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synaptic transmission exam 1 > Exam 1 > Flashcards

Exam 1 Flashcards

To cram for the first synaptic exam

1
Q

cation

A

+ charge

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2
Q

anion

A
  • charge
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3
Q

capacitor

A

seperator of charge

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4
Q

capacitance

A

ability to keep out charge

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5
Q

capacitance in measured in

A

farads

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6
Q

size of capicitor is proportional to

A

membrane area

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7
Q

K+ flows (—–) across the PM

A

freely

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8
Q

voltage definition

A

difference in charge btwn the anode and the cathode

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9
Q

charge of Na+ across membrabe

A

+65 mV

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10
Q

equation for voltage

A

v=ir

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11
Q

synaptic transmission

A

communication btwn cells

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12
Q

electric current in neuron controlled by…

A

moving ions across the membrane

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13
Q

current definition

A

movement of charge (indicated by positive charge movement)

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14
Q

resting membrane potential

A

very permeable to K+, (moving outside)

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15
Q

equilibrium

A

ions attempt to balance out charges to balance concentration and charge

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16
Q

Na/K pump

A

3Na ions out for every 2 K ions in, requires atp. This makes the neuron slightly more negative.

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17
Q

driving force definition

A

the push of an ion to move in or out of the cell

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18
Q

driving force equation

A

DFion= Vm (membrane potential)- Eion (equilibrium)

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19
Q

what does a positive driving force mean

A

the ion is being pushed out of the neuron

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20
Q

what does a negative driving force mean

A

the ion is being pushed into the neuron

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21
Q

voltage gated ion channels

A

change protein conformation based on potential difference across the membrane. This is dependent on the amino acid make up of each of the channels.

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22
Q

structure of a voltage gated ion channel

A

4 domains that each contain 6- alpha helical membrane spanning segments.These domains are sorted into a barrel shape. The 4th segment is a positively charged amino acid (voltage sensor). the 5th and 6th segments make a p-loop that becomes the pore of the channel.

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23
Q

how is selectivity created for an ion pore?

A

the pore narrows and also has amino acids that the ion has to interact with

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24
Q

what matters in the activation curves for Na and K?

A

The voltage and the driving force matter to determine ion movement.

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25
Q

what happens during an action potential?

A

a transient increase in the sodium permeability by activating channels

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26
Q

what depolarizes a cell?

A

any mechanism that causes an influx of positive charges into the neuron

27
Q

steps in an action potential

A

activation of Na channels -> increased Na conductance -> the cycle repeats, creating explosive depolarization -> action potential

28
Q

how are sodium ion channels inactivated?

A

ball and chain method, the closing contributes to the refractory period and the repolarization

29
Q

major mechanism of repolarizing after an action potential

A

increase in permeability to K+ (out)

30
Q

what makes a cell resistant to increased voltage?

A

small resistance (leaky), big area (charge doesnt diffuse quickly)

31
Q

how do microelectrode recording techniques work?

A

you put a sensor on the inside and outside of the cell. you can adjust the current by inserting a microelectrode.

32
Q

how does the voltage clamp work?

A

this method allows you to keep the Vm constant while being able to change the current by blocking channels or altering the ionic environment. the experimenter can keep the membrane potential at any voltage he wants (the command potential)

33
Q

Na channel inactivation

A

occurs when the ion channel closes while still in the presence of an activating stimulus. this most likely occurs with a ball and chain mechanism

34
Q

what is deactivation?

A

when the cell actually closes

35
Q

charles sherrington

A

introduced the concept of the synapse

36
Q

galvani and du bois reymond did what experiment?

A

the frog spinal cord experiment. They decided that signal went from nerve to muscle via “animal electricity”. They did the experiment by placing an iron rod to connect the spinal cord directly to the muscles.

37
Q

reticular theory

A

“web” theory. believed that neurons were connected much like capillaries connecting venules and arterioles

38
Q

ramon y cajal

A

determined that the neurons were not continuous with one another– precursor to the synapse.

39
Q

sir henry dale

A

argued that communication was chemical. ex) ACh or muscarine could mimic the vagus nerve to the heart.

40
Q

otto leowi experiment

A

used frog heart. stimulated one heart and then used the liquid from one petri dish, and put it in a dish with another heart. The uncharged liquid in the other petri dish caused the other heart to beat. This was a lucky pick for him, because achase in other animals is typically acts too quickly to be tested.

41
Q

what is another name for an electrical synapse?

A

gap junction

42
Q

in an electrical synapse the postsynaptic cell must be —— than the presynaptic cell

A

smaller

43
Q

what is some evidence for the existence of electrical synapses?

A
  1. the speed of signaling is faster than what could be acheived chemically.
  2. pre and postsynaptic activity are proportional, but not equal.
44
Q

What is the purpose of an electrical synapse?

A
  1. to very quickly send a signal

2. to link certain neuron activities (e.g. cells that fire together, wire together, stereotype behaviors like reflexes.

45
Q

what is a connexon?

A

a gap junction, which is formed by a pair of channels that span pre and post membrane. These are made of 6 subunits, and allow for chemical messaging. (each half channel is called a connexon)

46
Q

how do you regulate transmission of a gap junction?

A

by lowering the pH or by increasing intacellular calcium. Phosphorylation alters conductance. There are also different regulatory abilities based on the cytoplasmic loops.

47
Q

what is a rectifying synapse?

A

a unidirectional synapse (as seen in the crayfish).

48
Q

what are advantages of synaptic transmission?

A

plasticity, excitation and inhibition is fairly easy, you can excite a large postsynaptic cell.

49
Q

what are disadvantages of synaptic transmission?

A

slower, more energy required, less efficient, not as hard wired and can be disrupted more easily.

50
Q

fatt and katz did what?

A

measured the electrical activity in a muscle cell.

51
Q

what is synaptic delay?

A

when the AP in a presynaptic cell is 1 msec before the postsynaptic cell.

52
Q

What is the difference between an action potential and an endplate potential?

A

An action potential is maintained by voltage-gated Na and K channels in neurons and muscle cells. It can propagate along an axon or muscle cell and it is not diminished as it does so. The amplitude of the action potential may be as high as +50 mV. An end-plate potential is caused by the ligand-gated acetylcholine receptor channels found only on the postsynaptic membrane of the muscle cell. These potentials are localized, do not propagate and their maximum amplitude is 0 mV. However, when the end-plate potential reaches the threshold, an action potential will be initiated in the muscle cell.

53
Q

how to see typical muscle cell activity?

A

block sodium channels with an antagonist (such as QX314 or u-conotoxin) and this can show you background activitiy.

54
Q

what is a miniature end plate potential?

A

a small depolarization, .5-1mV in size.

55
Q

how are mEPP’s and EPP’s similar?

A

both are effected by ACh receptor blockers, AChase blockers, both are gone after the nerve is cut.

56
Q

what is an mEPP?

A

when a large dose of ACh is applied to a neuron, a small sub- AP signal is sent

57
Q

how much ACh for one mEPP?

A

~5000 molecules of ACh, and 2000 receptors are opened for each mEPP.

58
Q

as calcium outside the cell changes, how do mEPP’s and EPP’s change?

A

mEPP doesn’t change in size, but the EPP size does change (in multiples of mEPP).

59
Q

Calcium increases the likelihood that —— will be released.

A

transmitter

60
Q

What are the components of Quantal theory?

A
  1. Transmitter is only released as a fixed number of molecules (quanta)
  2. occasionally these are liberated spontaneously… mEPP
  3. Presynaptic AP increases the probability that these quanta will be released (by causing calcium to enter the nerve terminal)
61
Q

quantal content

A

mean EPP/ mean mEPP = number of quanta

62
Q

what is the equation for mean postsynaptic response?

A 
n= number of release sites
p= probability of release from each site 
q= size of quantal release

mean postsynaptic response: npq

63
Q

would you be able to do quantal analysis on a CNS synapse?

A

No, it would be too hard to isolate a cell and too difficult to tell if it measurements were free from background noise or even if the release of quanta was reliable.

synaptic transmission exam 1 (2 decks)

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