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The process by which neurons communicate with each other through electrical and chemical signaling at specialized junctions called synapses. Involves the release, diffusion, and binding of neurotransmitters to receptors.
Synaptic Transmission
Jan Swammerdam's frog neuromuscular preparation to Luigi Galvani's discovery of the action potential in the late 1700s led to the ____________________.
Discovery of Synaptic Transmission
The hypothesis about the function of the nervous system in the early 1700s, centered around the idea of ________ advocated by Galen and originating from the Ancient Greeks.
Animal Spirits
_________________’s idea in the early 1700s was that nerve signals have an electrical nature, thus describing the concept of electric bodies and the role of electricity in nerve signal transmission.
Isaac Newton
Italian doctor and professor of anatomy who helped discover the action potential using frog neuromuscular junction. He published a commentary on electricity's effects on muscular motion in 1791 and is thus considered a pioneer of electrical signaling in the nervous system.
Luigi Galvani
The development of ________ in the 1600s and 1700s by scientists like Van Leeuwenhoek, Odierna, and Hook, leading to the identification and description of neurons and nervous tissue by anatomists like Valentin, Ehrenberg, Purkinje, and Remak.
Microscopy
___________ and __________, who used a stain to visualize cells in the nervous system, with ________ proposing the reticular theory and ___________ proposing the neuron doctrine and the concept of synapses.
Golgi; Cajal; Golgi; Cajal
The concept proposed by Santiago Ramon y Cajal that cells in the brain are separate entities communicating at specific junctions called synapses, in contrast to Golgi's reticular theory suggesting physical connections between cells.
Neuron Doctrine
The region between neurons or between a neuron and its target cell where transmission occurs, involving both electrical and chemical signaling, identified as the primary site of communication in the nervous system.
Synapse
A type of synaptic transmission where there is direct flow of current between the presynaptic axon and the postsynaptic neuron through gap junctions, allowing for rapid communication without the use of neurotransmitters. Allows direct flow of ions between pre- and post-synaptic regions through connexons, enabling fast communication but lacks adaptability.
Electrical Synapse
A type of synaptic transmission where neurotransmitters are released from the presynaptic axon into the synaptic cleft, bind to specific receptors on the postsynaptic membrane, and induce responses in the target cell, which can be excitatory, inhibitory, or modulatory.
Chemical Synapse
Large channel or pore-like complexes formed between the plasma membrane of the presynaptic axon and the postsynaptic cell in electrical synapses, allowing for the direct movement of small molecules, including ions, between the cells.
Gap Junctions
Channels composed of connexin proteins located on the presynaptic and postsynaptic membranes in electrical synapses, allowing for the flow of ions and small molecules directly across the gap junction channels.
Connexons
A type of neurotransmission where neurotransmitters are released into the synaptic cleft but can diffuse outside into the extracellular fluid, affecting multiple neurons or dendritic spines in the surrounding area, leading to coordinated responses in a volume around the release site.
Volume Transmission
Astrocytes help compartmentalize synaptic transmission by producing extracellular proteins that form barriers to neurotransmitter diffusion, ensuring specificity in wiring transmission.
Astrocyte function at the synapse
Inhibitory synapses, excitatory synapses, and modulatory synapses are functional types named based on the response in the postsynaptic cell, with the presynaptic axon always communicating and using action potentials.
Types of synapses in the central nervous system
Spine synapses on dendritic spines are predominantly excitatory using glutamate, while shaft synapses on dendritic shafts can be excitatory, inhibitory, or modulatory, with GABA as the main inhibitory neurotransmitter.
Morphological types of CNS synapses
A type of synapse where a presynaptic axon forms functional synapses with multiple target dendritic spines along its path, contributing to synaptic transmission and information integration within neurons. The axon continues past the synapse to form connections with multiple downstream targets.
En passant synapse
The synaptic cleft is closer than depicted, with cell adhesion molecules spanning the pre and postsynaptic membranes, forming homotypic or heterotypic interactions that stabilize synaptic connections and enable communication beyond synaptic transmission.
Synaptic cleft and cell adhesion molecules
Role of cell adhesion molecules in autism
Mutations in neurexins and neuroligins, involved in forming synaptic connections, were the first genetic mutations identified in individuals with autism, highlighting the importance of these proteins in synaptic function and communication.
Involves the presynaptic neuron, postsynaptic neuron, and astrocyte, emphasizing the role of astrocytes in determining synaptic transmission as point-to-point or volume transmission.
Tripartite synapse
Long-term potentiation leads to changes in dendritic spines, receptor numbers, and synaptic responses, contributing to _________ crucial for learning and memory in both developmental and adult brains.
Synaptic plasticity
The first identified neurotransmitter, discovered by Dr. Otto Loewi, involved in mediating synaptic transmission.
Acetylcholine
A parasympathetic nerve originating in the brain stem, involved in regulating heart rate and contraction force.
Vagus Nerve
Proteins on the postsynaptic membrane that NTs bind to, leading to changes in membrane potential or the production of second messengers.
Neurotransmitter Receptors
Neurotransmitters with low molecular weight, synthesized in presynaptic terminus, stored in synaptic vesicles, and can produce rapid or slow effects. Consists of small proteins, synthesized in the cell body, transported to presynaptic terminus in dense core granules, and produce neuromodulatory effects. Categorized into amines, amino acids, and purines based on their molecular structure.
Small Molecule Neurotransmitters
Larger neurotransmitters that are released further away from active zones, diffusing into extracellular fluid without specific uptake or degradative mechanisms.
Neuropeptide Neurotransmitters
Hydrophobic molecules like endocannabinoids and small molecule gases (e.g., nitric oxide) that are not stored in vesicles, can diffuse across membranes, and are usually neuromodulatory.
Unconventional Neurotransmitters
Structures that store neurotransmitters before their release, with _________ (smaller, clear) storing small molecule neurotransmitters and _______ (larger, dense core) storing neuropeptides.
Synaptic vesicles; Secretory vesicles
Small molecule transmitters with amino groups, including acetylcholine and biogenic amines like dopamine and serotonin.
Amines
Larger precursors of neurotransmitters cleaved by proteases, synthesized in the cell soma, and released from secretory vesicles.
Neuropeptides
Transported by vesicular neurotransmitter transporters using a proton gradient. Generated from synaptic endosomes, containing neurotransmitters and released at the presynaptic terminus for synaptic transmission.
Synaptic vesicles
Concept of neurotransmitter release in discrete units within synaptic vesicles, with 3,000-9,000 molecules per vesicle. When an action potential reaches the presynaptic terminal, it triggers the release of synaptic vesicles, leading to the release of neurotransmitter into the synaptic cleft. Each synaptic vesicle releases its neurotransmitter content in a quantal fashion, ensuring that the amount of neurotransmitter released at each vesicle fusion event is consistent This phenomenon allows for precise and reliable synaptic transmission between neurons.
Quantal release
Electrical signal triggering neurotransmitter release by activating VGCCs in the presynaptic region. A rapid change in the membrane potential of a neuron, involving depolarization and repolarization, essential for transmitting signals. The electrical signal that requires activation of voltage-gated Na+ and K+ channels, conducted along the axon causing depolarization of the presynaptic membrane.
Action potential
Synaptic connection where the axon terminates at the postsynaptic target.
Terminal synapse
Channels activated by depolarization, leading to calcium influx and triggering neurotransmitter release in the presynaptic neuron. Transmembrane proteins in the presynaptic neuron that open in response to depolarization, allowing calcium influx and neurotransmitter release. Contains an Alpha subunit with 12 transmembrane spanning domains, S4 regions, and auxiliary subunits for localization. Also detect presynaptic action potentials and convert them into a release of neurotransmitters through calcium-dependent exocytosis. Channels composed of 24 transmembrane domains, activated by depolarization to about -45 to -40 mV, allowing Ca2+ influx triggering exocytosis of synaptic vesicles.
VGCCs
A divalent cation that acts as a messenger molecule and plays a crucial role in synaptic transmission by triggering neurotransmitter release.
Calcium Ion
N-type and P/Q-type channels in presynaptic region for neurotransmitter release, L and T-type channels in muscle cells and dendrites with different functions.
Calcium influx and neurotransmitter release
Proton ATPase pumps protons, vesicular neurotransmitter transporter fills vesicles, synaptotagmin senses calcium, V-SNARE and synaptophysin aid in fusion.
Synaptic vesicle proteins
Resting pool, recycling pool, and readily releasable pool connected metabolically for efficient neurotransmitter release.
Synaptic vesicle pools
_______ binds calcium, induces conformational change, and communicates with the ________ complex for vesicle fusion and exocytosis.
Synaptotagmin; SNARE
Docking of vesicle, priming through SNARE complex formation, calcium influx leading to vesicle fusion, exocytosis, and neurotransmitter release into synaptic cleft.
Neurotransmitter release process
A rapid fusion process where synaptic vesicles fuse with the presynaptic membrane quickly, allowing for rapid endocytosis and recycling of neurotransmitters.
Ultrafast Fusion
The process by which cells absorb molecules by engulfing them with their cell membrane, crucial for recycling synaptic vesicles and maintaining presynaptic membrane integrity. Process where the membrane is retrieved after exocytosis, allowing for recycling of synaptic vesicle proteins and lipids, and refilling with NT.
Endocytosis
Regions within the presynaptic neuron where voltage-gated calcium channels are localized, leading to high calcium concentrations and neurotransmitter release.
Calcium Microdomains
A key feature where VGCCs do not inactivate, allowing for faithful transduction of action potential frequency into presynaptic calcium levels and neurotransmitter release.
Prolonged opening of Calcium Channels
Mechanisms such as degradation and transporters that remove neurotransmitters from the synaptic cleft, crucial for terminating synaptic transmission.
Neurotransmitter Removal
The process of retrieving and recycling synaptic vesicle proteins after neurotransmitter release, involving endocytosis and refilling with neurotransmitters for reuse.
Synaptic Vesicle Recycling
Proposed by Camillo Golgi, suggests that cells in the nervous system form a continuous network allowing unimpeded electrical signal flow.
Reticular Theory
Involves conversion of electrical signals to chemical information via neurotransmitter release, offering adaptability and varied responses.
Chemical Synapse
Point-to-point neurotransmission localized at synapses, either through electrical responses (EPSPs, IPSPs) or volume transmission.
Wiring Transmission
Three functional types of synapses based on their effects; anatomical types include axo-dendritic, axo-somatic, and axo-axonic synapses.
Excitatory, Inhibitory, Modulatory Synapses
Molecules crucial for synaptic formation, maturation, and plasticity, enhancing trans-cellular communication at synapses.
Synaptic Adhesion Proteins
Process in which synapses are strengthened, weakened, or removed in an activity-dependent manner, crucial for learning and memory.
Synaptic Refinement
Small molecule and neuropeptide _________, including acetylcholine, monoamines, amino acids, and purines, crucial for synaptic communication.
Neurotransmitters
Divalent cation crucial for neurotransmitter release, regulated by pumps and exchangers to maintain low intracellular levels and prevent cell death.
Ca2+ Regulation
Caused by presynaptic Ca2+ increase, mediated by synaptotagmin binding to Ca2+ and SNARE complex formation, leading to NT release into the synaptic cleft.
Synaptic Vesicle Fusion
Mechanisms to keep intracellular Ca2+ levels low after influx through VG Ca2+ channels, involving pumping out, binding to proteins, and sequestration into organelles.
Presynaptic Ca2+ Regulation
Encoding of information in AP frequency, pattern, and number, decoded by VG Ca2+ channels to determine presynaptic Ca2+ signal and NT release.
Neural Coding
Small molecule NTs released by low frequency APs near active zones, while neuropeptide NTs require high frequency APs for release further away.
NT Release Regulation
Mechanisms including diffusion, degradation by proteases, and uptake into neurons and astrocytes by transporters to ensure short-lived and specific neuronal responses.
NT Removal
The discovery of synapses and synapses transmission involved and required the discovery or development of ____.
All of these answers
Tissue dyes/stains
Muscle contraction in response to electrical stimulation
The microscope and cell
Electricity
All of these answers
An electrical synapse requires _______.
Neurotransmitter release
Postsynaptic neurotransmitter receptors
Presynaptic voltage gated Na+, K+ and Ca2+ channels
Synaptic vesicles
Direct contact between the presynaptic and postsynaptic membranes
Direct contact between the presynaptic and postsynaptic membranes
A chemical synapse requires ____.
Release of neurotransmitter into the synaptic cleft or extracellular fluid
Direct contact between the presynaptic and postsynaptic membranes
Flow of current through GAP junction channels
Formation of a postsynaptic action potential
Synthesis of neurotransmitter in the synaptic cleft
Release of neurotransmitter into the synaptic cleft or extracellular fluid
Synapses can occur between a presynaptic neuron and ___.
A cardiac muscle cell
Another neuron
All of these answers
A neurosecretory (gland) cell
A smooth or skeletal muscle cell
All of these answers
Compared to electrical synapses, chemical synapses _____.
All of these answers
Are more abundant
Are more adaptable
Require more steps
Are slower
All of these answers
In ______ transmission, neurotransmitter can diffuse out of the synapse and activate nearby spines or neurons.
Diffuse
Point to point
Volume
Endocrine
Wiring
Volume
Which of the following BEST DESCRIBES typical synapses in the CNS?
The postsynaptic region of the synapse forms on dendrites but not other regions of the neuron
The presynaptic region of the synapse can be an axon or a dendrite
A synapse can include an oligodendrocyte which forms part of the tripartite synapse
Synapses can contain cell adhesion molecules and extracellular matrix proteins
In en passant synapses the axon ends on its target
Synapses can contain cell adhesion molecules and extracellular matrix proteins
Since axons can branch and form en passant synapses, this ensures that a neuron can communicate ____.
In volume and wiring transmission
With skeletal muscle and organs in the periphery
In both the CNS and PNS
Through chemical and electrical synaptic transmission
With multiple target neurons and at multiple synapses
With multiple target neurons and at multiple synapses
Acetylcholine was the first neurotransmitter identified through its release by the ______ and effects in the ______.
Autonomic ganglion, smooth muscle
Sympathetic nerve, aorta
Vagus nerve, heart
Brainstem, parasympathetic nervous system
Motor neurons, skeletal muscle
Vagus nerve, heart
The three categories of small molecule neurotransmitters are the _____, _________, ________.
Amines, Amino Acids, and Purines
Small molecule neurotransmitters are synthesized in the ____ and packaged into ____.
Presynaptic region, synaptic vesicles
Presynaptic region, secretory vesicles
Cell body/soma, secretory vesicles
Cell body/soma, synaptic vesicles
All of these answers
Presynaptic region, synaptic vesicles
Vesicles are filled with small molecule neurotransmitters (NTs) by _____.
The H+ (proton) ATPase pump
NT channels
Translocation in the RER
Endocytosis of NTs
Vesicular NT transporters
Vesicular NT transporters
Which of the following BEST DESCRIBES synaptic vesicles (SVs)?
SVs contain the v SNARE and t SNARE proteins
SVs contain the Ca2+ sensor called syntaxin
SVs contain both small molecule and neuropeptide neurotransmitters
SVs contain ion channels and ion transporters
SVs contain the proton/H+ ATPase and neurotransmitter transporters
SVs contain the proton/H+ ATPase and neurotransmitter transporters
Neuropeptides are synthesized in the ____ and packaged into ____.
Cell body/soma, synaptic vesicles
Presynaptic region, secretory vesicles
All of these answers
Presynaptic region, synaptic vesicles
Cell body/soma, secretory vesicles
Cell body/soma, secretory vesicles
Conventional NTs include both small molecule NTs and neuropeptide NTs.
True
False
True
Small molecule neurotransmitters and neuropeptides differ in their___.
All of these answers
Localization and release site in the presynaptic region
Molecular mass
Site of synthesis in the neuron
Requirements for release from the presynaptic neuron
All of these answers
In general, it has been shown that each neuron synthesizes and releases _____, though there are some exceptions to this.
One type of amine, one type of amino acid AND one type of neuropeptide NT
One small molecule NT AND one neuropeptide NT
One small molecule NT OR one neuropeptide NT
All types of NTs packaged into different vesicles
Many types of NTs that are co-packaged into synaptic vesicles
One small molecule NT AND one neuropeptide NT
Which of the following BEST DESCRIBES Ca2+ in neurons?
Ca2+ is involved in conduction of the action potential at the presynaptic region
Intracellular Ca2+ levels are controlled primarily by secondary active transporters on the plasma membrane
Low intracellular levels of Ca2+ can lead to apoptosis, a type of cell death
The Ca2+ concentration ratio (outside/inside) is ~ 10 at rest
Ca2+ is neither synthesized nor degraded so its concentration is controlled by its localization
Ca2+ is neither synthesized nor degraded so its concentration is controlled by its localization
Which of the following BEST DESCRIBES VGCCs? VGCCs _____.
All of these answers
Are required to increase the intracellular Ca2+ levels that stimulate NT release
Contain four S4 voltage sensor transmembrane domains
Are localized to the active zone
Are activated by the depolarization produced by the action potential
All of these answers
Which of the following BEST DESCRIBES the release of small molecule NT? It involves ______.
Diffusion of NT through GAP junction channels
Activation of VGCCs located on synaptic vesicles
Plasma membrane NT transporters which are located at the active zone
Formation of the SNARE complex between v-SNARES and t-SNARES
Endocytosis of synaptic vesicles at the active zone
Formation of the SNARE complex between v-SNARES and t-SNARES
What determines how much neurotransmitter is released by a presynaptic neuron?
All of these answers
The pattern of APs in the AP train
The frequency of APs in the AP train
How many VGCCs are opened and for how long
The number of action potentials (length of the AP train)
All of these answers
After fusion of a synaptic vesicle with the presynaptic plasma membrane, the synaptic vesicle membrane is retrieved by the process of ______.
Synopsis
Synaptocytosis
Phagocytosis
Exocytosis
Endocytosis
Endocytosis
Which of the following IS NOT a mechanism that may be involved in removing NTs or decreasing NT levels at the synaptic cleft?
Endocytosis
Uptake by plasma membrane NT transporters
Diffusion
Degradation
Endocytosis
Endosomal trafficking in the presynaptic region is DIRECTLY required for____.
Retrieval of exocytosed synaptic vesicle membrane and generation of new synaptic vesicles
Degradation of the NT at the cleft
All of these answers
Removal of NT from the cleft
Exocytosis and release NT at the cleft
Retrieval of exocytosed synaptic vesicle membrane and generation of new synaptic vesicles
In the early to mid-1800s, scientists including Jan Purkinje used _____ to further the understanding of the nervous system.
Photography
All of these answers
Electrophysiology
Microscopy
Biochemistry
Microscopy
In the the late 19th and early 20th century, the major argument between those who favored the neuron doctrine (Cajal) or reticular theory (Golgi) is whether communication involves______.
Chemical or electrical synapses
Chemical or electrical signaling
Neurotransmitters or neuropeptides
Continuous physical connections or gaps between neuronal processes
Action potentials and graded potentials
Continuous physical connections or gaps between neuronal processes
The debate between the soups and sparks was about whether ______.
Reactions in the primordial soup were stimulated by sparks
Axonal conduction involve chemical or electrical changes
Synaptic potentials involve the movement of ions or electrons
Neurons evolved once or twice during evolution
Synaptic transmission involves chemical or electrical signals
Synaptic transmission involves chemical or electrical signals
Who was correct about the debate above?
Both the soups and the sparks
The soups
The sparks
Neither the soups nor the sparks
Both the soups and the sparks
In the majority of neurons, the presynaptic region is typically an axon. Which types of neurons communicate by synaptic transmission but don't have an axon?
Some neurons in ganglia in the PNS
Some motor neurons
All of these answers
Some neurons in nuclei in the CNS
Some sensory receptor cells
Some sensory receptor cells
The secretory pathway can impact synaptic transmission because ____are generated in the secretory pathway.
Neuropeptides
Plasma membrane proteins and lipids
Dense core vesicles and secretory granules
Synaptic vesicle precursors
All of these answers
All of these answers
Synaptic plasticity, which involves the formation. strengthening, weakening and pruning of synapses, can occur _____.
In several neuronal circuits of the CNS
In the adult brain
During development
As a mechanism in memory
All of these answers
All of these answers
It has been proposed that the molecular mechanism(s) that decodes the neural code is/are _____.
All of these answers
The activation of VGCCs
The conduction of the action potential
The formation of synaptic vesicles
The inactivation of VGNa+Cs
The activation of VGCCs
A neuron is often described by the __________.
All of these answers
Neurons that communicate with it
Neurons it communicates with
Small molecule and neuropeptide NTs it releases
Types of synaptic inputs it receives
Small molecule and neuropeptide NTs it releases
At an electrical synapse, there is ________.
Opening of gap junction channels by neurotransmitter binding
Neurotransmitter diffusion through GAP junction channels
Direct movement of current through GAP junction channels
All of these answers
Exocytosis of synaptic vesicles containing GAP junction channels
Direct movement of current through GAP junction channels
At a chemical synapse, the presynaptic action potential ________.
Usually leads to release of neurotransmitter into the synaptic cleft or extracellular fluid
Usually produces an action potential in the postsynaptic cell
Is usually produced by a Na+ current which diffuses directly into the postsynaptic neuron producing an EPSP
All of these answers
Usually activates the opening of GAP junction channels which increase Ca2+ levels and stimulate the SNARE complex
Usually leads to release of neurotransmitter into the synaptic cleft or extracellular fluid
Which of the following is NOT TRUE about synapses in the CNS? They can ________.
Contain cell adhesion molecules and extracellular matrix proteins
Occur on dendrites, dendritic spines, the cell body/soma or axon
Include an astrocyte which forms the tripartite synapse
Be terminal synapses or en passant synapses
Involve an oligodendrocyte which myelinates the synapse
Involve an oligodendrocyte which myelinates the synapse
Which of the following is NOT TRUE about chemical synapses? Chemical synapses __________.
Are more abundant than electrical synapses
Are more adaptable than electrical synapses since they involve neurotransmitters and receptors
Involve more biochemical steps than electrical synapses do
Produce slower synaptic transmission than electrical synapses do
Involve point-to-point transmission but electrical synapses do not
Involve point-to-point transmission but electrical synapses do not
You discovered a new synapse which by electron microscopy contains a 30 nm gap, but two regions where the presynaptic and postsynaptic membranes are so closely apposed that no gap is visible. It contains numerous 40 nm vesicles on the presynaptic region and a postsynaptic density. You suspect this is ________.
An electrical only synapse
A neuromodulatory synapse
A chemical only synapse
A mixed electrical and chemical synapse
A dendro-dendritic synapse
A mixed electrical and chemical synapse
In the early to mid-1800s, scientists including Jan Purkinje used _____ to further the understanding of the nervous system.
Photography
All of these answers
Biochemistry
Electrophysiology
Microscopy
Microscopy