Reflex arc and myelin
Fri, Mar 19, 2027 · Week 9 · Human Anatomy & Physiology (Human Body Systems)
Today's goal: Trace a reflex arc and explain how myelin speeds signal conduction.
What a finished product looks like
This is a model of the work you should turn in today. Use it to check your own: match the structure and the level of detail, do not copy it. Your data and wording should be your own.
Reflex-arc components in order (with arrows):
1. Receptor (detects the stimulus, like a tap on the knee).
2. Sensory (afferent) neuron carries the signal toward the spinal cord.
3. Interneuron in the spinal cord processes it (this is the shortcut that skips the brain).
4. Motor (efferent) neuron carries the command back out.
5. Effector (the leg muscle) contracts.
Spinal-cord shortcut: I marked the loop at the spinal cord, because the response is triggered there before the brain is even aware of it, which is why reflexes are so fast.
Myelin explanation (two sentences): Myelin insulates the axon so the action potential jumps between the nodes of Ranvier instead of moving smoothly along the whole membrane. This saltatory (jumping) conduction lets signals travel up to about 70 m/s, far faster than the roughly 0.5 m/s in unmyelinated fibers.
Also due today: Submit a photo of your dated notebook page.
WebXam problem for today's skill
One exam-style question that uses exactly what you practiced today. Try it before you reveal the answer, then read why each choice is right or wrong.
Tap an answer to see the full explanation. Nothing is recorded or graded.