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Neurobio > Neurobio 2.1 (test 2, lec 1) > Flashcards

Neurobio 2.1 (test 2, lec 1) Flashcards

1
Q

Factors that affect action potential

A

MED
myelination
extracellular [K+]/ other electrolytes
diameter of axon

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2
Q

Lowest threshold for AP regeneration

A

Nodes of Ranvier

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3
Q

Why aren’t squid axons myelinated?

A

large diameter

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4
Q

T/F: Electrically coupled cells show a delay between the depolarization of one cell and another

A

False - virtually w/o delay

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5
Q

Term for any cell capable of firing AP

A

excitable

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6
Q

Gap junctions are also called

A

connexons

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7
Q

A single gap junction is composed of

A

two connexons

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8
Q

Each connexon is composed of

A

six connexins

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9
Q

A single connexon is also called

A

hemichannel

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10
Q

Gap junctions can be closed or open, and are usually _______

A

constitutively open

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11
Q

Benefits of electrical synapses

A 
Sr. Dr.
Synchronous activities of many cells
Reliable
Direct transfer of key small molecules
Rapid signalling
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12
Q

Electrical synapses more prev during

A

development

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13
Q

Electrical synapses more prev in

A

vertebrates

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14
Q

Conditions under which gap junctions close

A

high intracellular [Ca2+] or [H+] (lower pH)

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15
Q

Conc. gets high within cell when cell is damaged

A

Ca2+ and H+

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16
Q

Capable of passing through gap junctions:

A

SAIGA

  1. Small, straight peptides
  2. ATP, cAMP, cGTP
  3. Ions
  4. Gluose
  5. Amino acids
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17
Q

Can calmodulin (CaM) pass through gap junctions?

A

no

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18
Q

Generally, molecules of this size or less can go through gap junctions

A

2,000 Da

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19
Q

chemical synaptic transmission involves conversion of ____ signal to _____ to _____

A

electrical, chemical, eletrical

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20
Q

Types of synaptic transmission

A

chemical and electrical

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21
Q

Synaptic plasticity is the result of _____ transmission because it has many _____

A

chemical, points for regulation

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22
Q

The double-edged sword of chemical synapses

A

complexity means many points for regulation, but also much can go wrong and a lot of neurological diseases are associated with abhorrent chem synaptic tsmission

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23
Q

neurons mainly receive synaptic input in ___

A

dendrites and cell body

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24
Q

synaptic input first generates ____ which propagates to

A

synaptic potential, passively to axon hillock

25
propagation of synaptic potential leads to
firing of action potential at axon hillock
26
axon hillock is also called
trigger zone or initial segment
27
How might propagation of synaptic potential be boosted?
many neurons have voltage-gated channels in dendrites and cell body which open in response to synaptic potential
28
myelination speeds up AP b/c why?
AP just jumps from node to node | saltatory conduction
29
Describe node of Ranvier
high density voltage-gated channels, only place current can flow across membrane of myelinated axon
30
Review: sodium flowing in is ______ current
inward
31
Diameter of squid axon
1mm
32
Diameter of mammalian axons
0.5-20 microns
33
Diameter of axon terminals?
1-2 microns (remember, they are not myelinated)
34
Increasing diameter of axon by one micron increases speed of AP firing by
about 5 meters/second
35
At body temp, in 20 micron diameter axon, AP firing can be as fast as
100 meters/s
36
multiple sclerosis results from
demyelination; you get weak and maybe cannot walk
37
Why is potassium loss more influential in muscle fatigue when you sweat?
The extracellular conc. is only 10-12 millimolar, that of sodium is higher
38
When extracellular potassium conc. goes down, RMP becomes more ____
negative
39
What happens if RMP is more negative in terms of stamina?
Depolarization is harder and you experience muscle fatigue
40
Typical distance between cells at chemical synapse
30-40nm
41
Example of electrically coupled cells
cardiac myocytes
42
Why is it advantageous for heart cells to be connected by gap junctions
Limit regulation so that there are not too many potential problems. Gap junctions are reliable and allow synchronous activity of many cells.
43
Describe topology of connexin
Four transmembrane domains, two extracellular loops, and intracellular N-terminal and C-terminal domains. So basically an "M." Hint: "M" for myocyte junctions
44
Distance mentioned between two cells connected by gap junction
3.5nm
45
Why are gap junctions friendly?
Usually constitutively open
46
Diameter of gap junctional pore
10-20 Angstroms | "Ten to twenty is more than plenty (for various molecules to fit through such as ATP and linearlized polypetides lol)
47
Compare diameter of gap junction to that of selectivity filter of potassium channel
K+ channel is 3.2-3.3 Angstroms | Gap junctional pore is 10-20 Angstroms
48
These molecules cause gap junctions to close_____. This is a good idea because ___.
Ca2+ and H+. Cause cell death.
49
How to test if many cells are electrically coupled?
ucifer yellow dye - does it pervade all the cells?
50
Electrical synapses are seen more frequently during____. A plausible explanation is that _____.
Development. Neurons looking to reach same target may as well function as an electrical and biochemical unit.
51
In vertebrates, this type of synapse is more abundant than in invertebrates
electrical
52
Mechanisms for closing of gap junctions.
Phosphorylation and calcium or proton binding sites that induce conformational changes.
53
Diameter of unmyelinated human axon
1-2 micrometers
54
Speed of AP in unmyelinated human axon
1.8-2.2 m/s
55
Relationship between diameter of myelinated axon and speed of action potential
increase in 1 micrometer yields 5 m/s increase
56
Length of Node of Ranvier
2mm
57
To increase AP firing speed about 5 meters/second, increase diamter of axon by
1 micron
58
Significance of these numbers: a) 1-2 microns b) 2m/s c) 10-20 Angstrom d) 3.5nm e) 30-40nm
a) diameter unmyelinated axon and axon terminals b) speed of AP in unmyelinated axon c) diameter gap junctional pore d) length of electrical synapse f) length of chemical synapse

Neurobio (31 decks)

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