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PSYCH 255 > Chapter 4 - Neural Communication > Flashcards

Chapter 4 - Neural Communication Flashcards

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1
Q

Electricity

A

electrons flowing from negative pole to positive pole via conducting medium

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2
Q

Current

A

flow of electrons from negative to positive pole

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3
Q

Electric Potential

A

difference in charge between negative & positive pole

  • relative charge
  • volts (V)
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4
Q

Linking Electricity & Neural Activity

  • History
    • ​People (6)
A

1) Stephen Gray
2) Luigi Galvani
3) Gustv Fritsch & Eduard Hitzig
4) Bartholow
5) Wilder Penfield
6) Richard Caton

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5
Q

1) Stephen Gray

A

1731

  • found that flying boy conducts electricity
  • speculated that electricity is neural messenger
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6
Q

Findings from what suggested that neurons send electrical messages?

A

Electrical stimulation studies

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7
Q

Electrical Stimulation Studies suggesting neurons send electrical messages

2) Luigi Galvani

A

18th C

observed twitching frog legs on wire in market during lightning storm

  • suspected that electricity was activating muscles
  • confirmed speculation by stimulating nerves using electricity in lab
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8
Q

Electrical Stimulation Studies suggesting neurons send electrical messages

3) Gustav Fritsch & Eduard Hitzig

A

19th C

demonstrated that electrical stimulation of neocortex caused movement

  • identified motor cortex & mapped motor homonculus in animals
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9
Q

Electrical Stimulation Studies suggesting neurons send electrical messages

4) Bartholow

A

1874

1st to electrically stimulate human brain

  • patient with exposed parietal lobe
    • reported pain & tingling sensation
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10
Q

Electrical Stimulation Studies suggesting neurons send electrical messages

5) Wilder Penfield

A

electrically stimulated people having surgery for epilepsy

  • attempted to provoke “aura” (warning of impending seizure) that precedes seizure to find region of abnormal activity
  • also identified areas associated with language to try to avoid removing these areas
  • mapped out motor & sensory homonculus
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11
Q

Findings from Electrical _____ Studies also suggested neurons send electrical messages

6) Richard Caton

A

Electrical Recording Studies

20th C

1st to measure electrical currents of brain with voltmeter by placing electrodes on skull

→ Electroencephalogram (EEC)

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12
Q

Electroencephalogram (EEG)

A

standard tool for detecting electricaly activity in brain using electrodes attached to scalp

→ used to:

  • monitor sleep stages
  • record waking activity
  • diagnose disruptions (such as in epilepsy)
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13
Q

Hermann von Helmholtz

A

stimulated nerve leading to muscle & measured time muscle took to contract

  • 30-40 m/s
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14
Q

Microelectrodes

A

in brain to stimulate/record more precisely

  • i.e. specific region/cell
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15
Q

Ion Movement & Electrical Charge

A

chemicals in ICF & ECF differ & are kept seperate by cell membrane

  • chemicals are electrically charged (IONS)
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16
Q

Ions

A

electrically-charged chemicals

cations & anions

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17
Q

Cations

  • (2)
A

positively-charged ions

  • Sodium (Na+)
  • Potassium (K+)
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18
Q

Anions

  • (2)
A

negatively-charged ions

  • Chloride (Cl-)
  • Protein molecules (A-)
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19
Q

(3) factors influence movement of ions in/out of cell

A

1) Diffusion
2) Concentration Gradient
3) Voltage Gradient

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20
Q

Factors Influencing Ion Movement In/Out of Cell

1) Diffusion

A

movement of ions from area of [high] to area of [lower] through random motion

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21
Q

Factors Influencing Ion Movement In/Out of Cell

2) Concentration Gradient

A

differences in [substance] among regions that allow diffusion from area of [higher] to area of [lower]

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22
Q

Factors Influencing Ion Movement In/Out of Cell

3) Voltage Gradient

A

difference in charge between regions

  • allow flow of current if regions are connected
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23
Q

Resting Potential

  • definition
  • due to?
A

electrical charge across membrane at rest

  • greater negative charge on inside relative to outside
    • store of PE
  • - 70 mV

due to unequal distribution of ions inside & outside

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24
Q

Features of Cell Membrane Contributing to Resting Potential (4)

(How is the distribution of ions inside & outside of cell maintained?)

A

via channels, pumps & gates

  • proteins cannot leave cell (large & - charged)
  • channels allow K+ & Cl- to move in & out of cell more freely
  • Gated channels prevent Na+ from entering cell
  • Na/K Pumps → 3 Na+ out & 2 K+ in
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25
Q

Movement of K+ & Cl- across membrane

A

K+ → in

  • attracted by (-) charge

Cl- → out

  • stays in more (+) environment
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26
Q

Concentration of Sodium in ICF & ECF

A

[Na]out = 10x [Na]in

10x more Na+ outside than inside cell

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27
Q

Graded Potentials

A

small voltage fluctuations restricted to vicinity where ion concentrations change

  • change is proportional to stimulation
    • ​Δ[ion] → Δ membrane potential
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28
Q

(2) types of Graded Potentials

A

1) Excitatory Postsynaptic Potentials (EPSPs)
2) Inhibitory Postsynaptic Potentials (IPSPs)

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29
Q

1) Excitatory Postsynaptic Potentials (EPSPs)

  • define
  • effects (2)
  • due to?
A

GPs (brief graded depolarization) of membrane in response to stimulation

  • makes membrane potential more positive
    • ​inside more + than outside
  • ↑ increase likelihood of AP
  • due to opening of Na+ channels → Na+ enters
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30
Q

2) Inhibitory Postsynaptic Potentials (IPSPs)

  • define
  • effects? (2)
  • due to? (2)
A

GPs (brief, graded hyperpolarization) of neural membrane in response to stimulation

  • makes membrane potential more negative
    • ​inside even more (-) than outside
  • ↓ decreases likelihood of AP
  • due to: (caused by binding of NT)
    • opening of K+ channels → K+ out
    • OR opening of Cl- channels → Cl- in
31
Q

Hyperpolarization

A

small increase in charge across membrane due to

Cl- influx & K+ outflow

  • IPSPs → ↓ likelihood of firing
32
Q

Depolarization

A

small decrease in charge across cell membrane due to Na+ influx through open gated channels

  • EPSP → ↑ likelihood of firing
33
Q

GABA

A

major inhibitory NT

  • receptors have Cl- channels
    • Cl- influx

alcohol binds to GABA sites

34
Q

Glutamate

A

major excitatory NT

35
Q

Graded Potentials in:

a) Sensory Neuron
b) Interneurons & Motor Neurons

A

a) GP produced by external stimuli → only EPSPs
b) GP produced by other neurons
* EPSPs & IPSPs

36
Q

Action Potential

A

large, brief reversal in polarity of membrane

  • neuron that is stimulated to point of transmitting a signal is in action
  • 200 /s
37
Q

Threshold Potential

A

voltage on neural membrane at which an AP is triggered by opening of Na & K vs-channels

~ -50mV

38
Q

Phases of an AP (5)

A

1) Resting
2) Depolarization
3) Repolarization
4) Hyperpolarization
5) Resting

39
Q

Phases of AP

1) Resting

A

vs-Na channels & vs-K channels are closed

40
Q

Phases of AP

2) Depolarization

A

enough EPSPs & Na+ inflow

membrane potential reaches threshold

  • inside charge = ~-50 mV relative to outside

→ AP triggered

  • vs-Na & K channels open
    • vs-Na channels open faster → Na+ influx
      • ​​+30 mV
41
Q

Phases of AP

3) Repolarization

A
  • membrane potential of 30 mV triggers closing of non-vs Na channel
  • vs-K+ channels slower to open but remain open longer ​
    • K+ outflow reverses depolarization
    • - 70 mV
42
Q

Phases of AP

4) Hyperpolarization

A

vs-Na channels closed (non-vs Na channels reopened)

Since vs-K channels close slower than Na channels, too much K+ leaves, causing hyperpolarization

→ -73 mV

43
Q

Phases of AP

5) Resting

A

Resting potential restored by Na/K pump

  • active transport of 3Na+ out & 2K+ in
44
Q

Refractory Periods (2)

A
  1. Absolute RF
  2. Relative RF
45
Q

Absolute Refractory Period

A

period during repolarization phase in which another AP cannot be triggered

  • since Gate 2 of Na+ channel (non-vs) is closed
46
Q

Relative Refractory Period

A

period during hyperpolarization in which more stimulation is needed to trigger another AP

  • since membrane potential is further from threshold
    • ~ -73 mV
  • non-vs Na+ channel (gate 2) is open
47
Q

Nerve Impulse

A

propogation of AP along axon membrane

→ each AP causes adjacent point on membrane to reach threshold potential

  • APs are of a constant size
48
Q

(2) Practical Uses of Refractory Periods

A

1) limits maximum rate of AP to ~ 200 per second
2) prevent AP from reversing direction & returning to origin
* creates single, discrete impulses traveling away from point of initial stimulation

49
Q

Backpropagation

  • role in?
A

phenomenon in which AP of neuron creates voltage spike at end of axon & back through dendrites (from which original input current originated)

  • may play role in plastic changes that underlie learning
50
Q

Rate of Nerve Impulses

  • affected by? (2)
A

1) Width of axon
2) Amount of myelin

51
Q

Rate of Nerve Impulse →

1) Width of axon

A

↑ diameter → ↑ total volume for charges to flow through & ↓ resistance

52
Q

Rate of Nerve Impulse

2) Amount of Myelin

A

Myelin creates insulating barrier to flow of ionic current

Nodes of Ranvier are close enough that AP at one node can trigger opening of vs-gates at adjacent node, allowing AP to “jump” from node to node (saltatory conduction)

53
Q

Saltatory Conduction

A

propagation of AP at successive nodes of Ranvier

54
Q

Why are APs not produced on motor neuron’s cell body?

A

cell body membrane of most neurons does NOT contain vs-channels

  • stimulation must reach axon hillock, which is rich in vs-channels
55
Q

Whether or not threshold is reached & AP is generated depends upon? (2)

A

Temporal Summation

Spatial Summation

56
Q

For summation of inputs to occur….

A

Both Temporal & Spatial Summation must occur

57
Q

Temporal Summation

A

GPs that occur at approximately the same time on membrane are summated

58
Q

Spatial Summation

A

GPs that occur at approximately the same location on membrane are summated

59
Q

Role of IONS in Summation

A

EPSP → Na+ influx

added to

IPSP → K+ outflow

if spatially & temporally close together

  • If summed EPSPs & IPSPs charge membrane to threshold level at axon hillock, AP travels down axon membrane
60
Q

Temporal & Spatial Summation are how neurons…

A

integrate info recieved from other neurons

61
Q

Where does summation occur?

A

Soma & Dendrites recieve EPSPs & IPSPs

  • inputs are summated here
62
Q

Where is AP initiated?

A

Axon Hillock is rich in vs-gated channels

→ AP is initiated here

63
Q

How does sensory stimuli produce APs?

A

Sense receptors detect physical energy (chemical & mechanical stimuli) & convert E into APs

  • ion channels chemically/mechanically opened, which activate vs-gated ion channels to produce APs
64
Q

Sense Receptors

A

sensory nerve endings that responds to stimuli by converting its energy into an AP (sensory transduction)

65
Q

What type of senses are:

a) olfaction (smell)
b) gustation (taste)
c) vision
d) somatosensation
e) audition

A

olfactory, gustation & vision → chemical senses

somatosensation & audition → mechanical senses (produced by physical movement)

66
Q

Process of Touch Receptors

A

mechanical displacement of hair causes dendrite of touch neuron encircling base of hair to stretch

  • opens stretch-sensitive channels in dendrite membrane
  • Na+ influx depolarizes dendrite to threshold
  • vs-channels (Na & K) activated
    • open & initiate nerve impulse
      • conveys touch info to brain
67
Q

Process of Receptors in Eye

A

light particles strike chemicals in receptors

cause chemical change → activates ion channels in relay neurons’ membrane

68
Q

Stretch-Sensitive Channel

A

ion channel on tactile sensory neuron that activates in response to stretching of membrane & initaties nerve impulse

69
Q

Why are Somatosensory Neurons special?

A

Unipolar → 1 pole off of cell body

dendrites are myelinated & propogate APs

70
Q

How do Motor Neurons facilitate muscle movement?

A

axon of motor neurons synapses with target muscle

axon terminal releases ACh onto end plate of muscle membrane

  • opens transmitter-sensitive channels
  • Na+ in, K+ out → depolarizes muscle to threshold
  • adjacent vs-channels open → produce AP
  • muscle contracts
71
Q

End Plate

A

Receptor-Ion complex on muscle that is activated by release of ACh from terminal of motor neuron

72
Q

Transmitter-sensitive channel

A

Receptor complex with both a receptor site & pore through which ions can flow

73
Q

Neurons communicate using?

A

Electrochemical messages

  • ‘Electric’ aspect caused by change in [C] of ions found inside & outside cell

PSYCH 255 (7 decks)

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