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Biology 201 > Topic F > Flashcards

Topic F Flashcards

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1
Q

What are the four proteins needed for an action potential to occur?

A
  • Na+ and K+ pumps
  • K+ Leak Channels
  • Voltage-gated K+ Channels
  • Voltage gated Na+ Channels
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2
Q

What are the parts of a neuron?

A
  • cell body
  • dendrites
  • axon (less than 1mm to more than 1m long)
  • terminal branches of axons
  • nerve terminal
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3
Q

What is the “usual” resting membrane potential

A

-70.0mV

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4
Q

An axon at resting membrane potential is more _____ on the inside and more ____ on the outside

A

negative; positive`

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5
Q

What is the resting membrane potential maintained by?

A
  • Na+ & K+ pumps

- K+ Leak channels

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6
Q

Potassium channels are ______

A

Homotetramers

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7
Q

Sodium channels are ____ with ___ number of domains

A

monomers; 4

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8
Q

K+/Na+ channels in a neuron axon – Characteristics

A

shape: Channel
Energy - passive
Direction - uniport
Regulation: gated

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9
Q

Na+ channels open _____ in comparison to K+ channels when the membrane potential changes

A

Quicker

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10
Q

K+/ Na+ channels open at a membrane potential of ____

A

above -40 mv
(+) at the cytosol
(-) inside the neuron
Plasma membrane is depolarized

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11
Q

K+/ Na+ channels close at a membrane potential of ____

A

below -40 mv
(-) at the cytosol
(+) at inside the neuron
Plasma membrane is at rest

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12
Q

how do K+/ Na+ channels open

A

Gates of channels are wings that can rotate; (+) part of the wing moves towards (-) environment

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13
Q

What are the three phases of a sodium channel

A
  • Closed: Plasma membrane at rest
  • open: Membrane ois depolarized
  • inactivated: Membrane is at refractory
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14
Q

What is the inactived stage of a voltage gated Na+ channel

A

(-) inside the neuron
(+) at inside the cytosol
membrane Refractory

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15
Q

Activity of Na+/K+ pumps

A

(few)

Always working

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16
Q

Activity of K+ leak channels

A

Open and close randomly (few)

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17
Q

Activity of Voltage gated K+ channels

A

close, open, close

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18
Q

Activity of Voltage gated Na+ channels

A

close, open, inactivate, close

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19
Q

What are the stages of an action potential

A

1) Subthreshold depolarization
2) Threshold depolarization
3) Depolarization Phase
4) Repolarization Phase
5) Refractory Period

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20
Q

Subthreshold depolarization

A

@ resting membrane potential

1 Na+ channel opens nothing happens b/c of the K+ leak channels thats already open

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21
Q

Threshold depolarization

A

Several Na+ channels open, an influx of Na+ overcomes the outflow of K+ allowing the threshold membrane potential to be reached (-40mV).

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22
Q

Depolarization phase

A

Once threshold membrane potential is reached (-40mV), all the Na+ channels open, Membrane potential rises to +40mV.

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23
Q

Repolarization Phase

A

Na+ channels inactivate, K+ channels open, this drives the membrane pot. back down

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24
Q

Refractory Period

A

nothing can happened b/c Na+ channels are inactive, K+ channels open
After Membrane potential is below -40mV for a time Na+ and K+ channels close

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25
How does an AP travel on a regular axon
- voltage gated sodium channels allow Na+ to go into axon deploarizing the membrane causing passive depolarization to spread, which is followed by an outflow of K+ ions into the cytosol Speed of travel -- ~5m/s
26
How does an AP travel on a giant axon
Larger diameters of axons -- quicker APs Found in large invertebrates Speed -- ~100m/s
27
How does an AP travel on a myelinated axon
myelinated cells (myelin sheath) that wrap around the neurons axon insulating it AP "jumps" between nodes of ranvier speed ~100m/s
28
what is the function of SNAREs in Presynaptic Neurones
Activated by Ca+ (indirectly) | fusses synaptic versicle with presynaptic membrane
29
what is the function of Vesicles in Presynaptic Neurones
Carry neurotransmitters to presynaptic membrane
30
what is the function of SNAREs in Presynaptic Neurones
Activated by Ca+ (indirectly) | fusses synaptic versicle with presynaptic membrane to release neurotransmitters
31
what is the function of Acetylcholine receptors (AChR) in Postsynaptic Neurones
Ion channels or open adjacent ion channels Made of negatively charged amino acid side chains Open when neurotransmitters bind to it.
32
Electrical Synapses
Na+ moves through gap junctions | Advantages: speed
33
Chemical synapses
Neurotransmitters export from cell | Advantages: integration of multiple signals
34
what is the function of Acetylcholinesterase (AChE) in Postsynaptic Neurones
Degradation of ACh removed Neurotransmitters from synaptic cleft (break down with enzymes)
35
what is the function of Excitatory synapses in Postsynaptic Neurones
CASUES AN AP synapse in which an action potential in a presynaptic neuron increases the probability of an action potential occurring in a postsynaptic cell
36
what is the function of inhibitory synapses in Postsynaptic Neurones
opposite to Excitatory synapses
37
what is the function of postsynaptic potentials in Postsynaptic Neurones
Each active synapse generates a tiny post synaptic potential (PSP) from excitatory and inhibitory synapses which then combine
38
what is the function of spatial summation in Postsynaptic Neurones
The combination of PSPs from DIFFERENT presynaptic neurons
39
what is the function of temporal summation in Postsynaptic Neurones
the combination of PSPs from ONE presynaptic neurons
40
what is the function of combined PSPs in Postsynaptic Neurones
TS and SS combined which then change the membrane potential of neurones
41
what is the function of encoding at the axon hillock in Postsynaptic Neurones
generates output of postsynaptic neurones Magnitude of combined PSP --> frequency of axon potentials low, medium, high combined PSPs
42
Cl- enters the postsynaptic neuron --->
Hyperpolairzation
43
Neurotransmitters are removed from synaptic cleft by..
diffusion -- Wonder away degradation -- Break down w/ enzymes Reuptake -- import back into a cell
44
Low combined PSP
No action potential Voltage Gated Na+ and K+ channels are closed Minimal axon membrane potential (mV)
45
High combined PSP
Lots of action potential Voltage gated Na+ and K+ channels are open Many axon membrane potential (mV)
46
Moderate combined PSP
action potentials are possible but iinfrequent
47
____ refractory periods when combined PSP is ___ above threshold
extend; Slightly
48
What are the steps in activating a skeletal muscle cell?
1) Voltage Gated Ca+2 open with the activation of the nerve impulse resulting in a release of ACh 2) ACh binds to AChR ---> localized memb. depolarization 3) Voltage gated Na+ opens --> entire surface including T-tubules depolarizes 4) Voltage Gated Ca+2 open 5) Mechanically gates Ca+2 --> Ca+2 enter cytosol
49
The Binding of ___ to the troponin complex exposes the ____ ____ site.
Ca+2; myosin binding
50
What are the steps in activating a skeletal muscle cell?
1) Voltage Gated Ca+2 open with the activation of the nerve impulse resulting in a release of ACh 2) ACh binds to AChR ---> localized memb. depolarization 3) Voltage gated Na+ opens --> entire surface including T-tubules depolarizes 4) Voltage Gated Ca+2 open 5) Mechanically gates Ca+2 --> Ca+2 enter cytosol
51
steps for recovery of an activated skeletal muscle cell...
- ACh removed from synapse - Channels close - Ca+2 removed from cytosol - Tropomyosin block myosin binding sites
52
Ca+2 removed from cytosol with ____ & ____ Ca+2 transporters
ATP powered; Na+ gradient powered
53
How are skeletal muscles controlled
Need multiple signals/APs (temporal summation) to contract a muscle
54
Do muscle cells also do spatial summation?
No, only temporal
55
What is one motor unit?
1 motor neuron and several muscle cells
56
cardiac muscle cells vs skeletal muscle cell
- cardiac muscle cells are controlled by pacemaker cell not motor neuron -- sends pulses of (+) ions - wave of contractions to heart muscle cells -- spreads across heart - Connected with electrical synapses --gap junctions - Brain and adrenaline control the heart rate - cardiac muscle cells contract for a longer time
57
steps for recovery of an activated skeletal muscle cell...
- ACh removed from synapse - Channels close - Ca+2 removed from cytosol - Tropomyosin block myosin binding sites
58
Agonist
Activates
59
Antagonist
Blocks
60
Activator toxin
normal binding to site of enzyme; Increases activity
61
Competitive inhibitor toxin
Binds to active site of enzyme to decreases activity
62
Noncompetitive inhibitor
decreases activity
63
Noncompetitive inhibitor
binds at an allosteric site separate from the active site of substrate binding to decreases activity
64
Toxin: BoNT/A
Enzyme that cleaves SNAREs -- cuts SNARE thats necessary for release of ACh vesicles (Prevents release of neurotransmitters)
65
Toxin: Sarin
Competitive inhibitor -- mimics ACh and Inhibits AChE Involuntary muscle contractions (Prevents removal of neurotransmitters)
66
Toxin: Charybdotoxin
AChR Antagonist -- Blocks certain AChRs Muscle paralysis (prevents activation of receptors)
67
Toxin: Nicotine
AChR Agonist -- mimics ACh and activates certain AChRs Increases activity in brains pleasure center -- produces euphoria feeling and adrenaline response (inappropriate activation of receptors)
68
Humans have __ different AChRs
11
69
Toxin: BoNT/A The effect?
- Enzyme that cleaves SNAREs -- cuts SNARE thats necessary for release of ACh vesicles - Muscle paralysis; Treat people who have uncontrolled muscle contractions; Botox (Prevents release of neurotransmitters)
70
Toxin: Sarin The effect?
- Competitive inhibitor -- mimics ACh and Inhibits AChE - Involuntary muscle contractions (Prevents removal of neurotransmitters)
71
Toxin: Charybdotoxin The effect?
- AChR Antagonist -- Blocks certain AChRs - Muscle paralysis (prevents activation of receptors)
72
Toxin: Nicotine The effect?
- AChR Agonist -- mimics ACh and activates certain AChRs - Increases activity in brains pleasure center -- produces euphoria feeling and adrenaline response (inappropriate activation of receptors)
73
most dangerous neurotoxin? why?
BoNT/A; enzyme--> 1 molecule within a cell of the toxin can get rid of all the SNAREs
74
Nicotine activates AChRs on ____ and ___ cells
brain; adrenal
75
Nicotine activates AChRs which Causes voltage gates Ca+2 channels to ____ and ____ exocytosis of adrenaline
open; causes

Biology 201 (8 decks)

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