Chapter 19 Flashcards
wWhat is cardiology?
The study of the heart and treatment of its disorders
Divisions of the cardiovascular system?
Pulmonary circuit and systemic circuit
What is the pulmonary circuit?
Brings blood to the lungs
What is the systemic circuit?
Brings blood to every organ of the body
What does the left half of the heart do?
Supplies the systemic circuit, deals with oxygenated blood
What does the right half of the brain do?
Supplies the pulmonary circuit, deals with deoxygenated blood
Where do veins carry blood?
To the heart
Where do arteries carry blood?
Away from the heart
Flow of deoxygenated blood?
Through vena cavae into right atrium -> tricuspid valve -> right ventricle -> pulmonary valve -> pulmonary trunk -> right and left pulmonary arteries -> lungs (drops off CO2, picks up O2)
Flow of oxygenated blood?
Right and left pulmonary veins to left atrium -> bicuspid (mitral) valve -> left ventricle -> aortic valve -> ascending aorta, aortic arch, descending aorta -> out to body via systemic circuit
Where is the heart?
In the mediastinum, between the 2 lungs
What is the base of the heart?
The wide upper part where great vessels are attached
What is the apex of the heart?
The inferior pointed part tilting left
How much does the heart weigh?
About 300g in adults
What encloses the heart?
Pericardium
Layers of the parietal pericardium / pericardial sac?
(Superficial) fibrous layer and (deep) serous layer
What lies between the parietal and visceral membranes?
The pericardial cavity
What is in the pericardial cavity?
5-30 mL of pericardial fluid
What does pericardial fluid do?
Lubricate the heart so there’s no friction
What is pericarditis?
Inflammation of the pericardium
Simple function of the right atrium?
Receive blood from systemic circuit
Simple function of the right ventricle?
Pump blood into pulmonary circuit
Simple function of the left atrium?
Receive blood from the pulmonary circuit
Simple function of left ventricle?
Pump blood into systemic circuit
What do atria do?
Receive blood
What do ventricles do?
Pump blood
What are the layers surrounding the heart?
From outermost to innermost, pericardial sac, parietal pericardium, pericardial cavity, epicardium, myocardium, endocardium
Layers of heart wall, from outermost to innermost?
Epicardium, myocardium, endocardium
What are the atrioventricular valves?
Tricuspid and mitral (bicuspid) valves
What are the semilunar valves?
Pulmonary and aortic valves
What do the atrioventricular valves do?
Permit blood flow in one direction
What do the semilunar valves do?
Prevent backflow of blood into ventricles
Divisions of valves?
Atrioventricular and semilunar
What is auscultation?
Listening to the sounds the body makes
What is the first heart sound?
S1, the “lubb” or louder and longer-lasting sound. Signifies closing of AV valves
What happens during the S1 sound?
Atrioventricular valves close
What is the second heart sound?
S2, or “dupp”, the softer and sharper sound that signifies the closure of the semilunar valves
What happens during the S2 sound?
Semilunar valves close
What is valvular insufficiency?
Incompetence, or failure of the valve to prevent backward flow of blood (reflux)
Types of valvular insufficiency?
Valvular stenosis and mitral valve prolapse
What is valvular stenosis?
When the cusps are stiffened and the opening is constricted due to scar tissue. Increases afterload and heart overworks
Causes of valvular stenosis?
Rheumatic fever, calcification, or autoimmune attack on mitral and aortic valves
What is mitral valve prolapse?
A form of valvular insufficiency, in which one or both mitral valves bulge into the atria during ventricular contraction. May cause chest pain and shortness of breath
What is a heart murmur?
An abnormal sound due to blood rushing backwards during contraction
What are cardiac sulci?
Superficial groups which mark the boundaries of the 4 chambers. They follow where the sinuses are internally, externally
What is the coronary sulcus?
A sulcus separating the atria from the ventricles
What are the cardiac sulci?
Coronary sulcus, anterior interventricular sulcus, and posterior interventricular sulcus
What does the right coronary artery supply?
The right atrium and the sinoatrial node (pacemaker)
What are the branches of the right coronary artery?
The right marginal branch and the posterior interventricular branch
What does the right marginal branch of the RCA supply?
The lateral aspect of the right atrium and ventricle
What does the posterior interventricular branch of the RCA supply?
Posterior walls of both ventricles
What branches off of the left coronary artery?
The anterior interventricular branch and the circumflex branch
What does the anterior interventricular branch of the LCA supply?
Both ventricles and the anterior 2/3rds of the interventricular septum
What does the circumflex branch of the LCA supply?
The left atrium and posterior wall of the left ventricle
What is the coronary circulation?
When 5% of blood being pumped is routed throughout the heart, in order to supply it with nutrients and oxygen for its workload
What method does cardiac muscle use to make ATP?
Aerobic respiration
Benefits and downsides of cardiac muscle using aerobic respiration?
It doesn’t fatigue over a whole lifetime (unless something is wrong), but lack of oxygen means heart attack
What is coronary artery disease?
A constriction of the coronary arteries in which lipids degrade the arterial wall and form obstructions
What is angina pectoris?
Chest pain caused by partial obstruction of coronary blood flow
What causes coronary artery disease?
An endothelium gets damaged by hypertension, diabetes, or other causes
Avoidable risk factors of coronary artery disease?
Obesity, smoking, lack of exercise, anxious personality, stress, and diet
Unavoidable risk factors for coronary artery disease?
Genetics, aging, and being male
What is the coronary sinus?
A coronary vein which collects blood and empties into the right atrium
What is the great cardiac vein?
A coronary vein which collects blood from the anterior portion of the heart and empties into the coronary sinus
What is the middle cardiac vein?
A coronary vein which collects blood from the posterior portion of the heart and empties into the coronary sinus
What is the left marginal vein?
A coronary vein which empties into the coronary sinus
What is cardiac muscle tissue made of?
Cardiomyocytes
Structure of cardiomyocytes?
Striated, short, and thick. Branched, and joined at the ends by intercalated discs
Purpose of intercalated discs?
Allows the entire myocardium of either atria or ventricles to act like a single unified cell
How do cardiomyocytes join?
By mechanical junctions (desmosomes) and electrical junctions (gap junctions)
Purpose of mechanical junctions (desmosomes)?
Prevents contracting cardiomyocytes from being pulled apart from each other
Purpose of electrical junctions (gap junctions)?
Allows ions to flow between cells, so cells can stimulate their neighbors
In systemic circuit, blood leaves which chamber?
Left ventricle
In systemic circuit, blood enters which chamber?
Right atrium
In pulmonary circuit, blood exits which chamber?
Right ventricle
In pulmonary circuit, blood enters which chamber?
Left atrium
In systemic circuit, what artery leaves heart and is it oxygenated?
Aorta, oxygenated
In pulmonary circuit, what artery leaves heart and is it oxygenated?
Pulmonary arteries (left and right), deoxygenated
In systemic circuit, what vein leads to heart and is it oxygenated?
Inferior and superior vena cavae, deoxygenated
In pulmonary circuit, what vein leads to heart and is it oxygenated?
Pulmonary veins, oxygenated
What does autorhythmic mean?
The heart doesn’t depend on the nervous system for its rhythm. It has its own built-in pacemaker and electrical system
What are cardiomyocytes?
The muscle cells of the heart, which are branched, allowing cardiomyocytes to contact others around it
Distinctive features of intercalated discs?
Interdigitating folds, mechanical junctions, electrical junctions
What are interdigitating folds?
When folds of adjoining cells interlock with each other to increase the surface area of intercellular contact
What are mechanical junctions?
Fascia adherens and desmosomes. Desmosomes prevent contracting cardiomyocytes from pulling apart from each other
What are electrical junctions?
Gap junctions that allow ions to flow from the cytoplasm of one cardiomyocyte to the next. Enabling each cardiomyocyte to electrically stimulate its neighbors and act as one
Can cardiac muscle replace itself?
No, it repairs by fibrosis and scar tissue
How does cardiac muscle make ATP?
Aerobic respiration
Benefits and drawbacks of the heart using aerobic respiration?
It’s highly resistant to fatigue, but lack of oxygen has detrimental effects
What makes up the cardiac conduction system?
Internal pacemaker cells and nervelike conduction pathways
Steps of conduction system?
SA node fires, excitation spreads through atrial myocardium, AV node fires, excitation spreads down AV bundle, Purkinje fibers distribute excitation through ventricular myocardium
Does the nervous system have any effect on the cardiovascular system?
Yes, it can influence the heart rate and force of contraction. And there are fibers for cardiovascular reflexes and transmission of pain signals to the heart
What contracts first in a heartbeat?
Atria, then ventricles
2 types of cardiac muscle cells?
Autorhythmic and contractile cells
What do autorhythmic cells do?
Control and coordinate the heartbeat
What do contractile cells do?
Produce contractions that propel blood
What is the conducting system?
Specialized cardiomyocytes that initiate and distribute electrical impulses to stimulate contraction
Components of the conducting system?
Pacemaker cells and conducting cells
Where are pacemaker cells?
In the SA node and the Av node
Where are conducting cells?
In internodal pathways of atria and AV bundle, bundle branches, and Purkinje fibers of ventricles
Steps of impulse conduction through the heart?
SA node and atrial activation -> stimulus spreads across atria and reaches AV node -> impulse is slightly delayed, atrial contraction starts ->impulse travels in Av bundle and reaches Purkinje fibers -> they distribute impulse to ventricular myocardium, ending atrial contraction and starting ventricular contraction
What is bradycardia?
Abnormally slow heart rate
What is tachycardia?
Abnormally fast heart rate
What is an ECG?
A recording of electrical events in the heart that can diagnose damage
What are cardiac contractile cells?
They form the bulk of atrial and ventricular walls, and receive stimulus from Purkinje fibers
What are intercalated discs?
They interconnect cardiac contractile cells, holding cells together by desmosomes and linked by gap junctions. They transfer force of contraction from cell to cell and propagate action potentials
Steps of action potential in cardiac contractile cells?
Rapid depolarization, plateau, and repolarization
What happens during rapid depolarization?
Massive influx of sodium ions from fast sodium channels. Raise RMP to positive
What happens during plateau?
Extracellular calcium ions enter cytosol through slow calcium channels
What happens during repolarization?
Potassium ions rush out of the cell through slow potassium channels, RMP returns to -90mV
How long does an action potential in ventricular contractile cells take?
250-300 milliseconds, 30x longer than in skeletal muscle fibers
What is the cardiac cycle?
The start of one heartbeat to the start of the next. Includes alternating periods of contraction and relaxation. One complete systole and diastole of all 4 chambers
What is systole?
Contraction
What is diastole
Relaxation
Formula for cardiac output?
CO = heart rate x stroke volume
What is cardiac reserve?
The difference between resting and maximum cardiac outputs
What is the atrioventricular node?
The electrical gateway to the ventricles. Has the fibrous skeleton, an insulator that stops currents from getting to ventricles by any other route
What is the atrioventricular bundle / bundle of His?
It forks into the right and left bundle branches, which pass through the septum toward the apex
What are Purkinje fibers?
They spread signal upward throughout ventricular myocardium and distribute electrical excitation to the cardiomyocytes of the ventricles
What happens after Purkinje fibers deliver the signals?
The cardiomyocytes perpetuate it by passing ions from cell to cell via gap junctions
Conduction system pathway?
SA node -> AV node -> AV bundle -> right and left bundle branches -> Purkinje fibers -> cardiomyocytes of the ventricles
What is the P wave?
SA node fires, atria depolarization and contraction. Systole begins 100ms after SA signal
What is the QRS complex?
Ventricular depolarization
What is the ST segment?
Ventricular repolarization, which corresponds to the plateau in myocardial action potential
What is the T wave?
Ventricular repolarization and relaxation
Ways of cardiac rhythm
Sinus rhythm and ectopic focus
What is sinus rhythm?
A normal heartbeat triggered by the SA node, typically 70-80 bpm in adults at rest
What is ectopic focus?
A region of spontaneous firing other than the SA node. Can govern heart rhythm if SA node is damaged
What is nodal rhythm?
Heart rate of 40-50 bpm when SA node is damaged. Set by AV node
What is an arrythmia?
Any deviation from the regular sinus rhythm
What can deviations of ECG indicate?
Myocardial infarction, abnormalities in conduction pathways, heart enlargement, and electrolyte and hormone imbalances
What is ventricular fibrillation?
A serious arrhythmia caused by electrical signals traveling randomly
What is defibrillation?
A strong electrical shock, with the intent to depolarize the myocardium and reset the heart to sinus rhythm
What variables govern fluid movement?
Pressure causes flow, resistance opposes it. Fluid flows following a pressure gradient
What is Wigger’s diagram?
A diagram measuring cardiac cycles. it shows that pressure and volume are inversely related
What happens when the ventricles relax?
Pressure drops in the ventricles, semilunar valves close, AV valves open, and blood flows from atria to ventricles
What happens when ventricles contract?
AV valves close, pressure rises in ventricles, semilunar valves open and blood flows into great vessels
Phases of cardiac cycle?
Ventricular filing (diastole), isovolumetric contraction (systole), ventricular ejection (systole), isovolumetric relaxation (diastole)
What is ventricular filling?
Atria contract, 130mL of blood in each ventricle
What is ventricular ejection?
Blood is ejected, leaving 60mL in each ventricle
What variables govern stroke volume?
Preload, contractility, and afterload
What is pulse?
The surge of pressure produced by heart beat that can be felt by palpating a superficial artery. 120bpm in infants and 60-100bpm in adults
What are positive and negative chronotropic agents?
Positive are factors that raise heart rate, negative are factors that lower heart rate
What does the ANS do?
Modulate rhythm and force of the heartbeat. Cardiac centers in the medulla oblongata initiate the autonomic output to the heart
What is the cardiostimulatory effect?
Some neurons of cardiac center transmit signals to heart via sympathetic pathways. Symp fibers release norepinephrine, binds to fibers in the heart to speed it up and increase force of contractions
What is the cardioinhibitory effect?
Some neurons of cardiac center transmit parasympathetic signals via vagus nerve. Slows down heart
What happens to heart rate if symp and parasymp stimulation is blocked, or cardiac nerves are severed?
Heart beats at about 100bpm which is the intrinsic rate of the SA node
What happens if the innervation of the heart is intact?
it beats at 70-80 bpm by vagal tone, background firing rate of vagus nerves
What is blood pressure’s formula?
Cardiac output x systemic vascular resistance
What is preload?
The amount of tension in ventricular myocardium right before it begins to contract. Increased preload = increased force of contraction
What is contractility?
How hard the myocardium contracts for a given preload
What are positive inotropic agents?
They increase the heart’s contractility and include calcium, catecholamines, glucagon, and digitalis
What are negative inotropic agents?
They decrease the heart’s contractility and include hypocalcelmia and hyperkalemia
What is afterload?
The sum of all forces opposing ejection of blood from ventricles
What is cor pulmonale?
Right ventricular failure due to pulmonary vasoconstriction
What can restrict pulmonary circulation?
Lung diseases like COPD
How are volume and pressure in the chambers connected?
Inversely, when volume increases, pressure decreases and vice versa
Stages of diastole?
Rapid filling, diastasis, atrial systole, isovolumetric relaxation
Stages of systole?
Isovolumetric contraction, ventricular ejection
What does myogenic mean?
The impulse for contraction originates in the heart itself
What increases stroke volume?
Higher preload and contractility
What lowers stroke volume?
Higher afterload
