Anatomy and Physiology: Special Senses

Flashcards covering Special Senses: Anatomy, Physiology of Taste, Smell, Vision, Sound Perception, Equilibrium, and Orientation.

Objectives of Special Senses

Sense organ anatomy, physiology of taste and smell, physiology of vision, mechanism of sound perception, mechanisms of equilibrium and orientation.

Chemesthesis

The sensation of chemicals by means of nonchemoreceptors, such as sensing changes in pain, temperature, and touch, usually in reference to harmful chemicals.

Fungiform papillae

Mushroom shaped papillae located at tip and edges of tongue

Foliate papillae

Located back and side of the tongue and are sensitive papillae

Filiform papillae

Most abundant and give tongue rough texture but do not taste

Circumvallate papillae

Largest at the base of the tongue and play a role in gag reflex.

Sweet flavor

Sugars, saccharin, alcohol

Salt flavor

Metal ions

Sour flavor

Hydrogen ions

Bitter flavor

Quinine and nicotine

Umami flavor

Elicited by amino acid glutamate

Olfactory bulb

Connects with olfactory nerve and collects stimuli from olfactory receptor cells.

Mitral Cell

Neurons that process olfactory information.

Glomerulus

Synaptic site of mitral cells and olfactory receptor neurons.

Olfactory Transduction Steps

Odorant binds to receptor, receptor activates G protein, G protein activate adenylate cyclase, Adenylate cyclase converts ATP to cAMP, cAMP opens a cation channel allowing Na+ and Ca2+ to influx and cause depolarization.

Iris

The colored part of the eye that controls the size of the pupil and regulates the amount of light entering.

Ciliary Body

A structure behind the iris that produces aqueous humor and helps change the shape of the lens.

Aqueous Humor

The fluid in the anterior segment that provides nutrients and maintains pressure.

Vitreous Humor

The gel-like substance in the posterior segment that helps maintain the eye’s shape.

Macula

A specialized area of the retina responsible for sharp, central vision.

Fovea

The small pit in the macula with the highest concentration of cones, providing the sharpest vision.

Lacrimal Gland

Produces tears to lubricate and protect the eye.

Lacrimal Puncta

Tiny openings near the inner corners of the eyelids that drain excess tears into the tear ducts.

Tear Ducts (Nasolacrimal Duct)

Channels that carry tears from the eye surface to the nasal cavity.

Conjunctiva

A thin, transparent membrane covering the sclera and inner eyelids, helping to keep the eye moist and protected.

Caruncle

A small, fleshy bump in the inner corner of the eye that contains glands producing tears and mucus.

Rods

Can perceive light intensity and distinguish light from dark. They see grey tones and absorb all wavelengths of light. These feed into a single ganglion resulting in fuzzy images

Cones

Can perceive color and have three types: Red, blue, Green which can only absorb wavelengths of their respective colors. Each cone synapse with their own ganglion giving clear vision.

Amacrine cells

Interneurons

Horizontal cells

Summate inputs

Rods

visual pigments include rhodopsin (retinal, opsin)

Phototransduction steps

Light activates visual pigment, visual pigment activates transducin (g protein), transducing activates phosphodiesterase (PDE), PDE converts cGMP to GMP causing cGMP levels to fall, as cGMP levels fall, cGMP gated ion channels close resulting in hyperpolarization, no neurotransmitter is released from rod, lack of IPSP in bipolar cell causes depolarization, bipolar cell sends EPSP in ganglion which activates action potential.

Adaptation to bright light

Dramatic decreases in retinal sensitivity where rod function is lost and switching from the rod to cone system where visual acuity is gained.

Adaptation to dark

Cone stop functioning in low light and Rhodopsin accumulates in dark and retinal sensitivity is restored.

Parasympathetic nervous system

Causes pupils to contract

Sympathetic nervous system

Causes pupils to dilate

Close vision

Lens bulges and ciliary muscles contract

Far vision

Muscles relax and lens flattens

Myopia

Focal point infront of retina causes near sightedness

Hyperopia

Focal point behind retina causes far sightedness

Astigmatism

Lens fragments light and causes multiple focal points

Presbyopia

Gradual inability to focus on objects causing farsightedness with age.

Monochromacy

Total color blindness

Protanopia

Red blind

Deuteranopia

Green blind

Tritanopia

Blue blind

Ipsilateral fiber

Uncrossed

Contralateral fibers

Crossed

Stapes

Stirrup. Associated with the stapedius muscle which dampens loud noises

Incus

Anvil

Malleus

Hammer. Associated with the tensor tympani muscle. Helps dampen noise from chewing.

Cochlea

converts sound vibrations into neural signals through specialized hair cells.

Vestibule

helps detect changes in head position and contributes to balance.

Semicircular Canals

sense rotational movements of the head and aid in balance.

Basilar Membrane

vibrates in response to sound and helps differentiate pitches.

Organ of Corti

The primary hearing organ within the cochlea, housing hair cells that detect sound waves.

Hair Cells

Sensory cells in the cochlea and vestibular system that convert mechanical stimuli into nerve signals.

Vestibular Nerve

Transmits balance-related information from the semicircular canals and vestibule to the brain.

Cochlear Nerve

Carries auditory signals from the cochlea to the brain for sound perception.

Oval Window

A membrane-covered opening that receives vibrations from the stapes, transmitting sound into the cochlea.

Round Window

helps release pressure changes within the cochlea.

Modiolus

Central axis of cochlea made of spongy bone. Houses spiral ganglion.

Osseous Spiral Lamina

Bony shelf from modiolus which divides cochlea into scala vestibuli and scala tympani

Vestibular membrane

Thin membrane outside of the cochlea that helps transmit vibrations and allow nutrients to pass.

Scala media (cochlear duct)

Houses organ of corti

Helicotrema

Small opening where scalas meet. Plays role in low frequency hearing.

Frequency

Number of waves that pass a point in time. Measured by Hertz (20-20k human hearing)

Loudness

Measure by decibles (0-120bd human hearing)

Pathway of Sound

Sound waves vibrate the tympanic membrane, auditory ossicles vibrate and pressure is amplified, pressure waves created by the stapes pushing on the oval window move through fluid in the scala vestibuli, Sounds with frequencies below hearing travel through the helicotrema and do not excite hair cells, sounds within hearing range go through the cochlear duct, vibrating basilar membrane and deflecting hairs on inner hair cells

Sound Transduction

Stereocilia open and close mechanically gated ion channels in hair cells, When the basilar membrane is at rest the cell is slightly depolarized with only a few gated ion channels open, when the hairs bend towards the tallest cilia, the tip links tighten and open the channels allowing depolarization and release of neurotransmitters to stimulate cochlear nerve, When hairs bend away, the tip links loosen, and the channels shut down.

Conduction deafness

Something hampers sound conduction to the fluids of the inner ear (earwax, perforated eardrum, misalignment of ossicles)

Sensorineural deafness

Damage to neural structures at any point from cochlear hair cells to auditory cortical cells

Tinnitus

Ringing or clocking sound in absence of auditory stimuli. Can occur when the hair is broken causing leaky signals.

Meniere’s syndrome

Labyrinth disorder that affects cochlea and the semicircular canals causing vertigo, nausea, and vomiting.

Macula of utricle

Horizontal movement

Saccule

Vertical movement

Crista ampullaris in the ampulla of the semicircular canals

Monitor dynamic equilibrium