Anatomy test 5

superior rectus

1 of 6 extrinsic eye muscles Insertion: Superior surface of the eyeball. Action: Moves the eye so the cornea is directed upwards (elevation) and medially (adduction). (looking up to the left) Innervation: oculomotor nerve (III).

Inferior oblique

1 of 6 extrinsic eye muscles. Insertion: inferior surface of the eyeball. Action: depresses the posterior aspect of the eye, elevating the cornea (looking up right). Innervation: oculomotor nerve (III).

lateral rectus

1 of 6 extrinsic eye muscles. Insertion: lateral surface of the eyeball. Action: moves the eye so cornea is directed laterally (abduction). (looking right middle). Innervation: abducens nerve (VI)

Medial rectus

1 of 6 extrinsic eye muscles. Insertion: medial surface of the eyeball. Action: Moves the eye so that the cornea is directed medially (adduction). (looking left middle). Innervation: oculomotor nerve (III)

Superior oblique

1 of 6 extrinsic eye muscles. Insertion: posterosuperior surface of the eyeball. Uses the trochlear as a pulley. Action: depresses the posterior aspect of the eye, depressing the cornea. (looking down right.) Innervation: trochlear nerve (IV).

inferior rectus

1 of 6 extrinsic eye muscles. insertion: inferior surface of the eyeball. Action: moves the eye so cornea is directed downwards (depression). (looking down left). Innervation: oculomotor nerve (III)

Pigmentated epithelium

10th layer of retina. The outermost layer of the retina that sits next to the choroid of the eye. It comprises a single layer of pigmented epithelial cells.

Retina (visual pathway)

1st step in VP Transduction of light waves into electrical signals occurs in the ganglion cells of this. The nerve impulse is then passed along the axons of the ganglions towards the optic nerve.

Optic nerve (visual pathway)

2nd step in VP Is formed by the convergence of the axons of the ganglions from the retina, which meet at the optic nerve head. This nerve then passes out thru the orbit and into the cranial cavity to reach the optic chiasma.

olfactory tract

3rd in olfactory pathway Comprises axons from olfactory bulbs that travel to the temporal lobe, hypothalamus, and limbic system, which control autonomic reflexes (vomiting, salivating, ect.). Fibers also travel to the thalamus, where theyre relayed to the cerebral cortex. Here, signals are integrated w/ those from the senses of taste and sight to give us an overall conscious perception of smell.

ganglion cell layer

3rd innermost layer of retina. Consists of millions of ganglion cells located b/w the inner limiting membrane and the inner synaptic layer.

Optic chiasma (visual pathway)

3rd step in VP This is a flat body of nerve fibers formed by the crossing over of the optic nerves. Inside this, fibers from the medial half of each retina cross over fibers from the lateral half of each retina, to cont. in the contralateral optic tract.

limbic system

3rd step in gustatory pathway. Impulses that come here from the gustatory nucleus help us to appreciate what were tasting. When taste messages arrive here, we experience pleasant or aversive feelings towards certain foods, b/c this part of the brain is assoc. w/ emotion and memory.

hypothalamus

3rd step in gustatory pathway. This is a series of nuclei located anteriorly in the diencephalon, inferior to the thalamus, and in the lateral wall of the 3rd ventricle. It has roles in mood, memory, and emotion. Involved in determining whether or not we experience aversive or pleasant feelings towards specific foods.

Optic tracts (Visual pathway)

4th step in VP These are continuations of the optic chiasma that pass towards the brainstem. Theres 2 optic tracts, each of which curves around the cerebral peduncles to enter the lateral geniculate nucleus of the thalamus.

Lateral geniculate nucleus (visual pathway)

5th step of VP This is one of 6 groups of nuclei present in the thalamus. It receives visual info from the optic tract and relays this info to the primary visual area in the occipital lobe of the brain.

Optic radiations (visual pathway)

6th step of VP These are projections of nerve fibers in the cerebral cortex of the brain that connect the lateral geniculate nucleus w/ the primary visual cortex in the occipital lobe. Other fibers project to other areas of the brain that are concerned w/ diff. aspects of vision, the secondary or visual assoc. area.

Conjunctiva

A thin, transparent film that covers the inside of the eyelids and is reflected onto the surface of the visible part of the sclera (doesnt cover the cornea). It secretes oils and mucus that help to lube the surface of eye and keep it clean.

Hyperopia

AKA: far-sightedness A refractive abnormality of the eye caused by either a thinner than norm lens or when the eyeball is shorter than usual. Both result in the image converging behind the retina.

Myopia

AKA: near-sightedness A refractive abnormality of the eye caused either by a thicker than norm lens or when the eyeball is longer than usual. Both result in the image converging in front of the retina.

glutamate

An inhibitory neurotransmitter which hyperpolarizes the bipolar cells and prevents them from sending signals to the ganglion cells.

Eyebrows

Believed to direct perspiration and rays of sun away from eyes.

Primary visual cortex

Final step of VP The specialized area of the brain responsible for interpreting incoming visual info form the eyes. Is located at the most posterior point of the occipital lobe of the brain. Due to the crossing over of nerves w/in the brain, info from the right eye is sent to the left side of the brain and vice versa. This receives and processes visual signals from lateral geniculate nucleus of the thalamus.

Synaptic ending

Forms the proximal end of the cone cell. Its a complex pedicle containing many neurotransmitter vesicles, and its synapses w/ bipolar cells.

Synaptic ending

Forms the proximal end of the rod cell. Its a bulb-like terminal, which contains many neurotransmitter vesicles. It synapses w/ bipolar cells.

Photopigments

Found in rods and cones Are proteins composed of two parts: opsin and retinal. Respond to light in a cyclical fashion.

Optic chiasma

Here, half of the visual info crosses to the opp. side: fibers from the medial side of the retina enter the opp. optic tract whereas those from the lateral side of the retina remain uncrossed, traveling in the same side optic tract.

Cis-retinal

In darkness, retinal (the light-absorbing part) has a bend shape, called this ..., which fits tightly into the opsin part. When it absorbs light, it straightens out to a shape called trans-retinal. This cis-to-trans conversion is called isomerization.

Horizontal cells

In the 5th layer of retina. Laterally extending cells that synapse w/ photoreceptors. They act as inhibitory interneurons.

4th step of visual processing

Inflow of Na ions partially depolarizes the photoreceptor, triggering a continual release of Glutamate. This hyperpolarizes the bipolar cells and prevents them from sending signals to the ganglion cells. When light strikes the retina it activates enzymes that break down cGMP, creating a decreased inflow of Na ions and a hyperpolarization that decreases glutamate release.

tunics

Layers of the eyeball. 3 layers: fibrous, vascular, and neural.

emmetropic

Normal eye (as in vision)

refraction of light

Or bending of light rays occurs when traveling light comes into contact w/ a surface of a diff. density to that in which it was previously traveling. When light hits the junction b/w these two mediums, it changes speed, and as a consequence, meets the surface at a diff. angle.

Stalk

Part of a cone cell. Connects the inner segment to the outer segment, and contains a cilium.

Tarsal muscles

Part of eyelids Smooth muscles that assist in widening the palpebral fissure in fight or flight.

Lacrimal punctum

Part of lacrimal apparatus. A tiny hole on each eyelid, where tears begin to collect at the medial commissure.

Lacrimal canal

Part of lacrimal apparatus. Each lacrimal punctum leads to this, which drains the tears into the lacrimal sac.

Lacrimal gland

Part of lacrimal apparatus. Produces tears (contains oil, water, mucin, and antimicrobial proteins), which travel down tiny ducts in the upper eyelid to the surface of the eye: the conjunctiva.

nasolacrimal duct

Part of lacrimal apparatus. This drains into the inferior meatus of the nasal cavity, beneath the cover of the inferior nasal concha.

Stalk

Part of the rod. Connects the inner segment to the outer segment, and contains a cilium.

Photopigments

Photopsin= present in cone cells. Rhodopsin= present in rod cells. These are comprised of 2 parts: retinal and opsin

olfactory transduction

Process which a chem. stimulus (or odorant) is converted into a neural signal that can be interpreted by the brain. Only a few molecules of odor need to be present for response. (means olfication in general is a low threshold) 5 steps in this process.

Lacrimal apparatus

Produces tears which moisten the eye, preventing desiccation (drying) and reducing friction from eyelids. Tears also supply eye with nutrients and act as a bactericide. Includes: lacrimal gland, ducts, canal, sac, and punctum.

Eyelashes

Protect eyes from airborne particles, while the eyelids react to protect eyes from injury

Eyelids

Protect the eyeball anteriorly. Theyre seperated by palpebral fissure and join at the medial and lateral commissures. Theyre thin layrs of skin, surrounding the thin tarsal muscles. The upper lid is elevated by levator palpebrae superioris, which is controlled by CN III. The palpebral margin is closed using orbicularis oculi.

1st part of visual processing

Rods and cones absorb light, which changes the shape of their photopigments. This creates a signal that begins in the bipolar cells and passes thru the ganglion cells, optic nerves, and finally, the brain.

Photoreceptors

Specialized receptor cells of the visual system. They convert an optical image into a neural signal, which the brain interprets. Two types in the eye: rods and cones.

Refraction abnormalities

Such as myopia or hyperopia

Accomodation

The ability of the eye to alter its focusing ability on diff. objects. This is achieved by altering the shape and focal length of the lens.

Convergence

The ability of the eyes to maintain binocular vision and track a common object moving towards the eyes. To do this, both eyes rotate medially to maintain the same focal point on the back of both retinas.

cell body

The central, rounded portion of the cone cell, located b/w the outer and inner fibers. It contains the nucleus

3rd step of visual processing

The isomerization of retinal initiates chem. changes that lead to the generation of a receptor potential. In darkness, Na ions flow into the outer segments of the photoreceptors thru Na channels held open by the ligand cyclic guanosine monophosphate (cGMP).

5th step in visual processing

The light essentially turns off glutamate inhibition, which in turn allows the excitation of the bipolar cells. The bipolar cells then stimulate the ganglion cells to form action potentials that pass thru the optic nerve and on to the brain.

Inner fiber

The thin part of a cone cell that connects the cell body to the synaptic ending.

2nd step of visual processing

The trans-retinal separates from opsin, causing a bleaching of the photopigment. Last, the enzyme retinal isomerase converts the trans-retinal back to cis-retinal, which then binds to opsin and regenerates the photopigment.

Opsins

These are the glycoprotein part of photopigments. They combine w/ the light absorbing part, retinals. The type of ... to which a molecule of retinal is bound determines the wavelength of light that a photopigment can absorb. Rods only ahve one type of ...., whereas cones have 3.

Accessory structures of vision

These function to protect the surface of our eyes. Include: eyebrows, eyelashes, eyelids, conjunctiva, and lacrimal apparatus.

extrinsic eye muscles

These originate from the bony orbit (a tendinous ring that wraps around the optic nerve) and insert into the sclera of the eyeball. 6 of them that move the eyeball in almost any direction.

Retinal

This is the light-absorbing part of photopigments derived from vitamin A and it exists in 2 forms: trans-retinal and Cis-retinal. Cis-retinal is the kinked form it takes when its bound to an opsin, whereas trans-retinal is the straightened form that retinal twists into, which enables it to detach from an opsin.

viewing distant objects

To view this object, the lens becomes less convex (long and thin) as incoming light rays from distant objects are almost parallel and dont require much refraction. Here, the ciliary muscles relax, and the zonular fibers of the suspensory ligaments apply tension to the lens so that it becomes thinner.

Viewing close objects

To view this object, the lens becomes more convex (short and thick) to increase its focusing power. This causes incoming light rays to converge more as they enter the lens. Here, the ciliary muscles contract , releasing the tension on the lens so that it becomes fatter.

visual pathway

When light is absorbed by the photoreceptor cells and a nerve impulse is sent thru the layers of the retina to the optic nerve, info is sent along the visual pathway and takes this route: retina > optic nerve > optic chiasma > Optic tracts > lateral geniculate nucleus > optic radiations > primary visual cortex.

strabismus

aka: cross-eye. If contraction of the extrinsic eye muscles is not co-ordinated, due to paralyzed or bc its failed to develop all its nerve connections. Will affect quality of vision and ability to see in 3D.

lacrimal sac

part of lacrimal apparatus. The upper dilated end of the nasolacrimal duct. Oval in form and about 12-15mm. Its upper end is closed and rounded, and its lower end cont. as the nasolacrimal duct, which lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla.

isomerization

the process when a cis-retinal absorbs light, it straightens out to a shape called trans-retinal.

Nerve fiber layer

1 of 10 layers of retina. 2nd innermost layer. Consists of ganglion cell axons, which leave via the optic disc.

Outer segment

External, cone-shaped section of a cone cell, comprising a series of membrane infoldings, that contain the photopigments. Its much shorter than the inner segment.

olfactory gland

one of several cellular components in epithelium that contributes to the process of odor transduction. AKA Bowman's gland. Short, single-cell lined mucous glands that penetrate the olfactory epithelium. Duct of the gland sits in the connective tissue below the cribiform plate. They produce mucus, that functions to keep the surface of the olfactory epithelium moist, allowing odors to dissolve w/in it.

lingual papillae

specialized areas of taste buds of the tongue. Four types: vallate (circumvallate), foliate, fungiform, and filiform,

Outer synaptic layer

the 6th layer of retina. Consists of synaptic connections b/w photoreceptor, bipolar, horizontal, and amacrine cells.

internal limiting membrane

1 of 10 layers of retina. Innermost layer. Consists of a simple thin basement membrane that tops the nerve fiber layer.

steps of olfactory transduction

1. Odor molecule dissolves in nasal mucus, binds to membrane protein that is coupled w/ G protein. 2. This binding activates enzyme adenylate cyclase and sets into motion a chain of events that produce cyclic adenosine monophosphate (cAMP) 3. This chem. messenger activates membrane's ion channels resulting in an exchange of Na, Ca, and chloride ions, and a depolarizing generator potential. 4. If depolarized to threshold, olfactory receptor sends an action pot. along its axon, passing thru small holes in the ethmoid bone and ending at the olfactory bulb. 5. In bulb neuron, signals are received by the glomeruli and relayed thru the olfactory tract and on to the brain, where the odor is identified.

olfactory bulbs

2nd in olfactory pathway. Paired ... lie either side of the roof of the nasal cavity. They receive olfactory nerve fibers and relay incoming info from many olfactory nerve fibers to the olfactory tracts. They contain glomerulis, b/w olfactory nerves, olfactory bulb neurons, and intermediary cells. Here, axons from olfactory nerves that have a large amount of the same type of receptor converge w/in one glomerulus, so that diff smells activate diff. glomeruli. This helps us to distinguish b/w diff. smells.

gustatory nucleus

2nd step in gustatory pathway. This is a collection of neurons in the medulla oblongata assoc. w/ taste. It receives nerve impulses from IX, X, and VII nerves relaying info from the taste buds. From the ...., axons project to the thalamus, hypothalamus, and limbic system. As info is fed thru the gustatory nucleus, it sends signals to the stomach and mouth to increase saliva, thus preparing the digestive system for food.

Thalamus

3rd step in gustatory pathway. This receives gustatory info from the gustatory nucleus and relays this info to the primary gustatory cortex in the parietal lobe of the brain. It consists of a pair of oval masses of gray matter that lie beneath the cerebrum and form most of the diencephalon (posterior part of the forebrain). Theyre made up of 6 groups of nuclei and form the main relay center for ascending sensory impulses en route the cderebral cortex.

inner synaptic layer

4th layer of retina. Consists of synaptic connections b/w cells in the ganglion cell layer and cells in the bipolar cell layer.

bipolar layer (Syn. inner nuclear layer)

5th layer of retina. Consists of bipolar, amacrine, and horizontal cells located b/w the inner and outer synaptic layers.

external limiting membrane

8th layer of retina. Consists of synapses b/w photoreceptors and the surrounding supporting cells.

Photoreceptor layer

9th layer of retina. Consists of photoreceptor cells (rods and cone cells). Rods and cones are responsible for image formation and "light trapping" power of the retina.

Olfactory epithelium (mucosa)

A strip of mucous membrane located on the roof of the nasal cavity. Contians millions of olfactory receptor cells.

Vascular tunica

AKA The pigmented, .... coat. 2nd coat of eye. Consists of: choroid, ciliary body, and iris.

scleral venous sinus

Aqueous humor drains via this structure. Located at the junction of the cornea and sclera.

neural structures of the eye

Are the Retina and Optic nerve. They process light signals and relay them to the brain.

Primary gustatory cortex

Final step in gustatory pathway. Located on the inferior part of the post-central gyrus of the parietal lobe. Receives and process gustatory signals from the taste buds of the tongue and enables us to become conscious of taste.

primary olfactory cortex

Final step in olfactory pathway. Lies on the medial aspect of the orbital surface of the frontal lobe of the cerebrum. Receives and processes olfactory info directly from the olfactory bulbs.

Limbic system

Final step in olfactory pathway. Term given to part of forebrain responsible for emotion and behavior. Signals sent here and its subsequent interaction w/ higher brain centers enable us to remember smells, as well as bring back memories assoc. w/ the smell.

Hypothalamus

Final step in olfactory pathway. Thru connections to limbic system and brainstem, this regulates emotions, autonomic control, hunger, satiety, immunity, memory input, and anger control. Linked to our ability to remember smells and our emotional response to them.

olfactory nerves

First in olfactory pathway after stimulus. First cranial nerves, formed by axons from olfactory receptor cells. About 15-20 olfactory nerves pass on each side of nasal cavity, from roof of nasal fossa thru the cribriform plate, to reach the inferior surface of the olfactory bulb where they synapse w/ the olfactory bulb neurons. These nerves carry info from the olfactory receptor cells to the olfactory bulb.

Cranial nerves

First step in gustatory pathway. Taste buds in epiglottis and throat are innervated via the vagus nerve (X). Gustatory receptor cells in the vallate and foliate papillae synapse w/ fibers from the glossopharyngeal nerve (IX). Gustatory receptor cells in the fungiform papillae synapse w/ fibers from the chorda tympani branch of the facial nerve (VII).

Olfactory bulbs

Found below the anterior end of the olfactory sulcus, on the orbital surface of the frontal lobe of the brain. They receive 15-20 olfactory nerve fibers that relay info about odors from the olfactory receptor cells, located in the roof of the nasal fossa.

Cone cells

Found in 9th layer of retina. Sensitive to high light levels and provide us w/ color vision. 3 types: blue, green, and red and the combo of signals all 3 types enable us to see diff. colors. Their inputs are perceived in color, as the photopigments they contain absorb diff. wavelengths of light. However, unlike rods, they have fewer connects w/ bipolar cells and as a consequence, the info passed onto ganglion cells is more detailed and results in higher resolution vision.

Rod cells

Found in 9th layer of retina. Sensitive to low light levels and provide us w/ black and white vision. Their inputs are perceived black and white b/c the photopigment they contain, which absorbs a lesser range of light wavelengths. Many .... synapse w/ one bipolar cell and resultant high convergence of info causes indistinct and fuzzy vision.

Pigment epithelial cells

Found in the 10th layer of retina. Cuboidal-shaped, melanin-containing epithelial cells that house the outer segments of the photoreceptor cells. The pigment epithelium breaks down the discarded membranous discs of the outer segments of the photoreceptor cells.

taste buds

Grouped amounts of taste cells on the toungue. oval-shaped, found studded in the epithelial walls of the tongue papillae. About 10000 on the tongue, comprise of 3 types of epithelial cells: basal cells, gustatory receptor cells, and supporting cells.

ganglion cells

In the 3rd layer of retina. Multipolar neuron cells. Their dendrites synapse w/ bipolar, horizontal, and amacrine cells. Also have long axons that form the nerve fiber layer. Theyre the output neurons of the retina as they relay sensory info about visual stimuli to the brain, via the optic nerve.

Amacrine cells

In the 5th layer of retina. Laterally orientated neurons that form synapses w/ bipolar and ganglion cells. They modulate photoreceptor inputs, including color and brightness.

Bipolar cells

In the 5th layer of retina. Radially positioned cells w/ 2 processes that extend from either side of their cell bodies. Their axons synapse w/ a ganglion cell, while their dendrites synapes w/ the photoreceptor cells. .... relay and integrate info from the photoreceptors to the ganglion cells, as well as any inputs from surrounding horizontal and amacrine cells.

Aqueous humor

One of a few structures that allow light thru and be focused on the retina. A clean, watery fluid thats filtered from blood capillaries in the ciliary body and is constantly secreted. Important in maintaining intraocular pressure and drains via scleral venous sinus. Also provides nutrients to the avascular cornea and sclera.

Lens

One of a few structures that allow light thru and be focused on the retina. A transparent, avascular, elliptical structure held behind the aperture of the pupil by the suspensory ligaments of the ciliary body. It refracts light to a focal point on the retina and is able to change shape to accomodate viewing objects at closer and further distances.

Anterior chamber

One of a few structures that allow light thru and be focused on the retina. Located b/w the cornea anteriorly and the iris posteriorly. Filled w/ aqueous humor which allows light to pass thru it.

Posterior chamber

One of a few structures that allow light thru and be focused on the retina. Located b/w the iris anteriorly and the lens, suspensory ligaments, and ciliary body posteriorly. Its filled w/ aqueous humor and allows light to pass thru it.

Mucus

One of several cellular components in epithelium that contributes to the process of odor transduction. A viscous fluid produced by the olfactory glands in the olfactory epithelium. Its secreted onto the free surfacde of the olfactory epithelium, keeping it moist so that odors can dissolve and bind to receptors on the surface of the olfactory receptor cells.

Basal cell

One of several cellular components in epithelium that contributes to the process of odor transduction. Another type of supporting cell in the olfactory epithelium. They sit at the base, sandwiched b/w the olfactory receptor and supporting cells, and dont make contact w/ the free surface. They act as stem cells, constantly replenishing the supply of olfactory receptor cells.

Olfactory supporting cell

One of several cellular components in epithelium which contributes to the process of odor transduction. They're tall, columnar epithelial cells that sit adjacent to olfactory receptor cells. These provide support, nourishment, and insulation to the olfactory receptor cells.

Taste pores

One part that surrounds the epithelial cells, forming taste buds. A small opening in the top in the epithelium of the tongue where microvilli of gustatory receptor cells project from each taste cell.

Basal cells

One type of epithelial cell, part of taste buds. Small, round cells at the base of a taste bud. Act as stem cells and function to constantly replace the supply of the taste buds.

Fibrous tunica

Outer coat of eyeball. Includes the Sclera and cornea

cornea

Part of the fibrous tunica. The anterior, transparent part. Bends the light towards the pupil. The avascular transparent dome over the anterior part of the eye. Function: to refract (bend) light towards the pupil and to limit the amount of light that enters the eye.

Sclera

Part of the fibrous tunica. The white of the eye, and is avascular. Functions: to prevent light from entering the eyeball and to maintain eye shape.

Fovea centralis

Part of the neural tunica. A small area at the center of the macula lutea. Its the area of the retina where vision is most accurate.

Optic disc

Part of the neural tunica. AKA: blind spot Located 3mm medial to the macula lutea. Point from which the ganglion cells from the retina leave the back of the eye to form the optic nerve. Theres no photoreceptor cells on this, therefore, it cannot respond to light, thus creating a blind spot.

Macula lutea

Part of the neural tunica. Consists of a small area of cells on the retina, directly in line w/ the lens. Its the area of the retina that provides the clearest vision and contains only cone photoreceptors.

Retina

Part of the neural tunica. Inner lining of the posterior eye. Consists of 10 layers of neural, epithelial, and supporting cells. Attached to the optic disc at the back and to the ora serrata at the front. Contains the photoreceptors and assoc. neurons and fibers.

Cell body

Part of the olfactory receptor cell where theres a central olfactory receptor cell, containing the cell nucleus

Dendrite

Part of the olfactory receptor cell. Is the inferior process of the olfactory receptor cell that extends down from the olfactory epithelium into the nasal cavity. Terminates in a bulb-like process where 10-20 olfactory cilia project. This is where trapping of odors and sensory transduction occurs: trapped odor in mucus bind to receptors in the membrane.

Axon

Part of the olfactory receptor cell. This extends from the cell body in the opp. direction the dendrite. As it travels upwards, it joins other axons to become an olfactory nerve, which passes to the olfactory bulb

iris

Part of the vascular tunica. A pigmented ring of smooth muscle that forms the aperture known as the pupil. It contains two rings of muscles: the pupillary constrictor muscles and the pupillary dilator muscles. It changes the diameter of the aperture of the pupil.

Ciliary body

Part of the vascular tunica. Anterior, thickened portion of the choroid thats made of smooth muscle. Sits behind the iris and forms a ring around the lens. Together, this and lens divide the anterior cavity into anterior and posterior chambers. Suspensory ligaments project from this and attach it to the lens. .... supports the lens and iris, adjusts curvature of the lens, and secretes aqueous humor into the posterior chamber.

Choroid

Part of the vascular tunica. The dark ,brown layer that contains a rich network of blood vessels and lymphatic vessels to drain excess fluid from the posterior cavity. Arterial supply to the .... is via the ciliary arteries.

olfactory pathway

Production of impulses, stimulate by an odor in the nasal cavity take the following route: impulse => olfactory nerve fibers => olfactory nerve => olfactory bulb => olfactory tract => primary olfactory cortex, limbic system, and hypothalamus.

glomeruli

Sites in the brain's olfactory bulb where signals from the smell receptors converge.

Sensory neurons

Surrounds epithelial cell, forming the taste buds. Each taste bud is innervated by gustatory nerve fibers that are in contact w/ the base of gustatory receptor cells. These weave in and around the cells in the taste bud, innervating each gustatory cell and carrying nerve impulses to the brain. Activation of diff. groups of taste neurons enables the brain to evaluate diff combos of impulses, giving us the ablility to distinguish b/w diff. tastes.

lamina propria

Surrounds epithelial cell, forming the taste buds. The connective tissue deep to the epithelial layer. It attaches to the basement membrane of the epithelium and contains the nerve fibers and blood vessels that supply the tongue.

gustatory transduction

Taste is detected when a tastant dissolved in saliva diffuses thru membranes of the gustatory receptor cells. Each taste has an indiv. method of tranduction, using either direct passage or secondary messengers, but all methods result in depolarization of the gustatory receptor cell and neurotransmitter release.

Outer nuclear layer

The 7th layer of retina. An extension of the photoreceptor layer, containing the cell bodies of the photoreceptor cells.

Cell body

The central, rounded portion of a rod cell, located b/w the outer and inner fibers. It contains the nucleus.

Inner segment

The cylindrical part of a cone cell (much wider than rods). It connects the cell body to the outer segment, via the outer fiber, and consists of 2 parts: Myoid and the ellipsoid. This part of the cone contains the Golgi complex and numerous mitochondria.

Outer segment

The external, cylindrical shaped section of a rod cell. Comprises a series of membrane pleats and stacked discs (about 1000). This part of the rod contains photopigments that transduce light energy into receptor potentials.

Inner fiber

The first, thin part of a rod cell that connects the cell body to the synaptic ending.

Neural tunica

The innermost layer of the eyeball. Consists of: retina, macula lutea, fovea centralis, optic disc, and optic nerve (cranial nerve II).

Inner segment

The internal, cylindrical part of the rod that connects the cell body to the outer segment (via the outer fiber). It consists of two parts: myoid and ellipsoid. This part of the rod contains Golgi complexes and numerous mitochondria.

olfactory receptor cells

The olfactory epithelium contains millions of these. They're replaced every 50 days. Each is a bipolar neuron that transduces chem. odor stimuli into generator potentials. Made of 3 parts: cell body, dendrite, and axon.

outer fiber

The second, pinched section of the cone cell that connects the cell body to the inner segment.

Outer fiber

The second, thin section of a rod cell that connects the cell body to the inner segment.

Olfactory bulb neurons

These are ganglionated neurons that make up the olfactory bulb. They synapse w/ the olfactory nerve fibers in the olfactory bulb as globular tangles of nerve synapses, known as glomeruli.

Olfactory nerves

These ascend to leave the nasal cavity thru small holes in the cribriform plate of the ethmoid bone.

adaptation

This refers to the olfactory epithelium's sensitivity to smells over time. "becoming accustomed" to smell occurs quickly, raising the odor threshold for that smell. Total ... can happen after long exposure to a certain smell.

Olfactory tract

This relays incoming signals from the olfactory bulb to the cerebrum.

gustatory receptor cells

Type of epithelial cell, part of taste buds. Main sensory cells of the taste bud. Due to their exposure theyre replaced every 10 days. They are capable of transduction. Have a large, round nucleus. Their apical surface is covered in numerous microvilli (or gustatory hairs), that serve to increase surface area of the cell thats exposed in the mouth. Basal surfaces of these cells are also in contact w/ the nerve fiber endings of many cranial nerves innervating the tonuge.

G protein coupled receptor

Type of gustatory transduction. Tastants dont enter the cel, but bind to G protein coupled receptors on the surface of membrane. This is assoc. w/ bitter, sweet, and umami. Mechanism: Ions bind to membrane receptors linked to G protein called "gustducin". Upon binding, the G protein seperates and activates enzymes also present on membrane (such as phopholipase-C or adenylate cyclase). These enzymes initiate complex cascades that lead to the release of secondary chem. messengers, provoking depolarization of the cell by either increasing Ca ion inflow or reducing K ion outflow.

Direct passage

Type of gustatory transduction. The passing of ions into the cell thru ion channels in the membrane. This is assoc. w/ salty and sour tastants, which use Na and H ions. Mechanism: Na ions enter the receptor cell thru the Na ion channels in the cell's membrane. Entry of posi charged ions into the membrane causes the inside of the cell to become more posi and this change in membrane potential triggers depolarization of the cell.

fungiform papillae

Type of lingual papillae. Located on the anterior part of the dorsal surface of the tongue. They look like shroom-shaped elevations. They have taste buds present both in their walls and on their apical surfaces. Innervation: facial nerve (VIII)

Filiform papillae

Type of lingual papillae. Located over most of the presulcal, dorsal area of the tongue. Small, conical, cylindrical, projections. Tall and pointed and can be found arranged in diagonal rows extending anterolaterally across the tongue. Their apical ends are often split into many processes. This type has NO TASTE BUDS. Innervation: glossophayngeal (IX) and facial nerves (VII).

gustatory pathway

When tastants bind to and initiate a receptor potential in the gustatory receptor cells, a nerve impulse is sent to one of 3 first order neurons that synapse at the base of taste buds. Impulse sent from gustatory receptor cells > glossopharyngeal nerve (IX), Facial nerve (VII), and Vagus nerve (X) > medulla oblongata: gustatory nucleus > Thalamus, hypothalamus, and limbic system > primary gustatory area

tastants

chemoreceptors on the microvilli that detect molecules of food dissolved in saliva

taste threshold

lowest concentration of a tastant you can detect. bitter have lowest .... (most sensitive to bitter tastes), sour and umami have slightly higher..., and sweet and salty have the highest ....

vitreous body

one of a few structures that allow light thru and be focused on the retina. Consists of transparent jelly that fills the posterior cavity and is formed during the development of the eye. Its not renewed or replaced during life. The fluid is thick, gelatinous mass made of collagen and proteoglycans. Helps maintain the shape of the eyeball.

optic nerve (cranial nerve II)

part of the neural tunica. Passes from the back of the globe and enters the middle cranial fossa of the skull, via the optic canal in the sphenoid bone. This cross in the optic chiasma and pass posteriorly to visual structures in the brain.

Squamous epithelium

surrounds epithelial cell, forming the taste buds. The apical surface of each taste bud is comprised of non-keratinized stratified ...... This epithelium consists of a gradient of flat cells stacked on top of one another

5 basic taste sensations

sweet, salty, sour, bitter, and umami (meaty) Also other tastes like fattiness, metallic, and dryness, but research into them is still ongoing.

supporting cells

type of epithelial cell, part of taste buds. Long, spindle-shaped cells that give support to gustatory and basal cells.

Foliate papillae

type of lingual papillae. Located along the lateral surface of the tongue close to the termination of the terminal sulcus. Similar in structure to fungiform papillae, w/ a diff orientation due to their position on the sides of the tongue. They bear numerous taste buds in their walls and on their apical surfaces. Innervation: glossopharyngeal nerve (IX)

vallate (circumvallate) papillae

type of lingual papillae. Surface of tongue is split into oral and pharyngeal parts by a V-shaped terminal sulcus located near the back of the tongue. The largest of the papillae. Usually 12 found in an inverted V-shape. Each papilla consists of a shroom-like central projection surrounded by a sulcus and mucosal elevation. Taste buds are present in the walls of the papillae and sulcus only. Innervation: glossopharyngeal nerve (IX)

stem cells

unspecialized cells that can develop into specialized cells when under the right conditions