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Chapter 15
Special Senses
163
Anatomy
Undergraduate 2
02/07/2012

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Term
Eyeball size
Definition
Approx 1 inch in diameter
Term
How many sensory receptors are in the eye?
Definition
70% of all sensory receptors
Term
Eye protection
Definition
A cushion of fat and the bony orbit
Term
Orbicualris oculi
Definition
Close the eyelid
Term
Levator palebrae superioris
Definition
gives the upper eyelid mobility
Term
Orbicularis muscle
Definition
depresses the eyebrows
Term
Corrugator muscles
Definition
move the eyebrows downward and medially; wrinkles forehead
Term
Extrinsic Eye Muscles: Purpose
Definition
Enable the eye to follow moving objects. Maintains the shape of the eyeball
Term
Extrinsic Eye Muscles: Origin
Definition
Four rectus muscles originate from the annular ring. Superior oblique originates from the annular ring
Term
Names of the 4 rectus eye muscles
Definition
Lateral, Medial, Superior, Inferior
Term
Name of the two oblique eye muscles
Definition
Inferior, Superior
Term
Action of the Lateral rectus
Definition
Moves eye laterally
Term
Action of the medial rectus
Definition
Moves eye medially
Term
Action of the superior rectus
Definition
Elevates eye and turns it medially
Term
Action of the Inferior rectus
Definition
Depresses eye and turns it medially
Term
Action of the inferior oblique
Definition
Elevates eye and turns it laterally
Term
Action of the superior oblique
Definition
Depresses eye and turns it laterally
Term
Controlling cranial nerve of the Lateral Rectus
Definition
VI, abducens
Term
Controlling cranial nerve of the Medial rectus
Definition
Oculomotor, III
Term
Controlling cranial nerve of the Superior rectus
Definition
Oculomotor, III
Term
Controlling cranial nerve of the Inferior rectus
Definition
Oculomotor, III
Term
Controlling cranial nerve of the Inferior Oblique
Definition
Oculomotor, III
Term
Controlling cranial nerve of the Superior Oblique
Definition
Trochlear, IV
Term
Palpebrae
Definition
Eyelids
Term
Palpebrae(Eyelids) Function
Definition
Protect the eye anteriorly. Act as windshield wipers
Term
Palpebral fissure
Definition
separates eyelids
Term
How are the eyelids supported internally?
Definition
By tarsal plates of connective tissue
Term
Eyelashes: Purpose
Definition
Project from the free margin of each eyelid. Initiate reflex blinking
Term
Lubricating glands associated with the eyelids
Definition
Ciliary glands, Gland of Zeis, Meibomian or Tarsal glands, Lacrimal caruncle
Term
Ciliary glands
Definition
Lie between hair folliciles, protective film keeps tears from overflowing
Term
Gland of Zeis
Definition
lubricate the eyelashes
Term
Meibomian or Tarsal glands
Definition
secrete an oily substance that lubricates eyelids preventing the lids from sticking together
Term
Lacrimal caruncle
Definition
contains glands that secrete a whitish, oily secretion, (Sandman's eye sand)
Term
Conjuctiva: What is it?
Definition
Transparent membrane that lines the eylids as the palpebral conjuctiva. Lubricates and protects the eye immunologically
Term
Conjuctiva: What does it cover?
Definition
the whites of the eyes as the bulbar or ocular conjuctiva
Term
Lacrimal apparatus: What does it consist of?
Definition
the lacrimal gland and associated ducts
Term
What do the lacrimal glands secrete?
Definition
Tears
Term
What do Tears contain?
Definition
mucus, antibodies, and lysozyme
Term
How do tears enter the eye?
Definition
Via superolateral excretory ducts
Term
How do tears exit the eye
Definition
Medially via the lacrimal punctum
Term
Where do the tears drain into?
Definition
The nasolacrimal duct - collected in the nasal cavity
Term
What is the structure of the eyeball?
Definition
A slightly irregular hollow sphere with anterior and posterior poles
Term
What is the wall of the eye composed of?
Definition
Three tunics
Term
What are the three tunics of the eye?
Definition
Fibrous, vascular, and sensory
Term
The internal cavity of the eye is filled with what?
Definition
Fluids called humors
Term
How is the internal cavity separated?
Definition
By the lens into anterior and posterior segments
Term
Where is the fibrous tunic located?
Definition
The outermost coat of the eye
Term
What is the fibrous tunic composed of?
Definition
Opaque sclera, Clear Cornea
Term
Is the opaque sclera posterior or anterior?
Definition
Posterior
Term
Is the clear cornea anterior or posterior?
Definition
Anterior
Term
What is the function of the sclera?
Definition
Protects the eye and anchors extrinsic muscles
Term
What is the function of the cornea?
Definition
Lets light enter the eye
Term
Vascular tunic: Other name
Definition
Uvea
Term
Regions of the Vascular Tunic
Definition
Choroid, Ciliary body, Iris
Term
Choroid region: Anatomy
Definition
A dark brown membrane that forms the posterior portion of the uvea
Term
Choroid Region: Purpose
Definition
supplies blood to all eye tunics
Term
Ciliary body: Anatomy
Definition
Thickened ring of tissue surrounding the lens
Term
Ora serrata
Definition
non-neuronal area of the retina
Term
Ciliary body: composition
Definition
Smooth muscle bundles (ciliary muscles)
Term
Ciliary body: Function
Definition
anchors the suspensory ligament that holds the lens in place
Term
Iris: anatomy
Definition
colored part of the eye
Term
Pupil - anatomy
Definition
central opening of the iris
Term
Pupil - function
Definition
regulates the amount of light entering the eye
Term
When do pupils constrict?
Definition
Close vision and bright light
Term
When do pupils dilate?
Definition
Distant vision and dim light. Changes in emotional state. When subject matter is appealing or requires problem-solving skills
Term
How is the Parasympathetic system related to the pupil?
Definition
Constricts the pupil via the sphincter pupillae muscle
Term
How is the sympathetic system involved with the pupil?
Definition
Dilates the pupil via the dilator pupillae muscle
Term
Sensory Tunic: Retina - how many layers?
Definition
Two-layered membrane
Term
Retina - pigmented layer
Definition
the outer layer that absorbs light and prevents its scattering
Term
Neural layer contains what?
Definition
Photoreceptors that transduce light energy. Bipolar cells and ganglion cells. Amacrine and horizontal cells.
Term
What are the two layers of the Retina?
Definition
Pigmented and neural layer
Term
What are the two layers of the Retina?
Definition
Pigmented and neural layer
Term
What are the two types of photoreceptors?
Definition
Rods and cones
Term
Rods - function
Definition
Respond to dim light. Used for peripheral vision
Term
Cones - Function
Definition
Respond to bright light, have high-acuity color vision, found in the macula lutea, concentrated in the fovea centralis
Term
Retina: Ganglion cells
Definition
Run along the inner surface of the retina. Leave the eye as the optic nerve
Term
Retina: Optic disc
Definition
Where the optic nerve leaves the eye. Lacks photoreceptors (the blind spot)
Term
Blood supply to the retina: Neural retina
Definition
Outer third receives from the choroid. Inner 2/3 served by the central artery and vein
Term
Posterior segment: Filled with what?
Definition
Clear gel called vitreous humor
Term
Role of vitreous humor
Definition
Transmits light, supports the posterior surface of the lens, Holds the neural retina firmly against the pigmented layer, contributes to intraocular pressure
Term
Anterior Segment - What are the two chambers called?
Definition
Anterior and Posterior
Term
How are the two anterior chambers divided?
Definition
Anterior - cornea and iris
Posterior - iris and lens
Term
What is Aqueous humor?
Definition
Plasmalike fluid that fills the anterior segment
Term
How does the Aqueous humor drain?
Definition
Via the canal of Schlemm
Term
What is the role of Aqueous humor?
Definition
Supports, nourishes and removes wastes
Term
Lens - What is it?
Definition
A biconvex, flexible, avascular structure
Term
What does the Lens do?
Definition
Allows precise focusing of light onto the retina
Term
What is the lens composed of?
Definition
Epithelium and lens fibers
Term
What is lens epithelium?
Definition
anterior cells that differentiate into lens fibers
Term
What are lens fibers?
Definition
Cells filled with the transparent protein crystallin
Term
What happens to the lens with age?
Definition
Becomes more compact and dense and loses its elasticity
Term
Photoreception
Definition
process by which the eye detects light energy
Term
What do rods and cones contain?
Definition
Visual pigments (photopigments)
Term
How are the visual pigments arranged?
Definition
In a stack of disklike infoldings of the plasma membrane that change shape as they absorb light
Term
Functional characteristics of Rods
Definition
Sensitive to dim light and best suited for night vision. Absorb all wavelengths of visible light. Perceived input is in gray tones only. Sum of visual input from many rods feeds into a single ganglion cell. Results in fuzzy and indistinct images
Term
Functional characteristics of Cones
Definition
Need bright light for activation (have low sensitivity), have pigments that furnish a vividly colored view, each cone synapses with a single ganglion cell, vision is detailed and has high resolution
Term
Electromagnetic radiation
Definition
all energy waves from short gamma rays to long radio waves
Term
What is retinal?
Definition
A light-absorbing molecule
Term
What do retinal and opsin combine to form?
Definition
Visual pigments
Term
What is retinal synthesized from?
Definition
Vitamin A
Term
What are the two isomers of Retinal?
Definition
11-cis and all trans
Term
What does isomeriziaton of retinal initate?
Definition
Electrical impulses in the optic nerve
Term
What is the visual pigment of rods?
Definition
Rhodopsin (opsin + 11 cis retinal)
Term
Excitation of rods: Light phase
Definition
Rhodopsin breaks down into all trans retinal + opsin (bleaching of the pigment)
Term
Excitation of Rods: Dark phase
Definition
All-trans retinal converts to 11-cis form.
Term
How is rhodopsin regenerated?
Definition
11-cis retinal + opsin
Term
Excitation of cones: Similarities to rods
Definition
Visual pigments are similar (retinal + opsin). Excitation is similar
Term
Three types of cones
Definition
Red, blue, green
Term
How are intermediate colors perceived?
Definition
Activation of more than one type of cone
Term
Signal Transmission: Step 0
Definition
Photoreceptors and bipolar cells only generate graded potentials
Term
Signal Transmission: Step 1
Definition
Light hyperpolarizes photoreceptor cells
Term
Signal Transmission: Step 2
Definition
Hyperpolarization ceases release of inhibitory neurotransmitter glutamate
Term
Signal Transmission: Step 3
Definition
Bipolar cells (no longer inhibited) are then allowed to depolarize and release neurotransmitter onto ganglion cells
Term
Signal Transmission: Step 4
Definition
Ganglion cells generate APs that are transmitted in the optic nerve
Term
Phototransduction: Step 1
Definition
Light energy splits rhodopsin into all-trans retinal, releasing activated opsin.
Term
Phototransduction: Step 2
Definition
Freed opsin activates the G protein transducin
Term
Phototransduction: Step 3
Definition
Transducin catalyzes activation of phophodiesterase (PDE)
Term
Phototransduction: Step 4
Definition
PDE hydrolyzes cGMP to GMP and releases it from sodium channels
Term
Phototransduction: Step 5
Definition
Without bound CGMP, sodium channels close, the membrane hyperpolarizes, and neurotransmitter cannot be released.
Term
Visual Pathways: What do the axons of retinal ganglion cells form?
Definition
Optic nerve
Term
Where do the medial fibers of the optic nerve decussat?
Definition
At the optic chiasm
Term
Where do most fibers of the optic tracts continue to?
Definition
The lateral geniculate body of the thalamus
Term
Where do Opticr adiations travel from?
Definition
The thalamus to the visual cortex
Term
Cortical Processing: Primary visual cortex
Definition
Basic dark/bright and contrast information
Term
Cortical processing: Prestriate cortices (visual associations areas)
Definition
Form, color, and movement
Term
What are the two streams the visual information proceeds to anteriorly?
Definition
Ventral and Dorsal stream
Term
Ventral Stream
Definition
Temporal lobe - processes identification of objects
Term
Dorsal stream
Definition
Parietal cortex and post central gyrus - processes spatial location
Term
Chemical senses
Definition
gustation (taste) and olfaction (smell)
Term
What are chemoreceptors?
Definition
Proteins found on the outside of cells that bind to chemical or other proteins
Term
What happens during binding with chemoreceptors?
Definition
Sets off a chain of intracellular events that result in signal being sent to the brain
Term
How do chemoreceptors respond to chemicals in regards to taste?
Definition
Via substances dissolved in saliva
Term
How do chemoreceptors responds to chemicals in regards to smell?
Definition
Substances dissolved in fluids of the nasal membranes
Term
What is the organ of smell?
Definition
The olfactory epithelium
Term
What does the olfactory epithelium cover?
Definition
The superior nasal concha
Term
What are olfactory receptor cells?
Definition
Bipolar neurons with radiating olfactory cilia
Term
What are olfactory receptors surrounded and cushioned by?
Definition
Supporting cells
Term
Where do basal cells lie?
Definition
At the base of the epithelium
Term
What do olfactory cells synapse with?
Definition
Mitral cells
Term
What processes odor signals?
Definition
Glomerular mitral cells
Term
What do mitral cells send impulses to?
Definition
The olfactory cortex, the hypothalamus, amygdala, and limbic system
Term
Physiology of smell: Step 1
Definition
Odorant bind to its receptor
Term
Physiology of smell: Step 2
Definition
Receptor activates Gprotein
Term
Physiology of smell: Step 3
Definition
G protein activates adenylate cyclase
Term
Physiology of smell: Step 4
Definition
Adenylate cyclase converts ATP to cAMP
Term
Physiology of smell: Step 5
Definition
cAMP opens a cation channel allowing Na+ and Ca+ influx and causing depolarization which triggers an AP
Term
Where are many of the taste buds found?
Definition
Of the 10,000 most are found on the tongue
Term
Where are taste buds found?
Definition
In papillae of the tongue mucosa
Term
What are the three types of papillae?
Definition
Filiform, fungiform, and circumvallate
Term
Which papillae contain taste buds?
Definition
Fungiform and circumvallate
Term
Structure of a taste bud: What three major cell types make up a taste bud?
Definition
Supporting cells, Basal cells, Gustatory cells
Term
Supporting cells
Definition
insulate the receptor
Term
Basal cells
Definition
dynamic stem cells
Term
gustatory cells
Definition
taste cells
Term
What must occur for a chemical to be tasted?
Definition
Must be dissolved in saliva, must contact gustatory hairs
Term
What occurs with the binding of the food chemical?
Definition
Depolarizes the taste cell membrane, releasing neurotransmitter which initiates a generator potential that elicits an action potential
Term
Which nerves carry impulses from the taste buds to the solitary nucleus of the medulla?
Definition
Cranial Nerves VII (facial) and IX (glossopharygneal)
Term
Where do the impulses travel after reaching the solitary nucleus of the medulla?
Definition
Branch to the gustatory cortex, hypothalamus and limbic system
Term
Gustatory cortex
Definition
taste
Term
Hypothalamus and limbic system
Definition
appreciation of taste
Term
How much does smell influence taste?
Definition
80% of taste is smell
Term
Which receptors influence taste?
Definition
Heat (thermo-), touch (mechano-), and pain (noci-)
Term
What other variables affect taste?
Definition
Temperature and texture
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