Easy2Siksha sample Papers
GNDU Most Repeated (Important) Questions
B.A. 3rd Semester
PSYCHOLOGY (Biological Basis of Behaviour)
Based on 4-Year GNDU Question Paper Trend (2021–2024)
Must-Prepare Questions (80–100% Probability)
SECTION–A (Neurons & Synapses)
1. Structure and Functions of Neurons (with diagrams)
Appeared in: 2021 (Q1), 2022 (Q1), 2023 (Q1)
Probability for 2025: (100%)
2. Structure, Types, and Functions of Synapses (with diagrams)
Appeared in: 2021 (Q2), 2022 (Q2), 2023 (Q2), 2024 (Q1)
Probability for 2025: (100%)
GNDU Most Repeated (Important) Questions
B.A. 3rd Semester
PSYCHOLOGY (Biological Basis of Behaviour)
Based on 4-Year GNDU Question Paper Trend (2021–2024)
Must-Prepare Questions (80–100% Probability)
SECTION–A (Neurons & Synapses)
3. Structure and Functions of Neurons (with diagrams)
Appeared in: 2021 (Q1), 2022 (Q1), 2023 (Q1)
Probability for 2025: (100%)
4. Structure, Types, and Functions of Synapses (with diagrams)
Appeared in: 2021 (Q2), 2022 (Q2), 2023 (Q2), 2024 (Q1)
Probability for 2025: (100%)
Easy2Siksha sample Papers
2025 GUARANTEED QUESTIONS (100% Appearance Trend)
Top 9 Must-Prepare Topics
1. Structure & Functions of Neurons
2. Structure, Types & Functions of Synapses
Easy2Siksha sample Papers
GNDU Most Repeated (Important) Answers
B.A. 3rd Semester
PSYCHOLOGY (Biological Basis of Behaviour)
Based on 4-Year GNDU Question Paper Trend (2021–2024)
Must-Prepare Questions (80–100% Probability)
SECTION–A (Neurons & Synapses)
1. Structure and Functions of Neurons (with diagrams)
Appeared in: 2021 (Q1), 2022 (Q1), 2023 (Q1)
Probability for 2025: (100%)
Ans: The Incredible Story of Your Body's Messenger Cells
Imagine you're holding a smartphone in your hand right now. You touch the screen, and
instantly, a message travels to your friend across the world. Now, think about something
even more amazing: inside your body, at this very moment, billions of tiny biological
"smartphones" are sending messages to each other at lightning speed. These
remarkable cells are called neurons, and they're the reason you can read these words,
remember your best friend's face, feel the warmth of sunshine, and even dream at
night.
Easy2Siksha sample Papers
The Birth of a Communication Network
Your brain contains approximately 86 billion neurons. To put that in perspective, if each
neuron were a person, they'd represent more than ten times the entire human
population of Earth! But what makes these cells so special isn't just their number – it's
their extraordinary design and purpose.
Think of your nervous system as the world's most sophisticated postal service. Every
second of your life, countless messages need to be delivered: "The coffee cup is hot –
pull your hand away!" "That joke was funny – smile!" "Remember to call Mom
tomorrow." "Watch out for that car!" Each of these messages travels through a network
of neurons, and the speed and efficiency of this system would make any tech company
envious.
Anatomy of a Neuron: The Three-Part Messenger
Every neuron is like a tiny, living telegraph station with three main parts, each with its
own crucial job. Let's explore each one:
The Cell Body (Soma): The Command Center
Picture a small, round headquarters – that's your neuron's cell body, or soma. This isn't
just any ordinary cell center; it's the life-support system and control room rolled into
one.
Inside the soma, you'll find the nucleus, which contains all the genetic instructions (DNA)
that keep the neuron functioning. Surrounding the nucleus are thousands of
mitochondria – the power plants that generate energy for the cell. The soma also
contains ribosomes that manufacture proteins, the building blocks the neuron needs to
maintain itself and produce neurotransmitters (the chemical messengers we'll discuss
later).
The cell body typically measures about 10 to 80 micrometers in diameter – so tiny that
you'd need a microscope to see it. Despite its small size, this command center works
tirelessly, 24 hours a day, for your entire lifetime. Unlike many other cells in your body,
most neurons don't divide and replace themselves after you're born, which makes them
even more precious.
Dendrites: The Receivers
Branching out from the cell body like the branches of a winter tree, you'll find numerous
short, thread-like structures called dendrites. The word "dendrite" actually comes from
the Greek word "dendron," meaning tree – a fitting name for these beautiful, branching
structures.
Easy2Siksha sample Papers
Dendrites are the neuron's receivers, like countless tiny antennae picking up signals
from the environment. Each neuron can have hundreds or even thousands of dendrites,
creating an enormous surface area for receiving information. Some dendrites are
covered with small bumps called dendritic spines, which increase the surface area even
more – imagine adding leaves to the branches of our tree.
When a dendrite receives a signal from another neuron, it's like someone ringing your
doorbell. The dendrite captures this chemical message and converts it into an electrical
signal that travels toward the cell body. The more dendrites a neuron has, the more
connections it can make with other neurons – some neurons in your brain receive
signals from over 10,000 other neurons simultaneously!
The Axon: The Express Highway
Now comes the most remarkable part of the neuron's structure: the axon. If dendrites
are receivers, the axon is the transmitter – a single, long fiber that carries messages
away from the cell body to other neurons, muscles, or glands.
Some axons are incredibly short, measuring just a fraction of a millimeter. But others are
extraordinarily long – the axon that runs from your spinal cord down to your big toe can
be over three feet long! Imagine a single cell with an extension that long – it's like a cell
with a tail that stretches across your entire body.
The axon maintains the same diameter throughout its length and branches only at the
very end, where it forms multiple terminals called axon terminals or synaptic buttons.
These terminals are where the magic of neuron-to-neuron communication happens.
Many axons are wrapped in a fatty, white substance called myelin, which looks like
beads on a string. This myelin sheath is produced by special cells called Schwann cells (in
the peripheral nervous system) or oligodendrocytes (in the brain and spinal cord). The
myelin isn't continuous – there are tiny gaps between the segments called nodes of
Ranvier.
Why is myelin so important? It acts like insulation around an electrical wire, but even
better. It doesn't just prevent the signal from leaking out; it actually speeds up the
transmission dramatically. In a myelinated axon, the electrical signal literally jumps from
one node of Ranvier to the next in a process called saltatory conduction (from the Latin
word "saltare," meaning "to jump"). This allows signals to travel at speeds up to 120
meters per second – about 268 miles per hour! Without myelin, signals crawl along at
just 0.5 to 2 meters per second.
How Neurons Communicate: The Electrochemical Symphony
Now that we understand the structure, let's explore the truly magical part – how
neurons actually send messages to each other. This process combines both electrical
and chemical signals in a beautiful dance of biology and physics.
Easy2Siksha sample Papers
The Resting Potential: Calm Before the Storm
When a neuron isn't actively sending a signal, it's not exactly resting – it's preparing. The
neuron maintains what scientists call a resting potential, which is like a battery that's
fully charged and ready to discharge.
The inside of the neuron is negatively charged compared to the outside (about -70
millivolts). This difference is maintained by tiny protein pumps in the cell membrane that
continuously move sodium ions (Na+) out of the cell and potassium ions (K+) into the
cell. Think of it as the neuron holding its breath, waiting for the right moment to act.
The Action Potential: The Wave of Communication
When a neuron receives enough stimulation from other neurons, something dramatic
happens. The neuron reaches a threshold, and suddenly, like dominos falling in
sequence, channels in the cell membrane open up. Sodium ions rush into the cell,
making the inside briefly positive. This rapid change in electrical charge is called an
action potential, and it's an all-or-nothing event – the neuron either fires completely or
doesn't fire at all.
This electrical wave travels down the axon like a lightning bolt, moving at incredible
speeds (especially in those myelinated axons we talked about earlier). The action
potential is self-propagating – each section of the axon that fires triggers the next
section to fire, ensuring the message travels the entire length of the axon without losing
strength.
The Synapse: Bridging the Gap
Here's where things get even more interesting. When the electrical signal reaches the
axon terminal, it faces a problem: there's a tiny gap (called the synaptic cleft) between
this neuron and the next one. The gap is incredibly small – about 20-40 nanometers –
but the electrical signal can't jump across it.
So the neuron uses a brilliant solution: it converts the electrical signal into a chemical
one. When the action potential reaches the axon terminal, it triggers tiny bubbles
(vesicles) filled with neurotransmitters to fuse with the cell membrane and release their
contents into the synaptic cleft. These neurotransmitter molecules – chemicals like
dopamine, serotonin, acetylcholine, or GABA – float across the gap and bind to special
receptors on the dendrites of the next neuron, like keys fitting into locks.
When enough neurotransmitters bind to these receptors, they trigger a new electrical
signal in the receiving neuron, and the message continues on its journey. The whole
process happens in just a few milliseconds!
Types of Neurons: Specialized Workers
Easy2Siksha sample Papers
Not all neurons are identical – they've evolved into different types, each specialized for
particular tasks:
Sensory neurons (afferent neurons) are the body's reporters. They carry information
from your sensory organs to your central nervous system. When you touch something
hot, smell fresh coffee, or see a beautiful sunset, sensory neurons are the first
messengers delivering that news.
Motor neurons (efferent neurons) are the commanders. They carry instructions from
your brain and spinal cord to your muscles and glands, telling your body what to do.
Every movement you make, from blinking to running, involves motor neurons.
Interneurons are the processors and decision-makers. Found entirely within the central
nervous system, they connect sensory and motor neurons, integrate information, and
help you make decisions. They're the reason you can think, plan, and remember.
The Living Network
What makes neurons truly extraordinary isn't just their individual structure or function –
it's how they work together. Each neuron can connect with thousands of others,
creating a network of staggering complexity. Scientists estimate that the human brain
contains about 100 trillion synaptic connections – more connections than there are stars
in the Milky Way galaxy!
This network isn't fixed either. Throughout your life, neurons form new connections,
strengthen existing ones, and eliminate others in a process called neuroplasticity. Every
time you learn something new, practice a skill, or form a memory, you're actually
changing the physical structure of your neural network. You're literally reshaping your
brain with every experience.
The Poetry of Neural Communication
As you've been reading this explanation, billions of neurons have been firing in intricate
patterns throughout your brain. Neurons in your visual cortex processed the shapes of
letters. Neurons in your language centers decoded the meaning of words. Neurons in
your memory systems connected this new information with what you already knew. And
neurons throughout your brain worked together to create your subjective experience of
understanding.
Neurons are more than just cells – they're the physical foundation of consciousness
itself, the biological basis of every thought, feeling, and memory you've ever had.
They're the reason you can love, learn, dream, and wonder about the universe. In
understanding neurons, we're beginning to understand ourselves.
Easy2Siksha sample Papers
2. Structure, Types, and Functions of Synapses (with diagrams)
Appeared in: 2021 (Q2), 2022 (Q2), 2023 (Q2), 2024 (Q1)
Probability for 2025: (100%)
Ans; The Grand Junction: Where Neurons Meet and Magic Happens
Picture yourself standing at a bustling train station during rush hour. Thousands of
people are moving, messages are being delivered, and everything runs with split-second
precision. Now, imagine something even more spectacular – inside your brain, there are
trillions of these "stations" where nerve cells meet and communicate. These meeting
points are called synapses, and they're the reason you can think, feel, remember, and
do everything that makes you... well, you!
The Story Begins: What Exactly is a Synapse?
Let me take you back to a fascinating discovery. In the late 1800s, scientists were
puzzled. They knew the nervous system consisted of billions of nerve cells called
neurons, but here's what baffled them: How do these neurons talk to each other? Are
they directly connected like wires in a circuit, or is there something more mysterious
happening?
Enter Santiago Ramón y Cajal, a Spanish scientist who discovered that neurons don't
actually touch each other! There's a tiny gap between them – so small you'd need a
powerful electron microscope to see it. This gap, along with the specialized structures
Easy2Siksha sample Papers
around it, is what we call a synapse. The word comes from the Greek "synapsis,"
meaning "conjunction" or "junction."
Think of a synapse as a microscopic shipping dock where packages (information) are
loaded onto boats (neurotransmitters), sent across a narrow river (synaptic cleft), and
then unloaded at the receiving dock on the other side. Brilliant, isn't it?
The Architecture: Understanding the Structure
Let's zoom into a synapse and explore its magnificent architecture. Every synapse has
three main components, like a three-act play:
Act One: The Presynaptic Terminal (The Sender)
Imagine a warehouse packed with sealed packages ready for delivery. The presynaptic
terminal is the ending portion of the neuron that's sending the message. Here's what
makes it special:
Synaptic Vesicles: These are tiny bubble-like structures filled with chemical messengers
called neurotransmitters. Picture hundreds of small balloons filled with important
messages, just waiting for the signal to release their contents. Each vesicle contains
thousands of neurotransmitter molecules.
Voltage-Gated Calcium Channels: These are like security gates that only open when the
right signal arrives. When an electrical impulse (action potential) reaches the
presynaptic terminal, these channels swing open, allowing calcium ions to rush in. This
calcium influx is like sounding an alarm that says, "Release the packages NOW!"
Mitochondria: These are the power plants providing energy for all this activity.
Communication is hard work, and the synapse needs constant energy to keep
functioning.
Act Two: The Synaptic Cleft (The River Between)
Here's where the magic happens – in a gap so tiny it's only 20-40 nanometers wide.
That's about 1/2000th the width of a human hair! This microscopic space is filled with
fluid and special proteins. When those synaptic vesicles release their neurotransmitters,
the chemicals diffuse across this gap like perfume spreading through a room – except
this happens in less than a millisecond!
Act Three: The Postsynaptic Terminal (The Receiver)
On the other side of the synaptic cleft sits the receiving neuron, ready to catch the
message. Its membrane is studded with:
Easy2Siksha sample Papers
Receptors: These are like perfectly shaped locks waiting for the right keys. Each receptor
is designed to bind with specific neurotransmitters. When a neurotransmitter finds its
matching receptor, it's like a key turning in a lock – the door opens, and the message
gets through!
Ion Channels: Once the neurotransmitter binds to its receptor, these channels open or
close, allowing charged particles (ions) to flow in or out. This flow changes the electrical
state of the receiving neuron, either exciting it to fire its own signal or inhibiting it from
firing.
The Types: A Diverse Family
Just as there are many ways to communicate – texting, calling, emailing, or meeting
face-to-face – there are different types of synapses, each with its own style:
1. Chemical Synapses (The Messengers)
These are the most common type, making up about 99% of all synapses in your brain.
They use chemical neurotransmitters to send messages. The beauty of chemical
synapses is their flexibility – they can be strengthened or weakened, which is the basis of
learning and memory!
The Communication Process: When an electrical signal arrives at the presynaptic
terminal, it triggers the release of neurotransmitters. These chemicals cross the synaptic
cleft, bind to receptors, and convert back into an electrical signal in the receiving
neuron. It's like converting digital information to radio waves for transmission, then back
to digital on the receiving end!
2. Electrical Synapses (The Direct Line)
Imagine two houses connected by a tunnel – that's essentially what electrical synapses
are! The neurons are connected by special channels called gap junctions, allowing
electrical current to flow directly from one cell to another.
These synapses are much faster than chemical synapses because there's no chemical
conversion involved. They're found in places where speed is absolutely critical, like in
your heart muscle (ensuring all cells contract simultaneously) and in parts of the brain
that coordinate rapid reflexes.
3. Based on Location: Axodendritic, Axosomatic, and Axoaxonic
These names describe where the synapse forms:
Axodendritic: Connection from one neuron's axon to another's dendrite (most common)
Axosomatic: Connection from axon to cell body (powerful influence) Axoaxonic:
Connection from axon to another axon (can control neurotransmitter release)
Easy2Siksha sample Papers
It's like having different entrances to a building – front door, side door, or connecting
directly to another corridor!
The Function: How Synapses Actually Work
Now for the thrilling part – watching a synapse in action! Let's follow a signal step by
step:
Step 1: The Arrival
An electrical impulse (action potential) races down the axon at speeds up to 100 meters
per second – faster than a race car! When it reaches the presynaptic terminal, it's like a
train pulling into the station.
Step 2: The Calcium Rush
The electrical signal causes those voltage-gated calcium channels to burst open. Calcium
ions flood into the terminal like water through a broken dam. This is the critical trigger.
Step 3: Vesicle Fusion
The synaptic vesicles, sensing the calcium influx, move toward the cell membrane.
Through an elegant molecular dance involving special proteins called SNAREs (yes, they
"snare" vesicles to the membrane!), the vesicles fuse with the membrane and spill their
neurotransmitter contents into the synaptic cleft. This process is called exocytosis.
Step 4: The Journey Across
Thousands of neurotransmitter molecules now diffuse across the synaptic cleft. Despite
the tiny distance, this is a random walk – molecules bumping around until they reach the
other side.
Step 5: The Reception
Neurotransmitters bind to their specific receptors on the postsynaptic membrane. This
binding causes ion channels to open or close. If the neurotransmitter is excitatory (like
glutamate), it makes the receiving neuron more likely to fire. If it's inhibitory (like
GABA), it makes the neuron less likely to fire.
Step 6: The Cleanup
Here's something crucial – the signal can't last forever! The synapse must be reset for
the next message. This happens through:
• Reuptake: The presynaptic neuron vacuums up the neurotransmitter for
recycling
Easy2Siksha sample Papers
• Enzymatic degradation: Special enzymes break down the neurotransmitter
• Diffusion: Some molecules simply drift away
The Significance: Why This All Matters
Synapses aren't just message-passing stations – they're the foundation of everything
your brain does:
Learning and Memory: When you study for an exam, you're strengthening certain
synapses through a process called long-term potentiation. The more you use a synaptic
pathway, the stronger it becomes. That's why practice makes perfect!
Emotions and Mood: Many neurotransmitters (like serotonin and dopamine) released at
synapses influence how you feel. When these systems work well, you feel balanced.
When they don't, it can lead to depression or anxiety.
Drugs and Medicines: Most psychiatric medications work by altering synaptic function –
either increasing or decreasing neurotransmitter availability.
Diseases: Many neurological conditions involve synaptic dysfunction. In Alzheimer's
disease, synapses deteriorate. In Parkinson's disease, dopamine-releasing synapses are
damaged.
The Grand Finale
Every thought you have, every movement you make, every memory you cherish – it all
depends on synapses. Your brain contains roughly 100 trillion synapses, and they're
constantly changing, adapting, and rewiring themselves based on your experiences.
You're literally reshaping your brain's synaptic connections right now as you read and
understand this explanation!
The synapse is where chemistry meets electricity, where information becomes
knowledge, and where the microscopic becomes magnificent. It's the grand junction
where the physical world of molecules and ions creates the intangible world of thoughts,
dreams, and consciousness.
“This is only a part of the preparation journey.
For full access to repeated questions and detailed answers,
purchase our Premium Papers and boost your chances of scoring
higher!”
