Physioex 9.0 Exercise 3

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Activity 1
Pre-Lab Quiz
K+ inside a cell = 150 mM; K+ outside a cell = 5 mM
Na+ inside a cell = 5 mM; Na+ outside a cell = 150 mM
Stop & Think question
What is the polarity of the resting membrane potential (voltage)? Negative What does it mean that the voltage just inside the membrane is negative? B Membrane of most cells contains K+ leak channels…..b

What will happen to the resting membrane potential if the extracellular K+ concentration is increase? Less negative What happens to diffusion of K+ leaving the cell if you increase extracellular K+? decreases diffusion of K+ out of the cell Which way would Na+ move across the membrane if there wer open Na channels? A. into the cell The membrane has open K+ channels and changing….B. mostly closed Post-Lab Quiz

1. A negative membrane potential was recorded when the tip of the microelectrode was: a. In the extracellular solution just outside the cell body 2. Which of the following caused a change in membrane potential from -70 to -40 in the cell body? a. An increase in extracellular K+

3. Which of the following has the most negative voltage?
a. Between the outside of the axon and outside the cell body with control K+ ECF b. Between the outside of the axon and outside the cell body with High K+ ECF c. Between the inside of the axon and the outside of the axon with control K+ ECF d. Between the inside of the axon and the outside of the axon with High K+ ECF Activity 2

Pre-Lab Quiz
1 = c; 2= e; 3 = c; 4 = c
Stop& Think Questions
The adequate stimulus for a Pacinian corpuscle is pressure or vibration on the skin. Which of the following modalities will induce the largest amplitude receptor potential in the Pacinian corpuscle? C. moderate-intensity pressure Post-Lab quiz

1. A very intense stimulus can sometimes stimulate sensory neurons that have evolved for a different modality. Thus, with a blow to the eye, one “sees stars/” In this example the photoreceptors in the eyes are responding to: a. Pressure

2. Olfactory receptor neurons respond to low concentrations of chemical odorants b/c there are membrane proteins in the receptor ending of this sensory neuron that: b. Can bind & respond to the specific odorant

3. The sequence of events starting with a sensory stimulus & ending with a change in membrane potential is called: c. A sensory modality
d. Sensory transduction
4. Starting at a resting membrane potential of -70 mV, a change to which of the following represents the largest receptor potential? e. -80mV
f. -75
g. -60
h. -50
Activity 3
Pre-Lab Quiz
1 = d; 2 = a; 3 = d; 4 = a
Stop & Think Questions
Why is the action potential recorded by the 2nd recording electrode (R2) delayed relative to the action potential recorded by the 1st recording electrode (R1)? C. the action potential had to propagate from R1 to R2 How will the AP at R1 or R2 change as you continue to increase the stimulus voltage? Will not change???? An increase in extracellular K+ would ….B depolarize to near or above threshold Post-Lab Quiz

1. The threshold voltage in an axon is usually
a. Less negative than the resting membrane potential
b. More negative than the resting membrane potential
c. Achieved in the laboratory by applying -20 mV
d. The same value as the resting membrane potential
2. If a graded receptor potential made the resting membrane potential of the azon more negative (for example, -70 mV changes to -75 mV), you would expect e. It to be easier for this axon to reach the threshold voltage f. Subsequent action potentials to be shorter in duration g. No change in the ability of this axon to reach threshold voltage h. It to be more difficult for this axon to reach the threshold voltage 3. Failure to reach the threshold voltage in the axon of a sensory neuron could be caused by i. Generation...
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