Vestibular senses are a collection of subsystems that track body position and movement. They are devoted to providing balance and spatial data to help us coordinate our movements in varying body postures and angles. Movements are composed of rotation of the body, sudden stops and forward motion.
The body needs to keep track of head position, where objects are located and our posture. The vestibular system projects to the cerebellum, the thalamus the spine, and the eyes. It triggers reflex reactions oin the limbs and trunk to help you regain balance. It reports on a complex combination of factors. It tracks pressure, bending, spatial orientation, and head position and movement. It signals both linear and rotational acceleration. It shares all of this information with the cortex.
The parietal lobes collect all of the information about where objects are, and where we are in relationship to them. It has a 3D map of the environment, where it updates every time you shift your gaze. This up-to-date representation keeps us from running into things, and avoiding confusion when we look around us.
Sensors in our joints report if an arm is bent or straight. Similarly, sensory in the spine signal if we are bending over, standing straight or stretching to reach something. The neck also has stretch sensors. But most of our head position information comes from our inner ear.
The inner ear has two major components: the semicircular canal system and the otoliths.
The semicircular canals indicate rotational movements. There are 3 cancels ouch side of the head. One reacts when you rotate your head forward and back. One does side to side. And one reacts when you turn your head to look left or right. The two sides work together in a push-pull fashion. Acceleration on one side feels like a push, while the other side feels like a pull.
The canals are organized in a 3D configuration. They are nearly orthogonal, providing independent measures of rotational acceleration. Lateral (horizontal)rotation indicates you are doing spins. Superior (anterior) rotation indicates head-heel movement. It tracks all your somersaults. Inferior (posterior) rotation indicates you are doing cartwheels.
The semicircular canals contain fluid and hair-like fibers. When the head moves, the fluid flows, pushing the hair cells. The mechanical movement of the hairs is transduced into neural signals.
The otoliths measure linear accelerations. They are activated when you are pushed back in your chair during take off. There are two structures on each side of the head. One is the Utricle, meaning sac, and the other is the Saccule. Both work the same way. Both use gravity. They are filled with crystals that are suspended in a gel. When there is linear acceleration, the crystals and the gel more at different rates. The difference indicates how fast you are going. The Utricle sends signals to the eyes to help control their movements. The Saccularis primarily postural. It helps keep you upright.
When the vestibular system goes wrong, you feel groggy, dizzy and disoriented. This is often the case when you have a cold or flu. The condition is called vertigo.
Vertigo is characterized by dizziness, whirling or spinning. In some people it causes nausea and vomiting. In others, they have trouble walking. It 9s the feeling of motion when stationary.
Three sensations are possible. The objective sensations are when you are stationary but the world is moving. The subjective sensations are when the world is stationary and you are moving through is. The third option is pseudovertigo, where you feel you are rotating.
Vertigo is a pretty common complaint. It affects approximately 25% of the population at any given time. It appears in all ages, though more common as you get older. Most cases have peripheral vertigo, meaning it is caused by cold, flu or chemicals. Motion sickness is a good example of this type of vertigo. Central vertigo is caused by a problem in the central nervous system. Causes include migraine headaches, epilepsy, tumors or Parkinson’s disease. Prognosis in these cases is not good. There is either slow improvement, or no improvement at all.
Visceral
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- Vestibular
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