This document provides information on sensory receptors and the structures involved in the special senses of smell, taste, hearing, and balance. It discusses the main types of sensory receptors, including mechanoreceptors, photoreceptors, chemoreceptors, thermoreceptors, and nociceptors. It then describes the structures of sensory organs like muscle spindles, Meissner corpuscles, Pacinian corpuscles, Merkel disks, and Golgi tendon organs. The following sections focus on the special senses, outlining the neural pathways and mechanisms of smell, taste, hearing, and the roles of the inner ear in balance.

1. Anatomy and Physiology Times
Does that make Sense?
NOVEMBER 5, 2012 VOLUME 1, ISSUE 1
Sensory Receptors: Stimulus Detected Table of Contents
Mechanoreceptors:  Page 1
Photoreceptors: found activated when Located internally often
Sensory Receptors
only in the eye. Respond “deformed” to generate within body organs or
to light stimuli, if the receptor potential. viscera.
intensity is great enough  First Story
Example: Pressure ap-
to generate a receptor plied to the skin. (1) Proprioceptors: is a spe- Stimulus Detected
potential. (478) cialized type of viscero-
Examples: Eye (1) (478) ceptors. Located in the  Secondary News
Chemoreceptors: acti- skeletal muscles, joint
Exteroceptors: on or capsules and tendons . Structure
vated by amount or
near body surface, often changing concentration Provide info on body
called cutaneous recep- of certain chemicals. movement, orientation  Page 2
tors. Example: taste and smell in space and muscle Special Sense
Examples: pressure, (1) (478) stretch. There are tonic
touch, pain and temp (1) and phasic receptors  Smell
(478) Thermoreceptors: acti- provide positional infor-
mation on body or body
Visceroceptors: Provide
vated by changes in tem-
parts while at rest or  Taste
perature (1) (478)
the body with infor- during movement.
mation about internal Nociceptors: activated  Hearing
environment ,pressure, by intense stimuli that
stretch, chemical chang- may damage tissue sen-  Balance
es, hunger and thirst. sation produced in pain
Examples: Light and
sound (1) (478)
Structure
Muscle Spindle- It is contained basal cells where axon terminals trical potential. Free Nerve Endings: Are Within the Epidermis,
within a capsule lying parallel and laminar cells are interdigitat- commecning with the hair papilla in the same depth of the pacinian
to muscle fibers. (1) Intramural ed with the basal cells. Each corpuscle going further up attaching to the erector muscle. Above the
fibers are that inside the cap- axon; the terminated and those nerve ending is the skin papilla lying on the dermis layer of the skin.
sule where in-between them is in contact with epidermis con- root hair plexuses: the root hair plexuses constists of the lowest papilla,
a central region, wrapped tain mitochondria, micro vesicles where the root of the hair lies above, then on the inner root sheath
within sensory dendrites of the and myelinated dense bodies. (1) connective tissue sheath runs over it and muscle arrecteur pili is at the
muscle spindle afferent. (1) Pacinian Corpuscles: Within the top. underneath the epidermis is the sebaceous gland and at the visible
Then there is an ion channel in corpuscles there is a structure sight is the hair shaft. (1)
the sensory dendrites for called the first node of Ranvier.
whenever the muscle length- Myelin Sheath as well commenc- merkel disks: the structure of the merkel disks would consist of that as
ens (is being stretched). Those es in this area, conducting elec- to the fingertips, the epidermis the highest level of the skin to the fact
ions cause a potential reaction trical impulses relatively quickly. that the function is touch. (1)
in the action potentials of Nodes of Ranvier are present Golgi tendon Organs: Within the central nervous system, the Golgi
muscle spindle afferents. (1) through out the entire area tendon is made up of motor neurons, to where the organ monitors
Meissner Corpuscles- Upper extending from the sensory muscular and tendon tension from surrounding tissues. (1)
portion of corpuscle is in direct receptor, allowing the nodes to
contact with the epidermal rapidly transmit changes in elec-

2. DOES THAT MAKE SENSE? Page 2
Structure Continued...
of Ranvier. Withing the Epidermis, then on the inner root sheath
commecning with the hair
Myelin Sheath well com- connective tissue sheath runs
papilla in the same depth of
mences in this area, con- over it and muscle arrecteur
the pacinian corpuscle
ducting electrical impulses pili is at the top. underneath
relatively quickly. going further up attaching to the epidermis is the seba-
the erector muscle. Above ceous gland and at the visible
Nodes of Ranvier are present the nerve ending is the skin sight is the hair shaft
through out the entire area papilla lying on the dermis
extending from the sensory layer of the skin.
receptor, allowing the nodes
merkel disks: the structure of
to rapidly transmit changes in
the merkel disks would con-
electrical potential.
root hair plexuses: the root sist of that as to the finger-
hair plexuses constists of the tips, the epidermis the high-
lowest papilla, where the est level of the skin to the
Free Nerve Endings: Are root of the hair lies above, fact that the function is touch
EXTRA! EXTRA! READ ALL ABOUT THE SPECIAL SENCES
What are Special Senses?
Special Senses are characterized by receptors grouped closely together or grouped in spe-
cialized organs; sense of smell, taste, hearing, equilibrium, and vision.
SMELL:
Olfactory Receptors
epithelium stimulate the olfactory cell.
Olfactory sense organs consist of
Olfactory Epithelium- located in most superior portion of the
epithelial support cells and
nasal cavity
specialized olfactory receptor
Olfactory Receptors- extremely sensitive and easily fatigued
neurons
Olfactory Cilia- located on the Olfactory Pathways
olfactory receptor neu-
When the level of SMELL odor- producing chemicals reaches a
rons that touch the olfac-
threshold level, the following occurs
tory epithelium lining the
Receptor potential, and then action potential, is generated and
upper surface of the nasal
passed to the olfactory nerves in the olfactory bulb
cavity.
The impulse then passes through the olfactory tract and into
Olfactory Cells- chemorecep-
the thalamic and olfactory centers of the brain for inter-
tors; gas molecules or
pretation, integration, and memory storage
chemicals dissolved in the
mucus covering the nasal

3. Page 3 VOLUME 1, ISSUE 1
Taste:
Taste Buds- sense organs that (1) chemicals in the saliva Adaptation and sensitivity thresh- Nerve impulses from the
respond to gustatory, or taste, Taste buds are similar in struc- olds are different for each of anterior two thirds of the
stimuli; associated with papillae ture; functionally, each taste the primary taste sensations
tongue travel dover the
bud responds most effec- (1)
Chemoreceptors that are facial nerve; those from
stimulated by chem- Neural the posterior one-third of
icals dissolved in the Pathway- the tongue travel over
saliva (1) taste the glossopharyngeal
Gustatory cells special- sensation nerve; vagus nerve plays
ized cells in taste begins a minor role in taste.
buds; gustatory with a Nerve impulses are
hairs extend from receptor carried to the medulla
each other into the potential oblongata, relayed into
taste pores (1) in the the thalamus and then
Sense of taste depends on the gustatory cells of a taste bud; into the gustatory area of
tively to one of four primary
creation of a receptor po- generation and propagation of an the cerebral cortex in the
taste sensations: sour, sweet,
tential in gustatory cells action potential then transmits parietal lobe of the brain.
bitter, and salty(1)
because of taste-producing the sensory input to the brain.(1) (1)
Hearing:
Neural Pathway of hearing– a move- External ear is divided into two divi- The inner ear has a variety of struc-
ment of hair cells against the tectorial sions. Auricle or pinna which is the tures that consist of the a bony laby-
membrane stimulates the dendrites visible portion. The external auditory rinth, a membrane labyrinth, the vesti-
that terminate around the base of the meatus is the tube leading from the bule and semicircular canals which are
hair cells and initiates impulse conduc- auricle into the temporal bone and involved with balance, the cochlea, the
tion by the cocniear nerve to the brain- ending at the tympanic membrane. (1) end lymph and the perilymph (1)
stem. The impulses pass through “relay
stations” in the nuclei in the medulla, Middle Ear has tiny epithelium which
pons, midbrain and thalamus before is lined cavity hollowed out of the
reaching the auditory are of the tem- temporal lobe. It also contain 3 audito-
poral lobe.(1) ry ossicles the malleolus (hammer),
incus (anvil), and stapes (stirrup). (1)
Mechanisms of Hearing
Balance:
Sense of balance- related to head posi-
Static equilibrium is the abil- tion and deceleration
ity to sense the position Otoliths are located with-
of the head relative to in the matrix of the
gravity or to sense accel- macula
eration or deceleration Dynamic Equilibrium- needed
Movements of the macu- to maintain to balance when
la, located in both the head or body is rotated or
the utricle and sac- suddenly moved; able to de-
cule almost right tect changes in direction and
angles to each other, rate at which movement oc-
provide information curs (1)