Name the kind of each neuron, and say which of its processes brings the impulse to the cell body…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Name the kind of each neuron, and say which of its processes brings the impulse to the cell body.
- A neuron of the cerebral cortex with one axon and six dendrites.
- A neuron of the retina with one axon and one dendrite.
- A neuron of the embryo with a cell body and a single axon only.
- A student says that a neuron may have two axons and so be called bipolar. Is the student right?
Need a reminder? The key ideaShow
The CNS is the brain and the spinal cord. The PNS is the nerves. Afferent fibres bring impulses to the CNS, and efferent fibres carry them away. The somatic system serves skeletal muscles, and the autonomic system serves involuntary organs and smooth muscles. A multipolar neuron has one axon and two or more dendrites, a bipolar neuron has one axon and one dendrite, and a unipolar neuron has one axon only. Nodes of Ranvier lie between the parts of the myelin sheath.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) One axon and two or more dendrites: a multipolar neuron. The dendrites bring the impulse to the cell body.
Step 2. (b) One axon and one dendrite: a bipolar neuron. The dendrite brings the impulse in.
Step 3. (c) A cell body with one axon only: a unipolar neuron. It has no dendrite, so no process brings an impulse in.
Step 4. (d) The student is not right. In NCERT's classification, a neuron has one axon. The names depend on the number of dendrites: two or more for multipolar, one for bipolar, none for unipolar.
Answer: (a) multipolar; (b) bipolar; (c) unipolar; (d) no, a neuron has one axon.
Watch out. Do not call a neuron bipolar because it has two ends. It must have one axon and one dendrite.
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