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BIOL 1191 > Ch. 12 - Nervous Tissue II > Flashcards

Ch. 12 - Nervous Tissue II Flashcards

1
Q

What are leak channels?

A
  • randomly open/close; allow ions to move down conc gradient

- exist in dendrites, axons, cell bodies

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2
Q

What are ligand-gated channels?

A
  • require binding of specific chemical (e.g. NT, hormone) to open/close
  • exist in dendrites
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3
Q

What are mechanically gated ion channels?

A
  • open/close in response to mechanical stimuli (e.g. vibration, pressure, stretching)
  • in sensory neurons
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4
Q

What are voltage-gated channels?

A
  • open/close in response to changes in membrane potential

- in axons (b/c this is where APs are propagated!)

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5
Q

What are graded potentials?

A
  • occur in response to a stimulus
  • local deviations form resting potential of -70mV
  • if sufficient to reach threshold, will trigger an AP
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6
Q

What are action potentials?

A
  • occurs when local membrane potential becomes more positive than -55mV
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7
Q

Where do graded potentials usually occur? What type of ion channels do they involve?

A

dendrites and cell body of a neuron; mechanically gated + ligand-gated

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8
Q

C/C hyperpolarization and depolarization

A

H - membrane becomes more negative than -70mV (resting potential); further away from threshold –> less likely to trigger AP

D - membrane becomes less negative than -70mV; closer to threshold –> more likely to trigger AP

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9
Q

Why does a stronger stimulus cause a larger graded potential than a weaker stimulus?

A

because more ion channels will open up

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10
Q

What kind of ion channels do APs involve?

A

voltage-gated Na+ and K+ channels

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11
Q

Where is an AP initiated? What does it result with?

A

axon hillock and travels down length of axon; NT release at next synapse

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12
Q

What are the phases of an AP?

A

depolarizing and repolarizing phases

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13
Q

What occurs during the depolarizing phase of an AP?

A
  1. voltage-gated Na+ channels open

2. Na+ enters cell and changes MP to +30mV

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14
Q

What occurs during the repolarizing phase of an AP?

A
  1. Na+ channels inactivate (inflow stops)
  2. K+ channels open to let K+ out of cell
  3. MP returns to -70mV (repolarization)

*MP can hyperpolarize (reach -90mV)

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15
Q

What is the difference between absolute refractory and relative refractory period?

A

absolute - inactivated Na+ channels must return to resting state before they can be reopened; strong stimulus will not trigger another AP

relative - Na+ channels have returned to resting state (closed but can be opened again); suprathreshold stimulus can trigger an AP

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16
Q

What must happen to ‘reset’ the Na+ and K+ gradient so the neuron can fire another AP?

A

Na+/K+ pump

17
Q

What can increase the intensity of an AP?

A

higher frequency of APs + number of sensory neurons activated

18
Q

How do local anesthetics manipulate APs?

A
  • blocks voltage-gated Na+ channels of neurons from opening

- prevents AP generation so pain sensations don’t get transmitted to brain

19
Q

What is the difference between an electrical synapse and a chemical synapse?

A

E - ionic current spreads via gap junctions

C - transfer from presynaptic to postsynaptic cells; involve NT + receptors

20
Q

What are the 2 effects of a NT?

A

excitatory and inhibitory

21
Q

How does an excitatory effect affect ion channels?

A

NT causes opening of ligand-gated Na+ channels; triggers depolarization

22
Q

How does an inhibitory effect affect ion channels?

A

NT causes opening of ligand-gated K+ or Cl- channels; triggers hyperpolarization

23
Q

What is the difference between spatial summation and temporal summation?

A

S - NTs released from several end bulbs onto one neuron

T - NTs released from multiple firings of same end bulb

24
Q

What are the two classes of NT?

A
  1. small-molecule NTs

2. neuropeptides

25
Q

What are some examples of small-molecule NTs?

A
  • Ach
  • Glutamate (excitatory)
  • GABA + glycine (inhibitory)
  • norepinephrine, dopamine, serotonin
  • NO
  • adenosine
26
Q

What are some examples of neuropeptides?

A
  • endorphins & other opioid peptides

- substance P

27
Q

How do opioid peptides relate to substance P?

A

substance P enhances perception of pain; opioid peptides are natural painkillers by blocking release of substance P

28
Q

What are 3 mechanisms that prevent over-stimulation of postsynaptic cell? (terminate signal)

A
  1. diffusion
  2. enzymatic degradation
  3. uptake
29
Q

What are the 3 steps involved in the repair process of PNS neurons?

A
  1. chromatolysis
  2. Wallerian degeneration
  3. formation of a regeneration tube

BIOL 1191 (16 decks)

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