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
