Which ion primarily maintains the resting membrane potential in animal cells?
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Cardiac action potentials have three distinct phases.
Cardiac action potentials have three distinct phases.
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What is the function of calcium (Ca^2+) release in cardiomyocytes?
What is the function of calcium (Ca^2+) release in cardiomyocytes?
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The channels that open during the depolarization phase of cardiac action potentials are called voltage-gated ________ channels.
The channels that open during the depolarization phase of cardiac action potentials are called voltage-gated ________ channels.
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Match each component of cardiac action potentials to its effect.
Match each component of cardiac action potentials to its effect.
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What is a refractory period in the context of cardiac action potentials?
What is a refractory period in the context of cardiac action potentials?
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Tetanus can occur in cardiac muscle cells.
Tetanus can occur in cardiac muscle cells.
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What happens to the membrane potential during the plateau phase of cardiac action potentials?
What happens to the membrane potential during the plateau phase of cardiac action potentials?
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Study Notes
Lecture Objectives
- Describe the human heart's anatomical location.
- Describe the heart's structure, including pericardium, heart wall, surfaces, apex, and base.
- Explain how the heart is divided into chambers and describe their structure.
- Compare heart chamber thicknesses and relate thickness to function.
- Describe the structure and function of heart valves.
- Trace blood flow through the heart, pulmonary, and systemic circulation.
- Trace blood flow through coronary circulation and describe its function.
- Describe the microscopic structure and function of cardiac muscle tissue.
- Explain the basis for autorhythmicity of cardiac muscle tissue.
- Describe the structure and function of the cardiac conduction system.
- Compare cardiac and skeletal muscle action potentials.
- Define refractory periods.
- Explain how heart structure prevents tetanus.
- Define electrocardiogram (ECG).
- Explain the P, QRS, and T waves of ECGs.
- Describe cardiac cycle events, especially blood pressure and volume.
- Define heart sounds and explain their physiological basis.
- Define cardiac output and factors regulating it/stroke volume and heart rate.
- Explain how exercise affects heart structure and function.
Anatomy of the Human Heart
- The heart is roughly the size of a clenched fist.
- It's located in the mediastinum of the thoracic cavity.
- Mass: ~250g in females, ~300g in males.
- The apex (pointed tip) rests on the diaphragm, slightly to the left.
- The base (opposite the apex) is angled slightly posterior.
- The heart is positioned with its right surface facing the right lung, left surface facing the left lung, and anterior surface deep to the sternum.
- The pericardium is a double-layered sac surrounding the heart:
- A fibrous pericardium, strong and inelastic, anchoring the heart in the mediastinum
- A serous pericardium, thinner and more fragile, divided into parietal (fused with fibrous) and visceral layers (also known as the epicardium). The pericardial fluid in between the layers reduces friction.
Heart Wall Structure
- The heart wall is composed of three layers:
- Epicardium (visceral layer of the serous pericardium), with connective tissue and fat.
- Myocardium, cardiac muscle tissue.
- Endocardium, lining the chambers and valves, continuous with blood vessels and reducing friction.
Chambers and Valves
- The heart has four chambers: two atria and two ventricles.
- Atria receive blood from veins and are thin-walled.
- Ventricles pump blood into arteries and are thicker-walled.
- The right ventricle is thinner than the left.
- Heart valves ensure unidirectional blood flow.
- Tricuspid and mitral (bicuspid) are atrioventricular valves.
- Pulmonary and aortic are semilunar valves.
- Valves open and close based on pressure differences.
Cardiac Conduction System
- The cardiac conducting system coordinates and regulates heart contractions.
- The sinoatrial (SA) node initiates the heartbeat (pacemaker).
- The atrioventricular (AV) node delays the signal to allow the atria to contract before the ventricles.
- Signals travel through the AV bundle (bundle of His), bundle branches, and Purkinje fibers to stimulate ventricle contractions.
Cardiac Action Potentials
- Cardiac action potentials are unique compared to skeletal muscle potentials due to a plateau phase.
- VGNCs initiate depolarization.
- VGCCs (voltage-gated calcium channels) maintain the plateau; it is important for the strong and sustained contraction of cardiac cells.
- Repolarization of cardiac cells brings the membrane back to its resting potential, allowing for the refractory period and preventing tetanus.
Structure and Function of Cardiac Muscle
- Cardiac muscle cells are branched, striated, and have a single nucleus.
- Intercalated discs contain desmosomes and gap junctions, allowing for coordinated contractions.
- Cardiac muscle tissue has a high density of mitochondria enabling high oxidative respiration.
- Calcium ions play a critical role in contraction.
Coronary Circulation
- Coronary vessels supply the heart with oxygenated blood.
- Coronary arteries branch from the aorta.
- Blood flows from high pressure in the coronary arteries to low pressure in coronary capillaries.
- Deoxygenated blood is returned to the heart by the coronary veins, emptying into the coronary sinus, which empties into the right atrium.
ECG (Electrocardiogram)
- An ECG records electrical activity in the heart.
- P wave: atrial depolarization (contraction).
- QRS complex: ventricular depolarization (contraction).
- T wave: ventricular repolarization (relaxation).
- The intervals and segments between waves provide additional information.
Cardiac Cycle
- The cardiac cycle is a complete cycle of contraction and relaxation of the heart.
- Atrial systole and diastole: The atria contract to fill the ventricles. Ventricles fill with blood as atria relax.
- Ventricular systole and diastole: The ventricles contract to pump blood into the arteries. The ventricles relax and refill with blood from the atria.
- Pressure changes drive valve openings and closings.
- Heart sounds are produced by blood turbulence related to valve closure.
- S1 (lub): AV valves closing.
- S2 (dup): Semilunar valves closing.
Cardiac Output
- Cardiac output (CO) is the amount of blood pumped per minute.
- Stroke volume (SV): Volume of blood pumped per contraction.
- Heart rate (HR): Number of contractions per minute.
- CO = SV × HR.
- Cardiac reserve is the difference between maximum and resting CO.
Regulation of Cardiac Activity
- The autonomic nervous system (ANS) regulates heart activity, influencing heart rate and stroke volume.
- Sympathetic stimulation increases heart rate and contractility via norepinephrine.
- Parasympathetic stimulation (vagus nerve) decreases heart rate via acetylcholine.
- Other factors affecting heart rate and contractility include hormones and body temperature.
- Exercise, for example, increases cardiac output through increased heart rate and stroke output.
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Description
Test your knowledge on the anatomy and physiology of the heart with this quiz. Explore topics such as heart chambers, circulation, heart sounds, and the structure of heart tissues. This quiz is ideal for students studying cardiovascular biology or related health sciences.
