Anatomy and Physiology Marieb’s Human Anatomy and Physiology Marieb w Hoehn Chapter 13 – General Sensory Receptors Chapter 15 - Special Sensory Receptors Lecture 22 55 slides, 155 min. (1 -> 26, 80 min; 28 -> end, 75 min.)

Lecture Overview Introduction to the senses and sensation Types of sensors Classification of sensory receptors Anatomy of the ear Physiology of hearing/equilibrium Anatomy of the eye Physiology of vision Video 1 Video 2 Video 3

Special Senses sensory receptors are within large, complex sensory organs in the head hearing and equilibrium in ears sight in eyes smell in olfactory organs taste (gustation) in taste buds (Video 2)* (Video 3) Not covered in video – see master slide set

Overview of the Ear

External Ear auricle (pinna) external auditory meatus collects sounds waves external auditory meatus lined with ceruminous glands carries sound to tympanic membrane terminates at tympanic membrane tympanic membrane vibrates in response to sound waves

The Middle Ear (Tympanic Cavity) Typanic (attenuation) reflex: Elicited about 0.1 sec following loud noise; causes contraction of the tensor tympani m. and stapedius m. to dampen transmission of sound waves

Auditory Tube Eustachian, auditory, or pharyngotympanic tube connects middle ear to throat helps maintain equal pressure on both sides of tympanic membrane usually closed by valve-like flaps in throat When pressure in tympanic cavity is higher than in nasopharynx, tube opens automatically. But the converse is not true, and the tube must be forced open (swallowing, yawning, chewing).

Inner Ear 3 Parts of Labyrinth cochlea semicircular canals vestibule functions in hearing semicircular canals function in equilibrium vestibule functions in equilibrium utricle and saccule Labyrinth

Cochlea Scala vestibuli upper compartment Cochlea as it would look ‘unwound’ Tympano = in relation to, in connection with Oval window = base of scala vestibuli (vestibular duct); round window = base of scala tympani (tympanic duct). Scala vestibuli and s. tympani are filled with perilymph (like interstitial fluid ad CSF); cochlear duct (s. media) is filled with endolymph (unique comp., but similar to intracellular fluid) Scala vestibuli upper compartment leads from oval window to apex of spiral part of bony labyrinth Scala tympani lower compartment extends from apex of the cochlea to round window part of bony labyrinth

Organ of Corti group of hearing receptor cells (hair cells) on upper surface of basilar membrane different frequencies of vibration move different parts of basilar membrane particular sound frequencies cause hairs (stereocilia) of receptor cells to bend nerve impulse generated

Physiology of Hearing Know pathway for exam Figure from: Marieb, Human Anatomy & Physiology, Pearson, 2013 Know pathway for exam Tympanic membrane  malleus  incus  stapes  oval window  scala vestibuli  scala tympani  round window

Auditory Nerve Pathways Accessory Nerve (CN XI) Figure from: Martini, Fundamentals of Anatomy & Physiology, Pearson Education, 2004 (pons)

Vestibule Utricle communicates with saccule and membranous portion of semicircular canals Saccule communicates with cochlear duct Macula contains hair cells of utricle (horizontal) and saccule (vertical) Utricle and saccule provide sensations of: 1) gravity and 2) linear acceleration These organs function in static equilibrium (head/body are still)

Macula responds to changes in head position bending of hairs results in generation of nerve impulse

Semicircular Canals three canals at right angles ampulla (expansion) swelling of membranous labyrinth that communicates with the vestibule crista ampullaris sensory organ of ampulla hair cells and supporting cells rapid turns of head or body stimulate hair cells Acceleration of fluid inside canals causes nerve impulse These organs function in dynamic equilibrium (head/body are in motion)

Crista Ampullaris Semicircular canals respond to rotational, nonlinear movements of the head

Pathways for Equilibrium Sensations For vestibulo-ocular reflex 80 min to this point. Figure from: Martini, Fundamentals of Anatomy & Physiology, Benjamin Cummings, 2004 *

Please Take the Short Quiz Remember to take the brief quiz now to see if you’ve gotten the major concepts from the video. You can always go back and review the video as many times as you like – and can retake the quiz, as well.