Cardiovascular System Lecture Flashcards
What makes up the cardiovascular system?
heart, blood vessels, and blood
What is the purpose of the cardiovascular system?
delivery and removal of substances
maintain homeostatis
What is the average number of beats per minute?
75
What is the right side pump? What is the left side?
Right=pulmonary
left= systemic
What is the path of blood in the pulmonary circuit in brief?
R heart -> pulmonary trunk -> pulmonary arteries -> pulmonary arteries -> pulmonary capillaries -> pulmonary veins -> L heart
Function of the fibrous pericardium?
most superficial, protective, restricts the size of the heart
What lies between the parietal and visceral layers and what is it filled with?
pericardial cavity and pericardial fluid
What are the three layers of the heart wall?
epicardium
myocardium
endocardium
What is another name for the epicardium?
visceral serous membrane
Function/structure of the myocardium?
majority of the thickness of the heart wall. Made of muscle tissues (cardiomyocytes) and provides the ability for the heart to contract
Structure/function of the endocardium?
Lines chambers of the heart, made of simple squamous endothelium which provides a smooth surface for blood movement
What are the 4 chambers of the heart?
right atrium, right ventricle, left atrium, left ventricle
What veins supply the right atrium?
Superior and inferior vena cava and coronary sinus
what veins supply the left ventricle?
the right and left pulmonary veins (4)
What are the three types of muscle structures inside the heart and along the heart walls?
trabeculae carneae, pectinate, and papillary muscles
What structures keep the AV valves closed?
chordae tendineae which connect to papillary muscles
List the blood flow through the heart and lungs
R atrium -> tricuspid valve -> R ventricle -> pulmonary semilunar valve -> pulmonary trunk + arteries -> lungs -> pulmonary veins -> left atrium -> bicuspid valve -> left ventricle -> aortic semilunar valve -> aorta
Structure and function of valves
Thin floppy tissue that opens and closes in response to pressure changes. Stop blood from flowing back.
Why does blood flow throughout the heart and lungs?
Pressure gradients
What causes the AV valves to open?
HIgher pressure in the atrium than the ventricles
What causes the SL valves to open?
Higher pressure in the ventricles than the arteries
What causes heart sounds and which valves cause which heart sounds?
The sound is created by valves closing
lub= AV valves closing
dub= SL valves closing
what is the importance of the coronary circuit?
provides blood to the heart tissue
what is an arterial anastomoses
alternate routes to get blood to the same portion of tissue
What two major arteries supply the myocardium with blood?
R and L coronary arteries which branch off the aorta
What is the major vein that removes blood from the myocardium?
coronary sinus
Describe atherosclerosis
Fatty plaques in the coronary artery that reduce blood flow to the myocardium
Describe a myocardial infarction
complete blockage of a coronary artery stopping arterial blood flow to heart tissue. Tissue death is permanent and causes scar tissue that does not contract
What are 6 cardiomyocyte properties
amitotic, uninuclear, striation, high number of mitochondria, high volume of myoglobin, and branching
What type of cell metabolism do cardiomyocytes use?
aerobic cellular respiration
What does the endomysium contain a lot of?
capillaries
Where do cardiomyocytes get their Ca2+?
80% from the sarcoplasmic reticulum
20% from extracellular fluid
What are the two types of cell junctions between cardiomyocytes and what are their functions?
intercalated discs (gap junctions)- conduct electricity and cell-to-cell communication
desmosomes- resist tension on the cells
What percentage of cells in the heart are contractile and what percentage are conductive?
99% contractile
1% conductive
What is the function of the conductive cells? What are some of their features?
Form the conduction system of the heart . They are self-excitable, autorhythmic, and create their own action potentials.
What are the 4 parts of the heart conductive system?
SA (sinoatrial) node, AV (atrioventricular) node, AV (atrioventricular) bundle (Bundle of His), and Purkinje fibers.
How many times a minute on average does each part of the heart conduction system depolarize?
SA node: 60-100x
AV node- 40-60x
AV bundle- 30-40x
Purkinje fibers- 15-20x
where is the SA node located?
upper, posterior, right atrium
Function of the SA node?
Conducts to atria to contract, depolarizes the fastest, and sets sinus rhythm
Function of the AV node?
Delays impulses for about 1 second to allow the atria to finish their contraction before the ventricles contract. It is the only electrical connection between the atria and the ventricles.
When do the lower nodes control sinus rhythm?
Only when higher nodes are not functioning
What are the three steps to a conductive cell action potential?
prepotential, depolarization, and repolarization
Describe the prepotential of conducting cells?
No resting potential, constantly drift towards threshold because of a slow influx of Na+ channels that are opened during hyperpolarization (slow voltage-gated channels).
Describe depolarization in conductive cells
Occurs at -40mv. Ca2+ rushes into the cell (fast voltage-gated channel) and causes depolarization. Rises to +20 mV.
Describe repolarization in conductive cells?
When +20 mV is reached, K+ channels open and K+ leaves the cell causing repolarization.
What is the purpose of depolarization in conductive cells?
To send an electrical signal for the heart to contract (depolarization in contractile cells)
What are the four steps to an action potential in contractile cells?
resting membrane potential, depolarization, plateau, and repolarization
describe depolarization in contractile cells?
-90mV to +30 mV. Caused by fast voltage-gated Na+ channels opening.
describe the plateau of contractile cells?
Slow Ca2+ channels open and Na+ is pumped out. Isoelectric charge. This plateau is the heart holding a contraction.
describe repolarization in contractile cells
Slow Ca2+ channels close and K+ channels open and remove K+ which causes repolarization. K+ channels close and the cell returns to resting membrane potential
Is absolute refractory period longer in cardiac muscle cells or skeletal muscle cells?
cardiac muscle cells
Why are absolute refractory periods longer in cardiac muslce cells?
to hold contractions and to separate contractions and generate enough power to contract hard enough to pump blood
What are the main features of an EKG?
P wave, QRS complex, and T wave
What does an EKG do?
measures the sum total of all the action potentials happening in the heart in a given time
What electrical event happens during the P wave?
depolarization of the atria
What electrical event happens during the P-R segment?
The action potential is held in the AV node
what electrical event happens during the QRS complex?
depolarization of the ventricles and repolarization of the atria
What are the the three isoelectric segments?
P-R, S-T, and T-P segments
What electrical event happens during a T wave?
ventricle repolarization
What is the R-R interval?
time of one cardiac cycle
What mechanical event takes place during the T-P segment?
entire heart diastole
What mechanical event happens during the P wave?
atrial systole
What mechanical event happens during the QRS complex?
atrial diastole and ventricular systole
What mechanical event happens in the S-T segment?
ventricular systole
What mechanical event happens in the T wave?
ventricular diastole
What are the pressure gradients for
T-P segment and P wave
QRS complex
S-T segment
T wave
T-P segment and P wave: Patrium>Pventricle
QRS complex: Pventricle>P atrium
S-T segment: Pventricle>Partery
T wave: Partery>Pventricle
What is the status (open closed) of the valves for each
T-P segment and P wave
QRS complex
S-T segment
T wave
T-P segment and P wave- AV open, SL closed
QRS complex- AV close, SL closed
S-T segment- AV closed, SL open
T wave- AV closed, SL close
What is the overall event happening during the T-P segment?
80% ventricular filling
What is the overall event happening during the P wave?
Ventricular filling the final 20%
What is the overall event happening during the QRS complex?
Isovolumetric contraction of the end-diastolic volume of ~120mL
What is the overall event happening during the the S-T segment?
Blood ejection from the ventricles into the arteries of the ~70mL stroke volume.
What is the overall event happening during the T wave?
Isovolumetric relaxation with end-systolic volume of ~50mL
What is the definition of cardiac output?
The volume of blood pumped by each ventricle per minute
How do you calculate cardiac output?
Heart rate (beats per min) x stroke volume (mL/beat)
What is the average cardiac output for a 150lb subject?
5.25 L/min
What factors can change heart rate?
autonomic nervous system, hormones, ions, and age
What factors can change stroke volume?
preload, contractility, and afterload
Where are the cardioinhibitory and the cardioacceleratory centers located?
medulla oblongata
What is the pathway for the cardioinhibitory center?
medulla oblongata receives impulse that indicts a need for a lower heart rate-> MO activates parasympathetic nervous system-> PSNS innervation of the heart releases ACh @ SA/AV nodes, ACh binds to muscarinic receptors-> K+ outflux channels open in conductive cells -> hyperpolarization of conductive cells-> hyperpolarization increases the time to reach threshold-> slows action potentials-> heart rate slows-> cardiac output decreases
What is the pathway for the cardioacceleratory center?
Medulla oblongata receives stimulus that indicates to increase heart rate-> sympathetic nervous system is activated-> sympathetic innervation to the heart releases norepinephrine-> NE binds to B1 adrenergic receptors-> Ca2+ channels open and rush into the cell-> Ca2+ increases speed of depolarizations-> heart beats faster-> heart rate increases-> increases cardiac output
Which hormones affect heart rates, and what do they do?
epinephrine, norepinephrine, and thyroid. All increase HR and increase CO
Which ions affect heart rate?
Calcium- hyper/hypo calcemia
Potassiam- hyper/hypo kalemia
Sodium- hyper/hypo natriema
What is the average heart rate of a newborn?
120 bpm
How do you calculate stroke volume?
End diastolic volume (EDV)- End systolic volume (ESV)= SV
What are the three factors affecting stroke volume?
Preload, Contractility, and Afterload
Describe preload and the factors that affect it
The amount the cardiac muscles are stretched before contraction. The greater the muscle stretch, the stronger the contraction. When the ventricle is stretched and holds more blood, the contraction is stronger, ejecting more blood. An increase in venous return increases preload. A slow heart increases filling time which increases preload.
What is contractility?
Contractility is the force of the contraction. As contractility increases ESV decreases and SV increases.
What factors increase contractility?
sympathetic stimulation- increased Ca2+ release
hypercalemia- increased calcium, more cross bridges
Epi/NE and thyroid hormones
What factors descrease contractility?
Hypoxia
Acidosis
Hyperkalemia- K+ doesn’t want to leave the cell to cause repolarization, no relaxation
calcium channel blockers- bind to and block calcium channels which reduces the ability to create cross bridges
