CMB1004/L10 Signal Transmission Flashcards
What is the velocity of an action potential related to? (2)
Diameter of axon (D)
Membrane resistance (Rm)
How can signal transmission speed be increased? (2)
Increase D
Increase Rm
What occurs at nodes of Ranvier?
Current jumps from node to node
What feature do nodes of Ranvier have that aids signal transmission?
High density of Na+ channels
What is multiple sclerosis? (3)
Demyelinating disorder causes inability of signals to jump between nodes of Ranvier
Demyelination is scattered and progressive
Gradual loss of motor control
What do secretory vesicles contain at the synapse?
Neurotransmitter
What occurs when action potential invades the axon terminal? (6)
Presynaptic membrane depolarised
Opening of Ca2+ ions in presynaptic membrane
Vesicles fuse with presynaptic membrane
Neurotransmitter released into synaptic cleft
Neurotransmitter binds to receptors on postsynaptic membrane
Ligand-gated Na+ channels open in postsynaptic membrane
What is the equation for EndPlate Potential?
EPP = (E(Na)+E(K))/2
What is the voltage of a typical EndPlate Potential?
-15mV
Why is there no action potential at junctional folds?
No voltage-gated Na+ channels
When do mini-EPPs occur?
Randomly when nerves and muscles are at rest
How many vesicle fusions is 1 mini-EPP equivalent to?
1
What does the quantal nature of transmission refer to?
The fact that vesicles release all of their contents or none at all
Approximately how many vesicle fusions occur during EPP?
100
Approximately how many vesicle fusions occur during normal action potential at NMJ?
200-300
