scott wrote:
>> I have no idea what internal resistance is.
> 
> A pretty accurate model of a battery is a perfect voltage source in 
> series with an "internal" resistor.  This then nicely explains how the 
> more current you try to draw the lower the apparent voltage will be at 
> the terminals of the battery.

As far as I'm aware, resistors affect only current, not potential. But 
hey, I'm sure you know more about this than me...

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Eero Ahonen <aer### [at] removethiszbxtnetinvalid> wrote:
> clipka wrote:
> >
> > You need to invest extra power to get the higher frequency at the same AC
> > voltage and amps, right?
>
> Hmm, possibly.
>
> > So where does that extra power end up if you have the otherwise same AC running
> > through your body?
>
> At least part of it goes to heating the generator, which runs faster :).
>
> > EM field I'd guess - which may be just the extra "kick" you'd rather do without.
>
> That actually sounds reasonable. My head is atm too empty to remember
> how to calculate energies of EM fields, but it would make sense, while
> the field sure is frequency-dependent.
>
> -Aero


electrical impulses to the heart are interrupted and fibrillation occurs. IIRC
there are parts of the heart that receive the electrical impulses from the
brain then transmit secondary impulses to the muscle tissue to contract and
relax in an organised way. The electrical shock interrupts this process and you
get a disorganised high frequency oscillation in different parts of the heart. A
defibrillator is used to stop this effectively stopping the heart and the
natural sinus rhythm can be resumed. Before defibrillators became commonplace
the manual method was to strike the victims chest above the heart with a
controlled blow using the pinkie side of your fist. This was supposed to have


Stephen

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Invisible wrote:
> scott wrote:
>>> I have no idea what internal resistance is.
>>
>> A pretty accurate model of a battery is a perfect voltage source in
>> series with an "internal" resistor.  This then nicely explains how the
>> more current you try to draw the lower the apparent voltage will be at
>> the terminals of the battery.
> 
> As far as I'm aware, resistors affect only current, not potential. But
> hey, I'm sure you know more about this than me...

Try putting 2 resistors in series, connect the power (you'll have eg.
+12V on R1+, R1- on R2+ and R2- on ground) and measure voltages between
R1+/R2-, R1+/R1-, R2+/R2-, you might be surprised

+
|
R1
|
R2
|
-

-Aero

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On 15-6-2009 14:02, Stephen wrote:

> electrical impulses to the heart are interrupted and fibrillation occurs. IIRC
> there are parts of the heart that receive the electrical impulses from the
> brain then transmit secondary impulses to the muscle tissue to contract and
> relax in an organised way. 

No the heart is autonomous, will even beat outside the body for some 
time (hours) if oxygenated. It's frequency can be modulated by stuff in 
the blood and by nerve tissue that is close to the sinus node when they 
release special molecules.

> The electrical shock interrupts this process and you
> get a disorganised high frequency oscillation in different parts of the heart. 

No, but what happens is much more complicated (i.e. you need a 
complicated model to describe it and even then you see it happening 
without getting much more understanding, but it works).
Standard procedure to induce VF in an open chest heart: hold a 9V 
battery against it. And, no, I don't know how it actually works, but it 
does.

> A defibrillator is used to stop this effectively stopping the heart and the
> natural sinus rhythm can be resumed. Before defibrillators became commonplace
> the manual method was to strike the victims chest above the heart with a
> controlled blow using the pinkie side of your fist. This was supposed to have


I does work sometimes. http://en.wikipedia.org/wiki/Precordial_thump Do 
not apply to people that are not in VF: 
http://en.wikipedia.org/wiki/Commotio_cordis

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andrel wrote:

> No the heart is autonomous, will even beat outside the body for some 
> time (hours) if oxygenated.

Does anybody else find it slightly disturbing that andrel knows such things?

I mean, I know there's a good reason, but even so... kinda grusome.

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andrel <a_l### [at] hotmailcom> wrote:
> On 15-6-2009 14:02, Stephen wrote:

> > electrical impulses to the heart are interrupted and fibrillation occurs. IIRC
> > there are parts of the heart that receive the electrical impulses from the
> > brain then transmit secondary impulses to the muscle tissue to contract and
> > relax in an organised way.
>
> No the heart is autonomous, will even beat outside the body for some
> time (hours) if oxygenated. It's frequency can be modulated by stuff in
> the blood and by nerve tissue that is close to the sinus node when they
> release special molecules.
>

I thought that you might respond :)



> > The electrical shock interrupts this process and you
> > get a disorganised high frequency oscillation in different parts of the heart.
>
> No, but what happens is much more complicated (i.e. you need a
> complicated model to describe it and even then you see it happening
> without getting much more understanding, but it works).
> Standard procedure to induce VF in an open chest heart: hold a 9V
> battery against it. And, no, I don't know how it actually works, but it
> does.
>

You are the expert I'm only a first aider


> > A defibrillator is used to stop this effectively stopping the heart and the
> > natural sinus rhythm can be resumed. Before defibrillators became commonplace
> > the manual method was to strike the victims chest above the heart with a
> > controlled blow using the pinkie side of your fist. This was supposed to have

>
> I does work sometimes. http://en.wikipedia.org/wiki/Precordial_thump Do
> not apply to people that are not in VF:

Unless you want to kill them ;)

Stephen

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On 15-6-2009 17:30, Invisible wrote:
> andrel wrote:
> 
>> No the heart is autonomous, will even beat outside the body for some 
>> time (hours) if oxygenated.
> 
> Does anybody else find it slightly disturbing that andrel knows such 
> things?
> 
> I mean, I know there's a good reason, but even so... kinda grusome.

As you may be aware, it is my job. It comes with being in a experimental 
cardiology lab. BTW a beating heart is absolutely not gruesome, I would 
rather say beautiful. I'd be happy to show you if you happen to be in 
Amsterdam some time and an experiment is running. ;)

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Invisible wrote:
> Does anybody else find it slightly disturbing that andrel knows such 
> things?

You don't watch enough TV.

-- 
   Darren New, San Diego CA, USA (PST)
   Insanity is a small city on the western
   border of the State of Mind.

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>>> No the heart is autonomous, will even beat outside the body for some 
>>> time (hours) if oxygenated.
>>
>> Does anybody else find it slightly disturbing that andrel knows such 
>> things?
>>
>> I mean, I know there's a good reason, but even so... kinda grusome.
> 
> As you may be aware, it is my job. It comes with being in a experimental 
> cardiology lab.

Indeed. But still... kinda freaky.

> BTW a beating heart is absolutely not gruesome, I would 
> rather say beautiful. I'd be happy to show you if you happen to be in 
> Amsterdam some time and an experiment is running. ;)

I once saw an operation on TV. They cut open a guy's chest, ripped his 
ripcage apart, and inside was his heart. I swear, it honestly looked 
like it was trying to CLIMB THE HELL OUT OF HIS BODY AND RUN AWAY!! O_O

*shivers*

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>> Does anybody else find it slightly disturbing that andrel knows such 
>> things?
> 
> You don't watch enough TV.

I always thought I watch far too much TV. :-P

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