quiz #3 Flashcards
conscious or subconscious awareness of changes in the external or internal environment
sensation
what is the difference between sensation and perception?
sensation: occurs when sensory receptors detect sensory stimuli
perception: involves organization, interpretation, & conscious experience of those sensations
each piece of incoming information is combined with other arriving & previously stored information in a process called…
integration
occurs in: spinal cord, brain stem, cerebellum, basal nuclei, cerebral cortex
the conscious interpretation of sensation & primarily a function of the CEREBRAL CORTEX
perception
is blood pressure consciously percieved?
NO
does not reach cerebral cortex
unique type of sensation is called a _____
a given sensory neuron carries information for only _____ modality
modality
one
4 types of somatic senses
- tactile
- thermal
- pain
- proprioceptive
information about conditions within internal organs
ex: pressure, stretch, chemicals, nausea, hunger, & temperature
visceral senses
special senses: modalities
smell, taste, vision, hearing, equilibrium or balance
sensory receptor is a structure of the nervous system that _____ in the external or internal environment
monitors changes
process of sensation begins in a _____, which can be a specialized cell or dendrites of a sensory neuron
this characteristic of sensory receptors is known as _____
sensory receptor
selectivity
types of sensory receptor - classification
- microscopic structure
- location of receptors & origin of stimuli that activate them
- type of stimulus detected
microscopic structure - classification
- free nerve endings
- encapsulated nerve endings
- separate cells
bare dendrites associated with pain, thermal, tickle, itch and some touch sensations
free nerve endings
dendrites enclosed in CT capsule for pressure, vibration, and some touch sensations
encapsulated nerve endings
special senses of vision, taste, hearing and equilibrium are served by separate sensory cells - receptor cells synapse with first order sensory neurons
separate cells
location & origin of activating stimuli - classification
- exteroceptors
- interoreceptors
- proprioceptors
located at or near body surface, sensitive to stimuli originating outside body & provide information about external environment
convey visual, smell, taste, touch, pressure, vibration, thermal & pain sensations
exteroceptors
located in blood vessels, visceral organs & nervous system
provide information about internal environment
impulses usually not consciously perceived but may be felt as pain or pressure
interoceptors
located in mm, tendons, joints & inner ear
provide information about body position, mm length & tension, position & motion of joints, equilibrium (balance)
proprioceptors
detect mechanical stimuli; provide sensations of touch, pressure, vibration, proprioception, hearing & equilibrium; monitor stretching of blood vessels & internal organs
mechanoreceptors
detect changes in temperature
thermoreceptors
respond to painful stimuli resulting from physical or chemical damage to tissue
nociceptors
detect light that strikes retina of eye
photoreceptors
detect chemicals in mouth (taste), nose (smell), and body fluids
chemoreceptors
sense osmotic pressure of body fluids
osmoreceptors
characteristic of most sensory receptors is _____, in which generator potential or receptor potential decreases in amplitude during a maintained, constant stimulus
adaptation
*causes frequency of nerve impulses in first order neuron to decrease
areas with the highest density of somatic sensory receptors
tip of tongue, lips, & fingertips
touch, pressure, vibration, itch, & tickle
tactile sensations
touch, pressure & vibration are detected by…
encapsulated mechanoreceptors attached to large‐diameter myelinated A fibers
itch & tickle are detected by…
free nerve endings attached to small‐diameter, unmyelinated C fibers
which reaches the brain first – touch or itch?
touch (large myelinated A-fibers) reaches the brain faster than itch (unmyelinated c-fibers)
rapidly adapting touch receptors
- Meissner corpuscles (corpuscles of touch)
- hair root plexuses
slowly adapting touch receptors
- Ruffini Corpuscles (type II cutaneous mechanoreceptors)
- Merkel Discs (tactile discs/ type I cutaneous mechanoreceptors)
pressure receptors
- Pacinian Corpuscles (lamellated)
- Meissner’s Corpuscles
- Merkel Disks
vibration receptors
- Pacinian Corpuscles (high frequency)
- Meissner’s Corpuscles (low frequency)
itch receptors
- Puriceptors
- Nociocepors
tickle receptors
free nerve endings
thermoreceptors - free nerve endings
cold & warm receptors
-located in stratum basale of epidermis
-medium diameter, myelinated A fibers
-activated by temperatures between 10° & 40°C
cold receptors
-not as abundant as cold receptors
-located in dermis
-attached to small diameter, unmyelinated C fibers
-activated by temperatures between 32° & 48°C (90–118°F)
warm receptors
temperatures below 10°C & above 48°C primarily stimulate _____ receptors, nociceptors rather than thermoreceptors, producing painful sensations
pain
-nerve impulses propagate along medium diameter, myelinated type A fibers
-acute, sharp or pricking pain
-not felt in deeper tissues of body
fast pain
-gradually increases in intensity over a period of several seconds or minutes
-impulses conduct along small diameter, unmyelinated C fibers
-chronic, burning, aching or throbbing pain
-can occur both in skin & in deeper tissues or internal organs
slow pain
pain receptors: nociceptors - free nerve endings found in every tissue of the body except the…
brain
somatic sensations that arise from stimulating the skin are called ____ sensations
cutaneous
pain localization - somatic fast & slow pain
somatic fast pain: precisely localized to stimulated area
somatic slow pain: well localized but more diffuse (involves large areas), appears to come from larger area of skin
pain localization - visceral pain
= referred pain
*visceral organ involved & area to which pain is referred are served by same segment of the spinal cord
3 types of proprioceptors
- muscle spindles within skeletal muscles
- golgi tendon organs within tendons
- joint kinesthetic receptors within synovial joint capsules
-monitor changes in length of skeletal mm & participate in stretch reflexes
-contributes to mm tone
muscle spindles
-located at musculotendinous junction
-protect tendons by initiating tendon reflexes & their associated mm from damage due to excessive tension
golgi tendon organs
-within & around articular capsules of synovial joints
-free nerve endings & Ruffini corpuscles (pressure)
-small Pacinian corpuscles (acceleration & deceleration)
-joint ligaments (reflex)
joint kinesthetic receptors
for a sensation to arise, what 4 events occur?
- Stimulation of a sensory receptor
- Transduction of stimulus
- Generation of nerve impulses
- Integration of sensory input
sensory receptors produce what 2 different kinds of graded potentials in response to a stimuli
- generator potentials
- receptor potentials
a generator potential turns into an …
action potential
receptor potentials - neurotransmitter molecules liberated from synaptic vesicles diffuse across the synaptic cleft & produce a _____ in the first order neuron
postsynaptic potential (PSP)
large generator potentials or receptor potentials trigger nerve impulses at _____ in the first order neuron, in contrast to small generator potentials or receptor potentials, which trigger nerve impulses at _____
high frequency
lower frequencies
conditions which must be present for regeneration of neurons
- neurons must be located in PNS
- intact cell body
- myelination by functional Schwann cells having a neurolemma
birth of a new neuron from a stem cell
neurogenesis
-mild nerve injury
-temporary conduction block without axonal damage
-endoneurium, perineurium, epineurium intact
-no Wallerian degeneration
-sensory/motor problems distal to injury
-conduction blocked at injury site but remains intact in proximal & distal segments
-full recovery = days to weeks
neuropraxia
-2nd most severe nerve injury
-loss of axon continuity & myelin, but CT (epineurium, perineurium) intact
-sensory & motor deficits occur distal to injury, with no conduction for 3-4 days
-Wallerian degeneration distal to injury
-axonal regeneration allows for potential recovery without surgery
axonotmesis
-most severe nerve injury
-complete/ partial severance of nerve, causing sensory, motor, & autonomic deficits
-no conduction or Wallerian degeneration distal to injury
-surgical intervention required for repair
neurotmesis
