Module 06: Special Senses Flashcards
This are the means by which the brain receives information about the environment and the body.
Senses
This is the process initiated by stimulating sensory receptors.
Sensation
This pertains to the conscious awareness of those stimuli received by the sensory neurons.
Perception
How does the brain receive stimuli?
Sensory receptors respond to stimuli by generating action potentials that are propagated to the spinal cord the brain. Perception results when action potentials reach the cerebral cortex.
What are the characteristics of a sensation?
(1) Projection - area
(2) Intensity - degree
(3) Contrast - effect of a previous sensation to the current one
(4) Adaptation - becoming aware of continuing stimulus
(5) After Image - the sensation remains in the consciousness
This characteristic of the sensation pertains to how the sensation comes from the area where the receptors where stimulated, even though it is the brain that truly feels the sensation.
Projection
This characteristic of sensation pertains to the degree to which the sensation is felt; a strong stimulus affects more receptors and more impulses are sent to the brain.
intensity
This characteristic of sensation pertains to the effect of the previous or simultaneous sensation on a current sensation as the brain compares them.
Contrast
This characteristic of the brain pertains on becoming aware of the continuing stimulus. If the stimulus remains constant, there is no change for the receptors to detect.
Adaptation
This characteristic of the sensation pertains as to how the sensation remains in the consciousness after the stimulus has stopped.
After image
What are the two basic groups of senses?
(1) General senses
(2) Specific Senses
These senses have receptors distributed over a large part of the body that can sense touch, pressure, pain, temperature, and itch.
General Senses
These forms of general senses provide information about body and environment
Somatic Senses
These form of general senses provide information about internal organs, primarily involving pain and pressure.
Visceral Senses
These receptors are more specialized in structure and are localized to specific parts of the body. These include (1) Smell (olfaction), (2) taste, (3) vision, (4) hearing, and (5) Balance
Special Senses
What are the general senses?
(1) Touch
(2) Pressure
(3) Pain
(4) temperature
(5) Vibration
(6) Itch
(7) Proprioception
This sense pertains to the sense of movement and the position of the body.
Proprioception
These are sensory nerve endings or specialized cells respond to stimuli by developing action potentials.
Sensory receptors
These respond to mechanical stimuli , such as the bending or stretching of receptors (these detect movement).
Mechanoreceptors
These respond to chemicals. For example odor molecules binding to chemoreceptors, allowing us to perceive smells.
Chemoreceptors
These respond to light
Photoreceptors
These respond to temperature changes.
Thermoreceptors
These respond to stimuli that result in the sensation of pain
Nociceptors
These are the simples and most common type of sensory receptors and is relatively unspecialized neuronal branches to dendrites and is distributed to almost all parts of the body.
Free nerve endings
Free nerve endings can detect what?
(1) painful stimuli
(2) temperature
(3) itch
(4) movement
These are receptors that respond to decreasing temperatures but stop responding at temperatures below 12 degrees C (54F)
Cold receptors
These are receptors that respond to increasing temperatures but stop responding at temperatures above 47 degrees C (117F)
Warm receptors
In what temperature levels are pain receptors stimulated?
below 12 degrees Celsius or above 47 degrees Celsius
These are small, superficial nerve endings involved in detecting light touch and superficial pressure.
Merkel’s disk
These are associated with hairs and are also involved in detecting light touch.
Hair follicle receptors
These are very sensitive but not very discriminative, meaning that the point being touched cannot solely be precisely located.
Light touch receptors
These are receptors for fine, discriminative touch, just located deep into the epidermis, These receptors are very specific in localizing tactile sensations.
Meissner corpuscle
These are deeper tactile receptors and play an important role in detecting continuous pressure in the skin.
Ruffini corpuscle
These are the deepest receptors and are associated with tendons and joints. These receptors relay information concerning deep pressure, vibration, and position (proprioreception).
Pacinian corpuscle
Why is our proprioreception important?
(1) maintain postures
(2) perform daily bodily movements
How are proprioceptive information conveyed?
not only to our cerebrum (conscious awareness of our body position), but also different parts like the cerebellum
This enables us to maintain an upright position, even if our body is in an uneven ground.
righting reflex
This is characterized as an unpleasant perceptual and emotional experience. It can either be localized or diffused.
Pain
This kind of pain involves sharp, pricking, or cutting pain resulting from rapid conducted action potentials.
Localized pain
This kind of pain involves burning or aching paid resulting from action potentials that are propagated more slowly.
Diffusing pain
These are highly localized as a result of the simultaneous simulation of pain receptors and tactile receptors
Superficial pain sensations
These are not highly localized because of the absence of tactile receptors in the deeper structures. And are usually perceived as diffused pain.
Deep or visceral pain
This suppresses action potentials from pain receptors in local areas of the body through the injection of chemical anesthetics near a sensory receptor or nerve.
Local anesthesia
This is a treatment where chemical anesthetics affect reticular activating system or reticular formation. It is also associated with the loss of consciousness.
General anesthesia
How are pain sensations be influenced by inherent control?
Sensory neuros associated with tactile receptors are linked to the pain sensory pathway to the CNS. Therefore, stimulation of these tactile receptors can result to decreased perception of pain.
This is perceived to originate in a region of the body that it is not the source of the pain stimulus. This is also a visceral pain that is felt as a cutaneous pain.
Referred pain
When is referred pain felt?
Felt when internal organs are damages or inflamed
What causes referred pain?
When sensory neurons from the superficial area and the neurons of the source pain (visceral area) converge onto the same ascending neurons of the spinal cord
In terms of referred pain, this is referred to as the most superficial structures innervated, such as the skin.
painful sensation
What are the areas of referred pain?
(1) Liver and gallbladder
(2) Esophagus
(3) Kidney
(4) Appendix
(6) Urinary Bladder
(7) Lung and diaphragm
(8) Heart
(9) Stomach
(10) Colon
(11) Ureter
This is defined as the sense of smell and occurs as a response to airborne molecules.
Olfaction
These are airborne molecules to which the sense of olfaction respond to.
Odorants
These are bipolar neurons within the olfactory epithelium.
Olfactory Neurons
These lines the superior part of the nasal cavity.
Olfactory Epithelium
These are part of the olfactory neurons which extends in the epithelial surface.
Dendrites
These are the ends of the dendrites, which are long that lie in a thin mucous film located on the epithelial surface.
Cilia
This keeps the nasal epithelium moist, traps, and dissolves airborne molecules, and facilitates the removal of molecules and particles from the nasal epithelium.
Mucus
What happens to airborne odorants in the olfactory>
Airborne odorants become dissolved by the mucus on the surface of the epithelium and binds to the receptor molecules on the membranes of the specialized cilia. The binding of the odorant to the receptor then initiates action potentials that are conducted to the olfactory cortex of the cerebrum by the sensory neurons.
How much estimated functional olfactory neurons are found in the body?
400
How much estimated smells can be detected by the olfactory?
10,000
What happens to a receptor when it binds to an odorant?
it becomes desensitized and does not respond to another odor molecule for some time, which helps in the adaptation to a particular color (threshold for detecting odors is small=few olfactory neurons can initiate an action potential)
These carry action potentials from the olfactory neurons to the cerebrum that allow for perception and interpretation of stimuli.
Neuronal pathways of olfaction
These from the olfactory neurons form the olfactory nerves (cranial nerve 1), which pass through the foramina of the cribriform plate and enter the olfactory nerve.
Axons
This is where the new action potentials relayed from the synapsis of olfactory neurons and interneurons pass to the brain.
Olfactory Tracts
This is where the axons pass through and is known to be beside the foramina of the cribriform plate.
Olfactory bulb
Each olfactory tract terminates in an area of the brain called the _________________, which is located in the frontal and temporal lobes. And is involved in both the conscious perception of smell and the visceral and emotional reactions that are often linked to odors.
Olfactory Cortex
How is the olfaction relayed?
It is relayed through the cerebral cortex first and not the thalamus, this is the reflection of the older and more primitive origin of the olfactory cortex.
These are found in the olfactory cortex and olfactory bulb that tends to inhibit transmission of action potentials resulting from prolonged exposure to given odorants.
Feedback loops
How does the feedback help in adaptation?
The feedback plus the temporary decreased activity at the level of the receptors results in adaptation.
Explain the olfaction process
(1) Nasal cavity contains a thin film of mucous where odors become dissolved
(2) Olfactory neurons are located in the mucous. Dendrites of olfactory neurons are enlarged and contain cilia
(3) The dendrites pick up odor, depolarize and carry odor to axons in the olfactory bulb
(4) frontal and temporal lobes process odors
These are sensory structures that detect taste stimuli. These are also characterized as oval structures that are located on the surface of certain papillae (nipples).
Taste buds
These are enlargements on the surface of the tongue that contain the taste buds.
papillae (nipples).
This is known as the root of the mouth
Palate
What are the two cells that form the taste bud?
(1) Special epithelial cells
(2) 40 taste cells (interior portion)
These form the exterior supporting capsule of each taste bud.
Special epithelial cells
These are found in taste cells and are characterized as hair like processes that extend through a tiny opening in the surrounding stratified epithelium (taste pore)
Taste Hairs
This is known as the tiny opening in the surrounding stratified epithelium.
Taste Pore
How does taste sensation initiate action potentials?
Dissolved molecules or ions bind to the receptors on the taste hair and initiate action potentials, which sensory neurons carry to the insula of the cerebral cortex.
Taste sensations are divided into five basic types which are:
(1) sour
(2) salty
(3) bitter
(4) sweet
(5) umami
How does heat damages affect epithelial tissues?
Heat damage can cause injury to the tongue epithelial tissue or even death of the cells, including taste cells in the taste buds. If the epithelial cells are only damages, sensation can return within a few hours to a few days, but if they die, it takes about 2 weeks to be replaced.
What are the three cranial nerves that carry taste sensations to the brain?
(1) Facial nerve (VII)
(2) Glossopharyngeal nerve (IX)
(3) Vagus nerve (X)
This cranial nerve transmits taste sensations from the anterior two-thirds of the tongue.
Facial nerve (VII)
This cranial nerve carries taste sensation from the posterior one-thirds of the tongue.
Glossopharyngeal nerve (IX)
This cranial nerve carries taste sensations from the root of the tongue.
Vagus nerve (X)
How are taste sensations carried to the brain?
Taste buds to the tractus solitarius of the medulla oblangata. Axons from in the three cranial nerves synapse in the gustatory portion of the brainstem nuclei. Axons from the neurons in these brainstem nuclei extend and synapse with the interneurons in the thalamus. Axons from the neurons in the thalamus project to the taste area in the insula of the cerebrum.
What does the visual system include?
(1) eyes
(2) accessory structures
(3) sensory neurons
These are bony cavities that houses the eyes
Orbits
These includes information about light and dark, movement and color. It begins as actions potentials originating from the eyes.
Visual Input
These protects, lubricates, and moves the eyes. They include the eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles.
Accessory Structures
These protect the eyes by preventing perspiration from running down the forehead into the eyes, causing irritation. They also help shade the eyes from direct sunlight.
Eyebrows
These are associated with lashes and protects the eyes from foreign objects.
Eyelids
This refers to when an object suddenly approaches the eye, the eyelids protect the eye by closing then opening quite rapidly.
Blink reflex
How often does blinking occur?
20 times per minute (which lubricates the eyes by spreading tears over the surface)
This is a thin, transparent mucous membrane covering the inner surface of the eyelids and the anterior surface of the eye.
Conjunctiva
These primarily help in lubricating the eyes.
Conjunctive secretions
This is inflammation of the conjunctiva.
Conjunctivitis
This consists of a lacrimal gland situated in the superior lateral corner of the orbit and a nasolacrimal duct and associated in the inferior medial corner of the orbit.
Lacrimal Apparatus
This is the structure in eye that excretes fluid that we call tears, which passes through the anterior surface of the eye.
Lacrimal gland
These are small ducts where the excess tears are collected in the medial angle of the eyes.
Lacrimal Canaliculi
This is where the canaliculi opens into, which is an enlargement of the nasolacrimal duct.
Lacrimal sac
This is where tears pass through into the nasal cavity.
Nasocrimal duct.
Why are tears important?
Tears lubricate and cleans the eye and they are also composed of enzymes that helps combat eye infections.
What are the extrinsic eye muscles that are responsible to the movement of each eyeball.
(1) The superior, inferior, medial, and lateral rectus muscles
(2) The superior and inferior oblique muscles
These are muscles that run more or less straight from their origins in the posterior portion of the orbit to their insertion sites on the eye and are attached to the four quadrants of the eyeballs.
The superior, inferior, medial, and lateral rectus muscles
These extrinsic eye muscles are located at an angle to the long axis of the eyeball.
The superior and inferior oblique muscles
This is a hollow-fluid-filled sphere.
Eyeball
This is what you call the three tissue layers that comprise the wall of the eyeball.
Tunics
What are the three tunics and what do they contain?
(1) Fibrous tunic: sclera and cornea
(2) Vascular tunic: choroid, ciliary body, and iris
(3) Nervous tunic: Retina
This is the firm, white, outer connective tissue layer of the posterior five-sixths of the fibrous tunic. This helps maintain the shape of the eye, and protects the internal structures, as well as provides attachment for the extrinsic eye muscles.
Sclera
The sclera is also known as what?
White of the eye
This is the transparent anterior sixth of the eye, which permits light to enter. it is a part of the focusing system of the eye, and helps in bending or refracting the entering light.
Cornea
Why is the middle tunic known as the vascular tunic?
This is because is contains most of the blood vessels of the eyes.
This is the posterior portion of the vascular tonic that is associated with the sclera. It is a very thin structure consisting of a vascular network and melanin containing pigment cells that causes it to appear black.
Choroid
What does the cornea do?
it absorbs light to prevent it from being reflected because reflection of the light can interfere with vision
This is continuous with the anterior margin of the choroid.
Ciliary Body
These are smooth muscles within the ciliary body, which attach to the perimeter of the lens by suspensory ligaments .
Ciliary Muscles
This is the flexible, biconvex, transparent disc.
Lens
This is the colored part of the eye, This is attached to the anterior margin of the ciliary body anterior to the lens.
Iris
The iris is a contractile structure consisting of mainly smooth muscle surrounding an opening called the “______________”
Pupil (Lots of light - constricted, little light - dilated)
What is the relationship between the eye and the pupil?
Light passes through the pupil and the iris regulates the diameter of the pupil, which controls the amount of light entering the eye.
This causes the circular smooth muscles of the iris to contract and constrict the pupil. In this as the light intensity increases, the pupil constricts
Parasympathetic stimulation from the oculomotor nerve (circular smooth muscles)
This causes the radial smooth muscles of the iris to contract and dilate the pupil. In this, as the light intensity decreases, the pupil dilates.
Sympathetic stimulation (radial smooth muscles)
What is the relationship between the tension and ciliary muscles?
The contraction and relaxation of the ciliary muscles adjust the tension in the sensory ligaments attached to the lens. Therefore, alterations in tension and change the shape of the lens.
This is known as the innermost tunic of the eye.
Nervous tunic
This is part of the nervous tunic and is in charge of covering the posterior five-sixths of the eye and is composed of two parts, namely: outer pigmented and inner sensory,
Retina
This type of retina along with the choroid keeps light from being reflected back into the eye.
Outer pigmented retina
This type of retina contains photoreceptor cells.
Inner sensory retina
These are 20 times more common than cones and can function in dim light because they are very sensitive, meaning they require lower levels of light to be stimulated; however, they do not provide color vision as photoreceptor cells.
Rods
These photoreceptor cells require more light and they do provide color vision and has three different types of cones, that are each sensitive to a different color.
Cones
What are the three different types of cones that are each sensitive to a different color.
blue, green, or red
When the posterior region of the retina is examined with an ophthalmoscope, what are the two major features that can be observed?
(1) Macula
(2) Optic disc
This is a small spot near the center of the posterior retina and contains the fovea centralis.
Macula
This is the part of the retina where light is most focused when the eye is directly looking an object. It contains only one cone cells and the cells are more tightly packed there than anywhere else in the retina. This is the region with the greatest ability to discriminate fine images, which explains why objects are best seen ahead.
Fovea Centralis
This is the white spot just medial to the macula through which a number of blood vessels enter the eye and spread over the surface of the retina. This is also the spot at which axons from the retina meet and pass through the two outer tunics, and exit the eye as an optic nerve.
Optic disc
Why is the optic disc known as the blind spot of the eye.
It contains no photoreceptors and does not respond to light
Where is the anterior and posterior chambers located?
(The anterior and posterior chambers are located between the cornea and the lens and is divided by the iris, which is continuous to the pupils)
What are the three (3) chambers or areas of the interior of the eyeball?
(1) anterior chamber
(2) posterior chamber
(3) Vitreous chamber
This is the much larger chamber that is posterior to the lens and in the retina region.
Vitreous chamber
What is the function of the anterior and posterior chambers of the eyeball?
These are filled with aqueous humor (watery fluid) that helps maintain pressure within the eye, refracts light, and provides inner surface of the ey e.
This is produced by the ciliary body as a blood filtrate and is returned to the blood through the venous ring that surrounds the cornea.
aqueous humor (watery fluid)
What happens when the aqueous humor cannot return to the blood?
It keeps the eye inflated, but if the flow from the eye through the venous ring is blocked, the pressure of the increases resulting to glaucoma.
This is a condition that can eventually lead to blindness because fluid compresses the retina, thereby restricting the blood flow through it.
Glaucoma
This is a transparent jellylike substances that helps maintain pressure within the eye and holds the lens and the retina in place. it also refracts like and does not circulate.
Vitreous fluid
What are the basic life processes involved in vision?
(1) The pupil allows light into the eye, which is focused by the cornea, lens, and humors onto the retina
(2) The light striking the photoreceptors of the retina produces action potentials within the visual pathway
(3) The optic nerve conveys these action potentials to the brain where perception then occurs
How does refraction occur?
When light passes from air to some other, denser transparent substance,
When is light bended?
When the surface of the lens are concave
When do light rays converge?
When the surface of the lens is convex, like the outer surface of the cornea. (And when they converge, they reach a point wherein they cross called the focal point) - focusing - causes the light to converge
This is known as the crossing point and occurs just anterior to the retina and the tiny image that is focused on the retina is inverted compared to the actual object.
Focal point
What happens when there is distant vision?
Ciliary muscles in the ciliary body are relaxed. Tension in suspensory ligaments is high and they maintain elastic pressure of the perimeter of the lens and the lens are flattened which allows distant vision.
What happens when there is near vision?
Ciliary muscles in the ciliary body contract due to parasympathetic stimulation, moving ciliary body towards the lens. Tension in suspensory ligaments is low. The lens will be more convex and has a spherical form because of its own elastic nature (20 feet or 6 1/2 meters)
Where does the greatest amount of convergence occur?
Convergence occur because of the convex structure of the cornea. It also occurs when light passes through the aqueous and vitreous humor as well as the lens. The greatest amount of convergence occurs in the greatest contrast of media density between the air and the cornea.
note that fine adjustments can solely occur due to the change in the lens shape.
This is the process of changing the shape of the lens and it enables the eyes to focus on images closer than 20 feet of the eye.
Accommodation (Can be lost as we age due to the reduced flexibility and the ability of the lens to change shape)
What does it mean when a person has 20/20 vision and 20/40 vision?
The person can see at 20 feet what people with normal vision see at 20 feet (20/20). The person can see at 20 feet of the line what normal vision see at 40 feet (20/40).
These are specialized cells that allow for the process of vision. The outer segments of these are modified by numerous folding of the cell membrane to form discs.
Photoreceptors.
These are photosensitive pigment within rod photoreceptors that interacts with the light and causes action potentials in the retina.
Rhodopsin
This is the protein within Rhodopsin
Opsin
This is the loosely bounded yellow pigment within Rhodopsin. Its manufacture requires vitamin A.
Retinal
How does light affect rhodopsin?
(1) Prior to light exposure, a rhodopsin molecule is intact, with the opsin and retinal combined.
(2) When exposed to light, the retinal changes shape, which then changes the activity of the entire rhodopsin molecule
(3) This change in rhodopsin stimulates a response in the rods, resulting in vision
(4) Retinal completely detaches from the opsin
This is the most common symptom of mitochondrial diseases and is known as the absence of perception of one or more colors
Color blindness
When does color blindness usually occur?
Most forms of color blindness typically happen in males and are x-linked genetic traits. About 8% of all males and 1% of females have this in western Europe.
What happens to the rhodopsin in bright light?
In bright light, much of the rhodopsin in the rods is disassociated (opsin and retinal are separated), which is why in dim lights, it will take several seconds for the eyes to adjust to the dark as opsin and retinal tend to re-associated to form rhodopsin.
This is usually caused by vitamin A deficiency and is characterized by the difficulty to see in dim light.
Night-blindness
This can be a result from night blindness and is defined as the separation of the sensory retina from the pigmented retina. This also affects the periphery of the retina, where the rods are located, therefore affecting vision in low light to a greater extent than vision in bright light.
Retinal Detachment
What is the function of cone photoreceptor cells?
The pigment sin cone cells allow for the perception of colors that is associated with a certain wavelength of light. They are sensitive to blue, red or green. Hence, allowing us to perceive different colors due to the stimulation of these colors (cones)
What are the different interneurons in the sensory retina?
(1) Bipolar cells
(2) Horizontal cells
(3) Ganglion cells
What is the role of bipolar cells?
The bipolar cells synapse with the rods and cone cells.
What is the role of horizontal cells?
Along with the bipolar cells, these modify the output of the rod and cone cells which helps us perceive the borders between objects of contrasting brightness.
What is the role of ganglion cells?
They synapse with bipolar and horizontal cells, and their axons converge at the posterior of the eye to form the optic nerve.
Explain the neuronal pathway of the eyes?
(1) Light is collected in the visual field, which is divided into the temporal and nasal part.
(2) After passing through the lens and the cornea, the light from each half of the visual field projects to the opposite side of the retina to stimulate the photoreceptors.
(3) Action potentials are then conducted along the optic nerve.
(4) The optic nerves then leaves the eye by exiting through the optic foramen to the cranial cavity, wherein two optic nerves connect to each other via the optic chiasm, where the fibers of the optic nerve extend towards the opposite sides of the brain to allow the brain to receive signals.
(5) Axons from the nasal (medial) part of each retina cross through the optic chiasm and project to the opposite side of the brain while the the axons from the lateral part pass through the cranial nerve and project to the same side of the brain.
(6) After that, the ganglionic axons travels through the two optic tracts, which typically terminate in the thalamus.
(7) The neurons from the thalamus form the fibers of the optic radiations that are soon projected through the visual cortex in the occipital lobe of the cerebrum, where vision is perceived.
(The right part of each visual field is projected to the left side of the brain and vice versa)
This is known as the image perceived by the eye or the are wherein light is collected.
Visual Field
This requires both eyes and occurs where the two visual fields overlap. Each eye perceive s a slight different monocular view of the same object, which the brain processes as either three-dimensional or binocular.
Depth perception
This is caused by the misalignment of the two eyes and often results to the weakness of the muscles of the moving eyes. It can also be perceived as a symptom of a neurological problem like brain tumors compressing the nerves of the eye muscles.
Diplopia (binocular diplopia)
This condition refers to nearsightedness or when the image is in front of the retina.
Myopia
This condition pertains to farsightedness of when the image is behind the retina.
Hyperopia
This is the condition wherein the lens become elastic; thus entailing reading or corrective glasses.
Presbyopia
This condition pertains to irregular curvature in the lens or cornea; thus entailing corrective glasses or contacts.
Astigmatism
This condition pertains to the clouding or the opacity of crystalline lens that leads to blurring of vision and eventually loss of sight.
Cataract
What are the three areas of the ear?
(1) External Ear
(2) Middle Ear
(3) Inner Ear
This is the part extending from the outside of the head to the tympanic membrane or also known as the eardrum. This is also involved in conducting sound waves to the inner ear and functions for hearing only.
External Ear
This is an air-filled chamber medial to the tympanic membrane. This is also involved in conducting sound waves to the inner ear and functions for hearing only.
Middle Ear
This is the set of fluid-filled chambers medial to the ear. And is in charge of ear functions in both hearing and balance. This also consists of interconnecting tunnels and channels within the temporal bone.
Inner Ear
This is the fleshy part of the external ear on the outside of the head. This collects sound waves and travels them into the external auditory canal down to the tympanic membrane.
Auricle
This is known as the passageway that leads to the eardrum, where the auricle opens into.
External Auditory Canal
This is the skin that lines the auditory canal.
Ceruminous glands
This is produced by the Ceruminous glands and is defined as a modified sebum called “earwax,” which helps prevent foreign objects from reaching the delicate tympanic membrane
Cerumen
This is a thin membrane that separates the external ear from the middle ear. It consists of a thin layer of connective tissue wiched between two epithelial layers. The soundwaves reaching this causes it to vibrate.
Tympanic membrane
What are the two covered openings of the middle ear that connects it with the inner ear.
(1) Oval window - separates the middle ear and the inner ear
(2) Round window
What are the three auditory ossicles comprising the middle ear?
(1) Malleus or the hammer
(2) Incus or the anvil
(3) Stapes or the stirrup
These form a flexible, bony bridge that transmits vibrations from the tympanic membrane to the oval window.
auditory ossicles
This is the bone attached to the medial surface of the tympanic membrane
Malleus or the hammer
This connects the malleus and the stapes.
Incus or the anvil
This is seated in the oval window, surrounded by a flexible ligament.
Stapes or the stirrup
What happens when the vibrations are transferred from the malleus to the stapes?
The force of the vibrations are amplified about 20-fold because the area of the tympanic membrane is about 20 times that of the oval window. However two small muscles in the middle ear (attached to the malleus and stapes) help dampen vibrations caused by loud noises to protect the ear.
What are the two unblocked openings into the middle ear?
(1) One that opens into the mastoid air cells in the mastoid process (temporal bone)
(2) Auditory tube or eustachian tube
This opens into the pharynx and enables air pressure to be equalized between the outside air and the middle air cavity.
Auditory tube or eustachian tube
What happens when there is unequal pressure between the middle ear and the outside environment or when a person changes altitude?
(1) Distorts the tympanic membranes
(2) Dampen vibrations or make hearing difficulty
(3) Ear pain
can be solved by opening the auditory tube to allow air to enter and exit the middle ear (yawning, swallowing, etc.)
These are interconnecting tunnels and channels within the temporal bone found in the inner ear. This outer surface of this is the periosteum, which lines its inner surface.
Bony Labyrinth
These are smaller set of membranous tunnels and chambers found in the Bony Labyrinth
Membranous Labyrinth
This is the clear fluid that fills the Membranous Labyrinth
Endolymph
This is the fluid in the space between the membranous and bony labyrinth.
Perilymph
The bony labyrinth can be divided into three subsections or regions namely:
(1) Cochlea
(2) Semicircular canals
(3) Vestibule
This is shaped like a snail shell and contains a bony core shaped like screw. This where hearing takes place and it divided three channels
Cochlea
The threads of this screw in the cochlea are called ____________.
Spiral Lamina
What are three channels of the cochlea?
(1) Scala vestibuli
(2) Scala tympani
(3) Cochlear Duct
This extends from the oval window to the apex of cochlea. It is also a channel in perilymph-filled spaces between the walls of the bony membranous labyrinths.
Scala vestibuli (stairway)
This extends in parallel with the Scala vestibuli (stairway) from the apex back to the round window. It is also a channel in perilymph-filled spaces between the walls of the bony membranous labyrinths.
Scala tympani
The wall of the membranous labyrinth that lines the scala vestibuli is called the ________________.
vestibular membrane
The wall of the membranous labyrinth that lines the scala tympani is called the ________________.
basilar membrane
This is formed by the space between the vestibular membrane and the basilar membrane and is filled with endolymph.
Cochlear duct
This is a specialized structure Cochlear duct that contains hair cells.
Spiral organ or organ of Corti
These are specialized sensory cells that contain hair-like microvilli.
Hair cells
These are the hair-like microvilli in hair cells that are stiffened by actin filaments and are embedded on the tectorial.
Stereocilia
This is the acellular gelatinous shelf where the hair tips are embedded. This is also attached to the spiral lamina.
tectorial membrane
This is where the cell bodies of hair cells associated with axon terminals of sensory neurons lie.
Cochlear ganglion or spiral ganglion.
The axons join to form this and joins with the vestibular nerve to become a vestibulocochlear nerve (VIII), which carries action potentials to the brain.
Cochlear nerve
This is formed when the cochlear nerve joins with the vestibular nerve. This carries action potentials to the brain.
vestibulocochlear nerve (VIII),
The process of hearing involves two major steps:
(1) conduction of sound waves (outer, middle, inner ears)
(2) stimulation of hearing receptors (inner ear)
How is the process of hearing?
(1) Vibration create soundwaves. Sound waves strike the tympanic membrane, which causes it to vibrate
(2) The movement of the tympanic membrane causes vibration of the three ossicles of the middle ear (malleus, incus, stapes). These causes them to form a body bridge to conduct and amplify the vibration from the tympanic nerve to the oval window.
(3) Vibration of the base of the stapes (oval window) produces soundwaves in the perilymph of the cochlea.
(a) The two scalae can be thought of as continuous, U-shaped tube, with the oval window at the at one end of the scala vestibuli and the round window at the other end of the scala tympani.
(b) Due to the vibration of the stapes, the perilymph moves through the scala vestibuli to the scala tympani, pushing against the membrane covering of the round window.
(4) The flexibility of the membrane allows the perilymph to move.
(5) The waves produced in the perilymph passing through the vestibular membrane causes vibration of the endolymph, which ends up causing the displacement of the basilar membrane.
(6) When the basilar membrane is displaced, the hair cells moves with the membrane. The microvilli of the hair cells remain embedded and does not move due to their rigid shelf.
(7) However, one end of the microvilli moves with the air cells while the other remains embedded in the the tectorial membrane, causing it to bend,
(8) the bending stimulates hair cells thus inducing action potentials in the cochlear nerve.
(note the vibrations of the perilymph continue through the scala tympani toward round window until they are dampen)
This is a result of vibration and is often referred to as sound waves. These are often characterized for their pitch and volume.
Sound or sound waves
This is the frequency or wavelength of the sound.
Pitch
This is related to the amplitude of the sound wave.
Frequency
How is the structure of the basilar membrane?
The width and the structure basilar membrane is narrower and denser near the oval window and is less dense near the top of the cochlea.
What happens when the sound is of higher pitch and has a shorter wavelength
They can cause maximum distortion nearer the oval window
What happens when the sound is of low pitch and has a longer wavelength
They can cause maximum distortion nearer the apex of the cochlea
What happens to hair cells when the sound perceive is louder and have higher wave amplitudes?
The basilar membrane is more distorted intensely thus causing the hair cells to be stimulated more often, hence generating more action potentials along the auditory pathway.
What are the two forms of hearing impairment?
(1) Conduction deafness
(2) Sensorineural hearing loss
This hearing impairment results from mechanical deficiencies such as the destruction of the ligament that holds the malleus and incus together.
Conduction deafness
This hearing impairment is caused by deficiencies in the spiral organ or nerves, such as loud sounds that can damage the delicate microvilli of the hair cells, leading to the destruction of the spiral organ.
Sensorineural hearing loss
This nerve is in charge of transmitting the senses of hearing and balance. It also functions as two separate nerves carrying information from two separate but closely related structures.
Tibulocochlear nerve (VIII)
This is the portion of the vestibulocochlear nerve that is involved in balance.
Vestibular nerve
Describe the neuronal pathway of hearing,
(1) The cochlear nerve sends axons to the cochlear nucleus in the brainstem.
(2) Neuron in the cochlear nucleus project to other areas of the brainstem and to the inferior colliculus in the midbrain. Neurons from the inferior colliculus also project to the superior colliculus, where reflexes that turn the head and eyes in response to loud sounds are initiated.
(3) From the inferior colliculus, fibers project to the thalamus
(4) Neurons of the thalamus project to the auditory cortex in the temporal lobe of each cerebral hemisphere
This component of equilibrium associated with the vestibule and is involved in evaluating the position of the read relative to gravity.
Static equilibrium
This component of equilibrium associated with the semicircular canals and is involved in evaluating the changes in direction and rate of head movements.
Dynamic equilibrium
This is located in the inner ear and can be divided into two chambers namely: the utricle and saccule.
Vestibule
These are specialized patches of epithelium that surrounds the endolymph . This is also like a spiral organ that contains hair cells.
Maculae
The tips of the microvilli of the maculae are embedded in a gelatinous mass known as the “__________________”
Otolithic membrane
These comprises the otolithic membrane and are particles composed of protein and calcium carbonate.
Otoliths
How are action potentials of equilibrium conveyed from the microvilli ?
(1) the weighted gelatinous mass moves in response to gravity, bending the hair cell microvilli and initiating action potentials in the associated neurons.
(2) The action potentials from these neurons are carried by axons of the vestibular portion by the vestibulocochlear nerve (VIII) to the brain
(3) The brain interprets the change in position of the head
This is involved in dynamic equilibrium and are placed at nearly sight angles to one another, enabling a person to detect movement in essentially any direction
semicircular canals
This is formed by expanding the base of each semicircular canal
ampulla
In each ampulla, the epithelium is specialized to form a “___________.” This also consists of a ridge of epithelium with a curved gelatinous mass known as the cupula.
crista ampullaris
This is known as the ridge of epithelium with a curved gelatinous mass known as the cupula in the crista ampullaris. It also functions as a float that is displaced by the endolymph movement with the semicircular canals.
Cupula
What happens when the cupula moves?
(1) If the head moves in opposite directions, the endolymph tends to remain stationary while the cupula moves with the head. (It displaces the cupula to the direction opposite of the movement of the head)
(2) As the motion continues, fluid catches up. So when the motion stops, the fluid continues to move, displacing the cupula in the same direction of the movement
(3) This movement causes hair cell microvilli to bend and initiates depolarization of hair cells.
(4) Depolarization initiates action potentials in the vestibular nerves to join the cochlear nerves and form vestibulocochlear nerves.
This condition pertains to the continuous stimulation of the semicircular canals due to the rocking motion. This is characterized by nausea and weakness. There is confliction in the interpretation of the brain from the sensory input coming from the semicircular canals, eyes, and proprioreceptors.
Motion Sickness
Explain the neuronal pathway for balance
(1) Axons forming the vestibular portion of the vestibulocochlear nerve project to the vestibular nucleus in the brainstem
(2) The axons then run from the nucleus to different areas of the CNS, such as the cerebellum or the cerebral cortex
This is a complex sensation involving sensory input to the vestibular nucleus not only from the inner ear but also from the limbs and the visual tests as well
Balance
This is a form of motion sickness that is caused by the conflicting information reach the brain from different sources. In this, it reacts with a feeling of vertigo (feeling of spinning) and nausea
Sea sickness
