Neuroscience Chapter: Synapses
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Questions and Answers

What distinguishes an electrical synapse from a chemical synapse?

  • It allows ions to flow freely between cells. (correct)
  • It relies on neurotransmitters for signal transmission.
  • It creates a synaptic cleft for communication.
  • It requires a physical gap for transmission.

Which type of synapse is formed between a neuron and a muscle cell?

  • Electrical synapse
  • Axoaxonic synapse
  • Axodendritic synapse
  • Neuromuscular junction (correct)

What is the primary feature of chemical synapses?

  • Direct connection between neuron membranes.
  • The existence of a synaptic cleft. (correct)
  • Stimulus transmission without chemical agents.
  • Presence of gap junctions.

What role do gap junctions play in electrical synapses?

<p>They allow rapid transmission of electrical signals. (C)</p> Signup and view all the answers

Which of the following most accurately describes the postsynaptic structure in a chemical synapse?

<p>Motor end plate. (D)</p> Signup and view all the answers

What type of synapse is characterized by synaptic transmission that can inhibit or excite postsynaptic neurons?

<p>Chemical synapses (B)</p> Signup and view all the answers

What causes the release of neurotransmitters in a chemical synapse?

<p>Calcium ions entering the presynaptic neuron. (A)</p> Signup and view all the answers

How far apart are the cells connected by gap junctions in electrical synapses?

<p>2-4 nanometers (A)</p> Signup and view all the answers

What is the mechanism of action of Botulinum toxin?

<p>It destroys SNARE proteins, preventing neurotransmitter release. (B)</p> Signup and view all the answers

Which conditions is Botulinum toxin NOT used to treat?

<p>Osteoporosis (A)</p> Signup and view all the answers

How can one become infected with botulinum toxin?

<p>Ingesting improperly canned foods (B)</p> Signup and view all the answers

What is the primary effect of Tetanus toxin?

<p>It blocks the release of inhibitory neurotransmitters. (B)</p> Signup and view all the answers

What autoimmune effect is observed in Lambert-Eaton Syndrome?

<p>Destruction of specific voltage-gated Ca2+ channels. (C)</p> Signup and view all the answers

What results from autoantibodies formed in Myasthenia Gravis?

<p>Accumulation of acetylcholine in the synaptic cleft. (A)</p> Signup and view all the answers

What is the primary function of acetylcholine in the central nervous system?

<p>Initiating muscle contractions (C)</p> Signup and view all the answers

Which of the following statements accurately describes electrical synapses?

<p>They have a narrow synaptic gap and no synaptic delay. (A)</p> Signup and view all the answers

What is a common source of botulinum spores that poses a risk to infants?

<p>Honey (A)</p> Signup and view all the answers

What are V-SNARE proteins primarily responsible for?

<p>Merging synaptic vesicles with the target membrane. (A)</p> Signup and view all the answers

What type of paralysis is associated with Tetanus toxin action?

<p>Spastic paralysis (C)</p> Signup and view all the answers

What type of synaptic delay is characteristic of chemical synapses?

<p>A significant delay before signal transmission. (B)</p> Signup and view all the answers

Which disease is linked to dysfunction at the neuromuscular junction due to antibody interference?

<p>Myasthenia Gravis (B)</p> Signup and view all the answers

What role does synaptotagmin play in the SNARE complex?

<p>It enhances the assembly upon calcium binding. (A)</p> Signup and view all the answers

Which characteristic differentiates chemical synapses from electrical synapses?

<p>Chemical synapses utilize neurotransmitters for transmission. (B)</p> Signup and view all the answers

How does botulinum toxin affect the nervous system?

<p>It blocks the release of neurotransmitters. (C)</p> Signup and view all the answers

What is the primary action of curare at the neuromuscular junction?

<p>Blocks acetylcholine receptors (B)</p> Signup and view all the answers

Which neurotransmitter is primarily responsible for producing excitatory post-synaptic potentials (EPSPs)?

<p>Glutamate (B)</p> Signup and view all the answers

How does an inhibitory post-synaptic potential (IPSP) affect the postsynaptic neuron?

<p>It hyperpolarizes the neuron. (B)</p> Signup and view all the answers

What does the term convergence refer to in neural signaling?

<p>Signals from multiple presynaptic neurons to one postsynaptic neuron. (D)</p> Signup and view all the answers

What outcome occurs when the summation of EPSPs is higher than that of IPSPs?

<p>The postsynaptic neuron is stimulated. (A)</p> Signup and view all the answers

Which of the following ions is involved in the hyperpolarization of the postsynaptic neuron during an IPSP?

<p>Potassium (K) (C)</p> Signup and view all the answers

What occurs when acetylcholine (Ach) accumulates in the synaptic cleft due to competitive blockade?

<p>Inhibition of respiratory muscles. (B)</p> Signup and view all the answers

What triggers the opening of voltage-gated Ca+2 channels in the presynaptic neuron?

<p>Depolarization of the presynaptic neuron (A)</p> Signup and view all the answers

Which type of potential results from the opening of sodium (Na) channels in the postsynaptic neuron?

<p>EPSP (D)</p> Signup and view all the answers

What happens after the fusion of the vesicle with the presynaptic membrane?

<p>Neurotransmitters are released into the synaptic cleft (D)</p> Signup and view all the answers

What type of receptor is the nicotinic Ach receptor (nAcHR)?

<p>Ligand-gated ion channel (D)</p> Signup and view all the answers

What determines the number of vesicles released into the synaptic cleft?

<p>Intracellular Ca+2 concentration in the presynaptic terminal (C)</p> Signup and view all the answers

What effect does the binding of Ach to nAcHR receptors have on the ion flow?

<p>Na+ enters the cell while K+ exits (A)</p> Signup and view all the answers

What is the result of the accumulation of excitatory postsynaptic potentials (EPP)?

<p>Opening of further voltage-gated Na+ channels (C)</p> Signup and view all the answers

Which neurotransmitter is the most common excitatory neurotransmitter in the CNS?

<p>Glutamate (A)</p> Signup and view all the answers

What is the role of GABA in the central nervous system?

<p>It has a calming effect on nerve cells (D)</p> Signup and view all the answers

Flashcards

Synapse

The junction between a neuron and another cell, allowing information transfer.

Presynaptic cell

The cell before the synapse, sending information.

Postsynaptic cell

The cell after the synapse, receiving information.

Neuromuscular junction

A synapse between a neuron and a muscle cell.

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Electrical synapse

Synapses that establish a direct connection between neurons, allowing ions to flow freely.

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Chemical synapse

Synapses that utilize chemical messengers to transfer information across a gap.

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Synaptic cleft

The space between the presynaptic and postsynaptic cells in a chemical synapse.

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Neurotransmitters

Chemical messengers released by the presynaptic neuron, acting on receptors in the postsynaptic cell.

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Acetylcholine

A neurotransmitter responsible for initiating muscle contractions and playing a role in learning and memory within the central nervous system (CNS). It is found in both the CNS and the peripheral nervous system (PNS).

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SNARE Proteins

Proteins that help fuse synaptic vesicles with the presynaptic membrane, releasing neurotransmitters into the synaptic cleft.

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V-SNARE

A SNARE protein located on the vesicle membrane.

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T-SNARE

A SNARE protein located on the target membrane.

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Botulinum Toxin

A neurotoxin produced by bacteria that inhibits the release of acetylcholine from synaptic vesicles, causing paralysis.

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Botulism

A condition caused by botulinum toxin, characterized by muscle weakness and paralysis.

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Synaptic Transmission: Presynaptic Events

The arrival of the action potential (AP) at the presynaptic terminal triggers a series of events leading to the release of neurotransmitters.

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Calcium Influx

Voltage-gated calcium channels open, allowing calcium ions (Ca2+) to rush into the presynaptic terminal.

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Exocytosis

Vesicles containing neurotransmitters fuse with the presynaptic membrane, releasing their contents into the synaptic cleft.

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Postsynaptic Receptor Binding

Neurotransmitters bind to specific receptors on the postsynaptic membrane, triggering a response in the postsynaptic neuron.

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Postsynaptic Potential (PSP)

A graded potential that occurs in the postsynaptic membrane after neurotransmitter binding.

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Excitatory Postsynaptic Potential (EPSP)

A type of postsynaptic potential that increases the likelihood of a postsynaptic action potential occurring.

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Inhibitory Postsynaptic Potential (IPSP)

A type of postsynaptic potential that decreases the likelihood of a postsynaptic action potential occurring.

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Glutamate

The most common excitatory neurotransmitter in the CNS, involved in functions such as learning and memory.

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Curare

A type of poison that acts at the neuromuscular junction, preventing muscle contraction by blocking acetylcholine receptors.

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Postsynaptic potentials

Transient electrical changes in the postsynaptic neuron caused by chemical signals transmitted from the presynaptic neuron. These changes can be either excitatory (EPSP) or inhibitory (IPSP).

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EPSP (Excitatory Postsynaptic Potential)

A type of postsynaptic potential that makes the postsynaptic neuron more likely to fire an action potential.

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IPSP (Inhibitory Postsynaptic Potential)

A type of postsynaptic potential that makes the postsynaptic neuron less likely to fire an action potential.

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Convergence

When many presynaptic neurons send signals to a single postsynaptic neuron.

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Divergence

When a single presynaptic neuron sends signals to multiple postsynaptic neurons.

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Synaptic Integration

The sum of all EPSPs and IPSPs at the postsynaptic neuron.

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Facilitation

The ability of repeated stimulation to strengthen the connection between neurons.

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How does Botulinum toxin work?

Botulinum toxin inhibits the release of acetylcholine, a neurotransmitter crucial for muscle contraction. It does this by targeting and disrupting the proteins involved in vesicle fusion, effectively preventing the release of acetylcholine from the presynaptic neuron.

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What is Botulinum toxin and where is it found?

Botulinum toxin, produced by the bacterium Clostridium botulinum, can be found in soil, water, and some food products. It thrives in oxygen-free environments and produces toxins. This toxin can lead to botulism, a serious illness caused by the paralysis of muscles.

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Why are homemade canned foods a potential source of botulism?

Botulism is a potential risk associated with consuming homemade canned foods, particularly low-acid foods such as meat and vegetables. The improper sterilization of these foods can allow for the growth of Clostridium botulinum and the production of its toxin.

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Why should infants avoid honey?

Honey is a natural source of botulinum spores. Infants, with their developing immune systems, are highly susceptible to botulism. Therefore, honey should be avoided for infants to prevent the risk of developing botulism.

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How does tetanus toxin affect the nervous system?

Tetanus toxin, produced by Clostridium tetani, disrupts neurotransmission by specifically targeting and destroying synaptobrevin, a critical protein involved in the release of inhibitory neurotransmitters. This disruption leads to an overactivity of motor neurons causing spastic paralysis.

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What is Lambert-Eaton syndrome?

Lambert-Eaton syndrome is an autoimmune disorder that targets and destroys specific calcium channels in the nerves responsible for skeletal muscle innervation. This destruction reduces the release of acetylcholine, leading to muscle weakness.

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What is the mechanism of Myasthenia Gravis?

Myasthenia gravis, an autoimmune disease, involves the production of antibodies that attack acetylcholine receptors (AChR) at the neuromuscular junction. This attack disrupts the normal neurotransmission process, leading to muscle weakness and fatigue.

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What is curare and how does it work?

Curare is a natural compound derived from tropical plants known for its muscle relaxant properties. It blocks the action of acetylcholine at the neuromuscular junction, preventing muscle contraction. This action has historically been used as a paralyzing agent and is currently used in certain medical contexts.

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