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Practice English Speaking&Listening with: EKG or ECG Interpretation - Part 2/20

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but because potassium channels become

more active so potassium losses become

very very heavy there is a heavy

potassium efflux and as more and more

potassium is going out it means more and

more positive charges are going out it

means cell will again start developing

electronegativity because cell is losing

the positive potassium so when

potassium keep on moving out what really

happens that cells due to loss of

positively charged potassium become

progressively electro negative and

potassium is progressively being lost

potassium is being lost until membrane

potential again becomes at which value?

resting membrane potential value that is

minus 90 milli volts this is that right

so what happened during this time what

happens really that electrically

membrane has come back to its negative

polarization if membrane has come back

to its negative polarization it means

membrane is repolarized due to potassium

efflux membrane has gone to the

phenomenon of repolarization let us

revise it again what really happens this

was a resting myocardial cell it was

having resting membrane potential of

minus 90 milli volt is that right when

it was appropriately stimulated some

cations trickled in entered in these

cations took the resting membrane

potential at threshold potential at

threshold potential voltage-gated sodium

channels open lot of sodium comes in and

rest and then potential goes towards the

it loses all the electronegativity and goes

towards the positive side this

phenomenon is called membrane is

undergoing which phenomenal

depolarization membrane is depolarized

after depolarization in ventricular and

atrial cells repolarization process

start and repolarization process

initially

potassium goes out but very soon calcium

start coming in for a brief time

potassium is going out but at the same

time calcium is coming in so cations are

lost as well as cations are gained so

there is no voltage difference we say

that electrical potential is showing

plateau phase but eventually calcium

channels shut down and potassium

channels become progressively more open

so lot of potassium leaks out and due to

heavy losses of positive ions right

membrane become progressively electronegative

inside and potassium keep on

going out until the membrane voltage

goes back to its resting negatively

polarized state so we say that there is

membrane has gone under the phenomenon

of repolarization so these two processes

together they are called depolarization

and repolarization is that right so by

stimulation we say this cell number one

has undergone process of depolarization

and after the depolarization it has

undergone repolarization is that right

once this cell has cell went under

depolarization once this cell it was

undergoing depolarization due to sodium

and flats right thus sodium which was

coming to the sell some of this sodium

through gap junctions these are very

special connections between the adjacent

myocardial cells adjacent myocardial

cells neighboring myocardial cells have

electrical windows so what happens when

one cell undergo depolarization the

cations which have come into the cell

some of these cations trickle to the

next cell

here they go to the next cell when's

cations from the first stimulated cell

prickle into next cell what really

happens then resting membrane potential

of the next cell will reach up to yes

please reach up to threshold and then

what will happen voltage-gated sodium

channels will open into this then same

thing will happen for short time

voltage-gated calcium and potassium

channels will be open simultaneously

eventually calcium channel stop but

potassium channel keep on working and

losses of potassium eventually take the

membrane potential back to its resting

situation so it means depolarization of

one cell led to the depolarization of

second cell and when second cell is

depolarized when second cell gate gains

lot of cations you trickles the cations

into third cell and then third cell

undergoes the process of depolarization

and repolarization it means that this

fluctuating potential of the membrane

right the membrane fluctuate from

resting and potential to depolarization

and then it fluctuates back to

repolarization this depolarization and

repolarization they are moving in the

cell membranes because depolarization

and reposition the moving so this

fluctuation total electrical fluctuation

of depolarization and repolarization

because it is mobile it is called action

potential as the right let me write it

more clearly that there is yes resting

membrane potential and with proper

stimulation there is stimulation resting

minus potential will lead to the

membrane to yes please depolarization

then depolarization will stimulate

initially calcium and potassium channels

but eventually potassium channels become

very active and a lot of potassium goes

out and that leads to repolarization

and as depolarization and

repolarization the moving on the

membrane so both of them together they

are called action yes please action

potential is that right? so in next

discussion when I say their cells are

undergoing depolarization it means cell

is gaining cations usually sodium in

case of atrial and ventricular cells the

undergo during depolarization the gain

sodium cations right and if there is

special point if there is depolarization

of SA node and AV node remember

depolarization of SA node and AV node is

not sodium-dependent that is

calcium-dependent so it means when I say

that atrial tissue or ventricular

tissues are drawing depolarization it

means those tissues are gaining sodium

and if I say SA node and AV node are

depolarizing it means they are gaining

calcium but anyway depolarization is

whenever cell is appropriately

stimulated a lot of sodium or calcium

come in and depolarizes the cell but

whenever cell is depolarized it is

followed by which activity

repolarization and this depolarization

in one cell stimulates the next cell

through the gap junctions then next cell

become depolarized and second cell will

depolarize the third cell and third cell

will depolarize the next cell so in this

way in the heart because every cell has

electrical windows or gap junctions with

the next cell so electrical stimulation

of one cell can lead to the electrical

stimulation of the next cell am i clear

if this basic concept is clear now we'll

talk about that little bit more in

detail right

eventually what we have to understand

today we have to understand that how

electrical activity of the heart can

eventually be presented as ECG pattern

is that right now we develop some more

basic concepts let's suppose here is

your heart these are your atrial

chambers and here we have your yes please

ventricular chambers right of course

here should be SA node sinoatrial node

and in between the atrial and ventricle

this is fibrous what is this fibrous

anulus right and only electrical

connection between the atrial and ventricle

is what is this? AV node the only

electrical window between the atrial

myocardium and ventricular myocardium is

AV node is it right? so this is SA node

here it is AV node this is atrial

myocardium and here it is ventricular

myocardium right now you see

The Description of EKG or ECG Interpretation - Part 2/20