nervous system + review Flashcards
Which is the best description of why neurons have an absolute refractory period at the end of an action potential.
Because voltage-gated Na+ channels cannot open until after the membrane repolarizes (I.e. reaches approximately resting potential).
Which of the following is the best comparison of signaling via a chemical vs electrical synapse?
Signaling via a chemical synapse takes longer than signaling via an electrical synapse
Based on class discussion, which of the following would completely block transmission across all chemical synapses?
Blocking the activity of voltage gated Ca 2+ gated channels
Synaptic transmission via GABA receptor
Always results in an IPSP in the post synaptic cell, however hyperpolarization or depolarization might occur
plateau
the maximum value of the output value that can be produced by the effector
threshold
the value of an output above which the system will automatically and rapidly drive the output variable to plateau
transport
three major processes
1. pressure: force per unit area
2. concentration gradients
3. electrical charges
simple diffusion
direct diffusion of lipid-soluble subtances across the plasma membrane, CO2, O2, thyroid, steroid hormones
diffusion through protein channels
ion channels + water channels + uniporter carriers
uniporter carrier example from class
the glucose transporters (GLUT 1-4)
co - transporters
move substances in the same direction across the membrane
exchangers
move substances in the opposite direction across the membrane
endocytosis
engulfment of extracellular materials (phagocytosis), removal of spanning proteins from the plasma membrane
exocytosis
release of the messengers from intracellular vesicles, insertion of spanning proteins into plasma membrane
lipid soluble messegers
diffuse into cells, binding receptors in the cytoplasm or nucleas (steroid hormones, estrogen, cortisol)
water soluble messengers
bind transmembrane protein receptors, two main classes include ionotropic and metabotropic
myelin sheath
lipid-rich tissue that insulates the axon and improves the rate of signal transmission. stretches of myelin are separated by nodes of ranvier, which contain all the channels needed to propogate action potentials
the sodium potassium pump
3 sodium are pumped out, and 2 sodium are pumped in - establishes the sodium and potassium concentration gradients that eventually lead to resting potential.
describe leak channels. At rest, signifigantly more ______ leak channels are open as compared to _______
channels that are open at rest and alow their specific ions to flow. potassium, sodium
Resting potential for potassium is
-90
Resting potential for sodium is
+60
describe the giant squid experiment
a recording electrode was placed an extracellular saline, and the voltage was measured. following this, the recording electrode was placed in the cell where the resting potential was determined
describe the initiation of an action potential
something (such as an EPSP) prompts the depolarization of the cell. note: if, at this point the threshold is not reached, then it will return back to resting potential after some time
what happens when the voltage reaches threshold?
V-gated sodium channels start to open up. at the peak of the action potential, the conductance of the sodium is greater than the conductance of the potassium, membrane potential approaches ENa. However, Ek > 0 and there are potassium leak channels it doesn’t quite reach 60 mV.
what happens when the voltage reaches the peak?
The V-gated potassium channels open and the V-gated sodium channels become inactive, beginning a repolarization phase. During this, Gk»_space; GNa, meaning that much more potassium flows out of the cell than sodium into the cell meaning that the membrane voltage approaches Ek again.
why do neurons have an absolute refractory period at the end of an action potential?
Voltage-gated Na+ channels cannot open until after the membrane repolarizes
Do Ek or ENa change during the course of an action potential?
No
