1. Homework Sheet2. Review3. Powerpoint4. Video5. Practice Problems6. Worksheet

Sept. 21, 2011

LESSON 6 – THE EARBiology 30 - LS

Review

Review Brain parts

Review

Review

List of Receptor TypesChemoreceptor Sensitive to chemicals (tongue, nose, blood, organs)

Baroreceptor Sensitive to pressure(found in the skin and blood vessels)

Osmoreceptor Sensitive to fluid (water) levels (found in blood vessels)

Photoreceptor Sensitive to light (eyes)

Thermoreceptor Sensitive to heat (skin)

Mechanoreceptor Sensitive to vibrations (ear)

Lobe Task

Frontal Voluntary muscle movements, basic intelligence, personality

Temporal Hearing

Occipital Vision

Parietal Skin sensory information and body position

The Ear

The ear is composed of three parts: the outer ear, the middle ear, and the inner ear. Sound is captured by the pinna, transmitted down the auditory canal where it strikes the tympanic membrane (eardrum). The resultant vibrating tympanic membrane moves a series of three bones (the malleus, the incus, and the stapes) on the other side in the middle ear. The middle ear is an air filled area with its air pressure the same as the outside air as the result of the Eustachian tube.

The final of these three bones, the stapes, transfers the vibrations of to the membrane of the oval window. The oval window is much smaller than the tympanic membrane and as a result the vibrations are magnified 15-20 times.

Ear Cross Section

The vibrations then travel into the fluid filled inner ear causing waves to propagate through a coiled section of the inner ear called the cochlea (sound is further amplified in the fluid canals because sound travels faster through water than the air). Here, special hair cells projecting into the fluid of the inner ear catching the movement of the vibrations. Movement of the hair cells transfers energy to the organ of corti in the membrane which have special receptor cells that when stimulated cause action potentials to occur across synapses which are then transmitted by neural cells.

Organ of Corti

Sounds of higher frequencies affect the hair cells most near the beginning of the cochlea while sounds of lower frequencies can travel further through the cochlea to affect hair cells further along the cochlea. Recall that action potentials are all-or-none response and action potentials triggered at different locations in the cochlea determine why sounds of different frequencies are perceived as high and low tones by the brain.

Worksheet!