Neurotransmission Flashcards
What is contained is presynaptic part?
Vesicles containing neurotransmitter
Describe the structure of post-synaptic?
Junctional folds with Ach receptors and cholinesterase enzymes
Where is the origin of end plate potentials?
At the endplate
What do mini end plate potentials do?
Spontaneous release of one packet of neurotransmitter into the synaptic cleft
What is meant by a quantal?
Neurotransmitter put into packets
What are EPPs built from?
A large quantity of minEPPs
What neurotransmitter produces an EPSP?
Acetylcholine
What receptor does Ach fuse to?
Nicotinic Ach receptor
How many molecules of Ach are required to activate receptor?
2
How does the nicotinic Ach receptor change when the Ach fuses with it?
Rearrangment of receptor allows permeation of ions through aqueous pore. Permeable to both Na+ and K+ when opened, depolarising membrane
What receptor type is involved in generating IPSP?
Ligand gated chlorine channel
What neurotransmitter is involved in generating IPSPs in the brain?
GABA
What neurotransmitter is involved in generating IPSPs in the spinal cord?
Glycine
What two changes occur in GABA receptors in the generation of IPSPs?
- Hyperpolarisation of membrane
- Membrane becomes leakier to current so more difficult to generate a current
What stimulus are muscle spindle fibres sensitive to?
Stretch (mechanoreceptor)
Describe how monosynaptic reflex works?
- Muscle spindle fibres sends la afferent into spinal cord via dorsal root
- Synapses in ventral horn to alpha motor neuuron
- Sends axons to homonymous muscle making synapses with numerous muscle fibres
What is meant by recipricol antagonistic inhibition?
When one muscle is flexed, other is inhibited so it can relax
How is the antagonistic muscle relaxed?
Also well as monosynaptic activation of flexor neuron, there is another synapse onto interneuron in spinal cord.
Synapse is excitatory on inhibitory interneuron which release glycine at its synapse to inhibit antagonistic muscle.
What is the difference between neurotransmission, neuromodulation and neurotrophic factors?
Neurotransmission: ms
Neuromodulation: takes seconds to minutes
Neurotrophic factors: slowest of all- minutes to hours
What type of receptor is used in fast neurotransmission
Pentameric and tetrameric receptors that incorporate ion channels
What type of receptor is used in neuromodulation?
G protein coupled receptor
What happens when neuromodulator binds to GPCR?
Activates second messenger which causes series of reaction which causes modulation of ion channels
Is glutamate fast, modulator or both?
Both
Is Ach fast, modulator or both?
Both
Is glutamate fast, modulator or both?
Both
Is GABA fast, modulator or both?
Both
Is glycine fast, modulator or both
Fast
Is 5-HT fast, modulator or both?
Both
Is noradrenaline fast, modulator or both?
Modulator
Is dopamine fast, modulator or both?
Modulator
Where specifically does Ach bind to on channels?
C loops
Name the 2 mechanisms involved in termination of transmitter?
Neurotransmitter breakdown
Neurotranmitter reuptake
What enzyme breaks down Ach?
Acetylcholinesterase
What can inhibit acetylcholinesterase?
Organophosphate nerve agents
How is glutamate reuptaken?
Glutamate transporter reuptakes into neurons and glial cells
Runs of Na+ gradient
How is GABA reuptaken?
reuptaken into presynaptic terminals and astrocytes by GATs
What is M response?
direct activation of motor unit by electrical stimulation
What is H reflex?
Electrical equivelent to stretch reflex
What is F wave?
Antidromic motor nerve action potentials bouncing off the alpha motor neurons
What is the effect of peripheral demyelination?
Effects conduction time or number of axons that work
What is meant by giant motor unit and what condition is it seen in?
Alpha motor neurons die- denervation of motor fibres. surviving motor neurons sprout and send new collaterals to muscle fibres. Large motor units when 1 motor neuron innervates more than usual
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