What name is given to the label 1?
Threshold
Depolarisation
Repolarisation
Hyperpolarisation
What name is given to A?
What name is given to B?
What name is given to C?
The absolute refractory period refers to the period of hyperpolarisation in an action potential.
The refractory period is important for what?
Unidirectionality
Discrete action potentials
Conductance is approximately equal to permeability.
How is an action potential propagated in a non-myelinated axon?
The local current in an axonal section flows to the next "segment" of the axon, causing depolarisation of that part of the membrane. This continues, causing propagation of the action potential.
The non-myelinated axon is insulated by a myelin sheath which allows current to 'jump' from node to node, via "saltatory conduction".
Anterograde transport occurs away from the cell body of a neurone.
Kinesin are motor proteins that partake in anterograde transport.
Kinesin walk towards the positive end of microtubules found in the axon, which usually leads away from the cell body of the neuron.
Motor proteins carry vesicles or membrane bound organelles like mitochondria to their desired location.
What is the correct process of wallerian degeneration?
Trauma -> Axonal breakdown -> Macrophage invasion from nearby blood vessels -> Phagocytosis -> Ready for regeneration
Trauma -> Axonal breakdown -> Axonal fragments absorbed into bloodstream -> Ready for regeneration
What is the correct process of wallerian regeneration?
Edge of trauma site develops an axonal sprout -> the sprout encourages schwann cell division -> the schwann cells release neurotrophins to guide the growth cone -> growth cone grows -> axon regenerated
Edge of trauma site develops an axonal sprout -> the sprout encourages oligodendrocyte division -> the oligodendrocytes release neurotrophins to guide the growth cone -> growth cone grows -> axon regenerated
A class 1 nerve injury would cause what?
Minor compression and no axon degeneration
Crushing and resulting degeneration
Severe tear and endoneurium will be compromised
A class 2 nerve injury would cause what?
A class 3 nerve injury would cause what?
Reactive astrocytes contribute to CNS nerve regeneration.
What part of a local anaesthetic is shown by the red question mark?
Aromatic ring
Linkage
Amine group
What part of a local anaesthetic is shown by the green question mark?
What different type of link may be present in the part of the LA labelled with a blue question mark?
Ester
Amide
Carbonyl
Ketone
Why do most modern local anaesthetics have an amide linkage rather than an ester linkage?
Broken down more slowly - longer time of action
Broken down more quickly - shorter time of action
More prone to causing allergies
Less prone to causing allergies
The function of the aromatic ring in the local anaesthetic is to provide lipid soluble properties.
Local anaesthetics are...
Weak bases
Weak acids
Strong bases
Strong acids
Following on from the previous question, would a local anaesthetic be ionised in...
Acidic conditions
Alkaline conditions
The ionised form of the local anaesthetic can cross the plasma membrane to exhibit its action.
The ionised version of the local anaesthetic blocks the voltage-gated Na+ channels to prevent action potentials being generated.
Why is local anaesthetic less effective when a bacterial infection is present?
Local anaesthetics are weak bases. Bacteria that are present at the infection site will be metabolising substances which creates an acidic environment. An acidic environment will cause ionisation of the local anaesthetic. The ionised form of the local anaesthetic cannot cross the plasma membrane. Less local anaesthetic crossing the PM means there is less blocking of VG Na+ channels and therefore the local anaesthetic is less effective.
Local anaesthetics are weak acids. Bacteria that are present at the infection site will be metabolising substances which creates an alkaline environment. An alkaline environment will cause ionisation of the local anaesthetic. The ionised form of the local anaesthetic cannot cross the plasma membrane. Less local anaesthetic crossing the PM means there is less blocking of VG Na+ channels and therefore the local anaesthetic is less effective.
Lower diameter, less myelinated axons are more sensitive to local anaesthetic.
What is topical application of local anaesthetics?
Surface application
Blocking a branch of nerve fibres
Block somewhere along the length of the nerve before it branches
What is meant by infiltration in the context of application of local anaesthetics?
What is meant by nerve block in the context of application of local anaesthetics?
What side effects could result from local anaesthetic in high doses?
Decrease cardiac muscle contractility.
Increase cardiac muscle contractility.
Vasodilatation
Vasoconstriction
What adjunct might be used with local anaesthetic?
Adrenaline
Bupivicaine
Omeprasole
Acetylcholine
Transmitter binding to post-synaptic receptors causes a conformational change.
Many neurotransmitters can bind to one receptor subtype.
Metabotropic receptors are an ion channel pore which opens upon neurotransmitter binding.
Temporal summation increases the number of synapses firing at the same time to help threshold to be exceeded.
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