Synaptic Transmission

Under what conditions are peptide neurotransmitters generally released from the synaptic terminal?

-only with high-frequency trains of action potentials

Which of the following is FALSE? -Many toxins used to study signaling come from nature -Antagonists block the actions of neurotransmitters -Black widow venom increases acetylcholine release -Curare is an agonist

-Curare is an agonist

Which of the flowing is FALSE regarding neurotransmitter release? -Every action potential always releases a large number of synaptic vesicles -Some synaptic vesicles are docked -Vesicle membranes are recycled by endocytosis -Exocytosis occurs rapidly

-Every action potential always releases a large number of synaptic vesicles

Which of the following is FALSE? -Astrocytes can modulate neuronal signaling over a wide area -An action potential at a CNS synapse can lead to the release of one or a few synaptic vesicles -The number of channels that open depends on quantity of neurotransmitter released -All of the responses are true

-ALL responses TRUE

Endorphins are: -Amino acid transmitters -Peptide transmitters -Amine transmitters -Lipid transmitters

-Peptide transmitters

What is the function of a gap junction between neurons?

-electrical synapse between the neurons

Neurotransmitters are removed form the synaptic cleft by: -Reuptake -Diffusion -Degradation -Two of the responses -All of the responses

ALL responses

Which of the following is correct regarding the synapse? -Active zones are present on the presynaptic neuron -The cleft is not empty, but contains multiple proteins -The cleft is approximately 20-50 nm in width -Two of the above -All of the above

All of the above

Which of the following statements is FALSE? -An axon can form multiple active zones when synapsing on a target neuron -Astrocytes are often found in close proximity to synapses -Synapses can be formed between dendrites -All of these statements are TRUE

All of these statements are TRUE

EPSPs are produced when ion channels allowing anion entry are opened. -True -False

FALSE

If the postsynaptic cell is an interneuron that uses GABA as a neurotransmitter, the excitation of the cell will result in an action potential in its synaptic targets. True or false?

FALSE

Peptide neurotransmitters are released faster than amine or amino acid neurotransmitters -True -False

FALSE

Proteins can move between cells through gap junctions. -True -False

FALSE

The effectiveness of an excitatory synapse in triggering an action potential depends on how near the synapse is to the spike-initiation zone and the properties of the dendritic membranes. True or false?

FALSE

What are second messengers?

Molecules that activate additional enzymes in the cytosol

Dense core vesicles contain peptide neurotransmitters. -True -False

TRUE

T/F: Some neurons can make multiple neurotransmitters.

TRUE

The amplitude of a cell's EPSP is a sum of the miniamplitudes produced by each individual channel. -True -False

TRUE

Voltage-gated calcium channels are often concentrated at synaptic terminals: -True -False

TRUE

When EPSPs add up due to rapid firing of an input axon this is called: -Spatial summation -Quantal summation -Temporal summation -Shunting inhibition

Temporal Summation

Which types of neurotransmitters are loaded into vesicles?

amines and amino acids

Opening of the chloride channel allows Cl- ions to cross the membrane, bringing the membrane potential toward the ________________ equilibrium potential, Ecl About -65mV. If the membrane potential was less negative than -65mV when the transmitter was released, the activation of these channels would cause a _____________ IPSP.

chloride; hyperpolarizing

A dendrite with these properties would have the lowest length constant: -High membrane resistance and low internal resistance -Low membrane resistance and high internal resistance -High membrane resistance and high internal resistance -Low membrane resistance and low internal resistance

low membrane resistance and high internal resistance

Which types of neurotransmitters are loaded into secretory granules?

peptides

Acetylcholine is a(n): -Amino acid transmitter -Peptide transmitter -Amine transmitter -Lipid transmitter

-Amine transmitter

Which of the following is FALSE regarding transmitter-gated channels? -Channels open rapidly upon binding of the neurotransmitter -They are not as selective as voltage-gated channels -Excitatory channels allow Cl- entry -Channel is usually closed until the neurotransmitter is bound

-Excitatory channels allow Cl- entry

Which neurotransmitters are made primarily by the neurons that release them?

-GABA and amines -these neurons contain specific enzymes that synthesize the neurotransmitters from various metabolic precursors -the synthesizing enzymes are transported to the axon terminal, where they locally and rapidly direct transmitter synthesis

Which of the following statements is FALSE? -Two different neurotransmitters don't bind to the same receptor -Each neurotransmitter can bind to different subtypes -Nicotinic acetylcholine receptors are G protein linked -Agonists and antagonists can be used to classify receptor subtypes

-Nicotinic acetylcholine receptors are G protein linked

Which of the following is FALSE regarding neuromuscular junction synapses? -Small and thus easy to manipulate experimentally -Fast, reliable synapses -Similar to CNS synapses -All are TRUE

-Small and thus easy to manipulate experimentally

What are transporters? What is their role?

-Special proteins embedded in the vesicle membrane; responsible for concentrating neurotransmitters inside the vesicle

Quantal analysis shows that a single action potential at the neuromuscular junction causes an EPSP of 40 mV or more, compared to only a few tenths of a millivolt at many CNS synapses. What accounts for this difference?

-a larger number of synaptic vesicles releasing neurotransmitter molecules within the synaptic vesicles of a motor neuron compared with CNS synapses

What is the effect of activating G-protein coupled neurotransmitter receptors>

-activate effector proteins such as ion channels or those that synthesize second messengers

Which of the following is FALSE? -All neurotransmitters are released quickly at the synapse -Synaptic vesicle membranes are recycled by endocytosis -Some synaptic vesicles are docked before an action potential arrives -v-SNARES and t-SNARES are both involved in docking and synaptic vesicle release

-all neurotransmitters are released quickly at the synapse

Grays Type II synapses: -Are usually inhibitory -Are usually excitatory -Are asymmetrical -More than one of the above

-are usually inhibitory

Why are NMJ such reliable synapses?

-because the axon terminal is large and the presynaptic terminal contains a large number of active zones

Organophosphates:

-block AChase= the breakdown of ACh so this results in over-stimulation and paralysis ex= nerve gas and some insecticides

Botulinum toxin:

-blocks transmitter release -ACh

Some neurons make multiple neurotransmitters that: -Are released from the same vesicle -Are contained in different vesicles which are released upon different levels of stimulation -Both responses -None of the responses

-both responses

How do nerve gases interfere with synaptic transmission at the neuromuscular junction?

-by inhibiting the enzyme AChE

Removing calcium from the synapse would eliminate neurotransmitter release because: -Calcium is required to bind to vSNAREs and initiate vesicle fusion -Calcium is required to bind to tSNAREs and initiate vesicle fusion -It would block action potentials in presynaptic neuron -It would have no effect on vesicle release

-calcium is required to bind to vSNAREs and initiate vesicle fusion

Which of the following statements is FALSE? -Symmetrical synapses are usually inhibitory -Synapses exist in various sizes -Astrocytes are close to many synapses -Chemical synapses are bidirectional

-chemicals synapses are bidirectional

Which of the following is FALSE about length constants? -Depends on internal resistance and membrane resistance -Does not depend on number of ion channels open -Quantifies how currents dissipate as they move down a dendrite -Not the same value for all dendrites

-does not depend on number of ion channels open

Gap Junction

-electrical synapse between two membrane at this site -interconnect many cells including non-neural cells -allows ions to pass directly from the cytoplasm of one cell to the cytoplasm of the other -bidirectional -very fast transmission -occur in areas of the brain that requires neighboring neurons to be highly synchronized

Understand the differences between electrical and chemical synapses

-electrical synapses are very small and interconnect two membrane where as chemical synapses are a space in between two neurons

How are released neurotransmitters cleared from the synaptic cleft?

-enzymatic destruction and diffusion

Which neurotransmitters are synthesized/ found in practically all cells of the body?

-glutamate and glycine -amino acids that form building blocks of proteins so they are abundant

A dendrite with what properties would have the highest length constant? -High membrane resistance and low internal resistance -Low membrane resistance and high internal resistance -High membrane resistance and high internal resistance -Low membrane resistance and low internal resistance

-high membrane resistance and low internal resistance

Exocytosis

-how the vesicles release their contents (NT) -the membrane of the synaptic vesicle fuses . to presynaptic membrane causing the NTs to spill into the synapse

Black widow venom:

-increases ACh release

Fast forms of synaptic transmission

-last from about 10-100msec -at most CNS synapses are mediated by amino acids= glutamate, GABA, or glycine -Acetylcholine mediates fast synaptic transmission at NMJ

Grays Type I synapses: -Are usually inhibitory -Are usually excitatory -Are asymmetrical -More than one of the above

-more than one above -excitatory, asymmetrical

Synthesizing a peptide neurotransmitter. How? Where?

-peptides are formed when amino acids are strung together by ribosomes of the cell body (RER) and Golgi splits them -one of the smaller peptide fragments is the active NT -this is carried to the axon via axoplasmic transport

neuromuscular junction

-point of contact between a motor neuron and a skeletal muscle cell -transmission is fast and reliable -one of the largest synapses in the body

Lack of removal of neurotransmitters from the synaptic cleft can lead to: -Receptor desensitization -Receptor degradation -Increased neurotransmitter release -None of the responses

-receptor desensitzation

What is the other name for dense-core vesicles?

-secretory granules

Which of the following is FALSE regarding the NMJ? -Signaling is slow, but are reliable synapses -Easier to study than CNS synapses -Large number of acetylcholine receptors are present on the muscle -Are between motor neurons and muscle cells

-signaling is slow, but are reliable synapses

Connexon

-the gap junction channels that connect the two cells -made up of smaller proteins (6) called connexin

Which of the following is FALSE regarding electrical synapses? -They consist of unique connections called gap junctions -They are common in glial cells -They are considered evolutionarily old (present in many primitive species) -They are unidirectional

-they are unidirectional

What is the difference between vSNARES and tSNARES?

-vSNARES= specific vesicle SNARES; calcium interacts with this snare and synaptic vesicle fusion and release occurs rapidly by exocytosis -tSNARES= transport SNARES located on membrane of presynaptic terminus

Which of the following channels in the active zones of the synaptic terminal open when the membrane depolarizes and causes the release of synaptic vesicles?

-voltage gated calcium channels

T/F: presynaptic autoreceptors are often ligand gated.

FALSE -often G-protein-linked receptors and give feedback to the neuron releasing the neurotransmitter