DEEP LEARNING LESSON 2 NEURAL NETWORKS

Neurons

A neuron is a small processing unit inside a neural network. It receives information, performs calculations, and produces an output that is passed to the next part of the network.

In simple words

A neuron takes input values, processes them, and produces a result.

Where Are Neurons Used?

Neurons are the building blocks inside the layers of a neural network.

INPUT
Input Layer
HIDDEN
Neuron
Neuron
Neuron
OUTPUT
Output Layer

A hidden layer usually contains multiple neurons working together.

What Does a Neuron Do?

A neuron receives one or more input values. It processes those values and produces an output.

Input 1
Input 2
Input 3
Neuron
Output

The output from one neuron can become an input to neurons in the next layer.

Simple Example — Student Prediction

Suppose we want a neural network to predict whether a student will pass an exam.

We give the network three inputs:

Hours Studied = 7
Attendance = 90
Previous Score = 82

A neuron receives information from these inputs and processes it.

INPUTS
7
90
82
NEURON
Processes Inputs
OUTPUT
Result

A Layer Can Have Many Neurons

A neural network usually does not rely on just one neuron. A layer can contain many neurons.

INPUT
Input 1
Input 2
Input 3
HIDDEN LAYER
Neuron 1
Neuron 2
Neuron 3
Neuron 4
OUTPUT
Prediction

Each neuron can learn different patterns from the information it receives. Together, the neurons allow the layer to represent more useful information.

Neurons Work Together

One neuron by itself is usually not the whole model. Neural networks contain many connected neurons that pass information from one layer to another.

Input
Neurons
More Neurons
Prediction

This connection between neurons is what gives a neural network its ability to process complex data.

Example — Recognizing an Image

Imagine a neural network that receives an image of an animal.

The input contains many numerical pixel values. Neurons can process those values and help the network identify useful patterns.

Image Pixels
Neurons
Learned Patterns
Animal Prediction

In an image model, different layers can learn increasingly useful representations. For example, earlier layers may respond to simple visual patterns, while deeper layers can combine those patterns into more meaningful features.

Think of a Neuron as a Small Calculator

A useful beginner-friendly way to think about a neuron is as a small calculator.

Input Values
Neuron
Processed Value

The neuron does not simply copy the input. It performs mathematical operations on the values and produces a new value.

Important

We will learn exactly how the calculation works when we study weights and bias. For now, remember that the neuron takes inputs and transforms them into an output.

Neurons Pass Information Forward

The output of a neuron can be passed to neurons in the next layer.

LAYER 1
Neuron 1
Neuron 2
LAYER 2
Neuron 3
Neuron 4
Neuron 5
LAYER 3
Output

This creates a chain of calculations through the network.

Neuron vs Layer

Term
Meaning
Neuron
One processing unit that receives inputs and produces an output.
Layer
A group of neurons working at the same stage of the network.
Neural Network
Multiple connected layers of neurons.

Think of it like this:

Neuron
   ↓
Layer
   ↓
Neural Network

Complete Neural Network Flow

INPUT
Features
HIDDEN LAYER
Neuron
Neuron
Neuron
OUTPUT
Prediction

So the overall process is:

Input Data
    ↓
Neurons Process Data
    ↓
More Neurons Process the Results
    ↓
Final Output

What You Should Remember

A neuron is a basic processing unit of a neural network. It receives input values, performs calculations, and produces an output. Many connected neurons form layers, and multiple layers form a neural network.

QUICK CHECK

Check Your Understanding

What is a neuron?
A basic processing unit inside a neural network.

What does a neuron receive?
It receives one or more input values.

What does a neuron produce?
It produces an output value that can be passed to the next layer.

What is a layer?
A group of neurons working at the same stage of the network.

NEXT TOPIC

Weights and Bias

Now we will look at the parameters that control how a neuron processes its input: weights and bias.