Chapter 17- The Cardiovascular System Flashcards
What does the cardiovascular system consist of?
The heart
Blood vessels
Blood
The heart pumps blood into the blood vessels
What is the apex of the heart?
Bottom cone-shape part of the heart that points toward the left hip
What is the base of the heart?
The flattened, posterior side of the heart. All of the major vessels of the heart exit from here
What are the four chambers of the heart?
Right and left atrium
Right and left ventricle
Veins
Vessels which bring blood back to the heart
Arteries
Cells which carry blood from the ventricles away from the heart
Why is the right side of the heart sometimes called the pulmonary pump?
Because it pumps blood through the pulmonary arteries out to the pulmonary capillaries in the lungs
Where does gas exchange take place in the lungs?
Alveoli and pulmonary capillaries
Why is the left side of the heart often called the systemic pump?
It pumps oxygenated blood throughout the rest of the trunk and extremities
Which circuit in the heart operates at lower pressure? Why?
Pulmonary
Only has to pump to the lungs
Which circuit in the heart operates at higher pressure? Why?
Systemic
Has to pump blood to the entire body
What hormone is produced by the heart? How does it lower BP?
Atrial natriuretic peptide
Lowers the amount of sodium in the kidneys to less water is retained
Electrolyte homeostasis
What is the pericardium?
Membranous structure surrounding the heart composed of the : fibrous (thicker) and serous (thinner) pericardium
Visceral pericardium
Aka epicardium
Most superficial layer of the heart wall
Myocardium
Deep to the visceral pericardium
2 components: cardiac muscle tissue and the fibrous skeleton made of dense irregular collagen
Functions of fibrous skeleton
Gives the cardiac muscle cells something to hold on to
Provide structural support
Acts as an insulator for the hearts electrical activity
Endocardium
Deepest layer of the heart wall, lines the lumen of the heart
Composed of endothelium
What are the great vessels?
Superior/inferior vena cava
Pulmonary trunk
Aorta
Two veins that drain most of the systemic circuit into the right atrium
Superior/inferior vena cava
Pulmonary trunk
Receives deoxygenated blood from the right ventricle
Splits into the right/left pulmonary arteries
Pulmonary veins
2 from each lung
Drain oxygenated blood into the left atrium
Aorta
Supplies the entire systemic circuit with oxygenated blood
Receives blood ejected by the left ventricle
What is the function of the auricles?
They expand to give the atria more room to hold blood
What separates the two atria?
Interatrial septum
What is the fossa ovalis?
An indentation in the interatrial septum that used to be the foremen ovale
What is the foramen ovale?
Hole in the interatrial septum in fetal hearts to allow blood to bypass the lungs
What do we call the ridged surface created by irregular cardiac muscle inside the ventricles?
Trebeculae carnea
Papillary muscles
Finger-like projections of muscle in the ventricles that attach by the chordae tendineae to the valves between the atria and ventricles
What separates the right and left ventricles?
Interventricular septum
Atrioventricular valves aka AV valves
Prevent backflow of blood from the ventricles to the atria
The two valves consist of cusps. Each valve named for how many cusps it has : bicuspid and tricuspid
Valve located between the right atrium and right ventricle
Tricuspid valve
Valve located between the left atrium and left ventricle
Bicuspid
Semilunar valves
Prevent blood from flowing back into the ventricles
They are named for the artery in which they reside: pulmonary valve, aortic valve
Coronary circulation
Necessary because the walls of the heart are too thick for oxygen and nutrients to diffuse from inside the chambers.
So the heart has its own set of coronary arteries to supply it with the nutrients it needs
Two branches that arise from the ascending aorta
Right and left coronary arteries
Left coronary splits and becomes the anterior interventricular artery and the circumflex
Coronary sinus
Most of the hearts veins empty into the skin which drains to the right atrium
Receives blood from 3 major veins: great cardiac, small cardiac, middle cardiac
Pacemaker cells
Cardiac muscle cells that rhythmically and spontaneously generate action potentials that trigger contractile cells
Reside in the atria
Autorhythmicity
When cells set their own rhythm without a need for input from the nervous system
Cardiac conduction system
Three populations of cells in the heart capable of spontaneously generating action potentials and setting the pace of the heart
SA node
AV node
Purkinje fibers
Phases of a pacemaker action potential
- slow initial depolarization phase
- full depolarization phase
- repolarization phase
- minimum potential phase
Pacemaker slow initial depolarization phase
Membrane is hyperpolarized allowing sodium in and potassium out resulting in slow depolarization
Pacemaker full depolarization phase
Calcium ion channels open and calcium rushes in resulting in a rapid and complete depolarization
Pacemaker repolarization phase
Calcium channels begin to close and potassium channels begin to open causing the cell to repolarize
Pacemaker minimum potential phase
Potassium channels stay open until the membrane reaches its minimum potential. The membrane will then be hyperpolarized and the cycle begins again
Phases of contractile cell action potentials
- rapid depolarization phase
- initial repolarization phase
- plateau phase
- repolarization phase
Contractile cell rapid depolarization phase
Sodium channels open and sodium rushes in rapidly depolarizing the membrane
Contractile cell initial repolarization phase
Sodium channels shut down, some potassium channels open and some potassium leaks out causing slight repolarization
Contractile cell plateau phase
Calcium channels open and calcium enters as potassium exits simultaneously causing a plateau and prolonging depolarization
Contractile cell repolarization phase
Sodium and calcium channels close and potassium continues to exit the cell causing repolarization
Where is the Sinoatrial node(SA) and what does it do?
Upper right atrium. Causes the atria to contract
Where is the Atrioventricular node (AV) and what does it do?
Located behind the tricuspid valve it is slower than the SA node and causes the ventricles to contract
Purkinje fiber system
Slowest group of pacemaker cells
Composed of AV bundle, right/left bundle branches, terminal branches
Sinus rhythms
Electrical rhythms generated and maintained by the SA node
What is AV node delay?
Slow conduction of impulses as a result of a low number of gap junctions between cells and the presence of the non-conducting fibrous skeleton
What does an electrocardiogram measure?
Electrical activity occurring in all cardiac muscle cells over a period of time
Shown as waves: P wave, QES complex, T wave
Periods between waves represent phases of action potentials and denoted as intervals: R-R, P-R, Q-T. One segment to note: S-T
P wave
Atrial depolarization
QRS complex
Ventricular depolarization
T wave
Ventricular repolarization
R-R interval
Entire duration of a cardiac action potential
Q-T interval
Entire duration of a ventricular action potential
S-T segment
Ventricular plateau phase
P-R interval
Duration of atrial depolarization and AV node delay
Events in cardiac cycle
Ventricular filling phase
Isovolumetric contraction phase
Ventricular ejection phase
Isovolumetric relaxation phase
Ventricular filling phase
When blood drains from the atria into the ventricles.
Semilunar valves are closed preventing backflow from pulmonary trunk and aorta.
AV valves are open due to high atrial pressure pushing blood down its pressure gradient.
80% of blood drains passively from atria to ventricles while in diastole but then the final 20% gets ejected to ventricles during atrial systole
End Diastolic Volume (EDV)
Ventricular volume at the end of ventricular diastole (once atria have empties into ventricles)
Increases when the ventricles spend more time in diastole
Isovolumetric contraction phase
Ventricular systole occurs. High pressure closes the AV valves but pressure not high enough to open semilunar valves yet
Ventricular ejection phase
Pressure in the ventricles becomes higher than that in the pulmonary trunk and aorta and pushes semilunar valves open
Ejection of blood starts rapidly but then decreases until only 70ml of blood have been pumped, leaving 50ml remaining
End systolic volume (ESV)
Blood left in ventricles after ejection, about 50ml
Isovolumetric relaxation phase
Occurs as ventricular diastole begins and pressure drops.
Semilunar valves shut
Pressure is lower but still higher than in the atria so the AV valves remain closed
Blood is either entering or exiting the ventricles
What causes the heart sounds? What are they called?
Heart sounds are caused by the sound of valves snapping shut
S1 is when the AV valves close during the isovolumetric contraction phase
S2 is when the SL valves close during the isovolumetric relaxation phase
Cardiac output
The amount of blood pumped into the pulmonary and systemic circuits in 1 minute
Also determined by the amount of blood pumped in one heartbeat (stroke volume)
Preload
The amount that the ventricles can stretch before they contract
Largely determined by the EDV (amount of blood in ventricles at end of filling phase)
Venous return
Amount of blood returning to the right atrium from the systemic circuit
Frank Starling Law
The more the ventricular muscles are stretched, the more forceful the contraction will be
Important during exercise when cardiac output must increase to meet the body’s needs
Contractility
Pumping ability/ability to generate tension
Increasing contractility increases SV and decrease ESV
Decreasing contractility decreases SV and increases ESV
Afterload
The force the the right and left ventricles must overcome in order to eject blood to their arteries
Determined by blood pressure
Increase in afterload generally decreases SV, rise in ESV
Decrease in afterload increases SV, lower ESV
What are chronotropic agents?
Factors that influence the rate at which the SA node depolarizes
Positive agents
- sympathetic nervous system
- hormones
- elevated body temp
Negative agents
- parasympathetic NS
- decreases body temp
