Action Potentials - A Short Quiz

Be bold with your answers. The knowledge you construct defines you.

1. What ion enters a neuron causing depolarization of the cell membrane?
   1. sodium
   2. chloride
   3. potassium
   4. phosphate
2. Voltage-gated Na+ channels open upon reaching what state?
   1. resting potential
   2. threshold
   3. repolarization
   4. overshoot
3. What does a ligand-gated channel require in order to open?
   1. increase in concentration of Na+ ions
   2. binding of a neurotransmitter
   3. increase in concentration of K+ ions
   4. depolarization of the membrane
4. What does a mechanically gated channel respond to?
   1. physical stimulus
   2. chemical stimulus
   3. increase in resistance
   4. decrease in resistance
5. Which of the following voltages would most likely be measured during the relative refractory period?
   1. +30 mV
   2. 0 mV
   3. -45 mV
   4. -80 mV
6. Which of the following is probably going to propagate an action potential fastest?
   1. a thin, unmyelinated axon
   2. a thin, myelinated axon
   3. a thick, unmyelinated axon
   4. a thick, myelinated axon
7. What does it mean for an action potential to be an “all or none” event?
   The cell membrane must reach threshold before voltage-gated Na+ channels open. If threshold is not reached, those channels do not open, and the depolarizing phase of the action potential does not occur, the cell membrane will just go back to its resting state.
8. The conscious perception of pain is often delayed because of the time it takes for the sensations to reach the cerebral cortex. Why would this be the case based on propagation of the axon potential?
   Axons of pain sensing sensory neurons are thin and unmyelinated so that it takes longer for that sensation to reach the brain than other sensations.
9. The “fluid” and “mosaic” terms in the fluid mosaic model of membrane structure refer to the ___ and ___, respectively.
   A. inside of the membrane; outside of the membrane
   B. lipids; proteins
   C. proteins; lipids
   D. fatty acid chains; polar groups
10. Which of the following proteins is likely to contain one or more hydrophobic segments, 20-30 amino acids long?
    A. Integral membrane protein.
    B. Peripheral membrane protein.
    C. Lipid-anchored protein.
    D. Cytoplasmic protein.
11. Which of the following would most readily cross a lipid bilayer by simple diffusion?
    A. Oxygen
    B. Glucose
    C. Chloride ions
    D. Proteins
12. The voltage-gated potassium channels associated with an action potential provide an example of what type of membrane transport?
    A. Simple diffusion.
    B. Facilitated diffusion.
    C. Coupled transport.
    D. Active transport.
13. You are studying the entry of a small molecule into red blood cells. You determine the rate of movement across the membrane under a variety of conditions and make the following observations:
    i. The molecules can move across the membrane in either direction.
    ii. The molecules always move down their concentration gradient.
    iii. No energy source is required for the molecules to move across the membrane.
    iv. As the difference in concentration across the membrane increases, the rate of transport reaches a maximum.
    The mechanism used to get this molecule across the membrane is most likely:
    A. simple diffusion.
    B. facilitated diffusion.
    C. active transport.
    D. There is not enough information to determine a mechanism.
14. A particular cell has an internal chloride ion concentration of 50 mM, while outside the cell the chloride ion concentration is 100 mM. The free energy change associated with chloride transport into the cell (DG) is +970 cal/mol. Which choice below is the best explanation for this data?
    A. Cl- ion movement into the cell is energetically favorable.
    B. Both the concentration gradient and electrical gradient favor movement of Cl- ions into the cell.
    C. The concentration gradient for Cl- ions favors movement into the cell, but the electrical gradient opposes inward movement of Cl-.
    D. Both the electrical and chemical gradients for Cl- ions favor outward movement of Cl- ions.
15. Place the following steps in an action potential in the correct order.
    1. Sodium channels become inactivated and potassium channels are opened.
    2. Sodium and potassium channel gates are closed; membrane potential is –60mV.
    3. Sodium channel gates open in response to change in membrane potential.
    4. Potassium rapidly leaves the cell; membrane potential drops to –75mV.
    5. Sodium rushes into the cell; membrane potential reaches +40mV.
    A. 2, 1, 4, 3, 5, 2.
    B. 2, 1, 3, 4, 5, 2.
    C. 2, 3, 4, 1, 5, 2.
    D. 2, 3, 5, 1, 4, 2.
16. How are neurotransmitters released into a synapse in response to an action potential?
    A. They pass through voltage-gated neurotransmitter channels.
    B. They diffuse through the cell when the action potential reverses membrane potential.
    C. They pass through gap junctions into the post-synaptic cell.
    D. They are released by membrane fusion of vesicles in response to increased calcium concentration.
17. The neurotransmitter g-amino butyric acid (GABA) binds to receptors that are ligand-gated Cl- ion channels. What affect will this neurotransmitter have on the post-synaptic cell?
    A. Cl- ions will rush into the cell leading to hyperpolarization and a reduced likelihood of an action potential.
    B. Cl- ions will rush into the cell leading to depolarization and an increase in the chance for an action potential.
    C. Cl- ions bind to GABA and inhibit it from interacting with the receptor, stimulating an action potential.
    D. There will be no significant effect on the post-synaptic cell; only the pre-synaptic cell is affected by neurotransmitters.
18. Which of the following is the most likely immediate affect of G-protein activation?
    A. Receptors are stimulated to bind to their ligands.
    B. Enzymes are activated that catalyze second messenger formation.
    C. GTP is depleted from the cell.
    D. G-proteins bind to DNA and activate gene expression.
19. Proteins with SH2 domains are important in intracellular signaling pathways. What is the function of these domains?
    A. They bind to activated tyrosine kinase receptors.
    B. They bind to DNA and activate gene transcription.
    C. They regulate the activity of voltage-gated ion channels.
    D. They hydrolyze GTP to inactivate the pathway.
20. Platelet activation at the site of a wound is a example of:
    A. endocrine signaling.
    B. paracrine signaling.
    C. intracellular receptor activation.
    D. apoptosis.
21. Apoptosis is mediated by signal transduction pathways that lead to the programmed death of the cell. How is cell death achieved during apoptosis?
    A. Aqueous channels form in the cell membranes leading to inward movement of water and lysis of the cell.
    B. Gene expression is activated that leads to the synthesis of inhibitors of respiratory enzymes.
    C. The Na+/K+ ATPase is inactivated, leading to the loss of membrane potential which the cell needs to survive.
    D. Caspases are activated that lead to hydrolysis of many cellular macromolecules.
22. Which of the following statements is NOT true of tyrosine kinase-linked receptors?
    A. Monomeric receptors are often induced to dimerize upon ligand binding.
    B. The activated receptors attract and activate G proteins to continue the signal pathway.
    C. The cytoplasmic side of the receptor contains a kinase enzyme domain that is activated upon ligand binding.
    D. Activated receptors autophosphorylate themselves to attract SH2 domain proteins.
23. What mechanism is used to regulate the spontaneous assembly of collagen protein into a collagen fiber?
    A. Different fibroblasts secrete different components for each collagen fiber.
    B. Inhibitory protein domains are removed by an extracellular protease.
    C. Covalent cross-links between proteins are only made outside the cell.
    D. Complete collagen fibers are exported from the cell only as they are needed.
24. Which choice below describes the major function of proteoglycans in the extracellular matrix?
    A. They provide a hydrated, gel-like medium for lubrication, cushioning, and embedding other ECM components.
    B. They provide high strength fibers required to withstand mechanical stress.
    C. They provide a highly elastic support to resist tension.
    D. They create the dense, hard support structures of bone tissue.
25. Fibroblasts attach the extracellular matrix to the cytoskeleton via:
    A. focal adhesions.
    B. tight junctions.
    C. hemidesmosomes.
    D. gap junctions.

With the exception of this sentence the action potential and quiz is from; https://opentextbc.ca/anatomyandphysiology/chapter/12-4-the-action-potential