Circulatory System: Heart Flashcards
The cardiovascular system is composed of what?
The heart and blood vessels
The circulatory system is composed of what?
The, blood vessels, and the blood
What are the two major divisions of the circulatory system?
The pulmonary circuit-right side of the heart
The systemic circuit-left side of the heart
What is the function of the pulmonary circuit?
it carries blood to the lungs for gas exchange and back to the heart
What is the function of the systemic circuit?
Supplies oxygenated blood to all tissues of the body and returns it to the heart
What side of the heart receives oxygen rich blood and send it out and which side receives oxygen poor blood
Left side receives Oxy rich blood and sends it out
right side receives oxy poor blood and sends it to the lungs
What blood vessel does oxygen rich blood travel through to leave the heart?
the aorta
what blood vessel does oxygen poor blood leave the heart through when traveling to the lungs
the pulmonary trunk
What is the pericardium?
the double-walled sac that encloses the heart
What is the function of the pericardium?
Allows the heart to beat without friction while also resisting excessive expansion
What is the serous membrane that covers the heart?
the visceral pericardium
What are the three layers of the heart wall?
Epicardium
myocardium
endocardium
What is the epicardium?
the outter layer of the heart wall
What is the endocardium?
the smooth inner lining of the heart and blood vessels
What are the two components of the myocardium
the layer of cardiac muscle
the fibrous skeleton of the heart
What does the atrioventricular sulcus seperate?
The atria and ventricles
What is the interventricular sulcus?
The sulcus that divides the right ventricle from the left
What do the sulci of the heart contain?
the coronary arteries
What is the name of the wall that separates the atria?
the interatrial septum
What are the pectinate muscles
the internal ridges of the myocardium in the right atrium and both auricles
What is the name of the muscular wall that separates the ventricles?
the inter-ventricular septum
What are the internal ridges of the ventricles and what are their function?
The trabeculae carneae
prevent ventricular walls from sticking together
What is the name of the right atrioventricular valve
the tricuspid valve
What is the name of the left atrioventricular valve?
the mitral valve aka the bicuspid
What is the name of the cords that attach the AV valves to the papillary muscles?
the chordae tendineae
Where is the pulmonary semilunar valve located?
between the right ventricle and the pulmonary trunk
where is the aortic semilunar valve located?
between the left ventricle and aorta
What % of total blood volume is pumped to the heart itself?
5%
Where does the coronary artery branch from?
the ascending aorta
What are the two main branches of the Left coronary artery?
- the anterior inter-ventricular branch
- the circumflex branch
Where does the interventricular branch of the LCA supply blood?
Both ventricles and the anterior two thirds of the inter-ventricular septum
Where does the circumflex branch of the LCA supply blood to?
the left atrium and the posterior wall of the left ventricle
The RCA supply blood to____ before it brances
the right atrium and the SA node
What ate the two main branches of the RCA? what do they supply?
- The right marginal branch-lateral aspect of right side of heart
- Posterior interventricular branch-posterior walls of the ventricles
Flow through the coronary arteries is greatest when _____
the heart relaxes
Angina pectoris is ____
chest pain from partil obstruction of the coronary blood flow
5-10% of coronary blood drains directly into the ____ via the ___ veins
right ventricle
thebesian veins
Most of the coronary blood drains back into the heart via the _____
coronary sinus
What are the three main inputs of the coronary sinus?
- great cardiac vein
- posterior interventricular vein
- left marginal veins
What are cardiomyocytes?
cardiac muscle cells
Repair of damage to cardiac muscle is almost entirely by ___
fibrosis
What are the three features of the intercalated disks?
interdigitating folds
mechanical junctions
electrical junctions
What are the two types of mechanical junctions in cardiac muscle?
- The fascia adherens
- the desmosomes
What are fascia adherens?
where the actin of the muscle cells are anchored to the plasma membrane of the adjoining cell via trans-membrane proteins
What are the electrical junction in cardiac muscle?
gap junctions
Why is cardiac muscle fatigue resistant?
because it makes very little use of anaerobic fermentation
What is the primary pacemaker in the heart? what is it exactly?
The sinoatrial node (SA)
a grouping of modified cardiomyocytes
Where is the SA node located and what is its function?
located in the right atrium near the base of the superior vena cava
it initiates each heart beat and sets heart rate
What occurs once the SA node activates?
the atria contract?
What are the five steps f heart contraction?
- The SA node fires
- The atria contract
- the AV node is activated
- impulse travels down the AV bundle(bundle of his)
- The ventricles contract in a upward path
What do sympathetic nerves do to the heart?
they increase heart rate
What parasympathetic nerve is associated with the pacemakers of the heart?
the vagus nerve
Systole=
Contraction
Diastole=
relaxation
What is sinus rhythm?
normal heartbeat triggered by the SA node
70-80 bpm (vagal tone)
What is ectopic focus?
a region of spontaneous firing other than the SA node?
What causes ectopic focus?
-If SA node is damaged\
If the SA node is damged what takes over?
The AV node at around 40-50 BPM
What is unique about the resting membrain potential of the SA node cells?
It is not stable. It has a stead increase due to leaky sodium channels
Why does the heart contraction impulse slow down between the atria and the ventricles?
to allow time for the ventricles to fill
What is unique about the action potential of myocardium?
After the AP peaks it plateau’s
What allows the AP of myocardium to plateau?
After the peak of the AP calcium channels open slowing down the contraction
Why is the plateau phase of myocardial contraction important?
because it prevents summation and tetanus that could potentially stop the heart
What is an EKG/ECG?
a composite of all action potentials of nodal and myocardial cells detected, amplified, and recorded by electrodes
The P wave of an EKG is what event?
the firing of the SA node, depolarization and contraction of the atria
How long after SA signal does atrial systole begin?
100ms
The QRS complex wave of an EKG is what event?
the ventricular depolarization
The ST segment of an EKG is what event?
the plateau in myocardial action potential
The T wave of an EKG is what event?
Ventricular repolarization
What is V-Fib
Ventricular fibrillation
What is a ventricular fibrillation?
a serious arrhythmia caused by electrical signals traveling randomly
What is the intention of Defibrillation?
the depolarize the entire myocardium in hopes that it will reset the heart to sinus rhythm
the cardiac cycle is ___
one complete contraction and relaxation of all four chambers of the heart
What is valvular insufficiency ?
any failure of a valve to prevent reflux
What is valvular stenosis?
when the cusps are stiffended and the opening is coonstricted by scar tissue
what causes heart murmurs?
regurgitation of blood through incompetent valves
The fist heart sound is the sound of ____
the closure of the AV valves, turbulence, and movments of the heart wall
the second heart sound is___
the closure of the semilunar valves
What are the four phases of the cardiac cycle?
Ventricular filling
Isovolumetric contraction
ventricular ejection
isovolumetric relaxation
What occurs during the ventricular filling phase of the cardiac cycle?
- Ventricles expand and pressure drops below that of atria
- AV valves open and blood flows into ventricles three phases of filling
What are the three phases of ventricular filling?
- Rapid filling-first 1/3
- Diastasis: slower filling (second 1/3) P wave occurs at the end of this step
- Atrial systole: atrium contracts filling the final 1/3
What is the average EDV in each ventricle?
about 130mL
What occurs during the isovolumetric contraction phase of the cardiac cycle?
- the atria repolarize and are done
- Ventricles depolarize and cause QRS complex
- AV valves close
- S1 occurs
What does Isovolumetric contraction mean?
the ventricles are contracting but not yet ejecting blood as the pressure in the aorta and pulmonary trunk are still too high
What occurs during the ventricular ejection phase of the cardiac cycle?
- Pressure peaks in the ventricles causing the opening of the semi-lunar valves
- Blood is ejected first in a quick burst than slower as pressure decreases
- Corresponds with plateau phase of cardiac action potential
- T wave occurs late in this phase
Normal stroke volume is ?
70mL
What is norm ESV?
around 60mL
What occurs during the isovolumetric relaxation phase of the cardiac cycle?
- T wave ends and ventricles begin to expand
- Semi-lunar valves close
- S2 occurs
Atrial systole lasts about ____ seconds?
0.1
Ventricular systole lasts about ___ seconds?
0.3
Quiescent period lasts about ___ seconds?
0.4
Congestive heart failure (CHF)is a result of?
Failure of either ventricle to eject blood effectively
What are some causes of CHF
Weak heart due to MI
chronic hypertension
heart defects
What occurs if the left ventricle fails
the blood backs up into lungs causing pulmonary edema
What occurs if the right ventricle fails?
blood backs up into the vena cava causing systemic edema
Cardiac output is___
the amount ejected by each ventricle in 1 minute
How is Cardiac output calculated?
Heart rate X Stroke volume
What is the cardiac reserve?
the difference between a persons max CO and resting CO
What is Tachycardia?
A resting heartbeat of 100bpm or higher
What is bradycardia
resting heartrate of less than 60 bpm
What is a positive chronotropic agent?
factors that raise heartrate
what is a negative chronotropic agent?
factors that lower heartrate
What is the autonmic nervous systems role in heart rate?
it modulates the rhythm and force
Sympathetic postganglionic fibers are ___
adrenergic
What occurs when norepinephrine binds to the heart?
it activates cAMP second messenger system in cardiomyocytes and nodal cells
What does the activation of cAMP do to the cardiac cells
- leads to the opening of Ca++ channel
- increased Ca++ accelerates depolarization of SA node
- accelerates the uptake of Ca++ as well leading to a quick relaxation of the heart as well
How does the parasympathetic vagus nerve effect heartrate?
- it releases ACh
- this opens K+ gates in nodal cells
- The increased outflow of K+ causes hyperpolarization and less frequent firing
Without influence the hears standard rate is?
100bpm
What is vagal tone?
Steady background firing rate of the vagus nerves
around 70-80 BPM
What do Baroreceptors detect?
pressure in the arteries
How does nicotine effect heartrate?
increases it by stimulating catecholamine secretions
how does thyroid hormone effect heart rate?
it increases the number of adrenergic receptors on the heart so it is more responsive to adrenergic stimulation
How does caffeine effect heart rate?
it inhibits cAMP breakdown, prolonging adrenergic effects
How does Hyperkalemia effect heart rate?
it makes the heart less excitable slowing it down
how does hypokalemia effect heart rate?
the cells hyper polarize and require more stimulation
How does hypercalcemia effect heart rate?
decreases heart rate and contraction strength
how does hypocalcemia effect heart rate?
increases heart rate and contraction strength
What three variabes govern stroke volume?
preload
contractility
afterload
What is frank-starlings law of the heart
Stroke volume is proportional to the end diastolic volume
What is the afterload in the heart?
the sum of all forces opposing ejection of blood from the ventricles
What do Proprioceptors signal?
the cardiac center to prepare it for activity
What is Coronary artery disease?
a constriction of the coronary arteries
What are foam cells?
Macrophages that have absorbed fat and balloon up
What is a major risk factor for CAD
excess LDL leves
