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155 Cards in this Set

  • Front
  • Back
tissue that makes pericardial fluid?
mesothelium (serous membrane]
actin fibers?
myosin fibers?
cardiac muscle cells have?
gap junctions

y shaped
intercalated disc resistance?
1/400 the resistance of the cell membrane
The ________ are the foundations of intercalated discs
gap junctions
gap junctions are
Transmembrane protiens, hydrophillic channels
Resting membrane potential of cardiac muscle is _____ millivolts
Action potential is ____ millivolts
-85 to -95

Plateau lasts _____ sec in ventricular muscle (much longer than skeletal muscle)
~0.2 -0.3
Speed and pressure are _____ through the AV valves
ECF Ca is stored in the?
SR (sarco=muscle)
T-tubules store?
_______ help hold it in.
Results of Action Potential
Ca++ release from sarcoplasmic reticulum.
Ca++ release from T- tubules, which are large, are a very important source of Ca++.
T-tubule Ca++ depends strongly on extracellular Ca++ concentration.
Mucopolysaccharides bind Ca++.
Cardiac Cycle
Systole - muscle is stimulated by action potential and is contracting
Diastole - muscle is reestablishing Na+/K+/Ca++ gradient and is relaxing
EKG - P - atrial depol QRS - Ventricular depol,atrial repol T - ventricular repolarization
In the beginning of diastole, muscle fibers are ________
EKG representation
P - atrial depolarization wave QRS - Ventricular depol with atrial repol superimposed
T - ventricular repolarization
diastole occurances
Diastole - muscle reestablishing Na+/K+/Ca++ gradient and is relaxing
systole occurances
Systole - muscle stimulated by action potential and contracting
Refractory Period
During this time cardiac muscle tissue cannot be re-excited
Lasts 0.25-0.30 sec in ventricles
Lasts 0.15 sec in atria
Cardiac muscle has a _______ refractory period than other muscle types
Excess ECF K+
lowers potential across the membrane and lessens likelihood of depolarization
causes dilation
decreases contractility
causes arrhythmias and fibrillation
slows rate
increases of 2-3x normal can block A-V bundle and cause death
Excess ECF Ca++
causes spastic contraction
opposite effects of K +
Atrial pressure waves
a-wave - atrial contraction c-wave - ventricular contraction (A-V valves bulge) v-wave - flow of blood into atria
Ventricular systole
A-V valves close (ventricular press > atrial press)
Aortic valve opens
Ejection phase
Aortic valve closes
Aortic pressure decreases slowly during diastole because of [2]
the elasticity of the aorta
And blood (and pressure) speading through the arterial lines.
Valvular Functions
To prevent back-flow.
Chordae tendineae are attached to A-V valves.
Papillary muscle, attached to chordae tendineae, contract during systole and help prevent back-flow.
Because of smaller opening, velocity through aortic and pulmonary valves exceed that through the A-V valves.
Work output is affected by “preload” (end- diastolic pressure) and “afterload” (aortic pressure).
Sympathetic & Parasympathetic
Sympathetic stimulation causes increased HR + increased contractility with HR = 180-200 and C.O. = 15-20 L/min.

Parasympathetic stimulation decreases HR markedly and decreases cardiac contractility slightly. Vagal fibers go mainly to atria.(SA/AV)

Fast heart rate (tachycardia) can decrease C.O. because there is not enough time for heart to fill during diastole.

Sym-rate, contactility, irritability
SA nodes
Acts as pacemaker because membrane leaks Na+ and membrane potential is -55 to -60mV
When membrane potential reaches -40 mV, slow Ca++ channels open causing action potential.
After 100-150 msec Ca++ channels close and K+channels open more, returning membrane potential to -55mV.
Internodal Pathways
Transmit cardiac impulse throughout atria
Anterior, middle, and posterior internodal pathways
Anterior interatrial band carries impulses to left atrium.
Delay AV node---
Delay AV bundle--
Delay AV node---0.09 sec.
Delay AV bundle--0.04 sec.

Most delay is in A-V node
A-V Bundles
Normally one-way conduction through the bundles
The only conducting path between atria and ventricles is A-V node and A-V bundle
Divides into left and right bundles
Transmission time between A-V bundles and last of ventricular fibers is 0.06 second (QRS time)
Discharge rates
Normal rate of discharge in sinus node is 70-80/min.; A-V node - 40-60/min.; Purkinje fibers - 15-40/min.
Sinus node is pacemaker because of its faster discharge rate
Time of Arrival of Cardiac Impulse
Main Arrival Times
S-A Node 0.00 sec
A-V Node 0.03 sec A-V Bundle 0.12 sec Ventricular
Septum 0.16 sec
Internodal Pathways
Transmit cardiac impulse throughout atria
Anterior, middle, and posterior internodal pathways
Anterior interatrial band carries impulses to left atrium.
Delay in pickup of the heart beat is the _______ syndrome. New pacemaker is in A-V node or penetrating part of A-V bundle.
Parasympathetic effects
Parasympathetic (vagal) nerves, which release acetylcholine at their endings, innervate S-A node and A-V junctional fibers proximal to A-V node.
Causes hyperpolarization because of increased K+ permeability in response to acetylcholine.
This causes decreased transmission of impulses maybe temporarily stopping heart rate.
Ventricular escape occurs
Sympathetic effects
Releases norepinephrine at sympathetic ending
Causes increased sinus node discharge
Increases rate of conduction of impulse
Increases force of contraction in atria and ventricles
what interval appromimates the time of ventricular contraction?
is potential recorded when the ventricular muscle is either completely depolarized or repolarized?
Einthoven’s law
Sum of leads I+III always equals the potential of lead II
Bipolar means that
the EKG is recorded from two electrodes on the body (which is really a bag of salt water
Left arm is _______mv with respect to the average of the rest of the body
Rt arm is _____mv, so lead I demonstrates a positive potential of _____mv

Lead one
The negative terminal of the electrocardiogram is connected to the right arm, and the positive terminal is connected to the left arm
Lead II
The negative terminal of the electrocardiogram is connected to the right arm, and the positive terminal is connected to the left leg.
Lead III
The negative terminal of the electrocardiogram is connected to the left arm, and the positive terminal is connected to the left leg.
Einthoven’s Law states that
the electrical potential of any limb equals the sum of the other two (+ and - signs of leads must be observed).

example If lead I = 1.0 mV, Lead III = 0.5 mV, then Lead II = 1.0 + 0.5 = 1.5 mV
heart surface is close to these leads
records potential of the cardiac musculature right under what leads?
tiny irregularities in the ventricular surface (particularly the anterior wall), will show up in which leads?
V1 and V2 are usually negative because the electrode is nearer the “base” (top) of the heart. As depolarization of the vents occurs, movement is away from the top.

Vice versa for the bottom leads
Augmented Unipolar Limb Leads [3]
Augmented unipolar leads measure what?
resistances in the body
For aVR the + electrode is the _______ arm, and the - electrode is the _____ arm + _____ leg
right arm

left arm + left leg
aVL + electrode is _____ arm.
aVF + electrode is ______ foot.
lead 1
right arm, left arm
lead 2
right arm, left leg
lead 3
left arm, left leg
right arm
left arm
left leg
4th ICS right and left of sternum


5th ICS


v5 mid axillary
The current in the heart flows from the area of depolarization to the polarized areas, and the electrical potential generated can be represented by a vector, with the arrowhead pointing in the _______ direction.
The length of the vector is proportional to the?
voltage of the potential.
The generated potential at any instant can be represented by?
an instantaneous mean vector.
The normal mean QRS vector is?
59 degrees
during depolarization, current flows downward from the base to the apex, from ________ to _______?
negative to positive
aVR+ axis?
aVL+ axis
lead 1+ axis
lead 2+ axis
lead 3+ axis
When the vector representing the mean direct current flow in the heart is perpendicular to the axis of one of the bipolar limb leads, the voltage recorded in the electrocardiogram in this lead will be?
very low.
When the vector has approximately the same direction as the axis of one of the bipolar limb leads, what happens?
nearly the entire voltage will be recorded in this lead.
Voltages are measured form the peak of __ to the bottom of ___
peak of R to the bottom of S
Lead ______ should be largest voltage when compared to I and III when the mean vector is 59o
First area to repolarize is?
near the apex of the heart
Last areas, in general, to depolarize are the _____ to repolarize.
The P wave should give a + vector in which leads?
leads I, II, and III
vector is largest when?
When half of the ventricle is depolarized,
The mean electrical axis averaged over the entire period of depolarization is?
axis deviations are caused by
Changes in heart position
left shift caused by expiration
lying down
excess abdominal fat pushing up on diaphragm.
left ventr. hypertrophy.
Hypertrophy of left ventricle (left axis shift) caused by?
hypertension, aortic stenosis or aortic regurgitation causes slightly prolonged QRS and high voltage.
Hypertrophy of right ventricle (right axis shift) caused by
pulmonary hypertension, pulmonary valve stenosis, interventricular septal defect. All cause slightly prolonged QRS and high voltage.
For various reasons, one ventricle may become hypertrophied. If it does, depolarization through that vent will be _______ and shift the axis toward that side.
left bundle branch block causes ______ axis shift because right ventricle depolarizes much faster than left ventricle. QRS complex is prolonged. This differentiates Bundle branch block from hypertrophy
If sum of voltages of Leads I, II &III is greater than ______ this is considered to be a high voltage EKG.
4 mV,
Usually, total voltages vary between?
0.5 and 2.0 mV
Increased voltages in standard limb leads most often caused by?
increased ventricular muscle mass (hypertension, marathon runner).
Decreased voltages in standard limb leads
Cardiac muscle abnormalities (old infarcts causing decreased muscle mass and scaring , low voltage EKG, and prolonged QRS).
Conditions surrounding heart (fluid in pericardium, pleural effusions, emphysema) short circuits the voltage and it’s dissipated throughout the body.
Anterior-posterior rotation of apex of heart.
Prolonged QRS
Cause is prolonged conduction of cardiac impulse through ventricles.
Normal QRS = 0.06 - 0.08 sec.
One cause is cardiac hypertrophy.
One cause is a Purkinje system block.
If QRS exceeds 0.12 sec, usual cause is conduction block.
Unusual QRS can be caused by...
local conduction blocks which may cause multiple QRS peaks. Lead III esp. shows double Rs in ventricles or areas firing at different times d.t. failure of Purkinjes
current of injury
J point is not on the same line as T-P interval.
Indicates injury

ischemic tissue delivers current
Current of injury
Damaged cardiac muscle remains partially or totally depolarized all the time.
Current flows between damaged depolarized tissue and ‘normal’ polarized cardiac cells all the time
Injured muscle emits negative charges throughout each heart beat.
Causes of current of injury: (1) local ischemia (most common), (2) mechanical trauma, (3) infection.
current of injury
Under normal conditions, the J point is the junction of QRS complex and ST segment.
Under normal conditions, PR segment is considered the baseline for the entire tracing.
Axis of the current of injury
At the end of the S wave the ventricles are fully depolarized. This is the J point.
The difference between the J point and the T-P segment is the current of injury.
Plot the voltages of the current of injury on the coordinates of the three leads to determine the electrical axis.
The negative end of the vector originates in the injured or ischemic area.
Anterior and posterior wall infarctions
Whether the current of injury comes from the anterior or posterior wall of the heart is determined by the chest leads.
If the current of injury in the chest lead is negative, the chest lead is in an area of negative potential which indicates an anterior lesion.
A positive current of injury in the chest lead indicates a ______ lesion.
The ____ segment shows a current of injury following acute coronary thrombosis.
Ventricular repolarization usually occurs in the opposite direction as depolarization which causes...
an upright T
Prolongation of repolarization may change the...
T wave axis.
T wave abnormalities-causes
Left bundle branch block causes a late depolarization and thus a late repolarization of the left ventricle.

(Just after right ventricle is
repolarized and left is still depolarizing. This gives right
axis deviation and an inverted
T wave in lead I.)
Mild ischemia particularly in the apex of the heart prevents apex from repolarizing first. Thus, the T wave inverts.
Digitalis toxicity prolongs depolarization in certain parts of the heart and can cause a...
biphasic T wave.
caues of arrythmias...[5]
Abnormal rhythmicity of the pacemaker
Shift of pacemaker from sinus node
Blocks at different points in the transmission of the cardiac impulse
Abnormal pathways of transmission in the heart
Spontaneous generation of abnormal impulses from any part of the heart
MI diagnosed by...
Diagnosed by high levels of creatine phosphate (CPK) & lactate dehydrogenase (LDH)
Tachycardia caused by...
Caused by (1) increased body temperature, (2) sympathetic stimulation (such as from loss of blood and the reflex stimulation of the heart), and (3) toxic conditions of the heart
carotid sinus syndrome?
super sensitive receptors in the sinus that increase Ach release
Impulses through A-V node and A-V bundle (bundle of His) are slowed down or blocked due to:[4]
(1) Ischemia of A-V nodal or A-V bundle fibers (can be caused by coronary ischemia)
(2) Compression of A-V bundle (by scar tissue or calcified tissue)
(3) A-V nodal or A-V bundle inflammation myocarditis, diphtheria, rheumatic fever
(4) Excessive vagal stimulation
First degree block is a ______, not an actual block
Ventricles stop contracting during initial total AV block for 5-30 sec because of...
overdrive suppression
Incomplete intraventricular block-
Impulse is sometimes blocked and sometimes not in peripheral portions of Purkinje system resulting in abnormal QRS waves. Purkinje can’t fire during its refractory phase and misses a beat
can be caused by....
Can be caused by ischemia, myocarditis, and digitalis toxicity
Causes of ectopic foci are:
(1) Local areas of ischemia
(2) Calcified plaques
(3) Toxic irritation of A-V node, Purkinje system or myocardium by drugs, nicotine or caffeine
QRS voltage is high in PVC's because...
QRS voltage is high because one side depolarizes ahead of the other.
PVC/s can be caused by...
Caused by cigarettes, coffee, and lack of sleep
PSVT can be stopped with...
Can be stopped with a vagal reflex or quinidine or procainimide

P wave is inverted if origin is near A-V node
VF causes...
If one section of ventricle can get through refractory stages before adjacent sections complete their cycle
If pathway is long (dilated heart)
If conduction velocity is slowed (blockade of Purkinje system, ischemia of muscle, and high K+ levels)
If refractory period is shortened (epinephrine)
afib most frequent cause
Most frequent cause is atrial enlargement due to A-V valve dysfunction
This causes a long pathway of conduction which is favorable for circus movements.
Efficiency of ventricular pumping is decreased 20 - 30 percent. Poor V filling.
Irregular, fast heart rate occurs because of irregular arrival of cardiac impulse at the A-V node.
arrest ussually occurs because...
Usually occurs due to hypoxic conditions in the heart which prevents muscle and conductive fibers from maintaining their electrolyte gradients
No spontaneous rhythm
During deep anesthesia
Resulting from hypoxia
Can respond to CPR
Physical characteristics of the circulation: [4]
distribution of blood volume
total cross sectional area
blood pressure
Reasons for circulation in the first place…[3]
Transporting nutrients to the tissues
Transporting waste products away from the tissues
Transporting hormones
The Circulatory System is Composed of
the Systemic and Cardiopulmonary Circulation
And veins’ volume is about __ that of arteries
Velocity of Blood Flow is Greatest in the?

Aorta >Arterioles > Small veins >Capillaries
Blood flow to tissues is controlled in relation to
tissue needs, locally arteriole & sphincter constriction
Cardiac output is mainly controlled by
local tissue flow
Arterial pressure is controlled independent of either local blood flow control or cardiac output control. It is controlled by
changes in C.O., rate, contraction of venous reservoirs, contraction of arterioles, and , long term, by kidneys.
Relationship between Pressure, Flow, and Resistance
Flow (Q) through a blood vessel is determined by:
1) The pressure difference (DP) between the two ends of the vessel
2) Resistance (R) of the vessel
Causes of turbulent blood flow:
high velocities
sharp turns in the vessel
rough surfaces in the vessle
rapid narrowing of blood vessels
Laminar flow is _____, whereas turbulent flow tend to cause murmurs.
Blood Pressure
Blood pressure is the force exerted by the blood against any unit area of vessel wall.
Measured in millimeters of mercury (mmHg). A pressure of 100 mmHg means the force of blood was sufficient to push a column of mercury 100mm high.
Low pressures are sometimes reported in units of mm of water.
1mmHg = 13.6 mm of water
Resistance is
the impediment to blood flow in a vessel.
Resistance can be calculated by dividing the pressure difference between two points in a vessel by the vessel blood flow
Peripheral vascular resistance = blood pumped out of the heart every second. It averages 100mls. PVR
Heart generates about 100 mm Hg pressure.
Resistance of the entire systemic circulation is 100ml/100mmHg or 1PRU – peripheral resistance unit.
If all the vessels constrict, PRU can be as high as 4. In shock PRU can drop to 0.2
Pulmonary pressure: Mean pulm art press = 16mm Hg. Mean left atrial press = 2mm Hg. Net pulm press = 14mm Hg.
C.O = 100 ml / sec. Pulm vasc resistance = 0.14PRU about 1/7th of the systemic resistance
Conductance is how well a vessel conducts. Exact opposite of resistance
Conductance is a measure of the blood flow through a vessel for a given pressure difference.
Poiseulle’s Law = Q =_pDPr4
Conductance = 1____
Poiseuille's law
concerns the voluminal laminar stationary flow of an incompressible uniform viscous liquid (so-called Newtonian fluid) through a cylindrical tube with constant circular cross-section. It can be successfully applied to blood flow in capillaries and veins, to air flow in lung alveoli, for the flow through a drinking straw or through a hypodermic needle
For any given pressure, blood flows in _________ amounts through parallel structures.
far greater
Brain, kidney, muscle, G.I, skin and coronary are arranged in parallel. So, removal of a parallel tissue – like a kidney, or any amputation – reduces conductance and increases resistance
Conductance is very sensitive to change in ________ of vessel.
The conductance of a vessel increases in proportion to the fourth power of the radius.
The _______ power law makes it easily possible for arterioles to turn off or on blood flow to an area of tissues
Blood viscosity is _____ that of water
3 x
Vascular Distensibility
Vascular Distensibility is the fractional increase in volume for each mmHg rise in pressure
Veins are 8 times more distensible than arteries
Veins provide a reservoir function
Pulmonary arteries are relatively distensible and under much lower pressures than art.s. They are about 6 x as distensible as systemic art.s
Vascular Capacitance (or compliance)
Vascular capacitance is the total quantity of blood that can be stored in a given portion of the circulation for each mmHg.
Veins are more compliant and more distensible than arteries
Capacitance = Distensibility x volume
The capacitance of veins is 24 times that of arteries.
Volume-pressure Relationships in Circulation

Veins sequester blood
Veins are a big source of volume and therefore affect preload and CO
Any given change in volume within the arterial tree results in larger increases in pressure than in veins.
When veins are constricted, large quantities of blood are transferred to the heart, thereby increasing pre-load and cardiac output
Damping at the peripheral arteries
The intensity of pulsations becomes progressively less in the smaller arteries.

The degree of damping is proportional to the resistance of small vessels and arterioles and the compliance of the larger vessels
Factors Affecting Pulse Pressure
Stroke volume—increases in stroke volume increase pulse pressure,
conversely decreases in stroke volume decrease pulse pressure.

Arterial compliance—decreases in compliance increases pulse pressure;
increases in compliance decrease pulse pressure.
Abnormal Pressure Pulse Contour caused by? [3]
Arteriosclerosis–decreases compliance of arterial tree, thus leading to increase in pulse pressure.
Patent ductus arteriosus–associated with low diastolic pressure and high systolic pressure, net result is very high pulse pressure.
Aortic regurgitation–condition associated with backward flow of blood through the aortic valve. Low diastolic and high systolic pressure leads to high pulse pressure.
Resistance x compliance = ________
degree of damping
Measurement of Systolic and Diastolic Pressures
Auscultatory method is the most commonly used method for measuring systolic and diastolic pressures.
When cuff pressure reaches systolic pressure, one begins to hear tapping sounds in the antecubital artery; as the cuff pressure reaches diastolic pressure, one hears muffled sounds and then Korotkoff sounds disappear.
Mean arterial pressure can be estimated by adding 40% of systolic pressure to 60% of diastolic pressure.
Blood Reservoir Function of Veins
60% of blood is in veins
Under various physiological conditions, blood is transferred into arterial system to maintain arterial pressure.
The spleen, liver, large abdominal veins, and the venous plexus also serve as reservoirs.
Spleen also serves as a special reservoir for red blood cells.
Central Venous Pressure
Pressure in the right atrium is called central venous pressure.
Right atrial pressure is determined by the balance of the heart pumping blood out of the right atrium and flow of blood from the large veins into the right atrium.
Central venous pressure is normally 0 mmHg, but can be as high as 20-30 mmHg
Factors affecting central venous pressure
Right atrial pressure (RAP) is regulated by a balance between the ability of the heart to pump blood out of the atrium and the rate of blood flowing into the atrium from peripheral veins.
Factors that increase RAP:
-increased blood volume
-increased venous tone
- dilation of arterioles (blood pools in the periphery and fills the veins
-decreased cardiac function
Venous Pressure in the Body
Compressional factors tend to cause resistance to flow in large peripheral veins.

Increases in right atrial pressure causes blood to back up into the venous system thereby increasing venous pressures.

Abdominal pressures tend to increase venous pressures in the legs.
Venous Valves and “Venous Pump”
The venous valves and pump maintain a relatively low venous pressure in the legs.
Faulty venous valves lead to varicose