Neuronal Communication Basics (Neuroplasticity)

neuroglia

small cells that surround and wrap delicate neurons

neurons (nerve cells)

excitable cells that transmit electrical signals

Astrocytes (CNS)

support and from scars

Microglial cells (CNS)

become phagocytes

Ependymal cells (CNS)

ciliated cells lining CNS cavities; moves CSF

Oligodendrocytes (CNS)

form the myelin sheath that wraps around multiple axons in the brain and the spinal cord

Satellite cells (PNS)

support neuron cell bodies in ganglia; PNS equivalent of astrocytes

Schwann cells (PNS)

Form myelin sheath in the peripheral nerves; PNS equivalent of oligodendro's

1 Schwann cell wraps around what?

ONE portion of ONE axon

1 myelin sheath wraps around what?

MULTIPLE axons

where is the location of the nucleus?

neuron cell body

neuron cell body function

receives incoming signals

biosynthetic center

synthesizes proteins, membranes, neurotransmitters and other chemicals

the neuron cell bodies carry what

DNA

dendrites

receive signals from other neurons; primary receivers of info

hat is the importance of dendrites in surface area?

dendrites have greater surface area so the greater the capability of receiving synaptic info

axon

generates & transmits nerve impulses away from cell body; conductors/transmitters

axon hillock

where the axon starts; outgoing signals initiated here

the axon ends where?

terminal branches and axon terminals

axon terminals release what?

neurotransmitters

myelin function

Protects and electrically insulates axon. Increases speed of nerve impulse transmission.

increased myelin means leads to what?

increased action potential conduction

how do unmyelinated fibers conduct impulses?

more slowly

myelin-heavy regions of the CNS appear what color?

white

nodes of ranvier

gaps between Schwann cells that makes signals jump from one node to the next

what do the nodes of ranvier contain?

lots of ion channels in the axon membrane

where do neurons receive signals?

on dendrites

if a neural signal is strong enough what will the neuron do?

fire an action potential down its axon; it goes from axon hillock (beginning) to axon terminal (end)

neurons respond to what?

adequate stimulus by generating an action potential

what is an action potential?

a nerve impulse

when does an action potential remain the same?

as long as the stimulus is adequate (exceeds threshold)

what must occur in order to generate an action potential in a post-synaptic neuron?

multiple synaptic connections must be available (stimulus must be adequate enough/exceed threshold)

resting membrane potential definition

potential difference across the membrane of a resting cell

resting membrane potential

-70mV (polarized)

incoming signals can do what to a neuron?

excite a neuron or suppress/inhibit it

exciting or suppressing/inhibiting a neuron results in what?

results in membrane potential change RELATIVE to resting membrane potential

what is depolarization?

inside of membrane becomes less negative than resting membrane potential

deoplarization increases the probability of what?

producing (firing) a nerve impulse

what is hyperpolarization?

when inside of cell becomes more negative than resting membrane potential

hyper polarization reduced/decreases what?

probability of producing/firing a nerve impulse

presynaptic neuron

conducts impulses toward the synapse

postsynaptic neuron

receives a chemical signal from the presynaptic & transmits electrical signal way from synapse

what must the neurotransmitter cross?

the synaptic cleft

synaptic cleft

fluid-filled space between pre and post

chemical synapse

synapse specialized for release and reception of neurotransmitters

TRUE OR FALSE: electrical impulse gets changed to chemical across synapse and then back into electrical

TRUE

what is the 1st stage of communication across a chemical neuronal synapse?

axon potential arrives at axon terminal of presynaptic neuron

what is the 2nd stage of communication across a chemical neuronal synapse?

depolarization causes voltage-gated Ca2+ channels open & Ca2+ enter axon terminal

what is the 3rd stage of communication across a chemical neuronal synapse?

Ca2+ entry causes synaptic vesicles to release neurotransmitters by exocytosis

increased frequency of action potential leads to what?

increased release of neurotransmitters thus leading to increased stimuli to cross synaptic cleft

what is the 4th stage of communication across a chemical neuronal synapse?

neurotransmitter diffusion across synaptic cleft & binding to specific receptors on post-synaptic membrane

what is the 5th stage of communication across a chemical neuronal synapse?

binding of neurotransmitter opens ion channels, resulting in post-synaptic potentials

what is the 6th stage of communication across a chemical neuronal synapse?

neurotransmitter effects are terminated by reuptake through transport proteins, enzymatic degradation, or diffusion away from the synapse

what are the 3 diff ways to terminate neurotransmitters in synaptic terminal?

1. reuptake

2. diffusion away from synapse

3. enzymatic degradation

reuptake

neurotransmitters are sucked up back up by synaptic terminal & recycled for later use

enzymatic degradation

breaks up neurotransmitters

dendritic spines function

enhance strength & size of synapse

neurotransmitter receptors cause postsynaptic potential that vary in strength with what? (2)

1. amount of neurotransmitter released

2. time neurotransmitter stays in the area (extended length of stay minimizes reuptake, degradation, diffusion from synapse)

what are the 2 types of postsynaptic potentials?

EPSP (excitatory postsynaptic potentials) and IPSP (inhibitory postsynaptic potentials)

An EPSP is a local depolarization of the postsynaptic membrane that brings:

A. closer to AP threshold

B. further away from AP threshold

A. closer to AP threshold

when neurotransmitters binding opens chemically gated ion channels, what does it allow to pass through?

Na+

An IPSP is a hyperpolarization of the postsynaptic membrane that drives neuron:

A. toward AP threshold

B. away from AP threshold

B. away from AP threshold

means the cell becomes more negative

IPSP neurotransmitter binding opens what channels?

K+ or Cl- channels

what is synaptic integration summation rule?

a single EPSP cannot induce an action potential. it needs multiple & must reach a significant degree of threshold

EPSP can do what to influence postsynaptic neuron?

summate through increased frequency of EPSP

IPSP and EPSP both do what?

summate

most neurons receive what from thousands of other neurons?

both excitatory and inhibitory inputs

what is the only way an action potential will fire?

if EPSP predominate and reach threshold

temporal summation

One or more presynaptic neurons transmit impulses in rapid-fire order; closer together in time

spatial summation

Postsynaptic neuron stimulated simultaneously by large number of terminals on multiple dendrites at same time (signals arrive simultaneously from different dendrites)

strong stimulation can cause action potentials to do what?

occur more frequently (# of impulses per second of frequency of action potentials)

the stronger the stimulus the more what?

action potentials per second

how does the CNS determine stimulus intensity?

by the frequency of impulses - higher frequency means stronger stimulus i.e. jabbing needle into yourself

what is the relationship between stimulus strength & action potential frequency?

increased stimulus leads to increased frequency of action potentials

T/F: conduction velocity (speed) of neurons vary widely

TRUE

what does the rate of action potential propagation depend on?

1. axon diameter (wider axon = faster impulse conduction due to less resistance to local current flow)

2. degree of myelination (thicker myelin = faster conduction speed)

neurotransmitter defintion

an endogenous chemical related by a neuron that transmits a signal to another neuron, muscle or gland

what does endogenous mean?

made by a neuron & then released by a neuron

T/F: most neurons makes/produces two or more neurotransmitters (particularly within CNS)

TRUE

acetylcholine is released where?

at neuromuscular junctions by some ANS neurons & some CNS neurons

where is acetylcholine excitatory vs inhibitory

- excitatory at neuromuscular junction

- inhibitory in cardiac muscle

the same acetylcholine, can have different what?

receptors; receptor type determines effect of neurotransmitter on a post-synaptic neuron

what is a neuromuscular junction?

where alpha motor neuron reaches a muscle cell

what neurotransmitters are mostly excitatory in the nervous system?

dopamine, norepinephrine (NE), epinephrine, substance P

what neurotransmitters are mostly inhibitory?

serotonin, histamine, endorphins, adenosine

adenosine

neurotransmitter that caffeine works against

T/F: amino acids are split 50/50 between excitatory & inhibitory

TRUE

excitatory amino acids do what?

increase chances of activity within nervous system

what are the 2 types of excitatory amino acids?

1. glutamate

2. aspartate

glutamate can cause what?

excitotoxicity

excitotoxicty is the root cause of which disease?

ALS

what are the 2 types of inhibitory amino acids?

1. glycine

2. GABA

glycine, especially in the spinal cord, is blocked by what?

strychnine which causes convulsions

GABA, especially in the brain, is enhanced by what?

alcohol, benzos, and sedatives

excitatory vs inhibitory neurotransmitter summary

neurotransmitter effects can be excitatory (depolarizing) and/or inhibitory (hyperpolarizing)

- effects are determined by receptor to which it binds to

what type of neurotransmitter effect occurs when binded to GABA + glutamate?

inhibitory neurotransmitters

what type of neurotransmitter effect occurs when bonded to Glutamate?

excitatory neurotransmitter

what are the 7 things we can change to alter the neuronal communication/neural plasticity summary:

1. length of time NT stays in cleft

2. how much NT gets released

3. increase or decrease receptors released

4. decrease time difference of NT across post-synaptic cleft

5. increase inflow of calcium

6. change overall structure

7. insert more NT into post-synaptic membrane