Special senses (WEEK 5)

Palpebral fissure

The space between the eyelids that allows for the passage of light into the eye. It plays a crucial role in eye protection and blinking.

Lateral commisure

The outer corner of the eyelids where they meet, contributing to the shape and function of the palpebral fissure.

medial commisure

The inner corner of the eyelids where they meet, playing a role in the overall shape and function of the palpebral fissure.

sclera

The white outer layer of the eyeball, providing structure and protection. It is continuous with the cornea at the front of the eye.

conjunctiva

A thin, transparent membrane that covers the inner surface of the eyelids and the white part of the eyeball, providing lubrication and protection.

lacrimal caruncle

A small, pinkish gland located at the medial commisure of the eye, responsible for producing secretions that help lubricate the eye.

pupil

The opening in the center of the iris that regulates the amount of light entering the eye.

Lacrimal Apparatus Pathway

Stimulation from eyelashes→Lacrimal gland secretes→Secretions travel from gland to the Lacrimal punctum→Punctum to Canaliculi→Canaliculi to the Lacrimal Sac Structure→ Secretions enter nose through Nasolacrimal duct

Lacrimal Secretions

Mucus, Antibodies, Saline, Lysozyme

Extrinsic eye muscles

Superior, Lateral, Inferior, Medial rectus muscle, Common tendonous ring, Superior, inferior oblique muscle

Eyeball layers

The eyeball consists of three layers: the outer fibrous layer (sclera and cornea), the middle vascular layer (choroid, ciliary body, and iris), and the inner neural layer (retina). These layers work together to protect the eye and facilitate vision.

Anterior pole, Posterior pole

the two ends of the eyeball, with the anterior pole being the front surface and the posterior pole being the back surface where the optic nerve exits.

cornea

The transparent front layer of the eye that covers the iris, pupil, and anterior chamber. It refracts light and provides most of the eye's optical power.

ciliary body

A structure in the eye that connects the iris to the choroid, responsible for controlling the shape of the lens and producing aqueous humor.

ciliary zonule

A series of fibers that connect the ciliary body to the lens, helping to hold the lens in place and allowing for changes in its shape during accommodation.

macula lutea

A small, yellowish spot on the retina that contains a high concentration of cones, responsible for sharp central vision.

vitreous humor

The clear gel-like substance that fills the space between the lens and the retina in the eye, helping to maintain its shape and providing support to the retina. It also helps transmit light to the retina.

Rods vs. Cones

Rods are photoreceptor cells in the retina that are sensitive to low light levels, responsible for night vision, while cones are photoreceptor cells that function in bright light and are responsible for color vision and detail.

Bipolar cell vs. Ganglion cell

Bipolar cells are neurons in the retina that transmit signals from photoreceptors to ganglion cells, which then relay visual information to the brain. This pathway is essential for processing visual signals.

Events of Phototransduction

-Photon stimulates rhoclops

-Rhoclops con.change, release Transducin

-Transducin binds to Phosphodiesterase

-cGMP reduces, cGMP cation gated channel closes.

-Photoreceptor inhibited

Rods vs. Cones

Rods are very sensitive, only contain the black and white pigment, and hundreds can feed into one ganglion cell

Cones are less sensitive and contain 1 of 3 pigments for color vision (red, green, and blue), and require its unique ganglion and bipolar cells.

Emmetropic

-No refractive error

-All light focuses onto one point (Macula)

-Focal point is on retina

Myopic

-Focal Point is in front of retina

-All light focuses to a point before reaching the retina, causing distant objects to appear blurry.

-Only some light hits macula

Hyperopic

-Focal point is behind retina.

-The point where light focuses is beyond the retina.

-Only some light hits macula.

Olfactory epithelium

Mucus→Olfactory Cilia→Olfactory Receptor Cell (Supporting cell for structure)

Olfactory Transuction

Odorant binds to Receptor→ Conf.change G-protein→G-protein binds to Adenylate cyclase→Adenylate cyclate converts ATP to cAMP→cAMP binds to cAMP gated cation channel and lets ions in→ depolarization

Taste bud comp. tongue

(Front-back) Fungiform papillae, Circumvallate papillae, Foliate papillae (side)

Tasting

Tasting pore→ Gustatory hair→ Gustatory cell→ Taste fibers →Basal cells →Cranial nerves

Salty & Sour Taste Transduction

-Na or H enter their appropriate TRP.

-Stimulus causes Ca to enterthe cell, leading to depolarization and neurotransmitter release.

Bitter, Sweet, umami

Taste stimuli→Taste receptor→ Conf.change G-protein → Bind to Phospholipase C →IP3 released→ IP3 binds to IP3 gated channel on Intracellular calcium stores→ Ca enters cell, causing depolarization and neurotransmitter release.

Organ of Corti

The sensory organ located in the cochlea of the inner ear, responsible for converting sound vibrations into neural signals.

Semicircular canals vs Otolith organs

The structures in the inner ear that help maintain balance. Semicircular canals detect rotational movements, while otolith organs sense linear acceleration and gravity.

Auditory neuron connection

Vesibular cochlea→ Inferior pons→Decussation→ Superior pons → Inferior canaliculi → Medial geniculate Thalamus → Primary auditary area cerebral cortex

Taste Neuron Connection

Gustatory pathway→ Gustatory nucleus in Medulla Oblongata→Decussation→ Primary gustatory area in cerebral cortex

Olfaction

Olfactory bulb→ Olfactory tract → Primary olfactory area in the cerebral cortex