Lab Exam 1

Question 1

Passive Membrane:

Answer 1

the inherent construction and properties of a membrane that allow a neuron to store and propagate an impulse without the use of voltage-gated-channels

Question 2

Resistance:

What is the biological equivalent?

Answer 2

the impedance of charge flow

ion channels

Question 3

Capacitance:

What is the biological equivalent?

Answer 3

storage of charge

bilayer

Question 4

What are the axis labels for the RC curve?

Answer 4

x = time (s)
y = voltage (V)

Question 5

Time constant:

Answer 5

time it takes for the circuit to reach 63% of peak change in amplitude

Question 6

Formula: Time constant:

Answer 6

t x 0.63

Question 7

How would a stimulus curve look if only resistance (no capacitance) was involved?

Answer 7

a rectangular wave

Question 8

How do you determine the resistivity of a resistor?

Answer 8

calculation of the first three lines:

(when writing L to R)
number of the first-line color = the first number
number of the second-line color = the second number
number of the third-line color = the number of trailing zeroes

Question 9

How can you differentiate the different types of resistances when only given the amount?

Answer 9

Rm = highest value
Ri = mid value
Ro = lowest value

Question 10

Formula: Length constant:

Answer 10

length constant = sqrt(Rm/Ri + Ro)

Question 11

Length constant:

Answer 11

the distance it takes for the a signal to decay to 37% of its original state (delta voltage m)

Question 12

Increase/decrease in Rm results in ….

How can this be done?

Answer 12

I: increase in length constant (decreasing amount of channels)
D: decrease in length constant (increasing amount of channels)

Question 13

Increase/decrease Ri will result in ….

How can this be done?

Answer 13

I: decrease the length constant (decreasing the size)
D: increase the length constant (increasing the size)

Question 14

Increase/decrease in membrane capacitance will result it …

Answer 14

I: decrease length constant (removing myelin; smaller cell)
D: increasing length constant (adding myelin; larger cell)

Question 15

How can we change velocity (2)?

Answer 15

1. axon diameter (increase leads to greater velocity)

2. myelin (higher degree of myelination leads to greater velocity)

Question 16

In Lab 2, altering the concentration levels of extra and intracellular sodium leads to …

Answer 16

E: increase in amplitude
I: decrease in amplitude

Question 17

In Lab 2, altering the concentration levels of extra and intracellular potassium leads to …

Answer 17

E: decrease the AHP (smaller trough)
I: increase the AHP (bigger trough)

Question 18

Nerst Equation:

For the Chara plant what is the log ratio?

Answer 18

E = (61.514/z) log[(extracellular/intracellular)]

Chara plant: [pond water]/[cytoplasm]

Question 19

How can you tell the following was added during the simulation in Lab Two?

1. Na/K Pump
2. Leaky Channels
3. H-H

Answer 19

1. resting membrane voltage begins at -70 mV
2. starts at -70; dies out quickly and not a sharp slope
3. starts at -70; very rapid increase and decrease; recharges itself

Question 20

Why are crayfish the ideal model for studying excitatory muscular activity (4)?

Answer 20

1. simplistic reasons– muscles only have a few neurons (n3 there’s only 6)
2. multiterminal– motor neurons innervate muscle fiber at multiple points
3. polyneuronal– more than one motor neuron can innervate one muscle fiber
4. neuron are both inhibitory and excitatory

Question 21

How are you able to determine how many axons are present and how can you come to that conclusion?

Answer 21

each spike within the data represents an impulse from an axon; some of those peaks will be similar in height, indicating that the axon diameter is releasing another impulse

Question 22

Describe the process you used when dissecting a crayfish:

Answer 22

1. Place crayfish under ice for about 15 min
2. Cut thoracic section from the abdominal
3. Pin the tail down
4. Fill the dish with cold crayfish saline
5. Cut the mid section “I” shape
6. Add Janus Green nearby the open section

Question 23

What is the purpose of an action potential in a plant cell?

Answer 23

1. the large cells utilize cytoplasmic streaming to distribute nutrients throughout the cytoplasm
2. AP stop cytoplasmic streaming due to a response in deformation of the cell membrane

Question 24

What is the purpose of an Ohm’s test? What is the proper range? If it’s too high/too low, what does this mean?

Answer 24

to test the efficiency of a microelectrode

5-6 M-Ohms

H: air bubble
L: broken

Question 25

Differences between a mammalian species vs plants:

Answer 25

1. longer AP (seconds vs milliseconds)
2. larger AP (very negative RMP and very high amplitudes)
3. different ions contribute to the impulses falling and rising phases

Question 26

[…] contribute to a plant cells rising phase while […] contribute to the plant cells falling phase.

Answer 26

Ca2+ influx and Cl- efflux; K+ efflux