Solved Nervous System Worksheet Section A Fill in the blanks ... - Free Printable

Let's solve this Nervous System Worksheet step by step. The task is to:

1. Fill in the blanks for each type of neuron (sensory, motor, relay).
2. Label the parts of the neurons using the provided words:
cell body, dendrite, axon, myelin sheath, nucleus, sensory, motor, relay

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🔍 Step 1: Understand the types of neurons

There are three main types of neurons:

- Sensory neurons: Carry signals from sensory receptors (e.g., skin, eyes) to the central nervous system (CNS). They have long dendrites and short axons.
- Motor neurons: Carry signals from the CNS to muscles or glands. They have a long axon and shorter dendrites.
- Relay (interneurons): Connect sensory and motor neurons within the CNS. Usually found in the brain and spinal cord.

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🧩 Step 2: Analyze each diagram

#### Diagram 1:
This neuron has:
- A long process with many branches at one end, which is typical of dendrites.
- A long axon extending from the cell body.
- The cell body is located near the middle.
- It has many dendrites at the top and a long axon at the bottom.

👉 This is a sensory neuron because it has long dendrites and shorter axon (but in some diagrams, the long process is shown as the axon — however, sensory neurons typically have dendrites receiving input).

Wait — actually, in sensory neurons, the long process is often the axon, and the dendrites are short. But in standard diagrams, sensory neurons have a long dendrite from the receptor ending into the CNS.

Looking closely:
- The top part (a) has many branching structures → these are dendrites.
- The bottom part (e) has a long structure → likely the axon.
- The middle (c) contains the nucleus → that’s the cell body.

But wait — sensory neurons usually have long dendrites and short axons? Actually, no — sensory neurons have long axons and short dendrites when they originate from sensory receptors.

But in this diagram, the top part (a) has many branches → dendrites. The bottom (e) has a long fiber → axon.

So let’s re-analyze:

In sensory neurons, the dendrite receives stimulus (from skin, etc.), and the axon carries the signal to the CNS.

But in standard textbook diagrams, sensory neurons are drawn with the long process being the axon, and dendrites near the receptor.

However, in this diagram, the top (a) has many branches — that's dendrites.

But if the dendrites are at the top, and the axon is at the bottom, then it would be a motor neuron?

Wait — motor neurons have dendrites receiving input from interneurons, and a long axon going to muscles.

So let's compare all three diagrams.

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✔ Let’s go through each diagram carefully:

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🔹 Diagram 1:

- a: Branched structures at the top → Dendrites
- b: Coated structure around the axon → Myelin sheath
- c: Round structure with nucleus → Cell body
- d: Long fiber coming from the cell body → Axon
- e: Branching end of axon → Axon terminals (but not labeled; just label the axon)

Wait — but e is labeled on the axon — so likely axon.

But d is pointing to the myelin sheath? No — look:

Actually, looking at the diagram:

- a = Dendrites
- b = Myelin sheath (covering the axon)
- c = Cell body (contains nucleus)
- d = Axon
- e = Axon terminals (but we don’t have "axon terminals" in word list — so likely axon)

But d points to the axonal shaft, and e points to the end branches — both part of the axon.

But since only one label per box, likely:

- a: Dendrite
- b: Myelin sheath
- c: Cell body
- d: Axon
- e: Axon (or possibly axon terminals — but not in list)

But e is at the tip — still part of the axon.

Wait — b is pointing to the coated part — that’s myelin sheath.

c is the cell body.

d is the axon.

e is the axon terminal — but again, not in list. So likely, e is labeled as axon.

But perhaps d is myelin sheath?

Let’s check:

- b is the myelin sheath (the white coating around the axon).
- d is the axon (the long fiber).
- e is the axon terminal — but not in list.

Wait — d is pointing to the axon, and b to the myelin sheath.

Yes.

Now, what kind of neuron is this?

- Has long dendrites at the top (a), long axon at bottom (d), cell body in middle (c).

This is a sensory neuron — because sensory neurons have long dendrites (from sensory receptor) and long axon to CNS.

Wait — actually, sensory neurons have long axons, but short dendrites?

No — in fact, sensory neurons have long dendrites that extend to the skin or sense organs, and long axons that go to the spinal cord.

So yes, both ends are long — but the dendrites are the ones receiving input.

So a = dendrite, d = axon.

And b = myelin sheath (around axon), c = cell body.

So Diagram 1 is a sensory neuron.

✔ So: 1) A sensory neuron

Labels:
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon (since it's the end of the axon — but only one label, so likely axon) — but wait, e is pointing to the branching end — still part of axon.

But maybe e is axon terminals — but not in word list.

Alternatively, perhaps e is axon.

But we have two boxes for axon? No — each letter has one label.

So likely:
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

But that can't be — same label twice?

Wait — maybe d is myelin sheath, and b is something else?

Let’s re-express:

Looking at the diagram:

- a — branched structures at top → dendrite
- b — the white oval-shaped segments along the axon → myelin sheath
- c — the round structure with black dot → cell body (and the dot is nucleus)
- d — the long fiber extending from cell body → axon
- e — the branched end of the axon → axon (again)

But the word list includes: cell body, dendrite, axon, myelin sheath, nucleus, sensory, motor, relay

So nucleus is also available.

Ah! c has a black dot — that’s the nucleus.

So c should be nucleus?

But c is pointing to the entire cell body.

Wait — the arrow is pointing to the whole round area, which is the cell body, and inside is the nucleus.

But the label is c, and it's pointing to the cell body.

So c = cell body

But the dot is the nucleus — but there’s no separate label for it.

So likely, c is cell body, and the nucleus is part of it.

But the word list says “nucleus” — so maybe we need to use it.

Wait — f and g are below — maybe those are for the third diagram.

Let’s move to Diagram 2.

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🔹 Diagram 2:

This neuron has:
- One long axon extending down
- Few dendrites at the top
- Cell body near the top
- Long axon with myelin sheath

This looks like a motor neuron.

Because:
- Motor neurons have short dendrites (receive input from interneurons)
- Long axon (to muscle)
- Cell body near the top
- Myelin sheath around axon

So: 2) A motor neuron

Labels:
- a: dendrite (small branches at top)
- b: myelin sheath (white segments on axon)
- c: cell body (round structure)
- d: axon (long fiber)
- e: axon (again — tip)

But again, e is the end of axon — still axon

But perhaps d is axon, e is axon terminals — but not in list.

Wait — maybe d is myelin sheath?

No — d points to the axon shaft, b points to the myelin sheath.

Yes.

So:
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

But e is the terminal end — still part of axon.

So acceptable.

But c has a black dot — is that the nucleus?

Yes — but we already used cell body.

The word list includes nucleus, so maybe c is nucleus?

But the arrow points to the whole cell body, not just the nucleus.

So likely, c is cell body, and the nucleus is inside.

So we don’t need to label the nucleus separately unless asked.

But in the third diagram, we have f, g, h — perhaps for relay neuron.

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🔹 Diagram 3:

This is a relay neuron (interneuron).

Features:
- Short axon
- Multiple dendrites
- Cell body in center
- No long processes

So: 3) A relay neuron

Labels:
- f: dendrite
- g: axon
- h: cell body

Or vice versa?

Look:
- f points to one dendrite
- g points to axon
- h points to cell body

Yes.

So:
- f: dendrite
- g: axon
- h: cell body

Now, back to Diagram 1 and 2 — we need to assign labels.

But in Diagram 1, the cell body is in the middle, with long dendrites at top and long axon at bottom.

That’s typical of a sensory neuron.

In Diagram 2, cell body near top, long axon down, few dendrites — motor neuron.

In Diagram 3, short axon and dendrites — relay neuron.

So:

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✔ Final Answers:

#### 1) A sensory neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon (or possibly axon terminals, but not in list — so axon is fine)

Wait — but e is at the end — could it be axon? Yes.

But d and e both point to axon? That’s okay — different parts.

But b is myelin sheath, correct.

But c — is it cell body or nucleus?

The arrow points to the whole cell body, and the dot is the nucleus.

But the label is c, and it's pointing to the structure — so cell body.

Similarly, in Diagram 2, c is cell body.

But in Diagram 3, h is cell body.

Now, f and g in Diagram 3:
- f: dendrite
- g: axon
- h: cell body

But f and g are two separate labels — so we must choose.

Yes.

Now, the word list includes nucleus — but no arrow points to it directly.

So likely, nucleus is not needed for labeling — or perhaps c is nucleus?

But c is pointing to the whole cell body, not the nucleus.

So probably, nucleus is not required here.

Unless the dot is labeled — but it’s not.

So we proceed.

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✔ Complete Answer:

#### 1) A sensory neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

> Wait — but e is the axon terminal — but only axon is in the list.

So e = axon

Okay.

But now, d and e both say axon — but that’s acceptable.

Alternatively, maybe d is myelin sheath?

No — b is clearly the myelin sheath (white segments), d is the axon.

Yes.

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#### 2) A motor neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

Same issue.

But e is the end — still axon.

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#### 3) A relay neuron
- f: dendrite
- g: axon
- h: cell body

Now, we have three neurons:

1. Sensory
2. Motor
3. Relay

And the labels:

| Letter | Label |
|--------|---------------|
| a | dendrite |
| b | myelin sheath |
| c | cell body |
| d | axon |
| e | axon |
| f | dendrite |
| g | axon |
| h | cell body |

But e and d both axon — okay.

But wait — in Diagram 1, d is the axon, e is the axon terminal — but we label it axon.

Similarly in Diagram 2.

Now, is there any chance that c is nucleus?

No — the arrow is to the whole cell body, not the nucleus.

So c = cell body

But the nucleus is inside — not labeled.

So nucleus is not used.

But the word list includes it — perhaps for another purpose?

Maybe f or g?

No.

Perhaps in Diagram 3, h is nucleus?

No — arrow points to the whole cell body.

So likely, nucleus is not used.

But maybe c is nucleus?

But the label is c, and it’s pointing to the cell body.

So cell body is correct.

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✔ Final Answer:

#### 1) A sensory neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

#### 2) A motor neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

#### 3) A relay neuron
- f: dendrite
- g: axon
- h: cell body

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✔ Summary of Labels:

| Letter | Label |
|--------|------------------|
| a | dendrite |
| b | myelin sheath |
| c | cell body |
| d | axon |
| e | axon |
| f | dendrite |
| g | axon |
| h | cell body |

And the neuron types:
1. Sensory
2. Motor
3. Relay

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❓ Why not use "nucleus"?

Because no arrow points directly to the nucleus — only to the cell body.

So we use cell body for c and h.

The nucleus is part of the cell body.

So it's acceptable.

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✔ Final Answer Boxed:

1) A sensory neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

2) A motor neuron
- a: dendrite
- b: myelin sheath
- c: cell body
- d: axon
- e: axon

3) A relay neuron
- f: dendrite
- g: axon
- h: cell body

> Note: The word nucleus is in the list but not used, as no label points directly to it. All other words are used.

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