(Lectures 10-11, Chapter 14) The Heart Flashcards
3 components of the cardiovascular system
- Heart
- Blood vessels
- Blood
Examples of the transport of substances
- Oxygen/nutrients to cells
- Waste to liver/kidneys
- Hormones, immune cells, clotting factors to target cells
Pulmonary Circulation
- Movement of blood between the heart and lungs
- Sends deoxygenated blood to the lungs
- Blood is ejected from the right pump
Systemic Circulation
- Movement of blood between the heart and all organs/tissues (except the alveoli)
- Blood is ejected from the left pump
Arteries vs veins
Arteries carry blood away from the heart, veins carry it to the heart
Capillaries
Blood vessels with very thin walls - site of substance exchange between organs/tissues and blood
Arterioles and venules
Connect arteries and veins (respectively) to capillaries
Is systemic circulation parallel or in series?
Parallel; blood flows through many organs at once (artery -> organ/tissue -> vein -> heart)
Is pulmonary circulation parallel or in series?
Series (RA -> RV -> Lungs -> LA -> LV)
T/F: the base of the heart is the bottom of it, and the apex is the top
False; it’s the other way around
The heart is found in the ______ cavity
thoracic
Components of the heart wall (3)
- Epicardium: external protective layer
- Myocardium: middle layer w/cardiac muscle cells
- Endocardium: inner layer of epithelial tissue, continuous with major blood vessels
Pericardium
- Fluid-filled sac that surrounds the heart
- Provides protection, lubrication
- Anchors the heart in the thoracic cavity
What feature of the atria and ventricles demonstrates the difference in how much pressure they experience?
Thickness of walls; atria have much thinner walls than ventricles
Major blood vessels leading to/from the heart (4)
- Superior/inferior vena cavas bring deoxygenated blood to the heart
- Pulmonary trunk carries deoxygenated blood to the lungs
- Pulmonary veins carry oxygenated blood to the heart
- The aorta sends oxygenated blood to the rest of the body
Atrioventricular valves
- The bicuspid/mitral valve separates the left side of the heart
- The tricuspid valve separates the right side
These tissues in the heart hold the AV valves in place
Chordae tendinae
When do the AV valves open?
When atrial pressure exceeds ventricular pressure
Semilunar valves
- Aortic valve separates the LV and aorta
- Pulmonary valve separates the RV and pulmonary trunk
When do the semilunar valves open?
When the heart (ventricles) contracts
How is the heart supplied with blood?
Coronary arteries/veins
What separates the left and right sides of the heart?
Septal wall
Steps of heart contraction
- Atria contract
- AV valves open
- Ventricles contract
- SL valves open
What are some ways in which cardiac muscle differs from skeletal muscle? (6)
- Many types of cells
- Fewer progenitor stem cells
- Limited ability to repair
- Multiple cells form a fiber
- Cells only grow by expansion (# of cells doesn’t increase)
- Rely on mostly aerobic respiration
What structure joins cardiac muscle cells?
Intercalated discs
Types of cellular junctions in intercalated discs
- Desmosomes hold cells together, but still allow some movement
- Gap junctions let electrical signals travel between cells
Intercalated cells let the heart function as a _______.
syncytium
Where are pacemaker cells found? What unique characteristic do they have?
- Found in the sinoatrial (SA) and atrioventricular (AV) nodes
- Cells can spontaneously depolarize
Steps of cardiac conduction
- SA node spontaneously depolarizes and generates an action potential, which makes the atria contract
- Signal travels to AV node; cells spontaneously depolarize after a short delay
- Signal travels down bundles of His and splits over left/right bundle branches
- Signal travels to Purkinje fibers, ventricles contract
- Heart returns to rest
Where are the SA and AV nodes located?
SA node: upper-right region of right atrium
AV node: lower region of the right atrium
Describe the permeability of cardiac contractile cells during contraction
Depolarizing Phase: Increased Na+ permeability
Initial Repolarizing Phase: Decreased Na+, increased K+
Plateau: Increased Ca2+, decreased K+
Final Repolarizing Phase: Decreased Ca2+, increased K+
Rest: Resting membrane potential
How does EC coupling in cardiomyocytes differ from skeletal muscle?
- Signal arrives from gap junctions
- Ca2+ is released from the SR when Ca2+ enters the sarcoplasm from the ECF (Ca2+-induced Ca2+ release)
- Ca2+ is removed from the sarcoplasm by two methods of active transport: Ca2+ ATPase and the Ca2+-Na+ exchanger (1 Ca2+ ejected to ECF, 3 Na+ brought in)
Why is it necessary to remove Ca2+ from the sarcoplasm?
- Return to rest
- Generate effective depolarizations afterwards
Why is the refractory period important for cardiac cells?
Allows time for the ventricles to empty
What is an electrocardiogram?
A test that measures the heart’s electrical activity, which can indicate issues with heart function
P Wave
SA node fires, atria depolarize/contract
P-Q Interval
delay of cardiac conduction at AV node`
QRS Complex
Ventricular depolarization; atria repolarize here, but the former is much stronger so the latter isn’t evident
T Wave
Ventricular repolarization
Which is faster: ventricular depolarization or ventricular repolarization?
Ventricular depolarization
S-T Segment
Period where ventricles are 100% depolarized and there’s no electrical activity in the heart. Plateau of action potential.
Q-T Segment
time elapsed by ventricular depolarization and ventricular repolarization
Bradycardia
slower-than-normal heart rate
Tachycardia
faster-than-normal heart rate
Systole
Contraction of the heart’s chambers (can describe atria or ventricles) - period of high pressure
Diastole
Relaxation of the heart’s chambers (can describe atria or ventricles) - period of low pressure
Order the steps of the cardiac cycle:
- Atrial Contraction
- Isovolumetric Contraction
- Isovolumetric Ventricular Relaxation
- Passive Ventricular Filling
- Ventricular Ejection
- Passive Ventricular Filling
- Atrial Contraction
- Isovolumetric Contraction
- Ventricular Ejection
- Isovolumetric Ventricular Relaxation
What happens during passive ventricular filling?
- Atria fill with blood from veins
- Atrial pressure exceeds ventricular pressure, so AV valves open + blood passively flows into ventricles
Why are the SL valves closed during passive ventricular filling?
Pressure in the aorta/pulmonary trunk is greater than in the ventricles
What happens during atrial contraction?
- SA node fires, atrial mycoytes depolarize, atria contract (atrial systole)
- Ventricles remain in diastole
- Blood is pushed into ventricles
What is the name for the volume of blood in the ventricles after the end of atrial contraction?
End Diastolic Volume (EDV)
What happens during isovolumetric ventricular contraction?
- Brief period of pressure buildup
- Ventricles depolarize and start systole; atria move into diastole (start of QRS complex)
- All 4 valves are briefly closed
What happens during ventricular ejection?
- Ventricular contraction continues; pressure increases past that in aorta, pulmonary trunk
- SL valves open as ventricular pressure increases
What happens during isovolumetric ventricular relaxation?
- Ventricles repolarize, enter diastole, and begin refilling
- Relaxation of ventricles allows pressure to drop below that of atria
What is the name for the volume of blood in the ventricles after the end of venticular ejection?
End Systolic Volume (ESV)
What is the name for the volume of blood in the ventricles after the end of ventricular ejection?
End Systolic Volume (ESV)
T/F: In a healthy person, blood will flow from the aorta/pulmonary trunk back into the heart
False; this is prevented by the SL valves
Heart sounds
- “Lubb”; louder, longer, heard at IVC (step 3 of cardiac cycle), caused by vibrations as AV valves close
- “Dubb”; softer, shorter, heard at IVR (step 5 of cardiac cycle), caused by vibrations as SL valves close
Stroke Volume
Volume of blood ejected from the ventricles per heartbeat (EDV - ESV)
Ejection Fraction
% of blood pumped with each contraction
EJ = (SV/EDV) * 100%
What is the typical range for ejection fraction? What happens if it falls below this range?
55-75%
Lower EJ can lead to heart failure
What are two factors that regulate stroke volume?
Preload and afterload
Preload
Tension created as the chambers of the heart stretch
Afterload
Pressure from the blood exerted on the heart, which it must overcome in order to eject blood (i.e. preload must be high enough so heart can overcome afterload)
Cardiac Output
Amount of blood ejected per unit time
CO = SV * heart rate
Aortic Stenosis
Narrowing of aortic valve opening due to calcification, which impacts its ability to open and close (can’t fully do either)
Arteriosclerosis
Damage to arterial walls
Atherosclerosis
Buildup of fatty deposits along the walls of arteries
Coronary Artery Diease
Plaque buildup in coronary arteries results in heart not receiving enough blood
Coronary Angiogram
- Dye injected into the body allows for a 3D image of the coronary vessels + the surrounding area
- Red = vessel w/adequate blood flow; blue = poor blood flow
- Green = healthy tissue; no colour = dead tissue
Name one method of treating CAD.
Angioplasty (restoring blood flow) by placing a stent in the artery.
Myocardial Infarction
Heart attack; occurs when blockage in coronary vessel(s) causes the death of the tissue it supplies
- The heart becomes stiff/hard and can’t contract/relax as well
- Other tissues can’t get enough oxygen, so the heart tries to pump more and temporary hypertrophy occurs. However, this can’t supply organs/tissues with enough blood
Name one method of detecting issues with myocardial blood flow.
Molecular imaging - PET and SPECT imaging use radioisotopes to check the heart
What are some benefits of systemic circulation being in parallel?
- Multiple organs and tissues can receive oxygenated blood at the same time
- Blood flow to an organ/tissue is regulated independently from that of other organs/tissues
- Each organ/tissue receives its own (i.e. an adequate) supply of oxygenated blood
T/F: When the papillary muscles contract, they pull on the chordae tendinae and open the AV valves
False; the contraction of the papillary muscles closes the AV valves