191 a Exam #3

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142 Terms

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functions of the CV system
transportation, regulation (pH, temperature, water), protection (platelets, WBCs, blood proteins)
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scientific names for RBC and WBC
RBC \= erythrocytes, WBC \= leukocytes
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Platelets
cell fragments (with no nucleus) that initiate clots and close blood vessel breaks
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what makes up the majority of blood
plasma (mostly water)
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heart COVERINGS from outer to inner
1. fibrous pericardium
2. serous pericardium
(2a. parietal pericardium,
2b. visceral pericardium / epicardium)
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fibrous pericardium
tough, fibrous connective tissue that is the protective outer sac of the pericardium
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serous pericardium
double-walled inner sac of pericardium composed of the parietal and visceral pericardium
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parietal pericardium
outer layer of the serous pericardium
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visceral pericardium (epicardium)
inner layer of serous pericardium sac / outer layer of heart wall; rests ON ORGAN
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pericardial/serous cavity
space between parietal and visceral layers of the serous pericardium containing pericardial/serous fluid; decreases friction as heart moves
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myocardium
thick middle layer of heart wall composed of cardiac muscle; has many blood and lymph capillaries and nerve fibers
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Cardiac muscle
\= rhythmic, involuntary, striated fibers connected in branching 3D networks; contract in ALL-OR-NONE manner
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Endocardium
smooth inner layer of the heart wall composed of endothelium and elastic connective tissue
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pulmonary circuit
carries blood from the heart to lungs to heart again

(starts in RV)
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systemic circuit
carries blood from the heart to whole body to heart

(starts in LV)
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amount of oxygen and CO2 in blood are always \___ of each other?
opposite
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atria
thin-walled upper heart chambers that RECEIVE RETURNING blood
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ventricles
thick-walled lower heart chambers that receive blood from the atria and contract to FORCE BLOOD OUT of the heart into the arteries

(left ventricle is largest with thickest walls)
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septum
solid, wall-like structure that divides the heart into left and right halves, preventing blood from mixing
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interatrial septum
thinner, upper portion of the septum that separates atria
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interventricular septum
lower, thicker portion of the septum that separates ventricles
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atrioventricular valves
valves composed of leaf-like cusps that prevent backflow into the ATRIA; includes the tricuspid and bicuspid (mitral) valve
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semilunar valves
valves composed of deep U-shaped cusps that prevent backflow into the VENTRICLES; includes the pulmonary and aortic valves
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can AV valves be open while semilunar valves are open?
no
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path of blood flow through the heart (starting with right side)
1. coronary sinus and vena cavae
2. RA
3. tricuspid valve
4. RV
5. pulmonary valve
6. pulmonary trunk
7. pulmonary arteries
8. arterioles
9. capillaries
10. venules
11. pulmonary veins
12. LA
13. bicuspid (mitral) valve
14. LV
15. aortic valve
16. aorta (ascending, arch, descending)
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coronary sinus
smaller vein which returns blood from the heart wall into the RA
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Chordae tendineae
strong, fibrous strings that attach to the cusps of AV valves on the ventricular side
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Papillary muscles
muscles that pull on chordae tendineae to prevent AV valve cusps from swinging back into atria
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are AV valves open or closed during ventricular contraction?
closed
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why do heart valves open and close?
Valves close due to PRESSURE DIFFERENCES created by ventricular contractions and relaxations
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what happens right before the AV valves close?
atrial contraction increases atrial pressure to empty remaining blood into ventricles
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mitral valve prolapse (MVP)
one or both cusps of the mitral valve stretch and bulge into the LA during ventricular contraction, causing regurgitation of blood into the LA and heart murmur
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rules regarding pressure
the fuller the chamber (more contents), the higher the pressure

the bigger the chamber (more space), the lower the pressure
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coronary arteries
arteries branching from the aorta that supply oxygenated blood to the walls of the heart
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Cardiac (coronary) veins
veins parallel to coronary arteries that drain blood that has passed through myocardial capillaries; join the coronary sinus to return blood to RA
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Coronary artery disease (CAD) / heart disease
partial or complete blockage of coronary circulation, usually due to coronary atherosclerosis and reduction of blood flow to the myocardium

symptoms: angina pectoris, MI, stroke

risk factors: cholesterol, smoking, hypertension, family history, post-menopausal women, men \>45

\#1 cause of death in the US
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Electrocardiogram (ECG)
records electrical changes (depolarization and repolarization) in the myocardium during the cardiac cycle
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P wave

+ when does contraction occur?
depolarization of the atria (to push out the last bit of blood)

Contraction occurs during following flatline
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QRS complex

+ when does contraction occur?
depolarization of the ventricles (only really shows left because the myocardium is so thick)

Contraction occurs AFTER the peak of the R wave
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T wave
Repolarization of the ventricles

(before relaxation)
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Bradycardia
slow HR < 60 bpm
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Tachycardia
fast HR \> 100 bpm
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Systole
contraction of a heart chamber; increases pressure
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Diastole
relaxation of a heart chamber; decreases pressure
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Cardiac cycle
one complete heartbeat; the coordinated contraction of the heart chambers
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(Atrial/ventricular) Syncytium
mass of merging muscle fibers that act as a unit

*Note: atrial and ventricular syncytium are mostly separated to prevent simultaneous atrial and ventricular contraction
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heart murmur
abnormal heart sound; may be the sound of blood moving back into the LA due to MVP
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"lubb"
blood hits closed AV valves during ventricular CONTRACTION
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"dupp"
blood hits closed pulmonary and aortic valves (snap shut) during ventricular RELAXATION
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automaticity / autorhythmicity
cardiac muscle contracts without neural or hormonal stimulation
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cardiac conduction system definition
system of specialized cardiac muscle that initiates and distributes nerve impulses for contraction; contains few myofibrils because its function isn't contraction
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cardiac conduction system order
1. SA node
2. junctional fibers (internodal fibers)
3. AV node
4. AV bundle/Bundle of His
5. L/R bundle branches
6. Purkinje fibers
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SA node
self-stimulating specialized cardiac muscle tissue that generates the heart's rhythmic contraction; depolarizes fastest

located near opening of superior vena cava beneath the epicardium and continuous with the atrial syncytium
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Junctional (internodal) fibers
cardiac muscle fibers with small diameters that slow and conduct impulses from the SA node to the atrial syncytium, resulting in atrial contraction, AND conduct impulses from the atrial syncytium to the AV node

SA -\> atrial syncytium -\> AV
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AV node
specialized cardiac muscle tissue that slows the spread of impulse to ventricles; depolarizes slower

*Functions as a secondary (but slower) pacemaker if SA node fails

located in inferior portion of interatrial septum just beneath the epicardium
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AV bundle / Bundle of His
group of large fibers forming the only electrical connection between the atria and ventricles
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L/R bundle branches
division of AV bundle fibers (beginning at the upper part of the interventricular septum) that deliver impulses to Purkinje fibers or directly to papillary muscles

lies between the endocardium

*left branch is larger because it supplies the larger left ventricle
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Purkinje fibers
division of bundle branches that spread from the interventricular septum into papillary muscles and from the apex to the base of the heart

their branches are continuous with cardiac muscle fibers
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Why does the heart contract in a twisting motion?
Ventricular fibers are arranged in irregular whirls
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intercalated discs
points of connection between cardiac muscle fibers that allow impulses to travel from cell to cell
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gap junctions
relay stations at intercalated discs that transmit depolarization to the next cardiac muscle fiber
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Autonomic nervous system (ANS)
part of the peripheral nervous system with nerves that innervate the viscera; associated with involuntary activities; maintains homeostasis
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Sympathetic nervous system
o readies the body to expend energy ("fight or flight"); secretes NE and E, which increase HR and cardiac muscle cell metabolism, strengthening contraction and increasing stroke volume
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PARAsympathetic nervous system
(like the "brakes") most active at REST; secretes Ach, which decreases HR by hyper-polarization and inhibition of cells, weakening contraction and decreasing stroke volume
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cardiac output
amount of blood pumped by each ventricle per minute (mL/min), indicating blood flow to peripheral tissues; CO \= HR x SV
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stroke volume
the amount of blood pushed out of the ventricles per contraction (mL/beat); SV \= EDV - ESV

*most important factor to cardiac output
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End diastolic volume (EDV)
how full the ventricles are at the end of diastole
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End systolic volume (ESV)
how much blood remains in the ventricles at the end of systole
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3 purposes of CV regulation
ensure that changes in blood flow occur
(1) at right time,
(2) in right area,
(3) without drastically changing BP or flow to vital organs
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regulation of cardiac output
Extrinsic regulation:
(HR, indirectly affects SV)
- ANS: cardiac center sends sympathetic or parasympathetic impulses
- hormones: mimic sympathetic impulses

Intrinsic regulation:
(SV)
- Starling's law & EDV/ESV
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What 3 things control stroke volume?
preload, contractility, afterload
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preload
stretch prior to contraction; depends on fill time and venous return
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contractility
strength of myocardial contraction
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afterload
BP in the pulmonary trunk and aorta that must be EXCEEDED before blood can be ejected from ventricles


*more afterload \= less SV because less blood leaves the heart
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Blood vessel pathway from ventricles to atria
1. ventricles
2. arteries
3. arterioles
4. capillaries
5. venules
6. veins
7. atria
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artieries
strong, elastic vessels that carry blood away from the ventricles under high pressure
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arterioles
thinner, muscular branches of arteries with elastic-recoil capability; regulate blood flow from arteries into capillaries
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Capillaries
thinnest blood vessels that connect the smallest arterioles and venules; where exchange occurs
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Venules
non-elastic, microscopic vessels that continue from capillaries; initially lack muscular tunica media in smallest venules
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Veins
non-elastic, larger vessels that collect blood and return it to the heart
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walls of arteries and veins (small to big)
1. tunica interna/intima
2. tunica media
3. tunica externa/adventitia
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tunica interna/intima
inner wall of blood vessels composed of smooth endothelium that prevents clots; has elastic basement membrane of collagen and outer internal elastic lamina layer with small pores to allow for diffusion between walls
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Tunica media
middle wall of blood vessels composed of smooth muscle and a thick layer of elastic connective tissue; regulates diameter of the lumen
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Tunica externa/adventitia
outer wall of blood vessels composed of a thin layer of irregularly organized elastic and collagen fibers; protects blood vessel and attaches it to surrounding tissue
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Elastic arteries
largest arteries (e.g. aorta) that are most elastic to transport a lot of blood; their tunica media is lined with elastic lamellae
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Muscular arteries
medium-sized arteries that are less elastic but more muscular to distribute blood; maintain pressure by maintaining vascular tone and do not have recoil capability
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Continuous capillaries
endothelial cells form a continuous tube with intercellular gaps through which exchange occurs
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Fenestrated capillaries
endothelial cells have many fenestrations (pores) through which exchange occurs
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Sinusoids
larger capillaries with very large fenestrations and intercellular gaps through which exchange occurs
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Autonomic regulation of blood vessel diameter
*ONLY SYMPATHETIC INNERVATION

vasomotor center controls vasoconstriction and dilation
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Vasomotor fibers
sympathetic innervation of smooth muscle in arteries, arterioles, veins, and venules

- increased sympathetic stimulation (more NE/E) -\> constriction
- decreased sympathetic stimulation (less NE/E) -\> dilation
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precapillary sphincters
smooth muscles encircling capillary entrances that regulate blood distribution, routing oxygenated blood to different parts of the body
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diffusion
substances move across a semi-permeable membrane down the concentration gradient
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filtration
greater hydrostatic pressure on one side of the membrane forces molecules through to the other side, often separating solids from liquids
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osmosis
blood pressure is greater within the vessel than outside it, forcing water across a selectively-permeable membrane while larger molecules remain inside
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veins vs. arteries
- Arteries: smaller lumen, thickest walls because contents are under highest pressure, so the vessels are more muscular and elastic

- Veins: larger lumen, thinner walls because contents are under lower pressure, so the vessels are less muscular and elastic. Contain semilunar valves
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How is blood flow maintained in veins?
- valves support one-way flow and distribute weight of blood

-venoconstriction, skeletal contraction, and respiratory movements increase pressure
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blood pressure
the force blood exerts against the inner walls of blood vessels (usually arteries)
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why does BP decrease further away from the heart?
distance from pump + peripheral resistance
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systolic pressure
maximum pressure in the arteries as a result of ventricular systole