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NSCI 300 > FINAL > Flashcards

FINAL Flashcards

1
Q

What are 2 types of passive transport?

A
  • Channel-mediated
  • Transporter-mediated
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2
Q

What are 3 molecules that can cross the membrane, and 1 that can’t? (in order of most to least permeable)

A

Can cross the membrane: Hydrophobic molecules, Small Uncharged Polar Molecules, Large Uncharged Polar Molecules

Can’t cross the membrane: Ions

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3
Q

What is membrane potential?

A

The difference in charge across the membrane

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4
Q

What are the 3 electrical signals a neuron can generate?

A
  1. Receptor potentials: occurs when sensory neurons are activated by external stimuli like light, sound, or heat, altering their resting membrane potential
  2. Synaptic potentials: arise during neuron-to-neuron communication at synaptic junctions, facilitating the transfer of information between them
  3. Action potentials: Specialized signals that travel along the neuron’s axon, playing a crucial role in rapid signal transmission
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5
Q

Describe the 2 amplifiers used in the voltage-clamp experiment

A
  • amplifier measuring membrane potential of axon
  • feedback amplifier that compares the desired potential (command voltage) with the actual membrane potential, and injects necessary current to maintain desired potential
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6
Q

What is passive and active conduction?

A
  • Passive conduction: decays over distance
  • Active conduction: constant over distance
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7
Q

What happens when you inject an external depolarizing current into an axon?

A

Can result in the initiation and propagation of an action potential in both directions

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8
Q

How is the unidirectional propagation of action potentials ensured?

A

By the inactivation of voltage-gated Na+ channels during the refractory period.

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9
Q

Describe the 4 phases of the action potential

A
  1. Resting Phase: Neuron is at resting potential
  2. Depolarization Phase: Membrane potential becomes less negative, moves towards a positive charge
  3. Repolarization Phase: Membrane potential returns back towards the negative
  4. Hyperpolarization Phase: Membrane potential temporarily becomes more negative than the resting level
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10
Q

What 2 things contribute to speed up conduction velocity?

A
  1. Myelin sheath
  2. Axon diameter
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11
Q

What is Electric Charge (Q)?

A

The physical property of matter that causes it to experience a force when placed in an electromagnetic field. The unit is coulomb (C).

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12
Q

What is Voltage (V)?

A

The potential difference in electrical charge between two points. The unit is volt (V).

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13
Q

What is Current (I)?

A

Flow rate of electric charge. The unit is ampere (A). 1A = 1C/sec

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14
Q

What is Resistance (R)?

A

A force that counteracts the flow of electrical charge (current). The unit is ohm (ohms).

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15
Q

What is Conductance (g) and what is membrane conductance?

A

Conductance is inverse of resistance. The unit is siemens (S). Membrane conductance is a property of membrane that determines how much charge can go through the membrane.

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16
Q

What is Capcitance (C)?

A

Ability of a substance to hold an electric charge. The uni is farad (F). Depends on the surface areas, distance between two surfaces, and permeability of the insulator.

17
Q

What tools are needed for cellular electrical signal measurement? (3)

A

Requires sophisticated and specific equipment:
- Microelectrodes
- Amplifiers
- Units for data acquistion and analysis

18
Q

How do you place the microelectrode into the microelectrode holder?

A
  • Ensure to turn the screw cap counterclockwise before you insert (or remove) the electrode
  • After placing the electrode, rotate the screw cap clockwise to create a secure seal, but be careful not to tighten it excessively.
19
Q

What should you make sure to do before starting to use the micromanipulators (after setting up the equipment)?

A

Ensure that all the control knobs are positioned at the midpoint of their range.

20
Q

What are 4 features of a stereomicroscope?

A
  • Uses low magnification
  • Used for vieweing opaque specimens
  • Has a high working distance
  • Ideal for viewing dissections/3D objects
21
Q

What are 4 features of a compound microscope

A
  • Uses high magnification
  • Used for viewing transparent specimens
  • Has a small working distance (0.14 - 4mm)
  • Ideal for ultra-thin samples that you can pass light through (can’t see 3D)
22
Q

What is signal conditioning?

A

The process of amplification and then filtering an analog voltage signal that fluctuates over time.

23
Q

What are the 5 steps to follow for stereo microscope adjustment?

A
  1. Ensure that both diopter rings are set in the middle of their range
  2. Look through the right eyepiece with your right eye and adjust the focus using the “FOCUS CONTROL” knob
  3. Look through left eyepiece with left eye, and adjust focus using the “DIOPTER ADJUSTMENT RING”
  4. Finally adjust the distance between the eyepieces until you observe the SAME FIELD with both eyes.
  5. Whenever, you change the magnification, adjust the focus using the focus control knob, NOT THE DIOPTER ADJUSTMENT RING.
24
Q

How does increasing K+ concentration (hyperkalemia) in external fluids affect the cell’s potential?

A

The cell will depolarize initially and increase in excitability of neurons and muslces, but after a while, they may become inexcitable due to the inactivation of Ca2+ and Na+ channels. They then produce small or no action potentials.

25
Q

How does decreasing K+ concentration (hypokalemia) in external fluids affect cells?

A

The cell will hyperpolarize and become less excitable (make it harder to generate action potentials), causing muscle weakness and potential failure of resipiratory and heart muscles.

26
Q

Which amplifier do you use for intracellular recordings, and which one do you use for extracellular recordings?

A
  • DC Amplifier: Intracellular
  • AC/DC Differential Amplifier: Extracellular
27
Q

Why do we use DC amplifier for intracellular recording?

A

The DC amplifier is a high resistance amplifier, which means it significantly reduces the current flowing in the circuit, and thus minimize the alteration of ionic environment of the cell.

28
Q

Why do we use Ag/AgCl electrodes?

A
  • Ag has the highest electrical conductivity of all metals and it does not spark easily
  • Ag/AgCl electrodes are very stable and considered essentially non-polarized.
29
Q

What happens if the electrode resistance is recorded to be less than 5 MOhms?

A

The electrode is probably broken

30
Q

What happens if the electrode resistance is recorded to be more than 30 MOhms?

A

Electrode may be blocked

31
Q

Describe the dissection process of the crayfish (3 Steps) and the equipment for each step

A
  1. Remove head (Big scissor)
  2. Remove swimmerets (Small scissor, Coarse Forcep)
  3. Remove skin (Fine Forcep, Scalpel, Vannas Scissor)
32
Q

What are the 4 challenges and limitations of intracellular recording?

A
  1. Technical complexity: intracellular recording requires precise techniques and skilled handling
  2. Stability issues: Maintaining the stability of the recording over time is challenging.
  3. Risk of Damage: There is a risk of damaging the cell during electrode insertion, which can alter its natural functioning and affect the accuracy of data.
  4. Limited Duration: Due to the invasive nature of the technique, recordings are generally limited in duration, as prolonged electrode presence can compromise cell health.
33
Q

What are the 3 Rs regarding Animal Research?

A
  • Replacement: Full replacement (includes use of human volunteers, established cell lines, computer models), Partial replacement (using certain invertebrates that are thought not to feel suffering, based on current science, also includes cells/tissues from animals not used in painful experiments)
  • Reduction
  • Refinement
34
Q

What are 4 reasons to use a crayfish model?

A
  • Dissection is relatively easy for learning dissection techniques for live preparation
  • Muscle is stable for several hours in a minimal normal saline
  • Muscle preparation is fairly robust when external K+ concentration is altered for short time periods.
  • Due to large muscle size, it is relatively easy to obtain stable intracellular recordings.
35
Q

What is the Nernst equation?

A

EX = (R * T) / (F *z) ln([X]o / [X]i)

NSCI 300 (1 decks)

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