Peripheral Nervous System

sensation

receptors transducing stimuli into nerve impulses that are conducted into the CNS

perception

assigns meaning to that info within the brain

general (somatic) senses

touch, pressure, temperature, and pain

special senses

vision, olfaction, hearing, gustation

thermoreceptors

sensitive to temperature

mechanoreceptors

sensitive to mechanical changes

stretch stimulus

when plasma membrane stretches in response to body movements

nociceptors

sensitive to physical tissue damage

photoreceptors

sensitive to light

chemoreceptors

sensitive to chemicals

exteroceptors

sense our external environments

interceptors

sense our internal environment

proprioceptors

give info about our body position in space and each body part relative to one another

where are proprioceptors located

within muscles and joints

free nerve endings

embedded in tissue where they respond to sensation

encapsulated nerve endings

dendrites encapsulated in connective tissue

specialized senses

have specialized epithelial cells that synapse with neurons

sensory unit

a neuron and all of its receptors on its dendrites

receptive field

the area/region that can be sensed by a sensory unit

receptor potential

synaptic/graded potential seen at a receptor

receptor potential is impacted by what

stimulus intensity

stronger stimuli can ____

recruit additional sensory neurons or send multiple action potentials

sensory adaptation

desensitization to repeated or prolonged stimuli

types of adapting receptors

phasic and tonic

phasic receptors

rapidly adapting; stop sending action potentials

tonic receptors

slowly adapting; response slows down but stays continuous

the larger the receptor field, the ____ ability to discriminate two points

lesser

highest receptor density is in the ____

fovea of the eye

processes that allow us to localize/discriminate a sensation

smaller receptor fields, receptor field overlap, lateral inhibition

lateral inhibition

the secondary neuron that receives the most neurotransmitters synapses with the other secondary neurons to inhibit their neurotransmitter release

lateral inhibition is an example of an ______ synapse

axo-axonic/presynaptic

GABA

inhibitory neurotransmitter

first order neuron

receptors in body tissues, axon travels through the body to spinal cord where it synapses

second order neuron

responsible for decussation, synapses in the thalamus

third order neuron

has cell body in thalamus and terminates in somatosensory cortex

dorsal column pathway

information travels up through dorsal column in white matter of spinal cord; decussation occurs in medulla

spinothalamic pathway

information travels up through lateral or anterior spinothalamic tracts in white matter; decussation occurs in the spinal cord

info carried through dorsal column

fine tough and proprioception

tracks in the dorsal column

Fasiculus gracilis and Fasiculus cuneatus

info carried through spinothalamic pathway

pain, temp, crude touch

three layers of the eye

outer fibrous, intermediate vascular, and deep nervous layers

fibrous layer of the eye contains

sclera and cornea

vascular layer of the eye contains

iris, choroid, and pupil

nervous layer of the eye contains

retina

myopia

near-sightedness; lens can’t flatten enough or eye is too long

hyperopia

far-sightedness; lens can’t bulge enough or eye is too short

rods and cones in retina

photoreceptors

rods give

general shape

cones give

color

fovea is made up of

cones

bipolar cells in eye

intermediate cells between photoreceptors and ganglion cells

horizontal and amacrine cells

integrate info from multiple photoreceptors

ganglion cells

become part of the optic nerve

lateral portions of the eye receive info from ____ side of visual field

opposite

medial portions of the eye receive info from ____ side of visual field

same

axons from ____ portion of eye cross through the optic chiasm

medial

axons from ____ portion of eye do not cross over in the brain

lateral

regions of the ear

external, middle, and inner

role of external ear

sound conduction

parts of external ear

auricle and external acoustic meatus

role of middle ear

sound waves converted to mechanical sound

parts of middle ear

tympanic cavity, tympanic membrane, auditory ossicles

role of inner ear

specialized receptors detect pitch and amplitude

oval window

barrier between middle and inner ear

parts of inner ear

cochlea and vestibulocochlear nerve

parts of the cochlea

perilymph and basilar membrane

perilymph

fluid in cochlea that vibrates, displacing basilar membrane

basilar membrane

vibrates ciliated receptor cells that stimulates cochlear nerve

apex of cochlea detects ___

low frequencies, which is perceived as low pitch

base of cochlea detects ____

high frequency, which is perceived as high pitch