Questions and Answers
What is the blood pressure in the pulmonary circuit?
Which side of the heart pumps blood into the pulmonary artery?
What is the sequence of blood flow from the organs to the heart?
What is the output of the left ventricle?
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What is the normal blood pressure in the systemic circuit?
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What fills the left ventricle?
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What is the sequence of blood flow from the heart to the organs?
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What regulates the output of the heart?
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What is the function of desmosomes in cardiac muscle?
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What is the term for the ability of cardiac muscle cells to function together as a single unit?
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What is the purpose of the fibrous tissue that separates the atria from the ventricles?
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What is the term for the electrical potential difference between the inside and outside of a cell?
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What is the main function of ion channels in cardiac muscle cells?
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What is the term for the ability of an ion channel to only allow a specific type of ion to pass through?
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What is the term for the ability of an ion channel to open and close in response to changes in the transmembrane potential?
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What is the term for the movement of ions down their concentration gradient?
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What is the term for the ability of cardiac muscle cells to spontaneously depolarize?
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What is the purpose of the action potential in cardiac muscle cells?
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What is the effect of increased stretch of ventricular muscle on the formation of cross-bridges?
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What is the effect of sympathetic stimulation on the sinoatrial (SA) node action potential?
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What is the effect of parasympathetic stimulation on the heart rate?
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What is the importance of the Frank-Starling effect?
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What is the effect of inotropic agents such as adrenaline on the heart?
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What is the effect of aging on the blood vessels?
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What is the role of the sympathetic nervous system on the heart?
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What is the role of the parasympathetic nervous system on the heart?
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What is the normal resting heart rate?
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What is the effect of increased intracellular Ca2+ on the heart?
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What is the effect of parasympathetic nerve stimulation on pacemaker cells?
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What is the effect of sympathetic nerve stimulation on pacemaker cells?
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What is the function of baroreceptors in the carotid artery?
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What is the equation for blood pressure?
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What determines systolic blood pressure?
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What is the function of elastic tissue in blood vessel walls?
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What is the primary mechanism for blood pressure regulation in an acute setting?
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What causes vasoconstriction?
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What is the main change in the large arteries with age that contributes to hypertension?
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What is the effect of vasoconstriction on blood flow?
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What is the primary mechanism of blood pressure regulation in chronic hypertension?
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What is the effect of aging on blood pressure?
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What is the type of hypertension that has an identifiable cause?
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What is the result of the inflammatory response in the pathogenesis of atherosclerosis?
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What is a common effect of hypertension on the body?
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What is a risk factor for essential hypertension?
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What is the term for the initial event in the pathogenesis of atherosclerosis according to the response to injury hypothesis?
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What is a consequence of dysfunctional endothelium in hypertensive patients?
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What is the common underlying mechanism of various diseases, including ischaemic heart disease, cerebrovascular disease, and renal disease?
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What is a characteristic of atherosclerotic plaques?
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What does the P wave on an ECG trace primarily represent?
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Which part of the ECG represents ventricular depolarization?
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What is indicated by a prolonged PR interval on an ECG?
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How is stroke volume calculated?
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What initiates the pacemaker potential in the SAN cells?
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What represents the resting membrane potential on an ECG?
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What does the height of the R wave in the QRS complex suggest?
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How often does the sinoatrial node generate action potentials at rest?
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What influences the preload of the heart?
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What is the role of calcium during the action potential in cardiac muscle cells?
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Which type of calcium channels play a primary role in calcium-induced calcium release?
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What is the approximate end diastolic volume (EDV) of the ventricles at rest?
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What does the T wave on an ECG represent?
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What triggers the rapid depolarization in pacemaker cells after the threshold is reached?
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Which of the following is NOT a factor influencing stroke volume?
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What effect do sympathetic and parasympathetic nerves have on the sinoatrial node?
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What type of channel opens first as the membrane potential begins to depolarize in the SAN?
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What is indicated by Einthoven's Triangle in cardiac physiology?
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Which ion is primarily responsible for repolarization during the cardiac action potential?
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What characterizes the plaque in the marginal branch of the coronary artery?
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Which lipid component is primarily modified and contributes to the development of arterial plaque?
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What is the consequence of a thin fibrous cap on an atherosclerotic plaque?
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What initial injury initiates the process of plaque formation in coronary arteries?
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What type of cells form the 'fatty streak' in the arterial wall?
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Which of the following describes the role of smooth muscle cells in plaque development?
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What process involves macrophages ingesting modified LDL within the arterial wall?
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What is a significant characteristic of fibrotic plaque in coronary arteries?
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What is the name of the phase during which the heart relaxes and refills with blood?
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Which valve closes during ventricular isovolumetric contraction?
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What is the role of the pulmonary veins in the circulatory system?
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What are the two main categories of heart failure?
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What is the primary mechanism that causes pressure changes within the heart during the cardiac cycle?
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What event occurs immediately after the mitral valve closes during the cardiac cycle?
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Which of the following is NOT a phase of the cardiac cycle?
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What is the primary function of the heart valves?
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Where does mixed venous blood, returning from the body, enter the heart?
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What is the correct order of the events in the cardiac cycle?
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Study Notes
The Cardiovascular System
- The heart is a dual pump with two atria and two ventricles, pumping blood from low-pressure veins to high-pressure arteries.
- The right ventricle pumps blood into the pulmonary artery, while the left ventricle pumps blood into the aorta.
- The output of the heart is controlled by intrinsic mechanisms and can be regulated by autonomic nerves and hormones.
- Blood pressure in the pulmonary circuit is approximately 28/8 mmHg, while in the systemic circuit it is approximately 120/80 mmHg.
Cardiac Cycle
- The cardiac cycle includes a complete relaxation and contraction of both atria and ventricles.
- The cycle consists of:
- Diastole (relaxation phase)
- Systole (contraction phase)
- Pressure changes occur within the heart during the cardiac cycle, directing blood flow through different chambers and the body.
- Valves within the heart regulate blood flow.
Electrical Activity of the Heart
- The heart has distinct electrical characteristics.
- Intercalated discs allow action potentials to pass to adjacent cells, allowing the heart muscle to function as a syncytium.
- Myocardial cells can spontaneously depolarize, generating a pacemaker potential.
Action Potential of the Heart
- Phases of the cardiac action potential:
- Rapid depolarization
- Early rapid repolarization
- Plateau phase
- Final rapid repolarization
- Ion channels regulate the movement of ions across the cell membrane, controlling the action potential.
Pacemaker Potentials
- Pacemaker potentials are generated by the sinoatrial (SA) node, which depolarizes over time, triggering an action potential.
- The SA node can be influenced by sympathetic and parasympathetic nerves to increase or decrease heart rate.
Excitation-Contraction Coupling
- Excitation-contraction coupling is the process by which an electrical action potential leads to contraction of cardiac muscle cells.
- Calcium is the crucial mediator that couples electrical excitation to physical contraction.
Electrocardiography (ECG)
- The ECG is an electrical trace resulting from action potentials in all heart muscle fibers.
- The ECG varies depending on the direction of travel, whether cells are depolarizing or repolarizing, and the size of the change in potential.
Events of the Cardiac Cycle
- The cardiac cycle can be divided into:
- P wave (atrial depolarization)
- QRS complex (ventricular depolarization)
- PR interval (atrial muscle depolarization to ventricular depolarization)
- PR segment (atrial muscle repolarization)
Cardiac Output
- Cardiac output is the product of stroke volume and heart rate.
- Regulation of stroke volume:
- Preload (extent of stretch of the heart muscle)
- Afterload (pressure against which the heart needs to pump)
- Contractility (ability of the muscle to produce a force)
- The Frank-Starling mechanism: an increase in blood returning to the heart increases end-diastolic volume, leading to increased stretching and increased force of contraction.
Neural Control of the Heart Rate
- Neural control of the heart is regulated by sympathetic and parasympathetic divisions of the autonomic nervous system.
- The autonomic nervous system regulates heart rate, conduction velocity, force of contraction, and coronary blood flow.
- Sympathetic and parasympathetic stimulation have opposite effects on the sinoatrial (SA) node action potential, influencing heart rate.
Chronotropic Effects
- Positive chronotropic effects: increases in heart rate, mediated by the sympathetic nervous system.
- Negative chronotropic effects: decreases in heart rate, mediated by the parasympathetic nervous system.### Neural Factors Affecting the Heart
- The sympathetic nervous system (SNS) increases heart rate and contractility
- The parasympathetic nervous system (PNS) decreases heart rate but has little effect on contractility
- Resting heart rate is approximately 70bpm, which is reduced from 100bpm by 'vagal tone'
Effects of Autonomic Nervous System on Pacemaker Cells
- Parasympathetic nervous system:
- Decreases rate of Na+ influx through funny channels
- Decreases Ca2+ influx
- Increases time taken for pacemaker potential to reach threshold for action potential
- Sympathetic nervous system:
- Increases rate of Na+ and Ca2+ influx
- Increases pacemaker potential development, leading to cardiac action potentials
Baroreceptors and Chemoreceptors
- Baroreceptors (carotid artery):
- Stimulated by increased blood pressure
- Decreases heart rate and stroke volume
- Increases parasympathetic activity and decreases sympathetic activity
- Chemoreceptors (carotid body):
- Stimulated by increased PCO2 and/or decreased PO2
- Increases heart rate and stroke volume
- Increases sympathetic activity and decreases parasympathetic activity
Systemic Hypertension
- Defined as the pressure of blood moving through the arterial system
- Blood pressure (BP) = cardiac output (CO) x systemic vascular resistance (SVR)
- Systolic BP is largely determined by characteristics of stroke volume (SV) being ejected by the heart and the ability of the aorta to stretch to accommodate SV
Elastic Tissue in Blood Vessels
- When blood is pushed into vessels, elastic tissue is stretched
- Elasticity 'absorbs' pressure, preventing a sharp rise in pressure
- Between heart beats, elastic tissue recoils, maintaining continuous blood flow
Regulation of Blood Pressure
- Regulated by autonomic and hormonal mechanisms
- Baroreceptor reflex:
- Primary mechanism for blood pressure regulation in acute settings
- Acts as a buffer for changes in posture and acute changes in blood volume
- Renin-angiotensin-aldosterone mechanism:
- Maintains long-term blood pressure
- Can reset or downregulate the baroreceptor reflex to a higher setpoint
Blood Pressure and Age
- Arterial pressure rises with advancing age
- Increased stiffness of large arteries due to arteriosclerotic lesions and calcification
- Decreased baroreceptor sensitivity
- Increased responsiveness to sympathetic nervous system activity
- Alteration in renin-angiotensin-aldosterone system relationships
Hypertension
- Age-related changes:
- Increased stiffness of large arteries
- Decreased baroreceptor sensitivity
- Increased responsiveness to sympathetic nervous system activity
- Primary hypertension:
- 95% of all cases
- Has no identifiable cause
- Secondary hypertension:
- 5-10% of all cases
- Has an identifiable cause (e.g. kidney disease, adrenal cortical disorders)
Effects of Hypertension on the Body
- Stroke due to brain hemorrhage
- Damage to capillaries in the eye, leading to eyesight damage
- Edema
- Left ventricular hypertrophy, leading to heart failure
- Damage to kidney blood vessels, leading to renal failure
- Injury to artery walls, precipitating atherosclerosis
Risk Factors for Hypertension
- Essential/primary hypertension:
- Excess salt consumption
- Overweight/obesity
- Alcohol consumption
- Inactivity
- Smoking
- Age
- Race
- Genetic factors
- Secondary hypertension:
- Renal disease
- Excess aldosterone
- Pheochromocytoma
- Other disorders
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Description
Learn about the structure and function of the heart, including its dual pump system, blood pressure, and circulation pathways. Understand how the heart pumps blood from low pressure veins to high pressure arteries and how output is controlled.