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73 Cards in this Set
- Front
- Back
2 major blood vessel circuits in the body
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- Pulmonary circuit: to and from lungs
- Systemic circuit: to and from the rest of the body - Each circuit begins and ends with the heart |
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Types of vessels
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- Arteries (transport blood away from heart)
- Veins (transport blood to the heart) - Capillaries (exchange substances between blood and tissues) |
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List of structures of arteries and veins
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- Tunica intima
- Tunica media - Tunica externa |
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Structures of arteries and veins - Tunica intima
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- Innermost layer
- Endothelial cells and connective tissue with elastic fibers |
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Structures of arteries and veins - Tunica media
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- middle layer
- contains concentric sheets of smooth muscle (vasoconstriction or vasodilation) - collagen fibers connect tunica media to other layers |
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Structures of arteries and veins - Tunica externa
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- outermost layer
- connective tissue sheath with collagen and elastic fibers - Generally thicker in veins - Anchor vessel to surrounding tissues |
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Pathway of blood through the heart
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1) deoxygenated blood is brought in via the superior and inferior vena cava
2) enter right atrium 3) through tricuspid valve 4) enter right ventricle 5) passes through pulmonary semilunar valve 6) through pulmonary trunk 7) to lungs 8) back through pulmonary veins 9) left atrium 10) bicuspid valve 11) left ventricle 12) aortic semilunar valve 13) aorta 14) tissues |
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Name the 3 heart layers
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- Epicardium
- Myocardium - Endocardium |
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Epicardium characteristics
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- Outermost layer, covers the surface of the heart
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Myocardium characteristics
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- Forms atria and ventricles
- Contains cardiac muscle tissue, blood vessels and nerves - Thickest part of the heart (left ventricle has more) |
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Endocardium characteristics
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- Covering the intermost surface of the heart and valves
- Composed of simple squamous epithelial tissue |
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Compare right and left ventricles
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- Right: deoxygenated blood, less muscle
- Left: oxygenated blood, more muscle, larger |
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Heart valve locations
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- Tricuspid valve: right atria
- Bicuspid valve: left atria - Pulmonary semilunar: pulmonary trunk - Aortic semilunar valve: aorta |
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Characteristics of cardiac muscle cells
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- small cell size
- single, centrally located nucleus - Branching interconnections - Intercollated discs |
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What is arteriosclerosis and what does it cause?
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- Thickening or toughening of artery walls
- Causes increased BP - Coronary vessels = CAD - Brain arteries = stroke |
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What is atherosclerosis and causes
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- Most common form of arteriosclerosis
- Often associated with elevated cholesterol - Formation of lipid deposits in tunica media pushing against tunica intima (damage) |
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Coronary artery disease (CAD)
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- partial or complete blockage of coronary circulation
- reduced blood flow to area (coronary ischemia) = lower O2 - Usual cause is atheriosclerosis but can also be from blood clot (thrombus) - Treatment includes a wire mesh tube (stent) to hold vessel open |
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Steps of the cardiac cycle
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1) All four chambers are relaxed
2) Atrial systole (Contraction) - atria contract, filling relaxed ventricles with blood 3) atrial diastole - atria relax 4) ventricular systole #1 (occurs at the same time as #3) - ventricles contract - push AV valves closed - Not enough pressure to open semilunar valves - "Isovolumetric contraction" 5) Ventricular systole #2 - ventricular pressure increases - semilunar valves open - blood leaves ventricles - "ventricular ejection" 6) Ventricular diastole early - ventricles relax - pressure drops - semilunar valves close 7) Isovolumetric relaxtion - blood flows into relaxed atria - AV valves remain closed (all valves closed) 8)Ventricular diastole late - all chambers relaxed - ventricles fill passively to 70% volume - AV valves open |
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Heart sounds
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- S1: "Lubb", start of ventricular contraction and closure of AV valves
- S2: "dupp", closure of semilunar valves - S3: blood flowing into ventricles - S4: atrial contraction ** S3 and S4: very faint, rarely heard in adults |
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What is cardiac output?
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- amount of blood pumped by left ventricle in one minute
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What is stroke volume?
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- amount of blood pumped out of left ventricle during a single heartbeat
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Cardiac output formula
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=Heart rate x stroke volume = CO ml/min
- variations affect output: HR can increase, stroke volume can increase |
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What is the conducting system?
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- A network of specialized cardiac muscle cells responsible for initiating and distributing the stimulus to contract
- Can do on their own (automaticity) |
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Conducting system steps
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1) Sinoatrial node (SA)
- Posterior wall of right atrium - Impulse generated is distributed through other components 2) Internodal pathways - distribute signal to atria on way to ventricles 3) Atrioventricular node (AV) - junction of atria and ventricles - also contains pacemaker cells - of SA node damaged, can maintain lower HR - signal pauses (atria contract) 4) AV bundle and branches - interventricular septum - branches relay signal to ventricles toward heart apex 5) Purkinje fibers - large diameter conducting cells - final part of conduction system that triggers ventricular systole |
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Comparison between cardiac and skeletal contraction
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1) Skeletal:
- action potential is brief - twitch contraction is short - twitches can summate and tetanus can occur 2) Cardiac - action potential is long - contraction period is long - tetanic contractions cannot occur - full contractions and complete relaxation |
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3 stages of cardiac muscle action potential
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1) Rapid depolarization
- voltage gated fast sodium channels open at threshold 2) Plateau - transmembrane potential remains near 0mv - fast sodium channels close - slow calcium channels open allowing calcium influx 3) Repolarization - slow calcium channels close - slow potassium channels open |
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How do autonomic nervous systems affect the heart?
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- Pacemaker cells in the SA and AV nodes cannot maintain a stable resting potential
- Always gradual depolarization leading to threshold (=prepotential or pacemaker potential) |
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Parasympathetic stimulation on the heart
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- Ach open K+ channels
- slows heart rate - slows rate of depolarization - extends duration in reploarization |
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Sympathetic stimulation on the heart
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- Ion channels open
- increases rate of depolarization - shortens duration in repolarization |
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What is bradycardia?
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- HR slower than normal
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What is tachycardia?
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- HR is faster than normal
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Cardio control centers
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1) Cardioinhibitory center: controls the parasympathetic neurons to slow heart rate
2) Cardioacceleratory center: controls the sympathetic neurons to increase heart rate |
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End diastolic volume (EDV)
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- the amount of blood in a ventricle at the end of ventricular diastole
- Right before contraction occurs, end of relaxtion |
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End systolic volume (ESV)
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- The amount of blood left in the ventricle following contraction
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Stroke volume formula
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=EDV - ESV
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Influences on EDV that would affect stroke volume
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- Venous return: amount of venous blood returned per minute
- Filling time: duration of ventricular diastole - Preload: amount of myocardial stretching |
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Influences on ESV that would affect stroke volume
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- Contractility: amount of force produced during a contraction at a given preload
- Afterload: tension necessary for ventricular ejection |
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Increased venous return = __________EDV
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increased
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Decreased venous return = __________EDV
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decreased
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Increased HR = __________EDV
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decreased
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Decreased HR = __________EDV
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increased
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Increased preload = __________EDV
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increased
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Decreased preload = __________EDV
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decreased
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Increased contractility = __________afterload
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increased or decreased
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Increased constriction = __________afterload
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increased
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Increased dilation = __________afterload
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decreased
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Increased preload = __________contractility
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increased
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Decreased preload = __________contractility
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decreased
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Increased afterload = __________EDV = __________SV
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increased; decreased
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Decreased afterload = __________EDV = __________SV
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decreased; increased
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Increased contractility = __________ESV = __________SV
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decreased; increased
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Increased filling time = __________EDV
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increased
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Decreased filling time = __________EDV
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decreased
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What does a ECG do?
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- records electrical activities of the heart from body surface over time
- used to assess performance of: nodes, conduction system, contractile components |
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Sections of ECG reading
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- P Wave: atrial depoloarization
- QRS complex: atrial reploarization and ventricular depolarization - T Wave: ventricular reploarization |
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What is total peripheral resistance?
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- Resistance of entire cardiovascular system
- Must be overcome by sufficient pressure from the heart (amount of force depends on vascular resistance, viscosity, and turbulence) |
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Vascular resisitance
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- Largest component of total peripheral resistance
- Primarily results from friction between blood and vessel walls - Amount of friction depend on vessel length and vessel diameter *increased length = increased resistance *decreased diameter (changes throughout the day) = increased resistance |
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Viscosity
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- Resistance to flow caused by interactions of solutes and suspended materials in a liquid
- Thickness - Increased viscosity = increased resistance |
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Turbulence
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- mixed flow with eddies and swirls
- irregular surfaces such as plaque buildup |
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How does blood flow effect blood pressure?
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Increased blood flow = increased BP
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Pressure grandient
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- difference from one end of vessel to other end
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Where is the highest and lowest average BP
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- Highest: aorta
- Lowest: vena cava |
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How does atrial pressure vary?
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- Rising during ventricular systole
- Declining during ventricular diastole |
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What does capillary exchange involve?
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- Filtration, diffusion and osmosis
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Diffusion characteristics
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- Substances flow from higher to lower concentration
- Large solute/proteins usually do not diffuse - Occurs more rapidly when distances are short, concentration gradient is large, solutes are small - Proteins usually cannot cross except at sinusoids |
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Where does filtration predominate?
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arteriole end
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Capillary hydrostatic pressure (CHP)
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- highest near arteriole
- causes water and small solutes to enter interstitial fluid - decreases along capillary length |
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Blood colloid osmotic pressure (BCOP)
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- increases as filtration occurs
- water leaves capillary and plasma proteins remain |
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When is fluid forced out of the capillary?
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CHP > BCOP
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Net filtration pressure (NFP)
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- The difference between capillary hydrostatic and blood colloid osmotic pressure
- NFP = CHP - BCOP *Positive = filtration *Negative = reabsorption |
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Regulatory pathways of blood pressure
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- Blood flow must match changes in demand for oxygen and nutrients
1) Auto regulation: occurs at local level, no outside influence, in vessels (on their own), vasodilators etc. 2) Central regulation: if autoregulation is ineffective, neural and endocrine control (release of hormones such as ADH etc.) |
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Baroreceptor
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Monitors BP in vessel to maintain homeostasis
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Chemoreceptor
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Measures gas levels (O2, CO2)
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