Chapter 19 Flashcards
What are the major divisions of the circulatory system?
Pulmonary circuit
Systemic Circuit
What is the pulmonary circuit?
The right side of the heart
Carries blood to lungs for gas exchange and back to heart
What is the systemic circuit?
Left side of the heart
Supplies oxygenated blood to all tissues of the body and returns it to the heart
Where is the heart located ?
In the mediastinum between the lungs
What is the base of the heart?
The wide superior portion of heart.
Large vessels attach here
Where is the apex of the heart?
tapered inferior end that tilts to the left
How big is your heart?
Size of your fist
What is the pericardium?
A double walled sac that encloses the heart
What are the functions of the pericardium?
Allows heart to beat without friction
Anchored to the diaphragm and sternum
What is the parietal pericardium?
Pericardial sac (outer layer of pericardium)
superficial fibrous layer of connective tissue
Deep thin serous layer
What is the visceral pericardium? (epicardium)
Inner layer of pericardium
serous membrane covering heart
what is the pericardial cavity?
Space inside the pericardial sac filled with pericardial fluid
What is pericarditis
Painful inflammation of the pericardial membranes
what are the layers of the heart wall?
Epicardium
Endocardium
Myocardium
What is the Epicardium (Visceral pericardium)?
Serous membrane covering the heart
What is the endocardium?
Smooth inner lining of heart and blood vessels
Covers valve surfaces and is continuous with endothelium of blood vessels
What is myocardium?
Layer of cardiac muscle proportional to work load
What is the fibrous skeleton of the heart?
framework of collagenous and elastic fibers
What is the function of the Right and left atria?
Receive blood returning to heart
what is the function of the right and left ventricle?
pump blood into arteries
What are auricles?
enlarge the chamber
What is the atrioventricular sulcus?
Separates the atria and ventricles
What is the interventricular sulcus?
Overlies the interventricular septum that divides the right ventricle from the left
What are sulci?
They contain coronary arteries
Interatrial septum
Wall that separates atria
Pectinate muscles
internal ridges of myocardium in right atrium and both auricles
Interventricular septum
muscular wall that separates ventricles
Trabeculae carnae
internal ridges in both ventricles
Function of trabeculae carneae
prevent ventricle walls from sticking together after contraction
Purpose of valves in heart
ensure one way flow of blood through heart
Atrioventricular valves (AV)
control flow of blood between atria and ventricles
Other name for right AV valve
Tricuspid valve
other name for left AV valve
Mitral valve/bicuspid
What are chordae tendinae?
chords that connect AV valves to papillary muscles on floor of ventricles
function of Semilunar valves
control flow in to great arteries
open and close because of blood flow and pressure
Where is the Pulmonary semilunar valve?
in opening between right ventricle and pulmonary trunk
Where is the Aortic semilunar valve?
In opening between left ventricle and aorta
What is the coronary circulation ?
The 5% of the Blood pumped to the heart itself to sustain itself
What is the left coronary article?
Branches off the ascending aorta
Anterior interventricular branch
supplies blood to both ventricles
Circumflex branch
passes around the left side of the heart
Right coronary artery
Also branches off ascending aorta
supplies right atrium and SA node (pacemaker)
What is a myocardial infarction?
Heart attack
due to interruption of blood supply to the heart
How can arterial anastomoses provide protection from MI?
Because it provides alternative routes for blood the heart
What is Atheroma?
blood clot or fatty deposit often obstructs coronary arteries
what is angina pectoris?
chest pain from partial obstruction of coronary heart flow
What are interdigitating folds?
folds that interlock with eachother and increase surface area.
What is cardiac muscle made up of?
Striated cardiocytes intercalated discs interdigitating folds mechanical junctions electrical junctions
What are mechanical junctions?
They tightly join cardiocytes with fascia adherens and desmosomes
What are electrical junctions?
gap junctions that allow ions to flow between cells and stimulate their neighbours
Cardiac muscle depends almost exclusively on which type of respiration to make ATP?
Aerobic
uses oxygen to burn sugars
Mitochondria of cardiac muscle take up what percentage of the cell?
25%
Cardiac muscle is fatigue resistant because….
it makes little use of anaerobic fermentation or oxygen debt mechanisms
What is the function of the conduction system?
It coordinates the heartbeat of the heart
What is the anatomy of the conduction system?
It is composed of an internal pacemaker and nerve like conduction pathways through myocardium
What effect does the sympathetic nerve system have on the heart?
Sympathetic nerves increase heart rate and contraction strength
What effect does parasympathetic nerve system have on the heart?
Parasympathetic nerves slow heart rate
What is the pathway of parasympathetic nerves to heart
begins with vagus nerves in medulla oblongata
What is systole
contraction (usually of ventricles)
What is diastole?
relaxation (usually of ventricles)
What is sinus rhythm?
normal heartbeat triggered by SA node.
What is normal resting heart rate?
70-80BPM
What is another name for resting heart rate?
Vagal tone
What is an ectopic focus?
A region of spontaneous firing other than the SA node
Can an ectopic focus take over heart rhythm?
it can do if SA node is damaged, but not for long.
What is nodal rhythm ?
If SA node is damaged, heart rate is set by AV node at 40-50 bpm
Does the SA node have a stable resting membrane potential?
No.
it starts at -60 and drifts upwards due to slow sodium influx
What is pacemaker potential ?
gradual depolarization of the membrane potential in SA node
What happens when SA node reaches threshold of -40mV?
voltage gated fast CA2+ and NA+ channels open
Depolarization occurs peaking at 0mV
What causes depolarization of SA node?
K+ channels open and k+ leaves the cell
What is the effect of SA node firing?
it sets off a heartbeat
What is pacemaker physiology?
Physiology of the SA node
What are the three phases of cardiocytes?
depolarization
plateau
repolarization
Do cardiocytes have a stable resting potential?
yes- it is -90mV
why is the refractory period for cardiocytes long and absolute?
prevents wave summation and tetanus which would stop pumping action of the heart
What is an ECG/EKG
Electrocardiogram
What does an Electrocardiogram measure?
composite action of all potentials of nodal and myocardial cells detected, amplified and recorded by electrodes on arms legs and chest
What does the P wave represent?
SA node fires
atria depolarize
Atrial systole
What does the QRS complex represent?
Ventricular depolarization
What does ST segment represent?
Ventricular systole
What does the T wave represent?
Ventricular repolarization and relaxation
What should the interval be between R and R on an EKG?
0.8 seconds
Deviations of EKG from normal can indicate?
Myocardia infarction
Abnormalities in conduction pathways
Heart enlargement
Electrolyte and hormone imbalance
What is ventricular fibrillation?
Serious arrythmia caused by electrical signals travelling randomly
What is defibrillation used for?
Its a strong electrical shock with intent to depolarize the entire myocardium and reset heart to sinus rhythm
What is the cardiac cycle
one complete contraction and relaxation of all four chambers of the heart
What are the two main principles that govern fluid movement?
Pressure causes flow
Resistance opposes it
Fluid will only flow if there is a…..
Pressure gradient
opening and closing of heart valves are governed by
pressure in the heart changes
What is valvular insufficiency?
any failure of a valve to prevent reflux
What is valvular stenosis?
cusps are stiffened and opening is constricted by scar tissue from rheumatic fever
What is a heart murmur?
abnormal heart sound produced by regurgitation of blood through incompetent valves
What is a mitral valve prolapse?
insufficiency in which one or both mitral valve cusps bulge into atria during ventricular contraction
What is auscultation
listening to sounds made by body
What is S1?
first heart sound
loud and long
lubb
occurs when AV valves close
What is S2?
Second heart sound
softer and sharper dupp
occurs with closure of semilunar valves
what is s3?
Third heart sound, rarely heard in people over 30
What are the four phases of the cardiac cycle?
Ventricular filling
isovolumetric contraction
ventricular ejection
isovolumetric relaxation
What is ventricular filling phase of cardiac cycle?
Ventricles expand and their pressure drops below that of atria
AV valves open and blood flows in
What is isovolumetric contraction phase of cardiac cycle?
Atria repolarize and remain in diastole for rest of cycle
S1 sound
Ventricles depolarize
AV valves close
What is ventricular ejection phase of cardiac cycle?
Ventricular pressure exceeds arterial pressure and Semilunar valves open
What is isovolumetric relaxation phase of cardiac cycle?
Ventricles begin to expand
semilunar valves close
heart sound s2 occurs
Normally right and left side of heart eject …….volume of blood
The same
Congestive heart failure is
result of failure of either ventricle to eject blood effectively
Left ventricular failure
blood backs up in to the lungs causing pulmonary edema
Right ventricular failure
Blood backs up in the Vena Cava and causes systemic or generalized edema
Failure of either ventricle eventually leads to
total heart failure
What is cardiac output (CO)?
amount ejected by each ventricle in 1 minute
Formula for cardiac output
heart rate x stroke volume
cardiac reserve
difference between maximum and resting CO
what is tachycardia?
resting adult heart rate over 100 bpm
what is bradycardia?
resting adult heart rate of less than 60 bpm
What is pulse?
surge of pressure produced by heart beat that can be felt by palpating a superficial artery
ANS does not initiate heartbeat it….
modulates rhythm and force
What are positive chronotropic agents?
factors that raise the heart rate
What are negative chronotropic agents/
factors that lower the heart rate
Medulla oblongata initiates …..
autonomic output of the heart
Medulla receives input from
proprioceptors in muscles and joints
3 variables that govern stroke volume
preload
contractility
afterload
increased preload or contractility
increases stroke volume
increased afterload
decreases stroke volume
what is preload
Amount of tension in ventricular myocardium immediately before it begins to contract
Frank starling law of heart
SV is proportional to end diastolic volume
What is hyperkalemia?
excess in K+
heart rate slows and becomes irregular
What is hypokalemia
deficiency in K+
cells hyperpolarized and require increased stimulation
What is Hypercalcemia?
excess of calcium decreases heart rate and contraction strength
What is hypocalcemia?
deficiency of calcium increases heart rate and contraction strength
What is contractility?
refers to how hard the myocardium contracts for a given preload
What is afterload?
sum of all forces opposing ejection of blood ventricle
