1. A sea urchin egg is used in a voltage clamp experiment; that is, the value of the transmembrane voltage is set by the experimenter, not by the properties of the membrane.
The transmembrane voltage is held at +10 mV for one minute. At the end of that time
A. the voltage-gated calcium channels are all open.
B. the voltage-gated calcium channels are all inactivated.
C. the voltage-gated calcium channels have recovered from inactivation.
D. the voltage-gated calcium channels are going through cycles of opening and inactivation as the
cell generates repetitive action potentials.
E. any of answer A though D above could occur, depending on the density of potassium channels.
2. In a calcium action potential
A. the influx of calcium ions depolarizes the plasma membrane.
B. depolarization of the plasma membrane opens voltage-gated calcium channels.
C. open voltage-gated calcium channels carry an inward current of calcium ions.
D. an inward current of calcium ions aIDs positive charge to the cytosol.
E. all of the above occur.
3. Action potentials in nerve cell axons last a much shorter time than action potentials in
sea urchin eggs because
A. sodium has only a single positive charge while calcium has two.
B. voltage-gated sodium channels are found only at the nodes, while voltage-gated calcium channels
are found over the entire surface of the egg cell.
C. sodium ions are removed rapidly from the cytosol by the Na+/K+ ATPase.
D. voltage-gated sodium channels inactivate more rapidly than do voltage-gated calcium channels.
E. calcium has a higher atomic weight than does sodium and therefore diffuses more slowly.
4. An action potential is being generated at the node of a myelinated axon. Which of the
following statements is false?
A. Sodium is entering the axon interior through voltage-gated sodium channels.
B. Potassium is leaving the axon interior through potassium channels.
C. Calcium is entering the axon interior through voltage-gated calcium channels.
D. A net inward current is flowing across the plasma membrane of the node.
E. Current is leaving the region of the node axially, through the cytosol of the nerve cell.
5. The nodes of a myelinated axon are spaced a distance apart of approximately
A. 1 nm.
B. 1 ?m.
C. 1 mm.
D. 1 cm.
E. 1 m.
6. A sperm can trigger an action potential in a sea urchin egg because
A. its cytosol contains a lot of calcium ions that, upon fertilization, rush into the egg.
B. its membrane contains ion channels that, upon fertilization, pass an inward current that depolarizes
the egg plasma membrane.
C. its membrane contains ion channels that, upon fertilization, pass an outward current that repolarizes
the egg plasma membrane.
D. its cytosol contains a chemical that tends to pop the voltage-gated calcium channels into an
E. its cytosol contains a protease that modifies the behavior of voltage-gated calcium channels in
the plasma membrane of the egg.
7. When a nerve cell axon is depolarized to threshold, the flow of potassium through
potassium channels in the plasma membrane is
A. outward, and of a greater absolute amplitude than at the resting voltage.
B. inward, and of a greater absolute amplitude than at the resting voltage.
C. outward, but of a smaller absolute amplitude than at the resting voltage.
D. inward, but of a smaller absolute amplitude than at the resting voltage.
Why Choose Us
Top quality papers
We always make sure that writers follow all your instructions precisely. You can choose your academic level: high school, college/university or professional, and we will assign a writer who has a respective degree.
Professional academic writers
We have hired a team of professional writers experienced in academic and business writing. Most of them are native speakers and PhD holders able to take care of any assignment you need help with.
If you feel that we missed something, send the order for a free revision. You will have 10 days to send the order for revision after you receive the final paper. You can either do it on your own after signing in to your personal account or by contacting our support.
All papers are always delivered on time. In case we need more time to master your paper, we may contact you regarding the deadline extension. In case you cannot provide us with more time, a 100% refund is guaranteed.
Original & confidential
We use several checkers to make sure that all papers you receive are plagiarism-free. Our editors carefully go through all in-text citations. We also promise full confidentiality in all our services.
24/7 Customer Support
Our support agents are available 24 hours a day 7 days a week and committed to providing you with the best customer experience. Get in touch whenever you need any assistance.
Try it now!
How it works?
Follow these simple steps to get your paper done
Place your order
Fill in the order form and provide all details of your assignment.
Proceed with the payment
Choose the payment system that suits you most.
Receive the final file
Once your paper is ready, we will email it to you.
No need to work on your paper at night. Sleep tight, we will cover your back. We offer all kinds of writing services.
You are welcome to choose your academic level and the type of your paper. Our academic experts will gladly help you with essays, case studies, research papers and other assignments.
Admission help & business writing
You can be positive that we will be here 24/7 to help you get accepted to the Master’s program at the TOP-universities or help you get a well-paid position.
Editing your paper
Our academic writers and editors will help you submit a well-structured and organized paper just on time. We will ensure that your final paper is of the highest quality and absolutely free of mistakes.
Revising your paper
Our academic writers and editors will help you with unlimited number of revisions in case you need any customization of your academic papers