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Cardiovascular system transports substances including: (3)
- oxygen and nutrients to cells
- wastes from cells to liver and kidneys
- hormones, immune cells, and clotting proteins to specific target cells
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2 valves of heart
- Atrioventricular
- Semilunar
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Which has thicker wall, left or right ventricle? Why?
Left, b/c has to pump blood to body (right is thinner b/c blood is coming in)
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3 layers of heart wall
Inner:
Middle:
Outer:
Briefly describe each layer
- Endocardium: layer of endothelial cells
- Myocardium: cardiac muscle
- Epicardium: external membrane
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Which are larger, myocardium or skeletal muscle cells?
Skeletal
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Defining properties of myocardium cells (9)
- Small cells
- One nucleus
- Striations (myofilaments)
- Branching cells
- Intercalated disks: gap junctions & desmosomes
- Aerobic muscle
- No cell division after infancy-growth by hypertrophy
- 99% contractile cells
- 1% autorhythmic cells
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What is the importance of gap junctions in myocardium cells?
Cause heart to contract as a unit
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What is the importance of desmosomes of myocardium cells?
Resist stress
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Is the cardiovascular system an open or closed system?
Closed
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Heart capillaries are supplied by coronary arteries that arise from ____. These are specifically for the heart & provide heart w/nutrients.
aorta
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One of the main reasons for heart attack
Blockages in coronary arteries
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Wave of contraction through the myocardium
Heartbeat
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Which contracts first, atria or ventricles?
Atria
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What are the 2 atrioventricular valves?
- Tricuspid valve (right valve) (made of 3 tissues)
- Bicuspid valve (left valve) = mitral valve (made of 2 tissues)
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What are the 2 semilunar valves?
- Aortic valve
- Pulmonary valve
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What are the locations of semilunar valves?
- Aortic valve: b/w left ventricle & aorta
- Pulmonary valve: b/w right ventricle & pulmonary artery
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Series of events in the heart that pump blood
Cardiac cycle
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What the two main periods of the cardiac cycle?
- Systole = ventricle contraction
- Diastole = ventricle relaxation
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Blood flows from ___ pressure to ___ pressure. So the blood in ___ chambers flow to the ___ chambers and the blood flows from ventricles to the ___ or the ____.
- high, low
- atria, ventricles
- ventricles, pulmonary artery or aorta
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What causes AV and semilunar valves of heart to open?
- Pressure gradients:
- AV valves: pressure atria > pressure ventricles
- Semilunar valves: pressure ventricles > pressure arteries
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4 phases of cardiac cycle
- 1.) Ventricular filling
- 2.) Isovolumetric ventricular contraction
- 3.) Ventricular ejection
- 4.) Isovolumetric ventricular relaxation
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2 phases of ventricular filling & what happens
- passive phase: no atria or ventricular contraction
- active phase: atria contract
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1st phase cardiac cycle: Ventricle filling
Pressure atria ____ pressure ventricles
AV valves ___
Passive phase:
Active phase:
- >
- open
- no atria or vent contraction
- atria contract
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2nd phase cardiac cycle: Isovulumetric ventricular contraction
AV and semilunar valves ___
Ventricular pressure ___
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3rd phase cardiac cycle: Ventricular ejection
Semilunar valves ___
open
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4th phase cardiac cycle: Isovolumetric ventricular relaxation
Ventricular pressure ___
AV and semilunar valves ____
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Maximum aortic pressure in cardiac cycle
systolic pressure
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minimum aortic pressure in cardiac cycle
Diastolic pressure
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Mean arterial pressure (MAP) =
DP + [(SP-DP)/3]
(1/3 b/c we spend 1/3 of our time in systole)
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Volume of blood in ventricle at the end of diastole
End-diastolic volume (EDV)
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Volume of blood in ventricle at the end of systole
End-systolic volume (ESV)
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Which phases of cardiac cycle is there no chg in amt of blood in ventricles b/c valves are closed?
2 &4
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Volume of blood ejected by the ventricle each beat
Stroke volume
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Fraction of end-diastolic volume ejected during a heartbeat
Ejection fraction
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Ejection fraction =
SV/EDV
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What causes the sound of the heart?
Turbulent flow when valves close
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Describe first heart sound & what happens
- Soft lubb
- AV valves close simultaneously
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Describe second heart sound & what happens
- Louder dubb
- Semilunar valves close simultaneously
(louder b/c more pressure)
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Ability to generate one's own rhythm
Autorhythmicity
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Heart has conduction system containing autorhythmic cells which help spread excitation through the heart. How can the heart cells do this and what are they called?
- They produce their own action potential spontaneously by depolarizing.
- Pacemaker cells
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Rapidly conduct action potentials initiated by pacemaker cells to myocardium
Conduction fibers
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Commonly called the pacemaker of the heart b/c it sets heart rate
Sinoatrial node
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Where are pacemaker cells located?
Sinoatrial & atrioventricular nodes
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Internodal pathways, Bundle of His, and Purkinje fibers are all ___ of the ___
conduction fibers of the myocardium
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Junctions b/w adjacent myocardial cells
Intercalated disks
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___ are for electrical coupling & spread of excitation b/w cells
Gap junctions
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These stretch to prevent heart celsl from damage when contracting
Desmosomes
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Describe the beginning of spread of excitation in heart
- SA node to AV node
- SA node to right atrium to left atrium (rapid)
(both happen at same time)
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From the AV node, excitation is spread:
from atria to ventricles (slow which allows atria to contract before ventricles)
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Describe excitation of ventricles
Down bundle of His then up Purkinje fibers which contact ventricle contractile cells, causing ventricle to contract from apex up
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In heart, like muscle cells, depolarizations lead to more action potentials and hyperpolarizations lead to fewer action potentials.
T
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Calcium is removed from cytosol, causing troponin and tropomyosin return to position covering myosin binding sites on actin during ____
relaxation of cardiac muscle
- (Calcium release and calcium re-uptake have the
- same roles as they do in skeletal muscle)
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external measure of electrical activity of the heart which can be recorded from electrodes on the skin
electrocardiogram (ECG)
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Pace generated by SA node
Sinus rhythm
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Abnormal ECG rhythms:
Tachycardia:
Bradycardia:
- Fast sinus rhythm
- Slow sinus rhythm
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Loss of coordination of electrical activity of heart, causing rapid death unless corrected
Ventricular fibrillation
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Volume of blood pumped by each ventricle per minute
Cardiac Output
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Cardiac output =
Stroke volume x Heart rate
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Average resting cardiac output = ___ L/min
5
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Average blood volume = __ L
5.5 L
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2 ways in which cardiac output is regulated
- Intrinsic: autoregulation
- Extrinsic: neural & hormonal
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What determines heart rate?
SA node firing rate
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What would the heart rate be if we had no
extrinsic control? ie What is the SA node intrinsic firing rate?
100 beats/min
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HR when parasympathetic system dominates
75 beats/min
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What does sympathetic activity do to SA node
cells?
Activates receptors in SA node, causing an increase in open sodium and Ca channels, causing an increase in rate of spontaneous depolarization, causing increase in HR
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What does parasympathetic activity do to SA node
cells? (vagus nerve)
Activates receptors in SA node, causing opening of K+ channels and closing of Ca channels, causing decrease in rate of spontaneous depolarizations and hyperpolarizing the cell, causing decrease in HR
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What does the autonomic nervous system (both symp & parasymp) do to the AV node?
- Sympathetic: increase conductoin velocity through node
- Parasympathetic: decrease conduction velocity through node
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How to hormones affect heart rate?
- Epinephrine: same effect as symp nervous system
- Glucagon: increases HR
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What extrinsic factors affect stroke volume? In general, what does sympathetic activity do to heart muscle conctractility?
- Hormones (thyroid hormones, insulin, glucagon increase force of contraction) & sympathetic nervous system
- Increases cardiac contractility
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Specifically, what does sympathetic activity do to heart muscle conctractility?
Increases sympathetic activity so increases epinephrine release, strength & rate of contraction, and rate of relaxation
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Pressure in aorta during ejection
Afterload
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What intrinsic factors affect stroke volume?
afterload, end diastolic volume
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How does a higher afterload during intrinsic control affect stroke volume?
Decreases SV
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What is preload?
End-diastolic pressure
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What causes an increased EDV? (3)
- filling time
- atrial pressure
- central venous pressure
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What is the Frank-Starling law?
An increased EDV stretches muscle fibers, so fibers are closer to optimum length, resulting in stronger contraction, which increases SV
(ie An increase in EDV causes SV to increase)
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