Cardiac Muscle 4- Autorhythmic cells

Cardiac Muscle 4- Autorhythmic cells


– SO THE QUESTION
YOU SHOULD BE ASKING NOW IS WHERE DOES
THE ACTION POTENTIAL COME FROM? WE’RE TALKING
ABOUT THESE CONTRACTILE CELLS WHICH RECEIVE
AN ACTION POTENTIAL MESSAGE DIRECTLY
THROUGH THE GAP JUNCTIONS IN THEIR INTERCALATED DISCS
CAUSES THEM TO FIRE. WE’VE GOT THIS AWESOME MECHANISM FOR HOW CONTRACTILE
MUSCLE CELLS CONTRACT WITH THIS MAGICAL
ACTION POTENTIAL THAT APPEARED OUT OF NOWHERE. WE KNOW THAT IT DIDN’T
COME FROM THE NERVOUS SYSTEM BECAUSE HEART MUSCLE CAN BEAT WITHOUT NERVOUS
INPUT SO IT’S NOT LIKE THE NERVOUS SYSTEM IS
DUMPING NEUROTRANSMITTER ON CONTRACTILE CELLS AND TELLING THEM TO GO SO
WHO’S DOING THE JOB? THAT WOULD BE YOUR FRIENDLY
AUTORHYTHMIC CELLS. SO AUTORHYTHMIC
CELLS ARE SO COOL. HERE’S THE DEAL. THEY DO NOT
HAVE A RESTING POTENTIAL. CONTRACTILE CELLS DID
NOT HAVE A THRESHOLD. AUTORHYTHMIC CELLS HAVE
NO RESTING POTENTIAL; HOWEVER, THEY BEGIN
THE CYCLE AT ABOUT -60 MILLIVOLTS
AND HERE’S THE THING. THEY HAVE SPECIAL CHANNELS. THEY DO HAVE THRESHOLD. -40 IS THRESHOLD. THEY HAVE SPECIAL CHANNELS.
OOPS. THAT’S NOT WHAT I MEANT TO DO. I MEANT TO GO LIKE THAT. AUTORHYTHMIC CELLS HAVE SPECIAL
CHANNELS CALLED I F CHANNELS AND THE F ACTUALLY
COMES FROM THE WORD FUNNY. THESE ARE FUNNY CHANNELS. THE RESEARCHERS THOUGHT THEY
WERE SUPER FUNNY BECAUSE THEY’RE LEAKY. THEY’RE LEAKY FOR SODIUM
AND POTASSIUM BUT TELL ME TRUE DOG POUNDS WHO DO YOU THINK
THEY’RE MORE LEAKY FOR? LOOK WHAT’S HAPPENING
TO MY MEMBRANE POTENTIAL AS THESE FUNNY CHANNELS ARE
DOING THEIR THING. I’M SLOWLY DEPOLARIZING
WHICH MEANS THAT WE’RE PROBABLY A LITTLE MORE LEAKY TO SODIUM THAN TO POTASSIUM
AND THIS IS TOTALLY TRUE. NOW THESE FUNNY CHANNELS CREATE WHAT’S CALLED
THE PACEMAKER POTENTIAL. IT’S NOT A RESTING POTENTIAL BECAUSE IT DOESN’T
STAY AT THE SAME LEVEL. IT’S A PACEMAKER POTENTIAL
BECAUSE CAN YOU IMAGINE IF– ACTUALLY I’M NOT GOING
TO TELL YOU HOW TO IMAGINE LIKE MAKING THIS FIRE FASTER
OR SLOWER. I’M GOING TO LET YOU
THINK ABOUT THAT. EVENTUALLY THE LEAKY
CHANNELS ALLOW ENOUGH SODIUM INTO THE CELL
THAT WE REACH THRESHOLD AND ONCE WE REACH THRESHOLD
THE FUNNY CHANNELS CLOSE AND GUESS WHAT KIND
OF CHANNELS OPEN? CALCIUM CHANNELS OPEN
AND CALCIUM RUSHES IN. CALCIUM RUSHES IN UNTIL WE
REACH ABOUT 20 MILLIVOLTS. CALCIUM COMES IN. WE BECOME MORE POSITIVE. THIS MAKES PERFECT SENSE AND THEN OKAY SO LET’S
MAKE A NOTE OF THAT. CALCIUM COMES IN WHEN
THESE CALCIUM CHANNELS OPEN AND THEN WHO’S GOING
TO OPEN NEXT? LOOK WHAT’S GOING TO HAPPEN.
WE’RE GOING TO REPOLARIZE. HOW ABOUT OPENING UP
SOME POTASSIUM CHANNELS. POTASSIUM GOES OUT. WE REPOLARIZE THE CELL. THIS IS THE PATTERN THAT IS
MAINTAINED BY OUR FRIEND, THE AUTORHYTHMIC CELLS. AS SOON AS WE REACH THRESHOLD
WE GENERATE AN ACTION POTENTIAL AND THEN WE HEAD BACK DOWN
TO WHERE YOU START AT -60. IT ISN’T
THE RESTING MEMBRANE POTENTIAL. IT’S JUST THE STARTING POINT AND
THEN MY FUNNY CHANNELS ARE LEAKY AND SO WE CAN’T HANG OUT
AT A CERTAIN PLACE. EVENTUALLY WE REACH THRESHOLD
BECAUSE OF THOSE LEAKY CHANNELS AND WE FIRE AN ACTION POTENTIAL. NOW THIS, MY FRIENDS,
THIS RIGHT HERE, WE GOT TO HAVE A BETTER
COLOR THAN THAT. OKAY, I’LL JUST SHOW YOU
HOW AWFUL THIS COLOR IS. IT’S TERRIBLE.
THAT– WHAT WAS MY POINT? WE– THIS WE’VE GOT
A +20 MEMBRANE POTENTIAL INSIDE OUR CYTOPLASM NOW
AND THAT CYTOPLASM, THAT +20 PASSES
THROUGH THE GAP JUNCTION AND ACTIVATES THE VOLTAGE
GATED SODIUM CHANNELS AND THE CONTRACTILE CELLS. ONLY 1% OF ALL OF
YOUR HEART MUSCLE CELLS ARE AUTORHYTHMIC CELLS; HOWEVER, BECAUSE OF
THIS PHENOMENON RIGHT HERE THEY GENERATE
ALL THE ACTION POTENTIALS TO KEEP YOUR HEART GOING. THERE IS SOME ANATOMY HERE. WE ACTUALLY NEED TO TAKE A LOOK
AT HOW AUTORHYTHMIC CELLS ARE DISTRIBUTED THROUGH THE HEART
ITSELF SO THAT WE CAN SEE IF THEY’RE FIRING
AT A CERTAIN LEVEL HOW DOES THE MESSAGE GET ALL
THE WAY THROUGH THE ENTIRE HEART AND INITIATE A CONTRACTION
OF YOUR HEART, A BEAT. HOW DO THE AUTORHYTHMIC
CELLS COORDINATE HEART BEATS? WELL, WE HAVE TO LOOK AT HOW
THEY’RE ANATOMICALLY ARRANGED IN

43 thoughts on “Cardiac Muscle 4- Autorhythmic cells

  1. thanks a lot. i'v looked into my (guyton and hall medical physiology book) and i noticed that they is no 'peacemaker potential', but they wrote a 'resting potential' at the same autorhythmic cell (couldn't find an online image for that but if you have the 12th edition of it its at page number 116) 

    thanks again.

  2. OMG! You totally rock!!!! This is by far the best video I've viewed in autorhythmic cells and your positive energy actually re-activated my own; which I'd loss in the midst of studying myself to death. If only all instructors took your approach! Thank you, thank you, thank you.

  3. I don't understand how this can work. If Na is flowing into the cell and then Ca flows into the cell and K flows out of the cell. All the electrolytes need to go back. K needs to get back in the cell, Na and Ca needs to move back out of the cell. The switching back of all the electrolytes is not talked about. How can we just start over if all the electrolytes are not in the correct area?

  4. You're the best person to come across on youtube the night before an important test… So much makes sense now, all thanks to you Wendy!

  5. hey, how did calciun go out after depolarisation? please answer. you are a great teacher by the way! you saved many exams of med students! thanks! thanks a lot!

  6. While I love your enthusiasm I wish you go more in depth explaining funny current you need the hyperpolarization of sa av node to first start funny current depolarization at -60 and this is done by inward entrance of sodium that decreases potassium channel efflux, this is why it si funny. Also when funny current reaches pacemaker potential by depolarizing until -40, the channel that continue the depolarization until reaching +20 mV is the t-type calcium channels which continue depolarization because sodium channels become inactive when reaching 0 mV. It is when you reach +20 mv that voltage gated L-type calcium channels open.

  7. Your videos are so helpful! Your upbeat personality gets me SO EXCITED to study for my anatomy and physiology class every day. I always look forward to each video you create. Thank you!

  8. My CardPulm wanted to sound like Wendy but instead she giggles every other sentence and confuses the entire class. I wish med school professors watch YT for teaching inspiration sometimes.

  9. i didn't learn anything because I was wondering how much energy you use just moving your face so much.

  10. aweosome personality and your vibes are super enthusiastic wow you seem like an honourable teacher

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