vestibular
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14 terms
Terms | Definitions |
|---|---|
 What is function of vestibular system? | Is a function of the fluid-filled inner ear. Reports to the brain movement of head in space. Allows us to maintain balance, maintain vision, keep upright. |
| Semi-circular canals...? | Are a series of three chambers filled with a membranous tube filled with endolymph. Each of the 3 chambers have a swelling at their base called an ampulla. These report rotational acceleration. Have 3 in EACH ear. Each reports one plane of movement (x, y, z). The membrane of the semi-circular canals is attached to the skull - so anywhere the skull moves, the haircells and membrane move with it. The endolymph inside moves separately - is left behind a little bit. If head moves left, endolymph is left behind and moves right in relation...the movement of endolymph pushes the cupulla, which pushes the hair cells over to the right too. If the hairs are pushed towards the kinocilium, they're depolarised because channels are open. If the hairs are pushed away from the kinocilium, their channels close. |
| Ampulla | Is a swelling at the base of each of the 3 semi-circular canals. Is where hair cells are located. These hair cells are embedded in the gelatinous cupulla which envelops hairs cells and blocks off ampulla. |
| Otolith organs | Sense LINEAR acceleration. |
| What do vestibular system movements report to the brain? | Acceleration (NOT VELOCITY) (linear and rotational). |
| What does the cupulla do? | Blocks off the ampulla. |
| Hair cells | Are leaky, so are continuously slightly depolarised. Fire constant action potentials. Still head = action potentials still firing. If pushed towards kinocilium they become more leaky, so fire action potentials at a higher frequency. If pushed away from kinocilium (against preferred orientation) they become less leaky, so lower frequency of action potentionals. The advantage of a middle point of action potential firing at rest means that rate can either increase or decrease. |
| When are hair cells depolarised? | When they're pushed towards the kinocilium --> this increases the rate of action potentials firing. |
| When are hair cells repolarised? | When they're pushed away from the kinocilium --> this decreases the rate of action potential firing. |
| How to hair cells sense DIRECTION of movement? | If head is rotating left, fluid on left side of head is displaced to the right. Fluid on right side of head is displaced to the left. Hair cells on one side of head are depolarised, and hair cells on other side of head are repolarised. (different rates of firing --> different relative motion of hair cells). Brain then compares info from the two sides. |
| Describe LINEAR acceleration...? | Linear acceleration is reported to the brain by otolith organs, the utricle (sits horizontally with vertical hair cells ---> reports horizontal acceleration) and saccule (sits vertically with horizontal hair cells ---> reports vertical acceleration). A endolymph-filled cavity is above these hair cells (ie the hair cells are surrounded by endolymph). |
| What are otoconia? | "weights" made of calcium carbonate that make the top of the otolith cavity heavy. When the otoconia is displaced backwards, it displaces the hair cells backwards as well. If hair cells displaced towards kinocilium, get increased rate of ap firing, if hair cells displaced away from kinocilium, get decreased rate of ap firing. |
| Describe the output from vestibular apparatus...? | oculomotor nuclei, balance, vision |
| Vestibular nystagmus | Is eye movements to compensate for head movements. |
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