communication Flashcards
what is similar property between neurons and muscle cells
Excitable cells
High metabolic rate of neurons and muscle cells is due to
Processes to maintain the resting membrane potential
and
Synaptic transmission across the synapse between nerve cells or nerve to muscl
RMP maintained by what process
selective permeability to some ions
and
a ‘costly’ protein pump backup (Na+ - K+ pump)
Ion concentrations across a cell
differ outside to inside cell, because of a selectively permeable membrane:
the cell membrane is permeable to what and impermeable to what
Permeable to K+
Impermeable to Na+, and large anions (Cl-)
hat happened when you lose RMP
you cannot send any messages
RMP of a neuron
Neuron: -70mV inside
RMP of a muscle cell
muscle cell: -90mV inside
Increase in RMP is called what
hyperpolarization - more negative
what do we see with hyperpolarization
lesslikely to generate impulse
Inhibition
decrease in RMP is called what
depolarization - less negative
what do we see with depolarization
more likelyto send an impulse
excitation
three types of gated channels
Chemically-gated
Voltage-gated
mechanically gated
types of Chemically-gated
Ligand-gated
neurotransmitter
Voltage-gate - meaning and important for
change membrane potential open the gates (axon impulse coming down)
Important for generation of action potentials
what does it mean to be Mechanical gating
Sensory receptors, responding to mechanical forces such as touch, pressure
Local (graded) potentials property
generated and then decline with time and distance
Types of Local (graded) potentials
Receptor potentials (RP)
Synaptic potentials (SP)
Secretory potentials (ScP)
Receptor potentials (RP) are where
Generated at peripheral receptor of a sensory neuron
Synaptic potentials (SP)
Generated at a postsynaptic membrane
Secretory potentials (ScP)
Generated in the axon terminal [presynaptic membrane]
what are Action potentials (AP)
Depolarizing signal that is propagated down the axon
local potential V. AP amplitude
local- small, graded
AP- large, all-or-none
local potential V. AP effect on membrane
local- depolar or hyper
AP- depolar
local potential V. AP propagation
local- passive
AP- active and passive
local potential V. AP ion channels
local- end receptor modality gated channel and postsynaptic ligand gated
AP- voltage gated channels
Amplitude RP =
frequency
Duration RP =
duration of a train of APs
Resting neuron AP gates
activation gate closed; inactivation gate open
Activation neuron AP gates
activation gate opens, Na+ rushes in
Inactivation neuron AP gates
inactivation gate slow to close
Return toresting:activation gate closure; gradual inactivation gatereopening; depends on restoring resting membrane potential
Basis for AP - channels
voltage-gated Na+ and K+ channels
AP is summation of what
a number Na+channels activated
Refractory periods
inactivated due to resting state
Absolute
Relative
Accommodation
increase in threshold inresponse to a slowly rising stimulus
Inactivation of Na+ and activation of K+channels
how are AP regenerated down the axon
Internal currents result in regeneration of the AP at areas of high concentration of Na+ channels
Enhancing rate of
AP conduction
Increase diameterof the axon
Insulate with myelin sheaths
Speed of conduction is called
nerve conductionvelocity (NCV)
what is CMAP
relates to the sum of the events of allactivated nerve fibers
Nerve fiber sizes classified
A, B, C
characteristic of A delta and C fibers
small fibers
properties of Aalpha
the axons of motor nerves to musclesare the largest
over all C-fibers are
small, slow, and takes a lot to activate them
overall A-fibers are
large fibers and easy to conduct
At thesynapse what kind of gate do we see
chemically-gated channels
Synaptic potential (SP): exit or inhibitory
both: Excitatory (EPSP), Inhibitory (IPSP)
Generated at a postsynaptic membrane
Central synapses
forms the connections between different neurons in the central nervous system (CNS)
Neuron-neuron, requires manyEPSP or IPSP to trigger AP or inhibit;
what makes up the NMJ: neuro muscular junction
motor axon and its target muscle
ratio of AP in the NMJ
1NAP to 1MAP
AP at the NMJ excite or inhibitory
excite only
Postsynaptic cell response to NT is a
synaptic potential
synaptic potential local or AP
local potential
Stopping the postsynapticresponse
Degradation of NT in cleft
Reuptake of NT by presynapticmembrane
Diffuse away from synapse (e.g.glial: – eat excess NT- NT sink)
Presynaptic release of NT influenced by
secretory potential
[Ca++] entering terminal produces what
EPSPproduced (at NMJ in muscle fiber, or atcentral synapses EPSP or IPSP)
central synapsesexcitatory or inhibitory
both - unlike the NMJ
types of central synapses
Asymmetric - Gray Type I
Symmetric - Gray Type II
Asymmetric - Gray Type I properties
Excitatory
Symmetric - Gray Type II properties
Inhibitory
Axodendritic connection
axon to dendrite
less axosomaticinfluence onAPgeneration at the trigger zone
Less of a roll because it is further away
excitatory orinhibitory
Axosomatic connection
axon to soma
usually inhibitory
Have a greater influence on the generate of AP – because they are closer
This shows the inhibition is important in the NS - closer therefore important role
Axoaxonic
axon to axon
influencesNTrelease
Presynapticinhibitory and facilitatorymechanisms influence what
the release of NT
Postsynapticinhibitory and facilitatory mechanisms influence what
the postsynapticcell ability to generate an AP at the trigger zone.
Ionotropic
Receptor DIRECTLY controls ion flux
Rapid response
Metabatropic
‘Biochemical cascade’ – 2nd messengers
INDIRECT gating
Uses ‘second messengers’
Slower response; amplifiedmessage
repeated or regular routine of synapse activation leads towhat changes in the synapse
changes that enables more efficient activationin future.
Cellular and molecular basis oflearningand memory
what is LTP
a long-lasting strengthening of the synapse that occurs with repeated stimulation and is thought to be related to learning and long-term memory
Glutamate properties as a neurotransmitter
a major excitatory transmitter of CNS
what NT does NMDA accept
Glutamate
NMDA gate type
voltage and chemically gated
NMDA receptor type
ionotropicandmetabatropicreceptor
Ca++ entry activates 2ndmessenger system
what is NMDA blocked by
Mg++
what flows through NMDA
Ca++, Na+, K+
NMDA receptor a mechanism for what kind of potential
long-term potentiation (LTP)
