Question

lys originating cieral cortex that may lead to the stimulation of motor in the rtex synapse with alpha motor neurons. Action potentials in the P' contract. ealpha motor neurons, which, in turn, stim primary motor cortex. Pyramidal cells in this region of the ulate skeletal muscles to contract. r several years, DP has controlled his seizures with a singl rbamazepine (Tegretol®). However, duri on rked e medication onths, he has increase in seizure activity. His neurologist has now prescribed a second g the last 6 m nerienced a a ication topiramate (Topamax®), to be taken along with carbamazepine What is the ab period (RRP)? solute refractory period (ARP) in neurons? The relative refractory The mechanism of action of carbamazepine involves a decreased rate of recovery of voltage-gated Na* channels from their inactivation state. What effect does carbamazepine have on the ARP? The RRP? What effect does carbamazepine have on the frequency of action potential generation in these neurons? Compare and contrast temporal summation and spatial sumimation of postsynaptic potentials. l summation in postsynaptic neurons likely to be altered by

Answer 1

1 Absolute refractory period is the period after action potential in which neuron cannot generate another action potential because sodium channels are inactive.Relative Refractory period is the period after firing when a neuron will not fire again no matter how strong the incoming message maybe.This happens when the neuron is in hyperpolarization,where there are sodium channels either closed or inactivated and potassium channels are still open where potassium is effluxing into EC and membrabrane potential becomes more,requiring a greater stimulus for it to reach threshold.

2 Carbamazepine causes sodium channels to remain in absolute refractory period,used for trigeminal neuralgia.

3 In response to a depolarizing current pulse ,a series of high-frequency repetetive action potentials filled the entire duration of the current pulse in the control trace. Carbamazepine markedly reduced the number of action potentials elicited by the current pulses.

4Temporal summation occurs when a single pre-synaptic neuron fires many times in succession ,causing the post-synaptic neuron to reach its threshold and fire.Spatial summation occurs when excitatory potentials from many different pre-synaptic neurons cause the post-synaptic neuron to reach its threshold and fire.Spatial summation is like using many shovels to fill up a whole all at once.Temporal summation is like using a single shovel to fill up a hole over time.Both methods work to fill up the whole.