Lecture Notes: Stimulus for the Vestibular System
I. Head Acceleration as the Main Stimulus
- The vestibular system relies on head acceleration as its primary stimulus.
- There are two main types of head acceleration:
- Linear acceleration: This is a straight-line acceleration, like the feeling of gravity pulling you down.
- Angular acceleration: This is a rotational acceleration, like spinning on a merry-go-round.
II. Organs for Sensing Linear Acceleration (Otoconial Organs)
- The otoconial organs are responsible for detecting linear acceleration.
- They contain a dense mass (like a tiny rock) made of calcium carbonate.
- When you move your head linearly (e.g., feeling gravity), this mass shifts due to inertia, bending hairs on sensory cells and sending a signal to the brain.
- The lecture uses a hanging rock vs. feather analogy to illustrate how mass is crucial for sensing linear acceleration.
III. Organs for Sensing Rotational Acceleration (Semicircular Canals)
- The semicircular canals detect rotational acceleration.
- They are essentially fluid-filled tubes with a hair cell membrane (cupula) acting like a lightweight sensor.
- During rotational acceleration, the fluid in the canals moves due to inertia, pushing on the cupula and stimulating hair cells, which then send signals to the brain.
- The analogy of a feather moving through fluid is used to explain how the cupula detects rotation.
IV. Next Topic: A Closer Look at the Vestibular Apparatus
The next part of the lecture will delve deeper into the structure of these vestibular organs.