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NEURONS: THE BUILDING BLOCKS OF THE NERVOUS SYSTEM

The Role of Neurons

Core Function

Neurons are the fundamental cells of the nervous system responsible for receiving, processing, and transmitting electrical and chemical signals. These specialized cells allow communication within the nervous system and between the brain, spinal cord, and peripheral organs.

Basic Neuronal Structure

A typical neuron has three main components:

1

Cell body (soma)

Contains the nucleus and organelles that maintain cell function
2

Dendrites

Branch-like structures that receive messages from other neurons
3

Axon

A long fiber that carries electrical impulses away from the cell body to other neurons, muscles, or glands
4

Axon terminals

End points of the axon where neurotransmitters are released to communicate with another cell

Classification of Neurons

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Sensory Neurons

Carry messages from sensory receptors (skin, eyes, ears) to the CNS. They detect information such as pain, temperature, and pressure.
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Relay Neurons (Interneurons)

Found within the CNS, relay neurons connect sensory neurons to motor neurons or other interneurons for processing information. They are involved in reflexes and brain functions.
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Motor Neurons

Transmit impulses from the CNS to muscles or glands to produce movement or action.

Synaptic Transmission Process

Synaptic transmission involves converting an electrical signal into a chemical message and back into an electrical signal. The process includes:

I

Release of neurotransmitters

When an electrical impulse (action potential) reaches the axon terminal, it triggers the release of neurotransmitters stored in vesicles into the synaptic cleft.
II

Binding to receptors

Neurotransmitters cross the synaptic gap and bind to receptor sites on the receiving neuron, causing ion channels to open, which generates a new electrical signal in the receiving neuron.
III

Reuptake

After neurotransmitters have transmitted their message, they are either broken down by enzymes or taken back into the presynaptic neuron via reuptake for reuse or disposal.

Signal Modulation

✅
Excitatory Neurotransmittersincrease the likelihood that the receiving neuron will fire an impulse by depolarizing the membrane (making it less negative inside). Examples include glutamate.
❌
Inhibitory Neurotransmittersdecrease the chance of the neuron firing by hyperpolarizing the membrane (making it more negative). Examples include gamma-aminobutyric acid (GABA).

Interaction & Complex Processing

How these processes interact

The balance between excitation and inhibition is vital for proper brain function, allowing for coordinated responses and preventing overstimulation. Neurons continuously integrate excitatory and inhibitory signals to decide whether or not to fire an action potential. This dynamic communication enables complex processing such as learning, memory, and decision-making.

Hebb's Postulate on Learning

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The Core Principle: Donald Hebb proposed that learning arises from activity-dependent changes in synaptic strength, often summarized by the phrase “neurons that fire together, wire together.”

Neuroplasticity and Learning

Hebb’s concept underlies modern understandings of neuroplasticity. This idea explains:

A

Shaping Neural Pathways

How repeated experiences can shape neural pathways over time
B

Long-Term Memory

The formation of long-term memories through synaptic growth and plasticity
C

Brain Adaptability

The brain’s ability to adapt and reorganize in response to learning or injury
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Neuron Flashcards
Term
Primary Function of Neurons

What is the primary function of neurons?

Answer
Function

To receive, process, and transmit electrical and chemical signals in the nervous system.

Term
Main Parts of a Neuron

Name the three main parts of a typical neuron.

Answer
Parts

Cell body (soma), dendrites, and axon.

Term
Role of Dendrites

What role do dendrites play in a neuron?

Answer
Role

They receive messages from other neurons.

Term
Function of Axon

What is the function of the axon?

Answer
Function

To carry electrical impulses away from the cell body to other neurons, muscles, or glands.

Term
Axon Terminals

What are axon terminals responsible for?

Answer
Responsibility

Releasing neurotransmitters to communicate with other cells.

Term
Types of Neurons

List the three types of neurons and their functions.

Answer
Types & Functions

Sensory neurons carry messages to the CNS; relay neurons (interneurons) connect sensory and motor neurons; motor neurons carry impulses from CNS to muscles or glands.

Term
Synaptic Transmission

Describe synaptic transmission.

Answer
Process

The process where electrical signals are converted into chemical messages at the synapse and then back into electrical signals in the receiving neuron.

Term
Neurotransmitter Binding

What happens when neurotransmitters bind to receptors on the receiving neuron?

Answer
Effect

Ion channels open, generating a new electrical signal.

Term
Excitatory Neurotransmitters

Define excitatory neurotransmitters.

Answer
Definition

Chemicals that increase the chance the receiving neuron will fire by depolarizing its membrane.

Term
Inhibitory Neurotransmitters

Define inhibitory neurotransmitters.

Answer
Definition

Chemicals that decrease the chance the receiving neuron will fire by hyperpolarizing its membrane.

Term
Hebb’s Theory of Learning

What is Hebb’s theory of learning?

Answer
Theory

Neurons that fire together wire together, meaning synaptic connections strengthen with repeated simultaneous activation.

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🧠 Neuroscience Quiz

1. Which part of the neuron is responsible for receiving messages?

Dendrites receive messages from other neurons and transmit them to the cell body.

2. What type of neuron carries information from sensory receptors to the central nervous system?

Sensory neurons transmit signals from sensory receptors (like skin and eyes) to the CNS.

3. During synaptic transmission, neurotransmitters are released from:

Neurotransmitters are released from the axon terminals to cross the synaptic gap.

4. Which of the following is an excitatory neurotransmitter?

Glutamate excites neurons by depolarizing their membranes.

5. Hebb’s theory of learning can be summarized by which phrase?

This means that simultaneous neuronal activity strengthens connections between neurons.

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