Neuron Anatomy 4. Draw a “typical” multipolar neuron in the space below. Include and label the following structures on your diagram: cell body, nucleus, dendrites, axon, myelin sheath, and myelin sheath gaps. 5. How is one-way conduction of nerve impulses ensured? 6. What anatomical characteristic determines whether a particular neuron is classified as unipolar, bipolar, or multipolar? Make a simple line drawing of each type here. Unipolar neuron Bipolar neuron Multipolar neuron 7. Describe how the Schwann cells form the myelin sheath encasing an axon. (You may want to diagram the process.)
The correct answer and explanation is:
Answers and Explanations
4. Diagram of a Multipolar Neuron:
Here is a typical multipolar neuron structure with labels:
- Cell Body (Soma): Contains the nucleus and cytoplasm.
- Nucleus: Controls cellular activities, including gene expression.
- Dendrites: Branch-like structures that receive signals from other neurons.
- Axon: A long projection that transmits electrical signals away from the cell body.
- Myelin Sheath: Fatty covering around the axon that increases the speed of impulse transmission.
- Myelin Sheath Gaps (Nodes of Ranvier): Small gaps between myelin sheath segments where action potentials are regenerated.
(If you’d like a visual drawing, I can create one for you.)
5. How is one-way conduction of nerve impulses ensured?
One-way conduction is ensured by:
- Anatomy of the Synapse: Neurotransmitters are released from synaptic vesicles in the presynaptic neuron and bind to receptors on the postsynaptic neuron. This ensures the signal moves in one direction.
- Refractory Period: After an action potential, the neuron enters a refractory period, preventing the immediate reversal of the impulse.
- Unidirectional Ion Channels: Voltage-gated sodium channels open and close sequentially along the axon, propagating the impulse in one direction.
6. Neuron Classification Based on Anatomy:
- Unipolar Neuron: Has a single process extending from the cell body, splitting into peripheral and central branches (e.g., sensory neurons).
- Bipolar Neuron: Has two processes (one axon and one dendrite) extending from opposite ends of the cell body (e.g., in the retina).
- Multipolar Neuron: Has one axon and multiple dendrites (e.g., motor neurons).
7. Formation of Myelin Sheath by Schwann Cells:
Schwann cells wrap around the axon in the peripheral nervous system, forming the myelin sheath:
- Wrapping: The Schwann cell wraps its membrane around the axon multiple times.
- Compaction: Layers of membrane become tightly compacted, excluding cytoplasm, forming a dense insulating sheath.
- Myelinated Axon: This insulation speeds up nerve impulse conduction via saltatory conduction at the Nodes of Ranvier.
Would you like a diagram for the neuron classifications or Schwann cell process?