Cardio Lec 5 Flashcards
During re-polarization you have to put __ away
calcium
How is calcium put away?
active transporter puts it back in SR
Muscle cannot relax until __ & why
end of plateau phase bc you need to put calcium away
Digitalis
used to treat severe heart failure
What does digitalis do
inhibits Na/K pump -> Na accumulates in cell
The more calcium
the more forceful the contraction bc you get more actin & myosin interactions
What happens when Na accumulates in the cell
Na/K EXCHANGER will pump Na out in exchng for Ca in -> heart contracts more forcefully (pos. ionotropic agents)
Positive ionotropic agent
drugs that cause a more forceful contraction
Tetanization
when muscle stimulated so rapidly that theres no time for it to relax STAYS CONTRACTED -> muscle fatigues quickly bc using available enegy
Is tetanization favorable for cardiac muscle?
no -> CO would be 0 bc heart would stay contracted & wouldnt be able to fill AND bc it would fatigue
How does the heart not tetanize?
by having long absolute refractory periods heart wouldn’t respond to another stimulus bc wouldn’t be able to fire another action potential
How does tetanization occur?
by firing repetitive action potentials
T/F: Perkinje fibers have to spread impulses through ventricular myocytes very RAPIDLY, but if left to pace heart on their own fire action potentials infrequently -> lower hr
T
Signal gets delayed at the __, because
AV node bc it allows ventricles time to fill
EKG records
electrical activity of heart (ALL action potentials of ALL cells of heart)
T/F: EKG measures valve tension
F
P wave represents
atrial depolarization -> atrial contraction
Is it possible to have another contraction come in prior to relaxation occurring?
no
When is absolute refractory period over?
after heart has relaxed so you cant tetanize as a result
QRS com
ventricular depolarization -> ventricular contraction & atrial repolarization
T wave
ventricular repolarization -> relaxation
What do the waves show?
electrical activity
You have to ___ before you can contract, & ___ before you can relax
depolarize; repolarize
SA node spreads the wave of ___ through the atria
depolarization (causes P wave)
If P wave is missing, indicates
no SA node activity bc SA node sends wave of depolarization
PVC’s on their own are not problematic
T
In ventricular fibrillation heart has no
coordinated depolarization & no ventricular output
Heart block
missing qrs complexes & t-waves so AV node blocked in some instances
When does the AV valve close
beginning of ventricular systole/contraction
In an EKG when do you heart 1st heart sound
peak of R wave (where ventricular contraction begins)
In an EKG when do you heart 2nd heart sound
when semilunar valves close (when ventricular repolarization/relaxation begins) shortly after T wave
Bradycardia
hr < 60 bpm
Is a hr < 60 bpm always abnormal?
no; norm in athletes or if in good shape
Tachycardia
PERSISTENT hr > 100 bpm at rest
Is tachycardia always abnormal?
no; if doing exercise its norm
Tachycardia can result in an
ectopic foci
If tachycardia originates in atria, called
supraventricular (SVT) MOST ARE BENIGN
If tachycardia originates in ventricles, called
(V Tach) BAD ONES
Flutter means
really fast beats but contraction is coordinated so blood being mobilized
Fibrillation
no mobilization, no coordinated contraction, no blood mvmnt (heart quivers)
V-fib
FATAL due to circus movements (reentry)
A-fib
not immediately threatening bc ventricles receive most blood vol in absence of contraction -> predisposition to clots bc blood sits stagnant in walls of atria
Atrial flutters turns quickly to
A-fib
Defibrillation
can revert v-fib; depolarizes all cells at same time (resets) -> buys time
Cardiac output refers to
vol of blood pumped per min by each ventricle
Cardiac output =
SV x HR
Stroke vol refers to
amount of blood ejected in one beat
HR refers to
of beats per min
Avg HR
70 bpm
Avg SV
70 mls x beat
Avg CO
5L/min
If cardiac demands go up ->
hr incr -> contractile force incr -> SV incr -> CO incr
Cardiac reserve
COmax - COrest
How much cardiac reserve do people with severe heart disease have?
little to none
What the heart kicks the into high gear
SNS
