Synapse/Transmission + Neuroplasticity (5 -6)

What are the three types of synapses?

axosomatic, axodendritic, axoaxonic

axosomatic synapse

axon terminal connects directly to the cell body (soma) of another neuron.

axodendritic synapse

axon terminal → dendrite

axoaxonic

axon terminal → another axon

active chemical synapse

event 1

active chemical synapse

event 2

active chemical synapse

event 3

active chemical synapse

event 4

active chemical synapse

event 5

active chemical synapse

event 6

When AP arives at presynaptic terminal, neurotransmitterr vesicles connect with

docking protein

When neurotransmitter vesicles connect w/ docking proteins, the presynaptic terminal

membrane depolarizes

The presynaptic mem depolarizies and opens ________.

Ca2+ voltage-gated channels

What does Ca 2+ bind to?

docking protein

Vesicles fuse with ________ and release neurotransmitter into _______.

the membrane ; the cleft

Neurotransmitter diffuses across the

the synaptic cleft

Neurotransmitter binds to

postsynaptic membrane receptor

Membrane channel changes

shape and ions enter postsynaptic cell

What are neurotansmitters removed by on the presynaptic terminal?

reuptake transporters

_______ in the synaptic cleft can degrade neurotransmitters.

enzymes

Neurotransmitters can diffuse ____ of the synapse.

out

What can cause receptor inactivation?

Phosphorylation or other post-translational mods of mem receptors

_______ can be internalized.

membrane receptos

During presynaptic facilitation, _____ neurotransmitter is released

more

_____________ occurs when presynaptic axon neurotransmitter slightly depolarizes axon terminal of a second neuron

presynaptic facilitation

During presynaptic inhibition, _____ neurotransmitter is released

less

____________ occurs when neurotransmitter that slightly hyperpolarizes axonal region of a second neuron

Presynaptic inhibition

__________ are local changes in ion concentration across the postsynaptic membrane

Postsynaptic potentials

At the postsynaptic membrane, changes in the membrane potential are either

excitatory or inhibitory

Local depolarization is an ___________; Local hyperpolarization is an __________.

excitatory postsynaptic potential (EPSP); inhibitory postsynaptic potential (IPSP)

Summation of Postsynaptic Potentials

The process by which multiple postsynaptic potentials combine to produce a larger change in membrane potential, determining whether an action potential is triggered.

synaptic receptors can produce direct (________) or indirect (_________) actions

fast synaptic transmission; slow synaptic transmission

Which synaptic receptor action involves when the receptor and ion channel make up a single functional unit?

direct

Which synaptic receptor action involves using a cascade of intracellular molecules to activate ion channels or cause other changes within the postsynaptic neuron?

indirect

______________ are chemicals in presynaptic terminal that are released into the synaptic cleft to transmit information between neurons

Neurotransmitters

____________ are chemicals released into the extracellular fluid at a distance from the synaptic cleft.

Neuromodulators

Neuromodulators effects manifest

more slowly and usually act longer than effects at the synapse

Neurotrasmitters are _______ and _________.

local; specific

Neurotransmitters affects the postsynaptic neuron: directly, by

activating ion channels

Neurotransmitters affects the postsynaptic neuron indirectly by

activating proteins inside the postsynaptic neuron

What are the two types of neurotransmitters?

fast-acting and slow-acting

Fast-acting NT:

those that act directly (transmission requires less than 1/1000 of a second)

Slow-acting NT:

act indirectly (Transmission requires 1/10 of a second to minutes)

Neuromodulators have ___________.

more general release and impact (slower and longer effect)

Neuromodulators alter neural function by acting

at a distance away from synaptic cleft

How long can a neuromodulators last?

minutes to days

_____________ are drugs that bind to the receptor and mimic the effects of naturally occurring neurotransmitters/modulators

Agonist

___________ are drugs that prevent. the release of neurotransmitters/modulators or bind to the receptor and impede the effects of a naturally occurring transmitter/modulator.

Antagonists

Signaling between efferent nerve terminals and muscle cells can be disrupted by

disease

Lambert-Eaton syndrome

Antibodies destroy voltage-gated Ca2+ channels in the presynaptic terminal

Myasthenia gravis

antibodies (autoimmune) attack and destroy nicotinic receptors on muscle cells

Channelopathies

Diseases that involves dysfunction of ion channels

In some cases which pathology may cause epilepsy and migraines?

channelopathies

Neuroplasticity is the ability of

neurons to change their function, chemical profile, or structure

Neuronal structure involves

# synapses, dendrite branching, shape of postsynaptic membrane

Chemical profile involves

quantity and types of neurotransmitters

Functional/structural reorganization involves

one area substituting function for another area

The ability to reorganize neurons by forming new neural connections throughout life allows the brain to

respond to injury or new situations

Neuroplasticity is a general term used to encompass 3 chief mechanisms:

Habituation

Experience-dependent plasticity

Cellular recovery after injury

Habituation is a

temporary decrease in response to a repeated benign sensory stimulus

Habituation is a decrease and environmental decrease in the release and availability of _______ and ________.

excitatory neurotransmitters (e.g., glutamate)

free intracellular Ca2+

With prolonged repetition of stimulation, more permanent structural changes such as

DEC # of synapses / INC threshold for nts needed

Tactile defensiveness is abnormal sensitivity to touch so therapy includes

slowly introducing gentle stim / progressing to brisk stim

Therapy involving unilateral vestibular hypofunction consist of

practicing the movements that induce dizziness and nausea

Experience-Dependent Plasticity are complex processes involving

persistent, long-lasting changes

(in synapse strength/neural networks)

Learning =

Acquisition of knowledge or ability

Memory

Retention and storage of that knowledge or ability

__________ reflects the process we acquire knowledge; ___________ reflects the product of learning

learning; memory

Experience-Dependent Plasticity requires all of the following except

Growth of old synapses

Sleep is important for

motor learning consolidation

During initial stages of motor learning, large areas of the brain show

synaptic activity

As the task is repeated and learned, there is

a reduction in active brain regions.

Persistent, long-lasting changes of synaptic connections leads to

learning and new memory

What are two specific mechanisms involved in Experience-Dependent Plasticity?

LTP & LTD

LTP & LTD results in presynaptic changes in

neurotransmitter release

LTP & LTD results in postsynaptic changes in

receptor density and efficiency

Long-term potentiation and long-term depression can occur

simultaneously within a neural network

Long-Term Potentiation is best defined/understood as a type of

neuroplasticity in learning and declarative memory formation

LTP is the cellular mechanism for the formation of memory in the

temporal lobe (hippocampal gyrus)

In LTP, __________ synapses are converted to _______synapses

silent; active

In LTP, an increase in synaptic activity and metabolic changes increase

the efficiency of nerve cell firing

LTP synapse density involves repetitive stimuli that cause

synthesis / activation of new proteins that promote or inhibit growth of new synaptic connections

The result of LTP is

a maintained response and memory of specific, repetitive stimuli

Long-Term Depression =

receptor site removal from post-synaptic membrane (dendritic spine pruning)

LTD is a conversion of an _______synapse to a ______ synapse

active; silent

Where is Transcranial Magnetic Stimulation (TMS) applied to?

the motor cortex or other brain areas involved in motor learning

Transcranial Magnetic Stimulation (TMS) Can enhance or inhibit motor learning and memory formation, depending on

the experimental protocol

Astrocytes play an important role in

brain and SC plasticity

Neurons release neurotransmitters → stim astrocytes to release

gliotransmitters

Gliotransmitters modulate

neuronal activity

Gliotransmitters support ________ by moodulating

synaptogenesis;

NTS release / upstake

Injuries that damage or sever axons cause

degeneration but may not result in cell death

Injury that destroys the cell body of a neuron leads to

cell death

Neurons deprived of oxygen for a prolonged period (stroke/injury) will

DIE + NO REGENERATION

Excitotoxicity (Glutamate (Astrocytes)) may

add more damage

What drug provides significant neuroprotection for individuals with stroke, TBI, or neurodegenerative disease?

none known

In a PNS axonal injury (ex. polio) cells

can recover.

deprives input from damaged axons/attracts new inputs to maintain function

In a CNS axonal injury (sci, cva) cells

Cannot recover in the same way; research ongoing

Sever an axon: Wallerian (anterograde) Degeneration

distal portion dies and breaks into segments; no connection to nucleus

engulfed by microglia

Sever an axon: Retrograde (proximal) Degeneration /Central Chromatolysis - all are true except

Solution of nuclear chromatin