6.5 Neurons & Synapses Flashcards
What is the role of a dendrite?
Collects nerve impulses and converts the chemical impulses into electrical ones
Role of the soma?
Metabolic functions to keep the cell alive
Role of Myelin sheath?
Speeds up transmission of nerve impulse via saltatory conduction. The action potential just hops between the Nodes of Ranvier (between the myelin sheaths).
What is the resting potential?
-70mV, inside is more negative than outside, charge difference across membrane when neuron is not firing
What is the threshold potential?
stimulus to open voltage-gated NA+ channels, -55mV
What are action potentials? Describe the 3 steps.
They are the rapid changes in charge across neuron membranes, when a neuron is firing.
1) Depolarisation: a stimulus opens Na+ channels, so Na+ goes into cell, making the outside negative
2) Repolarisation: K+ channels open and they rush out of the cell, making the outside positive again
3)Refractory Period: Na-K pumps bring them back in their original position, so that the nerve can fire again
How does the nerve impuls travel along the axon, what is so special about the channels?
They are voltage gated, so if the neighboring segment of the axon is repolarised, mine starts to repolarise.
How do synapses work?
When the action potential reaches the pre-synaptic node, it triggers the release of Ca+ into the node, which causes neurotransmitter vesicles to fuse with the membrane and release the neurotransmitters across the synaptic cleft. The NB bind to receptors on the post synaptic node, which act as Na+ pumps, propagating the nerve impulse.
What are Neonicotinoid pesticides?
They bind to the acetylcholine receptors, but can’t be broken down, so they overstimulate the post synaptic node, and can cause convulsion and paralysis. They bind much stronger to the receptors in insects, than in humans, so it is no threat to us, but they have caused reductions in bees and birds populations, so their use is restricted in some countries.
What is Acetylcholine?What is it often involved with?
It is a Neurotransmitter, which is broken down into Acetyl and Choline after binding to receptors. They are often involved in muscle contraction and in parasympathetic responses (rest, digest).
