What are the sympathetic effects of activation of the Nucleus of the Solitary Tract (NST) due to increased BP and HR?
The NST sends excitatory projections to the venterolateral medulla depressor area.
This sends GABAergic projections to rostral venterolateral medullary depressor area (RVLM), thus inhibiting it.
The RVLM normally provides sympathetic activation to the heart.
Name 2 ganglionic blockers.
Which drugs can be used for treatment of chronic neuropathic pain?
What is Frey Syndrome?
The parasympathetic fibres of the trigeminal nerve are "diverted" from the parotid gland to overlying sweat glands.This causes sweating when there is meant to be salivation.
What are the 2 layers of the enteric nervous system what does each 1 broadly control?
- Myenteric plexus (Auerbach's); GIT motility
- Submucosal plexus (Meissner's); Senses environment and regulates GIT blood flow.
What are the consequences of compression of the common peroneal nerve?
Weakness of ankle dorsiflexion and eversion
Name 2 different inhibitory neurotransmitters.
What are the subtypes of muscarinic receptors and where is each 1 found?
- M1; CNS, salivary glands, postganglionic sympathetic neurones
- M2; Myocardium, smooth muscle and presynaptic sites
- M3; Exocrine glands, smooth muscle, iris sphincter
- M4; CNS
- M5; CNS
What is meralgia paraesthetica?
Compression of the lateral cutaneous nerve of the thigh
What are the effects of Isoproterenol?
Increases HR and contractile force, cardiac output due to agonism of β1 & β2
What are the symptoms of motor neuropathy?
- Muscle wasting
- Muscle fasciculation
What is the main antagonist of the α2-adrenergic receptor?
What is saltatory conduction?
It occurs when an action potential "jumps" from Node of Ranvier to the next along a myelinated neurone
Where are the cell bodies of the sympathetic preganglionic and postganglionic neurones found?
- Preganglionic; Spinal level of which the nerve leaves
- Post ganglionic; Paravertebral (sympathetic) chain.
What transporter establishes and maintains the concentration gradient of Na and K across the membrane?
The Na-K ATPase, pumps 2 K in and 3 Na out of the cell
Which division of the ANS is linked to the "fight or flight" response?
What is special about the sympathetic nervous supply to the adrenal medulla?
It is innervated only by preganglionic sympathetic neurones.
What are the features of radial nerve palsy?
- Wrist drop
- Variable sensory loss
Name 3 β antagonists.
- Timolol; non-specific for glaucoma
- Propanolol; reduces HR, contractile force and BP
- Bisoprolol; β1
- Atenolol; β1
Where are nicotinic receptors found?
- Post-ganglionic neurones
- Neuromuscular junction
What is the mortality rate for GBS?
Which roots of the spinal cord does all the sympathetic nervous system derive from?
Where is the origin of the parasympathetic nervous system?
- Head; oculomotor, facial, glossopharyngeal and vagus nerves
- Sacral region; S2-4
Where do the pre-ganglionic parasympathetic nerves terminate?
Usually in the walls of the visceral organ.
Name agonists of the muscarinic receptor.
- Pilocarpine (eye use)
How does ulnar nerve compression present?
- Hypothenar wasting
- Weakness of finger abduction and opposition of little finger
- Sensory changes on medial 2 fingers
What reversible acetyl cholinesterase inhibitors can be used in the treatment of glaucoma?
What are the signs of carpal tunnel syndrome?
- Numbness in lateral 3 and half fingers
- Weakness in thumb abduction
- Wasting of Thenar eminence
What happens to the voltage gated Na channels towards the peak of the action potential?
They enter a state of inactivation and prevent further Na movement
Why is there an overshoot of repolarisation of the membrane (after-hyperpolarisation)?
The voltage gated K channels are slow to inactivate so there is greater K efflux
How do local anaesthetics such as Lidocaine, anti-convulsants such as Carbamazepine and the poison Fugu from the puffer fish work?
They block the voltage gated Na channels so action potentials can not be initiated or conducted along nerves.
What are the main prevertebral ganglia called (i.e. not part of the sympathetic chain)?
- Superior mesenteric
- Inferior mesenteric
What is the advantage of saltatory conduction of action potentials?
It allows the neurone to conduct an action potential up to 50 times faster than unmyelinated axons
What are the 6 main mechanisms of peripheral nerve damage?
- Axonal degeneration
- Wallerian degeneration
Name antagonists of the α1-adrenergic receptor.
Which channels are activated by an excitatory neurotransmitter?
The ligand gated Na channels
What receptors are activated in response to partial depolarisation?
Voltage gated Na channels
What causes neuromyotonia?
Antibodies against voltage-gated potassium channels.
Where does glutamate act when the baroreceptors sense an increase in BP and HR?
The Nucleus of the Solitary Tract
What are the 3 main types of peripheral neuropathy?
- Demyelinating neuropathy
- Axonal neuropathy
Which ion's equilibrium potential is the membrane potential close to?
What condition is associated with a genetic mutation in the Schwann cells?
Charcot Marie Tooth disease
What is Horner's Syndrome?
Cranial nerve damage that causes ptosis, decreased pupil size and anhidrosis
What causes Lambert Eaton Myasthenic syndrome?
- Antibodies against voltage gated calcium channel
- Most (60%) is associated with small cell lung cancer
Through which structure do postganglionic sympathetic neurones pass through to re-enter the spinal nerves to be distributed to various organs?
Grey rami communicans
Where are muscarinic receptors found?
They are found on the effectors of the parasympathetic nervous system
What reversible inhibitors of acetyl cholinesterase can be used for the treatment of Myasthenia gravis?
What substance is released by the preganglionic sympathetic neurones?
What channels are responsible for the repolarisation of the membrane?
Voltage gated K channels
What is the disability outcome after GBS?
- 10% significantly after 1 year
- 11% moderate after 1 year
What are the parasympathetic effects of activation of the NST?
The excitatory projections of the NST extend to the nucleus ambiguus which results in activation of the parasympathetic innervation of the heart.
What is the main consequence of α1-adrenergic receptor activation?
Smooth muscle contraction including pupillary dilatory muscle and urethral sphincter.
What is the main difference between nicotinic and muscarinic receptors?
- Nicotinic receptors are ionotropic
- Muscarinic receptors are metabotropic
What must you monitor in a patient with GBS?
- The respiratory muscle strength
- Cardiac rhythm
What substance is released by the postganglionic sympathetic neurones?
How do poisons such as Sarin or organophosphates caused injury and death?
They irreversibly bind to acetyl cholinesterase, leading to an accumulation of ACh in the synaptic clefts leading to continuous muscle contractions.
What are the most common nerves to be injured by compression, and where does each 1 usually get compressed?
Ulnar nerve; as it crosses the elbow
Radial nerve; as it wraps around the humerus
Median nerve; as it passes through the carpal tunnel of the wrist
Lateral cutaneous nerve of the thigh; as it passes through the inguinal canal
Common peroneal nerve; as it passes around the fibula
What are the agonists of the α2-adrenergic receptor?
Which fibres of the sympathetic system are the longest, pre or post-ganglionic?
What are the effects of Reserpine?
It prevents the storage of noradrenaline in the presynaptic terminal.
What are the 3 main divisions of the autonomic nervous system?
What are the 2 specific treatments for GBS?
- IV immunglobulins
- Plasma exchange
Name a agonist of the nicotinic receptor
- Varenicline (treatment of nicotine dependence)
- Succinyl choline (muscle relaxant)
What is the function of voltage gated Ca channels in the presynaptic terminal?
They convert the electrical signal into a chemical signal by initiating events that lead to the release of neurotransmitters from the presynaptic terminal
What causes Myasthenia Gravis?
Antibodies against acetylcholine receptor
What are the antagonists of the muscarinic receptor?
What is orthostatic hypotension?
The ANS does not react quick enough or strong enough to maintain the BP when a person stands.
On which receptor does Salbutamol act?
What are the symptoms of a sensory neuropathy?
Which fibres, pre or postganglionic neurones of the sympathetic nervous system are myelinated?
What substance do parasympathetic preganglionic neurones utilise?
What are the symptoms of an autonomic neuropathy?
- Dry eyes and mouth
- Orthostatic hypotension and syncope
- Bladder hypersensitivity
- Loss of HR variability
Through what structure do the sympathetic roots enter the sympathetic chain?
White rami communicans
Where can a neurone synapse on another neurone (3 places)?
Dendrite; Axodendritic synapse
Cell body; axosomatic synapse
Axon; axoaxonic synapse
What are the treatment options for carpal tunnel?
- Wrist splints & steroids short term
- Decompressio surgery
What do parasympathetic post-ganglionic neurones use as a neurotransmitter?
Where are 3 different the β-adrenergic receptors found?
- β1; Heart
- β2; Respiratory, uterine and vascular smooth muscle, skeletal muscle and liver
- β3; Fat cells
What are the neuropathies classified according the number of neurones affected?
- 1 neurone = mononeuropathy
- A few = mononeuritis multiplex
- Lots = polyneuropathy
Name agonists of the α1-adrenergic receptor?
What can cause Guillain-Barre Syndrome (GBS)?
- Upper respiratory tract infection
- Viral illness from CMV or EBV
- Campylobacter jejuni
Where is the α2-adrenergic receptor located?