Test 2 Cardiac System Flashcards
ventricular contraction
systole
ventricular relaxation
diastole
explain the 4 stages of the cardiac cycle
1: ventricular filling (isotonic-no contraction occurring-no pressure)
2: ventricular contraction (isometric; tension being developed but no change in circumference) – pre-ejection
3: ventricular contraction (isotonic) – ejection; change is occurring
4: ventricular relaxation (isometric)
All cardiac valves are designed to only allow _____ of blood between chambers, dependent on ______
one-way flowpressure differential
What are the 4 valves in the heart? what is their purpose?
aortic, pulmonic, mitral, and tricuspid
one way blood flow in the heart( 2 way blood flow is a disorder)
When a valve is _____ it only allows one way blood flow, i.e., easy flow in the proper direction
“competent”- working the way it should be
Backward flow of blood through a one-way valve is called ______
“regurgitation”- can cause a murmur
Resistance to the normal direction of blood flow through a valve is usually caused by valve _______.
“stenosis” (means narrowing or constriction of a passage)
What are the semilunar valves of the heart?
aortic and pulmonic valves
Name 3 characteristics of the aortic and pulmonic valves.
- Firm, thick valves between ventricles and pulmonary artery and aorta
- Three valve leaflets (tricuspid)
- Prevent back flow (“regurgitation”) into ventricles
Name the atrioventricular or AV valves of the heart and how many leaflets each has.
Tricuspid-3 leaflets and mitral valves-2 leaflets
What is the lub dub sound?
the semilunar valves opening and closing
a think cartilage band that hold valves tightly together to avoid leaking when the heart is pumping
the valve annulus
Which valves are thick, flexible valves between atria and ventricles? Floppy like a parachute
tricuspid and mitral valves
which valves are stabilized with chordae tendinea attached to papillary muscles (1 muscle and chord bundle for each leaflet)?
tricuspid and mitral
dense connective tissue cords connecting valves to papillary muscles
Cordae tendinea
_____ contract during ventricular systole and maintain tension throughout systole
Papillary muscles
Heart and blood flow competency depends on coordinated what 4 things?
function of the annulus, valve leaflets, papillary muscles, and ventricular walls
: when ventricles contract (opens semilunar valves and closes AV valves)
Ventricular systole
when the ventricles relax and blood flows into them from the atria (results in closing of the semilunar valves due to artery back pressure)
Ventricular diastole
when atria contract (opens the AV valves)
Atrial systole
when the atria relax and blood flows into them from the vena cava (R) and the pulmonary vein (L)
Atrial diastole:
True or False: there is no electrical connection btw the upper and lower parts of the heart
true
Which valve is the only bicuspid valve?
mitral valve
narrowed valve opening due to thickening, calcification, or non-separation of leaflets
Stenosis
What can result from malfunction?
disease
backwards blood flow due to stretching, stenosis, papillary muscle or cordae tendinae disruption
Regurgitation
the absence of valve formation in utero/the incomplete formation
“atresia”
*Most commonly occurs with the pulmonic valve
Heart (and vascular) sounds are caused by _____
vibration
describe the two normal sounds heard from the heart
First is a low “lub” (S1) as the AV valves close at the start of ventricular systole
Second is a high-pitched “dup” (S2) as the semilunar valves close after ventricular systole
High rate of blood flow into chambers (e.g., 3rd and 4th heart sounds) could mean what for a patient?
heart failure
______ are abnormal sounds heard in various parts of the vascular system
Murmurs and bruits
Murmurs are sounds caused by _______, most commonly around valves
blood turbulence in the heart
*(late aortic stenosis)
Bruits (pronounced “brew-ee”) are sounds caused by _______
blood turbulence in blood vessels
*(carotid bruit)
Know the blood flow throughout the heart
veins carry oxygenated blood
arteries carry deoxygenated blood
What are the 3 major epicardial arteries (outside heart)?
Left common coronary artery divides into:
-Left anterior descending (LAD) artery: Supplies the apex, left anterior wall, anterior septum
_Left circumflex artery:
Supplies the lateral left
Right coronary artery:
Supplies the right wall, posterior wall, posterior septum
What is the second sound we hear that is associated with pulse?
S2-closure of semilunar valves
What is the first sound we hear that is not associated with pulse?
S1- closure of av valves
Smaller branches extend from the coronary arteries, penetrating into and perfusing the myocardium
intramural arteries
When the left ventricle contracts, the aortic valve opens. The valve cusps prevent what?
filling of the coronary arteries
When the left ventricle relaxes, aortic pressure closes the aortic valve, allowing what?
the coronary arteries to fill
only time the heart is receiving blood flow
diastole
From most superficial to deep, how is the heart blood vessels arranged?
coronary arteries–>intramural arteries–>capillaries
gets smaller and smaller
Blood from heart muscle is drained by what into what?, then into what?
cardiac veins; coronary sinus; right atrium
true or false: coronary veins generally run parallel to coronary arteries
true
_____ are electrically conductive cells which discharge rhythmically and continuously, starting an electrical impulse which normally travels through conductive pathways (specialized cardiomyocytes)
Pacemakers
How many pacemakers in the heart?
2;Sinoatrial node (SA node; “pacemaker”) and Atrioventricular node (AV node)
What is the normal pacemaker of the heart?
Sinoatrial node (SA node; “pacemaker”)
what is the gate keeper between the atrium and ventricles?
Atrioventricular node (AV node)
what are present in the atria, ventricles or conductive tissue and can take over when the SA and AV nodes aren’t functioning or conduction is blocked?
“Latent pacemakers”
what connects the electrical discharge through the atriums?
Internodal atrial pathways
Where does the bundle of his separate to?
RBB and LBB
The fastest pacemaker always sets the pace: __ > __ > _____
SA (60-100 per min)> AV > inherent ventricular pacemakers
*if something is higher than SA it could be tachycardia
purkinje system
the smallest fibers of the bundle branches
Why do pacemakers never enter resting potential?
they’re always preparing for or participating in an AP
Explain the 1st stage of pacemaker action potential.
1st phase (4 on figure): Slow passive Na+ inward movement (if – red) At ~ -50 mV, Ca2+ T (transient) channels open, slow inward movement (green)
Explain the 2nd phase of pacemaker action potential
2nd phase (0 on figure): At threshold (~ -40 mV), Ca2+ L (long) channels open, faster inward movement go ions (blue)
Explain the 3rd phase of pacemaker action potential
At ~ 0 mV the Ca2+ L channels close and K+ channels open (orange), fast K+ outflow to return potential to ~ -60 mV
What normally sets the pace in cardiac conduction?
SA node
*But fastest pacemaker ultimately controls heart rate
What conduct to the AV node in cardiac conduction?
Internodal pathways
*Atrial myocytes depolarize following internodal pathway depolarization
What delays transmission to the bundle of His in cardiac conduction? (delays conduction from upper to lower part of the heart)
AV node
*Facilitates coordination of atrial and ventricular contraction
What is the path from the bundle of His in cardiac conduction?
Bundle of His to bundle branches to Purkinje fibers to ventricular myocytes – very rapid
What is a measure of electrical activity in the heart?
The electrocardiogram (ECG, previously called the EKG)
What are branched and conduct depolarizations through intercalated disks?
Cardiomyocytes
What do atrial myocytes secrete?
atrial natriuretic peptide (ANP) with atrial distension (stretch)
What does ANP cause?
vasodilation, diuresis (increased water excretion into urine) and Na+ excretion
What do ventricular myocytes produce?
produce B-type natriuetic peptide (BNP) with ventricular distention (similar effects to ANP)
What is qrs associated with?
depolarization of ventricles
Why do we measure blood BNP concentration?
an indicator of ventricular stretch, e.g., with heart failure
What is the average BPM for most people?
70 BPM
What is the normal sinus rhythm?
means HR coming from SA node
If you have a slower or junctional rate about 40-59 BPM where is that coming from?
AV node
If you have a very slow rate under 40 BPM aka ventricular rate, where is that coming from?
Purkinje fibers and myocardial cells
If there is no P wave on an ECG, what does that mean?
something wrong with SA node
Myocytes in the heart (cardiomyocytes) release 2 hormones. What are they?
ANP and BNP (BNP is primary lab test that tests if someone has heart failure but there is stretch on the heart)
What provide strong union between fibers via desmosomes and provides low-resistance bridges for the spread of excitation from one cell to another via gap junction channels?
intercalated disks
Describe cardiomyocyte action potential.
- -Rapid depolarization (phase 0) due to Na+ influx through rapidly opening Na+ channels (the Na+ current, INa)
- -Initial rapid repolarization (phase 1) due to inactivation of Na+ channels and activation of repolarization process (phase 3) due to net K+ efflux through K+ channels
- -Plateau (phase 2) due to Ca2+ influx through more slowly opening Ca2+ L(long or slow channels) channels (the Ca2+ current, ICa)
- -Rapid repolarization process (phase 3) due to closure of Ca2+ channels with continued K+ efflux through K+ channels
- -Return to the resting membrane potential (phase 4)
What provides all parasympathetic control?
vagus nerve
What are the stimulation effects of the parasympathetic system on the heart?
- Decrease HR by decreasing SA and AV node pacing rate
- Does not affect myocardial contractility (force)
What nerves are responsible for the sympathetic nervous system?
spinal T2-T4 segments (thoracic vertebra)
**Pass into the cardiac plexus to the SA node (right) and AV node (left)
What are the stimulation effects of the sympathetic nervous system?
- Increase HR via increasing SA and AV node pacing rate
- Increase in myocardial contractility (force, therefore cardiac output)
The pressure developed in the ventricle is proportional to the ventricular end-diastolic volume, i.e., increased stretch of myofibrils results in increased contractile force, resulting in increased stroke volume
Frank-Starling Law
What are three things the heart has in reference to oxygen?
- -An abundant blood supply providing O2 and nutrients
- -High myoglobin content (muscle O2 “storage” protein)
- -Many mitochondria (fat metabolism, requires more O2)
Myocytes derive most of their energy from aerobic metabolism. Does this require continuous supply of O2?
yes
What are the sources myocytes receive energy from?
Glucose (35%)
Ketones and amino acids (5%)
Fat (60%)
Pericardium is a fibrous sack which _____ and _____ it from thoracic viscera
encloses the heart; separates
What are the two layers of the pericardium?
- Visceral: thin inner layer, directly attached to the myocardium
- Parietal: tough, fibrous out layer
Space between the visceral and parietal pericardium (the pericardial sac) contains 5 to 30 mL of clear ______.
Lubricates to minimize what?
pericardial fluid;
friction
The heart is fully developed by pregnancy week ____.
7 or 8
In utero function of ductus arteriosis and foramen ovale is to _____.
reduce blood flow to lungs
Within a few days after birth the ductus arterioles closes off completely and forms what?
ligimentum arteriosum
*Sometimes remains open (“patent ductus arteriosis”)
_____ (between atria) closes at birth and gradually fuses together over several weeks or months.
Foramen ovale
*Sometimes remains open (“patent foramen ovale”)
Rate x stroke volume = ____
total cardiac output
