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BMS2002 > L05 > Flashcards

L05 Flashcards

1
Q

how many connections (synapses) can a single neuron make

A

10,000

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2
Q

where are the synapses found

A

on the dendritic spines

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3
Q

what are the types of synapses

A

chemical

electrical

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4
Q

what happens in a chemical synapses

A

voltage gated calcium channels open when action potential arrives at the pre synapse

calcium influx causes creation and packaging of neurotransmitters into vesicles

neurotransmitters fuse with the pre synaptic membrane and released into the synaptic cleft

neurotransmitters bind to ion channels on the post synaptic density

ionic flux is opened generating a post synaptic potential PSP

results in intermittent transmission.

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5
Q

what happens in an electrical synapse

A

both sides of the synapse are connected thro intercellular channels (no synaptic cleft). each side has a hemi channel which come together to form a functioning intercellular channel

this allows for direct coupling of action potentials resulting in continuous transmission

transmission is rapid

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6
Q

what Cations are extracellular

A

potassium and magnesium

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7
Q

what Anions are extracellular

A

Phosphate and Some amino acids

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8
Q

what Cations are intracellular

A

Calcium and Sodium

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9
Q

what anions are intracellular

A

chloride

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10
Q

what does the resting membrane potential mean

A

voltage difference between outside and inside of the cell

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11
Q

what is the resting membrane potential for a neuron

A

-70 mV

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12
Q

how is the neuron’s RMP maintained

A

the flux of K+ ions mainly

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13
Q

how is potassium flux regulated to maintain the RMP

A

through K+ ion channels (leak)

and Na+/K+ ATPase (pump)

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14
Q

what is the action potential

A

A rapid change in the RMP (Sudden reverse of membrane polarity)

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15
Q

what is depolarization

A

Rapid change from negative MP to positive MP

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16
Q

what is repolarisation

A

Rapid return to negative MP

17
Q

why are APs important

A

they transmit of a signal

18
Q

what cells respond to APs

A

Only excitable cells

19
Q

what do APs control

A

Muscle contraction
Neurotransmitter release
Secretion

20
Q

what are the stages of an AP

A
  1. Resting phase
  2. Depolarisation
    - Slow rising phase
    - Rapid rising phase
  3. Repolarisation
  4. Hyperpolarisation (refractory)
21
Q

a stimulus has to reach a threshold before an AP is fired

A

True

22
Q

what is the AP threshold for a neuron

A

-55 mV

23
Q

what Voltage-gated channels control the AP

A

Voltage-gated sodium channel
- Opens & Na+ ions enter the cell

Voltage-gated potassium channel
- Opens & K+ ions leave the cell

24
Q

depolarization makes the outside of the cell more positive than the inside

A

False

25
Q

what causes depolarization

A

influx of Na ions through voltage gated Na channels

26
Q

what happens to Voltage gated Na+ channels during depolarization

A
  • When the membrane potential reaches about -55 mV
    (depolarisation of about 15 mV above the
    RMP of -70 mV)
    • the voltage-gated Na+ channel opens very
      rapidly
    • Na+ rushes into the cell through the
      ‘activation’ gate of the channel
27
Q

what events are associated with Voltage gated Na+ channel

A

Closed → Open
Fast, voltage gated

Open → Inactive
Fast, automatic

Inactive → Closed
Slow, automatic

28
Q

how does repolarization happen

A
  1. Following an influx of sodium,potassium channelsopen within the membrane of the axon
  2. As K+ions are more concentrated inside the neuron, opening potassium channels causes apassive efflux of potassium
  3. The efflux of potassium causes the membrane potential to return to a more negative internal differential (repolarisation)
29
Q

what happens to Voltage gated K+ channels during repolarization

A
  1. opens when the membrane is depolarised, but more slowly than the Na+ channel
  2. closes slowly in response to membrane repolarisation
30
Q

what is the refractory period (hyperpolarisation)

A

Period of time after an impulse before a cell can fire again

31
Q

what happens during hyperpolarization

A

Na+ - K+ pump opens, causing influx of K+ and eflux of Na+

32
Q

what is the absolute refractory period

A

the period between depolarization and repolarization

33
Q

what are the features of the absolute refractory period

A

Membrane cannot generate another action potential

Sodium channels are inactivated

34
Q

what are the features of the relative refractory period (hyperpolarization)

A

Membrane could generate another action potential (if given a larger than normal stimulus)

VG-Sodium channels are recovered

VG-potassium channels are still open

35
Q

where does the AP start

A

Axon initial segment (AIS)

36
Q

what prevents the AP from going backwards

A

the refractory period

37
Q

what is the mode of action of tetrodotoxin

A

depolarization

38
Q

Why would Homer experience paralysis after eating (bad) pufferfish?

A

Motor neurons stop firing, preventing communication in the brain

BMS2002 (14 decks)

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