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Special senses and endocrine system

Terms in this set (64)

5 special senses
smell, taste, sight, hearing, equilibrium
smell
the receptors for olfaction, which are bipolar neurons, are in the olfactory epithelium in the superior portion of the nasal cavity
-substances to be smelled must be volatile, water soluble, and lipid soluble
olfactory hairs
site of olfactory transduction (part of the receptor cell dendrite)
olfactory receptors
respond to chemical stimulation of odorant molecule> initiating the olfactory response; from olfactory receptors unmyelinated axons unite to form olfactory nerves> pass through foramina of the cribiform plate of the ethmoid bone> terminate in paired masses of gray matter in brain known as the olfactory bulbs> axons of olfactory bulbs extend posteriorly to form the olfactory tract> to various parts of the brain (including the limbic system> emotional aspects of odors)
3 types of cells that form the olfactory epithelium
1. olfactory receptors
2. supporting cells
3. basal cells
olfactory receptors
bipolar neurons with a knob-like dendrite at the distal end
supporting cells
columnar cells in the mucous membrane lining the nose
basal cells
produce new olfactory receptors (1 month life span)
-an exception to the rule that in the nervous system neurons are not replaced
-subject to damage due to contact with outside environment; we lose about 1% of olfactory receptors each year
-undergo sensory adaptation fairly quickly
- threshold of smell is low; therefore only a few molecules of certain substances need to be present in air to be smelled
olfactory glands
located in the connective tissue that anchors the olfactory epithelium
-produce mucus
-moisten surface of olfactory epithelium
-dissolve odorant gasses
gustation
taste; a chemical sense
-taste of a particular chemical can be detected only when the chemical is dissolved in the watery fluid (supplied by the salivary glands) surrounding the taste buds
taste buds
approximately 10,000 located on the tongue, soft palate, pharynx, and larynx
-oval body composed of 3 types of epithelial cells:
supporting cells
gustatory receptor cells
basal cells
supporting cells (taste)
form capsule containing approximately 50 receptor cells
gustatory receptor cells
contain projection known as gustatory hair which projects through taste pore to external surface
basal cells (taste)
produce supporting cells which develop into gustatory receptor cells (lifespan about 10 days)
papillae
elevations in the upper surface of the tongue that contain the taste buds
5 primary taste sensations
sweet sour salty bitter umami
-all other taste are combinations
3 cranial nerves supply pathway for taste
VII- anterior 2/3 of the tongue
IX- posterior 1/3 of the tongue
X- throat and epiglottis area
taste impulses
travel along 3 cranial nerves > medulla oblongata> limbic system and hypothalamus and thalamus> primary gustatory area in the parietal lobe of the cerebral cortex (conscious perception of taste)
hearing and equilibrium
-receptors for both hearing and equilibrium are located in the ear
-the ear is composed of 3 regions : external ear, middle ear, and inner ear
external ear
collects sound waves and directs them inward
consists of: auricle, helix, lobule, external acoustic meatus, tympanic membrane, ceruminous glands, perforated tympanic membrane
auricle
flap of elastic cartilage covered by skin
helix
rim
lobule
inferior portion
external acoustic meatus
curved tube about 1 inch long; located in the temporal bone; leads from the auricle to the tympanic membrane
tympanic membrane
(eardrum) semi transparent partition between external auditory meatus and the middle ear
ceruminous gland
located in the external auditory meatus
-secrete cerumen (earwax) to help prevent dust and foreign objects from entering the ear; may become impacted
perforated tympanic membrane
hole that reduces sound transmission> may require surgery
middle ear
(AKA tympanic cavity) small, air filled cavity in the temporal bone lined by epithelium
-composed of the tympanic membrane, auditory ossicles, the oval window, and the round window
-separated from the external ear by the tympanic membrane
-separated from the inner ear by the boney partition which contains two membrane-covered openings: round and oval windows
tympanic antrum
air space in the posterior aspect of the middle ear that leads to the mastoid air cells; (middle ear infections can spread to the temporal bone or brain)
auditory tube
opening located in the anterior wall of the middle ear leading directly to the nasopharynx; normally closed in the medial aspect; open during swallowing or yawning for pressure equalization between both sides of the tympanic membrane;this is necessary for normal hearing (altitude changes demonstrate function of the auditory tube) it is also a route for pathogens from the nose and throat to the middle ear
auditory ossicles
three tiny bones attached to the wall of the tympanic cavity which form bridge connecting the tympanic membrane to the inner ear; transmit vibrations
malleus
attached to the tympanic membrane; vibrations of the tympanic membrane cause malleus to vibrate
incus
caused to vibrate by malleus; passes the vibration to the stapes
stapes
held by annular ligaments to an opening in the wall of the tympanic cavity called the oval window; vibrations of the stapes act like a piston at the oval window which cause motion of the fluid within the inner ear
ossicles
form a lever system that helps increase the force of the vibrations as they are passed from the tympanic membrane to the oval window
-the vibrations are passed from a relatively large tympanic membrane surface to a smaller oval window concentrating the vibration force and increasing approximately 22x greater; the pressure applied to the oval window is about 22x greater than exerted on the tympanic membrane by sound waves
-CONNECTED BY SYNOVIAL JOINTS
tensor tympani
originates of the cartilaginous part of the auditory tube and the greater wing of the sphenoid bone> inserts on the medial surface of the malleus; contraction pulls the malleus inward thereby limiting movement and increasing tension on the tympanic membrane to prevent damage to the inner ear by loud noises
stapedius
originates from a pyramid (on the posterior walll of the inner ear) and inserts into the neck of the stapes: pulls the stapes outward: helps to check large vibrations resulting form loud noises
tensor tympani and stapedius
these two muscles are the effectors of the tympanic reflex which is elicited by loud noises; loud noises cause these two muscles to contract, moving and partially immobilizing the malleus and stapes causing the bridge of ossicles in the middle ear to become rigid, thus lowering the effectiveness in transmitting vibrations to the inner ear
inner ear
AKA the labyrinth because of its complicated series of canals; it consists of two divisions: an outer bony labyrinth that encloses an inner membranous labyrinth
bony labyrinth
series of cavities in the petrous portion of the temporal bone; 3 areas include the semicircular canals and the vestibule, both of which contain receptors for equilibrium, and the cochlea, which contains receptors for hearing
- it is lined with periosteum and contains a fluid called perilymph; chemically similar to CSF (surrounds the membranous labyrinth)
membranous labyrinth
series of sacs and tubes lying inside and having the same general form as the bony labyrinth
-contains endolymph (chemically similar to intracellular fluid) it is lined with epithelium
vestibule
the central oval portion of the bony labyrinth; the membranous labyrinth in the vestibule consists of two sacs known as the utricle and saccule
-projecting upward and posteriorly from the vestibule are the three bony semicircular canals, each arranged at right angles to the other two
-the anterior and posterior canals are oriented vertically; the lateral canal is oriented horizontally
-one end of each canal has an enlargement known as the ampulla
-the portion of the membranous labyrinth that lies inside the semicircular canal is known as the semicircular ducts
cochlea
lies anterior to the vestibule; consists of a bony spiral canal that makes almost 3 turns around a central bony core known as the modiolus
-cross section of the cochlea demonstrates division into 3 channels by partitions which have the shape of the letter Y
scala vestibuli
channel above the bony partition- ends at the oval window
contains perilymph
scala tympani
channel below the bony partition -ends at the round window contains perilymph
helicotrema
opening of the apex of the cochlea
scala media
cochlear duct; between the wings of the Y
vestibular membrane
separates the cochlear duct from the scala vestibuli
basilar membrane
separates the cochlear duct from the scala tympani
spiral organ
(organ of corti) organ of hearing, rests on the basilar membrane; coiled sheaths of epithelial cells, supporting cells, and about 16,00 hair cells; receptors for auditory sensations
inner hair cells
medially placed on a single row; extend the entire length of the cochlea
outer hair cells
arranged in several rows; have specialized microvilli at the apical ends which extend into the endolymph of the cochlear duct ; basal ends of these hair cells synapse with fibers of the cochlear nerve
tectorial membrane
attached to the bony shelf of the cochlea; passes like a roof over the receptor cells making contact with the tips of their hairs; delicate and flexible
sound waves
result from the alternate compression and decompression of air molecules; sound most frequently heard by humans are from sources that vibrate at frequencies between 500-5000 Hz
pitch
frequency of sound vibration
loudness
intensity (size) of vibration; measured in decibels
events involved in hearing
1. sound waves enter the external auditory meatus
2. waves of changing pressures causes the eardrum to reproduce the vibrations coming from the sound wave source
3. auditory ossicles amplify and transmit vibrations to the perilymph in the scala vestibuli
5. vibrations pass through the vestibular membrane and enter the endolymph of the cochlear duct
6.different frequencies of vibration in endolymph stimulate different sets of receptor cells

**differences in pitch are related to differences in the width and stiffness of the basilar membrane and sound waves of various frequencies cause specific regions of the basilar membrane to vibrate more intensely than others

7.a receptor cell becomes depolarized; its membrane becomes more permeable to Ca ions
8. in the presence of Ca ions, vesicles at the base of the receptor cell release neurotransmitter
9. neurotransmitter stimulates the ends of nearby sensory neurons
10. sensory neurons are triggered on fibers of the cochlear nerve
11. the auditory cortex of the temporal lobe interprets the sensory impulses
base of the cochlea
where high frequency and or high pitched sounds cause the basilar membrane to vibrate
apex of the cochlea
where low frequency or low pitched sounds cause the basilar membrane to vibrate
equilibrium
5 mechanisms for equilibrium on each side of the head
two senses- static and dynamic
-organs associated with static equilibrium functions to sense the position of the head with respect to the force of gravity when still
-when the head and body are suddenly moved or rotated, the organs for dynamic equilibrium detect such motion and aid in maintaining balance
vestibular apparatus
collective term for receptor organs involved in detecting equilibrium
-utricle, saccule, and semicircular canals
vestibule
a bony chamber between the semicircular canals and the cochlea; the membranous labyrinth inside the vestibule consists of 2 expanded chambers; the utricle and the saccule
-utricle and saccule: detect linear acceleration
-utricle: detects forward acceleration
-saccule: detects vertical acceleration
-the anterior and posterior canals are oriented vertically ; the lateral canal is oriented horizontally
-one end of each canal has an enlargement known as the ampulla
-the portion of the membranous labyrinth inside the semicircular canals is the semicircular ducts
macula
- a small patch of hair cells and supporting cells located in each chamber when the head is upright, the hair cells of the macula in the utricle project vertically those in the saccule project horizontally; both are in contact with a sheet of gelatinous material known as the otolithic membrane
Otolythic Membrane
contains crystals of calcium carbonate embedded in its surface; increasing the weight of the gelatinous sheet making it more responsive to change in position; the hair cells swerve as sensory receptors and have nerve fibers attached to their bases; associated with the vestibular nerve
-movement of the head the membrane to shift stimulating the hair cells, signalling a nerve impulse
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