Chp 18 class recording Flashcards
Differences between cardiac muscle action potential
steep/fast depolarization
has a plateau
and then we repolarize
why does cardiac muscle plateau during action potential
we need to make sure is filling up all the ventricles
also because of calcium channels opening in the cardiac muscle fibers
cardiac muscle at rest is what milivolt
-90
what is the plateau for the cardiac muscles action potential
a maintained/sustained depolarization
what causes the plateau
the calcium channels being slow to open
does the heart gradually or quickly repolarize
gradually
does the cardiac muscle have hyperpolarization
no, but we do have a period of rest
depolarization happens because of
Na
repolarization happens because of
K
cardiac muscle action potential ion stages
Na
Ca
K
Everytime you see ca you know what is happening in the heart
contraction and plaeua is happening
even though we have no hyperpolarization we still need a protective mechanism so we aren’t sending messages to the sanode repeadtly. So when is that happening
in the middle of the plauteu is our absolute refractory period (when the heart is contracting)
the slow depolarization is only happening at the SA node until we get to
threshold
what kind of memebranes does the heart have and why
leaky, so I dont have to put as much effort into contraction
why does the heart have leaky membranes
to increase it’s own control
what can take over our pacemaker
sympathetic nervous system lack of calcium electrolyte balance caffeine, smoking, any kind of stimulant hypoxia (low oxygen) from anemia
why does hypoxia speed up the heart overriding the sa node
because the heart has to work harder to give every tissue he same oxygen
ectopic pacemakers are
outside factors overriding the pacemaker, stimulants, sanode damage hypoxia
EKGs do what
measure the electrical activity at each junction
electrical pathway of cardiac contractions
sa node
atrial muscle
av node
ventricular muscle
contractions only happen where in the heart
the ventricular walls
how long does it take the cardiac electrical muscle to send messages
.05 secs sa node to av node
.1 secs av node onwards (slows down)
why does conduction slow in the heart
to allow the atria to fill with blood, send to ventricles
three phases of the heart on EKG
p, QRS, T
the most important phase in detecting actual contraction of the ventricles
QRS
T wave on EKG is going where
back to rest
p wave represents
sanode
atrial depolarization
if I have an inverted p wave what can you assume?
they need a pace maker
and something is wrong with the sanode
what does it mean if your QRS complex is drawn out?
contraction of the ventricles is slower
what does the T wave represent
ventricular repolarization
are invertted t waves common or uncommon… meaning what?
common, that we’re not able to go back to rest and each contraction is not as strong
what makes the heart sounds
when valves close
the first heart sound we hear is made by
when our aortic and pulmonary valves close
second heart sound is heard when what
av valves are closed
what valves have to open to fill the ventricles with blood. And which valves are closed
av valves
exit valves
blood drops down and ventricles
contract
systole means
contraction of ventricles
diastole means
relaxation of the ventricles
isovolumetric contraction and relaxation is referring to
at the end of systole and diastole how much blood is left over
the cardiac cycle always starts with
blood coming back to the heart
ventricular contraction happens because
the av valves close
the beginning of the ventricular systole
when the av valves close
period of isovolumic contraction
systole (how much volume is in the ventricles at the end of systole)
diastole happens
immediately after we contract
period of isovolumic relaxation
diastole
what valves have to be closed during diastole
semilunar
at the end of diastole what is happening
the ventricles are completely filled and the av valves are open
in the middle of diastole what is happening
the ventricles are filling
initial filling of blood is called
isovolumetric relaxation
beginning of diastole
then the cusps are completely open allowing blood to fill up
complete relaxtion
middle of diastole
maxed out at that filling capacity of ventricles
end of diastole
isometric contraction. just now sending the message to the purkinges fibers sending message to contract. av valves are closed and semilunar valves are open
initial phase of systole
ventricular ejection of blood is what phase
middle of systole
semilunar valves close means
end of systole
what is stroke volume
how much blood is put out of the heart at each contraction
how well this container is able to hold all of us before it explodes is called
preload
contractility is exactly at the end of
systole
how well the ventricular cardiac cells contracting is what
preload and contractility
the pressure that the ventricles need to overcome because of volume in the atrium
afterload
how does norepinephrine from the sympathetic nervous system how does it override the heart
opens calcium channels bypassing the sanode
the heart increases the force contraction without increasing the length of the muscle is called
inotropic effect
if the heart is overworked it starts to build more
myocradium
an enlarged heart due to muscle growth
hypertrophy
intrinsic effect of your pacemaker is
the sanode
if your sanode is messed up who takes over
av node
