Cranial Nerves, Sensory Organs, Eye and Vision, and Ear, Hearing, and Equilibrium

Flashcards on Cranial Nerves, Sensory Organs, Eye and Vision, and Ear, Hearing, and Equilibrium

Cranial Nerves

Nerves that exit the brainstem; different parts of the brainstem are associated with different cranial nerves.

General Senses (Somesthetic)

Sense touch, pressure, stretch, heat, cold, pain, blood pressure, and blood composition. Distributed throughout the body in the skin, muscles, tendons, joint capsules, and viscera.

Special Senses

Sense taste, smell, vision, hearing, and equilibrium. Distribution is limited to the head and they are innervated by the cranial nerves.

Exteroceptors

Respond to stimuli outside the body and are found near or at the body’s surface (eyes, taste, pain, temperature, touch, pressure).

Interoceptors

Respond to stimuli inside the body and are found in the viscera and blood vessels. These produce feelings of visceral pain, nausea, and stretching (chemoreceptors in blood vessels).

Proprioceptors

Sense position or movement of the body and its parts. They are only found in skeletal muscles, joints, tendons, and ligaments (Golgi tendon organs and muscle spindles).

Nociceptors

Pain receptors that respond to chemicals, stretching, and trauma and are found virtually anywhere in the body that pain can occur (tissues, mucosa, muscles, joints, gut).

Temperature Receptors

Respond to either cold or hot stimuli. Unencapsulated, free nerve endings, distributed throughout the body.

Mechanoreceptors

Stimulated by stretch (muscle spindles and Golgi tendon organs) in muscles and tendons. Pressoreceptors (baroreceptors) can be found in blood vessels and lungs (sense/monitor blood pressure changes or extension of lungs).

Chemoreceptors

Detect chemicals for smell, taste, and blood composition; general and special sense.

Photoreceptors

Visual receptors located in the eye (cones and rods); special sense.

Taste Buds

Located on the tongue (mostly), mucosa of cheeks, pharynx, and epiglottis of larynx and consist of 50-100 epithelial cells: gustatory (taste) cells, supporting cells and basal cells

Gustatory Cells

Taste cells that have apical microvilli (gustatory hairs) that are located in the taste pores and a sensory fiber connection at the base of the cell.

Olfactory Receptors

Found in pseudostratified epithelium on the roof of the nasal cavity called olfactory epithelium.

Olfactory Cells

Bipolar neurons with 20 nonmotile cilia called olfactory hairs; only neurons that are replaced (about every 60 days); closest neurons to the surface of the body and exposed to the external environment.

Lacrimal Apparatus

Contains the lacrimal gland which produces lacrimal fluid (mucus, antibodies, lysozyme) to help cleanse, moisten, and protect the eye surface.

Fibrous (External) Tunic

Outer layer of the eye composed of the sclera and cornea.

Sclera

Dense connective tissue for protection; Also called the white of the eye; the posterior part.

Cornea

The most anterior part of the fibrous tunic, transparent region; allows the light to enter the eye.

Vascular (Middle) Tunic

Uvea; composed of the choroid, ciliary body, and the pigmented iris.

Choroid

Provides blood supply (oxygen and nutrients) to retina; a collection of blood vessels between the retina and sclera.

Ciliary Body

Has the muscle to act on the lens and produces aqueous humor that nourishes the lens and cornea.

Iris

Controls the amount of light that reaches the retina by adjusting the size of pupil (with help of smooth muscle in the iris) and provides color to the eye.

Sensory (Internal) Tunic

Composed of the retina and optic nerve.

Retina

Has the photoreceptors (cones and rods) and is attached at the optic disk (aka blind spot=has no photoreceptors), where the optic nerve begins, and at the ora serrata (its anterior margin).

Rods

Photoreceptors for night (scotopic) vision, concentrated on the periphery of the retina.

Cones

Photoreceptors for day (photopic) and color vision, concentrated in the fovea centralis of the macula lutea.

Aqueous humor

Clear fluid produced by the ciliary body. It fills the area between the lens and cornea (anterior segment) and supplies them with O2 and nutrients.

Lens

The biconvex, flexible structure held in place by suspensory ligaments (hold the lens in place as they attach the lens to the ciliary muscles) and their tightness can change the shape of lens (thicker or thinner) to help focus light rays on the retina.

Vitreous Body

The jelly filling in the space between the lens and retina (posterior segment of the eye). It binds to water and lasts a lifetime; give the eye its shape and volume.

Optic Nerve

Cranial nerve II, formed of axons of ganglion cells in the retina. Purely sensory. Starts at the optic disc=a region without photoreceptors.

Hyperopia

The eyeball is too short, light focuses after it reaches the retina; Cannot see objects up close (farsightedness).

Myopia

The eyeball is too long, light focuses before the retina; Cannot see objects far away; Nearsightedness.

Ceruminous glands

Exocrine glands located in external ear canal; Produce cerumen (ear wax) to prevent foreign particles from entering the auditory canal and protects from water. It also coats the tympanic membrane.

Auditory Tube

Connects the middle ear (normally filled with air) with the pharynx (throat); Allows air to enter or leave the middle ear cavity and equalize pressure on both sides of the tympanic membrane.

Cochlea

Converts sound pressure impulses into electrical impulses that will travel through the (vestibule) cochlear nerve to the brain; Houses the organ of hearing called organ of Corti.

Organ of Corti

The organ of hearing in the cochlea; possesses hair cells responsible for hearing

Scala Vestibuli

Superior duct of the cochlea; attached to oval window; filled with perilymph and functions to transmit pressure.

Scala Tympani

Inferior duct of cochlea; attached to round window; filled with perilymph and functions to transmit pressure.

Cochlear Duct

Middle duct of the cochlea; filled with endolymph and has sensory function as it houses the organ of Corti (detects pressure impulses).

Basilar Membrane

Separates the cochlear duct from tympanic canal; the membrane where the organ Corti attaches and it plays a critical role in hearing.

Tectorial Membrane

Anchored and does not move and sits atop the hair cells; component of the organ of Corti.

Static Equilibrium

Interprets the position of the head permitting the CNS to maintain stability and posture when the head and body are not moving

Dynamic Equilibrium

Interprets balance when one is moving, or at least the head is moving.

Macula

Patch of hair cells in the utricle and saccule topped by a membrane (otolithic membrane) that has small, calcium carbonate crystals called otoliths; receptors for static equilibrium.

Crista Ampullaris

Complex mechanoreceptor within the semicircular canals containing the mechanoreceptors (hair cells) for dynamic equilibrium.