Exam 1: Cont. Flashcards
Law of Laplace
Increase in tension will increase force of ventricular contraction
Larger chamber will have to generate more wall tension, consuming more energy and oxygen
Chronotropic
Affects HR
Dromotropic
Affects conduction velocity
Inotropic
Affects strength of contraction
Frank starling law of heart
Within physiologic limits, heart will pump all blood that returns without allowing excessive damming of blood in veins
Increased venous return causes …
- Increased stretch on cardiac muscle fibers
- Increased cross-bridge formation
- Increased calcium influx
- Increased stretch on SA node
Heterometric autoregulation
As cardiac fibers stretched force of contraction increased
Homeometric autoregulation
Increase strength of contraction independent of length change
Stretch on SA node will increase ___ permeability which will increase ___
Ca/Na
HR
Extrinsic influences on HR
ANS
Hormones
Ionic influences
Temperature
Sympathetics, using ____, does what?
NorEpi
Increase HR
+ strength of contraction
+ conduction velocity
Parasympathetics, using ___, does what?
ACTH
- HR
- strength of contraction
- conduction velocity
___ has dominant - influence on resting HR
Parasympathetics
SNS blocked with ___, which is a beta blocker
Propranolol
Parasympathetic effects blocked using ___, which blocks muscarinic receptors
Atropine
Under resting conditions:
____ exerts dominant - effect on HR
____ exerts dominant + effect on strength of contraction
PSNS
SNS
___ accounts for most of SNS effect
Direct innervation of cardiac cells
Indirect effects of SNS due to
Circulating catecholamines (Epi and NorEpi)
Stimulation of left stellate ganglion
Decreased ventricular fibrillation threshold
Prolonged QT interval
Stimulation of right stellate ganglion
Increased ventricular fibrillation threshold
Bainbridge reflex
Stretch on right atrial wall stimulates stretch receptors -> send signals to MO -> + SNS outflow to heart
Bainbridge reflex helps prevent
Damming of blood in heart and central veins
Benzold-Jarisch reflex
Stimulation of sensory endings mainly in ventricles -> reflex via CN X
Benzold-Jarisch reflex effects results in
Hypotension and bradycardia
Benzold-jarisch reflex stimulated by
Occlusion of circumflex Artery
Increase in LVP and LV volumes
Thyroid hormones influence
+ inotropic
+ chronotropic
Increase CO by increasing BMR
Effects of elevated K
Dilation and flaccidity of cardiac muscle
Decreases resting membrane potential
Effect of elevated Ca
Spastic contraction
HR increases about _____ for every degree F elevation in body temperature
10 beats
_____ will increase temporarily but prolonged fever can decrease contractile strength
Contractile strength
Decreased body temp decreases ___ and ___
HR
Strength
Preferred energy substrate
Fatty acids
Last resort energy substrate
Amino acids
75% of NRG heart utilizes is converted to
Heat
EKG measures
Potential difference across surface of myocardium with respect to time
Normal rate of bps
60-80
> 100
Tachycardia
< 50
Bradycardia
If PR interval is greater than .2 sec, it indicates
1st degree AV block
Normal PR interval
.16 sec
P wave
Atrial depolarization
QRS complex
Ventricular depolarization
T wave
Ventricular repolarization
Atrial repolarization is buried in the
QRS complex
Routine EKG consists of 12 leads: 6 in the ___ and 6 in the ____
Frontal plane
Chest (horizontal plane)
Wave of depolarization moving toward + electrode
Increase deflection
Wave of repolarization moving toward + electrode
Decrease deflection
Wave of depolarization moving toward - electrode
Decrease deflection
Wave of repolarization moving toward - electrode
Increase deflection
Lead 1 complementary to
AvF
Lead 2 complementary to
AvL
Lead 3 complementary to
AvR
Infarction preceded by
Ischemia
Sing of ischemia
Inverted T wave
Hypertrophy: axis shifts _____
To side of problem
____ deviation MC in Hypertrophy
L axis deviation
HR order for EKG
300 150 100 75 60 50
PR interval
Time from SA node to entering ventricle
Includes AV nodal delay
1st degree AV block
PR interval greater than .2 sec
Prolonged QT interval
Increased incidence of sudden cardiac death
More likely to develop v fib
Heart rate variability is ___, because it means there is varying autonomic tone
Good
2nd degree AV block
Dropped beat
P wave with no associated QRS complex
3rd degree AV block
No relationship between P waves and QRS complex
Normal QRS complex duration
.06-.08 s
Prolonged QRS complex associated with
Ventricular Hypertrophy
Conduction block in purkinje System
Mean electrical axis
Average direction of ventricular depolarization
Ventricle depolarizes in what direction
Base to apex
Endocardium to epicardium
Normal axis between
-30 to + 105 degrees
Conduction block and hypertrophy shift axis
To side of problem
Left bundle branch block creates
Left axis deviation
____ limits myocardial blood flow, especially in LV
Contraction of cardiac muscle
Left coronary flow peaks at
Onset of diastole
Right coronary flow peaks
Mid systole
Resting myocardium O2 extracting rate
70% (maximal O2 out of perfusing coronary flow)
O2 taken out at rest system wide
25%
O2 taken out during exercise
50%
Depolarization and repolarization waves should be in ___ direction, so QRS and T waves points in ___ direction
Opposite
Same
Ischemia prolongs ___ and delays ____
Depolarization
Repolarization
Ischemia causes depolarization and repolarization waves to be in
Same direction
Damaged cells due to infarction lose ability to
Repolarize
Most frank damage during infarction occurs due to
Reperfusion injury (ROS damage)
Elevated ST segment suggests
Infarction
Released when myocardial necrosis occurs
Troponin
_____ are highly sensitive and specific for cardiac damage
Cardiac troponins T and I