Quiz 2 Study Guide What are the 3 main factors that result in the resting potential Negatively charged proteins in the cell Selective permeability of K channels Sodium Potassium Na K pump What attracts K ions into the neuron Electrostatic pressure ions flow towards oppositely charged areas The K is attracted to the negative proteins inside the cell Why can t enough K ions come into the neuron to cancel out the negative charges Because NA is simultaneously being pumped out every 3 for 2 K resulting in negative charge When is the most energy expended during the resting potential or the action potential Resting potential about 70 mV What is the Na K pump and how does it contribute to the resting potential It is the main effector that establishes the resting potential It pumps 3 Na ions out for every 2 K ions it pumps in adding to the negative charge It pumps via the use of ATP energy as it requires a lot What are graded potentials and how do they differ from action potentials Graded potential postsynaptic change in potential that spreads passively along the membrane Decreases over time and distance The greater the stimulus the greater the response What are temporal and spatial summation Temporal The summing of potentials that arrive at the axon hillock at different times Spatial The summing of potentials that come from different parts of the cell How can a given neurotransmitter have excitatory effects at one synapse and inhibitory effects at a different synapse Excitatory open sodium potassium channel Inhibitory opens chloride channels depending on receptor subtype How and where is an action potential generated How is it transmitted along an axon Why does it move in only one direction The arrival of an action potential at the axon terminals of a presynaptic neuron and the subsequent release of neurotransmitter results in a small graded depolarization excitatory postsynaptic potential EPSP or graded hyperpolarization inhibitory postsynaptic potential IPSP of the membrane of the postsynaptic cell depending on whether the postsynaptic receptor is excitatory or inhibitory respectively If enough EPSPs are received the postsynaptic cell s threshold is reached and an action potential is produced The action potential passes down the axon in a single direction like a wave It moves in one direction because it can t go back to where it has already passed because of the refractory period How does the presence or absence of myelin affect this process What is saltatory conduction The presence of myelin speeds it up and saves energy The absence of myelin slows down the transfer Saltatory Conduction the jumping of action potentials from node to node Describe the 2 parts of the refractory phase What contributes to each phase What is the significance of each for neuronal activity Absolute Refractory Phase no new action potentials are produced Relative Refractory Phase only strong stimulation can produce an action potential Describe two mechanisms by which the actions of neurotransmitters are stopped rapidly Chemical inactivation Reuptake transmitter is taken up into the presynaptic cell Degradation rapid breakdown and inactivation of transmitter by an enzyme Explain the math that the postsynaptic neuron uses to process the information that it receives in the form of postsynaptic potentials The math is referring to the sum of EPSPs and IPSPs EPSPs work to excite the cell towards firing an action potential cell is depolarizing going towards threshold IPSPs work to bring the cell away from threshold The neurotransmitter released from a pre synaptic cell results in a graded potential in the post synaptic cell When EPSPs exceed the IPSPs in the axon hillock an all or nothing action potential propagates down the axon Summarize the sequence of events that occurs when a synapse is activated from the arrival of an action potential at the axon terminal to the release of neurotransmitter At chemical synapses the arrival of an action potential causes voltage gated calcium channels to open in the membrane of the axon terminal Calcium influx induces vesicles to fuse to the synaptic membrane and release transmitter the amount released is proportional to the size of the calcium current What two types of effects do transmitters have on their receptors I onotropic receptors open an ion channel Metabotropic receptors activate G proteins What does an EEG measure What is an ERP EEG measures spontaneous electrical activity can reveal rapid changes in brain function ERP reflect the reaction of populations of neurons to discrete stimuli