Physiology 31 Lecture
Chapter 10 - Sensory Physiology
I. Overview
A. General Properties of Sensory Systems
B. Somatic Senses
C. The Ear: Hearing
D. The Ear: Equilibrium
E. The Eye & Vision
II. General Properties of Sensory Systems
A. Sense organs are extensions of the _________ system that respond to changes in the
environment & transmit nerve impulses to the CNS
B. In order to perceive a _____________, the following are necessary:
1. A ____________ (chemical, mechanical, temperature, or light) to initiate a nervous
system response
2. A __________ (sensory neuron dendrites or specialized epithelial cell) is a transducer
that converts the stimulus to a nerve impulse
3. ___________ of the nerve impulse from the receptor to the brain, via sensory
(ascending) nerve tracts in the spinal cord
4. _____________ of the perception in the brain’s cerebral cortex, after passing through
the medulla, pons, & thalamus
C. Senses may be general or special senses
1. _____________ (somatic) senses
a. Have receptors throughout the ________, muscles, tendons, joint capsules, and
viscera.
2. ___________ senses
a. Are limited to the ________ and innervated by cranial nerves
b. Include ________, hearing, equilibrium, taste, and smell
D. Sensory _________ include:
1. ________receptors respond to chemicals; found in the tongue, nose, blood vessels
2. ________receptors respond to heat and cold; found in skin
3. __________ respond to pain and itch; found throughout the body, except in the brain
4. __________receptors respond to physical deformation of the plasma membrane caused
by touch, pressure, stretch, tension, or vibration; found in skin, viscera, and joints
a. Touch receptors include Merkel cells and ____________ corpuscles
b. Pressure receptors include _________ and Ruffini corpuscles
c. _________ceptors sense the position and movements of body parts; found in
muscles, tendons, and joint capsules
5. _________receptors in the eyes respond to light
2
E. Each sensory neuron has a receptive _______
1. A sensory neuron is activated by __________ that fall within the neuron’s receptive field
2. Example: a _____-________ discrimination test
a. In ____ sensitive skin areas, many ________ neurons converge on one ___________
neuron (a large receptive field), thus two pins 20 mm apart are perceived as one
pinprick
b. More _________ skin areas often have smaller receptive areas, with a ____-to-___
relationship between primary and secondary neurons, thus two pins 2 mm apart are
perceived as separate
F. The CNS ___________ sensory information
1. ___________ impulses (except smell) travel to the spinal cord (or brain stem), up
projection tracts to the _________, and are relayed to the cerebral cortex
2. The perceptual __________ is the level of stimulus intensity necessary for us to be
aware of a sensation
a. To keep from being overwhelmed by sensory input, the CNS can selectively “turn
_____” some stimuli
b. ____________ modulation often occurs in secondary or tertiary neurons in the
sensory pathway
G. The CNS must distinguish the 4 properties of a ____________: modality, location,
intensity, and duration
1. Sensory ___________ is indicated by which types of sensory neurons are activated; the
brain associates a signal from a particular type of ____________ with a specific sensation
2. Stimulus ___________ is coded by different types of sensory neurons sending their
impulses through ascending ________ to specific regions of the cerebral _________
3. Stimulus __________ is coded by the ________ of receptors that are activated and by
the ___________ of their action potentials
4. ___________ of a stimulus is coded by the duration of ________ potentials in a sensory
neuron. Neurons may be either:
a. __________ receptors adapt _________ and generate impulses continually (e.g.:
nociceptors, proprioceptors)
b. __________ receptors generate a burst of impulses when first stimulated, adapt
_________, and stop even if stimuli continues (e.g.: touch, pressure, and smell
receptors)
III. __________ Senses include touch, proprioception, temperature, and nocioception (pain and
itch)
A. Receptors for somatic senses are found in the _______ and viscera
1. Receptor activation triggers action potentials in associated __________ sensory neurons,
which travel to the spinal cord and synapse with
2. __________ sensory neurons (interneurons), in ascending tracts, which cross over to the
__________ on the opposite side, where they synapse with
3. __________ sensory neurons, which project to a particular region of the
somato_________ cortex
3
B. Pain that originates in one area, but is felt in another area is called ____________ pain, and
occurs because multiple primary sensory neurons converge onto a single ascending tract
IV. The Ear: Hearing
A. Auditory ___________ in the middle ear
1. Incoming sound waves vibrate the __________ membrane
2. Tympanic vibrations move the malleus, incus, and ________
4. The stapes moves against the ________ (vestibular) window
5. The tympanic ______ helps to protect the ear from loud sounds a. ________ tympani
tenses the tympanic membrane
b. Stapedius muscle limits ________ movement
c. Sudden loud noises can still damage hearing by fracturing the stereo_______ of the
cochlear hair cells
B. Stimulation of cochlear _______ cells
1. Stapes movement causes waves in the scala vestibuli _________
2. Perilymph movement pushes the ___________ membrane down
3. Vestibular membrane movement pushes on ___________ in the cochlear duct
4. Endolymph movement pushes the ________ membrane down & up, bending the hair
cells’ _________ in the tectorial membrane, sending auditory nerve impulses to the
___________ nerve
5. Basilar movement pushes on the perilymph of the scala tympani, causing the
__________ window membrane to bulge out and in
C. Sensory Coding – how we distinguish loudness (__________) and pitch (___________)
1. Loud sounds cause the organ of _________ to vibrate more vigorously
a. More hair cells are excited over a larger area of the ________ membrane
b. More nerve impulses are sent to the __________ nerve
c. The brain detects intense activity from a large region of the organ of _________,
and interprets it as loud sound
2. Sound ___________ (pitch) is distinguished by the region of the __________
membrane that is vibrated
a. ___________ fibers span the length of the basilar membrane, increasing in length
from the base (oval window) to the apex
b. Audible sound waves with frequencies between 20,000 – 20 Hz are detected at
different areas along the _____ membrane
c. Audible sound waves set up perilymph waves that travel through the scala
vestibuli, flexing the ________ membrane, transferring waves to the cochlea,
which flexes the ________ membrane
d. Higher frequency waves stimulate fibers near the ______ of the basilar membrane,
vibrating the membrane at the high frequency
e. Lower frequency waves stimulate fibers near the basilar membrane ______,
vibrating the membrane at the low frequency
f. The stimulation of specific ______ cells along the basilar membrane length is
interpreted in the brain as sound of a certain _______
4
D. The _________ Projection Pathway – sound impulses are sent to the brain in the
following sequence: cochlear hair cells  bipolar neurons  cochlear nerve 
vestibulocochlear nerve  pons  inferior colliculi  thalamus  auditory cortex
(_________ lobe)
1. Vibration of the cochlear _________ membrane bends hair cell stereocilia in the
tectorial membrane, sending a nerve impulse to
2. ___________ neurons in the spiral ganglion that curves around the modiolus, which
sends the impulse to the
3. _________ nerve that joins with the vestibular nerve to form the
4. Vestibulocochlear nerve (CN _____), which sends the impulse to the
5. _______ in the brain stem, which transmits the impulse to the
6. Inferior _______ (auditory reflex center) in the midbrain to the
7. ___________ (medial geniculate nuclei), which relays the impulse to the
8. Primary auditory cortex in the ___________ lobe where it is interpreted as sound
E. _________ (hearing loss) may be caused by two different sources
1. ___________ deafness – results from damage to structures that transmit sound
vibrations to the inner ear
2. __________ (sensorineural) deafness – results from damage to cochlear ______ cells
or other nerve tissue involved in hearing
V. The Ear: Equilibrium
A. Two types of _____________ are
1. _________ – the perception of head orientation when the body is stationary
2. ___________ – the perception of motion or acceleration.
B. Two types of ___________ include
1. ___________ – a change in velocity in a straight line
2. ___________ – a change in the rate of rotation
C. Inner ear ________ responsible for equilibrium are the
1. Utricle & Saccule in the ___________ sense static equilibrium and linear acceleration
2. Semi________ ducts sense angular acceleration (head rotation)
D. __________ & Saccule sensory structures include the
1. ___________ – a patch of sensory hair cells surrounded by epithelial support cells
2. Each ______ cell has many stereocilia and one kinocilium embedded in an
___________ membrane
3. The membrane also contains tiny calcium carbonate “stones” called __________
4. When the head moves, the otolithic membrane slides with gravity and bends the
______ cells, which send a nerve impulse to the _____________ nerve
5. The brain compares input from the utricle & saccule to determine head orientation,
particularly in respect to linear and vertical ___________
5
E. Semicircular ________ sensory structures within include the
1. ___________ – expanded end of the ducts where they join the vestibule, contain the
2. ________ ____________, which houses the receptor hair cells, epithelial support cells,
and cupula
a. _______ cells have stereocilia and a kinocilium embedded in a
b. __________ – a gelatinous membrane that extends from the crista to the roof of the
ampulla
c. When the head turns the duct rotates, but the endolymph lags behind and pushes the
________, which bends the stereo____ and stimulates the hair cells
d. The hair cells transmit nerve impulses to the ________ nerve, which joins the
cochlear nerve to send the impulses to the brain, which interprets the head
___________
F. ________________ Projection Pathways to the Brain
1. Stimulated hair cells in the _______ and the __________ send nerve impulses to the
2. ______________ nerve, which transmits the impulses to the
a. ____________, which is controls skeletal muscle coordination and balance
b. _______ vestibular nucleus, which sends the impulses to the
c. __________ spinal cord, which sends the impulses to the cranial nerves that control
eye movement (CN III, IV, ___) and the muscles of the head and neck (CN ___)
VI. The Eye & Vision
A. Light entry through the pupil is controlled by two contractile elements in the ________
1. Pupillary __________
a. ____________ smooth muscle around the pupil
b. _______sympathetic nerves narrow the pupil in bright light conditions and when
eye ________ changes
c. Both pupils constrict when even one eye is exposed to light – called the
__________________ reflex
2. Pupillary _____________
a. Myoepithelial cells __________ arranged around the pupil
b. ___________ nerves widen the pupil in low light conditions and during stressful
conditions
B. ____________ (bending) of light through the eye is due to 4 substances (from outside to
inside the eye)
1. _________ – clear, convex structure on the anterior eye; most light refraction occurs
here
2. __________ humor – watery fluid in the anterior segment
3. ________ – clear, biconvex structure between the aqueous and vitreous humor; fine
tunes (_________) the incoming image
4. ___________ humor – clear, gel-like material in the posterior segment
a. ____________ – involves an uneven surface on the lens and/or cornea, which causes
light to bend unevenly, causing blurred vision
b. _____________ is an elevated pressure within the eye
1) Often caused by a blockage in the canal of ___________, so aqueous humor
builds up
6
2) Increasing pressure compresses retinal blood vessels and the _________ nerve,
leading to blindness if untreated
C. Emmetropia & the Near Response
1. _______________ is the relaxed state of a normal eye when it is focused on an object
___ ft. or more away; incoming light rays are parallel and focused on the retina
2. The _____ __________ is required to focus the eye on objects closer than 20 ft.; it
consists of the following
a. _____________ of the eyes – pupils begin to move medially
b. _________ constriction to filter out peripheral light rays and minimize spherical
aberrations from the lens
c. Lens ___________ – a change in the curvature of the lens via the following
1) ___________ muscle around the lens contracts, narrowing its diameter
2) ____________ ligaments that connect the ciliary muscle to the lens relax,
allowing the stretched lens to become more ___________
3) A more convex lens ___________ light more and focuses light rays onto the
retina
3. ____________ is a loss of lens accommodation due to a gradual lessening of lens
elasticity as we age
4. ________ (nearsightedness) results from an eye that is too ____, thus distant objects
are focused in front of the retina’s focal point
5. ________ (farsightedness) results from and eye that is too ____, thus near objects are
focused behind the retina’s focal point
VI. Sensory _______________ in the Retina
A. The _________ consists of 2 major layers
1. __________ layer – posterior layer composed of dark cuboidal epithelial cells; absorbs
light that is not absorbed by receptor cells in the
2. ________ layer – inner layer near the vitreous humor, composed of three main layers
of neural cells (from pigment layer to vitreous humor):
a. ________receptor cells – first to receive incoming light rays
1) _____ – cylindrical cells containing rhodopsin pigment that absorbs light;
responsible for ______ vision in black & white
2) ________ – cone-shaped cells that include red, green, and blue photoreceptors
that function in _________ light and are responsible for _______ vision
3) Rods and cones receive and transmit nerve impulses to
b. __________ cells – neuron dendrites receive nerve impulses from rods and cones,
then transmit the impulses along axons to
c. ____________ cells – neuron dendrites receive nerve impulses from bipolar cells;
axons converge to form the _______ nerve that exits the back of the eye and carries
impulses to the brain
7
B. Visual ___________ in the rods and cones include
1. _____________ (visual purple) in rods consists of two parts
a. ________ protein
b. ________ – a light-absorbing molecule made from vitamin __
2. ____________ (iodopsin) in cones also consist of 2 parts
a. ___________ - the same as that found in rhodopsin
b. _____ proteins with different amino acid sequences that allow for 3 types of cones
that absorb light of 3 different wavelengths
C. Photochemical reaction of __________
1. In the ______, retinal has a bent shape called ____-retinal
2. _______ converts the cis-retinal to a straighter shape called ______-retinal, which has
a violet color
3. The conversion of cis-retinal to trans-retinal leads to the production of a visual
_______ signal in the rods and cones
4. Trans-retinal loses its color quickly (___________), then is transported to the pigment
epithelium, reconverted to __-retinal, then transported back to the _______ in the
photoreceptors
D. Light & Dark Adaptation
1. ______ adaptation occurs when you go from darkness into light
a. Pupils __________ to reduce incoming light
b. Rods ______ quickly, and cones take over in about ____ min.
2. _______ adaptation occurs when you go from light to dark
a. Pupils __________ to admit more light into the eye
b. Rhodopsin _____________ faster than it bleaches; rods reach maximum sensitivity
in about ____-___ min.
E. Rod & Cone ___________ are relative to their functions
1. Cones are found predominantly in the retina’s macula ______ and are the only
photoreceptors found in the fovea centralis (________ point)
a. Each cone synapses with ____ bipolar cell, which synapses with ____ ganglionic
cell that sends the image to the brain
b. The one-to-one relationship between the cells produces a ________ color image in
_________ light
2. Rods are __________ throughout the peripheral ________
a. One ganglionic cell can receive input from ________ rods
b. This results in a _______ clear image in ____ light
F. Color Vision is produced by three types of ________
1. ____ cone photopsins absorb orange light wavelengths (___ nm)
2. _____ cone photopsins absorb green light wavelengths (___ nm)
3. _____ cone photopsins absorb blue light wavelengths (____ nm)
4. Perception of different colors is based on a mixture of _______ signals from the three
cone types
8
5. Color _______ is a hereditary condition in which a person lacks one or more
__________ in their cones, resulting in the inability to see certain colors
G. _______________ vision (depth perception) occurs because the visual fields of our two
eyes overlap, allowing each eye to see an object from slightly different angles
H. The ________ projection pathway from photoreceptors to brain
1. _______receptors transmit visual impulses to bipolar cells
2. _________ cells transmit impulses to _____________ cells, the axons of which form
the optic nerves (CN ___)
3. Optic nerves partially cross over at the optic __________, then enter the brain via the
optic ________
4. Most optic tract nerve fibers synapse with neurons in the lateral geniculate nuclei of
the ___________
5. Lateral geniculate neurons form the optic __________ of nerve fibers that transmit
impulses to the visual cortex in the _________ lobes of the brain for interpretation
6. A few optic tract nerve fibers go to the _________ to synapse with the
a. Superior colliculi, which control visual _________ of the extrinsic eye muscles
b. Pretectal nuclei, which are involved in the photo________ and _______________
reflexes