110 Peripheral neuropathy Flashcards
What is the potential difference across a nereve cell membrane?
-65mV
What is the MOA of lidocaine?
- inhibits the fast-gated voltage sodium channels
- stops AP signal propogation
- no AP in post synaptic neurone
What is Dale’s principle?
A single nerve makes a single NT
Which receptors are found in the post-synaptic neurones in the SNS?
- nicotinic
- adrenergic
What are the 2 main NTs of the SNS?
- ACh
- NA
In which division of the ANS does ACh act upon muscarinic receptors?
- parasympathetic postganglionic neurones in target organs
Which division of the ANS are noradrenergic receptors found?
Sympathetic neurones - target organs
What type of drugs are muscarine and pilocarpine?
Muscarine receptor agonists
What type of drug is atropine?
Muscarinic antagonist
WHere are α-1 adrenergic receptors found?
(4 listed)
- vascular SM
- papillary dilator muscle
- prostate
- heart
What effects to phenyleprine and methoxamine have on α-1 adrenergic receptors?
Agonists - e.g. to treat hypotension
Where are α2 adrenergic receptors found?
(4 listed)
- platelets
- SM
- nerve terminals
- adipocytes
What type of drug is yohimbine?
α2 adrenergic receptor antagonist - used to treat impotence
What type of drugs are isoproterenol and salbutamol?
β2 agonists
- increase HR
- increase cardiac output
- bronchiol SM relaxation
Clonidine and guanfacine are used to treat HTN - which receptors do they act on?
α-2 agonists
What kind of drugs are:
- timonolol
- propanolol
- bisoprolol
- β antagonists
- bisoprolol selectively blocks catecholamine stimulation of β1-adrenergic receptors in the heart and vascular smooth muscle
- –> reduction of HR, CO, systolic and diastolic BP
Neosigmine and pyrostigmine = ACh esterase inhibitors
What disease are they used to treat?
Myasthenia gravis
Which NT do the following affect?
- reserpine
- cocaine
- aphetamines
- parglycine
NA
What is Frey syndrome?
- Disorder of the ANS
- pts sweat from focal area on cheek instead of salivating
- inappropriate regeneration of damaged nerves following damage
What are the S&S in Carpal Tunnel syndrome?
- pain causing nocturnal waking
- thenar eminence wasting
- numbness and pain in thumb, index, middle and half of ring finger in affected hand
What is the cause of Carpal Tunnel?
Compression of the median nerve as it passes through the transverse carpal ligament
Which nerve is affected in Saturday night palsy?
Radial nerve - wrist drop characteristic sign
What is used to treat Guillan Barre?
- plasma exchange
- IV Ig’s
- speed up revovery but doesn’t improve overall outcome
What do gabapentin, pregabalin and amitriptyline have in common?
Drugs used to treat nerve pain
What kind of neuropathy is Meralgia parasthesia?
- Mononeuropathy
- loss of sensation to the anterolateral part of the thigh
- compression of the lateral cutaneous nerve of the thigh
What causes Charcot Marie Tooth syndrome?
Demyelination of peripheral nerves due to genetic mutation of Schwann cells
What type of nerve injury is Wallarian degeneration?
- axonopathy
- degeneration of axons distal to injury
- clinical presentation
- focal ischaemia
- vasculitis
In which type of diseases does distal axonal degradation happen?
- DM
- alcoholism
- HIV
i.e. chronic diseases
When is regeneration not possible in distal axonol degeneration?
(3 listed)
- if cell body is damaged
- if the neuropathic injury is irreversible
- if stress on the nerve isn’t removed
What is polyarteritis nodosa?
Vasculitis of small arteries due to attack of rogue immune cells - causes vasculitic neuropathy
What kind of syndrome is Lambert Eaton Myasthenic syndrome?
- NMJ disorder
- ABs against Ca2+ channels
- affect ACh release
Associated with SSLC (small cell lung cancer)
Typically weakness in arms and legs
What is the autoimmune component of Myasthenia Gravis?
- ABs against ACh receptor
- i.e. NMJ disorder
- muscle weakness
How is the NMJ damaged in Myasthenia Gravis?
- autoimmune reaction
- ABs present ACh receptors to mactophages
- they internalise the receptors –> damage
What are the possible treatments for MG?
- IV IG’s
- plasma exchange
- Ach esterase inhibitors (non selective - cause GIT symptoms)
- immunosuppression to allow NMJs to repair
Which channels are not switched off in neuromyotonia?
K+
