In neurons, ion exchange is a fundamental process that allows nerve cells to send and receive electrical signals. The two most important ions in this process are:

• Sodium (Na⁺)

• Potassium (K⁺)

Let's break down how this works:

⚡ What is Ion Exchange in Neurons?

Ion exchange refers to the movement of ions (charged particles) across the neuron’s membrane through specialized proteins called ion channels and pumps. This creates electrical signals that transmit information through the nervous system.

🔄 Resting Membrane Potential

When a neuron is not sending a signal, it’s in a resting state. During this state:

• Inside the neuron: more K⁺, less Na⁺

• Outside the neuron: more Na⁺, less K⁺

• Charge inside: -70 mV (negative)

This imbalance is maintained by the Sodium-Potassium Pump (Na⁺/K⁺ ATPase):

🧠 Na⁺/K⁺ Pump Action:

• Pumps 3 Na⁺ out

• Pumps 2 K⁺ in

• Uses 1 ATP for energy

✅ Maintains:

• A negative charge inside

• A concentration gradient (difference in Na⁺ and K⁺ levels)

⚡ How a Signal (Action Potential) Happens

When a neuron fires, it sends an electrical signal called an action potential.

🔹 Step-by-Step Breakdown:

1. Resting State (-70 mV):

• Na⁺ channels closed

• K⁺ channels slightly open

• Cell is polarized (negative inside)

2. Depolarization (Signal Begins):

• A stimulus opens Na⁺ channels

• Na⁺ rushes in

• Inside becomes less negative, then positive (up to +30 mV)

3. Repolarization (Return to Rest):

• Na⁺ channels close

• K⁺ channels open

• K⁺ rushes out

• Inside becomes negative again

4. Hyperpolarization (Overshoot):

• Too much K⁺ leaves

• Cell becomes extra negative (below -70 mV)

5. Return to Resting State:

• Na⁺/K⁺ pump restores balance

• Ready to fire again

📊 Summary Table:

🧠 Analogy

Think of Na⁺ and K⁺ like gates at a football stadium:

• Fans = ions

• Opening gates = ion channels

• Gate control = neuron decides who enters/exits

• Crowd behavior (movement of ions) = electrical signal