Lesson 3: Neuronal Communication Flashcards
Where do neurons communicate?
Synapses
What are synapses? (2)
Specialized junction between neurons
Allow for communication between neurons
_________________ travel from presynapatic to postsynaptic neuron
Neurotransmitters(NTs)
Synapses are either __________ or ________
Electrical
Chemical
List the following about Electrical Synapses:
Direction
Speed
Distance between pre- and postsynaptic cells
Signal travel method
Signal Type
Bidirectional Fast 3.5 nm Ions travel directly through gap junction channels Electrical signal (ion flow)
List the following about Chemical Synapses:
Direction
Speed
Distance between pre- and postsynaptic cells
Signal travel method
Signal Type
Unidirectional Slower than electrical 20 nm Ions diffuse to postsynaptic side Chemical signal (neurotransmitter)
What is the chemical signal for chemical synapses?
Neurotransmitters
What is the electrical signal for electrical synapses?
Ion flow
True or False:
Chemical synapses are faster than electrical synapses
False, chemical synapses are slower than electrical synapses
What is one common classification scheme for synapses?
Based on the neuronal structures involved
What are the types of synapses based on the neuronal structures involved? (3)
Axoaxonic
Axodendritic
Axosomatic
Chemical synapse consists of what? (2)
Presynaptic terminal
Postsynaptic terminal
What are neurotransmitters?
Chemical messengers which are released from the presynaptic terminal into the synaptic cleft
Neurotransmitters bind to receptors on the ____________ membrane
Postsynaptic
What are the criteria of neurotransmitter molecules? (3)
Must be synthesized and stored in the presynaptic neuron
Must be released by presynaptic neuron upon stimulation
When applied experimentally, must produce the same effect in the postsynaptic neuron as when it is released from the presynaptic neuron
What are the 3 categories of NTs?
Amino acid NTs
Monoamine NTs
Peptide NTs
List the characteristics of amino acid and monoamine NTs (2)
Small molecules
Produced, stored and released from synaptic vesicles
True or False:
Amino acid NTs are large molecules
False, amino acid and monoamine NTs are small molecules
Where are amino acid and monoamine NTs produced?
Synaptic vesicles
List the characteristics of peptide NTs (3)
Large molecules
Stored and released from secretory granules
Produced in cell body
Where are amino acid and monoamine NTs stored and released?
Synaptic vesicles
Where are peptide NTs stored and released?
Secretory granules
Where are peptide NTs produced?
Cell body
In Small Molecule Synthesis:
Small Molecule NTs are synthesized from _____ ____ precursors at the ________
Amino acid
Terminal
In Small Molecule Synthesis:
Small Molecule NTs are transported in ________ locally
Vesicles
In Neuropeptide Synthesis:
Precursor _______ synthesized on _____ __
Peptide
Rough ER
In Neuropeptide Synthesis:
Precursor protein split in ____ to form active _______
Golgi
Protein
In Neuropeptide Synthesis:
Secretory vesicles with _______ bud off of _____
Peptide
Golgi
In Neuropeptide Synthesis:
Secretory ________ transported to ____ ________
Granules
Axon terminal
What is the presynaptic mechanism of neurotransmitter release? (5)
Vesicles docked at the membrane ready to release NTs
Action potential depolarizes the membrane
Calcium channels on the terminal open
Influx in calcium triggers vesicle fusion to membrane
NTs are released in the synaptic cleft
Proteins on membrane and vesicle form a _____ _______ to “dock” vesicles at the presynaptic terminal
SNARE complex
What destabilizes interactions within SNARE complex?
Calcium influx
What happens when calcium influx occurs?
Vesicle membrane and cell membrane fuse, releasing NTs into the synaptic cleft
What are the postsynaptic mechanisms of neurotransmitter release? (3)
NTs diffuse through the synaptic cleft
Bind to and activate receptors on the postsynaptic neurons
Postsynaptic neuron receptors can be __________ or ____________
Ionotropic (ion channels)
Metabotropic (GPCRs)
List the major amino acid NTs (3)
Gamma-aminobutyric acid (GABA)
Glutamate (Glu)
Glycine (Gly)
List the major amine NTs (6)
Acetylcholine (ACh) Dopamine (DA) Epinephrine Histamine Norepinephrine (NE) Serotonin (5-HT)
List the major peptide NTs (9)
Cholecystokinin (CCK) Dynorphin Enkephalins (Enk) N-acetylaspartylglutamate (NAAG) Neuropeptide Y Somatostatin Substance P Thyrotropin-releasing hormone Vasoactive intestinal polypeptide (VIP)
List:
Type and function of acetylcholine (3)
Amine NT
Controls muscle contraction
Acts at neuromuscular junction
List:
Type and function of norepinephrine (3)
Amine NT
Response to novel stimuli
Sympathetic response
List:
Type and function of dopamine (2)
Amine NT
Reward and motivation
List:
Type and function of serotonin (2)
Amine NT
Appetite and mood
List:
Type and function of glutamate (3)
Amino acid NT
Major excitatory NT
Excites postsynaptic neuron
List:
Type and function of GABA (3)
Amino acid NT
Major inhibitory NT in CNS
Inhibits postsynaptic neuron
List:
Type and function of glycine (2)
Amino acid NT
Major inhibitory NT in PNS
List:
Type and function of neuropeptide Y (2)
Peptide NT
Contributes to appetite, nociception, and cognition
What is the most abundant peptide in the nervous system?
Neuropeptide Y
List:
Type and function of substance P (2)
Peptide NT
Transmits information regarding pain
List:
Type and function of vasoactive intestinal peptide (VIP) (2)
Peptide NT
Regulates blood and muscle activity in gastrointestinal tract
There are _ types of NT receptors, what are they?
2
Ionotropic (ion channels)
Metabotropic (GPCRs)
In Ionotropic Receptors:
Ion channels open and close upon ______ binding
Ligand
In Ionotropic Receptors:
Flow of ____ alters ________ _________
Ions
Membrane potential
True or False:
Ionotropic receptors are fast acting transmission
True
What determines opening duration of the gates linked with ionotropic receptors? (2)
Kinetics of receptor
Gating of receptor
What determines the magnitude of effect in ionotropic receptors?
Conductance
What determines which ions enter under ionotropic receptors?
Selectivity of channels
Define:
Metabotropic Receptors
Type of membrane receptor in eukaryotic cells that acts through a second messenger
In Metabotropic Receptors:
Most commonly functions in ____(_) pathways and activates _ ________
GPCR (G-Protein Coupled Receptor)
G Proteins
True or False:
Metabotropic receptors can stimulate the opening of ion channels in the cell membrane
False, metabotropic receptors can stimulate or inhibit the opening of ion channels in the cell membrane
In G Protein Coupled Receptors:
______ binds to receptor
Ligand
In G Protein Coupled Receptors:
Receptor activation causes a ______________ change in _-_______, and it splits
Conformational
G-Protein
In G Protein Coupled Receptors:
Subunits bind to and activate ________ proteins
Effector
In G Protein Coupled Receptors:
________ messengers are activated and __________ targets are altered
Chemical
Downstream
True or False:
G Protein Coupled Receptors have slow, but strong effects
True, these effects come via amplification
What is an example of GPCR signalling? List the process (7)
Epinephrine binds to receptor
Activates G-protein
Activates effector protein (adenylyl cyclase)
Production of second messenger (cAMP)
Activation of kinase (PKA)
Phosphorylation of target proteins (e.g. transcription factors)
Modification of gene expression
List the differences between metabotropic vs. ionotropic receptors (3)
Metabotropic
(Ionotropic)
Slow acting (Fast acting) Signal indirectly through second messengers (Signal directly through ion channels) Signal amplification (No signal amplification)
What are the 3 methods for neurotransmitter clearance?
Reuptake
Degradation
Diffusion
Define: Neurotransmitter clearance (reuptake)
When NTs are taken back to the axon terminal via reuptake-pumps or glial cells
In reuptake:
Reabsorbed NTs are ______ for another ________________
Reused
Neurotransmission
In reuptake:
Glial cells like __________ may reuptake NTs and use for ______ or send back to the ____ ________
Astrocytes
Itself
Axon terminal
When NTS are taken back in reuptake, what are they taken up through? (2)
Reuptake-pumps or glial cells
Define: Neurotransmitter clearance (degradation)
When NTs are broken down by enzymes at the synaptic cleft
True or False:
Broken down components can’t stimulate the neurotransmitter receptor
True
Define: Neurotransmitter clearance (diffusion)
When NTs scatter across the synaptic cleft
When can diffusion for neurotransmitter clearance occur?
Can only occur during low action potential firing
True or False:
Diffusion is enough to clear NTs for high action potential firing
False, diffusion won’t be enough to clear NTs for high action potential firing (NTs build up in synaptic cleft)
Ion flow in the postsynaptic cell changes membrane potential resulting in a ____________ _________
Postsynaptic potential
True or False:
Postsynaptic potentials can be excitatory
False, postsynaptic potentials can be excitatory OR inhibitory
What does excitatory postsynaptic potentials do?
Brings the membrane closer to threshold
What does inhibitory postsynaptic potentials do?
Brings the membrane away from the threshold
In Synaptic Integration:
_____ can sum up in a variety of ways to lead to generation of an _______ _________
EPSPs
Action potential
Define:
Spatial summation
The addition of many EPSPs generated simultaneously at many sites
Define:
Temporal summation
The addition of EPSPs generated in rapid succession
What is the addition of many EPSPs generated simultaneously at many sites called?
Spatial summation
What is the addition of EPSPs generated in rapid succession known as?
Temporal summation
When are electrical synapses formed?
Formed when the cytoplasm of two cells is linked by connexin channels
What are three characteristics of electrical synapses?
Bidirectional
Rapid
Always excitable
Where are electrical synapses often studied?
In the crayfish nervous system
In Electrical Synapses in Crayfish:
Postsynaptic signals occur how long after the generation of a presynaptic potential?
Occur within a fraction of a millisecond
In Electrical Synapses in Crayfish:
Minimal _____ allows for expedient transmission and ______ in crayfish
Delay
Escape
True or False:
Electrical synapses allow for quick motor responses in crayfish
True
True or False:
Electrical synapses play a major role in synchronization of neuronal activity
True
In Role of Electrical Synapses:
During development, electrical synapses provide a ________ for development of _________ networks
Framework
Neuronal
In Role of Electrical Synapses:
___ ________ _____ also allow entrance of molecules important for intracellular signaling
Gap junction pores
What is the presynaptic active zone?
Specialized electron dense region of the presynaptic plasma membrane
What is the presynaptic active zone composed of?
Network of proteins in opposing location to postsynaptic density
What is the network of proteins in the presynaptic active zone responsible for?
Docking and priming of synaptic vesicles
In Molecular Architecture:
Active zone is composed of _ main evolutionary proteins
5
What is are the 5 main evolutionary conserved proteins in the active zone?
ELKS RIM RIM-BP Munc13 α-Liprins
State the function of ELKS
The core
State the function of RIM & RIM-BP
Recruiting Ca2+ channels
State the function of Munc13
Mediating vesicular fusion
State the function of α-Liprins
Providing further binding interactions
What is the role of the active zone? (2)
Acceleration of vesicular release
Structural remodelling during synaptic plasticity & implication in memory formation
In the role of active zone:
Neuronal communication is divided into ______ or ______ transmission
Wiring
Volume
In the role of active zone:
The presence of active zone is a determinant of the mode of _____________ between _______
Communication
Neurons
List the differences between wiring transmission and volume transmission (4)
Wiring
(Volume)
Fast
(Slow, diffuse)
Precise
Energy demanding
(Less energy demanding)
Requires active zone
(Doesn’t require active zone)
In the role of active zone:
____-____ ________ __________ is the induced change in ________ and ________ of synaptic transission
Long-term synaptic plasticity
Strength
Efficacy
List the changes at the presynapse during positive enhancement (2)
Enlargement and remodelling of active zone proteins
Increased stability
List the changes at the postsynapse (1)
Increase of receptor conductance
In Structural Plasticity of the Active Zone:
Local neuronal activity dynamically controls ______ ____ organization through _____ dynamics to modulate presynaptic _________ and ________
Active zone
Actin
Structure
Function
True or False:
Active zone matrix is polymerized
False, active zone matrix is polymerized or depolymerized depending on the level of neuronal activity leading to changes of clustering
In Liquid Active Zone:
Clustering of ____ channels at ___________ active zones is critical for precise control of ________________ release
Ca2+
Presynaptic
Neurotransmitter
In Liquid Active Zone:
Active zone scaffold proteins ___ and ___-__ form self-assembled condensates capable of clustering _______-_____ ____ channels on lipid membrane bilayers
RIM
RIM-BP
Voltage-Gated Ca2+
Describe:
Calyx of Held (2)
Neuronal terminal in the auditory system containing hundreds to thousand of active zones
Largest synapse in human body
Describe: Neuromuscular junction (2)
Fixed number of active zones
Ensuring the motor outputs to be performed upon arrival of every action potential
What controls vesicle docking?
Rab proteins
____ Complexes assemble at docked ________
______ pore forms and releases ________________
Fusion
Vesicles
Fusion
Neurotransmitter
Define:
V-SNARE
Vesicle SNARE
Refers to proteins located on the vesicle itself
Define:
T-SNARE
Target SNARE
Refers to proteins located on the synaptic membrane
What are components of SNARE complexes? (4)
Syntaxin-1
SNAP-25
Synaptobrevin
Munc-18
What controls calcium binding at docked vesicles?
Synaptotagmin
What regulate SNARE complex disassembly?
NSF Complexes
