Week 19 Lectures Flashcards
What are the parasympathetic nerves come from?
CN III
CN VI
CN IX
CN X
S2 ,3,4
Where does the visceral motor cell bodies?
CN III
CN VI
CN IX
CN X
T1-L2
S2,3,4
Where does sympathetic innervation come from?
T1-L2
What are the layers in a nerve
epineurium
perineurium
endoneurium
Epineurium
surrounds entire nerve
Perineurium
encapsulates bundles of axons called fascicles
Endoneurium
m contained within the perineurium consists of axons
Axons require _______. _________ with soma for viability
Axons require cytoplasmic continuity with soma for viability
2 types of schwann cells associted with axons
1) myelinating
2) ensheathing
What 2 main variables influence AP propagation rate
1) Fibre diameter – larger diameter = faster AP propagation rate
2) Myelin - greater the thickness and segmental length of myelin = faster APs
Two classification schemes for Peripheral nerve axons
1) Conduction Velocity
A-fastest myelinated
alpha,beta, delta,gamma
B-slower myelinated
- C-smallest unmyelinated
2) Diameter
I,II,III,IV
a,b
- for sensory axons only
Special senses
The special senses are modalities carried by cranial nerves
Olfaction – CN. I
- Vision – CN. II
- Taste – CN. VII and CrN IX
- Hearing and balance (equilibrium) – CN. VIII
The general or somatic senses (Somatosensory)
Detected from all parts of the body (and head) and transmitted to CNS via:
- CN. V (trigeminal)
- All spinal nerves except CN.1
what is different about the Generating potential in the optic compared to all other cell types?
It is a hyperpolarization rather then a depolarztion
Where do the fibres for sensory of the body terminate
the VPL (Ventral posterolateral nucleus)
Where do the sensory fibres of the head-synapse in the thalamus?
VPM
Which sensory pathway is Lissauer tract a part of?
Spinothalamic tract
What do 3rd order neurons for sensory touch and pain travel through when traveling from the thalamus to the postcentral gyrus?
The internal capsule
Where do the motor neurons cross for the anterior corticospinal tract?
What is the percentage of fibres here?
It crosses in the spinal cord
15%
_- Motor neurons innervate ______ fibres which are responsible for muscle ________.
alpha- Motor neurons innervate extrafusal fibres which are responsible for muscle contraction.
How long do we have to reattach nerves if they are cut?
~12 months sooner is better!
What are the clues that a disease is demylinating (5)
1) Weakness without atrophy
2) Rapidly ascending
3) preceding infection
4) Areflexia
5) patchy distribution non-lenght dependent
peripheral neuropathy caused by diabetes is _______ and length _________
peripheral neuropathy caused by diabetes is Axonal and length dependent
Investigations lab tests for peripheral neuropathy (6)
1) CBC
2) A1C/ Blood glucose
3) B12
4) ESR- erythrocyte sedimentation rate_ inflammation
5) TSH
6) Serum protein electrophorisis
Positive motor symptoms for a peripheral neuropathy
Cramps/ twitching
Positive sensory symptoms for peripheral neuropathy? (5)
1) paresthesia- Tingling pins and needles
2) burning
3) stabbing pain
4) Allodynia- discomfort to stimuli that are not typically painful
5) Hyperalgesia- Increased sensitive to pain stimuli
What are the negative motor symptoms for peripheral neuropathy symptoms?
Weakness
Atrophy
What are the negative symptoms for peripheral neuropathy?
1) Reduce sensation/numbness
2) Gair ataxia/imbalance
What are some of the Autonamic symptoms of peripheral neuropathy? (4)
1) Cardiac
2) GI
3) Genitourinary
4) Vasomotor
- cold extremities
- skin color changes
Fill in this table:
Whar are the three categories of peripheral neuropathy and the types of neuropathy under those categories?
1) Focal
- Mononeuropathy: a single nerve
- Radiculopathy: A single nerve root
2) Multifocal
PolyRadiculopathy
Mononeuropathy multiplex
3) diffuse
Polyneuropahty
Explain Lenght dependent polyneuropathy pathology
metabolic function is in the neuron cell body and then nutrients are transported down axon if there is a defect in this the distal axons die first
what are some causes of distal axonapathy? (4)
1) diabetes
2) nutrient defiency
3) Toxins ETOH/ chemo
4) hereditary neuropathy
What are the red flag signs that something is not a Distal axonopathy (5)
1) Asymmetry of onset and findings
2) Cranial nerve involvment
3) Motor> sensory
4) disproportionate reflex changes (Areflexia with mild symptoms)
5) Rapid progression with significant deficit over acute
What is a Radiulopathy what is a example of this?
It involves a single nerve root. example is Sciatica
What is mononeuropathy? what is an example of this?
Lesion of a single nerve, Carpal tunnel, medial nerve
What is the order that we give drugs for neuropathic pain
1) Gabapentinoids/TCAs/SNRIs
2) Tramadol/Opiod ????
3) Cannabinoids
4) 4th line agents
What is a marker in CFS that is indicative of GBS?
Albuminocytologic dissociation
What is the gene that causes an CMT1A? Is those a demylinateing or axonal
PMP22
CMT1a is Demylinating
What are some key features of CMT (3)
Often have distal weakness and sensory loss with little disability
presence of pes caus and hammertoes
family history
The acute onset of perpherial neuropahty in the distribution of individual nerves is suggestive of what?
Vasculitis
What are 3 ways to damage a nerve?
1) Ischaemia
2) Compression
3) Cut
Neuropraxia
Demylinationg of a nerve. can be reduced thickness, to multiple segments of no myelin
What happens when a nerve is cut and needs to regenerate?
1) Trophic factors and cytokines released by damaged Schwann cells
2) Macrophages come clean up
3) dedifferentiate Schwann cells mylin loss
4) distal end degenerates (Wallerian degeneration )
4) triggers proliferation of indifferent Schwann cells which some become new new myelinating cells
5) Sprouts produced at cut end
What happens if a regenerating nerve cant reattach to a muscle
Neuroma- painful
Tinels sign
At the Proximal end of the cut nerve can tap and will get a tingling sensation can tell you where the leading edge of regeneration is
What are the two classes of Local anesthetics?
Aminoesters
aminoamides
How do LA’s work
they attach to the inactivated Na channel and stop the regeneration of an Axon potential. Most work from inside the cell
What is the difference between Bupivacaine and ropivacaine?
Bupivacaine is more cardiotoxic because it has a R and S enatiomers
Ropivacaine has just and S-isomer
Both are CNS toxic
How do LAs cross into cells
LAs are amphoteric based on their pkas they dissociate into a base and charged cation. the base will cross the cell membranes and the cation works inside the cell to inhibit the Na chanel
How do waling epidurals work?
LAs will target smaller unmyelinated fibres first. therefore the pain and temp fibres Type A-delta and C fibres will be target first and block pain and temp but not proprioception
Details about Benzocain (3)
1) aminoester
2) Used as topical anesthesia only
3) risk for methemoglobin (cyanosis)
Details about Lidocaine (3)
1) Aminoamide
2) Fast onset
3) used as IV as an antiarrhythmic and in acute and chronic pain
Details about Bupivacaine (2)
Lipophilic and potent long duration of action
R isomer has high cardiotoxicity
good sencory motor seperation
Ropivacaine detials
1) s isomer only of bupivacaine less cardiotoxic
even more motor sparing then bupivacaine
Never inject a La with a ________ into peripheral body parts as it can cause tissue necrosis and gangrene
Never inject a LA with a Vasoconstrictor into peripheral body parts as it can cause tissue necrosis and gangrene
LA potency cooraltes with ______ ______
LA potency correlates with Lipid solubility
Onset of LA action cooraltes with?
Pka, Lower pka faster
what is lipid rescue
Used to treat local anesthetic toxicity
20% lipid emulsion 1.5 ml/KF iV over a min
follow with continues infusion
