Special Senses Info.

Transduction

Stimulus is converted into graded receptor potentials

Transmission

Receptor potentials can trigger action potentials, which are conducted along sensory neurons to CNS

Interpretation

Brain/spinal cord gathers and perceives sensory information

Chemoreceptors

Respond to changes in chemical concentrations; smell, taste, oxygen concentration

Nociceptors

Respond to tissue damage; mechanical, electrical, thermal

Thermoreceptors

Respond to moderate changes in temperature

Mechanoreceptors

Respond to mechanical forces that distort receptor; touch, tension, stretch, blood pressure

Photoreceptors

Respond to light; found only in eyes

Sensation

Occurs when action potentials make the brain aware of a sensory event

Perception

Occurs when brain interprets sensory impulses

Projection

Process in which cerebral cortex interprets sensory information as being derived from certain receptors; allows location of the region being stimulated

Sensory Adaptation

Ability to ignore continuous stimuli; involves a decreased response to a particular stimulus from the receptors (peripheral) or along the CNS pathways leading to the cerebral cortex (central)

Exteroceptive Senses

Senses associated with body surface

Interoceptive Senses

Senses associated with changes in the viscera

Proprioceptive Senses

Senses associated with changes in muscles, tendons, and joints, body position

Free Nerve Endings

Type of mechanoreceptor, common in epithelial tissue, simplest receptors, sense itching and other sensations

Tactile Corpuscles

Abundant in hairless portions of skin and lips, detect fine touch and texture, distinguish between 2 points

Lamellated Corpuscles

Nerve endings encased in large ellipsoidal structures, common in deeper subcutaneous tissues, tendons, and ligaments, detect heavy pressure and vibrations

Thermoreceptors

Free nerve endings in skin (not mechanical)

Warm receptors

Sensitive to temps between 25 C (77 F) and 45 C (113 F)

Cold Receptors

Sensitive to temps between 10 C (50 F) and 20 C (68 F)

Nociceptors

Respond to temps below 10 C and above 45 C

Nociceptors

Consist of free nerve endings widely distributed in body, not present in brain, adapt very little

Referred Pain

Visceral pain that feels as though it is coming from another part of the body

Common Nerve Pathways

Reason why referred pain occurs; sensory impulses from visceral organ and dermatome synapse with the same CNS neuron

Fast Pain (A-delta) Fibers

Myelinated; conduct impulses rapidly (up to 30m/sec); associated with sharp pain in localized skin area; usually stops when stimulus stops

Slow Pain (C) Fibers

Unmyelinated; conduct impulses slowly (up to 2 m/sec); associated with dull, aching pain; difficult to localize; pain continues after stimulus stops

Reticular Formation

Original area in brain where pain fibers first synapse before moving to thalamus, hypothalamus, and cortex

Thalamus

Begins sensation of pain

Cerebral Cortex

Judges pain intensity, locates pain source, produces emotional and motor responses to pain

Serotonin, endorphins, enkephalins

3 pain inhibiting substances produced in the body

Lamellated Corpuscles

Pressure receptors in joints (specific)

Muscle Spindles

Stretch receptors in skeletal muscles, initiate stretch reflexes, in which it stretch causes muscle contraction

Golgi Tendon Organ

Stretch receptors in tendons, stimulates reflexes that oppose stretch reflexes; helps maintain posture and protects muscle attachments from being pulled loose

Bipolar Neurons

Cell type that olfactory receptor cells are

Olfactory neurons

Have knobs at distal ends of dendrites covered with cilia

Nasal cavity, superior nasal conchae, nasal septum

3 places where olfactory receptors are found

400

number of olfactory membrane receptor types

Taste buds

Located on papillae of tongue, roof of mouth, lining of cheeks, walls of pharynx

10,000

Number of taste buds

50-150

Range of number of taste cells on a taste bud

Taste cells

Modified epithelial cells that function as receptors

Taste hairs

microvilli that protrude from taste cells through pores of taste buds, sensitive part

Sweet

Taste stimulated by carbs

Sour

Taste stimulated by acids

Salty

Taste stimulated by salts (Na or K)

Bitter

Taste stimulated by many organic compounds, Mg and Ca salts

Umami

Taste stimulated by some amino acids, msg

Facial, vagus, glossopharyngeal

3 nerves that carry taste to medulla oblongata, thalamus, and insula

Auricle

Pinna; funnel-shaped, collects sound waves; outer ear

External Acoustic Meatus

S-shaped tube, lined with ceruminous glands, carries sound to tympanic membrane, outer ear

Tympanic Membrane

Vibrates in response to sound waves, outer ear

Tympanic cavity

Middle ear; air filled space in temporal bone

Auditory Ossicles

3 tiny bones, vibrate in response to tympanic membrane and amplify force; middle ear

Oval Window

Middle ear; opening in wall of tympanic cavity; stapes vibrates against it to move fluid in the inner ear

Tympanic Reflex

Muscles contractions that occur during loud sounds to lessen the transfer of sound vibrations to inner ear and prevent hearing damage

Tensor Tympani

Part of tympanic reflex; muscle; pulls malleus away from tympanic membrane

Stapedius

Pulls stapes away from oval window during tympanic reflex

Auditory Tube

Eustachian tube; connects middle ear to throat to maintain air pressure on both sides of tympanic membrane; closed by valve-like flaps in throat

Otitis media

Middle ear infection caused by bacteria traveling from throat/nasal passages to inner ear

Tympanostomy tube

Drains fluid through small opening in tympanic membrane

Osseous Labyrinth

Bony canal in temporal bone filled with perilymph

Membranous Labyrinth

Tube inside osseous labyrinth; filled with endolymph

Oval Window

Opening in wall of tympanic cavity through which the stapes transfers vibrations to fluid of the inner ear; vibrations stimulate hearing receptors

Round Window

Window in wall of inner ear facing the tympanic cavity; dissipates excess vibrations into tympanic cavity

Modiolus

Bony core of cochlea

Scala vestibuli

Part of cochlea; upper compartment of bony labyrinth; lead from oval window to apex of spiral

Scala tympani

Part of cochlea; lower compartment of bony labyrinth; extends from apex of cochlea to round window

Cochlear Duct

Part of cochlea; middle compartment of membranous labyrinth; contains receptor organ for hearing

Vestibular membrane

Part of cochlea; separates scala vestibuli from cochlear duct

Basilar Membrane

Part of cochlea; separates duct from scala tympani; forms floor of cochlear duct

Tectorial membrane

Extends partially into cochlear duct; forms roof of spiral organ

Spiral organ

Organ for hearing; sits on upper surface of basilar membrane; contains hair cells

Hair cells

Hearing receptor cells

Stereovilli

On hair cells

Cochlear nerve

nerve where nerve impulses for hearing are generated

Static equilibrium

Organs located in vestibule

Utricle and saccule

2 expanded chambers of the membranous labyrinth of vestibule

Macula

Inside each utricle and saccule; organ of static equilibrium; made of hair and supporting cells

otoliths

Calcium carbonate crystals inside gelatinous material of macula

Ampulla

In each semicircular canal; a swelling of the membranous labyrinth that communicates with the vestibule

Crista ampullaris

sensory organ for dynamic equilibrium; contains hair and supporting cells; located in ampulla

Cupula

Formed when hair cells of crista ampullaris extend upwards into a dome-shaped gelatinous mass

palpebrae

eyelids

orbicularis oculi

muscles that closes eyelid

levator palpebrae superioris

muscle that opens eyelid

tarsal glands

secrete oil onto eyelashes

conjunctiva

mucous membrane that lines eyelid and covers portion of eyeball

lacrimal gland

in orbit lateral to eye; secretes tears

canaliculi

2 ducts collect tears

lacrimal sac

collects tears from canaliculi; lies in groove in lacrimal bone

nasolacrimal duct

collects from lacrimal sac; empties tears into nasal cavity

lysozyme

antibacterial component of tears

superior rectus

rotates eye up and medially

inferior rectus

rotates eye down and medially

medial rectus

rotates eye medially

lateral rectus

rotates eye laterally

superior oblique

rotates eye down and laterally

inferior oblique

rotates eye up and laterally

fibrous tunic

cornea + sclera