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64 Cards in this Set

  • Front
  • Back
Golgi technique
only stains nerve cells
What did Cajal(and Ramon) show?
that neurons are distinct entities
how are signals carried from neuron to neuron?
electrical- APs

electrical to electrical
how does current move?
down path of least resistance
EC space has least amount of resistance
concluded that communication was biochemical
-katz said it first
End Plate
myelinated motor neuron axon that LOSES ITS MYELINATION as it contacts the mucle cell
how many nerves innervate a single muscle cell?

however, one nerve can branch and innervate many mucles. but each muscle cell gets 1 nerve
what are the terminal ends of axons called?

make up pre-synaptic membrane
Post synaptic membrane called
Junctional Folds

help w/ NTs diffusing quickly away from site of action
Active Zone
on presynaptic side
has lots of vessicles and lots of Ca channels

density of Ach Rec?
on post-syn side

10,000/micrometer sq
How is the synapse optimized?

pre and post-syn membrane are very close together
-tons of rec in jxnl fold
Synapse has a high Safety Factor
not probablistic
signal will activate muscle
from poison dart frogs
only affects muscle fibers
blocks post-syn jxn
how long do post-syn responses last?
a few milliseconds
in both PNS and CNS
decay in synaptic transmission is due to?
membrane time constant
fxn of res and capacitance
snake venom
blocks nicotinic ach receptors in the NMJ
how are Ach rec gated?
ligand binds and opens activation gate, ions move in based on conc gradients
how do Ligand gated channels inactivate
Desensitization- NOT same as voltage gated inactivation mech
with channels, what is most impt in movement?
relative permeability

mostly Na, K, and some Ca
driving force at RMP

driving force at 0mv

driving force at +voltage
Na will have greated driving force
driving forces for Na/K are balanced
K will have greater driving force
when is there reversal in driving forces?

what does this mean?
reversal at 0mv

proves that the channel is permeable to more than one ion
at RMP what is the current like
largely an inward Na current
ideal fxn of NMJ
respond rapidly, precisely, and with high fidelity

rapidly on order of milliseconds

*Ach Rec does this*
Process of synaptic trans
1. vesicle fuses w/ membrane
-diffusion into cleft (ms)
2. 2 molec of Ach bind to rec
-10us to open
3. get rid of Ach by diffusion or degradation (AchE)
Law of Mass Action
a reaction will proceed as proportional to reactants

ie- high conc of Ach and Rec=fast reacion
Ach is close to a full agonist

receptor affinity?
99% of rec will be simultaneously opened

Ach has low affinity for rec
do Ach normally desensitize?
NO. Ach is removed too quickly.

Ach would have to be bound for 10s of ms for desensitization

AchE inhib can do this(ie myesthenia)

Time Dependent
Active/Regenerative Propogation
via Na channels
evokes an End Plate Potential(EPP) and can carry on
Far away from synapse
lose synaptic response
Synaptic Responses

what do regenerative processes require?
will decay

voltage gated channels
Smallest Evoked EPP
=spontaneous mEPP
Unitary Response

Synaptic Event is made up of what?
the smallest response possible of neuron vessicle release

multiple unitary responses
Quantal Content

Quantal Size
The number of vessicles released per stimulation
the amplitude of the individual response
How do yo affect quantal size?
dec the density of rec on post-syn membrane

or dec Na conduction
Docking and Priming
when vessicles are moved to the active zone

lots of protein interactions
what allows the presynaptic membrane to remain the same size?
recycling of vessicles
calcium channels are where?
on plasma membrane

necessary for docking, fusion, and transmitter release
what senses intracellular calcium
protein on vessicle, will lead to fusion
Necessary but not sufficient for vessicle release

Timing is impt. Ca has to be there when you stimulate axon

depolarization of membrane opens ca channels
which is faster: Ca or Na channels

what is the rate limiting step?
Na chan are much faster. Ca chann do not open synchronously

Calcium chan openings
have to have high ca conc to trigger rel of NT
Low affinity is important for what?
high efficiency

ca-synaptotagmin and Ach-Rec are very low affinity
What is vessicle fustion tightly timed to?
the period when Ca conc is HIGH
spatial relationship of Ca channels to vessicles
they are very close to one another.
micro domains of ca channels near Vessicles
Ribbon Synapses
post synaptic channels and Ca channels
Myasthenia Gravis
autoimmune to NMJ ach rec

use AchE inhibitors
why doesnt diffusion work at NMJ
its too big. would take too long

have to use AchE-ensures rapid termination
inhibiting AchE
makes the synaptic response 4-5xs longer


big, fast synaptic jxn. Always gets an AP and contraction

(only fast trans in auditory corex) CNS neurons have multiple synapses. Localized
Localization of Synapses in CNS
axosomatic- inhibitory
somadendritic- proximally, GABA
axodendridic- mostly excitatory*
Axoaxonic- allow regulation, cross talk
-presynaptic inhibition
Main excitatory NT
synapses at dendritic spines
Olfactory Bulb has what type of synapses/excitation?
reciprocal excitation of dendrities via Dendrodendritic
what determines the AP in the CNS
Dendritic Integration
excitatory synapses occur where?
dendritic spines (mostly Glu)

each dendritic spine is a fraction of an endplate. fraction of NMJ
do same principles apply to dendritic zone as NMJ?
yes. the only difference is that there are a fraction of the active zones

takes multiple synapses from then to fire an AP
CNS cells must be able to do what?
listen to dfft sources (dendritic synapses) to fire 1 AP
Inhibitory ligand CNS synapses

Exciatory ligand CNS synapses
inhibitory ligand chan use CL-
-GABA or Gly
use Na and K
-Ach, Glu, Serotogenic
Inhibitory response does what

Excitatory (Ach/Glu) do what?
reverses MP to Equilib potential for Cl- (-60mV) near RMP

reverse to around 0mV
Shunting Inhibition
when cl- channels open and cl pours in, it counteracts the mvmt of cations and holds the membrane at RMP

via GABA chan, Cl- will shunt out any activation
excitation input near dendrites
EPP is for NMJ, but same for EPSP
GABA and Gly use what
CL- channels to keep membrane near RMP. prevent excitation

are inhibitory
Temporal Summation
closely occuring synaptic repsonses dont decay-->they sum up

dependent on Time Constant

spatial summation kind of does the same thing
Terminating a Signal in the CNS
diffusion is usually enough

Too much Glu is bad. Astrycytes suck it up out of synapses
-Glu to Gln, then shuttle back
Reuptake mechanisms in the CNS
are mainly used to prevent neurotoxicity

NOT the primary removal mech
Diffusion is MAIN one