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Neurobiology 523 > Unit 1 > Flashcards

Unit 1 Flashcards

1
Q

specialization

A

adaptaton to serve a particular function

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2
Q

nervous system

A

network of cells that transmit signals throughout the body

-organize functions of the body
-characteristic cells
-networks of myriad functions

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3
Q

ganglion

A

cluster of neurons

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4
Q

neurophysiology

A

function of neurons; similar across neurons of every species

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5
Q

What is meant by neuron “activation?”

A

change in a neuron’s electrical activity

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6
Q

neuron doctrine

A

neurons are separate cells that communicate

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7
Q

neurons as a computational unit

A

neurons are computational units that comunicate with one another to achieve complex functions

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8
Q

synapse

A

site of communication between neurons

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9
Q

What do 86,000,000,000 neurons buy us?

A

-quadrillion synapses
-more neurons/connectivity = more brain power

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10
Q

connection between neurons/connections and brain power

A

more neurons/connections means more brain power

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11
Q

A specialized neuron is…

A

-suited to a particular function
-distinct from other neurons in its morphology
-distinct from other neurons in its physiology

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12
Q

dynamic polarization

A

idea proposed by Ramon y Cajal that activity propagates through the cell

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13
Q

neurites

A

the “wires;” a projection from a neuron’s cell body; specializations for transmitting signals

either axon or dendrite

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14
Q

soma

A

neuronal cell body; contain nucleus (genetic material), house organelles, and perform transcription and some translation (some in neurites)

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15
Q

dendrites

A

neurite responsible for receiving input from synapses, like an antennae

-“primary” dendrites connect to soma
-branches fork, giving arboreal appearance
-can be spiny

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16
Q

axon

A

neurite responsible for output; when neuron decides to activate, it transmits that information downstream via the axon to synapses

-neurons have a single axon
-branches can arise at right angles, more sprawling and less arboreal than dendrite
-can appear like beads on a string

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17
Q

dendritic arbor

A

collection of dendrites of a cell

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18
Q

primary dendrites

A

connect to the soma

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19
Q

dendritic spines

A

some dendrites are spiny, and synapses can form onto spines (vs. shaft) of a dendrite; afford compartmentalization (to regulate signaling) and can be grown and eliminated

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20
Q

proximal neurite

A

closer to soma; proximal dendrites are thicker than distal dendrites

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21
Q

distal neurite

A

farther from soma; distal dendrites are thinner than proximal dendrites

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22
Q

collaterals

A

term for branches of axons

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23
Q

axon initial segment (AIS)

A

proximal region of axon, attaches to axon hillock; where electrical signal in axon is generated, it is also enriched in proteins for sending this signal down the axon

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24
Q

axon hillock

A

site where axon connects to soma

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25
Q

axon terminals

A

swollen endings of axon, called bouton; half of a synapse and the site where neural activity in transformed into neurotransmitter release

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26
Q

neurotransmitter

A

chemical released by neuron to convey neural activity

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27
Q

synaptic vesicles

A

where neurotransmitters are packed; sent across synapse from presynaptic terminal to receptors on the postsynaptic terminal

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28
Q

synaptic cleft

A

gap between 2 cells where neurotransmitter is released

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29
Q

types (locations) of synaptic formation

A

1) axo-dendritic
2) axo-somatic
3) axo-axonic
4) dendro-dendritic

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30
Q

neuromuscular junction

A

special synapse between neuron (motor neuron) and muscle; high density of receptors ensures reliable response (i.e., very sensitive)

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31
Q

immunohistochemistry

A

powerful chemical approach to label microscopic structures (histology) using antibodies of the immune system; essentially allows visualization of highly specific, fine structures in nervous system

Can be defined by the following process:
1) Primary antibodies bind to an antigen (receptor) on structure of interest
2) Labeled secondary antibodies bind to the primary antibody
3) Complex soaked in substrate and exposed to color-changing enzyme

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32
Q

pyramidal neuron

A
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33
Q

bipolar neuron

A
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34
Q

chandelier neuron

A
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35
Q

double bouquet neuron

A
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36
Q

starburst amacrite neuron

A
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37
Q

tufted neuron

A
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38
Q

neuroglia (glia)

A

“nerve glue,” originally thought to control local environment of neurons; as varied and numerous as neurons, they signal and influence neural activity

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39
Q

glia vs. neurons

A

-glia have no synapses
-glia are less excitable than neurons
-glia are not typically polarized

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40
Q

astrocytes

A

“star cells” that contact blood vessels to regulate blood flow and support the blood-brain barrier

support neurons locally by…
-providing nutrients
-balancing ions, including pH
-removing neurotransmitter and ions from cleft

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41
Q

ependymal cells

A

line cavities in nervous system; motile cilia create flow in cerebrospinal fluid, providing nutrients and removing waste

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42
Q

myelinating cells

A

wrap axons of neurons with myelin to provide insulation and help signals propagate; give white matter its white (fatty) look

in brain/spinal cord: oligodendrocytes
in PNS: Schwann cells

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43
Q

oligodendrocytes

A

the myelinating cells of the brain/spinal cord; wrap axons with myelin to provide insulation and help signals propagate

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44
Q

Schwann cells

A

the myelinating cells of the PNS; wrap axons with myelin to provide insulation and help signals propagate

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45
Q

microglia

A

immune cells of the central nervous system, move to site of injury and perform phagocytosis (clean up waste)

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46
Q

EEG (electroencephalography)

A

changes in voltage on surface of brain can be detected with sensitive electrodes on scalp

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47
Q

voltage

A

measure of capability of charge to move between two points

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48
Q

membrane potential (Vm)

A

voltage or electrical potential across a membrane; difference in electrical potential inside vs outside the cell

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49
Q

polarization of neuron plasma membrane

A

neuron plasma membrane is polarized; inside of cell tends to be negative relative to outside (potential to move positive charge inwards)

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50
Q

How much of our energy consumption is contributed to the brain (creating voltage)?

A

about 20%; pure neuronal activity can burn a significant amount of calories (i.e., requires lots of energy)

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51
Q

balloonist theory

A

ancient view that fluid in ventricles inflated muscles via hollow nerves

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52
Q

signaling

A

transmission of information from one place to another; molecular signaling is ubiquitous, potent, and often slow (hormones)

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53
Q

Galvani

A

discovered electricity could make dissected legs of frog twitch; metal conducted electricity to exposed nerves (this implied that electricity could be used as a neural signal)

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54
Q

fast signaling with electricity

A

charged particles can transmit signals quickly through electricity; selective pressure to signal fast

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55
Q

Hodgkin and Huxley

A

recorded electrical activity from squid giant axon, serving as the first direct measurement of membrane potential

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56
Q

resting membrane potential

A

primes neurons to signal electrically; Vm = -65 mV; resting membrane potential is so low because of potassium leak channels that polarize the interior of the cell

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57
Q

spheres of hydration

A

when water surround NaCl and dissolves it; demonstrates how water dissolves ions

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58
Q

conductance (g)

A

the degree to which a material conducts electricity (e.g., high conductance opens ion channels); inverse of resistance

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59
Q

resistance (R)

A

inverse of conductance; R=1/g, in ohms

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60
Q

current (I)

A

directly proportional to voltage across two points and inversely proportional to resistance; I=V/R; lower resistance means more current flows

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61
Q

Ohm’s law

A

V=IR, or Voltage=Current*Resistance; for fixed voltage, current increases as resistance decreases

Important because it tells us:
1) If current can’t flow, there is no voltage
2) How voltage and current relate at a given resistance; if R is constant, V and I are proportional

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62
Q

plasma membrane

A

made up of phospholipids with hydrophilic heads and hydrophobic tails; allows proteins to be suspended in membrane and act as channels or pumps

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63
Q

alpha helix in plasma membrane

A

helps arrange hydrophobic R groups within the membrane

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64
Q

sodium “leak” channel

A

sodium can pass, but not other ions; lower conductance than potassium leak channels, which is why resting membrane potential is negative

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65
Q

synthesis of transmembrane proteins

A

synthesized in the rough endoplasmic reticulum (RER)

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66
Q

synthesis of other (non-transmembrane) proteins

A

synthesized on free ribosomes and are often found in the cytosol

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67
Q

electrochemical gradient

A

combination of diffusion and electrical field; ions flow “down it”

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68
Q

equilibrium potential

A

membrane potential at which there is no net diffusion of ions down concentration gradient; also called reversal potential

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69
Q

driving force

A

difference between the equilibrium potential and the actual voltage; tells us which way and how strongly ions will flow

Vdf=Vm-Eion

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70
Q

Nernst equation

A

formula for calculating the equilibrium potential (Eion) of each ion

Eion = (61.5mV/Z)*log[ion]outside/[ion]inside

Tricks:
-If the signs for charge (Z) and Eion align, [ion] is greater outside the cell
-For all positive ions, if [ion] is greater outside the cell, Eion will be positive
-For all negative ions, if [ion] is greater inside the cell, Eion will be negative

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71
Q

sodium-potassium pump

A

3 Na+ ions move outside the cell and 2 K+ ions move inside the cell; pumps ions against concentration gradient

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72
Q

What happens to Vm when you elevate [K+] outside the neuron?

A

Vm moves towards 0, as K+ inside the cell is less likely to leak due to changes in the concentration gradient

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73
Q

permeability

A

ease with which ions cross membrane; proportional to that of potassium (e.g., pk=1, pNa=0.05)

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74
Q

Goldman equation

A

membrane is at equilibrium between the reversal potentials of its permeable ions; ions that are more permeable (more pores/channels) bias the membrane potential more, which is why resting membrane potential is near EK+ (-65 mV)

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75
Q

feedback

A

when output is used as input; a system running with feedback is “closed loop,” while a system running without feedback is “open loop”

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76
Q

Where can synapses form?

A

along entire length of dendrite or axon

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77
Q

voltage-gated ion channels

A

open and close depending on voltage, establishing feedback systems; there is a linked ion pore and voltage sensor

78
Q

linked ion pore and voltage sensor

A

comprise voltage-gated ion channels; there is a positively charged transmembrane domain and 4 subunits join to form channel

Key: as voltage changes, so do the forces acting on the charged domain

79
Q

How does membrane potential influence voltage-gated channels?

A

1) Negative resting potential causes the charged side chains of the membrane to be pulled towards the inside of the cell
2) As membrane potential depolarizes, charged segment is released and the channel opens

80
Q

positive feedback from sodium flow

A

at rest, all Na+ voltage-gated channels are closed, but as Vm reaches threshold, Na+ channels open and action potential is initiated

81
Q

action potential threshold

A

if membrane potential doesn’t reach threshold at which Na+ channels open, there is no positive feedback, no action potential, and the membrane returns to rest; action potentials are all-or-nothing

if membrane does reach threshold, positive feedback from sodium flow occurs, resulting in explosive depolarization

82
Q

action potential

A

also called “spike,” “nerve impulse,” or “discharge,” the action potential is generated in the soma and travels down axon, lasting on order of 1ms, and drives communication across synapses

refers to a Vm theshold being reached, causing a flow of Na+ into the cell, resulting in rapid depolarization, followed by Na+ channel closure and K+ channels opening, repolarizing and hyperpolarizing the cell

83
Q

signal amplification of the action potential

A

myelin ensures current upstream produces a potent depolarization and the next node depolarizes strongly (increases voltage at next node)

helps transmit information down the long, thin axon; without large depolarization due to the action potential, depolarization in the soma would affect the distal axon minimally

84
Q

nodes of Ranvier

A

myelinating glia leave gaps in myelin where channels cluster; each node must push the next past action potential theshold in order for an action potential to propagate down an axon

85
Q

saltatory conduction

A

action potential jumping from node to node

86
Q

Why does the action potential of a neuron stop near +50mV?

A

1) AP involves massive increase in Na+ permeability; according to the Goldman equation, this high pNa will move Vm near ENa
2) Driving force; we use driving forcr to calculate how much current will flow, and therefore how much Vm will change when channels open; Na+ current takes Vm near ENa, so driving force (and sodium current) steadily diminishes

87
Q

driving force and current (AP)

A

large driving force means large current; small driving force means small current

88
Q

polarity

A

refers to the potential difference across the membrane, and depolarization reduces this potential difference

89
Q

voltage clamp

A

maintains the membrane potential at a set point, so can directly control whether voltage-gated channels are open or closed (via a patch); tool used to measure conductance (g)

90
Q

equation for measuring conductance

A

Iion = gion(Vm - Eion)

Note: can also used Ohm’s law equation and substitute 1/g in for R

91
Q

unitary conductance

A

how much flow a single molecule can generate; can be measured with voltage clamp patch

92
Q

measuring conductance with voltage clamp

A

as cell is more depolarized, Na+ conductance is greater (i.e., more sodium channels open); this is observable by holding the membrane potential constant

93
Q

Why doesn’t Vm stay at ENa when voltage-gated sodium channels open?

A

1) Sodium channels close themselves
2) Potassium channels help return to rest

94
Q

inactivation of voltage-gated Na+ channels

A

inactivation is different than channel being closed; rather, it is blocked by ball-and-chain of amino acids (causes refractory period)

95
Q

AP undershoot phase

A

part of action potential where the membrane is hyperpolarized due to the speed at which K+ channels close after repolarizing the cell

96
Q

delayed rectifier

A

refers to the opening of voltage-gated potassium channels to repolarize the cell; “delayed” because it opens after the voltage-gated sodium channels and “rectifier” because it preferentially passes outward current; negative feedback

97
Q

negative feedback from potassium flow

A

“delayed rectifier” voltage-gated potassium channels open in response to depolarization, causing hyperpolarization

98
Q

effect of stronger depolarizing input in action potentials

A

causes faster rate of firing and pushes Vm back to threshold quicker after each AP; i.e., AP firing rate increases as the depolarizing current increases

99
Q

local translation in axons

A

axons locally produce proteins needed at synapse and for metabolic support; local translation often necessary for survival

growth cones in developing axons use local translation

100
Q

tetrodotoxin

A

blocks Na+ channels; for defense

101
Q

alpha- and beta-toxins

A

shifts opening and closing of Na+ channels; to capture prey

102
Q

apamin

A

blocks K+ channels; for defense

103
Q

dendrotoxin

A

blocks K+ channels; for prey capture

104
Q

Can a single axon form synapses with multiple dendrites?

A

yes, multiple dendrites can form a postsynaptic terminal with a single axon serving as the presynaptic terminals

105
Q

vagus nerve

A

a cranial nerve connecting brainstem (vs. spinal cord) with head/body

106
Q

neuron doctrine “debunked”

A

neuron doctrine widely accepted until the discovery of the electrical synapse (gap junction), which is a portal connecting cytosol of two neurons that allows direct ion flow from one neuron to another

107
Q

Golgi belief about neurons

A

single structure (reticular)

108
Q

Cajal belief about neurons

A

connected but distinct cells

109
Q

chemical synapse

A

synapse that signals through release of chemical (neurotransmitter)

110
Q

What do chemical synapses release?

A

many neurotransmitters can be released, and vesicles reflect the size of what is being released in that larger molecules have “denser” vesicles

111
Q

active zone

A

source of NT release across the synapse (site where vesicles “fuse” with membrane and dump NT); located on presynaptic terminal

112
Q

How many types of neurotransmitter can be released by a single neuron?

A

more than one type can be released

113
Q

steps in chemical synaptic transmission

A

1) Neurotransmitter synthesis
2) Load neurotransmitter into synaptic vesicles
3) Vesicles fuse to presynaptic terminal
4) NT spills into synaptic cleft
5) NT binds to postsynaptic receptors
6) Electrical and/or biochemical response elicited in postsynaptic cell
7) Removal of neurotransmitter from synaptic cleft by transporter proteins/reuptake or simple diffuson

114
Q

three major types of neurotransmitters

A

1) amino acids
2) amines
3) neuropeptides

115
Q

amino acid neurotransmitters

A

small building blocks of proteins are co-opted; neurons that release amino acids have special proteins that load them into vesicles

ex. glutamate (excitatory synapses), GABA (inhibitory synapses), glycine

116
Q

monoamine neurotransmitters

A

small organic molecules; neurons that release monoamines have special enzymes to synthesize them

ex. dopamine (DA), acetylcholine (Ach), norepinephrine (NE), serotonin (5-HT), melatonin

117
Q

peptide neurotransmitters

A

small proteins that are typically loaded into oblong, dense-core vesicles; tend to act in a paracrine fashion (not just across synapses but diffusing to nearby cells)

ex. dynorphin, enkephalins, oxytocin, vasopressin, substance P

118
Q

noncanonical neurotransmitters

A

1) nitric oxide - gaseous, paracrine signal, released by postsynaptic neuron (retrograde NT) through membrane (no vesicles) in response to NT
2) anandamide - hydrocarbon chain (fatty acid) in the endocannabinoid (eCB) system, retrograde signal

119
Q

retrograde signal

A

NT transmission from postsynaptic neuron to presynaptic neuron; carried out by nitric oxide and anandamide

120
Q

amino acid neurotransmitter synthesis and storage

A

often packaged at the presynaptic terminal, where they are found (this makes vesicle loading efficient)

121
Q

monoamine neurotransmitter synthesis and storage

A

most can be synthesized from amino acids; often packaged at the presynaptic terminal, where amino acids are found (this makes vesicle loading efficient)

122
Q

neuropeptide neurotransmitter synthesis and storage

A

usually packaged early and then transported

123
Q

What is required to transform an action potential into NT movement from vesicles to synaptic cleft?

A

1) Calcium channels (AP to calcium)
2) Calcium-sensitive SNARE complex (calcium to vesicle fusion)

124
Q

calcium chelators

A

molecules that bind with metal ions; help remove calcium from interior of neuron by binding free calcium

125
Q

relationship between mitochondria and calcium

A

mitochondria accumulate calcium through pumps, removing it from the cytosol

126
Q

voltage-gated calcium channels

A

have pore-forming and voltage-sensing domains (like sodium channels), and depolarization causes them to open (i.e., if AP propogates down the axon to the synapse they open); they are part of the synapse (presynaptic terminal)

127
Q

calcium at the synapse (how NTs undergo exocytosis and are released)

A

1) Action potential arrives at axon terminal
2) Voltage-gated Ca2+ channels open and Ca2+ enters the axon terminal
3) Upon entry, Ca2+ activates synaptotagmin, causing SNARE proteins on vesicle and plasma membrane to drive fusion. Fusion of two lipid bilayers makes contents of vesicle free to leave presynaptic terminal (exocytosis)
4) NT diffuses across cleft and binds to ligand-gated ion channels on postsynaptic membrane

128
Q

synaptotagmin

A

a calcium sensor that is activated by Ca2+ entry into the presynaptic terminal, it causes SNARE proteins on vesicle and plasma membrane to drive fusion

129
Q

SNARE proteins

A

located on vesicles and the plasma membrane, they are activated by synaptotagmin to drive fusion

130
Q

Loewi

A

concluded neurons communicate with chemicals because a stimulated vagus nerve changed the surrounding solution

131
Q

GluSnFR

A

engineered protein (can be expressed through transgenesis - transfer of foreign DNA) that reveal NT (glutamate) by flourescing when binding; this allows us to visualize synapses at dendritic spines and is especially useful because individual synapses on the same dendrite are difficult to measure and distinguish

132
Q

in vivo

A

in live animal

133
Q

GluSnFR and ferret visual area

A

using GluSnFR, it was determined that individual synapses in ferret visual area have preferred visual motion and that neighboring spines have different visual preference

134
Q

in vitro

A

in culture dish

135
Q

ligand

A

any molecule that binds a receptor

136
Q

receptor specificity

A

receptors are specific for NTs; that is, a receptor can only bind one specific NT

137
Q

neurotransmitter specificity

A

neurotransmitters are not specific for receptors; that is, one NT can bind various receptors (i.e., divergence)

138
Q

two types of neurotransmitter receptor

A

1) ligand-gated ion channel (ionotropic)
2) metabotropic receptor (GPCR)

139
Q

To what type of receptor do amine/amino acid neurotransmitters bind?

A

both ionotropic or metabotropic

140
Q

To what type of receptor do peptide neurotransmitters bind?

A

mostly metabotropic (GCPR)

141
Q

ionotropic receptor structure

A

usually 5 subunits (pentamer) and each subunit can be coded by a different gene (heteromeric), so subunits can be mixed and matched, creating channel diversity

142
Q

ionotropic receptor conformation change

A

instead of having a voltage-gate, when a receptor binds, the shape changes and pore opens

143
Q

postsynaptic current

A

caused by ionotropic receptors; a synapse can be either excitatory or inhibitory depending on action

144
Q

postsynaptic potential (PSP)

A

can be either excitatory (EPSP) or inhibitory (IPSP); PSP changes in postsynaptic cell as a response to NT binding to an ionotropic receptor

145
Q

excitatory postsynaptic potential (EPSP)

A

occurs when channels open and positively charged ions enter the cell (depolarization)

146
Q

inhibitory postsynaptic potential (IPSP)

A

occurs when channels open and negatively charged ions (Cl-) enter the cell (hyperpolarization)

147
Q

electrical synapses

A

called the gap junction, at which no NTs are needed and ions simply cross - they can move in both directions; can cause fast voltage changes postsynaptically (like chemical synapses) and help synchronize spiking across cells

148
Q

connexon

A

channel at electrical synapse; formed by six connexins

149
Q

electric coupling

A

cells that form a gap junction are said to be “electrically coupled”

150
Q

What happens when you lose gap junctions?

A

lose synchronization of these neurons in the brain stem

151
Q

metabotropic receptors

A

NT binds receptor, Galpha subunit detaches from trimer and moves to enzyme or channel or activate second messenger cascade (cAMP or IP3/DAG)

152
Q

ligand-gated ion channels vs. GPCRs

A

ligand gated ion channels are faster, but have shorter action than GPCRs

153
Q

GPCR structure

A

part of a 7 transmembrane domain superfamily and are coded by one gene

154
Q

orphan GPCR

A

a GCPR with no known ligand

155
Q

G-protein signaling mechanism

A

1) G-protein bumps into activated receptor and exchanges GDP for GTP
2) Binding of GTP releases Galpha subunit, which can be either stimulatory or inhibitory, and it influences effector proteins or triggers second messenger cascade
3) Galpha inactivates by slowly converting GTP to GDP
4) Galpha and Gbetagamma recombine to start cycle again

156
Q

Galpha signaling cascade

A

1) Galpha activates adenylyl cyclase (AC) which converts ATP to cAMP
2) cAMP activates PKA, a kinase that phosphorylates CREB, which binds DNA to alter gene expression
3) If Galpha is stimulatory, phosphorylation causes closing of K+ channels. If Galpha is inhibitory, no phosphorylation occurs and K+ channels open

157
Q

GPCR amplification

A

idea that 1 activated G-protein can bind hundreds of NTs and consequently activate many cAMP molecules that have profound effects on the cell (gene expression)

158
Q

signaling cascade convergence

A

idea that different G-proteins stimulate or inhibit AC, resulting in a push-pull method

159
Q

Why is neurotransmitter receptor location important?

A

it is key to its function

160
Q

autoreceptors

A

located in presynaptic terminal, receive the NT released from the same neuron; provides the neuron feedback and is often used for negative feedback tht can function as a safety valve (common effect of activating autoreceptors is inhibition of neurotransmitter release)

161
Q

extrasynaptic receptors

A

receptors on postsynaptic neuron that sit on membrane outside of synapse; detect spillover, when transmitter becomes so concentrated that it has to escape synapse

ex. NMDA, which allows Ca2+ to flow in, triggers death cascades on some cells

162
Q

How can NMDA receptors (metabotropic) on one cell promote survival and on others cell death?

A

response depends on molecules nearby; different signaling pathways by virtue of different second messenger systmes

163
Q

multiple receptors for single NT

A

ACh has different structures of receptors, such as nicotinic receptor (ionotropic) and muscarinic receptor (metabotropic); both receptors bind ACh, but not all ligands are shared, meaning different effects are produced

164
Q

receptor agonists

A

mimic actions of naturally occurring neurotransmitters; receptors are often named for agonist

165
Q

receptor antagonists

A

block actions of naturally occurring neurotransmitters

166
Q

synaptic integration

A

-process by which multiple synaptic potentials combine within one postsynaptic neuron
-most neurons in the brain and spinal cord receive thousands of synaptic inputs
-how neurons perform synaptic integration informs their computation

167
Q

spatial summation

A

synchronous depolarization (when EPSP); looks like singular “powerful” spike when summated as EPSP or below threshold bumps when summation as EPSP and IPSP

168
Q

temporal summation

A

rapid spikes in succession; looks like bumpy spikes when summated

169
Q

axon potential propagation in dendrites

A

just as the AP amplifies depolarization to help signal down axon, dendrites amplify depolarization to help it reach the soma and AIS; they do so via compartmentalization

170
Q

compartmentalization

A

dendrites can compartmentalize synaptic inputs, allowing them to amplify PSPs to help them reach the soma

ex. helps amacrine cells encode spatial visual information

171
Q

neural coding

A

idea that neurons represent information through their electrical activity

172
Q

spike rate

A

rate of action potential firing; increased by stronger depolarizing current

more spikes means more signaling (more NT release), which means more receptor binding and more EPSPs

173
Q

rate code

A

information represented by the rate or frequency of action potentials of a neuron

174
Q

temporal code

A

information represented by the precise timing of action potentials of a neuron

ex. retinal ganglion cells and the ability to use neuronal activity to recreate image an organism sees

175
Q

What influences the rate and timing of action potentials?

A

1) Synaptic input and integration (summation)
2) Neuron state (e.g., history of second messenger signals, such as how much cAMP)
3) Electrical properties specific to the neuron (intrinsic properties; “electrical fingerprint”)

176
Q

non-spiking starburst amacrine cell

A

as they develop, they lose their voltage-gated sodium channels and stop firing action potentials; spikes might impair function by linking dendritic compartments

177
Q

relationship between ion channels and neuronal activity profiles

A

a neuron’s particular response is defined by the complement of ion channels in its membrane; these unique intrinsic properties allow neurons to specialize

178
Q

three neuronal activity profiles

A

1) transient - lasting for a short time
2) sustained - sustained spike; neurons that sustain activity allow brief events to trigger prolonged effects (compliment metabotropic signaling)
3) rhythmic - patterned spikes; neurons that are rhythmically active can keep time or “pace” (pacemakers)

179
Q

sodium channels and temporal spike profile

A

inactivation (via ball-and-chain) creates refractory period that sets limit on spike rate; activation creates relative refractory period that further shapes spike rate

i.e., switching between active/inactive establishes a rhythm

180
Q

In what ways do differences in ionic currents arise from differences in ion channel?

A

1) Selectivity (potassium, sodium, calcium, chloride)
2) Gating - circumstances that cause the pore to open and close
3) Kinetics - the speed of opening and closing

181
Q

ion channel superfamily

A

ion channels with different gating (i.e., what ions they pass) are organized in families

182
Q

Kv channel differences

A

different Kv channels within the superfamily activate very differently and have differing kinetics; some are fast and sustained, some are fast and transient, and others are slow; many also require additional depolariation to obtain the same effect

183
Q

transient neurons

A

spike that lasts for a short time; underlying proteins are transitory excitatory channels and highly responsive inhibitory channels

again, the ultimate idea here is that ion channels can greatly influence the neuronal profile, allowing neurons to specialize

184
Q

sustained neurons

A

spike that is sustained and complimentary to metabotropic receptors; underlying proteins are sustained excitatory channels and a lack of inhibitory channels

again, the ultimate idea here is that ion channels can greatly influence the neuronal profile, allowing neurons to specialize

185
Q

spike train

A

cycles of calcium, sodium, and potassium channel activation; opening and closing of channels modifies rhytmic activity (this is how pacemakers work)

186
Q

T-type calcium channels

A

drive burst-firing (rapidly repeating action potentials)

187
Q

calcium-activated potassium channels (KCa)

A

potassium channels activated in response to calcium channels; calcium binds to binding site on KCa channels, prompting K+ to leave the cell and hyperpolarize it; common in burst-firing

188
Q

neuronal pacemaking

A

-is important for rhythmic movement
-can be generated by intrinsic properties
-involves cycles of spiking

189
Q

receptor autoradiography

A

deposit of radioactive isotopes at receptors to identify the location of a receptor; relies on a radioligand that binds to the receptor

190
Q

radioligand

A

a ligand that is radiolabeled; allow us to visualize where NT receptors are available in vitro and in vivo

191
Q

autoradiography vs. immunohistochemistry

A

in IHC, antibodies can be generated that recognize antigen on NT receptors, but antibodies don’t reveal capacity to bind ligand

radioligands are also applicable for labeling in vivo

192
Q

PET scan

A

injection of radioactive glucose allows measurement of deposition of radioactive glucose, which is higher in tumors and epileptic foci

Neurobiology 523 (3 decks)

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