How the inner ear keeps me upright Equilibrium How the inner ear keeps me upright

Static Equilibrium Based on the position of the head (body) relative to the force of gravity Takes place in the vestibule of the inner ear Specifically involves two structures: 1. Saccule, and 2. Utricle

How does it work? Within the utricle and saccule a small thickened region called the Macula is responsible for the information necessary to remain upright The maculae (2) are perpendicular to each other and they provide the sensory information that gives feedback on the position of the head relative to the surroundings This information allows us to maintain balance and posture The macula also detect linear acceleration and deceleration

What is the Macula made of? Two cell types: 1) Hair Cells---the sensory receptors 2) Supporting Cells— The hair cells have a thick gelatinous material that sits on them called the Otolithic membrane and dense calcium carbonate stones called otoliths

Equilibrium Function As we move our head, the gelatinous layer moves with us and bends the hairs The otoliths also “roll” with us and stimulate the production of action potentials that are interpreted as movement Can detect front/back/and side to side movement of head If the eyes detect movement (driving) but we are still, this can lead to motion related sickness

Dynamic Equilibrium This is our moving equilibrium Not based in vestibule, but rather in the 3 semicircular ducts that lie at right angles to one another in 3 planes of space Two of the ducts are vertical, and lie in an anterior and posterior position The other duct is horizontal and faces in a lateral direction This specific positioning allows us to detect rotational acceleration or deceleration and movement in all directions

How does it work? Each duct has a dilated portion called the ampulla and within this structure a crista is located The crista have a group of hair cells and supporting cells that are covered by a gelatinous material called the Cupula When we move, the stimulated canal and hair cells move with us and the endolymph (fluid within the semicircular canal) lags behind This allows for the hair cells to bend and to generate ap’s that allow us to detect movement

What is vertigo? Inappropriate sensation of movement Caused by infection, neck injury, strokes, tumors, medications, Meniere’s disease. Person will experience spinning, tilting, swaying, nausea and inappropriate eye movement Treatment varies depending on the cause and severity

What is deafness? Any loss of hearing Two types exist: 1. Conduction deafness – inner ear is fine, no nerve damage is present but something is not allowing sound to travel to the inner ear for processing Could be ear wax, pus, foreign object, or old age related Treatment includes removal of object, hearing aids, medication….etc.

What is deafness? 2. Sensorineural Deafness – damage to the nervous parts of the ear Can be caused by damage to the cochlea, cochlear nerve, processing centers of brain, or organ of corti Need to have a cochlear implant to replace the damaged nerve tissue No hearing aids will work in this case because the ear cannot generate its own action potentials

What is deafness? 3. Meniere’s Disease Degeneration of cranial nerve #8 Thought to be caused by a build up of fluid and pressure in the ear Progressive deafness is an issue because the disease comes and goes in a series of “attacks” Creates issues with balance and movement as well Happens in individuals between the ages of 40-60 Usually starts in one ear but progresses to the other People who have it complain of ringing, hissing, “static” in ear No cure exists