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The Endocrine System

  1. Jun 9, 2005 #1
    I have a bio test tomorrow on the endocrine and nervous systems, and i have a few questions.
    1) Are the endocrine glands and the exocrine glands both part of the endocrine system?
    2) For exocrine glands, do the glands just secrete the hormones through ducts or tubes, or do they actually use these hormones (e.g. tear and sweat glands)?
    3) How does ADH regulate Na levels if it only controls water permeability? (if there's more water in the blood, would the Na conc. just decrease?)
    4) How does depolarization work, that is, is there a Na/K pump after every K and Na "door"? (i.e. the impulse travels like so: K(open)Na(closed)-->K(closed)Na (open) --> Na/K pump....and this repeats)

    Test is tommorrow - thanks.
  2. jcsd
  3. Jun 13, 2005 #2


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    Show us some of your thoughts on all your questions (like you did for question 3) and then we can try and steer you in the right direction. For the yes/no answers, it will help to explain your reasoning. :smile:
    (see forum's policy)

    Q3: you said: "if there's more water in the blood, would the Na conc. just decrease?"
    Comment: what happens when the solvent (water) concentration increases but the ion (sodium) concentration remains constant? how does this change in liquid volume affect the forces inside the vessel (capillaries, veins, arteries, etc...)?
  4. Jun 27, 2005 #3
    well, for: 1) i would say yes because they both secrete hormones
    2) no idea. because our notes only focus on endocrine glands
    3) if water conc increases, then sodium conc. decreases because it pretty much becomes diluted.
    4) i would think that there is sodium/potassium pump after each pair of channels, so that the concentration of K and Na can return back to normal before depolairzation continues, but i'm not sure.
  5. Jun 27, 2005 #4
    1) No, exocrine glands don't secrete hormones, therefore are not part of the endocrine system. They secrete other substances, like pancreatic juices through ducts, whereas endocrine glands do not have ducts and secrete horomones right into the bloodsystem. Note that the pancreas is an exocrine and an endocrine gland, it secretes both hormones right into the bloodstream and other substances (juices) through ducts.
    2) Exocrine glands don't secrete hormones. They secrete other substances through ducts. If you have a test on the nervous system and endocrine system, you should not be asked about exocrine glands ACCEPT, you will likely get this Q:

    Which gland is exocrine and endocrine? Answer: Pancreas.
  6. Jun 27, 2005 #5
    elevated level of salt will osmotically pull water from the surrounding tissues, thereby raising the blood pressure. likewise, raising the volume of water in the blood will cause Na to diffuse into the blood.
  7. Jun 27, 2005 #6
    4): Depolarization: the idea is that the axons are aligned with Na+/K- pumps such that
    when the all-or-none firing principle occurs these pumps activate letting mostly Na+ in
    (can't remeber but i believe K- out-pumps don't open till around -40 thus leading to the quick rise in the peak) once the 0 threshold or was it +30 threshold is reached. the Na+
    in-pumps close(i odn't think the K- pumps close at the peak..but you should search for google for that)

    Hyperpolarization: once teh Na+ in-pumps close the Na+ out-pumps open and the reverse process hyperpolarization begins. K- out-pumps close. and K-inpumps open as

    the refractory period: is caused when hyperpolarization overshoots the resting...that is to much Na+ is let in so there's a time in which some Na+ or Cl- is exchanged..sorry my neurophysiology is long lost.

    you should also loook into Cl- pumps I believ they flow opposite to K- and are less concentration(thus minimal)
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