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Lecture 35

BIOL 1082 Lecture Notes - Lecture 35: Basilar Membrane, Oval Window, Cochlear DuctPremium

5 pages53 viewsSpring 2018

Department
Biological Sciences
Course Code
BIOL 1082
Professor
Mosley
Lecture
35

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Ch. 44 LO Part 2
Mechanoreceptors, taste, smelling, and seeing Textbook Reading: Concepts: 44.2-44.5
https://quizlet.com/68929328/bios-1710-exam-1-chapter-36-notes-flash-cards/
1. Distinguish among mechanoreceptors, chemoreceptors, electromagnetic
receptors, nociceptors, and thermoreceptors.
Mechanoreceptorsrespond to touch, pressure, vibration, stretch, and itch
Thermoreceptorssensitive to changes in temperature
Photoreceptorsrespond to light energy (e.g., retina)
Chemoreceptorsrespond to chemicals (e.g., smell, taste, changes in blood chemistry)
Nociceptorssensitive to pain-causing stimuli (e.g. extreme heat or cold, excessive
pressure, inflammatory chemicals)
2. Explain how sound waves in the environment lead to production of action potentials in
the inner ear and how different sound frequencies are detected and distinguished in terrestrial
vertebrates.
Hearing in Mammals
o In hear the ear transduces this mechanical stimulus into nerve impulses that the
brain perceives as sound.
o To hear music, speech or other sounds in the environment, hair cells, sensory
cells with hair like projections that detect motion.
o Before the vibration waves reach hair cells, they amplified and transformed by
several accessory structures.
o First the structures in the ear convert the vibrations of moving air into fluid.
o Moving air that reaches the outer ear causes the tympanic membrane to
vibrate.
o The three bones of the middle ear transmit these vibration to the oval window, a
membrane on the cochlea's surface. When one of the bones, the stapes vibrates
again the oval window it creates pressure waves in the fluid inside the cochlea.
o Upon entering the vestibular canal, fluid pressure waves push down on the
cochlear duct and basilar membrane.
o The basilar membrane and attached hair cells then vibrates up and down. The
hair projecting from the hair cells are deflected by the fixed tectorial membrane
which lies above.
o With each vibration, the hairs bend first in one direction and then the other
causing ion channels in the hair cells to open or close.
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o Bending in one direction depolarizes the hair cells, increasing the
neurotransmitter release and the frequency of action potentials directed to the
brain along the auditory nerve.
o Bending the hairs in the other direction hyperpolarizes hair cells, reducing the
neurotransmitter release and the frequency of auditory nerve sensation
o After propagating through the vestibular canal, pressure waves pass around the
apex of the cochlea and dissipate as they strike the round window,
o The damping of sound waves resets the apparatus for the next vibrations that
arrive
o The ear captures information about the volume and pitch.
Hearing in Aquatic Animals
o Hearing in other vertebrate such as aquatic animals:
o Fish rely on several systems for detecting movement and vibration in their
aquatic environment.
o One system involves a pair of inner ears that contain otoliths and hair cells.
o Fish have no ear drum, cochlea or opening to the outside of the body.
o Instead, the vibrations of the water caused by sound waves are conducted to the
inner ear through the skeleton of the head.
o Some fishes also have a series of bones that conduct vibrations to the inner ear
from the swim bladder.
Hearing in Others
o In the ear of a frog or toad, sound vibrations in the air are conduced to the inner
ear by a tympanic membrane on the body surface and a single middle ear bone.
o Birds and reptiles are also the same, but they have a cochlea.
3. Compare and contrast this to hearing in aquatic animals. Compare and contrast how
body position and movement are detected in terrestrial and aquatic animals.
Equilibrium in Mammals
o The chambers called the utricle and saccule allows up to perceive position with
respect to gravity of linear movement.
o Each of these chambers are situated in a vestibule behind the oval window,
contains hair cells that project into a gelatinous material.
o Embedded in the gel are small calcium carbonate particles called otoliths.
o When you tilt your head, the otoliths press on the hair protruding into the gel.
o The hair cell receptors transform this deflection into a change in the output of
sensory neurons, signaling the brain that you head is at an angle.
o This also helps you perceive acceleration.
o 3 fluid filled semicircular canal connected to the utricle detect turning of the
head and rotational acceleration
o Within each canal the hair cells form a cluster, with the hair projecting into a
gelatinous cap called a cupula.
o These canals also are arranged in 3 spatial planes that can detect angular motion
of the head in any direction.
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