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Flashcards in Chapter 4 Deck (66):
1

Symptoms of Epilepsy

Aura: a "feeling" or sensation
Abnormal movements
loss of consciousness

2

Electrical Stimulation

passing an electrical current from the uninsulated tip of an electrode onto a nerve produces behavior--> muscle contractoin

3

Voltmeter

device that measures the flow and the strength of electrical voltage by recording the difference in electrical potential between two bodies

4

Electroencephalogram (EEG)

can detect fluctuations in voltmeter recordings by placing electrodes on the skull

5

North Atlantic Squid

has "giant" axons--millimeter in diameter

6

Oscilloscope

device that serves as a sensitive voltmeter by registering the flow of electrons to measure voltage

7

Microelectrode

microscopic insulated wire or a salt-water filled glass tube of which the uninsulated tip is used to stimulate or record from neurons

8

Na

Sodium; positively charged

9

K

potassium; positively charged

10

Cl

chloride; negatively charged

11

A

protein molecules; negatively charged

12

Cations

positively charged ions

13

anions

negatively charged ions

14

Diffusion

movement of ions from an area of higher concentration to an area of lower concentration through random motion

15

Concentration Gradient

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

16

Voltage Gradient

difference in charge between two regions that allows a flow of current if the two regions are connected

17

Efflux

outward flow

18

influx

inward flow

19

Resting potential

store of potential energy in a membrane; -70mV

20

Ions in intracellular fluid

K+ and A-

21

Ions in the extracellular fluid

Na+ and Cl-

22

Maintaining Resting Potential

1. membrane is mostly impermeable, leaving A- inside
2. Ungated K+ and Cl- channels allow ions to pass freely, but gates keep Na+ out
3. Na+ -K+ pump extrude Na+ from inside and inject K+

23

A-

large protein anions; manufactured inside cells; too large to leave; alone sufficient to produce a transmembrane voltage or resting potential

24

How do cells balance A-?

K+ cross through channels; 20:1 inside to outside to balance the A- charge; K+ gets drawn out because of the concentration gradient; not enough K+ can enter to balance it

25

Outside the cell

Na+ is gated outside

26

Sodium-Potassium Pump

protein molecule embedded in the cell membrane that escorts out Na+ ions that leak into the cell; exchange three intercellular Na+ for two K+ ions

27

Cl-

move in an out of the cell freely; contribute little to resting potential;

28

Graded Potentials

small voltage fluctuations that are restricted to the vicinity on the axon where ion concentration change

29

Hyperpolarization

increases in electrical charge across a membrane, usually due to the inward flow of Cl- or Na+ or the outward flow of K+ ions; ex. -73 mV

30

Depolarization

decrease in electrical charge across a membrane, usually due to the inward flow of sodium ions; ex. -65 mV

31

Where does hyperpolarization/depolarization take place?

soma (cell-body) and dendrites; these areas contain channels that can open and close

32

Potassium Channels

for a membrane to become hyperpolarized, outside must become more positive--> efflux of K+. there is resistance to outward flow of K+--> reduce resistance for hyperpolarization

33

Chloride Channels

hyperpolarization--> influx of Cl-. Can pass through, but more remain outside. Thus, decreased resistance to Cl- can result in brief increases of Cl- inside

34

Sodium Channels

depolarization--> influx of Na+ by opening of normally gated Na+ channels

35

Action Potential

large, brief reversal in the polarity of an axon; summed current changes of inflow of Na+ and outflow of K+

36

Threshold Potential

voltage on a neural membrane at which an action potential is triggered by the opening of Na+ and K+ voltage-sensitive channels; about -50 mV relative to extracellular surroundings

37

Voltage Sensitive Channels

closed during resting potential; open briefly when the threshold voltage is met

38

How voltage sensitive channels work

1. Na+ and K+ have a threshold voltage of -50 mV--> channels open if this is met
2. Na+ open first because they are more sensitive
3. Na+ have two gates: once membrane depolarizes to +30 one gate closes
4. K+ open more slowly but stay open longer--> efflux reverses depolarization caused by Na+ influx

39

Absolutely Refractory

State of an axon in the repolarizing period during which a new action potential cannot be excited because gate 2 of Na, which is not voltage sensitive, is closed

40

Relatively Refractory

state of an axon in the later phase of an action potential during which increased electrical current is required to produce another action potential; K+ channels are still open

41

# of Na+ gates

2

42

# of K+ gates

1

43

During resting potential

gate 1 of Na+ is closed with gate 2 open-->threshold-->gate 1 opens and gate 2 quickly closes. When BOTH are open and when 2 is closed--> absolutely refractory

44

When a membrane is hyperpolarizing it is....

relatively refractory

45

Nerve Impulse

propagation of an action potential on the membrane of an axon

46

Refectory periods prevent...

action potentials from reversing direction on an axon

47

Largest human axons

30 micrometers wide and thus are not quick to transmit information

48

Glial Cells

speed up nerve impulses by forming meyling

49

Schwann Cells

Glial cells in the PNS; form meylin

50

Oligodendroglia

Glial cells in CNS; form meyling

51

Node of Ranvier

part of axon not covered by meylin; action potential occurring at one node can trigger the opening of voltage-sensitive gates at an adjacent node

52

Saltatory Conduction

propagation of an action potential at successive nodes of ranvier

53

Excitatory Postsynaptic Potentials (EPSPs)

reduce the charge of the membrane toward the threshold level and increase the probability that an action potential will result

54

Inhibitory Postsynaptic Potentials (IPSPs)

increase the charge of the membrane away from the threshold level and decrease the probability that an action potential will result

55

EPSPs

open Na+ channels and allow an influx of Na+ ions

56

IPSPs

open K+ channels, allow for an efflux of K+ ions OR the opening of Cl- channels and the influx of Cl-

57

Temporal Summation

graded potentials that occur at approximately the same time on a membrane are summed

58

Spatial Summation

graded potentials that occur at approximately the same location and time on a membrane are summed

59

Will a cell fire?

membrane indicates the summed influences of multiple inputs (temporal and spatial summation). Neuron analyzes inputs before determining what to do--> decision made at the axon hillock

60

Axon Hillock

region that initiates the action potential; inputs close are more influential than those further away

61

To produce an action potential

summed graded potentials must depolarize the membrane at the axon hillock to -50 mV

62

Hippocampus

can produce additional action potentials (depolarizing potentials) when the cell would typically be refractory

63

Back Propagation

movement of an action potential from the axon hillock into the dendritic field; signals that the neuron is sending an action potential over the axon and may influence learning

64

Stretch Sensitive Channel

Ion channel on a tactile sensory neuron that activates in response to stretching of the membrane, initiating a nerve impulse

65

End Plate

on a muscle, the receptor-ion complex that is activated by the release of the neurotransmitter acetylcholine from the terminal of a motor neuron

66

Transmitter-sensitive Channels

receptor complex that has both a receptor site for a chemical and a pore through which ions can flow