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50 Cards in this Set

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What are Electrical synapses

Specialized modifications of the membrane between two adjacent cells that allow a direct transfer of small molecules.




Most common in Glial sections

What is a Jap junction

Electrical Synapse




Small regions closely apposed cell membranes containing channels.


-Permeable to ions and Small Metabolites.


-Short half life



Where are typical gap junctions found?

Astrocytes, oligodenrocytes, schwann cells, ependymal cells.

What do gap junctiosn participate in?

Control of capillary beds


Pathological conditions (cerebral edema)


Embryonic Development - Help to define synchronous division of cells

What does coupling allow for?

Very rapid transmission of information


Seen in neurons and gap junctions




Olfactory and Hypothalamus

What is Charcot-Marie-Tooth Disease

Mutation in the gene for gap junctions in schwann cells




Results in demyelination and slowing of conduction in peripheral axons, muscle weakness, atrophy, and sensory loss

What are Chemical Synapses

Use of a chemical substance to convey electrical activity and sometiems other information between neurons.

What is Transduction

Action Potential converted to a chemical signal




Slower, less reliable, more subject to toxins than electrical but allows a much more complex system of information processing

What are the three elements of Chemical synapses

Presynaptic elelment


Synaptic cleft


Postsynaptic element

How are chemical synapses named?

According to the source of the pre to postsynaptic element.




Ex. Axodendritic, Axosomatic

What are the steps of chemical transmission at the pre-synaptic bouton?

1. Synthesis-Secretory vesicle synthesis and loading with transmitter and thetransport to the synaptic terminal (synthesis and packaging)


2.Depolarization of the terminal by an action potential.


3. Openingof Ca++channels which triggers


4. The release of neurotransmitter into thesynaptic cleft.

What are the steps of chemical transmission at the post-synaptic bouton?

5.Neurotransmitter diffuses across the cleftand binds to and activates of apostsynaptic cell receptor (changes shape)


6.Transduction of the signal by the postsynaptic cell.


7.Pre and Post synaptic inactivation of neurotransmitter that can includereuptakeor degradation of the neurotransmitter (termination).

How are Large Neurotrasmitters synthesized?

Synthesied in the Golgi apparatus and transported via fast axoplasmic transport to the nerve terminal




Released but not recyled.

How are small neurotransmitters synthesized

Undergo extensive recycling and synthesis within the pre-synaptic terminal.




Sensitive to agents which can interfere with synthetic or recycling enzymes (Aceytlcholine)

Describe the Depol of the terminal

Loaded Synpatic vesicles


-Chemical synapse initiated by AP and depols the pre-terminal




This opens voltage channels for calcium in the pre-terminal

Effect of Ca increase on transmission?

Initiates vesicle release


Fusion of the vesicle membrane with active zone of pre-terminal


Release of neurotransmisster to synaptic cleft



Transmission and the synaptic cleft

After releasem NT diffuse across the synapticcleft and contract receptors on the post synaptic membrane.





Receptors and their reaction to NT will

Define the nature of the transduction in the post synaptic membrane

What is a typical transduction reponse

Opening of ion channels such as sodium to produce a depol of the post synaptic membrane.

Descibe NT Reuptake?

Mostneurotransmitters or their inactivated products are directly taken up bytransporter proteins on the presynaptic membrane, and on adjacent neuroglialcells

Describe Vesicle Recycling

Synaptic vesicle membrane is reincorporated into new synaptic vesicles.




Small molecule transmitters, vesicles are reloaded within the terminal reused

What is Enzmatic Inactivation

Molecule is destroyed or modified by membrane boundenzymesaround the synaptic cleft. May be in Pre or post membrane

What is Neuromodulation?

Release of NT directly into the extracellular space: Catecholamines and neuropeptides




Often in Periperies in relation to smooth vessels.

How are receptor activation classified?

–Ligated channels- open or close transmembrane pores or channels


–G-proteincoupled and other second messengerreceptors


–Transmembrane receptors with modifiableenzymatic activity


–Ligand -dependent regulators of nucleartranscription


–Sequestrationof intracellular ions (calcium in particular).

What is a NT receptor agonist?

Agents which mimic or enhance the mornal action o a NT either through action on cell receptors or other mechanisms

What is a NT receptor antagonist

Block the normal action of a NT by direct or indirect effects on the receptos

What is a Ionotropic Synapse?

includes small moleculesynapses, fast synapses, singlemessenger synapses.




Activate primarily ionotropicreceptors.




postsynapticmembrane opens an ion channel to depolarize or hyperpolarize the postsynapticmembraneotection:0

What is Metabotropic Synapse

includes larger neuropeptidesynapses, slow synapses, second messenger synapses.




Activate primarily metabotropicreceptors.




producea second messenger molecule that acts usually through a different mechanism toproduce signal transduction.

What to metabotropic receptos most often act through?

Guansoine nucleotide-binding protein: G-protein

Describe the G-Protein

can act as a second messenger itself in function such as the opening of ionchannels.




This process can generateeither stimulatory or inhibitory signals.

What is determined by number of active receptors on Post synaptic cells?

How effectively the cell can be stimulated.

How is Receptor regulation accomplished

Through metabotropic mechanisms and can include both activation and deactivation

What is Denervation supersesitivity

Neuron loses some of its afferents then increases the numbers of its receptors and becomes more sensitive to the NT involved

What is Glutamate

Most prevalent excitatory transmitter in the CNS.




Derived from a-ketoglutarate




Recycled by a direct transporter into presynaptic terminals for reuse and indirectly through astrocytes where it is degraded to glutamine and reconverted

Describe GABA

Primary inhibitory NT in the brain.

Synthesized by Glutamic Acid Decarboxylase

Describe Glycine

Inhibitory NT primarily in the brainstem and SC




Primarily associated with mechanisms of recurrent inhibition




Part off feedback inhibitory mechanism common to motor neuron pools to limit activity

Describe Acetylcholine

Importantneurotransmitter in both the central and peripheral nervous systems with bothexcitatory and inhibitory properties with both ionotropicand metabotropic receptors

Describe Catcholamines

Bothexcitatory and inhibitory. They are synthesized from tyrosine in successivesteps to create the neurotransmitters dopamine, norepinephrine, andepinephrine

Describe Serotonin

excitatory and inhibitory-synthesized from tryptophan