Quiz 2 - Quiz starts slide topic 2 slide 17 1 Action...

Quiz starts slide topic 2, slide 17
1. Action potentials are propagated down the axon
1. The transmission of action potentials can be compared to a
“snapshot” of dominos falling, where each domino is in a different
position
2. Simultaneous recordings show that each section of axon is
experiencing a different phase of the action potential
1. As electrical energy of AP passes from one part of axon to the
next, the energy state is reflected in the membrane potential of
that region
1. Has to get sent down axon. Has to be regenerated at every
subsequent location along the axon
2. One neuron is generating 100’s of action potentials because it
has to be continually remade at every point on the axon
3. Action potential hasn’t arrived at the end yet. But it’s already
starting to depolarize (after time 11)
1. Further along in depolarizing as numbers go down
2. Peak depolarization at axon (point 7)
3. At point 1, 2, 3 already depolarized. Constantly follows
along after action potential
2. Principle of Dynamic Polarization cajal
1. The refractory period prevents backward movement of the action
potential
1. The trigger zone is in the refractory period, K+ gates have opened
and NA+ inactivation gates have closed. Loss of K+ from the
cytoplasm repolarizes the membrane
1. In the distal parts of the axon, local current flow from the
active region causes new sections of the membrane to
depolarize
2. Keep action potential going in one direction—uni directional flow
3. Once positive charge is inside neuron, equal amount of sodium
ions flow to the inactive region and refractory region
1. The charge to the refractory region will make it from
hyperpolarization to resting potential
1. When potassium is leaving
2. The charge to the inactive region will make it go to threshold
1. No threshold=no action
potential
3. Problem—the Synapse
1. For action potential to cross, must use neurotransmitters
1. Neurotransmitters= chemicals

4. Cell to cell communication occurs via synapses
1. An action potential depolarizes the axon terminal
2. The depolarization opens voltage-gated Ca2+ channels and Ca2+
enters the cell
3. Calcium entry triggers exocytosis of synaptic vesicle contents
4. Neurotransmitter diffuses across the synaptic cleft and binds with
receptors on the postsynaptic cell
1. Calcium opens into presynaptic terminal  triggers events
2. Inside presynaptic terminals, vesicles
5. Synaptic transmission nerve to muscle
1. Release neurotransmitter which binds to receptor on muscle
membrane Acetylcholine (Ach)
2. Results in electrical stimulation of muscle
3. Alpha motor neurons generated action potentials, release
acetylcholine—used to contract muscles
6. NMJ problems (neuro muscular junction)
1. Botulism (botulinum toxin): prevents Ach exocytosis
1. Most deadly poison. People inject it to the muscles in our face.