Module 1: Cellular And Molecular Neuroscience Flashcards
1
Q
Population (aka global) cellular recordings have excellent ________ resolution, but poor ________ resolution.
A
Temporal : spatial
2
Q
________ conduct action potentials away from the neuron cell body whereas ________ receive signals from other neurons which are carried towards the cell body.
A
Axons : dendrites
3
Q
What are homogenizing factors that influence ionic concentration across neural membrane and contribute to RMP?
A
- electrostatic pressure
- ionic motion driven by concentration gradients
4
Q
True or False. The concentration of positive ion species is greater inside of a neuron than outside.
A
False
5
Q
RMP results from the ______ distribution of ion species across the neural membrane
A
unequal
6
Q
How does diffusion of ions affect the RMP?
A
Each ion species has a differential permeability through the neural membrane which contributes to the unequal distribution of these ion species across the membrane.
7
Q
Leak ion channels are primarily responsible for what?
A
Establishing resting membrane potential
8
Q
True or false. The delay in synaptic transmission is shorter in electrical synapses than in chemical synapses.
A
True
9
Q
True or false. Graded potentials of the sarcolemma are termed end-plate potentials (EPPs).
A
True
10
Q
True or false. Neural activity at the NMJ always results in depolarization of the sarcolemma.
A
True
11
Q
True or false. The NMJ is the synapses between multiple motor neurons and a single skeletal muscle fiber.
A
False
12
Q
True or false. The NMJ contains nicotinic acetylcholine receptors located on the postynaptic membrane (sarcolemma).
A
True
13
Q
True or false. The size of the synaptic cleft in chemical synapses is smalller than those of electrical synapses.
A
False
14
Q
True or false. All chemical synapses utilize acetylcholine (ACh) are their main neurotransmitter.
A
False
15
Q
True or false. Only electrical synapses require a change in membrane voltage in order to induce transmission.
A
False
16
Q
True or false. Leak ion Chanel’s are primarily responsible for generating action potentials.
A
False, they establish RMP
17
Q
Do resting membrane potentials require energy to maintain?
A
Yes, ATP for ion pumps
18
Q
Type of neuron that has a single axon and contains multiple dendrites extending from the
soma (majority of CNS neurons)
A
Multipolar neuron
19
Q
Type of neuron that contains a single process extending from the soma that can branch (peripheral and central portions) to form dendrites and axon terminals
A
Pseudounipolar/unipolar
20
Q
Type of neuron that contains two processes, one axon and one dendrite, extending from the
soma
A
Bipolar neuron
21
Q
Multiple neuron cell bodies in the CNS are called:
A
Nuclei
22
Q
Multiple axonal processes that are anatomically or functionally distance in the CNS are called:
A
Tracts
23
Q
Multiple neuron cell bodies in the PNS are called:
A
Ganglia
24
Q
Multiple axonal processes that are anatomically or functionally distance in the PNS are called:
A
Nerves
25
What are the 5 principles of contact theory?
- neuron is elementary structural and signaling unit of nervous system
- dynamic polarization i.e. information received at one end, travels unidirectional to opposite end
- Synapses are specialized junctions where axon terminal (sending end) is in close contact to receptive end of another neuron
- connection specificity, meaning individual neuron will only communicate with synaptic contacts on specific regions of
specific cells
- neural/synaptic plasticity is a phenomenon neuron connections can be modified by experience
26
Where do graded potentials occur?
At dendrites and the soma
27
Where do action potentials occur?
initiated at a region adjacent to the axon hillock (A-H) and travel along the axon toward the terminal button
28
What membrane voltages rely on the activity of ion channels located throughout the plasma membrane?
Both graded and action potentials
29
What type of neuron population recording detects the magnitude and gross location of electrical activity in cortical regions and is performed in conjunction with a cognitive task?
EEG, electroencephalography
30
What type of neuron population study measures muscle
response or electrical activity in response to a nerve’s stimulation of the muscle? Utilized to detect neuromuscular abnormalities.
EMG (electromyography) & nerve conduction studies
31
What type of neuron population recording reflects the activity of the brain in response
to a stimulus? I.e reflects summed postsynaptic potentials of multiple neurons that have been activated.
ERP (event-related potential)
32
What kind of electrical activity is recorded with an extracellular single-unit micro-electrode?
all-or-none action potentials (APs)
33
What kind of electrical activity is recorded with an intracellular single-unit micro-electrode?
resting membrane potential (RMP), graded potentials (EPSPs, IPSPs) and APs
34
What kind of electrical activity is recorded with “patch clamp” single-unit micro-electrode?
ionic current not voltage of either a single or a group of ion channels
35
What is the resting membrane poetical of neurons in millivolts?
~ -70 mV, although RMP is typically between -40mV to -90mV depending on neuron size
36
In resting state, neurons are considered to be _____.
Polarized
37
What are anti-homogenizing factors that influence ionic concentration across neural membrane and contribute to RMP?
- differential permeability of ions that utilize ion channels
- active membrane-bound transporters, mainly the sodium-potassium pump
38
Which passes more readily through ion channels in the neural membrane, sodium or potassium?
Potassium (and also chloride) readily passes through the membrane
Sodium passes with difficulty
39
How does the resting membrane potential arise and maintain?
by the differences between the intracellular and extracellular concentrations of Na+, K+, and Cl- ions, as well as the negative charges of the protein ions trapped inside the cell.
40
What is the electrostatic force on chloride through neural membrane?
negative internal potential drives Cl- ions out of the cell
41
How does concentration affect diffusion of chloride at the neural membrane?
Because electrostatic forces are driving Cl- out, they accumulate outside the cell and the concentration gradient forces them back in
42
How does concentration affect diffusion of sodium at the neural membrane?
The neural membrane is resistant to diffusion of Na+ so extracellular concentration is high and drives Na+ into the cell
43
How does electrostatic pressure affect the diffusion of Na+ at the neural membrane?
negative internal resting potential drives Na+ ions into the cell
44
How do transporters affect sodium and potassium concentrations?
sodium-potassium pumps maintain:
- high extracellular Na+ concentration by pumping out Na+ ions at the same rate that they move in
- high intracellular K+ concentration by pumping K+ ions into the
neuron at the same rate that they move out
45
How does electrostatic pressure affect the diffusion of K+ ions at the neural membrane?
internal negative potential drives K+ ions back into the cell
46
How does concentration affect the diffusion of K+ at the neural membrane?
High internal concentrations of K+ cause them to move out
47
Characteristics of leak/leakage ion channels:
- Open even in a resting state
- Selective for a single ion species
- Contribute to the RMP
- ions follow concentration gradient
48
Characteristics of gated ion channels:
- Closed until opened by stimulus (voltage, ligand, sensory
stimuli)
- Can be selective for one or multiple ion species
- Necessary for graded and all-or-none action potentials
(APs) and neurosecretion
- can have depolarizing and hyperpolarizing effects
49
Where are leak/non-gated channels located in the plasma membrane of neurons?
on the cell body, dendrites, and along
| the axon.
50
Where are ligand-gated channels located in the plasma membrane of neurons?
on the cell body and dendrites of the neuron.
51
Where are voltage-gated channels located in the plasma membrane of neurons?
- on the axon hillock, all along unmyelinated axons,
and at the nodes of Ranvier in myelinated axons
- terminal button
52
The target of a presynaptic neuron may be :
another neuron, a region of a muscle, or a secretory cell.
53
What are electrical synapses?
Communication that allows for direct cell to cell communication via the flow of electrical current through specialized membrane channels (pores) that connect two cells
54
The intercellular region between sending and receiving cell.
Gap junction
55
The center core of a gap junction is formed by six subunits called:
Connexins, which are integral membrane proteins
56
The hexameric complex that forms the center pore of a gap junction:
Connexon
57
What is the direction of transmission at gap junctions?
Bidirectional
58
Where is transmission of signal more rapid, electrical or chemical synapse?
Electrical
59
Which intercellular region/synaptic cleft is larger, electrical or chemical synapse?
Chemical synapse, therefore transmission is slower than electrical synapses
60
Which class of synapse structure allows for synchronized electrical activity of a population of cells?
Electrical synapse
61
Which class of synapse structure allows for non-selective movement of molecules from one cell to another?
Electrical synapse
62
What are chemical synapses?
A type of communication that allows for cell to cell communication via the release of chemical
agents (neurotransmitters) by the presynaptic neuron which are received by receptors on the surface of the postsynaptic neuron
63
Chemical synapse morphology in which a presynaptic axon synapses on the shaft of a dendrite or on a dendritic spine of a postsynaptic neuron
Axodendritic
64
Chemical synapse morphology in which axon synapses on the soma or cell body
Axosomatic
65
Chemical synapse morphology in which axons synapse on axons
Axoaxonic
66
What is the most common synaptic arrangement?
Axodendritic
67
Axodendritic synapses are also known as:
Gray type I
68
Axosomatic synapses are also known as:
Gray type II
69
Which synapses have larger synaptic
| cleft and are often excitatory?
Axodendritic
70
Which synapses have smaller synaptic cleft and are often inhibitory?
Axosomatic
71
chemical synapses can be further subdivided into two distinct categories based on distance between presynaptic and postsynaptic neurons. What are they?
- directed, release and reception sites are in close proximity
- non-directed, release site is some distance from the site of reception
72
A chemical synapse between the extrafusal and intrafusal muscle fibers of striated and skeletal muscles
Neuromuscular junction
Aka: motor end-plates or myoneural junctions
73
What is a motor unit comprised of?
The single alpha motor neuron and all of
| the individual skeletal muscle fibers that it innervates
74
What dictates the number of muscle fibers in a motor unit?
The size and function of a muscle.
I.e. fine motor control requires fewer muscles in motor unit.
75
All NMJ’s use what neurotransmitter?
Acetylcholine (Ach)
76
What are the receptors fro acetylcholine on the sarcolemma?
Nicotine acetylcholine receptors (nAChR)
77
What is sarcolemma?
Muscle fiber plasma membrane
78
Describe the morphology of the Nicotinic ACh receptor.
```
- A large protein
consisting of 5 subunits
(2α, 1β, 1y, 1 delta)
• α subunits contain an
ACh-binding region
• Center pore functions
as ion channel for the
passage of Na+ ions
```
79
What is the difference between transmitter ligands of CNS chemical synapses and PNS chemical synapses?
The CNS uses multiple small and large neurotransmitter while the PNS uses only the small neurotransmitter, acetylcholine
80
What is the difference between the graded response of CNS chemical synapses and PNS chemical synapses?
The CNS chemical synapses can produce excitatory post synaptic potential (EPSP) vis depolarization or inhibitory post synaptic potential (IPSP) via hyperpolarization, while the PNS chemical synapses will produce only end plate potential (EPP) via depolarization
81
Which can produce excitation and inhibition, CNS or PNS chemical synapse?
CNS synapse
82
How does an excitatory postsynaptic potential (EPSP) increase the likelihood that a neuron will fire?
By moving the membrane potential closer to the threshold of excitation
83
How does an inhibitory postsynaptic potential (EPSP) decrease the likelihood that a neuron will fire?
By moving the membrane potential farther from the threshold of excitation
84
Binding of neurotransmitter molecules to their specific receptor proteins causes what?
Opening of ion channels which can either have a depolarizing or hyperpolarizing effect
85
Describe the properties of EPSPs and IPSPs at the postsynaptic membrane
- they have graded potentials with varying amplitudes
- travel passively but rapidly from sit of origin (dendrite/cell body)
- they are decremental meaning they decrease in amplitude as they travel along the axon
86
Sum of IPSPs and EPSPs needs to be sufficient to depolarize the membrane to a level called _____ to generate an action potential
the threshold of excitation
87
What is the value of the threshold of excitation to generate an action potential?
~ -55mV
88
Where is the action all potential generated?
Adjacent to the axon hillock
89
Action potentials are considered all or none. What does this mean?
They are NOT graded, therefore their magnitude is consistent
90
The magnitude of an action potential is directly proportional to what?
The concentration of Na+ ions inside and outside the cell
91
What mediates the production and conduction of action potentials by altering the membrane potential?
Voltage-gated ion channels
92
The majority of postsynaptic potentials (PSPs) produced are ________, meaning they are below the threshold for generating an action potential.
subthreshold
93
Since the majority of postsynaptic potentials produced are subthreshold, they must be combined in a process called _____
Summation
94
What are the two ways postsynaptic potentials can be summed?
Temporally (over time)
| Spatially (over space
95
Multiple PSPs from different synapses are combined to form larger PSP
Spatial summation
96
multiple PSPs produced in rapid succession at the same
| synapse combine to form a larger PSP
Temporal summation
97
What are the phases of an action potential?
1. Resting potential
2. Threshold
3. Depolarization phase
4. Repolarization phase
5. Undershoot
6. Refractory period
7. Return to resting state
98
Describe the resting state of an action all potential
Voltage-gated Na+ and K+ ion channels are closed and leak ion channels are open. The neuron’s membrane potential is at its RMP (~-70 mV).
99
Describe the threshold phase of the action potential
One or more EPSPs open some voltage-gated Na+ ion channels. If the threshold of excitation is reached, more Na+ ion channels will open, and an action potential is triggered.
100
Describe the depolarization phase of an action potential?
With Na+ ion channels now open, Na+ ions continue to rush into the cell, which alters the membrane potential (making it less negative/more positive). However, K+ ion channels are still closed.
101
Describe the repolarization phase of an action potential?
Voltage-gated Na+ ion channels become inactive while K+ ion channels begin to open. K+ ions rush out of the cell, which changes the membrane potential (making it more negative/less positive).
102
Describe the undershoot phase of an action potential?
Na+ ion channels are closed and K+ ion channels are closing but slowly. K+ ions are still leaving the cell through the remaining open channels, making the membrane potential more negative/less positive (beyond the normal RMP).
103
Describe the refractory period of an action potential?
In the wake of the AP, Na+ ion channels are deactivated and K+ ion channels are activated for a brief time. These changes make it impossible or very difficult for the neuron to produce an AP at this time.
104
The period from the initiation of the action potential to immediately after the peak, during which another EPSP (no matter how strong) cannot lead to the production of an AP. This absolute refractory period lasts about 1-2 ms.
Absolute refractory period
105
Following the absolute refractory period, Na+ channels begin to recover from inactivation and the relative refractory period begins, during which a stronger than normal stimulus is needed in order to elicit an action potential.
Relative refractory period
106
How does an action potential travel along an axon differently from how postsynaptic potentials travel?
Action potentials are non-decremental and slower than postsynaptic potentials
107
Axons wrapped in fatty tissue are said to be
Myelinated
108
What is the function of myelin
Increase speed of axon potential
109
Gaps between the myelin where Na+ channels are concentrated
Nodes of Ranvier
110
What is saltatory conduction?
The transmission of action potential on myelinated axons that jumps form node to node
111
Other than myelination, what affects the conduction speed of an action potential alone the axon
Size, specifically diameter
| Large diameter axons conduct faster
112
What criteria must a substance meet in order to be considered a neurotransmitter?
- must be present in the presynaptic neuron
- must be released in response to presynaptic depolarization (Ca2+ dependent)
- specific receptors for the substance must be present on the postsynaptic membrane
113
neurotransmitters are contained in ______ within the presynaptic neuron
Vesicles
114
What kind of effect can a neurotransmitter have on the receiving cell?
- inhibitory
- excitatory
- both
115
Large molecule neurotransmitters
Neuropeptides (3-36 AA’s long)
116
What category of neurotransmitter tends to modulate slower ongoing synaptic functions and generally binds only to metabotropic receptors?
Large-molecule neurotransmitters/neuropeptides
117
What category of neurotransmitter tends to mediate rapid synaptic action and can bind to either ionotropic or metabotropic receptors?
Small-molecule neurotransmitters
118
What are the 4 most common amino acid neurotransmitters?
Glutamate
Aspartate
Glycine
Gamma-aminobutyric acid (GABA)
119
What is the most prevalent inhibitory neurotransmitter?
GABA
120
What are the 4 monoamine neurotransmitters?
- catecholamines (dopamine, epinephrine, norepinephrine)
| - indolamines (serotonin/5-HTP)
121
Which are larger amino acid neurotransmitters or monoamine neurotransmitters?
Monoamine
122
What is the main neurotransmitter at neuromuscular junctions?
Acetylcholine
Also found at synapses in ANS and CNS
123
What are some examples of unconventional neurotransmitters?
Soluble gases such as Nitric oxide and carbon monoxide
| Endocannabinoids which are similar to THC
124
Where are small- molecule neurotransmitters synthesized?
In the cytoplasm of the presynaptic terminal button
125
Where are large-molecule NTs/neuropeptides synthesized?
In the cytoplasm of the cell body on ribosomes
126
Enzymes needed for synthesis of small-molecule NTs are produced in the cell body and are transported along microtubules to the terminal button via what?
Slow axonal transport
127
Neuropeptides are packaged into ________ core synaptic vesicles by the Golgi complex in the ________.
- dense core
| - cell body
128
Small molecule NTs are packaged into ________ core synaptic vesicles by the Golgi complex in the ________.
- clear core
| - terminal button
129
Vesicles containing neuropeptides are transported along microtubules to the presynaptic terminal button via ______
Fast axonal transport
130
Many neurons synthesize and release two or more different neurotransmitters. Low-frequency stimulation often releases only ______ whereas high-frequency stimulation is required for the release of ________.
- small-molecule neurotransmitters
| - neuropeptides
131
What is Dale’s Rule?
A single neuron produces, packages, and releases (after an AP) the same chemical transmitter(s) at ALL of its synapses.
132
Nearly all instances of coexistence are of _______ and _______.
Small molecule NTs and large neuropeptide
133
The mechanisms that facilitate the release and recycling of synaptic vesicles at the terminal button are dependent on what?
Ca2+
134
Exocytosis of neurotransmitter is rapidly followed by
Endocytosis
| This allows for rapid release and recycling of neurotransmitter
135
Vesicles congregate near docking sites of the presynaptic membrane called _______, which contain clusters of voltage-gated Ca2+ channels
- active zones
| - voltage-gated Ca2+ channels
136
Vesicles containing neurotransmitter are anchored in place near the active zones by proteins called _______.
synapsins
137
During an action potential, the membrane is depolarized, causing ion channels to open allowing an influx of Ca2+ into the terminal. This Ca2+ influx leads to:
phosphorylation of the synapsin proteins
138
What is the purpose of phosphorylation of synapsins?
```
It readies vesicles for exocytosis by allowing them to dock at the presynaptic membrane facing the synaptic cleft, fuse with it, and release their transmitters into the
synaptic cleft (exocytosis)
```
139
The # of vesicles released by a neuron
Quanta
| Which is directly related to the level of Ca2+ within the terminal
140
Low frequency stimulation often only increases the Ca2+ concentration near the membrane, which favors the release of ________.
small molecule NT only
141
Higher frequency stimulation leads to a more general increase in calcium which will release ________.
both small molecule NTs and neuropeptides
142
Small-molecule NTs activate either ionotropic or metabotropic receptors and function to transmit _________ signals
rapid and brief excitatory or inhibitory
143
Large-molecule NTs/ Neuropeptides (NPs) bind to metabotropic receptors that act via 2nd messengers and function to transmit ______ signals
slow and long-lasting
