Nociception Flashcards
A primary afferent neuron that is preferentially sensitive to noxious stimulus
Nociceptor
Pain producing
Algesic
Pain Preventing
Analgesic
Increased pain sensation elicited by a noxious stimulus (bump an injured toe)
Hyperalgesia
A pathological condition in which pain is produced by a stimulus that is normally innocuous (sunburn)
Allodynia
4 ways to detect pain in animals
- Situational evidence - recent injury?
- Behavioral responses (aggressiveness?)
- Physiological changes (increased HR?)
- Biochemical changes (coritsol or adrenaline in blood?)
All somatosensory pathways begin at a ……… that converts environmental energy into an electrical signal
Peripheral receptor
Location of a first order neuron in the Spinothalamic pathway
Spinal Ganglion
Location of a second order neuron in the Spinothalamic pathway
Spinal Cord
Location of a third order neuron in the Spinothalamic pathway
Thalamus —> to the cortex
Pain receptors (nociceptors) have:
Free Nerve Endings
TRPV1 is sensitive to:
Thermal Stimuli
&
changes in pH
2 examples of inflammatory mediators that act upon nociceptors
ATP & Bradykinin
Once inflamm mediators attach on nociceptors, 2nd messenger systems ……
increase sensitization and increase hyperalgesia
Sensitization of nociceptors is seen as (3):
This mechanism underlies ……
- A reduction in the threshold for activation
- An increase in response to a given stimulus
- The appearance of spontaneous activity
HYPERALGESIA
Peripheral nociceptors have their cell body or soma in a ______ or a ______
Spinal or a cranial nerve ganglia
The peripheral receptor cell body gives rise to (2 things):
- A peripheral process or primary afferent axon that innervates skin, muscles, viscera, etc. as a free nerve ending
- a Central Process that terminates in the spinal cord distal horn or in the brain stem
Two types of axons transmit noxious information:
A delta fibers
C fibers
Lightly myelinated, conduct at velocities of 2-30 M/sec (1st pain)
FAST!
A delta fibers
Non-myelinated, conduct at velocities of less than 2 M/sec (2nd pain)
SLOW!
C-Fibers
Central transmission of Pain
Pain is transmitted from: Primary Afferent Axons (from cell bodies in spinal ganglion) -----> Spinal cord dorsal horn (Marginal nucleus or nucleus proprius) -----> Thalamus -----> Cerebral Cortex
2 most important central nervous system pathways for pain:
- Spinothalamic Pathway
2. Spinocervicothalamic Pathway
This pathway is classically considered to be the major pain relay system in mammals.
Spinothalamic Pathway
1st order neuron
Location
Peripheral Process Projection Site
Central Process Projection Site
Dorsal Root Spinal Ganglion
The nociceptor
Gray matter of the cord
1st order neuron synapses on (3)
Marginal Nucleus
Substantia Gelatinosa
Deeper laminae
2nd order Neuron
Location
Axon path
Axon termination location
Marginal Nucleus & the Nucleus Proprius
Decussate and join other axons that send pain information. These form the Spinothalamic Tract.
Terminate in the thalamus
3rd order Neuron
Location
Send Axons to?
Thalamus
Send axons to the cerebral cortex
2nd order neuron axons that terminate in the MEDIAL THALAMUS mediate the ___________
Motivational-Affective aspects of pain (emotion & pain)
2nd order neuron axons that terminate in the LATERAL THALAMUS mediate ______________
discriminative aspects of pain
An animal becomes aware of painful stimuli at the level of the _______
Thalamus
The _______ is required for localization of pain to a specific body region
Cerebral cortex
The Spinocervicothalamic (Spinocervical Pathway) differs from the spinothalamic pathway in that is has an additional neuron located in the : \_\_\_\_\_\_\_\_\_\_
and the pathway crosses at the ___________
Lateral cervical nucleus
Level of the rostral spinal cord/lower brainstem
Spinocervicothalamic pathway:
Receptors: ______
1st Order Neurons: _______
2nd Order Neurons: ______
3rd Order Neurons located in: ______
Free Nerve Endings
Dorsal Root Ganglion
Marginal Nucleus or Nucleus Proprius
Lateral Cervical Nucleus
Axons from 3rd order neurons in the cervicospinal pathway cross the midline and ascend to the contralateral _______ where they terminate on ______
Thalamus
4th Order Neurons
Cervicospinal pathway
The axons of 4th Order Neurons project to _______ of the _______
Somatosensory Area
Cerebral Cortex
Major components of the endogneous Analgesia system: (3)
Midbrain Periaqueductal Gray (PAG)
Nucleus Raphe Magnus
Nucleus Locus Coeruleus
Nucleus Raphe Magnus Location
Midline of the rostral medulla
Nucleus Locus Coeruleus Location
Caudal pons near the floor of the 4th ventricle
Nucleus Raphe Magnus neurons contain high levels of _________
Axons synapse in the ______ and _______ to inhibit pain transmission neurons in these nuclei of the dorsal horn
Serotonin
Marginal Nucleus & Nucleus Proprius
Nucleus Locus Coeruleus contains high levels of ________
Norepinephrine
Midbrain Periaqueductal Grey region contains a high density of _______ which activates a ______ pathway that excites neurons in the ______ and consequently inhibits spinothalamic and spinocervicothalamic neurons in the spinal cord.
Opiate receptors
Descending
Nucleus Raphe Magnus
Endonenough Pain Activation System helps to maintain ____ ____.
Chronic Pain
4 vital signs to take
Temperature
Pulse
Respiratory Rate
Pain score
Treat mild pain with: (4)
NSAID’s
Steroids
Local anesthestics
Physical Therapy
Treat moderate pain with: (3)
Opioid agonists
Opioid agonists/antagonists
Alpha2 agonists
Treat severe pain with: (2)
Potent opioids with/without concurrent medications
Permanent nerve blocks
Local anesthetics (3)
Carbocaine
Lidocaine
Bupivicaine
Corticosteroid type
Prednisone
NSAID’s (4)
Aspirin
Rimadyl
Deraxocib oral
Tepoxalin oral
Alpha 2 Agonists (3)
Xylazine
Demotidine
Medetomidine
Opioids (1)
Buprenex Injectable (buprenorphine)
Acupuncture aids in the release of: (3)
Norepinephrine
Opioid substances
Other neurotransmitters
