Unit 5: Lecture 6 (Finish Taste, Sight, Equilibrium, & Hearing)

True

(T/F) Olfaction is one of the few sensory systems that bypasses the thalamus in direct route to the cortex.

Pseudostratified, non-motile (immotile), ciliated columnar epithelium

What type of epithelium is olfactory epithelium?

Olfactory (Bowman) glands

What glands secrete serous fluid that dissolves airborne odorants, enabling interaction with olfactory receptors?

True

(T/F) Each olfactory receptor neuron expresses only one type of receptor, and depending on which combinations are activated, the brain interprets this as a specific smell.

True

What unmyelinated axons penetrate the cribriform plate of the ethmoid bone, entering the anterior cranial fossa to synapse in the olfactory bulb, located superior to the cribriform plate?

Posteriorly

From the olfactory bulb, the signal is relayed ______ via the olfactory tract.

Temporal lobes

Where is the primary olfactory cortex located?

True

(T/F) Because the olfactory pathway bypasses the thalamus and projects to limbic structures, it has a strong link to emotional memory.

Lingual papillae

Gustation, or the sense of taste, is mediated by taste receptor cells located primarily within specialized epithelial structures known as _____ _____.

Vallate (circumvallate) papillae

What are the largest and least numerous papillae, numbering 8 to 12? They are arranged in a V-shaped row just anterior to the terminal sulcus of the tongue. Each is surrounded by a deep trench and houses numerous taste buds on the lateral walls.

Glossopharyngeal (CN IX)

Vallate (circumvallate) papillae are innervated primarily by the ________ nerve (CN ____), which provides sensory input from the posterior one-third of the tongue.

Fungiform papillae

What are the mushroom-shaped papillae that are scattered among the filiform papillae, primarily on the apex and lateral margins of the anterior two-thirds of the tongue? They are visible to the naked eye and contain a modest number of taste buds.

Facial nerve (CN VII)

What are fungiform papillae innervated by?

Foliate papillae

What are the papillae located on the posterolateral margins of the tongue, which appear as parallel folds or ridges? In humans, these structures contain taste buds primarily in early childhood, with a decrease in number and function with age. They are more prominent and functional in other mammals

They receive sensory innervation primarily from the glossopharyngeal nerve (CN IX), though some anterior fibers may receive input from the facial nerve (CN VII).

What nerves innervate the foliate papillae?

Fillform papillae

What are the most numerous type of papillae on the tongue and are conical or thread-like in shape? They are keratinized and serve a mechanical function rather than a gustatory one.

True

(T/F) Filiform papillae do not contain taste buds. Their primary function is to aid in manipulating food and providing texture to the tongue surface.

Vallate, fungiform, and foliate papillae

What types of papillae contain taste buds?

True

(T/F) Taste perception is deeply integrated with olfactory input, as smell contributes significantly to flavor identification and complexity.

First-order neurons

What order neurons in the taste chain are described:

Gustatory receptor cells synapse with sensory fibers of cranial nerves. For the anterior two-thirds of the tongue, signals are transmitted via the chorda tympani branch of the facial nerve (CN VII). For the posterior one-third, signals travel via the glossopharyngeal nerve (CN IX). The vagus nerve (CN X) also contributes taste fibers from the epiglottis and pharynx.

Second-order neurons

What order neurons in the taste chain are described:

Located in the solitary nucleus of the medulla oblongata. Axons ascend in the central tegmental tract to the thalamus.

Third-order neurons

What order neurons in the taste chain are described:

Project from the thalamus to the primary gustatory cortex, which is primarily located in the insular cortex.

Sweet, staly, sour, bitter, and umami

What are the 5 primary taste modalities recognized by the gustatory system?

Sweet

What taste sensation is elicited by sugars and certain alcohols found in fruits?

Salty

What taste sensation results from the presence of metal ions such as sodium and potassium?

Sour

What taste sensation is primarily due to hydrogen ions from acidic substances?

What taste sensation is often associated with alkaloids and can act as a protective mechanism against the ingestion of potentially toxic substances?

What taste sensation refers to the savory taste of amino acids, especially glutamate? It is commonly experienced in protein-rich foods.

Hypoglossal (CN XII) and Vagus (CN X)

What two nerves provide motor control to the tongue?

Palatoglossus muscle

What is the only tongue muscle that is innervated by the vagus nerve (CN X) rather than the hypoglossal nerve (CN XII)?

Lingual nerve (from CN V3), facial nerve (CN VII), glossopharyngeal nerve (CN IX), and vagus nerve (CN X)

What four sensory nerves innervate the tongue?

Lingual nerve (from CN V3)

What nerve provides general sensation to the anterior two-

thirds of the tongue and does not transmit taste?

Facial nerve (CN VII)

What nerve via the chorda tympani branch, provides taste sensation to the anterior two-thirds of the tongue?

Glossopharyngeal nerve (CN IX)

What nerve provides both general and taste sensation to the posterior one-third of the tongue?

Vagus nerve (CN X)

What nerve provides taste sensation to the root of the tongue and the epiglottis?

Intrinsic tongue muscles (Superior longitudinal, inferior longitudinal, transverse, and vertical muscles)is the anatomical transition zone between the transparent cornea and the opaque

sclera of the eye.is the anatomical transition zone between the transparent cornea and the opaque

sclera of the eye.

What muscles change the shape of the tongue?

Corneal margin

What is the anatomical transition zone between the transparent cornea and the opaque sclera of the eye?

Conjunctiva

What is the transparent mucous membrane that lines the inner surface of the eyelids (palpebral conjunctiva) and reflects onto the anterior surface of the sclera (bulbar conjunctiva), forming a conjunctival sac? It terminates at the corneal margin.

Stratified columnar epithelium containing goblet cells

What type of epithelium makes up the conjunctiva?

Lacrimal gland → Eye surface → Lacrimal puncta → Lacrimal canaliculi → Lacrimal sac → Nasolacrimal duct → Inferior nasal meatusWhat

What is the flow of tears?

Water, electrolytes, and lysozyme for antibacterial defense.

What does lacrimal fluid (tears) contain?

Superior rectus

What muscle elevates, adducts, and medially rotates the eyeball?

Inferior rectus

What muscle depresses, adducts, and laterally rotates the eyeball?

Medial rectus

What muscle adducts the eyeball?

Lateral rectus

What muscle abducts the eye?

Inferior oblique

What muscle abducts, elevates, and laterally rotates eyeball (allows you to look up and out when the eye is adducted)?

Superior oblique

What muscle Abducts, depresses, and medially rotates eyeball (depresses the adducted eye - allows you to look down and out) (Medial rotation = Intorsion)?

Levator palpebrae superioris

What muscle elevates the upper eyelid?

Ophthalmic artery

What is the first intracranial branch of the internal carotid artery? It enters the orbit through the optic canal alongside the optic nerve (CN II) and gives rise to several critical

branches supplying the eye, orbit, face, and nasal cavity. These branches are essential for the vascular support of extraocular muscles, orbital contents, and cutaneous structures of the forehead and scalp.

Supratrochlear, supraorbital, anterior and posterior ethmoidal, and central retinal arteries

What are the four key branches of the ophthalmic artery?

False

(T/F) Papillae and taste buds are the same thing.

Supratrochlear artery

What artery is the terminal branch of the ophthalmic artery that ascends to the forehead medial to the supraorbital artery? It supplies the skin and muscles of the medial forehead and scalp.

Supraorbital artery

What artery travels through the supraorbital foramen with the supraorbital nerve? It supplies the upper eyelid, forehead, and anterior scalp.

Anterior and posterior ethmoidal arteries

What arteries arise from the ophthalmic artery as it courses medially in the orbit? These arteries enter the anterior and posterior ethmoidal foramina. Part of Kiesselbach's triangle, but the posterior ethmoidal artery is less consistently involved.

Central retinal artery

What artery is one of the most critical branches of the internal carotid, as this artery pierces the optic nerve sheath and enters the retina at the optic disc to supply the inner retina? It is an end artery without significant collateral circulation.

Central retinal artery

Occlusion of what artery results in sudden, painless monocular blindness? This is an ophthalmic emergency requiring immediate intervention.

Anterior, posterior, and vitreous chambers

What are the three distinct fluid-filled chambers within the eyeball that contribute to intraocular pressure, optical function, and structural integrity?

Anterior chamber

What chamber lies between the cornea and the iris/pupil?

Aqueous humor

What fills the anterior chamber of the eye?

Posterior chamber

What chamber is the narrow space between the posterior surface of the iris and the anterior surface of the lens?

Aqueous humor

What fills the posterior chamber?

Ciliary processes

Where is aqueous humor produced?

Vitreous chamber

What chamber is located posterior to the lens and helps maintain the shape of the eyeball, holds the retina in place against the choroid, and supports the lens posteriorly?

Vitreous humor

What fills the vitreous chamber?

Fibrous (outer), vascular (middle), and inner retinal layers

What are the three concentric layers of the eyeball?

Fibrous (outer) layer

What layer of the eye includes the sclera (protection and structure) and the cornea (refracting light)?

Vascular (Middle) layer

What layer of the eyeball includes the choroid (nourishes the outer retina), ciliary body (contains ciliary muscle which alters lens shape, and ciliary process which secretes aqueous humor), and the iris (regulates pupil diameter)?

Inner (retinal) layer

What layer of the eyeball contains the retina?

Neural and outer pigmented layer

What are the two layers of the retina?

Neural layer

What layer of the retina contains photoreceptors (rods and cones)?

Outer pigmented layer

What layer of the retinal reduces light scatter and supports the photoreceptors metabolically?

Neural retina

Retinal detachment involves separation of the ____ ____ from the underlying pigmented epithelium, which can lead to permanent vision loss if not promptly treated.

Sclera

What is the opaque, fibrous, white portion of the eye, covering approximately 85% of the eyeball's surface? It is continuous anteriorly with the cornea and posteriorly with the optic nerve sheath.

Maintains the shape of the globe and provides an anchor point for the six extraocular muscles.

What does the sclera do?

Cornea

What is the transparent, avascular anterior portion of the fibrous tunic? It plays a key role in refraction of light, contributing to nearly two-thirds of the eye's total refractive power.

It plays a key role in refraction of light, contributing to nearly two-thirds of the eye's total refractive power.

What does the cornea do?

Cornea

Oxygen and nutrients are supplied to the _____ through diffusion from the tear film (externally) and the aqueous humor (internally).

Choroid

What lies between the sclera and retina and is composed of a dense capillary bed and pigmented cells that minimize light scatter? It is the primary vascular supply to the outer retina and ends anteriorly at the ciliary body.

Ophthalmic

Choroid receives blood primarily from branches of the _____ artery.

Ciliary body

What is the ring of tissue that connects the choroid to the iris?

Ciliary muscle and ciliary process

What is the ciliary body composed of?

Ciliary process

What secretes aqueous humor into the posterior chamber, which nourishes the avascular cornea and lens?

Ciliary muscle

What is the smooth muscle that controls lens accommodation for near and far vision by altering the tension on the suspensory ligaments (zonular fibers) attached to the lens?

Oculomotor nerve (CN III)

What nerve provides parasympathetic innervation to the ciliary muscle, which facilitates contraction, which rounds the lens for near focus and relaxation flattens the lens for distant vision?

True

(T/F) With aging (presbyopia), the lens loses its elasticity and the ciliary muscle's ability to induce accommodation is reduced, leading to difficulty focusing on close objects.

Iris

What is the most anterior part of the uvea and contains two smooth muscles: the sphincter pupillae and dilator pupillae?

Sphincter pupillae

What part of the iris receives parasympathetic innervation via CN III and constricts the pupil?

Dilator pupillae

What part of the iris is under sympathetic control and dilates the pupil. These opposing actions regulate the amount of light entering the eye?

Serous exocrine gland

What type of gland are the lacrimal glands?

Inner neural and outer pigmented layers

What are the two layers of the retina?

Parasympathetic innervation via facial nerve (CN VII) and sensory innervation from lacrimal nerve via trigeminal nerve (CN V)

What innervates the lacrimal gland?

Inner neural layer

What layer of the retina is light-receptive and houses the photoreceptor cells (rods and cones)?

Outer pigmented layer

What layer of the retina absorbs scattered light and helps maintain the integrity of the photoreceptors?

Ora serrata

The retina terminates anteriorly at the ___ _____, a serrated junction between the retina and the ciliary body.

Rods

What type of photoreceptor is more numerous and are essential for night (scotopic) vision and function well in low light but do not provide color information?

Cones

What type of photoreceptors are less numerous, concentrated in the macula lutea, especially the fovea centralis, and are responsible for color vision and visual acuity in bright (photopic) conditions?

Macula lutea

What is the central region of the retina rich in cones and adapted for detailed central vision?

Fovea centralis

What is the small depression in the macula, contains only cones and represents the point of highest visual acuity?

Optic disc

What is the site where the optic nerve (cranial nerve II) exits the eyeball? This region lacks photoreceptors and is thus insensitive to light, forming the physiological blind spot.

True

(T/F) Light entering the eye is refracted by the cornea and lens, and focused on the retina, particularly the fovea centralis, where photoreceptors convert it into electrochemical signals that are transmitted to the brain.