PHGY 209 > Nerve/Synapse > Flashcards

Nerve/Synapse Flashcards

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1
Q

The nervous system comprises around ______(amt) neurons

A

100 billion

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2
Q

Name 3 characteristics about neurons

A
  1. Neurons are electrical cells
  2. Neurons talk to each other
  3. Neurons come in an enormous range of shapes and sizes
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3
Q

Where does communication in neurons take place?

A

Synapse

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4
Q

How many axon does each neuron have?

A

1

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5
Q

The inside of a typical neuron is __ - __ mV, compared to the outside

A

-60 to -70mV

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6
Q

The ___________ is caused by a small excess of negatively charged ions inside the cell

A

Resting membrane potential

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7
Q

The resting permeability to K+ is caused by ____ channels

A

Leak

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8
Q

Are leak channels open or closed at resting membrane potential?

A

Open

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9
Q

The membrane potential is determined by _______ gradients and ______ permeabilities of membrane to different physiological ions

A

Concentration

Relative

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10
Q

What changes a lot? Concentration gradients or permeabilities?

(Membrane potential)

A

Permeabilities

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11
Q

What is the dominant permeability at rest?

A

Potassium

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12
Q

What are action potentials?

A

Brief electrical impulses

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13
Q

How do action potentials travel?

A

Usually starts at the initial segment of axon and then propagate down the length of the axon to the presynaptic terminals.

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14
Q

The action potential is a transient ___ (polarizing/depolarizing) spike that moves down the axon

A

Depolarizing

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15
Q

At the action potential peak, the membrane potential approaches E_ (Na+/K+)

A

Na+

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16
Q

What causes the rising (depolarizing) phase of the action potential?

A

Sodium ions flowing into the cell via voltage-gated sodium channels

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17
Q

What are sodium channels’ 3 critical properties?

A

1) They are closed at the resting membrane potential but open when membrane depolarizes

2) They are selective for Na+

3) The open channel rapidly inactivates, stopping the flow of Na+ ions

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18
Q

What 2 factors contribute to the falling phase of the action potential?

A

1) Sodium channel inactivation

2) delayed activation of voltage-gated potassium channels

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19
Q

What is the absolute refractory period?

A

Period after action potential in which the sodium channels are inactivated and the membrane is completely unexcitable

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20
Q

Which period is longer, absolute or relative refractory period?

A

Relative

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21
Q

What does tetrodotoxin do?

A

Inhibits sodium channels

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22
Q

What does batrachotoxin do?

A

Activates sodium channels

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23
Q

What are examples of local anaesthetics?

A

Lidocaine
Benzocaine
Tetracaine
Cocaine

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24
Q

What are examples of antiepileptics?

A

Phenytoin (Dilantin)

Carbamazepine (Tegretol)

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25
Myelin is formed by _____ cells (in the PNS) or ________ (in the CNS).
Schwann Oligodendrocytes
26
What do nodes of Ranvier contain?
Very high concentrations of voltage-graded sodium channels
27
Most synapses are on ____ (part of cell)
Dendrites
28
Activation of voltage-gated _____ channels triggers neurotransmitter release
Calcium
29
_______-gated ion channels are postsynaptic receptors for transmission at brain synapses
Ligand
30
Excitatory postsynaptic potential (EPSPs) ______ the postsynaptic membrane
Depolarize
31
Inhibitory postsynaptic potential (IPSP) ___________ the postsynaptic membrane
Hyperpolarizes
32
The main excitatory neurotransmitter in the brain is _______
Glutamate
33
Rapid excitatory transmission at synapses is primarily due to the actions of glutamate on 2 types of ______ glutamate receptors: 1) _____ receptors 2) _____ receptors
Ionotropic 1) AMPA 2) NMDA
34
AMPA receptors are responsible for the ‘’fast’’ ____ at excitatory synapses
EPSP
35
NMDA is blocked by **what** at resting membrane potential?
Mg2+
36
______ expels Mg2+, enabling the pore to conduct (NMDA receptors)
Depolarization
37
The open pore (for NMDA) is highly permeable to __ as well as monovalent cations
Ca2+
38
At -70mV, almost all synaptic current at an excitatory glutamate synapse is carried by Na+ through ____ receptors. However, if the postsynaptic membrane is depolarized, a substantial Ca2+ current flows through ____ receptors.
AMPA NMDA
39
Synaptic plasticity involves ____ receptors
NMDA
40
Long-term potentiation (LTP) is a model of…
Synaptic plasticity
41
Excitotoxicity involves _____ influx through ____ receptors
Calcium NMDA
42
True or false? High concentrations of glutamate is good for neurons
False! It is toxic
43
The main inhibitoral neurotransmitter in the brain is ____
Γ-aminobutyric acid (GABA)
44
The postsynaptic receptor responsible for the IPSP is called the ____ receptor
GABAa
45
Activation of GABAa receptor causes an influx of __, which ______ the postsynaptic membrane
Cl- Hyperpolarizes
46
Neurons that release neuromodulators often originate in small _____ or _____ nuclei.
Brainstem Midbrain
47
What are **ionotropic receptors**?
Ion channels that open in response to binding of small molecules (e.g. neurotransmitters) to receptor sites on their **external** surfaces
48
True or false? The depolarization caused by a single EPSP is large enough to depolarize the axon initial segment to threshold.
False, it is too small.
49
Approximately how many EPSPs must sum at the initial segment to initiate an action potential?
From 50 to 100 (Can come from multiple synapses acting in synchrony and/or from individual synapses, activated at high frequencies)
50
What is synaptic plasticity?
When highly active excitatory synapses become stronger (i.e. the EPSPs become stronger)
51
________ is likely to contribute to neuronal degeneration after stroke and in some neurodegenerative diseases.
Excitotoxicity
52
Excitatory inputs tend to be located on _______ (part of cell) Inhibitory inputs are often clustered on or near the ______ (part of cell) where their inhibitory effect is maximal.
Dendritic spines Cell soma
53
Glutamate synapses have both _____ receptors and ________ receptors
Ionotropic (AMPA and NMDA) Metabotropic glutamate (mGluR’s)
54
2nd messengers activate a range of cellular proteins, including … (3).
1. Ion channels 2. Protein kinases 3. Transcription factors
55
What is the GabaB receptor?
The metabotropic GABA receptor
56
What do neuromodulators do?
Modulate global neural states, influencing alertness, attention and mood. (Note: not directly involved in the fast flow of neural information)
57
Name some neurotransmitters that interact mainly (or entirely) with metabotropic receptors. (Note: these are also referred to as **neuromodulators**)
Dopamine Serotonin Norepinephrine Neuropeptides (such as endorphins)
58
What are neuromodulators?
Neutrotransmitters that interact mainly, or entirely with metabotropic receptors.
59
Neurons that release neuromodulators often originate in __________ or ________ (parts of brain). Their axons project diffusers throughout the brain.
Small brainstem Midbrain nuclei
60
Antidepressants such as Prozac affect _____ transmission. Amphetamines, cocaines and other stimulants typically affect _______ and ______ transmission.
Serotonergic Dopamine Norepinephrine
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