Action potential propagation Flashcards
what is AP propagation
the movement of an action potential along the membrane of a single cell
motor neurons have what function?
send impulses to muscles to generate movement, initiate motor movement
describe motor neuron basic structure
cell body (soma), coming off of soma are small projections called dendrites
- on other side of soma is a long projection that extends called an axon
- axon hillock is where axon connects to cell body
- at end of axon, small branches called terminals
basic structure and function of bipolar neurons (interneuron)
have 2 projections- one single dendrite coming off one end/pole of cell body and one single axon coming off the other end/pole
- these are sensory in function and are involved in olfaction(smell) and vision
Sensory neurons are called ___ neurons, not ___
pseudounipolar
unipolar
describe structure of pseudounipolar neurons
dendrite on top and axon on bottom- appears to be a single projection coming off of cell body, but differentiated according to function
- top part is called peripheral axon (functions like axon & carries info up from projections down toward the cell body)
- bottom part called central axon (takes sensory info and sends it toward the CNS to be registered) –> info seems to bypass the cell body, cell body does not have a role in processing/integrating that info
describe multipolar (motoneurons)
have a few short intermediate dendrites coming off one end of cell body & one single axon coming off of other
- involved in neural pathways called through circuits, a long distance neural pathway (neural pathways called neural circuits)
bipolar neurons aka ___ neurons
interneurons
pseudounipolar neurons aka ___ neurons
sensory neurons
multipolar neurons aka ___ neurons
motoneurons
structure & function of nerve cell is closely related…
what is the zone of dendrites and soma
zone of impulse integration
- the part of the neuron that receives and processes incoming stimuli
- a nerve cell can receive multiple stimuli at any given time, not just one –> dendrites and soma integrate these multiple signals into one final signal, which travels to axon hillock…if final signal above threshold–>AP
structure & function of nerve cell is closely related…
what is the zone of axon hillock
zone of spike initiation
(spike is term for AP), AP travels along axon
structure & function of nerve cell is closely related…
what is the zone of axon
zone of impulse propagation
movement of AP across length of single cell
structure & function of nerve cell is closely related…
what is the zone of terminals
zone of impulse transmission
when AP gets to terminals, only option is to jump to another cell (movement of AP from one cell to another cell)
in a typical motor neuron, in what structures are voltage-gated Na+ and K+ channels found?
exclusively found in axon and terminals (absent in cell body & dendrites)
in a typical motor neuron, in what structures are ligand-gated channels found?
in dendrites and cell body
how are ligand-gated channels activated
by some sort of chemical messenger that binds to the channel, most common chemical messenger is a neurotransmitter
in a typical motor neuron, in what structures are mechanically-gated channels found?
what are these channels?
in dendrites and cell body
mechanically-gated channels are activated by a result of stretch of pressure or temp on the membrane
can an action potential be generated in cell body or dendrites of nerve cell?
no
explain why an action potential is not generated in soma or dendrites
all the stimuli that come in cause a grated potential- a change in membrane potential that is directly proportional to the strength of the incoming stimulus
ex: depolarizing stimulus of 10 mV will depolarize the membrane by 10 mV- but no action potential because no voltage-gated channels to be spontaneously activated
what is electrotonic spread
the movement of an electrical signal with progressive loss of strength
explain signal integration that happens at soma and dendrites (start with +10 depolarizing stimulus)
10 mV depolarizing stimulus comes into inner surface of membrane –> opens sodium channels, positively charged sodium builds up on inside of membrane, changing potential by 10 mV –> this signal then begins to move laterally along membrane, moves b/c there is a high concentration of positive charge at the point where the signal entered, so move from + to - by electrical attraction (this signal is due to sodium, in that exact spot, high conc of sodium, but everywhere else: low conc.
- so, once a signal is established, starts to move down its electrical gradient –> as sodium diffuses along inside of membrane, some of it will be pumped through the sodium pump and some will diffuse back out through random diffusion…so as signal moves, loses strength (electrotonic spread) 10 mV becomes 9…8…7…6…5
- however, soma can receive multiple stimuli at a time, so at the same time, another 10 mV depolarizing signal can be added…now have 15 mV depolarizing signal (soma and dendrites progressively add these signals to form one signal of resulting strength—> final strength of it determines where you get an AP at axon hillock or not)
- also, a negative 10 mV signal can come in –> opens potassium channels, K increases outward, inside of membrane more negative, hyperpolarization
- if + and - signals meet, come together and cancel each other out
positive signals/stimuli to the membrane are called ___ signals, involving what ion?
excitatory signals
positive stimuli open sodium channels, causing depolarization of membrane, takes it toward threshold –> AP
negative signals/stimuli to the membrane are called ___ signals, involving what ion?
inhibitory signals
negative stimuli open potassium channels, cause hyperpolarization, takes potential away from threshold –> prevent AP