General Senses and Pain (2) Flashcards
Exam 2
Sensory Receptors definition
any structure specialized to detect a stimulus
What are the two types of sensory receptors?
- Simple: bare nerve endings
- Complex: sense organ-structure composed of nervous tissue and other tissue types (enhance responses to specific stimuli)
What is the purpose of sensory receptors?
transduction
Transduction definition
conversion of one form of energy to another
conversion of stimulus energy into nerve signals
Receptor Potential definition
small local electrical change on a receptor cell (neuron/ epithelial cell) brought about by a stimulus
strong stimuli = ___ ___
action potential
release neurotransmitter = generates nerve signal to CNS
Sensation definition
awareness of a stimulus
majority is filtered
What are the four kinds of information that transmit through receptors?
- Modality (type)
- Location
- Intensity
- Duration
What is Modality (type)?
hearing, taste, vision
determined by where sensory signals end in brain
What is Location?
which nerve fibers are sending signals
receptive field- area within which a sensory neuron detects stimuli
What is Intensity?
encoded in three ways:
- how fast are neurons firing
- number of neurons firing
- which neurons are firing
What is Duration?
how long stimulus lasts
changes in firing frequency over time
Phasic Receptors definition
adapt rapidly: generate bursts of action potentials when first stimulated
Tonic Receptors definition
adapt slowly: generate nerve signals more steadily throughout presence of stimulus
What are the 5 classifications of receptors by modality?
- Mechanoreceptors
- Thermoreceptors
- Pain Receptors
- Chemoreceptors
- Photoreceptors
What are Mechanoreceptors?
stimulated by changes in pressure or body movement
prioreceptors- specialized stretch receptors in muscle
What are Thermoreceptors?
stimulated by changed in the external or internal temperature
(primarily in the skin)
What are Pain Receptors?
stimulated by damage or oxygen deprivation to the tissues
skin- respond to chemicals released by injured tissue
What are Chemoreceptors?
Stimulated by changes in the chemical concentrations of substances
tastes buds/ olfactory receptors)
What are Photoreceptors?
stimulated by light energy
only in eye
What are the two ways receptors are classified?
- Origin of stimuli
2. Distribution
What are Exteroceptors?
detect external stimuli
vision, hearing, taste, touch, smell, temperature, pain
What are Interoceptors?
detect internal stimuli
hunger, stretch receptors, pressure receptors, visceral pain, nausea
What are Proprioceptors?
sense body position/movement
muscles tendons, joints
General (somatosensory) senses are ___ distributed
widely
Special sense are limited to ___
head
vision, hearing, taste, smell, equilibrium
What are the special senses?
- vision
- hearing
- taste
- smell
- equilibrium
Free nerve ending are for ___ and ____
pain (nociceptors)
temperature (warm/ cold receptors)
Bare dendrites have no ___ ____
special associates
Skin and mucous membrane branch between ___
cells
Somatosensory Projection Pathways definition
transmission of info from receptors to final destination in brain
Most somatosensory signals travel by way of three neuron. What are they?
- First order neurons
- Second order neurons
- Third order neurons
Pain definition
Discomfort caused by tissue injury or noxious stimulation
results in evasive action
Nociceptors definition
specialized nerve fibers
What are the two types of nociceptors?
- First (fast) Pain: myelinated fibers at 12 to 30 m/s (sharp, sudden, instantaneous- localized stabbing pain)
- Slow (second) Pain: unmyelinated fibers at 0.5 to 2 m/s (long lasting, dull, continuous)
What is nociceptive pain?
- superficial somatic pain (skin)
- deep somatic pain (bones, muscles, joints)
- visceral pain (organs)
Neuropathic Pain definition
nerves, spinal cord, meninges or brain
–stabbing, burning, or tingling
Injured tissues release chemicals that ____ pain fibers
stimulate
What are the three ascending tracts of the projection pathways for pain
- spinothalamic tract
- spinoreticular tract
- gracile fasciculus
What is the spinothalamic tract?
most significant pain pathway
(Carries most somatic pain signals)
(cerebral cortex)
What is the spin-reticular tract?
activated visceral, emotional, and behavioral reactions to pain
(limbic system, hypothalamus)
What is the gracile fasciculus?
carries signals for visceral pain
(stomach ache, kidney stones)
(thalamus)
Referred Pain definition
pain in viscera often mistakenly thought to come from the skin or other superficial site
What are endogenous opioids?
“internally produced opium-like substances”
Enkephalins definition
two analgesic oligopeptides with 200x potency of morphine
Endorphins definition
larger analgesic neuropeptides
Spinal Gating definition
stops pain signals in spinal cord (posterior horn)
Facts of descending analgesic fibers
- arise in brainstem
- descend in a spinal cord (reticulospinal tract)
- block pain signals from traveling up spinal cord
