Ves3bular Sense. Chapter 9

Transcription

1 Chapter 9 Majority of illustra3ons in this presenta3on are from Biological Psychology 4 th edi3on ( Sinuer Publica3ons) Ves3bular Sense 1. Ves3bular 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 accelera3on is contained in the inner ear. Three Semicircular Canals 2 Semicircular Canals The inner ear contains three semicircular canals, utricle and saccule. These organs are fluid filled (endolymph) and sense postural 3lts as well as linear mo3on in space. 3 1

2 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. h a p Crus Commune Ampulla 4 Angular Accelera3on During angular accelera3on in any plane results in movement of the endolymph sensing this angular mo3on. 5 Ves3bulocular Reflex The ves3bulocular reflex helps maintain the body by fixa3ng the eyes on an object with movement of the head. Both angular and linear accelera3on signals are used in the ves3bulocular reflex. 6 2

3 Ampulla Three ampullae at the end of the three semicircular canals that contain the sensory hair cells (Humans = 7000 cells). Body rota3ons are registered by hair cells when endolymph moves. Ampulla Capula Endolymph Endolymph Hair cells Semicircular canal Hair cells 7 Horizontal & Ver3cal Movement Horizontal and ver3cal accelera3on is sensed by saccule and utricle in the inner ear. 8 Utricle & Otolithic Membrane 1. Utricle (uterus, 3 mm) senses linear accelera3on in the horizontal plane. 2. Otolithic membrane (ellip3cal in shape) inside utricle is in horizontal plane. Hair cells oriented in many direc3ons register linear accelera3on. Face (eye level) Striola Back of the head 9 3

4 Saccule & Otolithic Membrane Macula inside the saccule (sack) is ver3cally oriented. Humans have 16,000 hair cells in the saccule and can sense ver3cal accelera3on in a number of ver3cal direc3ons. Head Striola Neck 10 Hair Cell S3mula3on Humans have 30,000 hair cells in utricle and 16,000 hair cells in the saccule. Orienta3on of the hair cells in the maculae senses the direc3on of the movement. Kinocilium Stereocilia Endolymph Movement Otoconia (Ear dust) µm Otolithic membrane Kinocilium Hair cells from top Striola Head Movement (forward) Ves3bulocochlear 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 12 4

5 Pathways Semicircular canals, utricle and saccule project to ves3bular nuclei in the brain stem. Some of these fibers pass directly to cerebellum and from there to motor apparatus adjus3ng the body to appropriate posi3ons or movements. 13 Vis3bulospinal Reflex 1. The ves3bulospinal reflex adjusts the posture of body by 3lts in the neck, pelvis, knee and ankles. 2. Utricle and saccule sense horizontal and ver3cal 3lts and con3nuously adjust the body through these reflexes. Pelvis Neck Knee Ankles

6 Ar3ficial S3mula3on 1. Low frequency s3mula3on of the sacs can produce nausea. 2. Low frequency s3mula3on of the semicircular canals produce dizziness and rhythmic eye movements with a slow and fast component (ves3bular or labyrinthine nystagmus). 3. Warm water in the ear can cause dizziness. 4. Alcohol drinking causes dizziness. 16 Diseases 1. Ver3go: Dizziness, caused as a pathological condi3on or due factors like spinning, movement in enclosed vehicles etc. 2. Benign Posi3onal Ver3go (mo3on sickness) 3. Benign Paroxysmal Posi3on Ver3go: caused some3mes by high impact aerobic exercise. 4. Ménière Disease: Water droplets in the semicircular canals, cause intermihent ver3go. 17 Dizziness & Size Look at the rela3ve 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) 18 6