Ch 19 sensory

1. constantly exposed to sensory information

2. conscious awareness to stimuli

-detect stimuli

•structurally complex sense organs (the eye) or simple endings of single neurons (dendritic endings in the skin)

•General senses -temperature, pain, touch, stretch, and pressure

•Special senses -gustation, olfaction, vision, equilibrium, and hearing

change one form of energy into another

•Ex: Visual receptors change light energy into electrical energy on the optic nerve

Receptors have this:

Areas sensitive ends distributed

constant stimulus, decrease action potential

•Tonic receptors slowly adapt (only slowly decrease firing in response to a constant stimulus)

•Phasic receptors rapidly adapt (fire only in response to changing stimuli) (hair tie)

General sense receptors- throughout skin and organs

-Somatic sensory receptors skin, mucous membranes lining body cavities, joints, muscles, and tendons

• texture, pressure, temperature, pain, vibration, and stretch

-Visceral sensory receptors walls of internal organs & blood vessels

•Detect stretch, changes in chemical, temperature, and pain

Special sense receptors - in complex organs in the head

•smell, taste, vision, hearing, and equilibrium

detect stimuli from external environment

• receptors in skin, body cavity linings and in special sense organs

'Stimulus origin

detect stimuli in internal organs

• stretch receptors in smooth muscle

• receptors for pain, pressure, temperature, and chemical changes in viscera

'Stimulus origin

detect stimuli pertaining to body position

•Found in muscles, tendons and joints

'Stimulus origin

Detect specific molecules dissolved in fluid

'modality of stimulus

Detect changes in temperature

'modality of stimulus

Detect changes in intensity, color, and position of light

'modality of stimulus

1. Detect touch, pressure, vibration, and stretch

2. Detect pressure changes within body structures

'modality of stimulus

Detect painful stimuli

'modality of stimulus

-sensation associated with a part of the body that has been removed

- Excitation of a CNS neuron that was formerly excited by the amputated limb is interpreted as pain in that limb

impulses are perceived as originating not from the organ but in a dermatome of the skin

•Ex: Heart attack, dermatomes of T1–T5

-most numerous type

-mechanoreceptors that react to touch, pressure, and vibration

Located in the dermis and subcutaneous layer

Two types:

•Unencapsulated: endings not wrapped in connective tissue or glial cells

•Encapsulated: endings wrapped in connective tissue or glial cells

unencapsulated tactile receptors

1: papillary layer of dermis and deep epidermis (temp, pain)

2: surround hair follicles in dermis (movement of hair)

3: associated with tactile cells in stratum basale of epidermis (light touch)

encapsulated tactile receptors

1: skin and oral, nasal, vagina, and anal (light pressure/vibration)

2: in dermis, subcutaneous tissue, synovial membranes, and some viscera (course touch, deep pressure)

3: in dermis and subcutaneous layer (continuous deep pressure)

4: in dermal papillae, especially lips, palms, eyelids, nipples, and genitals (texture and shape)

1.sense of smell

2. dissolved in mucus of nasal cavity and detected

1. lining superior nasal cavity

2. detect odors

3. sustain the olfactory receptor cells

4. replace olfactory receptor

lamina propria

•mucin-secreting olfactory glands

- bipolar neurons, primary cells in smell pathway

- a single dendrite with olfactory hairs (cilia) containing receptors for one odorant molecule

•Bundles of axons: olfactory nerves

-mix air with mucus of olfactory epithelium

-eight primary odors (for example, minty)

•Secondary odors (chemicals) not recognized by all

- cells can be mitotically replaced, declines with aging

Axons from bipolar neurons pass through foramina of cribriform plate and enter olfactory bulbs

•Bulbs -mitral and tufted cells

• olfactory glomeruli, olfactory cells converge

Neurons within olfactory bulbs project olfactory tracts, to olfactory cortex of temporal lobe

-sense of taste

Gustatory cells taste receptors in taste buds

dorsal surface of the tongue in epithelial and connective tissues elevations called papillae

1.Filiform papillae: Small numerous bumps lacking taste buds (middle)

2.Fungiform papillae: Mushroom shaped, tip and sides of tongue few taste buds

3.Vallate papillae: “V” back of tongue; many taste buds

4.Foliate papillae: Subtle ridges on (side) few taste buds in early childhood

•Gustatory cells detect tastants (molecules and ions) in food

-Gustatory cells are neuroepithelial cells with a dendritic gustatory microvillus (taste hair, receptive)

•taste hair extends through taste pore

•Supporting cells sustain gustatory cells

•Basal cells neural stem cells that replace gustatory cells (regeneration every 7 to 9 days)

•Sweet - sugars

•Salt - metal ions (Na⁺)

•Sour - acids

•Bitter - alkaloids

•Umami - amino acids

CN VII (facial) anterior two-thirds of tongue

CN IX (glossopharyngeal)posterior one-third of tongue

thalamus then gustatory cortex

- relies heavily on sense of smell

movable anterior protective coverings for eye

1. sebaceous glands ; secretion prevents overflow of tears and sticking together of eyelids

2. space between eyelids

•Medial and lateral palpebral commissures: corners of eyes

3. medial pink bump with ciliary glands that produce gritty secretion

-lining anterior surface (ocular conjunctiva)

internal surface of eyelid (palpebral conjunctiva)

•Stratified columnar epithelium

•Space is conjunctival fornix

•blood vessels and nerves

•goblet cells: lubricate eye

•Does not cover cornea

Produces, collects, and drains lacrimal fluid (tears)

lubricate

Lysozyme in tears -prevent bacterial infections

•Lacrimal gland: produces tears

•Lacrimal caruncle: contains modified sweat glands

•Lacrimal puncta: small “holes” in the caruncle

•Lacrimal canaliculus: drains lacrimal fluid into lacrimal sac

•Nasolacrimal duct: receives tears from lacrimal sac and drains to nasal cavity

-almost spherical organ about 2.5 cm in diameter

Orbital fat cushions the eye within the socket

Anterior cavity(front of the lens)

• circulating aqueous humor

Posterior cavity (behind the lens)

•permanent vitreous humor

•Cornea: avascular- oxygen & nutrients from lacrimal fluid & aqueous humor

-Outer corneal epithelium is stratified squamous

-Cornea meet sclera: limbus

•Sclera: majority of fibrous tunic; white of the eye

•Made of dense irregular connective tissue

•Choroid: capillaries, nutrients & oxygen to the retina

•Ciliary body: has ciliary muscles and ciliary processes; changes lens shape

•Iris: pigmented of eye; defines pupil—controls amount of light entering eye through

-Circular sphincter pupillae

-Radial dilator pupillae

-internal eye

1.Pigmented layer: (outer) attached to choroid; absorbs light passed through retina

• provides photoreceptors with vitamin A, nutrients, oxygen

2. Neural layer: photoreceptors (rod & cone)& neurons

• converts to nerve impulses

jagged margin between photosensitive and nonphotosensitive (anterior) part of retina, near ciliary body

1.Photoreceptor cells: outermost layer

-Rods: dim light

-cones: precise vision and color

- horizontal cells between

2.Bipolar cells: synapse with photoreceptors & ganglion cells

- amacrine cells: between

3.Ganglion cells: innermost layer of the retina; axons leave and form the optic nerve (CN II)

optic disc, no photoreceptors

• ganglion cell axons exit retina to form optic nerve and blood vessels enter/ exit the retina

depression in retina, highest cones and no rods

• sharpest vision

•Located within the macula lutea (lateral to optic disc)

behind pupil. Held by suspensory ligaments- attach outer of lens and tension changes lens’ shape

•Changes in tension are caused by contraction and relaxation of ciliary muscles of ciliary body

making lens spherical, look at thing close

•Parasympathetic fibers excite ciliary muscle; muscle contracts and suspensory ligaments slacken; lens becomes more spherical

1.Anterior cavity: between lens and cornea; filled with aqueous humor

-The iris subdivides this into: anterior chamber and posterior chamber

•Aqueous humor is secreted into posterior chamber; flows through pupil; drained through scleral venous sinus of limbus

2.Posterior cavity: between lens and retina; filled with vitreous humor (gelatinous, permanent)

•Hyaloid canal is remnant of developmental hyaloid blood vessel

Retinal photoreceptors convert light to neural signals

•Stimulus is passed to bipolar and ganglion cells

Axons of ganglion cells form optic nerve

•Optic nerves converge at optic chiasm where axons from medial retina cross

•Optic tracts extend laterally, posteriorly from chiasm

-Most extend to lateral geniculate nucleus of thalamus- then primary visual cortex of the occipital lobe

unite images from left and right eyes

•Some go to superior colliculi to coordinate visual reflexes involving extrinsic eye muscles

•Some go to pretectal nuclei to control pupillary and accommodation reflexes

fourth week optic vesicles form

become optic cups

•Cup contains two layers connected to brain by optic stalk

•Hyaloid vessels enter cup through stalk; later regress leaving hyaloid canal

Ectoderm over optic cup forms a lens pit

•The pit indents to form lens vesicle

1.auricle: funnel-shaped, elastic cartilage structure

2. bony tube, external acoustic meatus, which ends at the 3.tympanic membrane (eardrum)

4.secretion wax like cerumen to impede growth of microorganisms

1.beind tympanic membrane contains air

2.connects middle ear to nasopharynx (throat)

'middle ear

(small bones) transmit sound waves to inner ear

•Malleus between tympanic membrane and incus

•Incus is the middle ossicle

•Stapes between incus and oval window to inner ear

•Stapedius & tensor tympani

-within petrous portion of temporal bone

•bony labyrinth

-fluid-filled tubes and spaces called the membranous labyrinth (Receptors for equilibrium and hearing)

endolymph- middle

perilymph- above and under (scala vestibuli & scala tympani

•Cochlea has cochlear duct

•Vestibule has: utricle and saccule

•Semicircular canals each has a membranous semicircular duct

awareness of head position

Vestibular apparatus consists of sensory receptors:

- utricle and saccule detect static equilibrium (head position when head is stationary) and linear acceleration

- semicircular ducts detect angular acceleration (rotational movements)

- walls of utricle and saccule

- sensory epithelium lining the two maculae contains hair cells and supporting cells

Hair cells’

- 50 stiff microvilli, stereocilia

-one long cilium kinocilium

bend, change neurotransmitter released by the hair cell, changes the electrical activity sent to the brain via the vestibular nerve

(head position)

location top of maculae

-otoliths and gelatin layer with Stereocilia & kinocilium

head tilts, otoliths push gelatin, bends stereocilia of the hair cells

=neurotransmitter release = changes sensory neuron activity (head position)

semicircular canals (Anterior, posterior, and lateral) are continuous with the utricle

with semicircular duct ending with -ampulla

detect rotational movement of the head

ampulla - near semicircular duct

cupula- dome gelatin with stereocilia and kinocilia

-crista ampullaris inside dome, has hair cells

-head rotates, endolymph pushes against the cupula and bends the stereocilia

hair cell neurotransmitter release and the activity of the sensory neurons

- hair cells in vestibule or semicircular canal change their transmitter release, impulses initiated on vestibulocochlear nerve (CN VIII)

-Vestibular axons project to vestibular nuclei in the medulla oblongata or to cerebellum

•Vestibular nuclei: reflexive eye movements

•Cerebellum: coordinate balance

relayed to thalamus and cerebral cortex for awareness of body position

1: inner ear organ of hearing

2 Snail shaped with bony axis

3 Membranous labyrinth(fluid) inside cochlea (endolymph)

4.•Scala vestibule (perilymph)

•Scala tympani (perilymph)

-of cochlea is a thick sensory epithelium with hair cells and supporting cells on the basilar membrane

• row of inner hair cells (hearing)

•3 rows of outer hair cells (help tune spiral organ response to sounds)

The stereocilia and kinocilium of each hair cell project into gelatinous mass tectorial membrane

base of hair cells are sensory neurons that have their cell bodies in spiral ganglia

- auricle into external acoustic meatus

-Tympanic membrane vibrates = move ossicles

-Stapes moves oval window, transmitting sound to inner ear

-Pressure waves in perilymph of scala vestibuli deform cochlear duct

•Region of basilar membrane that matches sound frequency is displaced

-Stereocilia of hair cells bent = impulses in cochlear branch of vestibulocochlear nerve

# of waves per unit of time

• hertz (Hz); pitch of a sound

•Influences which part of spiral organ is stimulated

High frequency near oval window; low far

-Bending of stereocilia = impulses on cochlear nerve

-Sensory axons of cochlear nerve terminate in cochlear nuclei of brainstem and synapse with secondary neurons

-Secondary axons travel to either superior olivary nuclei ( sound localization) or inferior colliculi

-From inferior colliculus, nerve impulses travel to medial geniculate nucleus of thalamus and then to primary auditory cortex of temporal lobe

fourth week

External acoustic meatus forms from first pharyngeal cleft

Tympanic cavity and auditory tube form from first pharyngeal pouch

•Pouch first grows into tubotympanic recess

Tympanic membrane forms from first pharyngeal membrane

Inner ear forms from otic placode

•Placode invaginates forming otic pit

•Otic pit closes to become otocyst—primitive precursor to inner ear

Sound waves are detected by the receiver and turned into electrical impulses, which travel through the transmitter.

stimulatecochlear nerve, which then transmits nerve impulses to the brain.

-measured in decibels dB

-louder sound stimulate more hair cell = higher rate of nerve impulse on cochlear nerve