Neuropathic Pain Flashcards
What is the definition of pain?
an unpleasant sensory and emotional experience associated with actual or potential damage, or described in terms of such damage
what are the two main types of pain?
nociceptive
neuropathic
what is nociceptive pain?
acute pain associated with injury and inflammation
what causes nociceptive pain?
nociceptor is stimulated by noxious or potentially damaging stimuli through mechanical, thermal, or chemical means associated with inflammation
give an example of mechanical, thermal, and chemical pain
mech - break fingers
therm - hand on hot stove
chem - HCl on skin
what is neuropathic pain?
chronic sensory abnormalities; pain initiated by a lesion or dysfunction of the somatosensory system, resulting in abnormal activity of the nociceptive pathway
what are 3 potential causes of neuropathic pain?
drugs
disease
trauma
what are the pain and temp nerve fibers? what do they look like? which one is better at conducting pain transmission?
Adelta - small, myelinated (better)
C - small, unmyelinated
what is the touch nerve fiber? what does it look like?
Abeta - large, myelinated
out of the mentioned nerve fibers, which is the last to develop in neuropathic pain?
Abeta fibers
What are the steps of the pain pathway?
1) pain source goes to peripheral nerve
2) afferent fiber travels to dorsal horn (goes to DRG)
3) travels up spine to brain (thalamus, sensory cortex, limbic system)
4) motor response travels down spine
5) efferent fiber travels from spinal cord (ventral horn) to body part to move it away from pain source
What is the membrane potential at rest?
-70mV
What ions are involved with the membrane potential?
Na, K, Cl, Ca
Why is the membrane potential closer to Ek rather than Ena?
membrane is more permeable to K (Ek = -90mV)
how does the Na/K pump re-establish membrane potential?
pump out 3Na for every 2K pumped in
What is the first step in initiating an AP?
a stimulus causing depolarization and Na channels to open, allowing Na to rush into the cell
what is the 2nd step in initiating an AP?
internal membrane potential becomes more positive
what is the 3rd step in initiating an AP?
if the cell depolarizes to threshold, an AP will result (all or nothing)
what is the 4th step in initiating an AP?
Na channels start to close as K channels start to open
what is the 5th step in initiating an AP?
Em returns to resting potential and a refractory period occurs where Na channels cannot open
What do excitatory NTs do? give an example of an excitatory NT
bind to post synaptic receptors and cause depolarization
ex: Glu, substance P
what do inhibitory neurons do? give an example of an inhibitory neuron
bind to post-synaptic receptors and cause hyperpolarization
ex: GABA, glycine
What causes hyperexcitability?
enhancement of excitatory mechanisms or loss/reduction of inhibitory mechanisms
what happens when cell permeability is increased?
Na and Ca concentrations increase intracellularly, leading to depolarization and firing of neurons
