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Thread: How exactly does salt increase blood pressure?

  1. #1
    Monkey see, monkey denigrate visceral_instinct's Avatar
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    How exactly does salt increase blood pressure?

    According to Wikipedia:

    There is some relationship between dietary salt intake and increased blood volume, potentially resulting in higher arterial pressure, though this varies with the individual and is highly dependent on autonomic nervous system response.
    How does that work? Does salt actually stimulate the sympathetic nervous system?

  2. #2
    My guess is that it would raise the salt content of your blood, leading to more water moving into your vessels due to osmosis, thus causing higher blood pressure.


    On an unrelated note, did you know that if shot with a large caliber slug from a gun with a high muzzle velocity, like a .45, .44 or .50, that you can actually be killed by limb shots due to hydrostatic shock? Getting shot in the arm causes your blood pressure to sky-rocket, causing heart attack and stroke.

  3. #3
    Monkey see, monkey denigrate visceral_instinct's Avatar
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    Yes I did know that.

  4. #4
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    Quote Originally Posted by visceral_instinct View Post
    Yes I did know that.
    Roman is correct. It increases blood volume and thereby increases volumetric pressure at both ends of the pumping cycle.

  5. #5
    Monkey see, monkey denigrate visceral_instinct's Avatar
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    How is the autonomic nervous system involved?

  6. #6
    Quote Originally Posted by visceral_instinct View Post
    How is the autonomic nervous system involved?
    I imagine that it's not so much the salt that affects the ANS, but the ANS that flushes the salt out or simply ignores the osmotic irregularity until it the salt is passed in the urine

  7. #7
    there is one thing that both roman and readonly left out. That is that the salt concentration increases the amount of water reabsorbed from the filtrate by the kidneys. This may just be a technicality they overlooked though

    further more its POSSABLE that increased sodium levels COULD (need to check this) increase the contraction of the heart which effects the CO side of Blood pressure

    Note:
    CO = cardiac output
    BP = CO x peripheral resistance (cheat would be to say the amount of the capillary bed which is opened)
    CO = Stroke volume x heart rate
    stroke volume is the amount of blood pumped in one cycle

  8. #8
    Quote Originally Posted by Asguard View Post
    there is one thing that both roman and readonly left out. That is that the salt concentration increases the amount of water reabsorbed from the filtrate by the kidneys. This may just be a technicality they overlooked though
    Takes time though. And if you're not drinking enough or drinking something with a lot of solutes in it, like soda (high fructose corn syrup [I know, I know, everyone else uses sugar] really soaks up water), then you will retain fluids. You need to drink more to flush the water out.

    [edit]
    Oh. Right.
    You piss less.
    Totally missed what you were saying, Asguard!
    But still, that just leads to more fluid in your body. I'd hypothesize that the actual increase in pressure is due to osmoregulation.
    Last edited by Roman; 10-06-08 at 05:14 PM. Reason: edited parenthetical

  9. #9
    which is the job of the kidneys. The difference between celular fluid and extra celular fluid is controled by the S+\K+ pump and osmosis but that is aimed at regulating whats IN the cells. Regulating BP is the job of the kidneys not the indervidual cells
    Last edited by Asguard; 10-06-08 at 05:19 PM. Reason: sorry BP not PB:p

  10. #10
    uniquely dreadful S.A.M.'s Avatar
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    As Asguard said, hypertension is a kidney disease. There is a protein in the nephron that functions as a rheostat and balances sodium and potassium levels. High salt consumption probably affects the functioning of this protein, since I assume it has a salt sensor in the form of a pump [probably a Na-K ATPase] that regulates the levels of salt in the filtrate. The sensor on chronic exposure to high salt concentrations could get potentiated and malfunction.

  11. #11
    ops, god im an idiot

    Sorry Na+\K+ not S\K

  12. #12
    Quote Originally Posted by Asguard View Post
    which is the job of the kidneys. The difference between celular fluid and extra celular fluid is controled by the S+\K+ pump and osmosis but that is aimed at regulating whats IN the cells. Regulating BP is the job of the kidneys not the indervidual cells
    Quote Originally Posted by S.A.M. View Post
    As Asguard said, hypertension is a kidney disease. There is a protein in the nephron that functions as a rheostat and balances sodium and potassium levels. High salt consumption probably affects the functioning of this protein, since I assume it has a salt sensor in the form of a pump [probably a Na-K ATPase] that regulates the levels of salt in the filtrate. The sensor on chronic exposure to high salt concentrations could get potentiated and malfunction.
    I totally overlooked that.
    What's the ANS' roll in osmoregulation? I would imagine it's relatively small, save for fear responses, etc. I don't know much about nerves though.

  13. #13
    uniquely dreadful S.A.M.'s Avatar
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    I know the system is favored towards sodium retention since sodium is not profuse in foods we are supposed to eat. Reducing sodium goes against the grain so to speak and would be stressful to the system. The ANS responds to either the sodium level in the blood or has a feedback loop with the kidney, because it regulates the tensor of blood vessel walls. All speculation based on general knowledge of physiology

  14. #14
    When I stood up, I kept getting light-headed and dizzy. My doctor told me to eat more salt (I rarely ever use it).
    Could a person have an heart attack from low?

  15. #15
    the kidneys are very much tied up with the adrenial system. I dont know wether they are actually atached to the SNS directly but they are very responcive to stress hormones.

    In the case of sympathetic arosal output is cut because arosal means danger which leads to a potentual loss of blood. The kidneys expect this and compensate by retaining fluids that may be needed.

    If you need more detail than that i will have to look it up

  16. #16
    Quote Originally Posted by Asguard View Post
    the kidneys are very much tied up with the adrenial system. I dont know wether they are actually atached to the SNS directly but they are very responcive to stress hormones.
    Yeah, but in every day maintenance? I suppose SAM's speculation is correct, or at least generally so.

  17. #17
    uniquely dreadful S.A.M.'s Avatar
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    Quote Originally Posted by Roman View Post
    I totally overlooked that.
    What's the ANS' roll in osmoregulation?
    Geez Physiology 101. /slaps forehead

    The renin-angiotensin system. The kidney secretes renin when BP drops; renin induces angiotensin which causes blood vessel constriction. I bet there is an interaction between renin-angiotensin and ANS since peripheral vasoconstriction is required for basic fight or flight.

  18. #18
    orelander there you are PROBABLY looking at hypokalimia (low potasium) which causes heart iregularities because potassium is used to regulate the nerve inpulses to the heart

    Its possable i surpose that hyponatrinum (sodium) could have the same effect but im not sure.

    The other risk is whats called big bucket syndrome, this is where the capillary bed opens up to much (because BP = CO x PR, see above) which causes a massive drop in BP. This is actually one of the causes of anaphaltic shock and one of the ways it can kill

  19. #19
    SAM, thanks
    Im surposed to be revising that now anyway

  20. #20
    uniquely dreadful S.A.M.'s Avatar
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    Quote Originally Posted by Orleander View Post
    When I stood up, I kept getting light-headed and dizzy. My doctor told me to eat more salt (I rarely ever use it).
    Could a person have an heart attack from low?
    The reverse. While low BP can decrease blood perfusion [and hence oxygen supply] to brain, it decreases your probability of cardiovascular incident.

    You probably feel dizzy on standing up due to what is known as the gravity effect. When you stand up suddenly the veins in your heart constrict to compensate for the change in flow due to change in position, if you have low BP, this will cause a sudden drop in the blood pressure since the blood pooled in your extremities will take a little longer [2-3 minutes at the most] to become a part of the equation, reducing the flow of blood to your brain. Look up orthostatic hypotension.

    Its a function of both vascular tension, cardiac output and blood pressure and is a sign of ageing [since all of the above get affected by time]

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