Sensory Perception and Transmission in Nervous System Flashcards
visceral
in internal organs of body
somatic
pertaining to the body
importance of sensory input on psyche
vital to integrity of personality and intellectual function
sensory receptor
a structure specialized to detect a stimulus; participates in transduction
sense organ
nerve tissue surrounded by other tissues that enhance response to a certain type of stimulus – may include accessory tissue (epithelial, muscular, connective)
transduction
transforming one type of signal into another; conversion of one kind of energy to another
receptor potential
small local electrical change on a receptor cell brought about by a stimulus; makes action potential occur when receptor potential rises above threshold
Sensory receptors transmit four kinds of information
modality (type of sensation), location, intensity, duration
Sensation
a subjective awareness of the stimulus
Types of Sensory Receptors
- Mechanoreceptors
- Thermoreceptors
- Nociceptors
- Electromagnetic
- Chemoreceptors
Mechanoreceptors
detect deformation
Thermoreceptors
detect change in temperature
Nociceptors
detect damage (pain receptors)
Electromagnetic
detect light
Chemoreceptors
taste, smell, CO2, O2 etc.
free nerve ending
pain and temp., not encapsulated, located in skin and mucous membrane
expanded tup receptor
sense light touch and texture, in epidermis, tactile discs
tactile hair
can detect movement of hair, epidermis and dermis, mechanoreceptor
Pacinian corpuscle
deep pressure, stretch, tickle, vibration; deep tissue sensibility
Meissner’s Corpuscle
light touch and texture; hairless skin, epidermis and dermis
Krause’s Corpuscle
tactile, mucous membrane; epidermis and dermis
Ruffini’s End-Organ
heavy touch, pressure, joint movements, skin stretching; deeper tissue
Golgi Tendon Apparatus
tendon stretch, deep tissue, located at muscle endings
Muscle Spindle
responsible for sensing muscle movement; located at muscle endings; deep tissue
Generation of receptor potential by mechanical distortion
- Mechanical distortion increases Na+ conductance.
- receptor potential
- action potential
adaptation
receptor decreases frequency of impulse in response to sustained stimulation
tonic receptors
slow adaptation (hours, days)
tonic receptor examples
muscle spindle, Golgi tendon apparatus, Ruffini endings, Merkel discs, Macula, pain, temperature, baroreceptors, chemoreceptors, muscle contraction
phasic receptors
rapid adaptation; responds only to the change
examples of phasic receptors
pacinian corpuscle, meissner’s corpuscle, semicircular canals
gradation in signal intensity can be achieved by:
- spatial summation
2. temporal summation
spatial summation
increasing number of fibers stimulated in a particular area
temporal summation
increasing rate of firing in given fibers
nociception
pain
when does nociception occur?
when tissue is being damaged
Types of Pain (Nociception)
- Fast Pain
2. Slow Pain
Fast Pain
body surface
felt within 0.1 s after stimulus
sharp pain: (knife cut, needle poke, burn).
Not felt in most deeper tissues
Slow Pain
body surface or deeper tissue
felt after 1 s or more
throbbing or aching pain
Usually associated with tissue destruction (bradykinin).
main cause of pain from tissue damage
bradykinin
dual pain pathways
- fast pain (1st pain) transmitted by type A delta fibers (6-30 m/s) in neospinothalamic tract
- slow pain (2nd response) transmitted by type c fibers (0.5 - 20 m/s) in the paleospinothalamic tract
Neospinothalamic Tract
- On entering cord, pain fibers may travel up or down 1-3 segments and terminate on neurons in dorsal horn.
- 2nd neuron crosses immediately to the opposite side and passes to the brain in the anterolateral columns.
- 3rd order neurons go to the cortex.
excitatory transmitter of A-delta pain fiber nerve ending.
Glutamate
Neospinothalamic Tract: Some neurons terminate in the _____ but most go all the way to the ______
reticular substance; ventrobasal complex of the thalamus.
Paleospinothalamic tract
- Type C pain fibers terminate in laminae II & III of spinal cord.
- 2nd neuron crosses immediately to the opposite side and passes to the brain in the anterolateral columns.
excitatory transmitter of type C pain fiber nerve ending.
Substance P
Endogenous opioids
internally produced opium-like substances; Act as neuromodulators that block pain and give pleasure
Enkephalins
two analgesic oligopeptides with 200 times the potency of morphine
Endorphins and dynorphins
larger analgesic neuropeptides discovered later
endogenous analgesic secreted by:
CNS, pituitary gland, digestive tract, and other organs
______ is used to counter the effects of opiate overdose (heroin, morphine, etc)
Naloxone
