Chapter 9

Majority of illustraons in this presentaon are from Biological Psychology 4th edion (© Sinuer Publicaons)

Vesbular Sense

1. Vesbular sense or the sense of equilibrium and balance works for birds in air, fish in water, and terrestrial animals on land. 2. Sensory organ that senses gravity and acceleraon is contained in the inner ear.

Three Semicircular Canals

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Semicircular Canals

The inner ear contains three semicircular canals, utricle and saccule. These organs are fluid filled (endolymph) and sense postural lts as well as linear moon in space.

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1 Angular Movement

Three semicircular canals, horizontal (h) which is leveled when the head is upright; anterior (a) is in the front and posterior (p) lie at the back orthogonal to each other.

a Crus h p Commune

Ampulla 4

Angular Acceleraon

During angular acceleraon in any plane results in movement of the endolymph sensing this angular moon. www.kpcnews.net

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Vesbulocular Reflex

The vesbulocular reflex helps maintain the body by fixang the eyes on an object with movement of the head. Both angular and linear acceleraon signals are used in the vesbulocular reflex.

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2 Ampulla

Three ampullae at the end of the three semicircular canals that contain the sensory hair cells (Humans = 7000 cells). Body rotaons are registered by hair cells when endolymph moves. Capula Ampulla

Endolymph Endolymph

Semicircular Hair cells canal Hair cells

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Horizontal & Vercal Movement www.askamathemacian.com Horizontal and vercal acceleraon is sensed by saccule

and utricle in the inner ear.

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Utricle & Otolithic Membrane

1. Utricle (uterus, 3 mm) senses linear acceleraon in the horizontal plane. 2. Otolithic membrane (ellipcal in shape) inside utricle is in horizontal plane. Hair cells oriented in many direcons register linear acceleraon.

Face (eye level)

Striola

Back of the head 9

3 Saccule & Otolithic Membrane

Macula inside the saccule (sack) is vercally oriented. Humans have 16,000 hair cells in the saccule and can sense vercal acceleraon in a number of vercal direcons. Head

Striola

Neck 10

Hair Cell Smulaon

Humans have 30,000 hair cells in utricle and 16,000 hair cells in the saccule. Orientaon of the hair cells in the maculae senses the direcon of the movement.

Endolymph Movement Otoconia Kinocilium (Ear dust) 0.5-10 µm

Otolithic membrane Stereocilia

Striola Kinocilium Vesbulocochlear Hair cells from top Head Movement (forward) Nerve 11

Lateral Lines

Much like the hair cells in the semicircular canals, utricle and saccule, lateral lines in fish sense changes in water to make appropriate bodily movements.

Lateral Lines

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4 Pathways

Semicircular canals, utricle and saccule project to vesbular nuclei in the brain stem. Some of these fibers pass directly to cerebellum and from there to motor apparatus adjusng the body to appropriate posions or movements.

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Visbulospinal Reflex

1. The vesbulospinal reflex Neck adjusts the posture of body by lts in the neck, pelvis, knee and ankles. 2. Utricle and saccule sense Pelvis horizontal and vercal lts and connuously adjust the body through these Knee reflexes. Ankles

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5 Arficial Smulaon

1. Low frequency smulaon of the sacs can produce nausea. 2. Low frequency smulaon of the semicircular canals produce dizziness and rhythmic eye movements with a slow and fast component (vesbular or labyrinthine nystagmus). 3. Warm water in the ear can cause dizziness. 4. Alcohol drinking causes dizziness.

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Diseases

1. Vergo: Dizziness, caused as a pathological condion or due factors like spinning, movement in enclosed vehicles etc. 2. Benign Posional Vergo (moon sickness) 3. Benign Paroxysmal Posion Vergo: caused somemes by high impact aerobic exercise. 4. Ménière Disease: Water droplets in the semicircular canals, cause intermient vergo.

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Dizziness & Size

Look at the relave body size of a dolphin and a bushbaby, and compare semicircular canals in both animals. Absence of dizziness in the dolphin may be due to small semicircular canals. Dolphin Bushbaby Dolphin Bushbaby (primate)

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