The Heart Flashcards
What are the major divisions of the heart?
Pulmonary circuit
Systemic circuit
The pulmonary circuit carries blood to the ________ for gas exchange and returns it to the ________
Lungs
Heart
Blood travels from the _____ side of heart to _______ ________ to pulmonary ________ to _______ to _______ veins to heart.
Right
Pulmonary trunk
Pulmonary arteries
Lungs
Pulmonary veins
What is the function of the systemic circuit?
Supplies blood to every organ of the body
Path of the systemic circuit: ______ side of the heart to_______ to _________ arteries to tissues of body to ______ _______ to heart
Left
Aorta
Systemic
Vena Cava
Where is the heart located?
Lies in the thoracic cavity within the mediastinum
What is the apex of the heart?
The apex is the “unstable” part of the heart that rests on the diaphragm, below the base
What is the mediastinum?
This is the center of the chest
Describe the base of the heart.
The base of the heart is laterally, inclined to the right
It is the broader section of the heart
Describe the position of the heart.
The base points towards the right shoulder
More than half of the heart is to the left of the median plane
Describe the size and shape of the heart
The heart is approximately the size of a fist
The heart what is about 300 g in adults
What is the pericardium?
This is a membrane that surrounds the heart
What are the two types of pericardium?
Fibrous pericardium
Serous pericardium
What are the two divisions of the serous pericardium?
Parietal layer
Visceral layer
What is another name for the visceral layer of the serous pericardium?
The epicardium
What are the three layers of the heart wall?
Epicardium
Myocardium
Endocardium
What is the epicardium?
The outermost layer of the heart wall
Describe the epicardial membrane
It is a serous membrane
Consist of a simple squamous epithelium over lying thin loose connective tissue
What is the myocardium?
This is the middle layer of the heart wall
Describe the myocardial membrane
It is the primary cardiac muscle
It is the thickest layer of the heart wall
It performs the work of the heart
What is the endocardium?
This is the inner layer of the heart wall
Describe the endocardial membrane
lines the heart chambers
folds to create heart valves
Continuous with blood vessel endothelium
How many chambers does the heart have? Name them.
Four Chambers:
Two superior atria
Two inferior ventricles
What is the function of the heart valves?
They ensure blood flows, one way in the heart
Name the two classification of the heart valves
Atrioventricular valves
Semilunar valves
Name the two types of atrioventricular valves
Tricuspid valve or right atrioventricular valve
Mitral valve or left atrioventricular valve
What is the function of the tendinous cords?
The connect the AV valves to the papillary muscle
What is the function of the papillary muscle?
The tense when the miocardia contracts and prevent prolapsing of the AV valves
Describe the flow of blood through the chambers of the heart
Right atrium from superior and inferior vena cava
From right atrium to AV valve to right ventricle
Contraction of right ventricle opens pulmonary valve
Blood flows through pulmonary valve into pulmonary trunk
Blood distributed by right and left pulmonary arteries to lungs , unloads CO2 and Loads O2.
From lungs via pulmonary vein to left atrium
From left atrium through left AV valve to left ventricle
Contraction of left ventricle (happens with step 3) opens aortic valve
Blood flows through aortic valve into ascending aorta
Blood in aorta distributed to every organ in the body
Blood returns to right atrium via vena cava
What is coronary circulation?
This refers to the blood vessels of the heart wall that provide the heart with nutrients
What are the main vessels of the heart wall?
Left coronary artery
Right coronary artery
Cardiac veins
Describe coronary circulation
Left ventricle
aorta
coronary arteries
coronary capillaries
coronary veins
coronary sinus
right atrium
Describe the cardiac muscle structure
Consist of cardio myocytes
striated muscle tissue
Inter-calated discs
Describe cardio myocytes
muscle cells of the heart
Single centrally placed nucleus, some more
Sarco plasmic reticulum is less developed than in skeletal muscle, no terminal cisterns
Larger T tubules than in skeletal muscle, they admit calcium ions from EC fluid to activate contraction
Joined by intercalated discs
99% contractile cells
1% autorhythmic cells
What does the term myogenic mean in terms of the heartbeat?
The signal originates in the heart itself
What is the heart described as auto rhythmic?
It doesn’t depend on the nervous system for it’s rhythm
How does the heart generate its own rhythm?
It has its own built-in pacemaker, and electrical system
What are the intercalated discs in cardio myocytes?
These are thick connections that join cardio myocytes to each other.
They have a complex step like structure with three distinct features, not found in skeletal muscles
What are the three distinct features of inter-calated discs?
Interdigitating folds
Mechanical junctions
Electrical junctions
What is one major difference between skeletal muscle and cardiac muscle, in terms of healing?
Skeletal muscle contain satellite cells that divide and replace that muscle fibers to an extent these are not found in cardiac muscle
Cardiac muscle has a limited capacity for mitosis and regeneration
Heals mainly by scarring (fibrosis)
Cardiac muscle depends on what type of respiration to make ATP?
Aerobic respiration
Very vulnerable to oxygen deficiency
Does not make use of oxygen debt mechanism or anaerobic fermentation, so not prone to fatigue
What is the function of the cardiac conduction system?
This coordinates the heartbeat
What is a cardiac conduction system composed of?
Internal pacemaker (SA node)
Nerve like conduction pathways through the myocardium
What is the SA node?
Sinuatrial node is a patch of modified cardio myocytes in the right atrium
What is the location of the SA node?
Located in the right atrium under the epicardium near the superior vena cava
Describe how the cardiac conduction system works.
SA node fires
Excitation spreads through atrial myocardium
AV node fires
Excitation spreads down AV bundle
Subendocardial conducting network distributes excitation through ventricular myocardium
Describe the fibers that carry the electrical signals that activate excitation in the myocardium
SA node
AV node
Atrioventricular bundle
Right and left bundle branches
Subendocardial conducting network
What is an ECG?
This is a recording of electrical changes in the myocardium during a cardiac cycle
What are the principal deflections of an ECG reading?
P-wave
QRS complex
T-wave
What happens in the P-wave of the cardiac cycle?
Atrial depolarization- this causes contraction
What happens in the QRS complex of the cardiac cycle,?
Ventricular depolarization- ventricle contracts at Q and raises to R, completes when falls to S.
Depolarization causes________, repolarization causes_________
Contraction
Relaxation
What happens at the T-wave in the cardiac cycle?
Ventricular repolarization begins at the lowest point of T, rises, completes when it falls.
Heart is ready for another cycle
What is an arrhythmia?
Irregular heartbeat
What is ventricular fibrillation?
The electrical signals in the heart are off, and the ventricle quiver is instead of contracting enough to pump blood to the body
What is a heart block?
This is a failure of any part of the cardiac conduction system
What is defibrillation?
Emergency, shocking of the heart with paddle electrodes to depolarize the entire myocardium and stop fibrillation
This usually causes the SA node to resume sinus rhythm
What unit is pressure measured in?
Measured in millimeters of mercury: mm Hg
Mercury is used because of its density, doesn’t have to be pushed as far up as water to be measured
What is used to measure blood pressure?
A sphygmomanometer
What is a pressure gradient?
Fluid flowing because there is more pressure at one point and the other
What causes the heart valves to open and close?
Changes in blood pressure in the heart
What happens when the ventricles relax and their pressure is low
The valves stay open, and the cusps hang down limply
What causes the first heart sound?
Shutting of AV valve
Blood pushes against the AV valve
What causes a second heart sound?
Shutting off semilunar valve
Blood pushing against the semi lunar valves
What is the cardiac cycle?
Complete contraction and relaxation of all 4 chambers
Name the phases of the cardiac cycle
Ventricular filling
Isovolumetric contraction
Ventricular ejection
Isovolumetric relaxation
What happens in isovolumetric contraction?
Pressure in the ventricles, rises sharply, and reverses the pressure gradient between the atria and the ventricles
Heart sound 1 is produced by blood beating against EV valve
Why is the contraction at phase two referred to as isovolumetric?
Ventricles contract but do not eject any blood yet, and there is no change in their volume
What happens at ventricular ejection?
Blood passes through semilunar valves and is ejected
What is stroke volume?
The amount of blood ejected from the heart
What is the measurement of stroke volume?
About 70 ml
________-________= ESV
EDV- SV equals ESV
Systole is___________
Contraction
Diastole is
Relaxation
Diastasis is_________
Slow filling off the ventricle
Ventricular filling occurs in how many phases. Name them
Three
Rapid filling
Slow filling (diastasis)
Atrial systole
What is in diastolic volume?
The amount of blood that fills the heart at ventricular filling
What is the measure of end diastolic volume?
130 mL
Left ventricular pressure, of 120mm Hg, overcomes which arterial pressure
Aortic pressure off 80 mm Hg
Right ventricular pressure of 25 mm Hg, overcomes which arterial pressure?
Pulmonary trunk pressure of 10 mm Hg
What is the amount of pressure needed in the left ventricle higher than the right ventricle
The left ventricle is pumping blood to the entire body, while the right ventricle is pumping blood to the lungs.
left ventricle has a longer distance to push the blood to needs higher pressure
Depolarization, systole is_________
Contraction
Repolarization, diastole is_________
Relaxation
End systolic volume is the difference between
End diastolic volume and stroke volume
Semi lunar valves close to prevent backflow
Heart sound two occurs
Isovolumetric relaxation
Ventricles contract, but do not eject blood
No change in volume
Heart sound 1 is heard
Pressure in aorta and pulmonary trunk peaks to prepare for stroke volume
Isovolumetric contraction
What is the cardiac cycle?
Each time the heart contracts and relaxes to admit, and eject blood
What is the cardiac output?
amount of blood pumped out of each ventricle in one minute
Cardio put is a product of _______ times ______
Heart rate x stroke volume
What is heart rate?
Heartbeats per minute
How many factors regulate stroke volume? Name them.
Three factors:
Preload
Contractility
Afterload
What is the preload phase of stroke volume?
The degree of stretch before contraction
Directly proportional to stroke volume (Frank- Starling law)
What is contractility in terms of stroke volume?
Forcefulness of the contraction
What is afterload in terms of stroke volume?
Sum of forces, ventricle must overcome before ejection
LVP -120 mm Hg
RVP -25 mm Hg
Name the two main mechanisms that regulate heart rate
ANS
Hormone activity
Factors that affect CO in terms of a reduced heart rate
Called negative Chrono tropic agents:
Parasympathetic nervous system
Acetylcholine
Hypercalcemia
Hypokalemia
Beta blockers
What does that affect CO in terms of a reduced stroke volume
Reduced preload
reduced contractility
increased afterload
negative inotropic agents:
Hypocalcemia
Hyperkalemia
Factors affecting CO, in terms of increased heart rate
Positive Chronotropic agents:
Sympathetic nervous system
Epinephrine, norepinephrine
Thyroid hormone
Glucagon
Nicotine, caffeine
Hypocalcemia
Factors affecting CO, in terms of increased stroke volume
Increased preload (myocardial stretch)
Positive inotropic agents:
Sympathetic nervous system
Epinephrine, norepinephrine
Glucagon
Digitalis
Nicotine, caffeine
Hypercalcemia
What causes cardiac disease?
Obstruction of coronary blood flow
Insufficiency of ventricular pumping
Name two types of cardiac diseases
Angina pectoris (chest pain)
Myocardial infarction (heart attack)
What happens in a pulmonary edema?
RV output exceeds LV output
Pressure backs up
Fluid accumulates in pulmonary tissue
What happens in a systemic edema?
LV output exceeds RV output
Pressure backs up
Fluid accumulates in systemic tissue
What in the wrong s artherosclerosis?
A buildup of plaque in the arteries which prevents proper blood flow
