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Human A&P BIO 304 · American River College ← Course home (Week 4)

BIO 304 . WEEK 4 . THURSDAY . LAB WORKBOOK

Neurons and Resting Membrane Potential

Neuron anatomy, glia, and how the resting potential is built and maintained.

Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.

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Part 1 of 2

Anatomy Lab

1A. What you will draw

Two drawings today. Box A is a labeled neuron. Box B is a close-up of a patch of resting membrane showing the pumps, channels, and ion distribution responsible for the resting potential.

Box A. The neuron

Directions

  1. Draw a cell body (soma) as an irregular circle. Show a nucleus inside.
  2. Add 3 to 5 short branched dendrites projecting from the soma.
  3. Extend a single long process from the opposite side. Label its base Axon hillock.
  4. Wrap the axon with discrete myelin segments. Show at least 2 unmyelinated gaps. Label one gap Node of Ranvier.
  5. Identify which cell type makes the myelin: if CNS, an oligodendrocyte; if PNS, a Schwann cell. Pick one and label it.
  6. End the axon in several axon terminals (small swellings). Label one.

Box B. Resting membrane close-up

Directions

  1. Draw a horizontal rectangle representing a patch of plasma membrane. Label the top Outside (extracellular) and the bottom Inside (cytoplasm).
  2. Draw a Na-K ATPase pump straddling the membrane. Show arrows: 3 Na-plus leaving the cell, 2 K-plus entering, ATP being consumed.
  3. Draw at least 2 K-plus leak channels in the membrane. Show K-plus leaking OUT down its gradient.
  4. On the outside, write a large Na-plus and a small K-plus. On the inside, write a small Na-plus and a large K-plus. (Show which ion is more concentrated where.)
  5. Indicate charge: a row of minus signs lining the inside of the membrane and plus signs lining the outside.
  6. In the corner, write the resting potential value: about negative 70 millivolts.

1C. Structures to label (14)

After you finish each drawing, label every structure below directly on your sketch.

  1. Dendrites
  2. Cell body (soma)
  3. Nucleus
  4. Axon hillock
  5. Axon
  6. Myelin sheath
  7. Node of Ranvier
  8. Schwann cell or oligodendrocyte
  9. Axon terminal
  10. Na+/K+ ATPase
  11. K+ leak channel
  12. Na+ (high outside)
  13. K+ (high inside)
  14. Resting membrane potential (-70 mV)

Part 2 of 2

Physiology Lab

2A. Calculation: who builds the resting potential?

Use your Box B drawing as the reference. Answer each question. Show short work where math is involved.

1. Per ATP, the Na+/K+ ATPase moves 3 Na+ out and 2 K+ in. What is the NET charge moved across the membrane per cycle, and in which direction?
2. Does this NET pump activity make the inside more negative or more positive on its own? Explain.
3. The membrane is also leaky to K+. Which direction does K+ flow through these leak channels at rest, and why (give the gradient driving it)?
4. Of the two mechanisms (pump electrogenicity vs K+ leak), which contributes MORE to the -70 mV resting potential? Justify in one or two sentences.
5. Predict the resting potential of a cell that has lost ALL its K+ leak channels but still has a working Na+/K+ ATPase.

2B. Synthesis questions

Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.

1. Ouabain blocks the Na+/K+ ATPase. Predict the resting membrane potential at: (a) 5 seconds, (b) 5 minutes, (c) 5 hours after exposure. Explain the trajectory.
2. Match each glial cell to one function: astrocyte, oligodendrocyte, microglia, Schwann cell, ependymal cell. Pick from: makes myelin in CNS; makes myelin in PNS; immune surveillance; blood brain barrier support; produces CSF.
3. A neuron in cold seawater has a resting potential of -90 mV instead of -70 mV. Propose one mechanistic explanation involving the Na+/K+ ATPase or the K+ leak channels.

3. What to submit

Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.