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Psych 275 > Chapter 5: How Do Neurons Communicate and Adapt > Flashcards

Chapter 5: How Do Neurons Communicate and Adapt Flashcards

1
Q

How do neurons communicate and adapt?

A

-Chemical message
-Varieties of neurotransmitters and receptors
-Neurotransmitter systems and behavior
-Adaptive role of synapses in learning and memory

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2
Q

Otto Loewi

A

-Frog heart experiment
-Role of the vagus nerve and neurotransmitter acetylcholine (ACh) in showing heart rate
-Epinephrine (EP)
-Norepinephrine (NE)

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3
Q

Acetylcholine

A

-First neurotransmitter discovered in PNS and CNS; activates skeletal muscles in the somatic nervous system and may excite or inhibit internal organs in the automatic nervous system

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4
Q

Neurotransmitter

A

-Chemical released by a neuron onto a target with an excitatory or inhibitory effect
-Outside the CNS, many of these chemicals circulate in the bloodstream as hormones (distinct targets, slower than neurotransmitter)

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5
Q

Presynaptic membrane (axon terminal)

A

-Where the action potential terminates to release the chemical message

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6
Q

Postsynaptic membrane (dendritic spine)

A

-The receiving side of the chemical message where EPSP’s or IPSP’s are generated

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7
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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8
Q

Synaptic vessicle

A

-Presynaptic
-Small membrane-bound spheres that contain one or more neurotransmitters

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9
Q

Storage granule

A

-Presynaptic
-Membranous compartment that holds several vesicles containing neurotransmitters

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10
Q

Anterograde synaptic transmission

A

-Process that occurs when the neurotransmitter is released from a presynaptic neuron and binds to a receptor in the post-synaptic neuron
-5 step process of transmitting information across a chemical synapse from pre to post synaptic neuron

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11
Q

1)

A

The neurotransmitter is synthesized somewhere inside the neuron

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12
Q

2)

A

It is packaged and stored within vesicles at the axon terminal

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13
Q

3)

A

It is transported to the presynaptic membrane and released into the cleft in response to an action potential

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14
Q

4)

A

It binds to and activates receptors on the postsynaptic membrane

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15
Q

5)

A

-It is degraded or removed
-Not continue to interact with receptor and work indefinitely

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16
Q

How are neurotransmitters derived

A

1) Synthesized in axon terminal: Building blocks from food are pumped into cell via transporters, protein molecules are embedded in the cell membrane
2) Synthesized in cell body: According to DNA instructions (peptide transmitters) Transported on microtubules to axon terminal

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17
Q

Neurotransmitter release (step 3)

A

-At the terminal the action potential opens voltage-sensitive calcium (Ca2+) channels
-Ca2+ enters the terminal and binds to the protein calmodulin forming a complex
-The complex causes some vesicles to empty their contents into the synapse and others to get ready to empty their contents

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18
Q

Receptor-site activation (step 4)

A

-After release the neurotransmitter diffuses across the synaptic cleft to activate receptors on the postsynaptic membrane

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19
Q

Transmitter activated receptors

A

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

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20
Q

Postsynaptic side (step 4)

A

the neurotransmitter may
1) Depolarize the postsynaptic membrane causing EPSP
2) Hyperpolarize the postsynaptic membrane causing IPSP
3) Initiate other chemicals reactions that modulate the excitatory or inhibitory effect of influence other functions of the receiving norm

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21
Q

Autoreceptor

A

-Self-receptor on the presynaptic membrane that responds to the transmitter that the neuron releases

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22
Q

step 5: Neurotransmitter inactivation

A

1) diffusion: some of the neurotransmitter simply diffuses away from cleft and no longer available to bind to receptors
2) Degradation: Enzymes in cleft break down neurotransmitter
3) Reuptake: Transmitter is brought back into the presynaptic axon terminal; byproducts of degradation by enzymes also may be taken into terminal for reuse
4) astrocyte uptake: nearby astrocytes take up neurotransmitter; can also store transmitters for re-export to the axon terminal

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23
Q

Gap Junction

A

-Fused presynaptic and postsynaptic membrane that allows an action potential to pass directly from on neuron to the next
-Electrical synapses: fast

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24
Q

Chemical synapses

A

-More flexible
-Amplify or diminish signal
-Origins in feeding behavior of single-celled creatures
-Digestive juices secreted on prey (exocytosis-releasing neurotransmitter)
-Parallels to use of neurotransmitters for communications

25
Excitatory synapse
-typically located on dendrites -Round vesicles -Dense material on membranes -Wide cleft (more surface area) -Large active zone -EPSP
26
Inhibitory synapse
-Typically located on cell body -Flat vesicles -Sparse materials on membranes -Narrow cleft -small active zone -IPSP
27
4 criteria for identifying neurotransmitters
1) Transmitter must be synthesized in neuron or be present in neuron 2) When neuron active, chemical must be released produce response in some target 3) Same response must be obtained when the transmitter is experimentally placed on target 4) Mechanism must exist for removing the transmitter from site once work is done
28
Retrograde messages
-Reverse direction -Communicate by sending messages in opposite directions -Influence the release or reuptake of transmitters on the presynaptic sitde
29
Classes of neurotransmitters
1) Small-molecule transmitters 2) Peptide transmitters 3) Lipid transmitters 4) Gaseous transmitters
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1) Small-molecule transmitters
-quick acting neurotransmitters -Synthesized from dietary nutrients and packaged ready for use in axon terminals -Single peptide bonds -Acetylcholine synthesis -Sequential synthesis of 3 amines -Amino Acid transmitters
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Acetylcholine synthesis
-Choline -Acetate -Taken back up and turns back into acetylcholine again
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Sequential synthesis of 3 amines
-Tyrosine, L-Dopa, Dopamine, Norepinephrine, Epinephrine -Enzymes between each part -Make one to make rest -Each step is dependent on enzyme b/c more enzyme = faster rate
33
Amino Acid Transmitters
-Glutamate: main excitatory transmitter -GABA: Main inhibitory transmitter -Gaba is formed by simple modification of glutamate molecule
34
2) Peptide Transmitters
-Neuropeptides -Synthesized through translation of mRNA from instructions in the neurons DNA -Most are assembled on neurons ribosomes, packaged in a membrane by golgi bodies and transported by the microtubules to the axon terminals -act slowly and are not quickly replaced
35
Peptide transmitters use
-Act as hormones that respond to stress -Enable a mother to bond with her infant -Regulate eating and drinking, pleasure and pain -Contribute to learning -Opioids such as morphine and heroin mimic actions of natural brain peptides
36
3) Lipid transmitters
-Endocannabinoids -Class of lipid neurotransmitters synthesized at the postsynaptic membrane to act on receptors at the presynaptic membrane -Occurs naturally to babies after nursing "Milk drink" -Binds to cannabinoid receptors -Includes anandamide and 2-AG both delivered from arachidonic acid
37
Endocannabinoids
-Lipophilic (fat-loving) molecules -Not soluble in water and not stored in vesicles -Once anandamic or 2-AG is synthesized, it diffuses across the synaptic cleft and interacts with its receptor on presynaptic membrane -Can reduce amount of small-molecule transmitter being released
38
CB1
-CB1 is target of all cannabinoids -found at both glutamate and GABA synapses -Cannabinoids act as neuromodulators to inhibit release of glutamate and GABA -Cannabinoids this dampen both neuronal excitation and inhabitation
39
4) Gaseous and Ion Transmitters
-Gaseous transmitters are neither stored in synaptic vesicles nor released from them -Synthesized in cell as needed; easily cross membrane
40
Ion transmitters
-Zn2+ is a transmitter -Actively transported, packaged into vesicles, usually with another transmitter like glutamate, and released into the synaptic cleft
41
1) ionotropic receptors
-Embedded membrane protein with two parts -binding site for neurotransmitter -Pore that regulates ion flow to directly and rapidly change membrane voltage -Allows for movement of ions such as Na+, K+, and Ca2+ across a membrane -When neurotransmitter attaches to binding site, the pore opens or closes changing flow of ions
42
2) Metabotropic receptors
-Embedded membrane protein with a binding site for a neurotransmitter but no pore -Indirectly produces changes in nearby ion channels or in the cell's metabolic activity -Linked to G protein that can affect other receptors of act with second messengers to affect other cellular processes
43
G protein
-Consists of three subunits: Alpha, beta, gamma -Alpha subunit detaches when a neurotransmitter binds to the G protein's associated metabotropic receptor -Detached alpha subunit binds to other proteins in the cell membrane or cytoplasm
44
Second messenger
-Binds to a membrane-bound channel, causing the channel to change its structure and thus alter ion flow through the membrane -Incorporates reaction within the cell protein molecules into the cell membrane, leading to formation of new molecules -Binds to site on the cells DNA to initiate or crease the production of specific proteins
45
Cholinegeric
-Motor neuron -Neuron that uses ACh as its main neurotransmitter -Excites skeletal muscles to cause contractions
46
Nicotinic ACH
-When ACh or nicotine binds to this receptor, its pore opens to permit its ion flow thus depolarizing the muscle fiber -Permits simultaneous efflux of K+ and influx of na+
47
ACh receptors
Controls sympathetic and parasympathetic divisions -ACh receptors on heart are inhibitory; on the gut they are excitatory -ACh receptors with Norepinephrine: NE receptors on heart are excitatory; on the gut they are inhibitory
48
Enteric nervous system
-ENS can act without input from CNS -Uses all four classes of neurotransmitters (more than 30): Mainly serotonin and dopamine
49
Activating system
-Neural pathways that coordinate brain activity through a single neurotransmitter -Cell bodies lie in nucleus in the brainstem, and their axons are distributed through a wide region of the brain -Four systems
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What are the four systems
1) Cholinergic 2) Dopaminergic 3) Noradrenergic 4) Serotonergic
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1) Cholinergic system
-Normal waking behavior -function in attention and memory -Loss of cholinergic associated with Alzheimer's
52
2) 2 Dopaminergic systems
-Nigrostriatal pathways -Mesolimbic pathways
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Nigrostriatal pathways
-Active in maintaining normal motor behavior -Loss of DA is related to muscle rigidity
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Mesolimbic pathways
-Dopamine releases causes repetition of behaviors -Thought to be the neurotransmitter systems most affected by addictive drugs and behavioral addictions -Increases in DA activity linked with schizophrenia -Decrease in DA related to attention deficits -Hippocampus and amygdala (reward pathways)
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3) Noradrenergic system
Plays a role in learning by stimulating neurons to change structure; may also facilitate normal development of brain and organize movements -Imbalances associated with depression/mania
56
4) Serotonergic
-Plays a role in wakeful learning -Imbalances associated with depression, schizophrenia, OCD, sleep apnea, sudden infant death syndrome (SIDS)
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Neural Basis of habituation
-As habituation develops EPSP's get smaller -Motor neuron is receiving less neurotransmitter from sensory neuron across synapse -Habituation must take place in the axon terminal of the sensory neuron -As habituation takes place Ca2+ influx decreases in response to voltage changes associated with an action potential -Reduced sensitivity of Ca2+ channels and decreased release of neurotransmitter
58
Neural basis of sensitization
-In response to action potential on axon of sensory neuron, K+ channels are slow to open -K+ ions cannot repolarize the membrane quickly, so action potentials last longer than normal -Prolongs inflow of Ca2+ and more transmitter is released -

Psych 275 (8 decks)

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