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PSYCH 255 > Chapter 4 - Neural Communication > Flashcards

Chapter 4 - Neural Communication Flashcards

(73 cards)

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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
Movement of K+ & Cl- across membrane
**K+ → in** * attracted by **(-)** charge **Cl- → out** * stays in more **(+)** environment
26
Concentration of Sodium in ICF & ECF
[Na]out = 10x [Na]in 10x more Na+ **outside** than inside cell
27
Graded Potentials
**small voltage** **fluctuations** **restricted to vicinity** where **ion concentrations** **change** * **change** is **proportional** to **stimulation** * **​**Δ[ion] → Δ membrane potential
28
**(2)** types of Graded Potentials
1) **Excitatory** Postsynaptic Potentials (EPSPs) 2) **Inhibitory** Postsynaptic Potentials (IPSPs)
29
1) **Excitatory** Postsynaptic Potentials (EPSPs) * define * effects (2) * due to?
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**
30
2) **Inhibitory** Postsynaptic Potentials (IPSPs) * define * effects? (2) * due to? (2)
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
Hyperpolarization
small **increase** in charge across membrane due to **Cl- influx** & **K+ outflow** * **IPSPs →** ↓ likelihood of firing
32
Depolarization
small **decrease** in charge across cell membrane due to **Na+ influx** through open gated channels * EPSP → ↑ likelihood of firing
33
GABA
major **inhibitory** NT * receptors have **Cl- channels** * Cl- **influx** *alcohol binds to GABA sites*
34
Glutamate
major **excitatory NT**
35
Graded Potentials in: a) **Sensory** Neuron b) **Interneurons & Motor** Neurons
a) GP produced by **external stimuli →** only EPSPs b) GP produced by **other neurons** * EPSPs & IPSPs
36
Action Potential
large, brief **reversal** in **polarity** of membrane * neuron that is stimulated to point of transmitting a signal is **in action** * ***200 /s***
37
Threshold Potential
**voltage** on neural membrane at which an **AP** is **triggered** by **opening** of **Na & K vs-channels** ## Footnote **~ -50mV**
38
**Phases** of an AP (5)
1) Resting 2) Depolarization 3) Repolarization 4) Hyperpolarization 5) Resting
39
Phases of AP ## Footnote **1) Resting**
vs-Na channels & vs-K channels are **closed**
40
Phases of AP ## Footnote **2) Depolarization**
*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
Phases of AP ## Footnote **3) Repolarization**
* 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
Phases of AP **4) Hyperpolarization**
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
Phases of AP ## Footnote **5) Resting**
Resting potential **restored** by **Na/K pump** * active transport of **3Na+ out** & **2K+ in**
44
Refractory Periods (2)
1. **Absolute** RF 2. **Relative** RF
45
**Absolute** Refractory Period
period during **repolarization** phase in which another AP **cannot** be triggered * since Gate 2 of Na+ channel (non-vs) is **closed**
46
**Relative** Refractory Period
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
**Nerve Impulse**
**propogation** of **AP** along **axon membrane** → each AP causes **adjacent** point on membrane to reach **threshold potential** * APs are of a **constant size**
48
(2) Practical Uses of **Refractory Periods**
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
**Backpropagation** * role in?
**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
**Rate** of Nerve Impulses * affected by? **(2)**
1) **Width** of axon 2) **Amount** of **myelin**
51
Rate of Nerve Impulse → **1) Width of axon**
↑ diameter → **↑ total volume** for charges to flow through & **↓ resistance**
52
Rate of Nerve Impulse 2) **Amount** of **Myelin**
**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
Saltatory Conduction
**propagation** of AP at **successive nodes of Ranvier**
54
Why are APs **not produced** on motor neuron's cell body?
**cell body membrane** of most neurons does NOT contain vs-channels * stimulation must reach **axon hillock,** which is rich in vs-channels
55
Whether or not threshold is reached & AP is generated depends upon? (2)
**Temporal** Summation **Spatial** Summation
56
For summation of inputs to occur....
Both **Temporal & Spatial** Summation must occur
57
**Temporal** Summation
GPs that occur at **approximately** the **same time** on membrane are summated
58
**Spatial** Summation
GPs that occur at approximately the **same location** on membrane are summated
59
Role of **IONS** in Summation
**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
Temporal & Spatial Summation are how neurons...
**integrate** info recieved from other neurons
61
Where does summation occur?
**Soma** & **Dendrites** recieve **EPSPs** & **IPSPs** - **inputs** are **summated** here
62
Where is AP initiated?
**Axon Hillock** is rich in **vs-gated channels** → **AP** is **initiated** here
63
How does **sensory stimuli** produce **APs**?
_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
**Sense Receptors**
**sensory nerve endings** that responds to **stimuli** by converting its energy into an AP (**sensory transduction**)
65
What type of senses are: a) olfaction (smell) b) gustation (taste) c) vision d) somatosensation e) audition
olfactory, gustation & vision → **chemical** senses somatosensation & audition → **mechanical** senses (produced by physical movement)
66
Process of **Touch** Receptors
**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
Process of **Receptors in Eye**
light particles strike chemicals in receptors cause **chemical** **change** → activates **ion channels** in **relay neurons' membrane**
68
Stretch-Sensitive Channel
**ion channel** on **tactile sensory** neuron that **activates** in **response** to **stretching** of membrane & **initaties nerve impulse**
69
Why are **Somatosensory Neurons** special?
**Unipolar →** 1 pole off of cell body **dendrites** are **myelinated** & **propogate** APs
70
How do **Motor Neurons** facilitate **muscle movement?**
**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
End Plate
**Receptor-Ion complex** on muscle that is **activated** by release of **ACh** from **terminal** of **motor** neuron
72
Transmitter-sensitive channel
**Receptor complex** with both a **receptor** **site** & **pore** through which ions can flow
73
Neurons communicate using?
**Electrochemical** messages * **'Electric'** aspect caused by **change in [C] of ions** found **inside** & **outside** cell

PSYCH 255 (7 decks)

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