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psy290: neuroscience > week 5 > Flashcards

week 5 Flashcards

1
Q

draw what an AP looks like

A

[see sticky note]

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2
Q

summarize the AP process (6)

A
  1. membrane depolarizes past threshold by receptor/synaptic (graded) potential.
  2. voltage-gated Na+ channels open in positive feedback loop, causing rising phase.
  3. Na+ channels inactivate, initiating refractory period.
  4. voltage-gated K+ channels open, causing falling phase + undershoot.
  5. K+ channels close, end refractory period.
  6. Na+/K+ pump restores resting potential.
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3
Q

where are APs generated?

A

axon

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4
Q

gated voltage channels are ___ at rest and ___ when stimulated.

A

closed
open

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5
Q

what is the positive feedback loop?

A
  1. depolarized membrane potential,
  2. voltage-gated Na+ channels open,
  3. Na+ rushes in (depolarizes)
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6
Q

what causes the AP rising phase?

A

depolarization passing threshold, which opens voltage-gated Na+ channels, triggering other Na+ channels (domino effect).

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7
Q

what causes the rising phase to end?

A

the voltage-gated Na+ channels inactivating.

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8
Q

which voltage-gated channels operate faster: Na+ or K+?

A

Na+

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9
Q

what causes the falling phase?

A

voltage-gated K+ channels opening in response to depolarization.

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10
Q

what is the negative feedback loop?

A
  1. depolarized membrane potential,
  2. voltage-gated K+ channels open,
  3. K+ flows out (hyperpolarizes)
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11
Q

what is the all-or-none property?

A

the AP either fires at its full amplitude, or it doesn’t fire at all.

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12
Q

approx. how many APs can occur in 1 second?

A

1200

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13
Q

a) what is a refractory period?
b) what are the two refractory phases?

A

a) when beyond certain point, only first stimulus elicits AP, so axon is refractory (unresponsive) to second stimulus.

b) absolute refractory phase: brief period immediately following AP, no amount of stimulation induces another AP, because voltage-gated Na+ channels cannot respond.

relative refractory phase: strong stimulation can depolarize axon to threshold to produce another AP. K+ ions flowing out, so cell is temporarily hyperpolarized after firing AP.

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14
Q

which axons conduct faster: myelinated or unmyelinated?

A

myelinated

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15
Q

what are 3 problems with unmyelinated axons?

A
  1. leaky/low membrane resistance [rm]: ions escaping (Na+ charge exits cell, dissipating membrane polarization).
  2. sticky/high membrane capacitance [cm]: ions attracted to one another.
  3. thin/high axoplasmic resistance [ra]: little space for ions to move around.
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16
Q

a) what did invertebrates evolve?
b) what did this do?

A

a) wide axons

b) rm: not solved.
cm: slightly solved.
ra: solved – have more space to flow, therefore a bit faster.

17
Q

a) what did vertebrates evolve?
b) what did this do?

A

a) myelin

b) rm: solved – fatty barrier = +membrane resistance.
cm: solved – reduced, less attracted to each other.
ra: kinda solved?

18
Q

a) in vertebrates, do voltage-gated channels exist across the entire axon?
b) why or why not?

A

a) no

b) myelin allows ions to flow freely without risk of losing membrane polarity. therefore, no need for voltage-gated channels all down axons. instead, only at nodes of ranvier.

19
Q

what is the longest recorded span between nodes of ranvier?

A

2cm

20
Q

what is MS? (5)

A

-probably autoimmune: antibodies attack CNS myelin (oligodendrocytes).

-first symptoms (vision, tactile, balance, speech, etc) usually between 20-40 years old (progressive in nature).

-prevalence in NA: 1 in 1,000 people.
-prevalent in women 2x than men.

-genetic factors: if one identical twin has MS, 30% prob that other does vs. if one fraternal twin has MS, 4% prob that other does.

21
Q

what is a graded potential?

A

changes in membrane potential that vary in size (NOT all-or-nothing).

22
Q

diff between EPSP and IPSP?

A

EPSP: produces small local depolarization as Na+ channels open, pushing cell closer to threshold.

IPSP: produces small hyperpolarization, pushing cell further away from threshold.

23
Q

diff between spatial and temporal summation?

A

spatial summation: summing potentials that come from diff parts of cell.

temporal summation: summing potentials that arrive at integration zone at diff times (one after the other).

[see slide 24]

24
Q

what is one way we can make use of this knowledge about how neurons operate?

A

developing bionic limbs integrated to bone, nerves, and muscles so people can use their prosthetics like regular body parts.

25
Q

diff between GP and AP? (6)

A

can occur due to de- or hyperpolarization vs. only depolarization.

variable strengths [less than AP] vs. depolarization to threshold [-40mV].

generated by ligand-gated ion channels vs. voltage-gated ion channels.

short distance transmission vs. long.

may lose strength over transmission vs. do not.

can be summated vs. cannot.

psy290: neuroscience (9 decks)

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