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ANT 3120: Chapter 20 (Phys)
Physiology
120
Anatomy
Undergraduate 1
03/05/2013

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Term
cardiac conduction system
Definition
group of specialized, highly excitable cells that give the heart its rhythmicity
Term
function of cardiac conduction system
Definition
spontaneously generates and conducts action potentials
Term
sinoatrial node (description)
Definition
pacemaker of heart
Term
function of SA node
Definition
spontaneously generates action potentials at a rate of 70 to 80 per minute
Term
SA node spreads action potentials to
Definition
1) cardiac muscle of atria via internodal pathways
2) to AV node via internodal pathways
Term
function of AV node
Definition
receives action potentials from SA node
Term
AV node spreads action potentials to
Definition
AV bundle/Bundle of His after the 110 ms delay
Term
AV bundle (description)
Definition
divides into left and right bundle branches (one per ventricle)
Term
function of AV bundle
Definition
receives action potentials from AV node
Term
AV bundle spreads action potentials to
Definition
Purkinje fibers
Term
function of Purkinje fibers
Definition
receive action potentials from the AV bundle
Term
Purkinje fibers spread action potentials to
Definition
cardiac muscle of the ventricles
Term
ectopic pacemaker (description)
Definition
any part of the heart other than the SA node that generates a rhythm
Term
most common ectopic pacemaker
Definition
AV node
Term
heart rate if AV node is pacemaker
Definition
40 to 60 beats per minute
Term
heart rate if Purkinje fibers are pacemaker
Definition
25 to 45 beats per minute
Term
arrangement of cardiac muscle cells
Definition
arranged in a syncitium
Term
cardiac muscle cells make up
Definition
the bulk of the atrial and ventricular walls
Term
resting Vm of cardiac muscle cell
Definition
-90 mV
Term
EKG (description)
Definition
recording of electrical activity of cardiac muscle
Term
EKG is recorded with
Definition
electrocardiograph
Term
function of standard bipolar limb leads
Definition
measure electrical activity of heart in a frontal plane
Term
(standard bipolar limb lead) Lead I
Definition
measures electrical activity across heart at 0° angle
Term
(standard bipolar limb lead) Lead II
Definition
measures electrical activity across heart at +60° angle
Term
(standard bipolar limb lead) Lead III
Definition
measures electrical activity across heart at +120° angle
Term
augmented unipolar limb leads
Definition
measure electrical activity of the heart in a frontal plane
Term
(augmented unipolar limb leads)aVR
Definition
measures electrical activity across heart at -150° angle
Term
(augmented unipolar limb leads)aVL
Definition
measures electrical activity across heart at -30° angle
Term
(augmented unipolar limb leads)aVF
Definition
measures electrical activity across heart at +90° angle
Term
placement of Lead I
Definition
right arm to left leg
Term
placement of Lead II
Definition
right arm to left leg
Term
placement of Lead III
Definition
left arm to left leg
Term
placement of aVR
Definition
right arm to the joining of left arm and left leg
Term
placement of aVL
Definition
left arm to the joining of left leg and right arm
Term
placement of aVF
Definition
left leg to the joining of right arm and left leg
Term
function of chest leads
Definition
measure the electrical activity of the heart in a transverse plane
Term
leads across chest
Definition
V1 to V6
Term
P wave
Definition
signifies atrial deploarization; normally 80 to 120 msec in duration
Term
QRS complex
Definition
signifies ventricular depolarization; normally 60 to 100 msec in duration
Term
T wave
Definition
signifies ventricular repolarization; normally 160 to 200 msec in duration
Term
PQ interval/PR interval
Definition
from onset of atrial depolarization to onset of ventricular depolarization (P to Q); normally 120 to 200 msec in duration
Term
mean electrical axis
Definition
average of all the instantaneous mean electrical vectors occurring sequentially during depolarization of the ventricles
Term
mean electrical axis is based on
Definition
QRS complexes of limb leads I, II, III
Term
normal value of mean electrical axis
Definition
+59°
Term
arrhythmia
Definition
conditions where electrical activity is irregular
Term
tachycardia
Definition
heart rate above 100 beats per minute
Term
bradycardia
Definition
heart rate below 60 beats per minute
Term
reasons for tachycardia
Definition
elevated body temp, excessive sympathetic stimulation
Term
reasons for bradycardia
Definition
excessive parasympathetic stimulation; athletic heart
Term
first degree heart block
Definition
conduction of action potential is slowed; prolonged PQ interval (greater than 200 msec)
Term
type I second degree heart block
Definition
conduction of action potentials slowed; very prolonged PQ interval and loss of QRS complex from time to time
Term
symptom of Type I second degree heart block
Definition
dizziness
Term
type II second degree heart block
Definition
conduction of action potential is slowed/blocked; very prolonged PQ interval and multiple P waves without QRS complex
Term
symptom of Type II second degree heart block
Definition
slow HR and could need artificial pacemaker
Term
common reason for artificial pacemaker
Definition
third degree heart block
Term
reason for third degree heart block
Definition
heart disease or congenital in nature
Term
third degree heart block
Definition
complete block of action potential conduction; very slow heart rate which leads to inadequate circulation
Term
atrial fibrillation
Definition
block of action potential in atria; AV node activated sporadically
Term
EKG of atrial fibrillation
Definition
no observable P waves and no constant QRS spacing
Term
ventricular fibrillation
Definition
conduction system is disordered
Term
EKG of ventricular fibrillation
Definition
no clear waves
Term
symptom of ventricular fibrillation
Definition
loss of consciousness; death imminent if not remedied
Term
right axis deviation (+90° to +180°)
Definition
hypertrophy of the right side of the heart or damage to left side of the heart
Term
right axis deviation could be due to
Definition
1) pulmonary hypertension
2) pulmonary valve dysfunction
3) heart attack that damages left side
Term
left axis deviation (-30° to -90°)
Definition
hypertrophy of the left side of the heart or damage to right side of the heart
Term
left axis deviation could be due to
Definition
1) systemic hypertension
2) aortic valve dysfunction
3) heart attack that damages right side
4) athletic heart
Term
heart sounds due to
Definition
closing of valves and the collision of blood against them when they do close
Term
opening and closing of valves is dictated by
Definition
pressure changes in the chambers of the heart
Term
valves function to
Definition
allow flow of blood through the heart in only one direction
Term
AV valves open when
Definition
atrial pressure exceeds ventricular pressure
Term
AV valves close when
Definition
ventricular pressure exceeds atrial pressure
Term
semilunar valves open when
Definition
ventricular pressure exceeds pulmonary trunk and aortic pressure
Term
semilunar valves close when
Definition
pulmonary trunk and aortic pressures exceed ventricular pressure
Term
First heart sound (S1)
Definition
closing of AV valves (tricuspid and mitral); longest and loudest sound
Term
2nd heart sound (S2)
Definition
closing of pulmonary and aortic semilunar valves
Term
heart murmur indicates
Definition
turbulent blood flow
Term
stenosis
Definition
narrowing of valves which creates resistance to flow
Term
stenosis murmur heard when
Definition
blood flows through the valve

AV stenosis prior to S1
semilunar stenosis prior to S2
Term
valve insufficiency/regurgitation
Definition
improper closing of valves which causes back flow of blood through valve
Term
valve insufficiency/regurgitation murmur heard when
Definition
valves close

AV insufficiency during S1
semilunar insufficiency during S2
Term
most commonly heard murmur
Definition
mitral valve insufficiency
Term
septal defects cause
Definition
blood flow to be turbulent
Term
cardiac cycle
Definition
events that make up one heart beat
Term
average typical duration of cardiac cycle
Definition
varies from .75 seconds to 1 second
Term
duration of cardiac cycle dictates
Definition
heart rate
Term
heart spends ___ of its time in systole
Definition
1/3
Term
heart spends ___ of its time in diastole
Definition
2/3
Term
atrial systole
Definition
time atria are contracting
Term
ventricular systole
Definition
time the ventricles are contracting
Term
atrial diastole
Definition
time atria are relaxing
Term
ventricular diastole
Definition
time ventricles are relaxing
Term
5 periods of cardiac cycle
Definition
1) isovolumic contraction (systole)
2) period of ejection (systole)
3) isovolumic relaxation (diastole)
4)passive ventricular filling(diastole)
5)active ventricular filling (diastole)
Term
stroke volume
Definition
volume of blood ejected to each great artery (~70mL)
Term
end diastolic volume
Definition
volume of blood in ventricles prior to ejection of blood (~120mL)
Term
ejection fraction
Definition
percentage of blood ejected from each ventricle (55% to 70% is normal)
Term
calculate EF
Definition
EF = (SV)/(EDV) x 100
Term
end diastolc volume
Definition
volume of blood in the ventricles after the stroke volume is ejected
Term
calculate ESV
Definition
(EDV) - (SV)
Term
isovolumic relaxation
Definition
relaxation of ventricles; ventricular pressure decreases below pressure of great arteries
Term
passive ventricular filling
Definition
ventricular pressure decreases further and is now lower than atrial pressure
Term
active ventricular filling
Definition
atria contract and actively fill ventricles with more blood
Term
isovolumic contraction
Definition
ventricles begin to contract; ventricular pressure increases and eventually exceeds atrial pressure
Term
period of ejection
Definition
ventricular pressure increases further and exceeds pressure of great arteries
Term
cardiac output
Definition
volume of blood pumped by either the left or right ventricle in a minute
Term
calculate cardiac output
Definition
CO = SV x HR
Term
inotropic
Definition
something that affects heart contractility and therefore stroke volume
Term
chronotropic
Definition
something that affects heart rate
Term
preload
Definition
volume of blood in the ventricle immediate prior to systole (EDV)
Term
Starling's law of the heart is a relationship between
Definition
preload and heart contractility
Term
afterload
Definition
resistance the ventricle is exposed to when pumping
Term
extrinsic regulation
Definition
1) autonomic nervous system
2) hormones
3) body temperature
Term
vagus nerve (PS) [description]
Definition
primary controller of resting heart rate
Term
vagus nerve innervates
Definition
SA node, AV node, atrial myocardium
Term
influence of vagus nerve
Definition
inhibitory: decreases heart rate (negative chronotropic effect)
Term
cardiac nerve (S) [description]
Definition
primary controller of heart contractility
Term
cardiac nerve innervates
Definition
SA node, AV node, atrial and ventricular myocardium
Term
influence of cardiac nerve
Definition
excitatory: increases heart rate (positive chronotropic effect) and increases heart contractility (positive inotropic effect)
Term
function of epinephrine and norepinephrine
Definition
bind to B-adrenergic receptors
Term
function of T3 and T4
Definition
increase the number of B-adrenergic receptors
Term
body temperature effect on heart rate
Definition
change of 1°C changes heart rate approx. 10 beats per minute
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