A myelinated axon is 30 mm long. It is covered by segments of myelin sheath, each 2.5 mm long, laid…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A myelinated axon is mm long. It is covered by segments of myelin sheath, each mm long, laid end to end. The gap at a node of Ranvier is about wide, a standard value that NCERT does not give.
- How many segments of sheath are there?
- How many nodes of Ranvier lie between them?
- What is the total width of the nodes, in micrometres?
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.
Given. Axon: mm. Segment: mm. Node: .
Plan. Count the segments. The nodes are the gaps between them.
Step 1. Segments. .
Step 2. Nodes. The gaps lie between neighbouring segments, so there are nodes.
Step 3. Width of the nodes. .
Answer: ; ; .
Check. The nodes make about of the length, so nearly all the axon is covered by myelin.
Watch out. The two ends of the row have no neighbour, so they are not nodes.
More onHuman Body
Discussion (0)
Log in to join the discussion.
Loading…