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PSYCH 275 > Chapter 5: Communication and Adaptation of Neurons > Flashcards

Chapter 5: Communication and Adaptation of Neurons Flashcards

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1
Q

Acetylcholine (ACh)

A

first neurotransmitter discovered in the PNS and CNS, activates skeletal muscles in the SNS, either excites or inhibits organs in the ANS

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2
Q

Epinephrine (EP)

A

chemical messenger that acts as a neurotransmitter in the CNS and as a hormone to mobilize the body for flight or fight during times of stress, also known as adrenaline

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3
Q

Norepinephrine (NE)

A

neurotransmitter that accelerates heart rate in mammals, found in the brain and in the sympathic division of the ANS, also known as noradrenaline

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4
Q

Neurotransmitters

A

chemical with an excitatory or inhibitory effect when released by a neuron onto a target

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5
Q

Dopamine (DA)

A

amine neurotransmitter involved in coordinating movement, attention, learning, and reinforcing behaviors

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6
Q

Synaptic Vesicles

A

membranous compartment that encloses a fixed number (called a quantum) or neurotransmitter molecules

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7
Q

Synaptic Cleft

A

gap separating the neuronal presynaptic membrane from the postsynaptic membrane

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8
Q

Tripartite Synapse

A

functional integration and physical proximity of the presynaptic membrane, postsynaptic membrane, and their intimate association with surrounding astrocytes

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9
Q

Chemical Synapse

A

junction at which messenger molecules are released when stimulated by an action potential

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10
Q

Presynaptic Membrane

A

axon terminal membrane on the transmitter, or output, side of a synapse

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11
Q

Postsynaptic Membrane

A

membrane on the transmitter, or input, side of a synapse

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12
Q

Storage Granule

A

membranous compartment that holds several vesicles containing a neurotransmitter

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13
Q

Anterograde Synaptic Transmission

A

process that occurs when a neurotransmitter is released from a presynaptic neuron and binds to a receptor on the postsynaptic neuron

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14
Q

What are the five steps of neurotransmission?

A
  1. The neurotransmitter is synthesized somewhere inside the neuron
  2. It is packaged and stored with vesicles at the axon terminal
  3. It is transported to the presynaptic membrane and released into the cleft in response to an action potential
  4. It binds to and activates receptors on the postsynaptic membrane
  5. It is degraded or removed, so it will not continue to interact with a receptor and work indefinitely
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15
Q

Transporter

A

protein molecule that pumps substances across a membrane

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16
Q

Transmitter-Activated Receptor

A

protein that has a binding site for a specific neurotransmitter and is embedded in the membrane of a cell

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17
Q

Ionotropic Receptor

A

embedded membrane protein, acts as a binding site for a neurotransmitter and a pore that regulates ion flow to directly and rapidly change membrane voltage

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18
Q

Metabotropic Receptor

A

embedded membrane protein with a binding site for a neurotransmitter linked to a G protein, can affect other receptors or act with second messengers to affect other cellular processes, including opening a pore

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19
Q

Autoreceptor

A

self-receptor in a neuronal membrane, that is, it responds to the same transmitter released by the neuron, part of a negative feedback loop allowing the neuron to adjust its output

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20
Q

Quantum

A

number of neurotransmitter molecules, equivalent to the content of a single synaptic vesicle, that produces a just-observable change in postsynaptic electric potential

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21
Q

Gap Junction

A

area of contact between adjacent cells in which connexin proteins in each cell form connecting hemichannels which, when open, allow ions to pass between the two cells, also called an electrical synapse

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22
Q

What are the four criteria for identifying neurotransmitters?

A
  1. The transmitter must be synthesized in the neuron or otherwise be present in it
  2. When neuron is active, the transmitter must be released and produce a response to some target
  3. The same response must be obtained when the transmitter is experimentally placed on the target
  4. A mechanism must exist for removing the transmitter from its site of action after its work is done
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23
Q

Reuptake

A

inactivation of a neurotransmitter when membrane transporter proteins bring the transmitter back into the presynaptic axon terminal for reuse

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24
Q

Small-Molecule Transmitter

A

quick-acting neurotransmitter synthesized in the axon terminal from products derived from the diet

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25
Q

Rate-Limiting Factor

A

any chemical in limited supply that restricts the pace at which another chemical can be synthesized

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26
Q

Serotonin (5-HT)

A

amine neurotransmitter, helps to regulate mood and aggression, appetite and arousal, perception of pain and respiration

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27
Q

Gamma-Aminobutyric Acid (GABA)

A

amino acid neurotransmitter, typically inhibits neurons

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28
Q

Histamine (H)

A

neurotransmitter that controls arousal and waking, can cause the constriction of smooth muscles, when activated in allergic reactions, constricts airway and contributes of asthma

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29
Q

Neuropeptide

A

short, multifunctional amino acid chain (fewer than 100 amino acids)

acts as a neurotransmitter and can act as a hormone, may contribute to learning

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30
Q

Endocannabinoid

A

class of lipid neurotransmitters, including anandamide and 2-AG

synthesized at the presynaptic membrane to act on receptors at the presynaptic membrane

affects appetite, pain, sleep, mood, memory, anxiety, and the stress response

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31
Q

Nitric Oxide (NO)

A

gaseous neurotransmitter, acts for example, to dilate blood vessels, aid digestion, and activate cellular metabolism

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32
Q

Carbon Monoxide (CO)

A

gaseous neurotransmitter, activates cellular respiration

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33
Q

Hydrogen Sulfide

A

gaseous neurotransmitter, slows cellular metabolism

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34
Q

Zinc

A

an ion transmitter that is packaged and stored in vesicles and that is then released and interacts with several receptors

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35
Q

G protein

A

guanylyl nucleotide-binding proteins coupled to a metabotropic receptor, when activated binds to other proteins

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36
Q

Subunit

A

protein molecule that assembles with other protein molecules

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37
Q

Second Messenger

A

chemical that initiates a biochemical process when activated by a neurotransmitter (the first messenger)

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38
Q

How were chemical messages discovered?

A

discoveries about how neurons communicate stem from experiments designed to study what controls an animals heartbeat

heartbeat quickens if you are excited or exercising, if you are resting, it slows

chemical relay excitatory messages to speed up and inhibitory messages to slow down

role of the vagus nerve and neurotransmitter acetylcholine (ACh) in slowing heart rate

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38
Q

How were chemical messages discovered?

A

discoveries about how neurons communicate stem from experiments designed to study what controls an animals heartbeat

heartbeat quickens if you are excited or exercising, if you are resting, it slows

chemical relay excitatory messages to speed up and inhibitory messages to slow down

role of the vagus nerve and neurotransmitter acetylcholine (ACh) in slowing heart rate

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39
Q

Who was Otto Loewi (1921)?

A

frog heart experiment

marked the beginning of research into how chemicals carry info from one neuron to another

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40
Q

What did Otto Loewi discover about acetylcholine?

A

the first neurotransmitter discovered in the PNS and CNS

activates skeletal muscles in the somatic NS

excitatory/inhibitory action dependent upon the ion channel (not the molecule itself)

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41
Q

What did Otto Loewi discover about epinephrine?

A

chemical messenger that acts as a hormone

mobilize the body for fight or flight during stress

works as a neurotransmitter in the CNS

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42
Q

What did Loewi discover about norepinephrine?

A

neurotransmitter found in the brain and in the sympathetic division of the autonomic NS

accelerates heart rate in mammals

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43
Q

What is a neurotransmitter?

A

chemical released by a neuron onto a target (excitatory or inhibitory)

outside the CNS, many of these chemicals circulate in the bloodstream as hormones (have distinct targets, action slower than that of a neurotransmitter)

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44
Q

How are neurotransmitters measured today?

A

the actual number of transmitters is an open question, with 100 posited as the maximum

the confirmed number is 60, with most of the work being done by 10

whether a chemical is accepted as a neurotransmitter depends on the extent to which it meet certain criteria

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45
Q

What is an electron microscope?

A

projects a beam of electrons through a very thin slice of tissue

much better resolution than the light microscope

1950s: revealed the structure of a synapse for the first time

allowed researchers to determine that neurotransmitters are packaged into vesicles at the end terminals of axons

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46
Q

What is a chemical synapse?

A

the junction where messenger molecules (neurotransmitters) are released from one neuron to excite or inhibit the next neuron

most synapses in the mammalian nervous system are chemical

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47
Q

What is the presynaptic membrane?

A

axon terminal

where the action potential terminates to release the chemical message

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48
Q

What is the postsynaptic membrane?

A

dendritic spine

the receiving side of the chemical message, where EPSPs or IPSPs are generated

49
Q

What is the synaptic cleft?

A

space between

small gap where the chemical travels from presynaptic to postsynaptic membrane

50
Q

What is the tripartite synapse?

A

functional integration and physical proximity of the presynaptic membrane, postsynaptic membrane, and their intimate association with surrounding astrocytes

51
Q

What is the synaptic vesicle?

A

presynaptic

small membrane-bound spheres that contain one or more neurotransmitters

52
Q

What is the postsynaptic receptor?

A

postsynaptic

site to which a neurotransmitter molecule binds

53
Q

What are the two ways neurotransmitters are derived?

A

synthesized in the axon terminal (small molecule transmitter)

synthesized in the cell body (peptide transmitters)

54
Q

How are neurotransmitters synthesized in the axon terminal?

A

made from building block from food

pumped into cell via transporters

protein molecules embedded in the cell membrane, pumps substances across a membrane

55
Q

How are neurotransmitters synthesized in the cell body?

A

according to instructions in the DNA (peptide transmitters)

transported on microtubules to axon terminal

peptide transmitters may also be manufactured within presynaptic terminal by the ribosomes

56
Q

How are neurotransmitters packaged?

A

regardless of their origin, neurotransmitters that are packaged into vesicles can be found in three locations at the axon terminal

some vesicles are warehoused in granules

some are attached to microfilaments

others are attached to the presynaptic membrane

57
Q

How are neurotransmitters released into the synaptic cleft?

A

synaptic vesicles loaded with neurotransmitters must dock near release sites on the presynaptic membrane

then the vesicles are primed to prepare them to fuse rapidly in response to calcium (Ca) influx

at the terminal, the action potential opens voltage-sensitive calcium channels

Ca2+ enters the terminal and binds to the protein

the complex causes some vesicles to empty their contents into the synapse

58
Q

What is receptor-site activation?

A

after release, the neurotransmitter diffuses across the synaptic cleft to activate receptors on the postsynaptic membrane

properties of the receptor determine the effect on the postsynaptic cell

59
Q

What are transmitter-activated receptors?

A

protein embedded in the membrane of a cell that has a binding site for a specific neurotransmitter

60
Q

What effects can a neurotransmitter have on the postsynaptic cell?

A

depolarize the postsynaptic membrane, causing excitatory action on the postsynaptic neuron (EPSP)

hyperpolarize the postsynaptic membrane, causing inhibitory action on the postsynaptic neuron (IPSP)

initiate other chemical reactions that modulate the excitatory or the inhibitory effect or influence other functions of the receiving neuron

61
Q

How does diffusion inactivate neurotransmitters?

A

some of the neurotransmitter simply diffuses away from the synaptic cleft and is no longer available to bind to receptors

62
Q

How does degradation inactivate neurotransmitters?

A

enzymes in the synaptic cleft break down the neurotransmitter

63
Q

How does reuptake inactivate neurotransmitters?

A

transmitter is brought back into the presynaptic axon terminal by membrane transporters for reuse

by-products of degradation by enzymes also may be taken back into the terminal to be used again

64
Q

How does astrocyte uptake inactivate neurotransmitter?

A

nearby astrocytes take up neurotransmitter, can also store transmitters for re-export to the axon terminal

65
Q

What is flexibility in synaptic function?

A

if the terminal is very active, the amount of neurotransmitter made and stored there increases

if the terminal is not often used, enzymes within the terminal buttons may breakdown excess transmitter

the by-products are then reused or excreted from the neuron

axon terminals may even send messages to the neuron’s cell body, requesting increased supplies of the neurotransmitter or the molecules with which to make it

66
Q

What is the variety of synapses?

A

synapses vary widely

each type is specialized in location, structure, function, and target

variety of connections makes the synapse a versatile chemical delivery system

67
Q

What are electrical synapses?

A

gap junction: fused presynaptic and postsynaptic membrane that allows an action potential to pass directly from one neuron to the next

electrical synapses are fast, gap junctions eliminate delays in information flow

67
Q

What are electrical synapses?

A

gap junction: fused presynaptic and postsynaptic membrane that allows an action potential to pass directly from one neuron to the next

electrical synapses are fast, gap junctions eliminate delays in information flow

chemical synapses are more flexible (amplify or diminish signal) but slower

68
Q

What are excitatory synapses?

A

typically located on dendrites
round vesicles
dense material on membranes
wide cleft
large active zone

69
Q

What are inhibitory synapses?

A

typically located on cell body
flat vesicles
sparse material on membranes
narrow cleft
small active zone

70
Q

What is the relationship between excitatory and inhibitory action within a neuron?

A

the differing locations of excitatory and inhibitory synapses divide a neuron into two zones: an excitatory dendritic tree and an inhibitory cell body

excitation coming in over the dendrites and spreading past the axon hillock to trigger an action potential at the initial segment

if the message is to be stopped, it is vest stopped by inhibiting the cell body close to the initial segment

so inhibition blocks or cuts excitation from passing through the postsynaptic cell

71
Q

What are some functions of neurotransmitters?

A

carry a message from one neuron to another by influencing the voltage on the postsynaptic membrane

change the structure of a synapse

communicate by sending messages in the opposite direction, these retrograde (reverse-direction) messages influences the release or reuptake of transmitters on the presynaptic side

72
Q

What are small-molecule transmitters?

A

class of quick acting neurotransmitters

synthesized from dietary nutrients and packaged ready for use in axon terminals

can be quickly replaced at presynaptic terminal

some drugs are designed to emulate the router of small-molecule transmitters

73
Q

What is acetylcholine (ACh)?

A

present at junction of neurons and muscles in the CSN

74
Q

What are some examples of amines?

A

common biochemical pathway/relatedness

dopamine, norepinephrine, epinephrine, serotonin

75
Q

What are amino acids?

A

glutamate: main excitatory

GABA: main inhibitory transmitter (workhorses of the brain)

76
Q

What are purines?

A

synthesized as nucleotides, regulate blood flow, sleep, arousal, etc.

77
Q

What are neuropeptides?

A

short, multifunctional amino acid chain, acts as a neurotransmitter and can act as a hormone

synthesized through translation of mRNA from instructions in the neuron’s DNA

most are assembled on the neuron’s ribosomes, packaged in a membrane by Golgi bodies, and transported by the microtubules to the axon terminals

act slowly and are not replaced quickly

have no direct effects on postsynaptic membrane voltage

activate receptors that indirectly influence cell structure/function

generally, cannot be taken orally as drugs, as small-molecule transmitters can

78
Q

What are the function of neuropeptides in the NS?

A

act as hormones that respond to stress

enable a mother to bond with her infant (oxytocin)

regulate eating and drinking/pleasure and pain

79
Q

What are lipid transmitters?

A

can’t be stored in vesicles, created “on demand”

main example: endocannabinoids (endogenous cannabinoids), synthesized at the postsynaptic membrane to act on receptors at the presynaptic membrane, postsynaptic neurons reduces amount of incoming neural signal

affect appetite, pain, sleep, mood, memory, anxiety, stress response

80
Q

What are endocannabinoids?

A

investigators hypothesize that endocannabinoids are synthesized on demand after a neuron has depolarized and calcium has entered

acts on presynaptic receptor

reduces the amount of small-molecule transmitter being released, so the postsynaptic neuron reduces the amount if incoming neural signal

CBI receptor is the target of all cannabinoids, endocannabinoids (humans) or phytocannabinoid (plants) or synthetic cannabinoids

found in both glutamate and GABA synapses, cannabinoids act as neuromodulators to inhibit release of glutamate and GABA, cannabinoids thus dampen both neuronal excitation and inhibition

obtained from the hemp plants Cannabis Sativa and Cannabis Indica

used for medical and recreational purposes for thousands of years

81
Q

What are gaseous transmitters?

A

nitric oxide, carbon monoxide, hydrogen sulfide

neither stored in synaptic nor released from them

synthesized in cell as needed; easily cross cell membrane

chemical messengers in body, modulate neurotransmitter production

82
Q

What are ion transmitters?

A

recent evidence has led researchers to classify zinc as a transmitter

actively transported, packaged into vesicles, usually with another transmitter like glutamate, and released into the synaptic cleft

zinc dysregulation is linked to Alzheimer’s

83
Q

What are ionotropic receptors?

A

embedded membrane protein with two parts: a binding site for a neurotransmitter and a pore that regulates ion flow to directly and rapidly change membrane voltage

allows the movement of ions such as Na+, K+, and Ca+ across a membrane

when neurotransmitter attaches to binding site, the pore opens or closes, changing the flow of ions

84
Q

What are metabotropic receptors?

A

embedded membrane protein with a binding site for a neurotransmitter but no pore

indirectly produces change in nearby ion channels or in the cell’s metabolic activity

linked to a G protein that can affect other receptors or act with second messengers to affect other cellular processes

85
Q

What is the amplification cascade?

A

a single neurotransmitter binding to a metabolic receptor can activate an escalating sequence of events

proteins can be activated or deactivated

86
Q

Cholinergic Neuron

A

neuron that uses acetylcholine as its main neurotransmitter, cholinergic applies to any neuron that uses ACh as its main transmitter

87
Q

Activating System

A

neural pathways that coordinate brain activity through a single transmitter

its cell bodies lie in a brainstem nucleus

axons are distributed through a wide CNS region

88
Q

Schizophrenia

A

behavioral disorder characterized by delusions, hallucinations, disorganized speech, blunted emotions, agitation or immobility, and a host of associated symptoms

89
Q

Noradrenergic Neuron

A

a neuron containing norepinephrine

90
Q

Major Depression

A

mood disorder characterized by prolonged feelings of worthlessness and guilt, disruption of normal eating habits, insomnia, a general slowing of behavior, and frequent thoughts of suicide

91
Q

Mania

A

disordered mental state of extreme excitement

92
Q

Obsessive-Compulsive Disorder

A

behavior characterized by compulsively repeated acts (such as hand washing) and repetitive, often unpleasant thoughts (obsessions)

93
Q

Learning

A

relatively persistent or even permanent change in behavior that results from experience

94
Q

Habituation

A

learned behavior in which the response to a stimulus weakens with repeated presentations

95
Q

Saccades

A

small, fast, random eye movements designed to keep photoreceptors exposed to ever-changing visual stimuli to prevent habituation

96
Q

Sensitization

A

learned behavior in which the response to a stimulus strengthens with learned presentations

97
Q

Posttraumatic Stress Disorder (PTSD)

A

syndrome characterized by psychological arousal associated with recurrent memories and dreams arising from a traumatic event that occurred months or years earlier

98
Q

What are receptor subtypes?

A

each neurotransmitter may interact with a number of receptor subtypes specific to that neurotransmitter

each subtype has slightly different properties, which confer different activities

99
Q

What are neurotransmitter systems and behavior?

A

a single neuron may use one transmitter at one synapse and a different transmitter at another synapse

different transmitters may coexist in the same terminal or synapse

caution against the assumption of a simple cause-and-effect relationship between a neurotransmitter and a behavior

100
Q

What is neurotransmission in the somatic nervous system (SNS)?

A

cholinergic neuron (motor neurons): neuron that uses acetylcholine as its main transmitter, excites skeletal muscles to cause contractions

nicotinic ACh receptor (nAChr): when Ach or nicotine binds to this receptor, its pore opens to permit ion flow, thus depolarizing the muscle fiber

the nicotine receptor pore permits the simultaneous efflux of K+ and influx of Na+

101
Q

What are the dual activating systems of the autonomic nervous system (ANS)?

A

the sympathetic division arouses the body for action, producing the fight-or-flight response, heart rate ramps up, digestive functions ramp down

the parasympathetic division calms the body down, producing an essentially opposite rest-and-digest response, digestive functions ramp up, heart rate ramps down

both divisions are controlled by acetylcholine neurons that emanate from the CNS at two levels of the spinal cord

102
Q

What is the function of cholinergic neurons in the CNS?

A

cholinergic neurons in the CNS synapse with sympathetic NE neurons to prepare the body’s organs for fight or flight

cholinergic neurons in the CNS synapse with autonomic ACh neurons in the parasympathetic division to prepare the body’s organs to rest and digest

103
Q

What are excitatory and inhibitory synapses?

A

during sympathetic arousal, norepinephrine turns up heart rate and turns down digestive functions, NE receptors on the heart are excitatory, whereas NE receptors on the gut are inhibitory

acetylcholine turns down heart rate and turns up digestive functions because its receptors on these organs are reversed, on the heart is inhibitory, on the gut is excitatory

104
Q

What is enteric nervous system (ENS) autonomy?

A

ENS can act without input from the CNS

uses al four classes of neurotransmitters, more than 30 transmitters, mainly serotonin and dopamine

sensory ENS neurons detect mechanical and chemical conditions in the gastrointestinal system

105
Q

What are activating systems?

A

neuronal pathway that coordinate brain activity through a single neurotransmitter

cell bodies lie in a nucleus in the brainstem, and their axons are distributed through a wide region of the brain

four systems: cholinergic, dopaminergic, noradrenergic, and serotonergic

one system for each small-molecule transmitter

106
Q

What is the cholinergic system?

A

normal waking behavior, is thought to function in attention and memory

loss of cholinergic neurons is associated with Alzheimer disease

107
Q

What is the dopaminergic system?

A

nigrostriatal pathways and mesolimbic pathways

108
Q

What are the nigrostriatal pathways in the dopaminergic system?

A

active in maintaining normal motor behavior (coordination)

loss of DA is related to muscle rigidity and dyskinesia in Parkinson disease

109
Q

What are the mesolimbic pathways in the dopaminergic system?

A

dopamine release causes repetition of behaviors

most affected in addiction behaviors (food, drugs, etc.)

related to impulse control

increases in DA activity may be related to schizophrenia

decreases in DA activity may be related to deficits of attention

110
Q

What is the noradrenergic system?

A

norepinephrine plays a role in learning by stimulating neurons to change structure

may also facilitate normal development of the brain and organize movements

imbalances associated with depression, mania

decreased NE activity related to ADHD and hyperactivity

111
Q

What is the serotonergic system?

A

plays a role in wakefulness and learning

imbalances associated with depression, schizophrenia, OCD, sleep apnea, sudden infant death syndrome (SIDS)

112
Q

What is the adaptive role of synapses in learning and memory?

A

learning: relatively permanent change in behavior that results from experience

neuroplasticity: the nervous system’s potential for change, which enhances its ability to adapt, required for learning and memory

hebb synapse: when the axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such as A’s efficiency, as one of the cells firing B is increased

cells that fire together, wire together

113
Q

Who is Eric Kandel?

A

was awarded the 2000 Nobel Prize in Physiology or Medicine for his descriptions of the synaptic basis of learning using Aplysia

he used enduring changes in simple defensive behaviors to study underlying changes in the nervous system

114
Q

What is the habituation response?

A

learning behavior in which a response to a stimulus weakens with repeated presentations of the stimulus

example: gill withdrawal response in the marine snail Aplysia californica

115
Q

What is the neural basis of habituation?

A

as habituation develops, the excitatory postsynaptic potentials in the motor neuron become smaller (motor neuron is receiving less neurotransmitter from the sensory neuron across the synapse)

habituation must take place in the axon terminal of the sensory neuron

less activity from a habituated neuron relative to a non-habituated ones (as habituation takes place, calcium influx decreases in response to voltage changes associated with an action potential)

reduced sensitivity of calcium channels and decreased release of neurotransmitter

116
Q

What is the sensitization response?

A

learning behavior in which the response to stimulus strengthens with repeated presentations because the stimulus is novel or stronger than normal

117
Q

What is the neural basis of sensitization?

A

in response to an action potential on an axon of a sensory neuron, K+ channels are slow to open (K+ ions cannot repolarize the membrane quickly, so action potential lasts longer than normal, prolongs the inflow of calcium and more transmitter is released)

sensitization is the opposite of habituation at the molecular and behavioral levels

in sensitization, more calcium influx results in more transmitter being released

in habituation, less calcium influx results in less neurotransmitter being released

118
Q

What is learning as a change in synapse number?

A

neural changes associated with learning must last long enough to account for a relatively permanent change in an organism’s behavior

repeated stimulation produces habituation and sensitization that can persist for months

the number and size of sensory synapses change in well-trained, habituated, and sensitized Aplysia

transcription and translation of nuclear DNA initiate structural changes (formation of new synapses and spines)

second-messenger cAMP molecules plays an important role in carrying instructions regarding structural changes to nuclear DNA

PSYCH 275 (11 decks)

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