Ch.15 Flashcards
Olfaction
sense of smell
in response to odors that stimulate sensory receptors in the olfactory region
Where is the olfactory region and what is it lined with?
Olfactory region is located in the extreme superior area of nasal cavity and lined with specialized epithelium called the olfactory epithelium
The olfactory epithelium contains approx ________ olfactory neurons, which are ________ _________ cells
10 million
Olfactory receptor cells
Olfactory vesicles
Bulbous enlargements of dendrites of olfactory neurons that extend into the epithelial surface of the nasal cavity
Olfactory hairs
Cilia on the olfactory vesicles which lie in thin mucous film on epithelial surface
Olfactory neurons are considered what type of receptor?
Chemoreceptor
Odorants
Airborne molecules that enter the nasal cavity and are dissolved into the fluid covering the olfactory epihelium
Bind to odorant receptor molecules
What is the process for a binding of an odorant to activating a olfactory neuron?
- Odorant binds to receptor molecule
- Receptor molecule activates G protien, which activates adenylate cyclase.
- Adenylate cyclase catalyzes the formation of cAMP from ATP
- cAMP in these cells causes Na+ and Ca2+ channels to open
- The influx of ions causes depolarization and an action potential
What are the 7 primary smells?
Camphoraceous (mothballs)
Musky
Floral
Pepperminty
Ethereal (fresh pears)
Pungent
Putird
Can a olfactory receptor react to more than one odorant?
yes
What is the neuronal pathway for olfaction?
Axons from the olfactory neuron which forms olfactory nerve, project through small foramina in the bony cribiform plate to the olfactory bulb where olfactory neurons synapse with 2ndry neurons which relay olfactory info to the brain via olfactory tracts
Olfactory stimuli cause not only perception of odors but also a emotional and autonomic responses. What parts of the brain do the olfactory neurons lead to?
Central olfactory cortex areas in temporal and frontal lobes
Also to the hypothalamus, hippocampus, and structures of limbic system
What are the structures that dectect taste or gustatory stimuli?
Taste buds
Papillae on tounge
bumps on tounge / not taste buds
What are the 4 major types of papille and where are they located?
- *Filiform** - most numerous but no tastebuds/rough surface helping with food
- *Vallae** - Surrounded by a wall/largest and least numerous, V shape separeting anterior and posterior tounge
- *Foliate** - leaf shaped / sides of tounge and most sensative taste buds
- *Fungiform** - mushroom shaped / scattered irregulary
Taste buds are associated with vallate, foliate, and fungiform papillae
What is the life span of a taste cell?
10 days
Each of the 10,000 taste buds found in the oral cavitiy consists of what 3 types of specialized epithelial cells?
Taste cells - sensory
Basal cells - non sensory
Supporting cells - non sensory
Each taste cell has several microvilli, called?
Tastants
Substances dissolved in saliva which enter taste pores and stimulate the taste cells
What are the 5 classes of tastants?
Salt
Sour
Sweet
Bitter
Umami
How does the taste of Salt occur?
When Na+ diffuses through Na+ channels resulting in depolarization of taste cells
How do we taste sweet ?
bind to receptor molecules and cause depolarization through G protien mechanisms
How do we taste Sour ?
Results when H+ of acids cause depolarization 1 of 3 ways
- enter through H+ channels
- Bind to ligand gated K+ channels and block the exit of K+
- open ligand gated channels for other positive ions and allow them to diffuse into the cell
How do we taste Bitter ?
Simular to how we taste sweet, through G protiens
How do we taste Umami ?
results when amino acids bind to receptors and causes depolarization through g protien mechanisms
What other factors can affect the perception of taste?
Texture
hot or cold temp
What are the neuronal pathways for taste?
Facial nerve VII - Chorda tympani transmits taste sensations from anterior 2/3s of tounge, except from vallae papillae
Glossopharyngeal nerve IX - carries taste sensations from posterior 1/3 of tounge, the vallate papillae and superior pharynx
Vagus nerve X - carries fibers from epiglottis
*The fibers then go to Medulla oblongata then decussate then go to thalamus. then go to cerebrum
The visual system includes
Eyes
Accessory structures
Optic nerves, tracts and pathways
What are the accessory structures of the visual system?
Eyebrows
Eyelids
Eyelashes
conjuntiva
Lacrimal apparatus
Extrinsic eye muscles
What is the function of eyebrows?
Prevent perspiration from running down forehead and shade eyes from sunlight
What is the function of the eyelids?
Palpebrae
their eyelashes protect eyes from foriegn objects
What are the 5 layers of tissue that make up eyelids
- thin layer of skin on external surface
- thin layer of aerolar connective tissue
- layer of skeletal muscle containing orbicularis oculi and levator palpebrae superior muscles
- cresent shaped layer of Dense connective tissue which helps maintain shape of eyelid
- Palpebral conjunctiva which lines inner surface of eyelid and anterior surface of eyeball
Ciliary glands
modified sweat glands that open into the follicles of the eyelashes to keep them lubricated
*A sty forms when one of these glands becomes inflamed
Meibomian glands
aka Tarsal glands
are sebaceous glands near inner margins of eyelids, produce sebum which lubricates the lods and restrains tears from flowing over the margins of eyelids
Chalazion - infection or blockage of a meibomian gland
Conjunctiva
thin transparent mucous membrane associated with the eyelids and exposed areas of the eye
Palpebral conjunctiva
- covers inner surface of eyelid
Bulbar conjunctiva
- covers anterior white surface of eye
Conjunctival fornices
- where palpebral and bulbar conjunctiva meet
Conjunctivitis
inflammation of conjunctiva caused by infection or other irritation
Acute contagious conjunctivitis (pink eye) - caused by a bacterium
Lacrimal apparatus
consists of a lacrimal gland situated in the superolateral corner of the orbit and a nasolacrimal duct
Lacrimal gland
innervated by parasympathetic fibers from facial nerve VII
Produces tears which leave the gland through lacrimal ducts
Produces tears at a rate of about 1mL/day
What are the 6 extrinsic muscles attached to the eye?
Superior rectus muscle
Inferior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Clincal test for noraml eye movement is called
H test
*a persons inability to move their eye to one part of the H may indicate dysfunction of a muscle or cranial nerve
They eyeball is a hollow fluid filled sphere. The wall of the eyeball consists of what 3 layers?
Fibrous tunic
Vascular tunic
nervous tunic
Fibrous tunic
Outer layer of eyeball
Consists of sclera and cornea
Vascular tunic
middle layer of eyeball
consists of choroid, ciliary body and iris
Nervous tunic
inner layer of eyeball
consists of retina
Sclera
white outer layer
Firm opaque tissue layer that consists of dense collaganeous connective tissue with elastic fibers
Helps maintain shape of eye, protects internal structures, provides attachement point for muscles
Cornea
avascular, transparent structure that permits light to enter the eye
As light passes through it bends or refracts
*Part of eyes focusing system
*most common eye injury are cuts or tears of cornea
What makes cornea easy to transplant
Easily accessable and easily removed
Avascular
less immunologically active
Vascular tunic
Consists of choroid, ciliary body, iris
Has short ciliary arteries which pierce sclera in the circle around optic nerve,
Contains a large number of melanin containing pigment cells and appears black in color
The smooth muscle of the iris is organized into what 2 groups?
Sphincter pupillae - when contracts pupil decreases
dilator pupillae - when contracts the pupil increases
Nervous tunic
Retina and consists of pigmented layer and inner neural layer
What 2 features can be observed when the retina is examined with an ophhalmoscope?
Macula & optic disc
The interior of the eye is divided into what 3 chambers?
Anterior chamber
Posterior chamber
Vitreous chamber
Refraction
Bending of light
As light rays converge, they reach a point in which they cross called
Focal point
Causing light to converge is called
Focusing
reflection
When a ray of light bounces off a surface that is not transparent
When an object is brought closer than 20 feet to the eye what 3 events bring the image into focus?
Accomodation by the lens -(changing shape of lens)
constriction of the pupil
convergence of the eyes
Near point vision
the point at which blurring occurs when an object is too close to see
Presbyopia
increase in near point of vision that develops with age
Depth of focus
the greatest distance through which an object can be moved and still remain in focus on the retina
Main factor affecting depth of focus is pupil size
Convergence
medial rotation of the eyes
Myopia
nearsightedness
Can see close objects clearly and far objects are blurry
Focal point is too near the lens and the image is focused in front of the retina
Corrected by concave lens aka minus lens
radial keratotomy and LASIK
Radial keratotomy
a series of 4-8 radiaing cuts are made in cornea, so it becomes flattened and eliminates myopia
Hyperopia
farsightedness
can see distant objects clearly but close objects are blurry
Cornea or lens system is too weak or eyeball too short
Image is focused behind the retina
can be correct by convex lenses (plus lenses)
Presbyopia
normal unavoidable degeneration of accommodation power of eye associated with aging
*Lens becomes less flexible
When near point of vision increases beyond 9 inches
Avg age is mid 40’s
Astigmatism
type of refractive error that affects quality of focus
Can be corrected with glasses if normal astigmatism
The retina consists of a neural layer and a pigmented layer. The neural layer has what 3 sublayers?
Photoreceptor cells
bipolar cells
and ganglionic cells
and 2 plexiform layers where neurons of adjacent layer synapse with eachother
Pigmented layer
consists of a single layer of cells filled with melanin
Rods
bipolar photoreceptor cells involved in non-color vision, responsible for vision under conditions of reduced light
Rhodopsin
purple pigment that consists of the protien opsin
Cone
color vision; visual activity
Cones
bipolar phooreceptor cells
color vision and visual acuity are the functions of cone cells
Cones require relatively bright light to function
Contain visual pigment, iodopsin (red,blue,green)
Where is color interpreted?
In the visual cortex of occipital lobe
What does colorblindness result from?
dysfunction of 1 or more of the 3 photo pigments (red, blue,green)
What are the organs of hearing and balance?
External ear
Middle ear
Inner ear
*The external ear and middle ear are involved in hearing only, while the inner ear functions both in hearing and balance
What are the 3 layers of the tympanic membrane?
- simple cubodial epithelium
- middle layer of connective tissue
- thin stratified squamous epithelium
The semicircular canals do what?
involved in balance
Cochela does what?
involved in hearing
What are the 2 major features of sound?
Volumne and pitch
Volume is a function of sound wave amplitude or height measured in decibels
Pitch is the sound wave frequency measured in hertz
