(07) Nociception Flashcards
What is an unpleasant sensory and emotional experience associated with actual or potential tissue damage?
pain
What is a primary afferent neuron that is preferentially sensitive to a noxious stimulus?
- nociceptor
What is the detection of tissue damage by specialized transducers (nociceptors) attached to “A delta” and “C” peripheral nerve fibers?
Does is refer to production of emotional or other types of response to the noxious stimulus?
- nociception
- no
What does Algesic mean?
Analgesic?
- pain producing
- pain preventing
What is increased pain sensation elicited by a noxious stimulus (bump an injured toe)?
- hyperalgesia
What is a pathological condition in which pain is produced by a stimulus that is normally innocuous (sunburn)?
- Allodynia
Look at this for a spell
Tissue damage, injury or inflammation causes the tissue area to be more sensitive to what?
What does this lead to?
So can just touching the area around an incision be painful?
- both innocuous and noxious stimuli
- increased pain sensation
- yes
What are the four ways you can recognize pain in animals?
- situational evidence (recent injury)
- behavioral responses
- physiological changes (altered autonomic function)
- Biochemical changes (cortisol or adrenaline in blood)
(1) nociceptor
(2) first-order neuron (spinal ganglion)
(3) Second order neuron (spinal cord)
(4) Third-order neuron (thalamus)
Pain or nociception is initiated when what occurs?
What three things activate sensory neurons?
What is the broad term for this?
(nociceptors) Pain receptors = ?
- when the peripheral terminals (receptors) of a subgroup of sensory neurons (nociceptors) are activated
- noxious chemical, mechanical, or thermal stimuli
- Peripheral transmission
- free nerve endings
Damage to tissue causes the release of what?
What are some examples of these?
What do these do?
What (3 things) is sensitization seen as?
- large number of mediators that activate nociceptor nerve endings.
- ATP (from damaged cells), bradykinin (from blood), PGE2, NGF
- increase sensitivy, make nociceptors much more sensitive
- A reduction in the threshold for activation
- An increase in response to a given stimulus, and/or
- The appearance of spontaneous activity.
What does the TRPV1receptor measure?
- heat
What is the progression to hyperalgesia - starting with inflammatory mediators?
Inflammatory mediators–>
Receptors on nociceptors –>
Second messenger systems–>
Sensitization–> Hyperalgesia
How does the release of mediators increase sensitivity?
What do activated pain terminals do once they have been activated?
- activate pain terminals by increasing conductance of sodium (gNA) or calcium (gCa) channels
- or by activating second messenger systems(adenylate cyclase, AC)
- conduct electrical signal to spinal cord
What effect does tissue damage or repetition of a noxious stimulus have on nociceptors?
What does this reduce?
What does this lead to?
This is the mechanism that underlies what?
- sensitizes them
- their threshold for activation
- increase in response to stimulus or development of spontaneous activity
- hyperalgesia
Where do peripheral nociceptors have their cell body (or soma)?
What does the cell body give rise to (2 things + what they do)?
- in a spinal or a cranial nerve ganglia
1. peripheral process (or primary afferent axon) - innervates skin, muscle, viscera, etc as a free nerve ending
2. central process - terminates in spinal cord dorsal horn or in brain stem
Two types of axons that transmit noxious information from nociceptive receptors
- A-delta fibers
- C-fibers
A-delta fibers vs. C-fibers
myelination
conduction speed
1st or second pain
lightly myelinated – non-myelinated
2-30 M/sec – less than 2 M/sec
1st pain – 2nd pain
(Primary Response Characteristics)
- what will things that are progressively more painful lead to?
- Does receptor stop firing right when painful stimulus is over?
- The more action potentials there are…
- more action potential (from pain receptors) being fired
- no it keeps going for a spell
- the more it hurts
Give me the order of central transmission
Primary afferent axons -> the spinal cord dorsal horn (marginal nucleus or nucleus proprius) -> thalamus -> cerebral cortex
Pain sensation is conveyed from the spinal cord by several central nervous system pathways - what are the two most important in animals?
- Spinothalamic pathway
- Spinocervicothalamic pathway
What pathway is considered to be the major pain relay system in mammals?
- spinothalamic pathway
(SPINOTHALAMIC PATHWAY)
(1st order neuron)
cell body location?
peripheral process associated with?
central process enters what to synapse in what?
(2nd order neuron)
cell body location?
axons cross midline (decussate) and join what?
What do these axons form?
axons travel through what to terminate in what?
What do they synapse on?
(third order neurons)
Axons terminating in lateral thalamus mediate?
in the medial thalamus?
3rd order neurons in thalamus send their axons where?
(1st order neuron)
- spinal (dorsal root) ganglion
- receptor
- enters gray matter of the cod to synapse in the marginal nucleus (lamina I), substantia gelatinosa (lamina II), and deeper laminae.
(2nd order neuron)
- in marginal nucleus and nucleus propius
- other axons that also carry pain sensation
- Spinothalamic tract (in ventral part of lateral funiculus)
- through brain stem to terminate in thalamus
- synapse on 3rd order neurons in thalamus
(third order neurons)
- discriminative aspects of pain
- motivational-affective aspects of pain (relationship between emotion and pain)
- the cerebral cortex
