TABLE 12.1 Concentrations of major ions in intracellular fluid (cytoplasm) and extracellular fluid Squid axon Mammalian muscle lon type Out (mM) In (mM) Out/In Out (mM) In (mM) Out/In Na* 440 50 8.8 145 12 12.1 K* 20 400 0.05 4 155 0.03 560 60 9.3 120 3.8 31.6 A- (organic anions) 270 -

What proteins are responsible for membrane potential in section 1 potassium leak channels opening of potassium channels opening of ligand gated sodium channels Na+/K+ Atpase opening of sodium channels

Conduction velocity refers to the [a] at which an action potential travels along a neuron's axon. In invertebrates, conduction velocity can only be increased by [b]. However in vertebrates (exclusively), such as humans, conduction velocity can also be increased by [c]. This enables vertebrates to conserve [d] while still increasing conduction velocity. [a] [b] [c] [d] [Choose ] [Choose ] [Choose ] [Choose ]

Name and describe the roles of key molecules and membrane structures in maintaining axon membrane resting potential of-70 mV Name and describe the roles of key molecules and membrane structures in propagation of axon membrane action potentials during depolarization at +35 mV  Explain why they myelin sheath of white matter neurons allows faster action potential transmission than that of neurons found in gray matter.

The membrane potential labeled (0) is due to which of the following (when compared to (3) potential. (A) voltage-gated Na+ channels (B) voltage-gated K+ channels (C) voltage-gated slow Ca++ channels (D) voltage-gated fast Ca++ channels (E) voltage-gated transient Ca++ channels (F) funny channels

The membrane potential in animal cells, but not in plants, depends largely on resting K+ channels. How do these channels contribute to the resting membrane potential? Why are these channels considered to be nongated channels? How do these channels achieve selectivity for K+ versus Na+, which is smaller than K+?

In an experiment, it was determined that the motor (effector) neuron for muscle fibre 1 had a threshold level of –5 mV. The motor (effector) neuron for muscle fibre 2 had a threshold level of –16 mV. An electrical probe was used to stimulate these two effector neurons of the muscle fibres. Which of the following rows correctly identifies the reaction of each muscle fibre based on the applied stimulus voltage? a.  Stimulus Voltage  Muscle Fibre 1  Muscle Fibre 2 –10 mV Contracted Relaxed b.  Stimulus Voltage  Muscle Fibre 1  Muscle Fibre 2 –20 mV Relaxed Contracted c.  Stimulus Voltage  Muscle Fibre 1  Muscle Fibre 2 –10 mV Relaxed Contracted d.  Stimulus Voltage  Muscle Fibre 1  Muscle Fibre 2 –20 mV Contracted Relaxed

For each phase, again, name the phase. Then draw in the figures below: Na+ and K+ channels. Draw them open or closed as appropriate. Where Na+ and K+ ions are located If Na+ or K+ are moving, draw the direction that they move. Make sure they move through their appropriate ion channel.

Below is a figure from a 2015 paper that characterizes the effect of venom from the spider Selenocosmia hainana on voltage-gated sodium channels. According to the I-V curve (current-voltage curve) in Figure panel B, what is the effect of the venom on voltage-gated sodium channels? Current is on the y-axis and voltage is on the x-axis during an action potential. The figure legend denotes the concentration of the venom being applied. A C rHNTX-IV (10 μM) -rHNTX-IV (100 nM) Control Control 5 nA 10 ms r 5 nA 10 ms rHNTX- IV (10 μM) B D -80 -80 -60 -60 A -40 -40 V (mv) -20 V(mv) -20 be TOLF 2-6 I (NA) -8 ON -12 10 -12 -14 -8 -10 (NA) Control 100 nM — 10 μΜ 40 -Control -- 10 μM 40

What proteins are responsible for the decrease of membrane potential in section 3? opening of voltage gated sodium channels opening of voltage gated potassium channels potassium leak channels opening of ligand gated sodium channels Na+/ K+/atpase