Synapses & Neuromuscular Junctions

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Questions and Answers

What is the primary distinction between electrical and chemical transmission?

Electrical transmission uses neurotransmitters while chemical transmission does not.

Electrical transmission relies on ion channels, while chemical transmission relies on vesicles and neurotransmitters. (correct)

Electrical transmission occurs across synaptic clefts, chemical transmission does not.

Electrical transmission is slower than chemical transmission.

What role do MEPPs play in synaptic transmission?

They provide evidence of quantal release of neurotransmitters at the neuromuscular junction. (correct)

They indicate the release of multiple neurotransmitter vesicles simultaneously.

They are responsible for the generation of action potentials in the pre-synaptic neuron.

They represent the total summation of all synaptic activity at a post-synaptic neuron.

Which structural feature is critical to the function of the neuromuscular junction?

A high density of voltage-gated sodium channels on the post-synaptic membrane.

Presence of myelinated axons for rapid signal conduction.

The presence of active calcium pumps in the post-synaptic neuron.

The separation of pre-synaptic and post-synaptic neurons by the synaptic cleft. (correct)

How do temporal and spatial summation primarily differ?

Temporal summation involves several stimuli in quick succession, while spatial summation involves multiple stimuli from different sources. Signup and view all the answers

What molecule is primarily responsible for the quantal release of neurotransmitters?

Calcium ions entering the pre-synaptic terminal. Signup and view all the answers

Which statement correctly describes the historical discovery of the synapse?

The synaptic cleft was first identified by Loewi in the early 1920s. Signup and view all the answers

What is the primary role of Ca2+ in synaptic communication?

To trigger the exocytosis of synaptic vesicles Signup and view all the answers

What determines whether a postsynaptic cell will fire an action potential?

The integration of EPSP’s and IPSP’s Signup and view all the answers

Which substance is NOT involved in reducing vesicle release at the synapse?

ACh (Acetylcholine) Signup and view all the answers

What occurs at the axon hillock in relation to action potentials?

Integration of graded potentials takes place Signup and view all the answers

Which scenario describes a suprathreshold postsynaptic response?

The sum of multiple subthreshold potentials reaches threshold Signup and view all the answers

Which condition is most likely to decrease neurotransmitter release at a synapse?

Elevated levels of magnesium Signup and view all the answers

What is the consequence of a resting synapse that is exposed to curare?

Inhibition of postsynaptic receptor binding Signup and view all the answers

What is the characteristic behavior of graded potentials in the cytoplasm?

They diminish quickly with distance Signup and view all the answers

Which component of neuronal communication is primarily responsible for integrating signals?

Cell body Signup and view all the answers

What is the effect of EPSP on a neuron's likelihood to fire an action potential?

It generates depolarization, making firing more likely. Signup and view all the answers

Which of the following accurately describes IPSP?

It contributes to generating hyperpolarization. Signup and view all the answers

What is the primary role of EPSP and IPSP in synaptic communication?

To determine if a neuron will reach the threshold for action potential. Signup and view all the answers

What occurs when EPSPs and IPSPs interact?

They act to cancel each other out, influencing the firing outcome. Signup and view all the answers

Which statement is true regarding the nature of EPSP and IPSP?

They are sub-threshold events and can modify firing likelihood. Signup and view all the answers

How do EPSP and IPSP contribute to spatial and temporal summation?

They combine their effects to determine postsynaptic potential changes. Signup and view all the answers

Which scenario lessens the chance of a neuron firing an action potential?

Increasing the number of IPSPs. Signup and view all the answers

Why are EPSPs considered excitatory?

They cause depolarization of the postsynaptic neuron. Signup and view all the answers

Study Notes

Learning Outcomes

Understand distinctions between electrical transmission (heart) and chemical transmission (neural synapses).
Recognize structural features of the neuromuscular junction (NMJ).
Explain quantal release mechanism of neurotransmitters.
Differentiate between miniature end plate potentials (MEPPs) and end plate potentials (EPPs).
Clarify temporal and spatial summation concepts.

Concept of the Synapse

Discovery of the synaptic cleft by Sherrington in the early 1900s.
Synaptic transmission relies on chemical neurotransmitters, as demonstrated by Loewi in the 1920s.

Synaptic Communication

Calcium ions (Ca2+) play a crucial role in synaptic communication.
Voltage-gated Ca2+ channels open upon action potential arrival.
Ca2+ entry triggers exocytosis of neurotransmitter-filled vesicles.
Neurotransmitters diffuse across the synaptic cleft to activate postsynaptic neurons.

Subthreshold and Suprathreshold Postsynaptic Responses

Subthreshold responses exhibit graded potentials and diminish quickly.
Suprathreshold responses can trigger action potentials depending on the depolarization level at the axon hillock.

Graded Potentials

Initiated by stimuli causing localized depolarization.
The magnitude of the potential can decrease rapidly over distance.

Action Potential Propagation

Action potentials propagate along the axon, reaching the presynaptic terminal.

Integration of EPSPs and IPSPs

Excitatory postsynaptic potentials (EPSPs) sum to depolarize the neuron, promoting action potential firing.
Inhibitory postsynaptic potentials (IPSPs) contribute to hyperpolarization, reducing action potential likelihood.
The balance of EPSPs and IPSPs determines neuronal firing.

Drugs & Neurotransmission

Factors affecting vesicle release include low calcium levels, high magnesium levels, curare (a toxin), and botulinum toxin (Botox).
These factors impair neurotransmission by disrupting the normal release of neurotransmitters.

Knee Jerk Reflex

Illustrates communication across neural networks in response to stimuli.
Involves muscle spindles detecting stretch and eliciting a reflexive response.

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Description

Explore the essential differences between electrical and chemical synapses, focusing on their roles in the heart and neural transmission. This quiz will help you understand synaptic transmission and its significance in physiology. Perfect for students of psychiatry and neuroscience.