Lecture 3 Flashcards
the phenomenon of _________ does not allow an AP to backfire
inactivation of Na+ channels
inactivation of Na+ channels is referred to as the _______ refractory period
absolute
What two factors affect the speed of an AP
diameter (larger diameter = faster) and myelination
Myelin sheath has break called)_______ nodes where APs are generated
Ranvier
5 Steps of conduction of AP
- membrane depolarization to the threshold
- generation of an AP
- local currents spread passively
- they depolarize adjacent areas of he membrane
- a new action potential is generated
Action potential cannot backfire because of the absolute refractory period which is due to
inactivation of Na+ channels
the fastest conducting axons in the nervous system would have 2 characteristics?
large diameter and myelination
the slowest conducting axons in the nervous system would have what 2 characteristics?
small diameter and unmyelinaed
from the soma to terminal branches
orthodromic conduction
from the end of the axons to the soma
Antidromic conduction
Sensory neurons have what type of conduction
antidromic conduction
motor neurons have what type of conductin
orthodromic conduction
body of the cell: the site of input signals
soma
short branches originating from the soma; sites of inputs
dendrites
a long branch; transmits output signals
axon
the site where the axon exits the soma; typically the site of generation of APs
axon hillock
a brush at the end of the axon
terminal branches
a fatlike substance covering the axon; it increases the speed of conduction of APs
myelin
breaks in the myelin sheath; places wher APs are generated
Ranvier nodes
many axons running together
nerve (peripheral) or neural tracts (central)
______ allow the dendrite to start generating APs and continue to do so without any external stimuli as long as the membrane potential stays above threshold
Persistent Inward Currents (PIC)
PICs are good for _____ and are found in what type of neurons
postural muscles and in isometric situation
Alpha motor neurons
AP on the presynaptic membrane that always gives rise to an AP on the postsynaptic membrane
Obligatory
A single AP on the presynaptic membrane is typically unable to induce an AP on the postsynaptic membrane
nonobligatory
EPSP causes
depolarization
IPSP causes
hyperploarization
Steps of synaptic transmission (5)
- a presynaptic AP arrives
- the presynaptic membrane lets vessicles with molecules of neurotransmitters pass through
- the vesicles release the neurotransmitters into the synaptic cleft
- the molecules diffuse across the cleft to the postsynaptic membrane and act at special sites (receptors)
- the postsynaptic membrane is either depolarized or hyperpolarized.
Electrical synapses are located b/w ______ and _____ cells in the brain
glial and schwann
what is the diff. b/w chemical and electrical synapses?
- chemical: use neurotransmitter so it is a little shower
- electrical: faster; less synaptic delay than chemical
________ summation occurs when several APs arrive at a presynaptic membrane at intervals that do not allow individual EPSP to disapprear
Temporal
______ summation occurs when several APs arrive SIMULTANEOUSLY synapses on the same presynaptic membrane so that their individual EPSPs sum up and can induce an AP
Spatial
Temporal and Spatial summation can only occur for EPSPs (Tor F)
False
Why is it important the temporal and spatial summation can occur for IPSPs?
can help with control; will increase the amount of inhibition.
