Ch 13 & 15, general sense and special sense , FINAL EXAM

General senses

• Sensory receptors not concentrated in special organs

• Include detection of, temp, pain, touch, pressure. Vibration, proprioception

Types of sensory receptors:

• Nocicerecptors

• Thermorecptors

• Chemorecptros

• Mechanorecptors

  • Bareorecptors

  • Proprioceptors

  • Tactile receptors

Nocicerecptors

• May be senstive many stimuli:

  • Temp extremes

  • Mechanical damage

  • Dissolved chemicals (injured cells)

• Free nerve endings with large receptive fields

THERMORECEPTORS (temperature receptors)

• Temperature sensations conducted along the same pathways as pain sensations 

• Free nerve endings located in:

  • Dermis 

  • Skeletal muscles liver 

  • Hypothalamus 

CHEMORECPTORS

• Detect chemicals in the body

• Respond to only dissolved

  • Water soluble substances

  • Lipid soluble substances

• Unconscious viceral receptors

• Adapt quickly (perioud of seconds)

MECHANORECPTORS

• Sensitive to stimuli that distort their plasma membranes

• Contain mechanically gated ion channels

  • Gates open or close in response to, stretching, compression, twisting, and other distortions of the membrane

Three classes of merchanoreceptors:

1. Barocrecptors

2. Prorioceptors

3. Tactile receptors

BARORECEPTOR

• Respond to change in pressure, adapt rapidly

• Free nerve endings that branch within elastic tissues

• Walls of blood vessels, digestive, respiratory, and urinary tracts

 PROPRIOCEPTORS

• monitor:

  • Position of joints

  • Tension in tendons and ligaments

  • State of muscular contraction 

 TACTILE RECEPTORS

• Touch sensations (shape or texture)

• Pressure sensations (degree of mechanical distortion)

• Vibration sensations (pulsing or oscillating pressure)

• fine touch and pressure receptors:

  • Narrow receptive field, detailed info abt stimulus

• Crude touch

  • Large receptive fields

    • Poor localization, little info abt stimulus

Olfaction (smell) :

• Odorants bind directly to neuron

Taste, vision, hearing, equilibrium:

• Specialized receptor cell stimulated

• Cell release neurotransmitters

• Neuron stimulated

Olfactory organs

• Upper nasal cavity on either side of nasal septum

• Two cell layers

  • Olfactory epithelium

  • Lamina propria

Olfactory glands (Bowman's glands)

• Produces mucus that coats olfactory organs

• Dissolves odorants

olfactory receptors function

detect dissolved chemicals

taste (gustation)

information about the foods and liquids consumed

taste receptors (gustatory cells)

• On tongue, portions of pharynx and larynx

• Extend microvilli (taste hairs) through taste pore

  • Detects dissolved chemicals

• Last 10 days before replacement 

• Receptors clustered into taste buds

taste buds contain :

• basal (stem) cells

• gustatory receptor cells

taste buds are grouped into what?

lingual papillae, epithelial projections on superior surface of tongue

Accessory structures of the eye:

• Palpebrae (eyelids)

• Eyelashes

• Lacrimal caruncle

• Conjunctiva

• Lacrimal apparatus

The eye:

Hollow with two cavities filled with fluid or gel

1. Large posterior cavity

2. Smaller anterior cavity

outer fibrous layer of the eye

• sclera

• cornea

sclera

• Protection, muscle attachment

• Collagen and elastic fibers

• White of the eye

cornea

• Transparent layer

• Directs light into eye

The vascular layer of the eye:

• Iris

• Pupil

• Ciliary body

• choroid

iris

• Regulates light entering eye

• Pupillary muscles (smooth muscle) change diameter of pupil

pupil

eye opening

1. Ciliary body and 2. choroid

• holds lens in place, changes shape of lens, secrets aqueous humor

• choroid, delivers oxygen and nutrients to retina

inner nervous layer

• Neural layer (retina)

  • photoreceptors

    • cones and rods

  • macula

  • optic disc

The inner nervous layer of the eye has an inner sublayer called?

neural layer (retina)

• Contains photoreceptors and associated neurons

Neural layer (retina), PHOTORECEPTORS

• Rods, grey light

  • Don't discriminate colors

  • Responds to almost any photon, highly sensitive to light

• Cones, provide color vision

Neural layer (retina) has what kinds of cells

• bipolar, connect rods and cones to ganglion cells

• ganglion, transmit action potentials to brain

• horizontal, where bipolar cells synapse w photoreceptors

• amacrine, where bipolar cells synapse w ganglion cells

The macula

• Oval shaped pigmented area at the center of the retina

• Contains densely clustered cones in small depression (fovea), which is the area of sharpest vision

The optic disc:

• Circular region just medial to fovea

• Origin of optic nerve

  • Blind spot because there aren't any photoreceptors

lens

• fibers

  • Cells in interior of lens

  • Produced by lens epithelium, migrate to middle of lens

  • Mature cells have no nuclei or organelles, filled with crystallions, which provide clarity and focusing to power lens 

Light refraction:

• Bending of light by cornea and lens

  • Focal point, specific point of intersection on retina 

  • Focal distance, Distance between center of lens and focal point

  • Accommodation, Shape of lens changes to focus image on retina

Anatomy of rods and cones:

• Outer segment, membranous discs with visual pigments

• Inner segment, cell function

Anatomy of rods and cones: VISUAL PIGMENTS (RHODOPSIN) 

• Where ligbt absorption occurs

• Composed of covalently bonded opsin and retinal (syntesized from vitamin A)

Photoreception

• at rest cell releasing neurotransmitters, Na + gates are help open by cGMP, and Na+ cycles through cells

• Photon strikes retinal portion of rhodophin molecule in disc, this converts retinal from 11-cis form to 11-trans form, which activates opsin 

opsin creates

• Protein Chain reaction

  • cGMP is removed from Na channels

  • NA channels close

  • Neurotransmitters reduced

  • Neuron detects change 

Bleaching is?

recovery after stimulation

Rhodopsin breaks down retinal and opsin

Process of detecting light:

• Sodium movement

• Light changing shape for retinal

• Activation of opsin and sequence of chain reactions

• Sodium channels closed

• Neurotransmitters reduced

external ear

• Auricle 

• External acoustic meatus

• Ceremonious glands

auricle

• Protects opening of canal

• Provides directional sensitivity

• Sounds entrance to external acoustic meatus

external acoustic meatus

propels sounds to eardrum

the middle ear

• Tympanic membrane

• Tympanic cavity and auditory tube

• Auditory ossicles

tympanic membrane

• Vibrates in response to sound waves

• A thin, semitransparent sheet between outer and middle ear

tympanic cavity

• Connected to nasopharynx via auditory tube

  • Equalizes pressure to outside

The middle ear encloses and protects three auditory ossicles:

• Malleus (hammer)

• Incus (anvil)

• Stapes (stirrup)

Internal ear:

• contains fluid called endolymph

• Vestibule

• Semicircular canals

• Cochlea

• Oval window 

• Round window

vestibule

Enclose saccule and utricle, which detect quality and linear acceleration

semicircular canals

contain semicircular ducts, stimulated by rotation of head

cochlea

contain cochlear duct (elongated portion of membranous labyrinth), sense of hearing

hair cells

• Equilibrium and hearing detected by hair cells in inner ear 

• Sterocilia

• Kinocilium

equilibrium:  Sterocilia and kinocilium: 

• hair cells in the inner ear

• When sterocilia move toward kinocilium, cells depolarize (sends signal)

• When sterocilia move away from kinocilium, cell hyperpolarizes

Equilibrium : SEMICIRCULAR DUCTS

• Detect rotation movement 

• Each duct contains an ampulla

  • When the head rotates in the plane of semicircular duct, movement of the endolymph pushes against the ampullary cupula and stimulates hair cells

  • Each duct responses to 1 of 3 movements 

The utricle and saccule:

provide equilibrium sensations

Utricle and saccule, MACULAE:

Oval structures where cells cluster

• Utricle and saccule

  • Maculae

    • OTOLITH:

• When the head tilts, the pull of gravity on the otoliths shifts weight to the side, distorting sensory hairs

  • This change tells CNS that the head is no longer level

• Calcium carbonate crystals

• Pulled by gravity

cochlea has what

• perilymph, fluid in cochlea

• scala vestibuli, canal extending from oval window

• basilar membrane, separates scala vestibuli from scala tympani

• scala typmani, perilmphy extending to round window

Process of a soundwave being detected:

• Tympanic membrane

• Auditory ossicles

• Wave moves through cochlea

• Basilar membrane distorts

Hearing, Tympanic membrane:

vibrates

Hearing, Auditory ossicles:

• Enhance vibration

• Creates greater pressure fluctuations in perilymph of cochlea

vibration of stapes at 6000 Hz causes stapes to move inward, causing distortion to what?

basilar membrane

Stimulation of Basilar membrane:

• As basilar membrane distorts

  • Hair cells become displaced

  • Stimulate cranial nerve VIII

frequency of sound

determined by which part of cochlear duct is stimulated

Production of sound steps:

1. Sound waves arrive at tympanic membrane

2. Movement of tympanic membrane causes displacement of the auditory ossicles

3. Movement of the stapes at the oval window establishes pressure waves in perilymp of the scala vestibuli

4. Pressure waves distort basilar membrane on their way to round window of scala tympani

5. Vibration of basilar membrane causes hair cells to vibrate against tectorial membrane

6. Info about the region and intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII