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Flashcards in Neuronal Signaling Deck (79)
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1

An increase in axon diameter results in what?

Decrease in resistance within the axon membrane - ions more more rapidly
Increases conduction velocity

2

Absolute Refractory period

NO action potentials can be generated
K channels open - hyperpolarization
Na channels inactive
Directly behind propagating action potential

3

Voltage gated channels

Responds to changes in voltage

4

Propagation of an action potential from the soma to the axon terminal is unidirectional because...

of the inactivation of the Na channels

5

[Ca] mM

ECM 2.5
ICM .0001

6

Schwann Cells

Make myelin in PNS

7

Voltage

Electrical potential difference between two regions of charge

8

A change in membrane potential from -40 mV to -70 mV...

would occu in response to opening K channels

9

Membrane potential

Ionic concentration difference between ECT and Intracellular fluid across membrane results in electrical potential/voltage

10

Neurons differ in size - they can range from ____ to _____

um to meters

11

Name the 4 glial cells

Astrocytes
Oligodendrocytes
Schwann Cells
Microglia

12

Microglia

Macrophage-like - activated by injury
Phagocytize and digest waste products

13

unipolar neuron

one process

14

Tetrodotoxin

Toxin isolated from Japanese Puffer fish
Blocks Na channels/nerve conduction

15

Guillain-Barre Disease

Autoimmune disorder that attacks myelin in the PNS
Acute - days to weeks

16

Na voltage gated channels

High number in axon for depolarization
Closed at resting potential
Opens in response to nerve pulse = Na enters cell
Inactivated for a period after activation - refractory period - will not respond to a new signal

17

Pseudounipolar neurons

One process fromsoma splitting to form 2 axons

18

Relative Refractory period

Action potentials can be generated but at a higher threshold
Na channels closed
K channels open - hyperpolarization
Behind absolute refractory period

19

What kind of proteins are in the neuronal membrane?

Ion pumps
Ion channels
Receptors for neurotransmitters

20

Which glial cell is most common?

astrocytes

21

[K] mM

ECM 4
ICM 130

22

Equilibrium potential/voltage

balance between chemical force (concentration gradient) and electrical force (charge gradient)

23

Ca voltage gated channels

high number in axon terminal for the release of neurotransmitters and docking of vesicles

24

Ion channel

Ions move through pores via diffusion via chemical gradients

25

Etiology of multiple sclerosis

Viral infection triggers

26

A change in a cell membrane potential that makes it more negative...

hyperpolarization

27

What two factors affect the conduction velocity in axons?

Axon diameter
Myelination

28

State dependent blockade

More effecting at blocking channels/nerve conduction during the open or inactivated state

29

Symptoms of multiple sclerosis

Loss of sensation/motor function in multiple sites

30

tx of guillain barre disease

Immunoglobulins and plasmapheresis (remove plasma, which may be source of immune factors)

31

A change in a cell membrane potential that makes it more positive is....

depolarization

32

Neurons are cells with...

polarity that signals using electrical and chemical activity

33

Which two glial cells have the same function but inn different parts of the nervous system?

Oligodendrocytes
Schwann Cells

34

An increase in myelination of an axon results in what?

Increase in the axon membrane resistance, decreasing the leakage of Na
Increases conduction velocity

35

Frequence of guillain barre disease

1 in 100,000

36

How to axon hillocks accomodate the integration of local potentials?

Lots of Na channels

37

What is the reason for hyperpolarization during an action potential?

prevents reverse action potential
Limits action potential firing

38

Which ions are ion channels slective for?

Na
K
Cl
Ca

39

Threshold potential

If the integrated local potential is depolarized enough to open enough Na channels to reach the threshold potential, an action potential is initiated

40

Action potential

Brief, transient change in membrane potential (1 ms)
Polarity of membrane reverses from -60 mV to +40 mV
Results from time dependent, voltage sensitive channels
Propagates from soma to axon terminal in all or none fashion

41

What are 3 things of note when calculating the equilibrium potential?

1. Very few ions actually move
2. Potential difference occurs near membrane
3. At equilibirum, no net movement of K+ ions

42

Oligodendrocytes

Make myelin in CNS

43

The Na/K pump is ELECTROGENIC - what does this mean?

It generates a voltage
-2 mV

44

How does ion gating differ between Na and K?

Na - open - inactive - closed
K - no inactivation

45

Multiple sclerosis

Autoimmune disorder which attacks myelin in the CNS
Chronic - months to years - relapsing/progressively worse

46

Saltatory propagation

Action potential jumps from one Node of Ranvier to the next
= increase in conduction velocity

47

What is the structure of the neuronal membrane?

Lipid bilayer

48

Equilibirum potential

membrane potential at which the electrical gradient and chemical (concentration) gradient become = in magnitude but in opposite direction

aka the electrical potential required to offset the chemical gradient

49

K voltage gated channels

high number in axon for repolarization and hyperpolarization

50

Multipolar neuron

Most common
Multiple processes

51

Nodes of Ranvier

Gaps of axon between myelinated portions
Where Na can anter axon

52

[Cl] mM

ECM 120
ICM 5

53

Tx of multiple sclerosis

Glucocorticoids - adrenal steroids to decrease inflammation

54

What is the function of the neuronal membrane?

Barrier to ion flow
Storage for ionic charge
Support of integral membrane proteins

55

The Nernst equation calculates

Calculates the equilibrium potential of a single ion IF only 1 ion channel open at a time

56

Ion pump

Ions move through membrane AGAINST chemical gradient

57

Ligand gated channels

High number in dendrites and in cell bodies that receive synaptic input
Neurotransmitters to dendrites

58

Which cytoskeletal proteins are in axons and dendrites? What are their function?

Microtubules
Neurofilaments
Structural support

59

Dendrites receive ______ signals from axons and transmits _______ signals to cell body

chemical
Electrical

60

Local potentials generated in dendrites can cause...

1. excitatory neurotransmitters cause a depolarization
2. inhibitory neurotransmitters cause a hyperpolarization

61

Local potentials are INTEGRATED (summated) where?

At the axon hillock - first portion of axon extending from cell body

62

Bipolar neuron

two major processes

63

[Na] mM

ECM 140
ICM 15

64

Which type of neuron is most common?

multipolar

65

Internodes

Myelinated portions of axon

66

Neuronal cell bodies contain which organelles?

Nucleus
Endoplasmic reticulum/ribosomes (protein synthesis)
Golgi (protein processing and packaging)
Mitochondria
Lysosomes

67

symptoms of guillain barre disease

Loss of sensation/muscle control
Initially hands and feet then moves to torso

68

What are two properties of ion channels?

Ion gating
Ion selectivity

69

An axon is a single process extending from the cell body which transmits _______ activity to terminals that release ______

electrical (action potential)
chemical signals (neurotransmitter)

70

etiology of guillain barre disease

Infection triggers immune response

71

Na/K pump

Ion pump
Requires ATP
Electrogenic - generates voltage (-2mV)
Responsible for maintaining Na/K concentration gradient

72

Which organelles are in the axon?

cytoskeletal proteins
mitochondria
vesicles - neurotransmitter

73

Synaptic potential

difference in voltage between the outside and inside of a postsynaptic neuron

74

What is the frequency of multiple sclerosis

1 in 1,000

75

Astrocytes

"Star shaped"
Structural support
Uptake of ions - K
Fill gaps via proliferation - injury
Neurotransmitter metabolism
Blood flow

76

Local anaesthetics - lidocaine

Blocks sodium channels/nerve conduction

77

Membrane potentials with single ions are generated by the selective movement of a single ion due to _________ gradient across membrane

electrochemical

78

Which organelles are in dendrites?

endoplasmic reticulum
mitochondria
cytoskeletal proteins

79

Ligand gated ion channels are also called

ionotropic receptors