Learning Objectives for Bio220 AUT 2022 Unit Two - Electrical Signaling You should be able to: 1. Compare and Contrast a. passive transport, primary active transport, and secondary active transport b. electrical gradient, electrochemical gradient, and concentration (chemical) gradient c. equilibrium potential and resting membrane potential d. graded potentials and action potentials
2. Use Flow Diagrams to explain a. How receptor potentials are generated and lead (or don't lead) to action potentials in sensory neurons. b. How action potentials propagate. C. d.
potentials.
3. Use the Nernst equation to calculate equilibrium potentials and the magnitude of the electrochemical gradients.
4. Use Flux Reasoning ("gradient" / "resistance") to explain the direction and rate of movement of ions from one location to another.
5. Use Mass Balance Reasoning to explain the concentration of molecules in synapses and inside cells.
6.
Key Structures (vocabulary) Sensory neurons Interneurons (inhibitory, excitatory) Dendrites and cell body Trigger zone Axon Axon terminal Cell membrane lons Sodium ions (Na*) Potassium ions (K*) Chloride ions (CI) Calcium ions (Ca*+, Ca2+) Active and secondary active transport proteins Na*/K* pump (Na*/K* ATPase) NKCC1 (Na*/K+/CI triple transporter) KCC2 (K*/CI cotransporter) Ion channels Mechanosensitive ion channels Sodium leak channels (LNa*) Potassium leak channels (LK*) Voltage-gated sodium channels (VNa*) Voltage-gated potassium channels (VK*) Voltage-gated calcium channels (VCa**) Ionotropic neurotransmitter receptors (i.e., Ligand-gated ion channels) GABA receptor (GABAR) Glutamate receptor (GluR) Neurotransmitters Glutamate (Glu) gamma-Aminobutyric acid (GABA) Synapse Presynaptic membrane Neurotransmitter vesicles Synaptic cleft Postsynaptic membrane
Membrane Potentials Resting membrane potential Receptor membrane potential (a type of graded potential) Action potential Post-synaptic membrane potential (e.g., EPSP or IPSP) (a type of graded potential)
PRACTICE QUESTIONS
1. (6 pts) All living cells rely on to provide a continuous barrier between their cytosol and external fluid environments. One unique characteristic of this barrier is which allows for spatial separation of oppositely charged ions on either side. A second characteristic, unique to cells which transmit signals electrically, is active regulation of ion This regulation is partially
2. (12 pts) The figure to the right depicts a modeled Action Potential. Refer to the labeled points in the figure to answer the following:
+50
a) At what points are the voltage-gated K+ channels closed? (Circle all that apply) A B c D
E
Membrane Potential (mV) -50
b) At what points are the voltage-gated Na+ channels open? (Circ/e all that apply) A B c D
E
-100
c) At what points are K+ leak channels open? (Circ/e all that apply) ) A B
Time
c
D
E
d) At what points are the K+ leak channel flux and the Na+ leak channel flux equal to each other? (Circle all that apply) A B c D E
e) At what points is the membrane potential depolarizing? (Circle all that apply) A B c D
E
f) At what points is the membrane potential repolarizing? (Circle all that apply) A B c D
E
3. An imaginary mammalian cell at 37C' has an internal [CI-] of 16 mM that is