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Psych 275 > Chapter 4: How Do Neurons Use Electrical Signals To Transmit Information > Flashcards

Chapter 4: How Do Neurons Use Electrical Signals To Transmit Information Flashcards

1
Q

Electrical potential/Electrical charge

A

-Ability to do work using stored electrical energy
-Because electrons carry a negative charge the negative pole has a higher electrical charge (more electrons) than a positive pole

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2
Q

Electricity

A

-A flow of electrons from a body that contains a higher charge
-Fewer electrons

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3
Q

Negative pole

A

-The source of electrons; higher charge

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4
Q

Positive pole

A

-Location to which electrons flow; lower charge

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5
Q

Galvani (18th century)

A

-Electrical current applied to a dissected nerve induced a twitch in the muscle connected to the nerve
-Galvani concluded that electricity flows along the nerve

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6
Q

Electrical stimulation

A

-Passing an electrical current from the top of an electrode through brain tissue
-Results in changes in electrical activity of the tissue

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7
Q

Fritsch and Hitzig (19th century)

A

-Electrical stimulation of the neocortex causes movement in arms and legs

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8
Q

Bartholow (1874)

A

-First report of human brain stimulation
-passed insulated needle into the left posterior lobe so that the non-insulated portion rested entirely in the substance of the brain
-When circuit closed muscular contraction in the upper right and lower extremities ensued

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9
Q

Caton (early 19th century)

A

-First attempt to measure electrical currents of the brain using a voltmeter and electrodes on the skull

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10
Q

-Electroencephalogram

A

-Graph that records electrical activity through the skull or from the brain and represents graded potentials of many neurons
-Less invasive
-Measures electrical potential on scalps
-Not entirely accurate due to other noise in brain

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11
Q

Von Helmholtz (19th century)

A

-Flow of information in the nervous system is too slow to be a flow of electricity
-Nerve conduction: 30-40 meters/s
-Electricity: 3x108 meters/s

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12
Q

Bernstein (1886)

A

-It is not the ions themselves that travel along the axon but rather a wave of charge
-One node to another–saltatory conduction

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13
Q

Electrical potential

A

-An electrical charge measured in volts; the ability to do work through the use of stored electrical energy

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14
Q

Volt

A

-A measure of a difference in electrical potential
-Inside of axon vs outside of axon

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15
Q

Voltmeter

A

-A device that measures the difference in electrical potential between two bodies

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16
Q

Microelectrodes

A

-Set of electrodes small enough to place on or in an axon
-used to measure a neurons electrical actvity and deliver an electrical current to a single neuron (stimulation)

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17
Q

Oscilloscope

A

-A device that serves as a sensitive voltmeter
-Used to record voltage changes on an axon

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18
Q

Cations Vs Anions

A

-Cations = positively charged ions (Na+, K+)
-Anions = (Cl-, protein, A-)

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19
Q

Diffusion

A

-Movement of ions from an area of high concentration to an area of low concentration through random motion

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20
Q

Concentration gradient

A

-Differences in concentration of a substance among regions of a container allow the substance to diffuse from an area of higher concentration to an area of lower concentration

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21
Q

Voltage gradient

A

-Difference in charge between 2 regions that allows a flow of current if the two regions are connected
-Opposite charges attract
-Similar charges repel
-Ions will move down a voltage gradient from an area of higher concentration to an area of lower charge

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22
Q

Equilibrium

A

-Efflux of cl- ions down the cl- concentration gradient is counteracted by the influx (forward flow) of cl- ions down the cl- voltage gradient
-Occurs when the concentration gradient of cl on the right side of the beaker is balanced by the voltage gradient of the cl ions on the left
-Concentration gradient is equal to voltage gradient

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23
Q

Resting potential

A

-Electrical charge across the cell membrane in the absence of stimulation
-Store of negative energy on the intracellular side relative to the extracellular side
-The inside of the membrane at rest is -70 millivolts relative to the extracellular side

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24
Q

Four charged particles

A

-Four charged particles take place in producing the resting potential
-Sodium and chloride = higher concentration outside cell
-Potassium and large proteins = higher concentration inside cell

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25
Maintaining resting potential
-Ungated potassium and chloride channels allow potassium and chloride ions to pass freely, but gates on sodium channels keep out positively charged sodium ions -Na and K pumps extrude Na 3 from the intracellular fluid and inject 2 K
26
Inside the cell
-Large proteins -Negative charge alone is sufficient to produce transmembrane voltage/resting potential -Cells accumulate positively charged potassium ions to the extent about 20 times as many potassium ions cluster inside the cell as outside -Because concentration of potassium is much higher than outside the cell, potassium ions are drawn out the cell by concentration gradient
27
Outside the cell
-Sodium ions are kept out to the extent that about 10 times as many sodium ions reside outside the axon membrane as inside it -Difference in concentration of sodium also contributes to resting potential -Gates on sodium channels in the cell membrane are ordinarily closed blocking entry of most sodium ions
28
Graded potentials
-If concentration of ions across unstimulated cell changes the membrane voltage changes -Graded potentials are small voltage fluctuations across the cell membrane
29
Hyperpolarizarion
-Increase in electrical charge across a membrane (more negative) -Usually due to the inward flow of chloride ions or outward flow of potassium ions
30
Depolarization
-Decrease in electrical change across a membrane (more positive) -Usually due to the inward flow of sodium
31
Action potential
-Large, brief reversal in polarity of an axon -Lasts approx. 1 MS
32
Threshold potential
-Voltage on a neural membrane at which an action potential triggered -opening of Na+ and K+ voltage activated channels -Approx. -50 mV relative to extracellular surround
33
Voltage-activated ion channels
-Gated protein channels that open or close only at specific membrane voltages -Sodium (Na+) and potassium (K+) -Closed at membrane's resting potential -Na+ channels are more sensitive than K+ channels and therefore, open sooner.
34
Voltage Activated Ion Channels
-Occurs when a large concentration of first Na+ ions, then K+ ions crosses the membrane rapidly -Depolarization due to Na+ influx -Hyperpolarization due to K+ efflux (TEA)
35
Blocking an action potential
-An action potential is produced by changes in voltage-activated Na+ and K+ channels which can be blocked by TTX and TEA -
36
Role of Voltage activated channels
-Both voltage activated channels are attuned to threshold of -50mV. If cell membrane reaches this, both channels open and allow ion flow across membrane -Sodium channels react quicker so voltage change occurs quicker with Na influx before k+ efflux can occur
37
+30mV
-Sodium channels have two gates, once membrane depolarizes to +30mV one of the gates closes. Thus Na+ influx begins quickly and ends quickly
38
Which channel opens slower?
-The K+ channels open slower than Na+ channels and they remain open longer -Efflux of K+ reverses the depolarization produced by Na+ influx and hyperpolarizes the membrane
39
Absolute refractory period
-State of an axon in repolarizing period, during which a new action potential cannot (usually) be elicited because gate 2 of sodium channels (not voltage activated) closes
40
Relative refractory period
-State of an axon in the later phase of an action potential, during which stronger electrical current is required to produce another action potential -K+ channels are still open
41
Nerve impulse
-Propagation of an action potential on the membrane of an axon -Refractory periods produce a single discrete impulse that travels along the axon in one direction only -Size and shape of action potential remain constant along the axon
42
Refractory period
-Although action potential can travel in either direction of an axon, refractory periods prevent it from reversing directions -They produce a single discrete impulse that travels away from the point of initial stimulation
43
Myelin
-Produced by oligodendroglia in the CNS and schwaan cells in the PNS -Speeds up neural impulse
44
Node of ranvier
-Part of an axon that is not covered by myelin -Tiny gaps of myelin sheath -Enables saltatory conduction
45
Damaged myelin
-Neuron may be unable to send any messages over to its axons -Multiple sclerosis (MS) the myelin formed by oligodendroglia is damaged, which disrupts the functioning of neurons whose axons it encases
46
How do neurons integrate information
-Through dendritic spines, neuron can establish more than 50 000 connections to other neurons -Nerve impulses traveling from other neurons bombard the receiving neuron with all manner of inputs excitatory and inhibitory -Cell body, (between dendritic tree and axon) can receive inputs from many other neurons
47
EPSP
-Excitatory post synaptic potential -Brief depolarization of a neuron membrane in response to stimulation -Depolarized neuron is more likely to produce an action potential -opening of sodium channels: influx of Na+
48
IPSP
-Inhibitory postsynaptic potential -Brief hyperpolarization of a neuron membrane in response to stimulation -Hyperpolarized neuron is less likely to produce an action potential -Opening of K+ (efflux) or Cl- channels(Influx)
49
Temporal summation VS spatial summation
-Temporal: Pulses that occur at approximately the same time on are summed -Spatial: Pulses that occur at approximately the same place on a membrane are summed
50
Summation of Inputs
-A neuron sums all inputs that are close in time and space -Provides an indication of the summed influences of multiple inputs -If summed ionic inputs exceed threshold (-50mV) at the axon hillock an action potential will be initiated
51
Ions and Summation
-Influx of Na+ accompanying one EPSP is added to the influx of sodium ions accompanying a second EPSP if the two occur close together in time and space -If the two are remote in time or space no summation is possible -Same regarding K+ effluxes
52
Axon Hillock
-Junction of cell body and axon -rich in voltage-activated channels -Where EPSPs and IPSPs are integrated -where action potentials are initiated
53
Cell body membranes
-Do not contain voltage-activated channels -Typical neuron does not initiate action potentials on its dendrites -In some neurons however voltage activated channels on dendrites do enable action potentials
54
Back propagation
-Reverse movement of an action potential from the axon hillock into the dendritic field -Signals the dendritic field that the neuron is sending an action potential over its axon and may play a role in plastic changes in the neurons that underlie learning
55
Nonmammalian species
-Neurons of some nonmammalian species have no dendritic branches
56
Optogenetics
-Some ion channels, rather than responding to voltage, respond to light by opening and allowing ions to pass
57
Differences among neurons
-The many differences among neurons suggest that the nervous system capitalizes on structural and functional modifications to produce adaptive behavior in each species
58
How we receive stimuli
-Bodily sensations (touch and balance) -Auditory sensations (hearing) -Visual sensations (Sight) Chemical sensations (taste and olfaction) -neurons related to these diverse receptors all have ion channels on their cell membranes --produce nerve impulses
59
Touch producing action potentials
-Each hair on body allows detection of slightest displacement -Dendrite of a touch neuron wrapped around the base of each hair -Hair displacement opens stretch-activated channels in the dendrites membrane -When channels open they allow influx on Na+ sufficient to depolarize the dendrite to threshold
60
How do nerve impulses produce movement
-Spinal motor neurons send nerve impulses to synapses on muscle cells -Axons of each motor neuron makes one or more synapses with target muscle
61
End plate
Part of the muscle membrane that is contacted by the axon terminal
62
Acetylcholine: How nerve impulses produce movement
-Chemical transmitter that the axon terminal releases at the muscle and end plate -attaches to transmitter-activated channels -Channels open allowing Na+ and K+ ions across the muscle membrane to depolarize muscle -Muscle then generate action potentials to contract
63
Muscle contractions
A: when a motor neurons and collaterals contact a muscle fiber end plate B: Acetylcholine attaches to receptor sites on the end plates transmitter-activated channels opening them -These large membrane channels allow influx and efflux of Na+ and K+ generating a current sufficient to activate threshold

Psych 275 (8 decks)

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