Structure of Neuron and Synapse

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Questions and Answers

What is the threshold potential that a neuron must reach to fire?

-55 mV (correct)

-90 mV

-70 mV

-40 mV

Which process is primarily responsible for the repolarisation of a neuron?

Chloride efflux

Sodium influx

Calcium influx

Potassium efflux (correct)

What occurs during the depolarisation phase of a neuron's action potential?

Potassium ions enter the neuron

Chloride channels remain inactive

Potassium channels close

Sodium channels open (correct)

What is the role of sodium-potassium ATPase in neuron function?

To maintain resting membrane potential Signup and view all the answers

What characterizes hyperpolarisation in a neuron?

Membrane potential becomes more negative Signup and view all the answers

What happens when neurotransmitters bind to ligand-gated channels at the synapse?

Opening of sodium channels Signup and view all the answers

What is the significance of reaching -70 mV in a neuron?

It is the resting potential of the neuron. Signup and view all the answers

What is the primary ion responsible for the depolarisation of a neuron?

Sodium Signup and view all the answers

What is the primary function of dendrites in a neuron?

To receive signals from axon endings of other neurons Signup and view all the answers

Which structure in the neuron is responsible for carrying information along its length?

Axon Signup and view all the answers

In the flow of information within a neuron, which sequence is correct?

Dendrites -> Cell body -> Axon -> Terminals -> Effector cell Signup and view all the answers

What role do glial cells play in relation to neurons?

They provide structural support and regulate the environment around neurons Signup and view all the answers

Which part of a neuron contains the nucleus?

Soma/Cell body Signup and view all the answers

Which neurotransmitter is primarily associated with signal transmission in the retina?

Glutamate Signup and view all the answers

What is the resting potential of a typical neuron?

-70 mV Signup and view all the answers

What is the primary function of the soma in a neuron?

To maintain normal neuron functioning Signup and view all the answers

What effect does GABA have on postsynaptic cells when it binds to GABAA receptors?

Causes hyperpolarization Signup and view all the answers

How does presynaptic inhibition affect excitatory signals at a synapse?

Inhibits the release of neurotransmitters Signup and view all the answers

Which type of neuron is characterized by having only one process extending from the cell body?

Unipolar neuron Signup and view all the answers

What is the role of myelination in axons?

It allows faster information transmission Signup and view all the answers

What type of receptors are GABAB receptors classified as?

Metabotropic receptors Signup and view all the answers

Which type of neuron has multiple tapering dendrites and a single axon?

Multipolar neuron Signup and view all the answers

What ions do GABAB receptors open to result in hyperpolarization?

Potassium ions Signup and view all the answers

Which structure in a neuron is responsible for signaling to other neurons?

Axon terminal Signup and view all the answers

What is the primary role of neurotransmitters released at the axon terminal?

Facilitate membrane depolarization Signup and view all the answers

What distinguishes pseudounipolar neurons from unipolar neurons?

Pseudounipolar neurons do not have dendrites Signup and view all the answers

Which mechanism primarily makes a neuron less likely to fire by making the cell more negative?

Hyperpolarization Signup and view all the answers

Which type of receptor promotes the entry of chloride ions into the postsynaptic cell?

GABA receptors Signup and view all the answers

What structural characteristic is common to bipolar neurons?

One axon and one dendrite on opposite ends Signup and view all the answers

Which of the following accurately describes the function of neurofilaments?

They support the structure of the cell Signup and view all the answers

What is the primary role of glial cells in the retina?

To support and maintain the retinal environment Signup and view all the answers

Which type of glial cells acts as specialized macrophages in the retina?

Microglia Signup and view all the answers

What mediates the entry of immune cells into the retina?

Microglia Signup and view all the answers

Where are glial cell axonal and vascular sheaths found?

Retinal nerve fiber layer (RNFL) Signup and view all the answers

What happens at the axon terminal during synaptic transmission?

Calcium influx occurs Signup and view all the answers

What is the result of depolarization in the presynaptic terminal?

Increased release of neurotransmitters Signup and view all the answers

What structure is responsible for fusing with the cell membrane during neurotransmission?

Synaptic vesicle Signup and view all the answers

What is the primary function of the blood-retina barrier?

Regulate the exchange of substances between the bloodstream and retina Signup and view all the answers

Study Notes

Neuron Structure

Neurons consist of four main components: dendrites, soma (cell body), axon, and axon terminals.
Information flow: Dendrites -> cell body -> axon -> terminals -> effector cell.

Dendrites

Branch out from the cell body and can be extensive, receiving signals from other neurons at synapses.
Composed of neurofilaments for structural support.

Soma (Cell Body)

Acts as the metabolic center of the neuron, essential for maintaining normal functions.
Produces proteins necessary for neuron maintenance and activity.
Neurons are classified by the shape of the cell body and the arrangement of the processes extending from it.

Neuron Classification

Unipolar Neurons: One process extends from the cell body, branching into axon and dendrite.
Bipolar Neurons: One axon and one dendrite extend from opposite ends of the cell body.
Pseudounipolar Neurons: A single axon bifurcates into two branches; commonly found in sensory neurons.
Multipolar Neurons: Numerous tapering dendrites with one axon, allowing for extensive connectivity.

Axons

Known as nerve fibers, they carry electrical messages to other neurons.
Can extend long distances and are myelinated, which enhances the speed of information transmission.
Terminate in axon terminals where neurotransmitter release occurs.

Action Potential Process

Initiated by depolarization when the membrane potential reaches a threshold of -55 mV.
Steps include hypopolarization, depolarization, repolarization, and hyperpolarization.
Sodium ions influx leads to action potential propagation, facilitated by ligand-gated channels.

Presynaptic Inhibition

Inhibition occurs before an excitatory signal reaches the postsynaptic neuron.
Involves GABA:
- GABAA Receptors: Ionotropic, allowing chloride ions into the cell, making it more negative.
- GABAB Receptors: Metabotropic, opening potassium channels and hyperpolarizing the neuron.

Retina and Glial Cells

Glial cells in the retina, including microglia, act as specialized macrophages.
They remove damaged neurons and maintain the neuroretinal microenvironment.
Microglia mediate the entry of immune cells into the retina.

Synapse Functionality

Action potentials arriving at the axon terminal cause depolarization.
Voltage-gated calcium channels open, allowing calcium influx which triggers neurotransmitter release from vesicles into the synaptic cleft.
This chemical synapse facilitates information propagation to the next neuron.

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This quiz covers essential topics related to the structure of neurons and synapses, focusing on their functions and significance in the nervous system. Designed for OPTM4106, the quiz aims to enhance your understanding of neuroanatomy and synaptic transmission. Prepare to test your knowledge on these critical concepts.

Structure of Neuron and Synapse - OPTM4106

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