Mace Cardiovascular System Lecture 5a (Exam 3) Flashcards
What is the function of the cardiovascular system?
To move blood –> organ perfusion
To remove waste
What are the parts of the cardiovascular system and what are their functions?
- Heart = pumping station
- Blood vessels - Pathway - NO notable gas exchange in arteries or veins
Pulmonary capillaries exchange with air sacs
Systemic capillaries exchange with cells
Veins = carry blood back to the heart
Arteries = carries blood AWAY from the heart
T/F: Arteries and veins are mainly involved with gas exchange
False! They play a very small roll in gas exchange (5%)
ONLY capillaries allow for full gas exchange
T/F: The left side of the heart pumps more blood than the right
False!
The right and left must pump the SAME volume with each beat
If they don’t - will cause edema or pulmonary edema due to blood being left over
T/F: The left side of the heart has more/produces more pressure than the right
True!
What is the basic pattern of blood flow?
- R side of heart
- Lungs
(low pressure - lungs are close by - do not need a lot of pressure) - L side of heart
(thicker muscle and higher pressure pump) - Systemic cells
What are the functions of the two pump systems of the heart?
Each pump has a receiving chamber (atria) and a pumping chamber (ventricle)
R side: pumps deoxygenated blood to lungs
L side: pumps oxygenated blood to body
What are the Great vessels?
Arteries (arterial trunks) Pulmonary trunk Aorta Vena cavae (SVC and IVC) Pulmonary veins
What is the function of the arteries (arterial trunks)?
transport blood AWAY from the heart
What is the function of the pulmonary trunk?
Transports deoxygenated blood from the right side of the heart to the lungs
What is the function of the aorta?
Transports oxygenated blood from the L side of the heart
What is the function of the Vena cavae (SVC and IVC)?
Drain deoxygenated blood into the R side of the heart (RA)
What is the function of the pulmonary veins?
Drain oxygenated blood into the L side of the heart (LA)
What is the function of the R and L auricles?
They accept a large volume of blood rushing back to the heart.
Accept this blood until the cardiovascular system can adjust - ensure that this happens and no tearing/damage occurs to the arteries
What is the coronary sinus and what are the main takeaways that Mace wants us to know?
- Where blood goes out from ventricles
- Stops right before the RA - goes into a sinus called the Coronary Sulcus (between Atria and Ventricle)
- Drains heart of venous blood from the coronary veins
- In PULSATILE fashion blood is removed from that vessel ea. time the heart pumps
- When heart pumps - it squeezes ventricles - moving blood into the coronary sinus
- As heart relaxes - coronary sinus drops the blood into the atria
Describe the arteries of the Coronary Circulation
- The R coronary artery goes all the way around the coronary sulcus - to feed R side of the heart
- L coronary artery is very short - goes posterior to the pulmonary trunk and branches into:
- Circumflex artery (feeds the L side of heart)
- Anterior ventricular artery (LAD - goes down to the L ventricle)
Describe the Stop and Go contraction of the Coronary Arteries
- During contraction of the ventricles the vessels are compressed
- Ventricles relax - coronary arteries draw blood into the muscle itself
- Contraction = pushing blood up beyond the aortic valve into aorta towards the body
- Ventricles relax - blood sucked back towards heart
- Aortic valve closes - preventing backflow
- Closing of valve creates pressure at base of ascending aorta - pressure fills coronary arteries
To summarize, what is the function of the coronary sinus?
Drains the cardiac veins into the RA in a pulsatile fashion
How are arteries and veins packaged together?
packaged together in the same area
Ex: great cardiac vein & LAD go down the same coronary sulcus in all areas
The obstruction of the \_\_\_ will cause more severe myocardial infarction (MI) than the obstruction of any of the others? A. Left marginal vein B. Left coronary artery (LCA) C. Posterior interventricular vein D. Anterior interventricular branch E. Circumflex branch
B. Left coronary artery (LCA)
Would block everything downstream!
What is the flow of deoxygenated blood through the heart?
This should be seared into your brain by now!
- Deox blood to R atria (from SVC and IVC)
- Tricuspid valve
- R ventricle
- Pulmonary valve
- Pulmonary trunk –> artery
- Lungs
What is the flow of oxygenated blood through the heart?
- Blood comes back from the lungs via L and R pulmonary veins
- L atria
- Mitral valve
- L ventricle
- Aortic valve
- Ascending Aorta –> aortic arch
- Coronary Arteries –> Right Brachiocephalic trunk, L Common Carotid, L Subclavian
- Body (systemic system)
What is the fibrous skeleton of the heart?
Dense, irregular connective tissue
What are the functions of the fibrous skeleton?
- Provides SUPPORT for the atria and ventricle boundary (allows them to contract in a stable manner)
- Forms rings as valve anchors
- Rigid framework for cardiac muscle (muscles attach in spiral bundles)
- Electrical insulators (barrier between atria and ventricles)
What are the chordae tendinae? What is the function?
Attach to the thin AV valves in the ventricles
Secured by papillary muscles
Prevent opening of AV valves under pressure (during ventricular contraction)
Why do the papillary muscles contract just slightly before the rest of the ventricles?
They help to take the slack out of the cordae tendinae.
When ventricles contract - they pull on chordae tendinae and prevent prolapsing of the AV valves
Describe the structure of the semilunar valves
More structure compared to the AV valves
Responsive to pressure coming down from the great vessels
Responsive to pressure created when the ventricles contract (open) and when they relax (closed)
After entering the R atrium, the furthest a red blood cell will travel is the A. R ventricle B. Pulmonary trunk C. Superior vena cava D. Ascending aorta E. L atrium
C. Superior vena cava
What type of muscle makes up the heart?
Striated muscle
Describe the striated muscle of the heart
Short, branched cells
Stimulate one another in a wave
Interdigitated
(unlike skeletal striated muscle which has single, long cells)
What are intercalated discs?
Boundaries on either side of the cardiac muscle - connect each cardiac muscle together
(acts as a wave)
Cell membranes interdigitate
What are the 2 important components (proteins) of intercalated discs?
Desmosomes
Gap junctions
What is the function of desmosomes?
Proteins designed to bind cells together for STRENGTH
Prevention of tearing apart of cells
What is the function of gap junctions?
Allow for electrical impulses to transfer
low resistance transfer of electricity in the form of ions
What do the intercalated discs allow the heart to function as?
A functional syncytium (individual cells come together to function as one unit).
Important for allowing depolarization of the heart and evacuation of blood.
Repair of damage of cardiac cells occurs almost entirely by ___
fibrosis (scar tissue)
Metabolism requires what 3 things?
- Extensive blood supply
- High myoglobin (O2 storage)
- Creatine kinase (Cr phosphates) CK
Metabolism relies almost exclusively on ____ respiration
Aerobic
What substrates are used for producing aerobic respiration?
Glycogen/glucose Lactic acids Amino acids Ketone bodies (usage of substrates fluctuates)
The heart is highly susceptible to ___
ischemia
the heart really needs O2
T/F There is very limited use of anaerobic pathways in the heart?
True!
Which of the following structures allow one cardiac cell to electronically stimulate another by allowing ion flow across the intercalated disk? A. T-tubules B. gap junctions C. desmosomes D. intercellular folds
B. gap junctions
Describe the pathway of the depolarization of the conduction system
- Depolarization at SA node in RA
- Moves across RA and LA
- Comes to AV node (delay - allows contraction of atria and complete filling of ventricles)
- AV valve depolarizes - enters the AV bundle (Bundle of His)
- Interventricular septum
- R & L Bundle branches
- Out and around through Purkinji fibers
- Papillary muscles
What is the natural pacemaker of the heart? What is its intrinsic rate?
SA node
Rate of 100-110 bpm
(relatively independent)
What modifies the intrinsic heart rate of the SA node?
Vagal tone - through the medulla oblongata
Reduces rate to 60-80 bpm
What specific drug did Mace mention that alters the intrinsic rate of the heart?
Digitalis - blocks the intrinsic rate - depending on if the drug is in a therapeutic range or toxic range - will determine if it increases or decreases vagal tone
T/F Contraction and depolarization are the same thing
False!!!
Can have a depolarization that DOES NOT result in a contraction
Do depolarization and contraction occur at the same time? What does this mean when you are interpreting an EKG?
NO! They occur at different times
EKG = electrical activity - depolarization! NOT contraction (depolarization is followed by contraction)
What is the cardiac center?
Medulla oblongata - houses cardio-acceleratory and inhibitory center
Does NOT initiate heartbeat
SA nodal activity leads to ____
autorhythmicity
What are the steps of the SA nodal activity pathway
- Reaching threshold - SLOW voltage-gated Na+ channels open. Slow inflow of Na+ changes membrane potential from -60mV to -40 mV
- Depolarization - FAST voltage-gated Ca2+ channels open. Inflow of Ca2+ changes membrane potential from -40mV to just above 0mV
- Repolarization - FAST voltage-gated Ca2+ channels close. Voltage-gated K+ channels open allowing K+ outflow. Membrane potential return to -60mV. Voltage gated K+ channels close
What is the pacemaker potential?
Number 1 on the graph (the range from -60mV to -40mV)
It is the opening of SLOW Na+ voltage gated channels
(vagal tone will affect/change this)
What does the AV bundle delay allow for?
Allows for the atria to completely finish contracting and filling the ventricles prior to ventricular contraction
How does the muscular contraction (AP) of skeletal muscles compare to cardiac muscle?
The contraction of skeletal muscle for a single stimulation is very delayed in its depolarization compared to the action potential
The delayed closing of Ca2+ channels (slow to close) creates a ___ refractory period for cardiac muscle.
Longer
What does a longer refractory period in cardiac muscle allow for?
This allows for NO tetany (any kind of wave summation in the cardiac muscle)
Frequency of stimulation does NOT lead to wave summation - it always goes back to its relapsed form
Describe Phase 0 of the action potential of cardiac muscle
Rapid Na+ influx through open, FAST Na+ channels (steep depolarization)
In Phase 1 of the action potential of cardiac muscle, transient K+ channels open and what occurs?
K+ efflux returns TMP to 0mV
In Phase 2 of the action potential of cardiac muscle there is an influx of Ca2+ through ___ Ca2+ channels. What is this electrically balanced by?
L-type
Balanced by K+ efflux through DELAYED rectifier K+ channels
In Phase 3 of the action potential of cardiac muscle Ca2+ channels ___ but delayed rectifier K+ channels remain ___ and return TMP to -90mV
Ca2+ channels CLOSE but delayed rectifier K+ channels remain OPEN
Which of the following statement is incorrect?
A. The firing of the SA node stimulates both atria to contract almost simultaneously
B. The signal to contract is delayed at the AV node, allowing the ventricles to fill with blood
C. Firing signals reach the papillary muscles before the rest of the ventricular myocardium
D. Ventricular contraction begins at the AV valves and progresses downward toward the apex of the heart.
D.
If the ventricular contraction began at the AV valves down to the apex, this would “blow out” the bottom of the heart.
Ventricular contraction goes down through the middle and contracts upwards to push the blood out through the great vessels
Step 1: During Atrial Contraction and Ventricular Filling the atria ___ and the ventricles ___
Atria contract
Ventricles relax
Step 1: During Atrial Contraction and Ventricular Filling what happens to the ventricular pressure and the valves?
Ventricular pressure:
< atrial and
< arterial trunk
AV valves open
Semilunar valves closed
Step 2: During Isovolumetric Contraction the atria ___ and the ventricles ___
Atria relax
Ventricles contract
Step 2: During Isovolumetric Contraction what happens to ventricular pressure and the valves?
Ventricular pressure:
> atrial
< arterial trunk
AV valves closed
Semilunar valves closed
Step 3: During Ventricular Ejection the atria ___ and the ventricles ___
Atria relax
Ventricles contract
Step 3: During Ventricular Ejection what happens to ventricular pressure and the valves?
Ventricular pressure:
> atrial
> arterial trunk
AV valves are closed
Semilunar valves are open
Step 4: During Isovolumetric Relaxation the atria ___ and the ventricles ___
Atria relax
Ventricles relax
Step 4: During Isovolumetric Relaxation what happens to the ventricular pressure and the valves?
Ventricular pressure:
> atrial
< arterial trunk
AV valves closed
Semilunar valves closed
Step 5: During Ventricular Filling the atria ___ and the ventricles ___
Atria relax
Ventricles relax
Step 5: During Ventricular Filling what happens to the ventricular pressure and the valves?
Ventricular pressure:
< atria
< arterial trunk
AV valves open
Semilunar valves closed
T/F: When the ventricles relax, blood in the aorta flows back toward the heart, filling the coronary arteries
True!
When the ventricles relax, blood in the aorta flows back towards the heart instead of out to the body, filling the coronary arteries
During a normal cardiac cycle, which phase has the longest duration? A. atrial systole B. ventricular systole C. quiescent period D. valvular period
C. quiescent period
Cardiac Output is the amount of blood pumped ___ of the heart by 1 ___ in 1 minute (ml/min)
out
ventricle
Cardiac Output (CO) = ?
Stroke Volume (volume/beat) x HR (bpm)
What is the average resting cardiac output?
Around 5-7 L/min
With HF this would be much less (peripheral tissue needs are not being met)
What can increase Cardiac Output (CO)?
Exercise!
HR increases and so does SV
Athletes can reach as high as 40 L/min
What is Cardiac Reserve?
The increase of CO ABOVE resting level
COex - COrest = Cardiac Reserve
Athletes will have a high Cardiac Reserve
Assuming that the left ventricle of a child's heart has an EDV=90ml, and ESV=60ml, and a CO of 2,400 ml/min. His SV and HR are A. SV=30ml/beat, HR=80 bpm B. SV=40ml/beat, HR=60 bpm C. SV = 80ml/beat, HR=30 bpm D. SV = 150ml/beat, HR=16 bpm E. SV = 16ml/beat, HR=150 bpm
A.
SV = 90ml - 60ml = 30ml/beat
CO = (SV) x (HR) CO = 2,400 2,400 = (30 ml/beat) x (HR) 2,400/30 = 80 bpm = HR
Mace said to be prepared to do these types of calculations for the exam!
Factors affecting Heart Rate are called?
Chronotropic
What factors affect Heart Rate?
Autonomic regulation
Baroreceptor reflex
Chemoreceptor reflex
Extracellular ions, body temperature
What are the 2 different changes you will see in persistent HR changes
Bradycardia
Tachycardia
Sympathetic NS innervates the AV and SA node leading to ___ in the myocardium, affecting also contractility/inotropy
tachycardia
Parasympathetic NS innervates the AV and SA nodes leading to ___
bradycardia
What is the baroreceptor reflex?
Stretch in heart muscle (as a result of low HR)
Adjusts HR and MAP by altering the force and speed of heart contractions and TPR (total peripheral resistance)
What is the chemoreceptor reflex?
Measures O2, CO2, and pH (a powerful mediator for HR)
What are the extracellular ions that affect HR?
K+ (especially)
Ca2+ (also an inotropic agent aka affects contractility)
One degree of body temperature change (Celsius) increases HR by ___ beats
10 beats
With exercise you are usually warmer and therefore need an increased HR. Also with a fever b/c you want to send more WBCs, RBCs, O2, etc. to metabolically active cells to fight off infection
All of the following are heart rate stimulants except A. epinephrine B. caffeine, nicotine, and chocolate C. thyroid hormone D. potassium (and Ca2+ ions)
D. potassium (and Ca2+ ions)
Need to think about where K+ and Ca2+ are and if there is a low or high concentration
The main affect of Ca2+ ions = inc contractility = most often a decreased HR
TH increases metabolic activity = inc temp = inc CO2 = inc HR
What are factors that affect Stroke Volume?
- Venous return (volume of blood returned to the heart per unit)
- Inotropic agents
- Afterload
How does increased venous return affect SV?
- Increased venous return (occurs with greater venous pressure or slower HR)
- Increases stretch of heart wall (PRELOAD), which results in greater overlap of thick and thin filaments in sarcomeres
- Additional cross-bridges form - ventricles contract with greater force
- SV INCREASES
(opposite is seen with smaller venous return e.g. hemorrhage or extremely rapid HR)
How do Inotropic agents affect SV?
Inotropic agents act on the myocardium to alter contractility
- Positive inotropic agents (e.g stimulation by SNS)
- Inc Ca2+ in sarcoplasm = greater binding of Ca2+ to troponin of thin filaments w/i sarcomeres
- Additional cross-bridges form - ventricles contact with greater force
- SV INCREASES
(opposite seen with negative inotropic agents e.g. CCBs)
How does Afterload affect SV?
Afterload is the resistance in arteries to ejection of blood
- Atherosclerosis is typically only a factor as we age (arteries cannot expand)
- Arteries become more narrow in diameter
- Increases the resistance to pump blood into arteries
- SV DECREASES
(decreased afterload = improved SV)
What determines the afterload?
Performance of the L ventricle
How hard it is to push blood into the arteries themselves
Which of the following increases stroke volume proportionally? A. increased venous return B. increased Ca2+ in sarcoplasm C. afterload D. A and B E. all of the above
D. A and B
Inc venous return (Starling law)
Inc Ca2+ in sarcoplasm (due to inc force of contraction is inotropic)
Afterload (not specified if it was increased or decreased)
If afterload was decreased then this would increase SV but the opp is true if it increases
Death of heart muscle from lack of O2 is known as myocardial infarction (MI), but what is temporary myocardial ischemia called? A. cardiac stenosis B. cardiac defibrillation C. angina pectoris D. cardiac arrest
C. angina pectoris
Cardiac stenosis and Cardiac arrest are NOT temporary
Cardiac defibrillation is shocking of the heart to get it to depolarize
What happens if LV output exceeds RV output? Where is the problem?
Pressure backs up
Fluid accumulates in system tissue
The problem is in the R heart - failure to maintain equal flow in and out
What happens if RV output exceeds LV output?
Pressure backs up
Fluid accumulates in pulmonary tissue
What affect do chronotropic agents have on HR?
Alter SA and AV nodes
Positive agents = Inc HR –> Inc CO
Negative agents = Dec HR –> Dec CO
Venous return and Positive Inotropic Agents are ___ correlated with SV. They both ___ SV and CO
Directly
Increase
Afterload is ___ related to SV
Inversely
Muscular contractions ___ venous return by directing venous blood to the RA
Increase
Large reductions in blood volume due to bleeding or dehydration ___ venous return.
Reduce
Changes in peripheral blood flow patterns can ___ or ___ venous return
Increase or Decrease
Changes in venous return affects what?
End diastolic volume (EDV)
What does the EDV determine?
The myocardial preload, or the amount of sarcomere stretching at the end of diastole
The amount of preload affects the ESV by influencing the ____ of contractions
Efficiency
The greater the contractility the ___ the ESV
Smaller
Vasodilation ___ afterload
Decreases
Vasoconstriction ___ afterload
Increases
The greater the afterload, the lower the pumping efficiency of the heart, and the ___ the ESV
Larger
SV = EDV - ?
SV = EDV - ESV
Many hormones ___ contractility in addition to their affects at other target organs. What are some examples?
Increase
TH, Epi, NE
What is ESV?
The volume of blood left in the ventricles after contraction
T/F: An EKG represents electrical activity and mechanical components of the heart
False!
ONLY electrical activity
What does the P wave represent?
Atrial depolarization
atrial contraction occurs in the middle of the P wave
What does P-Q segment on an EKG represent?
Atrial contraction and the AV node delay
What does the QRS complex represent?
Atrial repolarization overlaps with ventricular depolarization
(at the tip of R is where ventricular contraction initiates)
Also, R-S and slightly past S = the isovolumetric contraction phase
What does the S-T segment on an EKG represent?
Ventricular contraction
What does the T wave represent?
Ventricular repolarization
Also, the end of the T wave = the isovolumetic relaxation phase (overlaps with relaxation)
What does the T-P segment on an EKG represent?
Quiescent period (longest period in cardiac cycle)
What is happening in the quiescent period?
Blood is flowing (passively) into both atria and also filling the ventricles
What does the P-R interval represent?
SA node action potential through the conduction system to the AV node
What does the Q-T interval represent?
The muscle action potential through the ventricles
____ is the generation/creation of new blood vessels
Angiogenesis
The increase in blood flow in skeletal muscle during exercise is an example of ___ ___
Active hyperemia
___ ___ is the increase in blood flow to an area after blood flow has been temporarily blocked
Reactive hyperemia
On a normal EKG, repolarization of the atria is not evident. Why?
The repolarization of the atria has a much smaller amplitude than the ventricular depolarization so it is masked
