Exercise 3: Neurophysiology of Nerve Impulses

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EXERCISE 3: Neurophysiology of Nerve Impulses
ACTIVITY 1: The Resting Membrane PotentialAnswers
1.The nervous system contains two general types of cells: neuroglia cells and a.nerves.
b.cell bodies.
c.neurons.
d.nephrons.
2.The resting membrane potential of the neuron in this lab under the control conditions was _______ mV. 3.True or False: For most neurons, the concentration of Na+ and K+ ions inside and outside the cell are the primary factors that determine the resting membrane potential. 4.Explain why increasing the extracellular K+ causes the membrane potential to change to a less negative value.

5.Discuss the relative permeability of the membrane to Na+ and to K+ in a resting neuron. 6.Discuss how a change in Na+ or K+ conductance would affect the resting membrane potential. ACTIVITY 2: Receptor Potential

7.The “receiving end” of a sensory neuron is called the sensory receptor. It has proteins that can generate a signal called the _________ potential when the sensory neuron is stimulated. 8.Which of the following is not a sensory modality?

a.taste
b.smell
c.touch
d.height
9.The maximum amplitude of response of the Pacinian corpuscle to pressure in this simulation was ____ mV. 10. Sensory neurons have a resting membrane potential based on the efflux of potassium ions (as demonstrated in Activity 1.) What passive channels are likely found in the membrane of the olfactory receptor, in the membrane of the Pacinian corpuscle, and in the membrane of the free nerve ending? 11. What is meant by the term graded potential?

12.Identify which of the stimulus modalities induced the largest amplitude receptor potential in the Pacinian corpuscle. 13.Identify which of the stimulus modalities induced the largest amplitude receptor potential in the olfactory receptors. 14.What type of sensory receptor would likely respond to a green light? ACTIVITY 3: The Action Potential: Threshold

15.In this lab simulation, what stimulus voltage first caused voltage to be seen at R1 and R2? _______ mV 16.True or False: A neuron must be polarized to the threshold voltage before an action potential is generated. 17.If the resting membrane potential of a neuron is -70mV and the threshold voltage of that neuron is -50 mV, then the neuron must be depolarized by a minimum of ______ mV before an action potential is generated. a.10mV

b.15mV
c.20mV
d.30mV
18.Define the term threshold as it applies to an action potential. 19.What change in membrane potential (depolarization or hyperpolarization) triggers an action potential? 20.How did the action potential at R1 (or at R2) change as you increased the stimulus voltage above the threshold voltage? 21.An action potential is an “all-or-nothing” event. What does this mean? ACTIVITY 4: The Action Potential: Importance of Voltage-Gated Na+ Channels 22.According to your lab manual, “voltage-gated” channels open when the cell membrane of the neuron ___________. 23.When Na+ ions flow through open channels into the neuron, then the membrane potential becomes a.more negative

b.less negative
c.closer to, at, or above the threshold voltage
d.both b. and c.
24.True or False: When a voltage-gated Na+ channel is closed, then the Na+ ions actually flow in the opposite direction than if the channel is open. 25.What does TTX do to voltage-gated Na+ channels?

26.What does lidocaine do to voltage-gated Na+ channels? How does its effect differ from the effect of TTX? 27.Why are fewer action potentials recorded at R2 when TTX is applied between R1 and R2? 28.Why are fewer action potentials recorded at R2 when lidocaine is applied between R1 and R2? 29.Pain-sensitive neurons (called nociceptors) conduct action potentials from the skin or teeth to sites in the brain involved in pain perception. Where should a dentist inject the lidocaine to block pain perception? ACTIVITY 5: The Action...
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