Ninja Nerd - Sense Organ

What are the two types of retinas in the eye?

Nasal hemiretina and temporal hemiretina

How do visual fields relate to brain processing?

Visual fields are processed in the opposite side of the brain; right visual field goes to the left brain and vice versa.

What are ipsilateral fibers?

Ipsilateral fibers are signals from the eye that go straight to the same side of the brain.

What are contralateral fibers?

Contralateral fibers are signals that cross to the opposite side of the brain.

What is the lateral geniculate nucleus?

A nucleus in the thalamus that processes visual signals, consisting of 6 layers.

Which layers of the lateral geniculate nucleus do ipsilateral fibers go to?

Ipsilateral fibers go to layers 2, 3, and 5.

Which layers of the lateral geniculate nucleus do contralateral fibers go to?

Contralateral fibers go to layers 1, 4, and 6.

What are the superior and inferior retinal fibers?

Superior retinal fibers (Bum's loop) go through the parietal lobe, while inferior retinal fibers (Myers' loops) go through the temporal lobe.

What is the role of the superior colliculus?

It detects movement in the midbrain.

What is the function of the Edinger-Westphal nucleus?

It sends signals to the ganglionic cells for pupil constriction.

What happens when light is shined into the eye?

It stimulates ganglion cells, which send action potentials through the optic nerve.

What is the role of the ciliary ganglion?

It is part of the PNS that controls the ciliary muscle and sphincter pupillae for near vision.

What is the fibrous tunic of the eye composed of?

The sclera and cornea.

What is the vascular tunic of the eye made up of?

The choroid, iris, and ciliary body.

What are the layers of the cornea?

Thin epithelial layer, Bowman's membrane, stromal layer, Descemet's layer, and endothelial layer.

What is the function of the iris?

It regulates the size of the pupil and controls the amount of light entering the eye.

What is the anterior segment of the eye?

The space between the cornea and lens, consisting of the anterior and posterior chambers.

What is the function of the ciliary processes?

They secrete aqueous humor using nutrients from blood.

What is the choroid's role in the eye?

It absorbs stray light rays and provides vascular support to the retina.

What is the posterior segment of the eye filled with?

Vitreous humor.

What is the function of the vitreous humor?

It transmits light rays and holds the retina in place.

What cells are found in the neural layer of the retina?

Photoreceptors, bipolar neurons, ganglion cells, amacrine cells, and horizontal cells.

What is the conjunctiva?

A connective tissue covering the inner surface of the eyelids and the bulb of the cornea.

What causes conjunctivitis?

Bacteria interacting with the conjunctiva under the eyelid.

What is the function of the tarsal plate?

It serves as an attachment point for muscles and contains sebaceous glands for lubrication.

What is the pathway of tears from the lacrimal gland?

Tears move medially across the eyeball, enter the lacrimal puncta, go through the lacrimal canaliculi, into the lacrimal sac, and exit via the nasolacrimal duct.

What happens at the optic nerve's exit point from the eye?

The optic nerve pierces through the sclera.

What are the lacrimal canaliculi?

Holes that lead tears to the lacrimal sac before emptying into the nasolacrimal duct.

What is the lamina cribriosa?

The holes where the optic nerve pierces through the sclera.

What are the three cell layers of the retina?

Outer pigmented layer, rods and cones, bipolar cells.

What is the function of the outer pigmented layer of the retina?

To absorb stray light and provide nutrients to retinal cells.

What type of vision do rods provide?

Scotopic vision (dim light, gray-scale).

What is rhodopsin?

A protein in rods made of retinal and opsin that is involved in phototransduction.

What type of vision do cones provide?

Photopic vision (visual acuity and color vision).

What are the three types of photopsin?

Photopsin I, Photopsin II, Photopsin III.

What role do horizontal cells play in the retina?

They modulate photoreceptor behavior and assist in dark/light adaptation using GABA.

What is the role of bipolar cells in the retina?

They connect photoreceptors to ganglion cells.

What is the function of amacrine cells?

To integrate information between bipolar and ganglion cells.

What happens to 11-cis-retinal when light hits it?

It converts to all-trans-retinal, activating a transducin protein.

What is the effect of phosphodiesterase in phototransduction?

It breaks down cGMP, leading to hyperpolarization of the photoreceptor cell.

How does decreased glutamate release from rods affect bipolar cells?

It stimulates bipolar cells by preventing cations from leaving, keeping them positive.

What is PERRLA?

An acronym for pupil equal, round, reactive to light and accommodation.

What happens to light from the left visual field in the left eye?

It hits the nasal hemiretina and crosses over in the optic tract.

Where do the optic tracts meet?

At the lateral geniculate nucleus (LGN) of the thalamus.

How are ipsilateral and contralateral fibers organized in the LGN?

Ipsilateral fibers synapse on sections 2, 3, and 5; contralateral fibers on sections 1, 4, and 6.

What is the function of the superior colliculus?

It is responsible for visual reflexes.

What triggers the pupillary reflex?

Light shining on the retina activates photoreceptors, leading to pupil constriction.

What is the difference between direct and consensual pupil response?

Direct response is pupil constriction in the stimulated eye; consensual response is constriction in the other eye.

What role does the Edinger-Westphal nucleus play in the pupillary reflex?

It sends projections to the ciliary ganglion to control pupil constriction.

What happens to the ciliaris muscle when it contracts?

The zonular fibers loosen, allowing the lens to bulge for near vision.

What is the role of the short ciliary nerve?

It innervates the ciliaris muscle and sphincter pupillae for accommodation and pupil constriction.

What is the parasympathetic response to light?

Pupil constriction due to activation of the sphincter pupillae.

How does light adaptation occur in photoreceptors?

By the conversion of all-trans retinal back to 11-cis retinal, allowing for increased glutamate release.

What is the function of melanopsin in ganglion cells?

It is stimulated by light and triggers potentials sent down both ipsilateral and contralateral fibers.

What nerve communicates with the ciliary muscle and sphincter pupillae?

The long ciliary nerve

What effect does the long ciliary nerve have on the ciliary muscle?

It relaxes the ciliary muscle, flattening the lens for far vision.

What is mydriasis?

Pupil dilation

What is miosis?

Pupil contraction

What condition is characterized by an eyeball that is too long?

Myopia (nearsightedness)

How is myopia treated?

With a concave lens

What condition is characterized by an eyeball that is too short?

Hyperopia (farsightedness)

How is hyperopia treated?

With a convex lens

What happens to light from the left visual field of the left eye at the optic chiasm?

It crosses over to the right side.

What is the role of the lateral geniculate nucleus (LGN) in the visual pathway?

It processes visual information before sending it to the visual cortex.

Where do ipsilateral fibers synapse in the LGN?

On zones 2, 3, and 5.

Where do contralateral fibers synapse in the LGN?

On zones 1, 4, and 6.

What is Baum's Loop?

Pathway of superior retinal fibers through the parietal lobe to the occipital lobe.

What is Meyer's Loop?

Pathway of inferior retinal fibers through the temporal lobe to the occipital lobe.

What visual field loss results from a lesion to the right optic nerve?

Mono-ocular blindness (loss of vision in the right eye).

What is bi-temporal hemianopia?

Loss of vision in the outer visual fields of both eyes due to a lesion at the optic chiasm.

What visual field loss occurs with a lesion of the right optic tract?

Left homonymous hemianopia (loss of left visual field in both eyes).

What is left inferior quadrant hemianopia?

Loss of vision in the left inferior visual fields due to a lesion of Baum's Loop.

What is right superior quadrant hemianopia?

Loss of vision in the right superior visual fields due to a lesion of Meyer's Loop.

What happens to rods during dark to light adaptation?

Rods turn off as rhodopsin is bleached.

What is the function of rhodopsin?

It is a photopigment in rods that responds to light.

What occurs during light to dark adaptation?

Pupils dilate, rhodopsin accumulates, and retinal sensitivity increases.

What is the fovea centralis?

The center point of the macula lutea with the highest concentration of cones.

What is the role of cones in vision?

They are important for visual acuity and color vision.

What is the macula lutea?

The center of the retina responsible for sharp vision.

What is the optic disc?

The blind spot in the retina where there are no photoreceptors.

What happens to the pupils when transitioning from dark to light?

The pupils constrict to focus light on the fovea.

What is the effect of a lesion to the posterior cerebral artery?

It can cause homonymous hemianopia with sparing of the macula.

What is color blindness?

An X-linked recessive disorder where cones lack certain photopsins, most commonly affecting red or green vision.

What causes nyctalopia (night blindness)?

Usually caused by decreased production of vitamin A, which is necessary for the formation of photopigments.

What is retinitis pigmentosa?

A disorder where pigmented epithelial cells cannot renew photoreceptors, leading to rod degeneration and nyctalopia.

What is the function of the auricle/pinna?

To funnel sound waves into the ear.

What are ceruminous glands?

Glands lining the external auditory canal that secrete cerumen (earwax).

What are the two layers of the tympanic membrane?

The pars tensa (dense connective tissue) and the pars flaccida (areolar connective tissue).

What is the role of the tensor tympani muscle?

To dampen sound waves by pulling the malleus and tensing the tympanic membrane.

What are the ossicles?

The malleus, incus, and stapes, which transmit sound vibrations from the tympanic membrane to the oval window.

What is the function of the stapedius muscle?

To dampen sound by preventing excessive vibrations from reaching the oval window.

What is the pharyngotympanic tube (eustachian tube)?

A tube that equalizes pressure between the atmosphere and the middle ear.

What is the cochlea?

A snail-shaped structure in the inner ear that contains three chambers: scala vestibuli, scala media, and scala tympani.

What fluid fills the scala vestibuli and scala tympani?

Perilymph.

What fluid fills the scala media (cochlear duct)?

Endolymph, which is rich in potassium.

What is the helicotrema?

The point in the cochlea where the scala vestibuli and scala tympani meet.

What is the spiral organ of Corti?

A structure in the scala media containing hair cells and a tectorial membrane that detects sound.

What are the utricle and saccule responsible for?

Detecting static equilibrium.

What is the function of the semicircular canals?

To detect dynamic equilibrium.

What is the modulus in relation to the cochlea?

A conical bone around which the cochlea makes about 2.5 rotations.