chapter 18: general and special sense

sensory receptors

specialized cells that monitor the condition in the body or the environment

General sense

temperature, pain, touch, pressure, vibration, and proprioception ( knowing where your body is in a space )

Special sense

smell, taste, balance, hearing, and vision ( goes directly to the brain )

free nerve ending

• simplest receptor

• dendrites of sensory neurons

• responds to a variety of stimuli

receptive fields

• large - receptors spread far apart, harder to localize stimuli

• small - close together

• Two-touch test

tonic receptors

• interpretations of sensory information

• always active

• photoreceptor of the eye and a receptor that constantly monitors body position

Phasic receptor

• interpretation of sensory information

• normally inactive but become active when necessary (for short periods of time )

  • touch and pressure receptors of the skin

  • adaptation

adaptation

• reductions in sensitivity due to a constant stimulus

• temperature

• spice

• volume

exteroceptors

• external environment

• based on location ( general senses )

Proprioceptor

• position of the body

• based on location ( general senses )

Interoceptors

• Monitors the internal conditions to help maintain homeostasis

• based on location ( general senses)

Nociceptors

• based on stimuli ( general sense )

• sensation of pain

Thermoreceptors

• based on stimuli ( general senses )

• change in temperature

Mechanoreceptors

• based on stimuli ( general senses )

• physical distortion of cell membranes

chemoreceptors

• based on stimuli ( general senses )

• chemical composition of body fluids

Nociceptors

• pain receptors

• free nerve endings and large receptor fields

  • difficult to “ pinpoint” the origin of the pain

• fast pain

• slow pain

• referred pain

fast pin

pricking pain or cuts

slow pain

burns or aching pains

referred pain

• Visceral organ pain felt elsewhere- reaches the spinal cord via the same dorsal root

• pain that’s happening in an organ is happening in another part of the body

thermoreceptors

• changes in temperature

• in the dermis, skeletal muscles, liver, and hypothalamus - free nerve endings

• phasic receptors

thermoreceptors

more cold than hot receptors - bc cold is more dangerous for you

phasic

transmitted along pain pathways

mechanoreceptors

• respond to physical disruption to the membrane, constant or pressure

• There are three types

  • tactile receptors

  • baroreceptors

  • proprioceptors

Tactile receptors

receptors that detect touch, pressure, and vibration

Baroreceptors

pressure changes within organs and help determine if you are full or not

Proprioceptors

position of joints and muscles

tactile response

• sensation of touch, pressure, and vibration

  • unencapsulated tactile receptors

  • encapsulated tactile receptors

unencapsulated tactile receptors

free nerve endings, tactile discs, and toot hair plexus

encapsulated tactile receptors

• tactile (Meissner’s) corpuscles

• bulbous ( ruffini ) corpuscles

• lamellar ( pacinian ) corpuscles

• have a layer of connective tissue covering the tip of nerve endings

pacinian corpuscles

• deeper in the dermis

• responds to heavy pressure, pulsing, and frequency vibration stimuli

ruffini corpuscles

• in dermis, sensitive to pressure and distortion of the skin

• pulling on skin

• Bulbuls

meissner’s corpuscles

• detect light touch, movement, and vibrations ( eyelids, nipple, finger tips, lips, external genitalia )Tactile (

Baroreceptors

• stretch receptors that monitor changes in the stretch of organs, pressure changes

• Monitor changes in your organ

• lets you know when you need to expel your waste

proprioceptors

monitior the postition of joints

proprioceptors

monitor tension in the tendons and ligaments

proprioceptors

Monitor the length of muscle fibers upon contraction

chemoreceptors

• Monitor the chemical composition of body fluid and respond to the presence of specific molecules

found in

• The medulla oblongata - CSF

• carotid artery and aorta - blood

olfaction

• chemical sense, tastes ( taste is mostly smell)

  • 10 - 100 million receptors

  • have to dissolve in something to pick up information

olfactory epithelium

superior portion of the nasal cavity, cribriform plate

• includes

  • olfactory sensory neurons

  • supporting cells

  • basal epithelia cells

olfactory sensory neurons

____ are bipolar neurons

supporting cell

columnar epithelium

basal epithelial cells

between support cells, eventually divides to replace worn-out olfactory sensory neurons

olfactory gland

produces thick mucus, dissolves odorants (Bowman’s)

olfactory discrimination

• Receptors have different sensitivities

  • “ detect” different smells

• olfactory receptors can be replaced

  • declines with age

adaptations to odors occur quickly

• few molecules

• completely insensitive after 1 minute

gustation ( taste )

• chemical sense

• stimulating molecules must dissolve

• Receptors located in the taste buds

  • gustatory epithelial cells

  • lingual papillae

Gustatory epithelial cells

• taste hair

• replaced every 10 - 12 days

Lingual papillae

• on the tongue

• four types

  • filiform

  • fungiform

  • foliate

  • vallate

• molecules have to dissolve to taste

Gustatory discrimination

• There are four (possibly six ) primary taste sensations

  • sweet, salty, sour, bitter

  • umami- amino acids, glutamate

  • water - pharynx

• Taste is mostly smell

Inner ear

consists of :

• bony labyrinth

  • vestibular complex

  • cochlea

• membranous labyrinth

  • hair cells

  • endolymph

vestibular complex

equilibrium

cochlea

A structure in the ear used for hearing

membranous labyrinth

within the boney labyrinth

hair cells

embedded in a gelatinous

endolymph

perilymph

the vestibular complex and equilibrium

• provides equilibrium sensation by detecting rotation, gravity, and acceleration

consists of :

• semicircular canals

• utricles

• saccule

the inner ear

The vestibular complex creates the :

• hair cells

• semicircular canals

• utricle and saccule

semicircular canals

this structure monitors head rotation

utricle and saccule

• oval maculae

  • otoliths

otoliths

calcium carbonate crystals

utricle and saccule

when you move up or down ( elevator movement )

• otoliths rest on top of the maculae

• When moving upward, the otoliths press down on the macular surface

• When moving downward, the otoliths lift off the macular surface

When you tilt side to side :

• When tilting to one side, the otoliths shift to one side of the macular surface

hearing

the cochlea

• hair cells

• tectorial membrane

all help in ___

hair cell

• receptor cells

  • localized within the organ of Corti ( spiral organ )

Tectorial membrane

a structure in the cochlea that distorts with sound waves

detection of sound waves ( pressure waves )

• sound waves enter the external acoustic meatus

• vibrates the tympanic membrane → ossicles → oval window

• creates pressure waves through the perilymph

• distorts the tectorial membrane, stimulating the organ of Corti

• sends a signal to the cochlear nerve

Vision

• components of our visual system include

  • accessory structures

  • the eye

this creates our ___

accessory structures of the eye

• palpebrae ( eyelids )

• eyelashes

• glands

palpebrae

• eyelids

• palpebral fissure

• medial and lateral canthus

• conjunctiva

palpebral fissure

• area between the eyelids and the eye

medial and lateral canthus

• connect the eyelids at the corners of the eye

conjunctiva

• epithelial lining of the eyelids

eyelashes

contain root hair plexus, which triggers the blinking reflex

glands

glands of Zeis, tarsal glands, lacrimal glands, lacrimal caruncle

the eye

consists of :

• three layers

• fibrous layer

• vascular layers

• inner layer ( retina )

anterior cavity

• anterior chamber

• posterior chamber

posterior cavity

fibrous layer

• outer layer

• consists of sclera and the cornea

  • The cornea is modified sclera

Fibrous layer

provides mechanical support and protection of the eye

sclera

attachment site for the extrinsic eye muscles

• fibrous layer

cornea

contain structures that assist in eye focusing

• Fibrous layer

Vascular layer

a layer that contains :

• iris, pupil, ciliary body, choroid

Vascular layer

provides a route for lymphatic vessels and blood vessels of the eye

Pupil

A layer regulates the amount of light entering the eye

• Vascular layer

vascular layer

secretes and reabsorbs the aqueous humor

ciliary body

controls the shape of the lens

• in vascular layer

Retina

contains :

• macula lutea, fovea centralis, optic disks

  • rods and cones

  • inner layer

retina

where preliminary processing and integration of visual info happens

retina

contains photoreceptors that respond to light

• rods

• cones

inner layer

rods

light sensitive allowing vision in dim light

cones

provides color vision, gives shape, and provides clear vision

retina

supply nutrients to the tissue lining the posterior cavity

Anterior cavity

• anterior chamber

• posterior chamber

• filled with fluids called aqueous fluid

  • similar to CSF

  • glaucoma

glaucoma

when fluid cannot drain ( puff test pressure)

Posterior cavity

• vitreous chamber

• filled with fluid called vitreous fluid ( humor )

vitreous humor

support the shape of the eye and position of the lens and retina

detached retina

What happens when the fluid is not the right consistency

lens

posterior to the cornea

lens

held in place by suspensory ligaments

lens

Focus the visual images on the retina photoreceptors