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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
Q

propagation of synaptic potential leads to

A

firing of action potential at axon hillock

26
Q

axon hillock is also called

A

trigger zone or initial segment

27
Q

How might propagation of synaptic potential be boosted?

A

many neurons have voltage-gated channels in dendrites and cell body which open in response to synaptic potential

28
Q

myelination speeds up AP b/c why?

A

AP just jumps from node to node

saltatory conduction

29
Q

Describe node of Ranvier

A

high density voltage-gated channels, only place current can flow across membrane of myelinated axon

30
Q

Review: sodium flowing in is ______ current

A

inward

31
Q

Diameter of squid axon

A

1mm

32
Q

Diameter of mammalian axons

A

0.5-20 microns

33
Q

Diameter of axon terminals?

A

1-2 microns (remember, they are not myelinated)

34
Q

Increasing diameter of axon by one micron increases speed of AP firing by

A

about 5 meters/second

35
Q

At body temp, in 20 micron diameter axon, AP firing can be as fast as

A

100 meters/s

36
Q

multiple sclerosis results from

A

demyelination; you get weak and maybe cannot walk

37
Q

Why is potassium loss more influential in muscle fatigue when you sweat?

A

The extracellular conc. is only 10-12 millimolar, that of sodium is higher

38
Q

When extracellular potassium conc. goes down, RMP becomes more ____

A

negative

39
Q

What happens if RMP is more negative in terms of stamina?

A

Depolarization is harder and you experience muscle fatigue

40
Q

Typical distance between cells at chemical synapse

A

30-40nm

41
Q

Example of electrically coupled cells

A

cardiac myocytes

42
Q

Why is it advantageous for heart cells to be connected by gap junctions

A

Limit regulation so that there are not too many potential problems. Gap junctions are reliable and allow synchronous activity of many cells.

43
Q

Describe topology of connexin

A

Four transmembrane domains, two extracellular loops, and intracellular N-terminal and C-terminal domains.
So basically an “M.”
Hint: “M” for myocyte junctions

44
Q

Distance mentioned between two cells connected by gap junction

A

3.5nm

45
Q

Why are gap junctions friendly?

A

Usually constitutively open

46
Q

Diameter of gap junctional pore

A

10-20 Angstroms

“Ten to twenty is more than plenty (for various molecules to fit through such as ATP and linearlized polypetides lol)

47
Q

Compare diameter of gap junction to that of selectivity filter of potassium channel

A

K+ channel is 3.2-3.3 Angstroms

Gap junctional pore is 10-20 Angstroms

48
Q

These molecules cause gap junctions to close_____. This is a good idea because ___.

A

Ca2+ and H+. Cause cell death.

49
Q

How to test if many cells are electrically coupled?

A

ucifer yellow dye - does it pervade all the cells?

50
Q

Electrical synapses are seen more frequently during____. A plausible explanation is that _____.

A

Development. Neurons looking to reach same target may as well function as an electrical and biochemical unit.

51
Q

In vertebrates, this type of synapse is more abundant than in invertebrates

A

electrical

52
Q

Mechanisms for closing of gap junctions.

A

Phosphorylation and calcium or proton binding sites that induce conformational changes.

53
Q

Diameter of unmyelinated human axon

A

1-2 micrometers

54
Q

Speed of AP in unmyelinated human axon

A

1.8-2.2 m/s

55
Q

Relationship between diameter of myelinated axon and speed of action potential

A

increase in 1 micrometer yields 5 m/s increase

56
Q

Length of Node of Ranvier

A

2mm

57
Q

To increase AP firing speed about 5 meters/second, increase diamter of axon by

A

1 micron

58
Q

Significance of these numbers:

a) 1-2 microns
b) 2m/s
c) 10-20 Angstrom
d) 3.5nm
e) 30-40nm

A

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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