ch 6 pns afferent and special senses

PNS

nerve fibers that carry info bw cns and other parts

Afferent division

detects, encodes and transmits peripheral signals to the cns

Receptors

structyres at oeripheral endings of afferent neurons that detect stimulus

transduction

receptor converts forms of energy into electrical signals/action potentials,

photoreceptors

responsible to visible wavelengths of light

mechanoreceptors

sensitive to mechanical energy

thermoreceptors

sensitive to heat and cold

osmoreceptors

detects changes in solute concentration in body fluids and changes in osmotic activity

chemoreceptors

respond to chemicals, includes smell, taste, o2, co2, and chem content in digestive tract

nociceptors

pain receptors

receptors permeability

altered by stimulus leading to graded receptor potential

nonselective opening of all small ion channels can be caused by

receptors

receptor generator potentials

changes in membrane permeability can cause an influx of sodium ions making this, magnitiude represenst the intensity of the stimulus, can cause an action potential

Tonic receptors

do not adapt or adapt slowly ex. muscles or joint proprioceptors, must continually get information about degree of muscle length and joint position (always making APs)

phasic receptors

rapidly adapting, doesnt respond to maintained stim, signals a change in stimuus intensity ex. touch receptos

somatosensory pathways

conveys conscious somatic sensation, chains of neurons synaptically interconnected

acuity

refers to discriminative ability influenced by receptive field size and lateral inhibition

perception

interpreting of external world from sensory input

pain

protective mechnism, avoids harmful events in future, stimulates noicereceptors

Substance P

A neurotransmitter that is involved in the transmission of pain messages to the brain.

Brain's analgesic system

suppresses transmission of pain depending on presence of opiate receptors like endorphins, enkephalins, dynorphon

Sclera

white of the eye

cornea

The clear tissue that covers the front of the eye, allow light to pass into interior of eye

choroid

middle, vascular layer of the eye, between the retina and the sclera, specialized to form ciliary body and iris

retina

innermost coat under choroid, has outer pigmented layer and inner nervous tissue layer

Rods(night) and cones(color)

photoreceptors that convert light energy to nerve impulses

Vrteus humor

bw lens and retina, jelly fluid, maintains shape of eye

aqueous humor

bw cornea and lens, watery, nutrients and made by capillary network wi cilliary body.

Iris

controls light intrance, 2 smooth muscle(circular/constrictor and radial/dilator)

Pupil

round opening through which light enters

Cornea and light refraction

light passes thru, contributes a lot to the eyes refractive ability, never changes its ability

Lens and light refraction

can be adjusted by changing curvature

Accomodation

ability to adjust strength of lens, depends on shape, regulated by ciliary muscle

presbyopia

age related decreaseof accomadation

Retinal layers (retina)

receptor contating portion is an extension of CNS

What are the outermost cells of the neural portion of the retina?

Rods and cones

What type of cells are found in the middle layer of the neural portion of the retina?

Bipolar cells

What cells are located in the inner layer of the neural portion of the retina?

Ganglion cells

What is the point on the retina where the optic nerve leaves called?

Optic disc or blind spot

Fovea

pin head sized depression in exact center of retina, most distinct vison, only cones

Macula Lutea

around fovea, fairly high acuity

macular degeneration

progressive damage to the macula of the retina

Photoreceptors/rod and cones cells (outer)

detects light

Photoreceptors/rod and cones cells (inner)

contains metabolic machinery of cell

Photoreceptors/rod and cones cells (synaptic terminal)

transmits signal generated in photoreceptor from light to the next cells

photopigments

chemicals in photoreceptors that respond to light and assist in converting light into neural activity

Opsin

part of photpigments, protein that is an integral part of the disc membrane

Retinene

vit A derivative, light absorbibg part of photopgment

Rhodopsin

the pigment in rod cells that causes light sensitivity, absorbs all visible wavelength

Dark Adaptation

The process in which the eyes become more sensitive to light in low illumination due to the regeneration of rod pigments that were broken before from light.

Light Adaptation

the recovery of the eye's sensitivity to visual stimuli in light after exposure to darkness, due to the breakdown of cone pigments

External&middle ear

transmit sound waves to fluid filled inner ear, amplifies sound energy

Inner ear

houses 2 diff sensory systems (cochlea, and vestibular apparatus)

Cochlea

a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses, makes hearing possible

Vestibular apparatus

necessary for sense of equilibrium

Hearing

nerual perception of spund energy involves identification and localization of sounds

Sound Waves

traveling vibrations of air, consist of alternate regions of compression and rarefaction of air molecules

Pitch

depends on frwuency of air waves

Intensity

depends on amplitude of air waves

Timbre

Overtones

Sound Wave Transmission

-Tympanic membrane vibrates when struck by sound waves

-Middle ear transfers vibrations through ossicles (malleus, incus, stapes) to oval window (entrance into fluid-filled cochlea)

-Waves in cochlear fluid set basilar membrane in motion

-Receptive hair cells are bent as basilar membrane is deflected up and down

-Mechanical deformation of specific hair cells is transduced into neural signals that are transmitted to auditory cortex in temporal lobe of brain for sound perception

Semicircular canals

part of vestibular apparatus, that detects rotational acceleration or deceleration in any direction

utricle and saccule

detects changes rate of linear movement and inofrmatant to determine heads position in relation to gravity, part of vestibular apparatus.

Equilibrium

neural signals made in response to mechanical deformatino of hair cells by specific movement of fluid and related structures, the vestibular input goes to vestibular nuclei in brain stem and to cerebellum

taste and smell

uses chemoreceptors, along w food intake influnece flow of digestive juices and appetite, stim of receptors induces pleasurable or objectionable sensations and signals presence of smth to seek or to avoid

taste

chemorecetors in taste buds, found oral cavity and throat, lifespan od 10 days, taste buds consist of taste pores, and receptor cells

taste pore

opening through which fluids in mouth come into contact w surface of receptor cells

taste receptor cells

modified epithelial cells w surface folds called microvilli, the microvillis plasma membrane has receptor sites that bind w chem molecules

tastant

taste provoking chem, binds to receptor cell and alters cell's iconic channels to make depolarizing receptor potential, the receptor potential causes a action potential which travels to cranial nerves and goes to brainstem, then thalamus to cortical gustatory area.

Primary tastes

sweet-evoked by configuaration of glucode, sour- caused by acids H+, salty-chemical salts, bitter- chemically diverse group of tastants, umami-meaty or savory taste

Taste Perception

influenced by information deriveed from receptors like odor, temp, taste, nostalgia

smell

olfactory receptors are specialized endings of renewable afferent neurons,

olfactory mucosa

has olfactory receptor cells, supporting cells, basal cells

odorants

molecules that can be smelled, must be volatile and water soluble