Neuropain and histology and Degeneration and Recovery of Function FINISH- E2 Flashcards
What are the steps of an AP release at a synapse
- AP arrives @ presynaptic terminal
- Mem depol, opens VGCa++C
- Influx Ca++ causes mvmt synaptic vesicles containing NT toward release site
- Synaptic vesicles fuse w/mem and release NT
- NT diffuses across cleft
- NT binds to postsynaptic receptors
List the 3 types of synapses
Axodendritic
Axosomatic
Axoasonic
What is an axodendritic synapse
b/t axon pre and dendrite of post synaptic
What is an axosomatic synapse
b/t axon pre and cell body post synaptic
What is an axoaxonic synapse
b/t axon pre and axon post synaptic
Which synapses generate a local postsynaptic potential?
Neuromuscular
Axosomatic
Axodendritic
Which synapses modulate the membrane potential of a postsynaptic cell
Axoaxonic
How do axoaxonic neurons regulate NT release?
They change the amount of Ca++ influx to the presynaptic neurons
What are the steps of presynaptic inhibition
- IN release NT
- NT bind to presynaptic neuron, reduce Ca++ influx
- Presynaptic neuron releases less NT when an AP arrives at its terminal
What are the steps of presynaptic facilitation
- IN releases NT
- NT bind to presynaptic neuron, increase Ca++ influx
- Presynaptic neuron releases more NT when an AP potential arrives
Define nociception
the neural process of encoding noxious stimuli
What are nociceptors?
“free” peripheral nerve endings consisting of a series of spindle-shaped, thick segments linked by thin segments, creating a “string-of-beads” appearance
Where can you find nociceptors?
- skin
- muscles
- joints
- viscera
- mouth, dental
- almost all types of tissues
How do you activate a nociceptor
- Intense thermal, mechanical, or chemical stimuli from exogenous or endogenous sources
T or F: Nociceptors are unimodal
False - polymodal
What nerve cells are part of the double pain sensation
A delta neurons and C fiber neurons
What kind of pain with…
a) A delta
B) C fiber
A) Initial, sharp, localized pain
B) Diffuse, prolonged, aching, dull pain
What % of pain-transmitting fibers are….
a) A delta
b) C fiber
a) 80
b) 20
What kind of neurons are A delta and C fibers?
Unipolar neurons w/cell bodies in DRG
Which has a faster nerve conduction velocity? (A delta or C fibers)
A delta (30m/s) not C fibers (1-4 m/s)
Which fiber type (nerve) has associated autonomic responses
C fibers
Which lamina of the SC do you find A delta and C fibers
Lamina I, II and V
What do C and A delta neurons synapse on?
Transmission cells (T cells) in the substantia gelatinosa of the SC
How does the gate control mechanism of pain work
A-beta fibers synapse on the inhibitory interneuron to block out the synapse of the a-delta and c fibers
What is the severity of pain sensation determined by
The balance of excitatory and inhibitory inputs to the T cells
What do the T cells synapse on
Efferent alpha motor neurons to cause mm contractions
What is responsible for the “pain-spasm-pain” cycle?
The C & A delta neurons synapsing on T cells that in turn synapse on efferent alpha motor neurons
What else do C & A delta neurons synapse on?
2nd order neurons
- Autonomic neurons
- Ascending sensory spinal cord tracts (to thal to sensory cortex)
Where does the lateral spinothalamic tract go to?
What does it transmit?
Medial thalamus
Sharp, localized pain
Where does the antero- spinothalamic tract go to?
What does it transmit?
Reticular formation, hypothalamus, and limbic system, all of which synapse on the lateral, ventral, and caudal thalamus
Prolonged, aching pain
What does the thalamus do
Processes and relays pain afferent sensations to various brain structures
Pain interpretation in:
Sensory cortex
Conscious pain perception including location and quality of pain
Pain interpretation in:
Anterior and posterior cingulate gyri
Pain interpretation plus focus attn towards the cause of the pain and evaluates its significance
Pain interpretation in:
Temporal lobes
May start processes of storing memories associated w/pain
Pain interpretation in:
Hypothalamus
Autonomic responses to pain
Where is a NT synthesized
In the neuron cell body and then is transported to the presynaptic terminal
How are NT removed from the synaptic cleft?
Synaptic vesicle recycling
T or F: NT only excite the postsynaptic neuron
False! They excite or inhibit depending on the molecule released and the receptors present on the postsynaptic membrane
Which are fast- acting and why?
A) NT that act directly
B) NT that act indirectly
A) NT that act directly bc their effects are extremely short lived
Which are slow-acting and why?
A) NT that act directly
B) NT that act indirectly
B) NT that act indirectly bc their transmission requires 100ms to minutes
How do ligand gated channels and NT work together?
Like a lock and key w/NT as the key
How do indirect NT activate the ion channels?
By binding to a separate G-protein that will then activate the ion channel
What are the steps for signal transmission at the G-protein
- Non-stim state, G prot complex assoc w/mem receptor
- NT binds to mem receptor, causing a conform change and activation of G protein
- GTP binds to G prot and conform change in the protein channel causes the channel to open, and ions (Na+) flow in
- GDP released and channel closes
T or F: The G-protein can cause persistent opening of membrane channels
True!
What is a neuromodulator
It acts at a distance from the synapse and modulates the activity of many neurons at the same time, lasting minutes or days
What is an example of a NT and Neuromodulator duo?
NT: Glutamate
NM: Substance P
List 2 types of AA
Glutamate
GABA
What are the most prevalent fast-acting neurotransmitters? What category are they?
GABA and Glutamate which are Amino Acids
Glutamate:
a) Slow or fast
b) Excitatory or Inhibitory
c) What is it involved in
d) What does overactivity cause
a) Fast
b) Excitatory
c) Learning and memory
d) Seizures and too much may cause neuronal damage
GABA
a) Slow or fast
b) Excitatory or Inhibitory
c) What is it involved in
a) Fast
b) Inhibitory
c) Preventing excessive neuronal activity
What do bartiburates mimic?
What are they used for?
GABA
Sedation and anticonvulsants
What does Baclofen do?
It is a mm relaxant
It increases the presynaptic release of GABA
What is ACh
a) Slow or fast
b) Excitatory or Inhibitory
A cholinergic NT
a) Slow and Fast
b) Fast-acting is Excitatory and Slow-acting is inhibitory
What are nicotinic and muscarinic receptors associated with?
ACh
Nicotinic Receptor A) what does it bind b) What is it linked to c) What type of response d) Located where? e) Mediates (excitation/inhibition?)
A) Nicotine
b) Ion channels
c) Fast and brief
d) Neuromuscular junction, autonimic ganglia, some CNS
e) Exciation
Muscarinic Receptor A) what does it bind b) What is it linked to c) What type of response d) Located where? e) Mediates (excitation/inhibition?)
a) Muscarine
b) 2nd messenger G protein
c) Slow and prolonged response
d) Myocardial mm, smooth mm, and some CNS
e) Both inhibition and excitation
T or F: ACh is a NT and a NM
True - as a neuromodulator it regulates locomotion and arousal, facilitates attention, memory and learning
Dopamine
a) NT Type
b) Excitatory or Inhibitory
c) What is it involved in
d) Where is it produced
a) Amine
b) Inhibitory in CNS
c) Motor A, motivation/reward, cognition
d) SNc of BG
List the different types of amines
Histamine
Norepinephrine
Serotonin
Dopamine
What is the dopamine projection system
a) BG - Movement
b) Limibic - Reward/wanting & addiction
c) prefrontal - working memory, attn
Which Neuro conditions are from an increase in dopamine
1) Lack of motivation Behaviours
2) Schizophrenia
Which Neuro Conditions are from dec. DA
1) PD (dec. in BG)
2) Depression/cognitive
3) Drug addiction
What are the body’s natural pain killers?
Peptides - the endogenous opioids
Opiopeptins
a) NT Type
b) Excitatory or Inhibitory
c) What is it involved in
d) How can the body increase these concentrations
A) Peptides
B) Inhibitory
c) Pain killing and altering the perception of pain
d) EXERCISE
What is Substance P
A peptide that acts as both a NT and NM
Substance P’s role as a NT
Binds NK-1 receptors in SC that then relay this info up the spinothalamic tract up to Broadman areas 1,2
What nerve cells release Substance P as a NT
Primary afferent C and A delta nerve fibers
What does Substance P co-transmit w/ and what does it do
Glutamate and substance P work together to cause pain signals to be sent to the brain and prolong the depolarization caused by glutamate
What is the dual role in pain management played by Substance P
It increases sensitivity to pain indirectly by its inflammatory effects AND it directly increases the recognition of pain
What is the centralization of pain vs peripheralization
Pain moving towards the center of the spine vs laterally away from the center of the spine/down the extremity