Neuro 4 PG Flashcards
how are action potentials produced and how are they conducted along the axon?
through the action of voltage-activated ion channels
what are voltage-activated ion channels
ion channels that open or close in response to changes in the level of the membrane potential
why is membrane potential of of a neuron at rest is relatively constant despite the high pressure acting to drive Na+ ions into the cell?
This is because the resting membrane is relatively impermeable to Na+ ions and because those few that do pass in are pumped out
what marks the end of the rising phase in action potential?
the sodium channel closing
what is the beginning of depolarization in action potential?
the continued leaving of K+ ions.
what ions does action potential involve?
only those right next to the membrane
what is the absolute refectory period?
a brief period of about 1 to 2 milliseconds after the initiation of an action potential during which it is impossible to elicit a second one.
what is the relative refractory period?
the period during which it is possible to fire the neuron again but only by applying higher-than-normal levels of stimulation. The end of the relative refractory period is the point at which the amount of stimulation necessary to fire a neuron returns to baseline.
what are the two important ways that axons differ from conduction of EPSPs and IPSPs
-conduction of action potentials along an axon is nondecremental (action potentials do not grow weaker as they travel through axonal membranes)
-action potentials are conducted more slowly than postsynaptic potentials
the conduction os EPSPs and IPSPs is
passive
axonal conduction of action potential is
largely active
antidromic conductions
if electrical stimulation of sufficient intensity is applied to the terminal end of an axon, an action potential will be generated and will travel along the axon back to the cell body
orthodromic conduction
axonal conduction in the natural direction
where can myelinated axons pass through the axonal membrane
at the nodes of Ranvier
what is saltatory conduction
the transmission of action potentials in myelinated axons
where do axodendritic synapses terminate
dendritic spines
what are axiomatic synapses
synapses of axon terminal buttons on somas
what can axoaxonic synapses do
mediate presynaptic facilitation and inhibition
directed synapses
synapse at which the site of a neurotransmitter release and the sire of neurotransmitter reception are in close proximity
non directed synapse
synapse at which the site of release is at some distance from the site of reception
-also referred to as string-of-bead synapses
what are large neurotransmitters
neuropeptides
neuropeptides
short amino acid chains composed of between 3 and 36 amino acids; short proteins
coexistence
many neurons contain two neurotransmitters
exocytosis
process of neurotransmitter release
reuptake
The drawing back into the terminal button of neurotransmitter molecules after their release into the synapse; the most common mechanism for deactivating a released neurotransmitter.
