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[Jatt101]

Don't really understand your question. But H+H combines due to high gravity right? (nuclear fusion?)

[Archaemic]

In a star, H+H = He.

Now Hydrogen cancells out Gravitys force on the star, pulling it inwards.

Why?


Sorry i phrased that badly..but do you understand?

Hydrogen does not cancel out gravity. Where did you get this idea? Hydrogen is simply less dense than the rest of the atmosphere, so it rises to the top of the atmosphere (see buoyancy).

[Jatt101]

Can someone answer this question: Why doesn't the heart go into tetanus?

(I know a little but don't quite understand it, please include membrane potential, Ca++ etc.)

[PopeOfDope]

You mean tetany right?
Tetany occurs when action potentials happen in quick succession and fuse together to cause a greater effect, usually contract the muscle faster.
With the heart, action potentials can't summate. The atrial action potential starts with an influx of sodium, but this causes calcium channels to open and calcium moves into the heart cell. This will cause sodium channels to close and you reach a plateau phase. Since the sodium channels are closed, no further action potentials will cause tetany.

[Skyline34]

Why do we get hiccups? :)

[Archaemic]

Hiccups are, if I'm not mistaken, your diaphragm spasming. Not sure what causes them, though.

[filberto]

This is indeed wrong because spacetime is not Euclidean, but in fact a Minkowski space, which behaves differently. The speed of light is absolute. Addition of velocities is no longer linear at relativistic speeds (speeds close to the speed of light). What you're getting into here is special relativity. No matter which direction you're traveling or what speed your traveling, the speed of light is the same in all directions as it would be if you were perceived to be at rest. All inertial reference frames (that is, reference frames that are not accelerating) are equivalent.

It has nothing to do with the doppler effect



Sorry, but I won't do your homework for you. Those questions are just too specific to be anything else :/

So just wondering, but what is changing? Something must be changing to allow this to happen. Is this time?

Also, what is a stitch?

[Archaemic]

What do you mean "what is changing"? I'm not sure I follow.

Also, a stitch is something with sewing. I dunno. All I know is that "A stitch in time saves nine" means that you fix a small hole easily before it grows too large and requires more effort to fix.

[filberto]

No you got me all wrong... A stich when you do exercise and you can get them sometimes?

Well I suppose if light's velocity is definite then this quiestion is pointless. I just thought that if light alwats travels at the speed of light even if an object s moving away from it, something must be happening to make this possible. Eg. why is light's velocity always the same?

[Jatt101]

You mean tetany right?
Tetany occurs when action potentials happen in quick succession and fuse together to cause a greater effect, usually contract the muscle faster.
With the heart, action potentials can't summate. The atrial action potential starts with an influx of sodium, but this causes calcium channels to open and calcium moves into the heart cell. This will cause sodium channels to close and you reach a plateau phase. Since the sodium channels are closed, no further action potentials will cause tetany.

My book & my professor refers to it as tetanus. And I almost forgot that you're pre-med too. I knew all of this before when I took human physiology but forgot it now...better go read up on it. Theres more extracellular Ca++ in the cardiac muscle then inside right? (don't worry I'll find out)
-= Double Post =-

So just wondering, but what is changing? Something must be changing to allow this to happen. Is this time?

Also, what is a stitch?

You mean a twitch or a spasm?

A twitch is just one complete contraction of a muscle fiber.

[FreePlay]

When you get a 'stitch' in a muscle, it's usually a cramp or pain caused by buildup of lactic acid, IIRC.

[Jatt101]

When you get a 'stitch' in a muscle, it's usually a cramp or pain caused by buildup of lactic acid, IIRC.

No, thats when it goes into tetanus. The muscle stays contracted due to some reason such as action potential being fired continuously or Ca++ isn't being pumped out of the cell or into the sarcoplasmic reticulum. Lack of ATP can be a cause sometimes...but it shouldn't make it cramp.



Its different from a spasm...

[Archaemic]

No you got me all wrong... A stich when you do exercise and you can get them sometimes?

Well I suppose if light's velocity is definite then this quiestion is pointless. I just thought that if light alwats travels at the speed of light even if an object s moving away from it, something must be happening to make this possible. Eg. why is light's velocity always the same?

It's because the universe is not Euclidean, it's a Minkowski space. This makes a lot of things that are taken for granted at everyday speeds just not work.

Also, the buildup of lactic acid is what makes muscles sore as you work them (the "burn"). It's not what causes a stitch.

[FreePlay]

then what IS a stitch? I thought that's what it was... bleh

[Jatt101]

stitch

A sharp pain usually felt on the right side, immediately below the rib cage. It occurs mainly when exercising upright, for example when running. A stitch often develops during the early stages of exercise and subsides as exercise continues, but the pain may be so severe that it is impossible to continue. Relief can be gained by supporting the abdominal wall, or by lying down with hips raised. The exact cause of a stitch is unknown but it may be due to lack of oxygen to the muscles used in breathing (particularly the diaphragm and intercostals). Factors that increase the likelihood of a stitch include jolting the body, starting an exercise at too high an intensity, eating and drinking before exercise, weakness of the abdominal wall, and lack of training.

I guess I confused it with cramp...
-= Double Post =-

Also, the buildup of lactic acid is what makes muscles sore as you work them (the "burn"). It's not what causes a stitch.

Thats somewhat true, lactic acid only lasts in your body about <20 minutes after the workout. Its being constantly degraded. The burn when you workout is the lactic acid. But the soreness you feel after an hour or a day after working out is due to muscle damage not lactic acid.

But that type of muscle damage is good and it promotes hypertrophy.

[FreePlay]

I... like you guys. intelligence. mmm.