Nissl's Granules (Nissl Bodies): Composition and Function
Biology · Neural Control and Coordination · NEET
Nissl's granules (also called Nissl bodies) are granular structures inside the neuron's cell body and dendrites. They are made of free ribosomes and rough endoplasmic reticulum (RER), so they are the main site of protein synthesis in the neuron. Memory hook: "Nissl = neuron's protein factory (ribosomes + RER)."
Nissl's granules (purple dots) are packed in the neuron cell body and reach into the dendrites, but are absent in the axon. They are aggregations of free ribosomes and rough endoplasmic reticulum (RER), the protein-making machinery of the neuron.
Your doubts, answered
What exactly are Nissl's granules made of?
Nissl's granules are made of free ribosomes and rough endoplasmic reticulum (RER). Because ribosomes and RER build proteins, Nissl bodies are the protein-synthesis centre of the neuron. This is the exact fact NEET tests, so remember: free ribosomes + RER, NOT DNA, lipids, or SER.
Are Nissl bodies found in the axon?
No. Nissl's granules are present in the cell body (cyton) and extend into the dendrites, but they are absent in the axon and in the axon hillock. This is a favourite NEET point: the axon has no Nissl bodies, so it cannot make its own proteins and depends on the cell body.
Do dendrites have Nissl granules?
Yes. NCERT states that the short branching fibres that contain Nissl's granules are called dendrites. So dendrites contain Nissl bodies, while the axon does not. This difference helps you tell an axon from a dendrite in a diagram question.
Why does a neuron need Nissl granules at all?
Neurons are highly active cells that constantly make proteins, enzymes, and neurotransmitter-related molecules. Nissl bodies (ribosomes + RER) provide this high protein output. Their large amount is a sign of the neuron's strong metabolic and synthetic activity.
How are Nissl granules different from mitochondria in a neuron?
Nissl granules (ribosomes + RER) make proteins, while mitochondria make ATP (energy). Both are in the cell body, but only Nissl bodies are the protein-synthesis site. NEET options sometimes mix these up, so keep the jobs separate.
⚠️ The NEET trap ✗ Choosing 'DNA and RNA' or 'proteins and lipids' because Nissl bodies stain dark and look nucleus-like. ✓ Nissl bodies are made of free ribosomes and rough endoplasmic reticulum (RER); they synthesise protein but are not made of DNA or lipids. 🧠 Nissl = ribosomes + RER = protein FACTORY, not a DNA store. Dark staining is due to RNA in ribosomes, not DNA.
Real NEET questions
NEET 2018
Nissl bodies are mainly composed of
A · Nucleic acids and SER
B · DNA and RNA
C · Proteins and lipids
D · Free ribosomes and RER ✓
Solution: Nissl's granules (Nissl bodies) are granular bodies in the neuron cell body and dendrites. They are aggregations of free ribosomes and rough endoplasmic reticulum (RER), which makes them the main site of protein synthesis. So the correct answer is 'Free ribosomes and RER'. They are not made of DNA, lipids, or SER.
Solved Neural Control and Coordination NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
