What's That Sound?
Which part of the ear vibrates when sound waves hit it?
A) Eardrum
B) Broccoliorli
C) Cochlea
D) Vitaminus
...What is the Eardrum?
FOLLOW-ALONG NOTES)
Outer ear: collects and directs sound ( parts = auricle & ear canal)
Middle ear: amplifies vibrations (parts = ossicles, oval window, Eustachian tube)
Inner ear: converts vibrations to signals and maintains balance (parts = cochlea, Organ of Corti, vestibule, semicircular canals)
Hair cells in the Organ of Corti detect vibrations and create nerve signals
Cochlear branch of vestibulocochlear nerve --> brainstem --> thalamus --> auditory cortex
Basilar membrane: different regions respond to different pitches (base = high pitched noise, apex = low pitched noise)
Raise your hand when you can hear the sound.
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The animal shell that most closely resembles the cochlea.
A) Turtle Shell
B) Crab Shell
C) Snail Shell
D) Armadillo Shell
...What is Snail Shell?
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FOLLOW ALONG NOTES:
Sound waves travel through the air
Enter the external auditory canal
They reach the tympanic membrane (eardrum), causing vibration
Vibrations are amplified by ossicles (malleus → incus → stapes)
Stapes pushes on the oval window, transmitting vibrations into the inner ear fluids
Fluid waves travel through the scala vestibuli and scala tympani
The basilar membrane vibrates at specific locations depending on pitch
Hair cells in the Organ of Corti bend, converting mechanical energy to electrical signals
Signals travel through the cochlear branch of the vestibulocochlear nerve (CN VIII)
Nerve signals reach the cochlear nuclei in the medulla
Travel to the superior olivary complex (sound localization)
Continue to the inferior colliculus in the midbrain (auditory reflexes)
Then to the medial geniculate nucleus of the thalamus
Finally reaches the primary auditory cortex in the temporal lobe for sound perception and interpretation
Overall pathway: Air → ear canal → eardrum → ossicles → oval window → cochlea hair cells → CN VIII → brainstem → thalamus → auditory cortex
What is equilibrium and how many senses does it have?
What even is equilibrium?
Equilibrium isn’t just one sense. It's actually two senses,two equilibriums that come from two different organs in the inner ear. These senses help the body maintain balance and orientation.
How many senses are in equilibrium?
Senses:
Static Equilibrium
Dynamic Equilibrium
Distinguishing static vs dynamic equilibrium:
Static equilibrium: 1) senses the position of the head when the body is still. 2) Maintain balance, posture, and stability. 3) it responds to linear movement and gravity.
Dynamic equilibrium: 1) Detects movement when the head or body rotates or moves. 2) Also maintains balance but during sudden motion. 3) Responds to rotational movement
EQUILIBRIUM ORGANS
Static equilibrium organs:
Located in the vestibule (it is the bony chamber between the semicircular canals and the cochlea)
This includes:
Utricle
Saccule
And both of these contain a structure called the macula.
Macula:
Contains hair cells (work as sensory receptors)
Hairs extend into a gelatinous mass
Contains calcium carbonate particles that have weight in them.
Why/How does this work? When the head bends or tilts, gravity causes the gelatinous mass to shift, which bends the hairs. Sending signals to the brain about head position so balance can be adjusted.
Dynamic equilibrium organs:
Located in the three semicircular canals of the labyrinth.
This includes:
Semicircular ducts
Each duct ends in an ampulla
Inside the ampulla is the crista ampullaris
Crista ampullaris:
It has hair cells and hair cells into a gelatinous structure called the cupula.
Why/How does this work? When the head rotates, the fluid in the ducts moves slower than the canal. Bending the hair cells and the cupula. Sending signals to the brain that ultimately interpret the direction of movement.
The equilibrium pathway starts from where and ends in where
a.) inner ear / cerebral cortex
b.) brain stem / thalamus
c.) vestibular nerve / thalamus
d.) brainstem vestibular nuclei / cerebral cortex
a.) inner ear / cerebral cortex
The pathway an equilibrium signal follows starts in the vestibular nerve (CN VIII), moves to the Brainstem Vestibular Nuclei, then the Thalamus, and finally ends in the cerebral cortex