BIOL 472 - Mammalian Physiology - Exam II Material

Penn State - Fall 2026 - Dr. James Strauss

Exteroceptors

Sensory receptors that provide information about the external environment

Visceroceptors

Sensory receptors that provide information about the internal environment

Blood Vessels and Viscera

Where are visceroceptors generally located in the body?

Proprioceptors

Sensory receptors that provide information about body position and movement

Chemoreceptors

Subclass of receptors that provide information about taste and smell

Mechanoreceptors

Subclass of receptors that provide information about touch, blood pressure, hearing, and equilibrium

Thermoreceptors

Subclass of receptors that provide information about temperature

Photoreceptors

Subclass of receptors that provide information about sight

Hearing and balance

What bodily functions is the ear responsible for managing?

Mechanoreceptors and Proprioceptors

What receptor types does the ear use to maintain its function?

50 - 18000 cycles per second

What range of frequency in Hertz can the human ear hear?

Cartilage and bone

What is the auditory canal composed of?

Auricle (Pinna)

What part of the ear is responsible for localization of sound waves?

Tympanic Membrane

What structure, also known as the eardrum, separates the outer and inner ear?

Malleus

Outermost of the three small bones in the middle ear, transmits soundwaves from the tympanic membrane to the incus

Incus

Anvil-shaped bone in the middle ear that acts as a bridge, rocking back and forth to push mechanical energy into the stapes

Stapes

Smallest and lightest bone in the human body, functioning as a piston, carrying sound vibrations directly into the cochlea

Tensor Tympani

Small skeletal muscle that pulls the malleus away from the tympanic membrane to dampen loud noises and prevent ear damage

Stapedius

Smallest skeletal muscle in the human body, contracts to pull the stapes away from the oval window to dampen loud noises and prevent ear damage

Eustachian Tubes

Narrow canal made of cartilage and bone that connects the middle ear to the back of the nose and upper throat, acts as a valve that maintains equal air pressure on both sides of the tympanic membrane

Oval Window

Membrane-covered opening that connects the middle ear to the inner ear, responsible for generating waves in the perilymph

Round Window

Membrane-covered opening in the wall of the inner ear, sitting below and behind the oval window, acts as a release valve for pressure waves

Unbalanced pressure on either side of the tympanic membrane

What causing eustachian tubes to release, causing the ear popping sensation?

Cranial Nerve VIII

What nerve innervates the inner ear?

Osseous Labyrinth and Membranous Labyrinth

What are the two major divisions of the inner ear?

Cochlea, Semicircular Canals, Vestibule

What are the three parts of the osseous labyrinth?

Osseous Labyrinth

Rigid, protective outer shell of the inner ear, filled with perilymph

Scala Vestibuli

Superior chamber of the cochlea, receives sound-induced pressure and carries it upward toward the apex

Scala Tympani

Inferior chamber of the cochlea, carries fluid waves toward the base of the cochlea and releases pressure via the round window

Narrow, thick membrane, high tension

What are the qualities of the base of the cochlea that allow high-frequency sound waves to be transduced there?

Wide, thin membrane, low tension

What are the qualities of the helicotrema that allow low-frequency sound waves to be transduced there?

Semicircular Canals

Three fluid-filled, interconnected loops in the inner ear that sense rotational head movements and help maintain balance

Vestibule

Structure in the inner ear that conrtains the utricle and saccule

Membranous Labyrinth

Continuous system of fluid-filled sacs and ducts located inside the osseous labyrinth, filled with endolymph

Stria Vascularis

Epithelial tissue that synthesizes endolymph

Cochlear duct, semicircular ducts, utricle/saccule

Three major parts of the membranous labyrinth

Organ of Corti

Primary structure in the cochlear duct responsible for hearing that contains the hair cells

20,000

Around how many hair cells are there in one Organ of Corti?

3:1

What is the ratio of outer to inner hair cells in any given Organ of Corti?

Sound transduction

What is the main function of inner hair cells?

90%

What percentage of innervation are inner hair cells responsible for?

10%

What percentage of innervation are outer hair cells responsible for?

Alter characteristics of the basilar membrane

What is the main function of outer hair cells?

Endolymph

What liquid is the apex of the outer hair cell exposed to?

Perilymph

What liquid is the base of the outer hair cell exposed to?

The hair cell hyperpolarizes

What happens when the basilar membrane moves downward?

The hair cell depolarizes

What happens when the basilar membrane moves upward?

Tectorial membrane

What membrane attached to hair cells is stationary?

Basilar membrane

What membrane attached to hair cells vibrates / induces hyperpolarization and depolarization?

Potassium (K+)

What ion does endolymph have a high concentration of?

Sodium (Na+)

What ion does perilymph have a high concentration of?

The basilar membrane moves upwards, K+ moves down the concentration gradient into the hair cell, inducing a Ca2+ influx, and release of neurotransmitters stimulates the vestibulocochlear nerve

How does the depolarization of hair cells happen?

Cochlear Duct

What structure(s) in the membranous labyrinth interact with the cochlear portion of Cranial Nerve VIII?

Semicircular Ducts and Utricle/Saccule

What structure(s) in the membranous labyrinth interact with the vestibular portion of Cranial Nerve VIII?

Crista Ampularis

Sensory receptor organ of rotation located in the base of each of the semicircular ducts

Semicircular Ducts

Three separate channels in the membranous labyrinth responsible for balance

As the head moves, fluid flows in the opposite direction due to inertia. As a result, one side is hyperpolarized and the other is depolarized

How is dynamic equilibrium maintained by the semicircular ducts?

Utricle/Saccule

Fluid-filled sacs within the membranous labyrinth that contain hair cells with otoliths

Gravity and acceleration forces cause depolarization in properly oriented hair cells

How do the utricle/saccule maintain static equilibrium?

Motion Sickness

What condition is caused when signals from the utricle/saccule conflict with visual signals?

Problems with conducting sound vibrations due to ear deformity, or nerve deafness due to damage to hair cells or Cranial Nerve VIII

What are the two possible causes of deafness?

Nystagmus Reflex

The phenomenon that, when the body is rotated, at first the eyes move slowly in the opposite direction, but the eye jumps quickly back to a centered position

Caloric Stimulation Test

Test that checks for function of the inner ear by inserting water into the ear canal that is either colder or warmer than body temp, and convection generates nystagmus reflex in a healthy ear

Olfactory Nerve: Sensory only, smell sensation

Cranial Nerve I

Optic Nerve: Sensory only, sight sensation

Cranial Nerve II

Oculomotor Nerve: Motor only, to most extrinsic eye muscles, also motor to iris and ciliary body

Cranial Nerve III

Trochlear Nerve: Motor only to superior oblique of eye

Cranial Nerve IV

Trigeminal Nerve: Sensory to eye, upper palate, teeth, jaw, mastication muscles, general sensation of tongue, motor to mastication muscles

Cranial Nerve V

Opthalmic, Maxillary, and Mandibular

Three branches of Trigeminal Nerve

Sensory to eye

Function of opthalmic branch of trigeminal nerve

Sensory to upper jaw

Function of maxillary branch of trigeminal nerve

Sensory to lower jaw, tongue

Function of mandibular branch of trigeminal nerve

Abducens Nerve: motor only to lateral rectus muscle of eye

Cranial Nerve VI

Facial Nerve: motor to muscles of facial expression and salivary glands, sensory for the front 2/3 taste buds, face and scalp

Cranial Nerve VII

Vestibulocochlear Nerve: Sensory for hearing, balance, and equilibrium

Cranial Nerve VIII

Glossopharyngeal Nerve: Motor for swallowing and salivary glands, sensory from throat, blood pressure regulation, taste in rear 1/3 of tongue

Cranial Nerve IX

Vagus Nerve: Motor to throat for swallowing, heart, lungs, GI tract, sensory from same areas, deep taste in throat

Cranial Nerve X

Accessory Nerve: Motor to trapezius, sternocleidomastoid

Cranial Nerve XI

Hypoglossal Nerve: Motor to tongue

Cranial Nerve XII

380 - 760 nm

What range of light is visible (that the human eye is sensitive to)?

Conjunctiva

Thin, clear mucous membrane that lines the inner surface of the eyelid and covers the sclera

Cornea

Clear, dome-shaped outer layer at the front of the eye that covers the iris and pupil

Sclera

Dense, tough, opaque white outer layer of the eyeball

Choroid

Middle, blood-vessel-rich layer of the wall of the eye

Ciliary Body

Ring-shaped tissue structure in the middle of the eye

Ciliary body contracts (relaxed suspensory ligaments, lens balls up), eyes converge, pupil constricts

Steps of accomodation triad (adjusting from looking at something far away to something close)

Ciliary body relaxes, suspensory ligaments contract, lens flattens

What happens to the eye when adjusting to see something far away?

Retina

Thin, light-sensitive tissue that lines the inner back wall of the eye

Anterior Chamber

Fluid-filled space directly behind the cornea but directly in front of the lens and iris

Posterior Chamber

Narrow, fluid-filled space behind iris and in front of lens and suspensory ligaments

Aqueous Humor

Clear, watery fluid that fills the front part of the eye

Canal of Schlemm

Vessel that collects aqueous humor from the eye and drains it into venous circulation

Vitreous Humor

Clear, colorless, gel-like substance that fills the posterior portion of the eye between the lens and the retina

Ganglion Layer

Innermost layer of neurosensory retina that contains the bodies of ganglion cells

Amacrine Cells

Diverse class of inhibitory interneurons in the retina that process signals before they reach ganglion cells

Bipolar Cells

Specialized sensory neurons in the retina that collect visual signals from rods and cones and relay them to ganglion and amacrine cells

Horizontal Cells

Interconnecting neurons in retina that provide interference, allowing visual signals to be smooth and prevents strobe-like effect of continual signals

Rods

Light-detecting photoreceptors responsible for low-light and peripheral vision

Cones

Light-detecting photoreceptors responsible for color vision and high-acuity detail

Macula Lutea

Small, oval-shaped yellow area in the center of the retina, managing central visual acuity, with a high density of cones