BiologyChapter 5: Nervous System of Man
5.3.6 Differences Between Myelinated and Non-Myelinated Neurons
Myelinated Neurons:
Explanation level
Neurons can be categorized based on the presence or absence of a myelin sheath around their axons. Myelinated neurons have a myelin sheath, while non-myelinated neurons do not. This difference affects the speed of nerve impulse transmission and other structural and functional characteristics.
Definition
Myelinated Neurons: Myelinated neurons are those that possess a myelin sheath around their axons. The myelin sheath is formed by Schwann cells.
Non-Myelinated Neurons: Non-myelinated neurons are those that do not possess a myelin sheath around their axons. The Schwann cells are present but do not wrap around the axon.
Main Idea
- The axons may be categorized into myelinated (with sheath) and non-myelinated (without sheath).
- Myelinated fibers are present in the white part of the brain and also in the spinal cord.
- Non-myelinated nerve fibers are present in the autonomic nervous system.
- Myelinated axons tend to be larger in diameter than non-myelinated axons.
- Myelinated neurons transmit nerve impulses very fast.
- Non-myelinated neurons transmit nerve impulses very slow.
Core Concept
- Myelinated neurons = possess myelin sheath
- Non-myelinated neurons = do not possess myelin sheath
- Myelin sheath = formed by Schwann cells
- White matter = myelinated fibers
- Grey matter = non-myelinated fibers
- Speed = myelinated: fast; non-myelinated: slow
- Diameter = myelinated: larger; non-myelinated: smaller
- Nodes of Ranvier = present in myelinated; absent in non-myelinated
- Collateral fibers = produced in myelinated; not produced in non-myelinated
Detailed Explanation
Differences Between Myelinated and Non-Myelinated Neurons
The axons may be categorized into myelinated (with sheath) and non-myelinated (without sheath).
| Feature | Myelinated Neuron | Non-Myelinated Neuron |
|---|---|---|
| Myelin sheath | They possess myelin sheath | These do not possess myelin sheath |
| Schwann cells | The Schwann cells show wrapping around the nerve axon | The Schwann cells do not show wrapping but are only present in the groove |
| Sheaths | This shows two sheaths in the axis of the cylinder | This shows only one sheath in the axis of the cylinder |
| Impulse transmission | These transfer nerve impulses very fast | These transfer nerve impulses very slow |
| Appearance | These appear white in their fresh form | These appear grey in their fresh form |
| Nodes and internodes | They possess nodes and internodes | These do not possess nodes and internodes |
| Nodes of Ranvier | Nodes of Ranvier are known to be present in these neurons | Nodes of Ranvier are not present in these |
| Collateral fibres | Collateral fibres are produced | Collateral fibres are not produced |
Location of Myelinated and Non-Myelinated Neurons
| Neuron Type | Location |
|---|---|
| Myelinated | White part of the brain; spinal cord |
| Non-myelinated | Autonomic nervous system |
Diameter of Axons
- Myelinated axons tend to be larger in diameter than non-myelinated axons.
Intermediate Level
Comparison of Myelinated and Non-Myelinated Neurons
| Feature | Myelinated Neuron | Non-Myelinated Neuron |
|---|---|---|
| Myelin sheath | Present | Absent |
| Schwann cells | Wrap around axon | Present in groove; no wrapping |
| Sheaths | Two sheaths | One sheath |
| Impulse speed | Very fast | Very slow |
| Appearance | White | Grey |
| Nodes and internodes | Present | Absent |
| Nodes of Ranvier | Present | Absent |
| Collateral fibres | Produced | Not produced |
| Location | White matter of brain; spinal cord | Autonomic nervous system |
| Diameter | Larger | Smaller |
Detailed Features
| Feature | Description |
|---|---|
| Myelin sheath | Insulating layer around axon |
| Schwann cells | Cells that form myelin sheath |
| Nodes of Ranvier | Gaps between myelin sheath segments |
| Internodes | Segments between nodes |
| Collateral fibres | Side branches from axon |
Speed of Impulse Transmission
| Neuron Type | Speed |
|---|---|
| Myelinated | Very fast |
| Non-myelinated | Very slow |
Formula / Mathematical Form
Not applicable to this topic.
Solved Example
Not applicable to this topic (descriptive topic).
Important Points
- 1. Axons are categorized into myelinated and non-myelinated.
- 2. Myelinated neurons possess myelin sheath.
- 3. Non-myelinated neurons do not possess myelin sheath.
- 4. Myelin sheath is formed by Schwann cells.
- 5. Schwann cells wrap around axon in myelinated neurons.
- 6. Schwann cells do not wrap around axon in non-myelinated neurons.
- 7. Myelinated neurons have two sheaths.
- 8. Non-myelinated neurons have one sheath.
- 9. Myelinated neurons transmit impulses very fast.
- 10. Non-myelinated neurons transmit impulses very slow.
- 11. Myelinated neurons appear white.
- 12. Non-myelinated neurons appear grey.
- 13. Myelinated neurons have nodes and internodes.
- 14. Non-myelinated neurons do not have nodes and internodes.
- 15. Myelinated neurons have Nodes of Ranvier.
- 16. Non-myelinated neurons do not have Nodes of Ranvier.
- 17. Myelinated neurons produce collateral fibres.
- 18. Non-myelinated neurons do not produce collateral fibres.
- 19. Myelinated neurons are in white matter of brain and spinal cord.
- 20. Non-myelinated neurons are in autonomic nervous system.
- 21. Myelinated axons are larger in diameter.
- 22. Non-myelinated axons are smaller in diameter.
Remember
- - Myelinated neurons = possess myelin sheath
- - Non-myelinated neurons = do not possess myelin sheath
- - Myelin sheath = formed by Schwann cells
- - White matter = myelinated fibers
- - Grey matter = non-myelinated fibers
- - Speed = myelinated: fast; non-myelinated: slow
- - Diameter = myelinated: larger; non-myelinated: smaller
- - Nodes of Ranvier = present in myelinated; absent in non-myelinated
- - Collateral fibers = produced in myelinated; not produced in non-myelinated
- - Location = myelinated: white matter; non-myelinated: autonomic nervous system
Common Mistakes
- 1. Confusing myelinated and non-myelinated neurons — Myelinated = myelin sheath; non-myelinated = no myelin sheath.
- 2. Thinking non-myelinated neurons have no Schwann cells — They have Schwann cells but they do not wrap around the axon.
- 3. Mixing up the speed — Myelinated = fast; non-myelinated = slow.
- 4. Confusing the appearance — Myelinated = white; non-myelinated = grey.
- 5. Mixing up the nodes — Myelinated = nodes and internodes; non-myelinated = no nodes.
- 6. Forgetting the Nodes of Ranvier — Present in myelinated; absent in non-myelinated.
- 7. Mixing up the locations — Myelinated = white matter; non-myelinated = autonomic nervous system.
- 8. Confusing the diameter — Myelinated = larger; non-myelinated = smaller.
- 9. Forgetting collateral fibres — Produced in myelinated; not produced in non-myelinated.
- 10. Thinking all neurons are myelinated — Some neurons are non-myelinated.
Quick Revision
The axons may be categorized into myelinated (with sheath) and non-myelinated (without sheath). The myelinated fibers are present in the white part of the brain and also in the spinal cord, while the non-myelinated nerve fiber is present in the autonomic nervous system. Myelinated axons tend to be larger in diameter than the non-myelinated axons. Myelinated neurons possess myelin sheath; non-myelinated neurons do not possess myelin sheath. The Schwann cells show wrapping around the nerve axon in myelinated neurons; the Schwann cells do not show wrapping but are only present in the groove in non-myelinated neurons. Myelinated neurons show two sheaths in the axis of the cylinder; non-myelinated neurons show only one sheath in the axis of the cylinder. Myelinated neurons transfer nerve impulses very fast; non-myelinated neurons transfer nerve impulses very slow. Myelinated neurons appear white in their fresh form; non-myelinated neurons appear grey in their fresh form. Myelinated neurons possess nodes and internodes; non-myelinated neurons do not possess nodes and internodes. Nodes of Ranvier are known to be present in myelinated neurons; Nodes of Ranvier are not present in non-myelinated neurons. Collateral fibres are produced in myelinated neurons; collateral fibres are not produced in non-myelinated neurons.
60-Second Revision
- Myelinated neurons = possess myelin sheath
- Non-myelinated neurons = do not possess myelin sheath
- Myelin sheath = formed by Schwann cells
- White matter = myelinated fibers
- Grey matter = non-myelinated fibers
- Speed = myelinated: fast; non-myelinated: slow
- Diameter = myelinated: larger; non-myelinated: smaller
- Nodes of Ranvier = present in myelinated; absent in non-myelinated
- Collateral fibers = produced in myelinated; not produced in non-myelinated
- Location = myelinated: white matter; non-myelinated: autonomic nervous system
- Warning: Myelinated neurons transmit impulses fast; non-myelinated neurons transmit impulses slow
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Review the key facts, formulas and checks before you move on.5.3.6 Differences Between Myelinated and Non-Myelinated Neurons
Sticky Notes · Quick Revision
Key Point 1
- Myelinated neurons = possess myelin sheath
Key Point 2
- Non-myelinated neurons = do not possess myelin sheath
Key Point 3
- Myelin sheath = formed by Schwann cells
Key Point 4
- White matter = myelinated fibers
Key Point 5
- Grey matter = non-myelinated fibers
Key Point 6
- Speed = myelinated: fast; non-myelinated: slow
Key Point 7
- Diameter = myelinated: larger; non-myelinated: smaller
Key Point 8
- Nodes of Ranvier = present in myelinated; absent in non-myelinated
Key Point 9
- Collateral fibers = produced in myelinated; not produced in non-myelinated
Key Point 10
- Location = myelinated: white matter; non-myelinated: autonomic nervous system
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