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Neurophysiology > Neurophysiology Lecture 1 > Flashcards

Neurophysiology Lecture 1 Flashcards

1
Q

Key Features of Neurons

  1. How are they at rest?
    a. A Neuron is analogous to what?
    b. How is the inside relative to the outside?
    c. What is VOLTAGE?
  2. Stimuli induce changes in polarization
    a. Define Depolarization
    b. Define Hyperpolarization
A
  1. Electrically Polarized
    a. to a “Plus” and “minus” poles of a battery
    b. Negative
    c. Difference b/w Electrical Potential
  2. a. Cell potential becomes less negative, or even positive inside relative to the outside
    b. Cell potential becomes more negative
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2
Q

Key Features of Neurons (2)

  1. Changes in polarization can be transmitted throughout the cell
    a. How do neurons conduct voltage: Actively or Passively?
    b. They can also create a wave of voltage change. What is this called?
  2. Where do these changes get communicated to?
A
  1. a. Passively
    b. Action Potential
  2. Other neurons, Sensory Receptors, Muscle Cells
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3
Q

Electrophysiological Techniques

  1. 3 Types of recording
A
  1. a. Single Cell (Extra and Intracellular)
    b. Multiple Cell Recording
    c. Volume Recording (Non-invasive and Invasive)
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4
Q

Resting Potential

  1. What is it?
  2. When is there an Electrical Potential (voltage) involved?
  3. What 2 things will BALANCE each other?
  4. Potential Depends upon what 3 things?
A
  1. Gradients of Particles (Atom or molecules) across a membrane which PRODUCES OSMOTIC PRESSURE!
  2. If the particles producing the gradient are IONS.
  3. Electrical and Osmotic Pressure
  4. a. Charge of the ion (which pole of the battery you’re contacting)
    b. Size of the gradient (voltage of the battery)
    c. Ionic Permeability (how much current is flowing from the battery)
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5
Q

Relating Concentration to Potential

  1. Potential (E) depends on what?
  2. What is the Nernst Equation?
  3. Goldman Equation?
A
  1. a. Charge of the Ion (z)
    b. Ionic gradient (ratio of OUTSIDE to INSIDE)
    c. Permeability (P)
  2. It’s for a Single Ion Gradient
  3. It gives the Potential for Any combination of Ionic Gradients!
    * E = RT/(zF)*ln([ion outside cell]/[ion inside cell])
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6
Q
  1. Sodium
    a. Internal Concentration
    b. External Concentration
    c. Potential
A
  1. a. 10 mM
    b. 142 mM
    c. +70
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7
Q
  1. Potassium
    a. Internal Concentration
    b. External Concentration
    c. Potential
A
  1. a. 100
    b. 4
    c. -94
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8
Q
  1. Calcium
    a. Internal Concentration
    b. External Concentration
    c. Potential
A
  1. a. 0.25
    b. 2.4
    c. +120
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9
Q
  1. Chloride
    a. Internal Concentration
    b. External Concentration
    c. Potential
A
  1. a. 10
    b. 103
    c. -86

*HIGHER INTERNAL CONCENTRATION = Negative potential (higher than external)

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10
Q

Ionic Permeability

  1. How do Ions usually cross the membrane?
  2. Why are channels needed?
A
  1. Thru ION CHANNELS: Specialized proteins

2. due to membranes being primary lipid bilayers, and charged molecules aren’t very soluble in lipids.

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11
Q

Types of Ion Channels

  1. Leakage Channels
  2. VG Ion Channels
  3. Receptor-Linked (ligand-gated) Ion Channels
  4. G-Protein Coupled Ion Channels
A
  1. Always Open
  2. Open only at certain voltages
  3. Open in response to the stimulation of a neurotransmitter receptor
  4. Open in response to changes in the level of GTP
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12
Q

Resting Neuron Illustration

  1. What does each ion w/a concentration gradient act like?
  2. What does each Ion channel act like?
  3. At rest, why is the Potential (-75mV) close to that of POTASSIUM?
A
  1. A Battery
  2. A Resistor (Leakage) or a Switch (Other types)
  3. Cuz it has the greatest permeability (Current Flow)
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13
Q

Depolarization

  1. What is the threshold level?
    a. What does reaching this threshold do?
    b. What happens to the Cell’s potential at this point?
A
  1. A decrease in negative potential that reaches the threshold (+15 to +30 mV above resting voltage)
    a. Opens VG Sodium Channels (they now have high conductance)
    b. Cell’s Potential (+55mV) moves closer to that of Sodium
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14
Q

Repolarization

  1. What happens to Sodium Channels?
  2. and then…?
  3. What happens last?
A
  1. Spontaneously close (like turning off a switch)
  2. VG-Potassium channels open (after a delay) to repolarize, and hyperpolarize the cell (-80mV)
  3. Additional Potassium channels spontaneously close and the cell returns to resting potential, but it’s refractory to further stimulation (about 2 ms)
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15
Q

The Action Potential

  1. What is an Action potential?
A
  1. 1 Complete cycle of depolarization and repolarization

* Threshold change in resting potential –> Depolarization –> Repolarization –> Return to Resting Potential

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16
Q

Maintaining Ionic Gradients

  1. How are Ionic Gradients created?
  2. What pump is KEY for this?
    a. What does it use for energy?
    b. Exchanges what exactly?
    c. What does it do to K and Na concentrations?
  3. Active Process
    a. Uses what?
A
  1. pumping ions into or out of the cell (maintains them as well)
  2. Na/K ATPase is the key “pump”
    a. ATP
    b. Exchanges 3 Na+ ions from intracellular space for 2 K+ ions form the extracellular space using one ATP molecule
    c. Increases [K+]i and decreases [Na+]i
  3. a. Uses ATP or other stored energy that can be converted into ATP (Making ATP uses Glucose and Oxygen)
17
Q

Use of Glucose by the Brain

  1. Brain contains how many neurons?
  2. Brain weight vs weight of body?
A
  1. about 100 billion neurons (and about the same for support cells)
  2. Brain comprises only 2% of the weight of the body, it uses a disproportionate amount of metabolic resources. (25% of glucose; 20% of oxygen; 15% of cardiac output)
18
Q

Measuring Brain Activity with PET

  1. Brain areas more active take up more what?
  2. What is a patient given?
  3. Why does this work?
A
  1. Glucose
  2. 18F-DG (Positron emitter and is taken up the same way as glucose)
  3. DG can’t be metabolized, so it remains in Brain cells, where it gets imaged
19
Q

PET

  1. what does a PET scanner contain?
  2. What gamma rays are counted?
  3. How is a Positron produced?
  4. How are gamma rays produced?
  5. There’s uncertainty in the location of the tracer: Why?
  6. This uncertainty causes what?
A
  1. a CIRCULAR array of Gamma Ray Detectors
  2. only PAIRS of gamma rays emitted simultaneously and in opposite directions are counted
  3. Decay of 18F produces a positron
  4. Position collides with an electron, it produces 2 gamma rays moving in nearly opposite directions
  5. Positron can travel before annihilation and directions of gamma rays aren’t perfectly opposite
  6. Produces “Blur” in the imaging
20
Q

Brain Energy Use

  1. To maintain brain activity at the highest level, you would have to supply how many packets of sugar to the brain?
A
  1. About 3 packets of Sugar per hour directly to the brain.
21
Q

Ischemic Stroke

  1. What is it?
  2. Loss of oxygen does what?
    a. What is the problem with this? (3)
  3. Lose consciousness in how long?
  4. Permanent damage can occur in how long?
A
  1. Interruption of Blood Flow to the Brain
  2. Switches to Anaerobic Respiration
    a. Less Efficient
    b. Produces lactic Acid (can be toxic)
    c. interrupts aerobic respiration results in presence of free radicals
  3. 60s to 90s
  4. Permanent damage in minutes
22
Q

Ischemic Events in the Eye

  1. Symptoms? (3)
  2. Causes?
A
  1. a. None
    b. Amaurosis Fugax
    c. Sudden vision loss
  2. a. Vascular disease (diabetes, hypertension)
    b. Retinal Vein and artery occlusions
    c. AION, NAION, OIS
23
Q

The Action Potential

  1. What’s the first thing that needs to happen for an AP to be propagated along the neuron?
  2. Depolarization causes what?
  3. As this process continues, what will happen?
  4. The wave travels how?
A
  1. Local AP occurs
  2. a Slight decrease in potential of the Adjacent area. If that reaches threshold, an AP happens there too
  3. A Wave of depolarization and repolarization occurs
  4. in ONLY one Direction cuz Excited areas are briefly refractive to re-excitation
24
Q

AP vs. Graded Potential

  1. What is the normal way electrical potential is transmitted?
    a. how do they decay?
    b. Ohm’s Law?
    c. What does a graded potential depend on?
  2. APs are regenerative
    a. They’re BINARY: define
A
  1. Graded Potentials
    a. with Distance traveled
    b. V = I * R
    c. the Size of original Depolarization, its distance away, and its duration
  2. a. Either they occur or they don’t. (Have same general form anywhere along the axon)
    * “All or None.” Don’t reflect the size or location of the depolarization that generated them.
25
Q

Recording of APs

  1. What is used?
    a. What’s measured?
    b. APs have the Same what?
A
  1. Microelectrode
    a. Change in potential
    b. SAME FORM: either occur or don’t; and Rate can Vary
26
Q

Saltatory Conduction

  1. When one segment of the axon depolarizes, it depolarizes what else?
    a. Depolarization has limited extent: Why?
    b. AP moves how?
    c. Speed can be improved: How?
  2. Myelination: What does it do?
  3. Myelination allows what else?
A
  1. the next segment
    a. cuz the axon is not a good passive conductor
    b. in small steps so depolarization takes time at each step.
    c. by increasing the axon’s diameter (depolarization travels further)
  2. conducts depolarization further: 1 node depolarization is good enough to move rapidly, jumping b/w nodes
  3. allows axons to be smaller in diameter and faster in conduction
27
Q

Multiple Sclerosis

  1. What does it do?
  2. Why is this a problem?
  3. Presents how?
A
  1. demyelination lesions disrupt saltatory conduction
  2. Axonal areas under myelin sheath generally have FEW ion channels. AP may be slowed or blocked
  3. as optic neuritis: loss of vision, diplopia, nystagmus, ocular dysmetria
28
Q

Effect of NT on the Ach Receptor

  1. Binding of ACH causes what to happen?
  2. The change in position does what?
  3. What happens here?
A
  1. Causes 2 subunits to swivel around a disulfide bond
  2. of the subunits opens the channel
  3. sodium conductance increases, depolarizing the cell
29
Q

Gap Junctions

  1. Electrical signals can also be transmitted how?
  2. These contain what?
  3. Depolarization does what?
A
  1. without using chemicals…they form conductive tight connections called GAP JUNCTIONS
  2. Channels connecting the Fluid (cytoplasm) compartments of 2 cells
  3. depolarizing 1 cell is transmitted to the other cell thru the fluid connection (like electrical voltage being transmitted thru salt water)
30
Q

Receptors and Drugs

  1. Neurotransmitters recognize what?
  2. Drugs recognize what?
  3. Drugs can have diverse effects of a given receptor depending on how they alter its structure…how?
A
  1. a single type of receptor or a small number of different types
  2. a large number of different receptors (drugs will have multiple effects on the body; and when receptors have similar natural neurotransmitters, drugs that act at one will often have some effect at all)
  3. Agonist (Competitive and non-competitive) and Antagonist (reverse agonist)
31
Q

Effect of Drugs on Receptors

  1. 2 different drugs bind to AChBP: what does it do?
A
  1. Induces distinct structural changes: this leads to changes in the function of the receptor.
32
Q

Ocular drugs Act at Receptors

  1. Meiotics
  2. Midriatics
  3. Cycloplegics
  4. Antihistamines
  5. Most IOP lowering drugs
A
  1. Adrenergic and Cholinergic
  2. Cholinergic
  3. Adrenergic
  4. Histaminergic
  5. Adrenergic, Cholinergic, Prostaglandin
33
Q

Effects of Receptor Stimulation

  1. Opening of Ion Channels
    a. What leads to depolarization?
    b. Hyperpolarization?
  2. Increase or decrease in second messengers
    a. 2nd messengers are what?
    b. Why are they called them?
  3. Regulation of Gene Expression
    a. Produces what?
    b. Activation of what receptors can have this effect?
A
  1. a. Receptor linked Na channels open
    b. Opening receptor linked potassium or chloride channels
  2. a. small molecules, and can have multiple effects on cell function, including changes in polarization
    b. their levels are controlled by another agent (first messenger)
  3. a. long-term changes in cell function
    b. activation of hormone receptors
34
Q

Cyclic Nucleotides

  1. What are they?
  2. First messenger is usually what?
  3. What does this process do?
  4. Cyclic nucleotides will activate or deactivate what?
  5. Stimulation of a single receptor can do what?
A
  1. cAMP, cGMP, usually act as 2nd messengers, so does PI (phosphoinositol)
  2. a neurotransmitter binding to a receptor
  3. increases or decreases concentration of cyclic nucleotides inside the cell
  4. other proteins like ion channels, receptors, and enzymes
  5. can make many cyclic nucleotides available, amplifying the signal
35
Q

Neuronal Computation

  1. All signals received by a neuron are what?
  2. Different signals can have different effects: how?
  3. If the summed signal produces sufficient depolarization, what happens?
  4. Most sensitive part of axon to depolarizaiton?
A
  1. summed up
  2. signals received at cell body are MORE effective usually than those received at dendrites; some dendrites can amplify signals (can generate an AP; have “spines” which make signals more effective)
  3. produces sufficient depolarization, an AP is started
  4. Axon Hillock. Decision to start an AP
36
Q

Illustration of Computation

  1. Synaptic potentials last how long? Travel how?
  2. EPSPs?
A
  1. Finite time; Travel by passive current spread
  2. arrive from multiple inputs closely in time then they have additive effects.
    * Summation = Analog

AP = digital

37
Q

Spatiotemporal Summation

  1. Temporal Summation
  2. Spatial Summation
A
  1. a. multiple inputs arriving closely in time
    b. Basis of Bloch’s Law
  2. a. Multiple Inputs from different sources; Active at the same time
    b. Basis of Ricco’s Law

Neurophysiology (4 decks)

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