Balance: Otolith Organs

by Thad Wilson, PhD

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    00:01 The Otolith Organs.

    00:03 These also work on the structure of hair cells. Bending in one direction versus another.

    00:10 These structural bent is all towards the kinocilium.

    00:15 This is the tallest component of the hair cell.

    00:19 So if you’re bending in that direction, you will get a depolarization.

    00:23 If you bend in the opposite direction, you will get a hyperpolarization.

    00:28 So how otolith organ works? Are you, are now putting these various lowcals of hair cells? All in a little different configuration.

    00:40 So that in any movement that you get in the head or if there is linear acceleration that takes place.

    00:46 Some of the hair cells will be bent depolarized, some will be bent and hyperpolarized.

    00:53 It is this coordinated amount of information that’s sent back to the brain that helps it understand where it is in space.

    01:04 So this otolith arrangement becomes very important. Which, which way you’re going to bend the hair cells.

    01:11 You can orient the hair cells in multiple directions at the same time.

    01:16 And that is what the otolith organs do.

    01:19 You have a different orientation of these hair cells along the different planes.

    01:25 That way, you can tell when a little movement is made in the head in one direction or another because some of the hair cells are being depolarized and other ones are being hyperpolarized.

    01:36 All depending upon their orientation.

    01:40 How do these cells get bent? There is an interesting process in where there’s gelatinous material, as well as small stones that are made up of calcium to have a little bit of inertia associated with these gelatinous material.

    01:58 Therefore, when they’re bent, they will have a little weight to them and will want to move.

    02:03 And as the gelatinous substance moves, they bend the hair cells.

    02:08 You might ask, okay, why do you need this gelatinous substance? I mean why stick these hair cells and something like jello? The reason is because it allows for better protection of the hair cells.

    02:19 Imagine hair cells are very delicate.

    02:22 If you just simply rub stones allover these hair cells you would break some of them off.

    02:27 But having them mixed in these jello-like substance, you can move the jello round a little bit.

    02:34 And with that does is allow for the hair cells to move but still be in a protected environment.

    02:41 So what activates these otolith organ hair cells? We mentioned movement the number of times but simply the relation to gravity.

    02:51 Are you in a standing position? Or you’re laying supine. Or maybe you’re sitting in the upright position.

    02:58 Or you’re tilting you're head one side or another? All of those changes are sensed by the otolith organs.

    03:06 Because remember that gelatinous substance has a little weight to it.

    03:10 So wherever you are imposition to gravity, it will poll on that gelatinous substance and that gelatinous substance will cause some hair cells to depolarized, another hair cells to hyperpolarized.

    03:26 Interesting linear acceleration also does these.

    03:30 So if you’re driving in a car in the faster you go you get these feeling of movement.

    03:36 Why because they are, that gelatinous substance is being moved back as you accelerate forward.

    03:43 And that movement of the gelatinous substance stimulates or depolarizes some of those hair cells.

    03:51 Same thing it can happen if ride in an elevator.

    03:54 So you could sense linear direction upwards and downwards just like you can forward and back.

    About the Lecture

    The lecture Balance: Otolith Organs by Thad Wilson, PhD is from the course Neurophysiology.

    Included Quiz Questions

    1. Depolarization
    2. Hyperpolarization
    3. No change
    4. Decreased resting potential
    5. Decreased conductance of potassium ions
    1. Gelatinous material and calcium stones
    2. Water
    3. Gelatinous material
    4. Plasma
    5. Calcium stones

    Author of lecture Balance: Otolith Organs

     Thad Wilson, PhD

    Thad Wilson, PhD

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