communication Flashcards by VB VB

what is similar property between neurons and muscle cells

Excitable cells

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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

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RMP maintained by what process

selective permeability to some ions

and

a ‘costly’ protein pump backup (Na+ - K+ pump)

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Ion concentrations across a cell

differ outside to inside cell, because of a selectively permeable membrane:

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the cell membrane is permeable to what and impermeable to what

Permeable to K+

Impermeable to Na+, and large anions (Cl-)

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hat happened when you lose RMP

you cannot send any messages

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RMP of a neuron

Neuron: -70mV inside

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RMP of a muscle cell

muscle cell: -90mV inside

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Increase in RMP is called what

hyperpolarization - more negative

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what do we see with hyperpolarization

lesslikely to generate impulse
Inhibition

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decrease in RMP is called what

depolarization - less negative

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what do we see with depolarization

more likelyto send an impulse
excitation

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three types of gated channels

Chemically-gated
Voltage-gated
mechanically gated

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types of Chemically-gated

Ligand-gated
neurotransmitter

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Voltage-gate - meaning and important for

change membrane potential open the gates (axon impulse coming down)

Important for generation of action potentials

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what does it mean to be Mechanical gating

Sensory receptors, responding to mechanical forces such as touch, pressure

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Local (graded) potentials property

generated and then decline with time and distance

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Types of Local (graded) potentials

Receptor potentials (RP)
Synaptic potentials (SP)
Secretory potentials (ScP)

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Receptor potentials (RP) are where

Generated at peripheral receptor of a sensory neuron

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Synaptic potentials (SP)

Generated at a postsynaptic membrane

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Secretory potentials (ScP)

Generated in the axon terminal [presynaptic membrane]

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what are Action potentials (AP)

Depolarizing signal that is propagated down the axon

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local potential V. AP amplitude

local- small, graded

AP- large, all-or-none

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local potential V. AP effect on membrane

local- depolar or hyper

AP- depolar

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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 to resting: activation gate closure; gradual inactivation gate reopening; 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 in response 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 diameter of the axon Insulate with myelin sheaths

Speed of conduction is called

nerve conduction velocity (NCV)

what is CMAP

relates to the sum of the events of all activated nerve fibers

Nerve fiber sizes classified

A, B, C

characteristic of A delta and C fibers

small fibers

properties of A alpha

the axons of motor nerves to muscles are 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 the synapse 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 many EPSP 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 postsynaptic response

Degradation of NT in cleft Reuptake of NT by presynaptic membrane 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

EPSP produced (at NMJ in muscle fiber, or at central synapses EPSP or IPSP)

central synapses excitatory 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 axosomatic influence on AP generation at the trigger zone Less of a roll because it is further away excitatory or inhibitory

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 influences NT release

Presynaptic inhibitory and facilitatory mechanisms influence what

the release of NT

Postsynaptic inhibitory and facilitatory mechanisms influence what

the postsynaptic cell 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; amplified message

repeated or regular routine of synapse activation leads to what changes in the synapse

changes that enables more efficient activation in future. Cellular and molecular basis of learning and 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

ionotropic and metabatropic receptor Ca++ entry activates 2nd messenger 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)