Module 5 Neurons' Electrochemical Signals to Communicate and Adapt Flashcards

Question

Excitatory and Inhibitory Messages | -Type II Synapse

Answer 1

- Inhibitory - Typically located on the cell body - Flat vesicles - Sparse material on membranes - Narrow Cleft - Small active zone - Found on the neuron cell body

Answer 2

-Chemical transmission may have had its origins in the feeding behavior of single-celled creatures ~Digestive juices are secreted onto prey via EXOCUTOSIS (release of neurotransmitter) ~Prey is captured via ENDOCYTOSIS -This process parallels the use of neurotransmitters for communication

Answer 3

- About 50 different kinds have been identified - Some are inhibitory at one location and excitatory at another - More than one neurotransmitter may be active at a single synapse - No simple one-to-one relationship between a single neurotransmitter and a single behavior

Answer 4

- The chemical must be SYNTHESIZED in the neuron or otherwise be present in it - When the neuron is active, the chemical must be RELEASED and PRODUCE A RESPONSE in some target - The same response must be obtained when the chemical is EXPERIMENTALLY PLACES on the target - A mechanism must exist for REMOVING the chemical from its site of action after its work is done

Answer 5

- Main axon projects to muscle; axon collateral remains in spinal cord and synapses with Renshaw inhibitory interneuron - Motor axon and collateral contain acetylcholine - When the motor neuron is highly excited, it can modulate its activity levels through the Renshaw loop (plus and minus signs)

Answer 6

-Carry a message from one neuron to another by influencing the voltage on the postsynaptic membrane -Have a common message carrying function, such as changing the structure of a synapse -Communicate by sending messages from postsynaptic to presynaptic membrane ~These reverse-direction messages influence the release or reuptake of transmitters

Answer 7

- Small-molecule transmitters - Peptide transmitters - Transmitter gases

Answer 8

-Class of quick-acting neurotransmitters -Synthesized from dietary nutrients and packaged ready for use in axon terminals -Examples ~Acetylcholine (ACh) ~Amines: *Dopamine (DA) *Norepinephrine (NE) *Epinephrine (EP) *Serotonin (5-HT) ~Amino Acids: *Glutamate (Glu) *Gamma aminobutyric acid (GABA) *Glycine (Gly)

Answer 9

-Choline -Acetate ~Two important enzymes *Acetyl coenzyme A *Choline acetyltransferase (ChAT) -Breakdown of Acetylcholine ~Enzyme *Acetylcholinesterase (AChE)

Answer 10

-Tyrosine -> L-Dopa -> Dopamine -> Norepinephrine -> Epinephrine

Answer 11

-Any enzyme that is in limited supply, thus restricting the pace at which a chemical can be synthesized -Example: ~Tyrosine hydroxylase in amine synthesis

Answer 12

``` -Glutamate ~Main excitatory transmitter -GABA ~Main inhibitory transmitter *GABA is formed by a simple modification of the glutamate molecule ```

Answer 13

-Neuropeptide ~A multifunctional chain of amino acids that act as a neurotransmitter ~Synthesized from mRNA on instructions from the cell's DNA ~Do not bind to ion channels; do not have direct effects on the voltage of the postsynaptic membrane -Indirectly influence cell structure and function -Act as hormones that respond to stress -Enable a mother or father to bond with her infant -Regulate eating and drinking and pleasure and pain -Contribute to learning -Opiates such as morphine and heroin mimic the actions of natural brain peptides

Answer 14

-Neither stored in synaptic vesicles nor released from them -Synthesized in call as needed -Easily crosses cell membrane -Example ~Nitric Oxide (NO) ~Carbon Monoxide (CO)

Answer 15

-Ionotropic Receptor -Metabotropic Receptor ~No one neurotransmitter is associated with a single receptor type ~A neurotransmitter may *Bind to an ionotropic receptor and have an excitatory effect on the target cell or *Bind to a metabotropic receptor and have an inhibitory effect *Example **Acetylcholine activates inotropic receptors on muscles for excitation; activates metabotropic receptors on heart to inhibit

Answer 16

-Embedded membrane protein with two parts ~A binding site for a neurotransmitter ~A pore that regulates ion flow to directly and rapidly change membrane voltage ~Allows the movement of ions such as Na+, K+ and Ca2+, across a membrane ~When neurotransmitter attaches to binding site, the pore opens or closes changing the flow of ions

Answer 17

- Embedded membrane protein with a binding site for a neurotransmitter but NO PORE - Indirectly produce changes 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

Answer 18

-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 within the cell membrane or within the cytoplasm of the cell

Answer 19

-A chemical that carries a message to initiate a biochemical process -Activated by a neurotransmitter (the first messenger) -Example ~Alter ion flow in a membrane channel -Formation of new ion channels -Production of new proteins through DNA

Answer 20

- 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 relation between a neurotransmitter and a behavior

Answer 21

-Cholinergic Neuron ~Neuron that uses acetylcholine (ACh) as its main neurotransmitter -Nicotinic ACh Receptor ~When ACh (or nicotine) binds to this receptor, its pore opens to permit ion flow, thus depolarizing the muscle fiber

Answer 22

-Cholinergic neurons from the CNS control both divisions ~Sympathetic (fight-or-flight- response) ~Parasympathetic (rest-and-digest response) -Norepinephrine is also involved in the fight-or-flight response

Answer 23

``` -Activating System ~Neural pathways that coordinate brain activity through a single neurotransmitter ~Cell bodies are located in a nucleus in the brainstem and their axons are distributed through a wide region of the brain ~Four Systems *Cholinergic *Dopaminergic *Noradrenergic *Serotonergic ```

Answer 24

- Normal waking behavior and is thought to function in attention and memory - Loss of cholinergic neurons associated with Alzheimer's disease

Answer 25

-Nigrostriatal path ~Involved in coordinating movement; degenerates in Parkinson's disease -Mesolimbic Path ~Enhances responses to environmental stimuli; implicated in addiction and schizophrenia

Answer 26

- Plays a role in learning by stimulating neurons to change their structure; may also facilitate normal development of the brain and organize movements - Imbalances associated with depression or mania

Answer 27

- Plays a role in wakefulness and learning | - Imbalances associated with depression, schizophrenia, obsessive-compulsive disorder, sleep apnea

Answer 28

-Relatively permanent change in behavior that results from experience

Answer 29

- The nervous system's potential for change that enhances its ability to adapt - Required for learning and memory

Answer 30

-"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 that A's efficiency, as one of the cells firing B, is increased"

Answer 31

- Eric Kandel was awarded a Nobel Prize in 2000 for his descriptions of the synaptic basis of learning using APLYSIA - Used enduring changes in simple defensive behaviors to study underlying changes in the snail's nervous system

Answer 32

-Learning behavior in which a response to stimulus weakens with repeated stimulus presentations -Example ~Gill withdrawal response in the marine snail APLYSIA CALIFORNICA

Answer 33

- 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 neurotransmitter is released from a habituated neuron than from a nonhabituated one - 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

Answer 34

-Learning behavior in which the response to a stimulus strengthens with repeated presentations of that stimulus because the stimulus is novel or stronger than normal

Answer 35

- In response to an action potential on axon of 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 Ca2+ and more transmitter is released - Sensitization is the opposite of habituation at the molecular and behavioral levels - In sensitization, more Ca2+ influx results in more transmitter being released - In habituation, less Ca2+ influx results in less neurotransmitter being released

Answer 36

- 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 plays an important role in carrying instructions regarding structural changes to nuclear DNA

Answer 37

- Conserves the body's oxygen when you are not breathing is a useful survival strategy - This energy -conserving response under water is common to many animals

Answer 38

- Excitatory message | - Inhibitory message

Answer 39

-That says speed up

Answer 40

-Says to slow down

Answer 41

-The same transmitter that activates skeletal muscles ~Loewi's experiment ACh acts to inhibit heartbeat, to slow it down -It turns out that ACh excites skeletal muscles in the somatic nervous system, causing them to contract, and may either excite or inhibit various internal organs in the automatic system ~It turns out that the ion channel and it's associated receptor, not the molecule itself, determine whether the messenger will be excitatory or inhibitory -ACh is the chemical messenger associated with the slowed heartbeat in diving bradycardia -First neurotransmitter discovered in the PNS and CNS; activates skeletal muscles in the SNS; either excites or inhibits internal organs in the ANS

Answer 42

- Stimulated a nerve to the heart, the accelerator nerve, and heart rate increased - Both are the same substance, produced by the adrenal glands located atop the kidneys - Adrenaline is the name more people know, in part because a drug company used it as a trade name, but epinephrine is common parlance in the science community - Chemical messenger that acts as a neurotransmitter in the CNS and as a hormone to mobilize the body for fight or flight during times of stress; also know as adrenaline

Answer 43

- A chemical closely related to epinephrine (EP) - ACh from the vagus nerve inhibits heartbeat, and EP from the accelerator nerve excited it - Neurotrantmitter that accelerates heart rate in mammals; found in the brain and in the sympathetic division of the ANS; also known as noradrenaline

Answer 44

-Chemical messengers released by a neuron onto a target to cause an excitatory or inhibitory effect -Outside the CNS, many of the same chemicals, epinephrine among them, circulate in the bloodstream as hormones ~Under control of the hypothalamus, the pituitary gland releases hormones into the bloodstream to excite or inhibit targets, such as organs and glands in the autonomic and enteric nervous systems -Travel throughout the body to distant targets, their actions are slower than those of CNS neurotransmitters prodded by the lightning-quick nerve impulse -Chemical with an excitatory or inhibitory effect when released by a neuron onto a target -The real difference between neurotransmitters and hormones is the distance they travel, within the same body, before they encounter their receptors

Answer 45

- Travel throughout the body to distant targets, their actions are slower than those of CNS neurotransmitters prodded by the lightning-quick nerve impulse - The real difference between neurotransmitters and hormones is the distance they travel, within the same body, before they encounter their receptors

Answer 46

-Three findings have helped researchers understand it's neural basis ~In 1919 Tréatikoff (1974) studied the brains of nine Parkinson patients on autopsy and found that the substantia nigra, a small midbrain nucleus, had degenerated; in the brain of one patient who had Parkinsonlike symptoms on only one side of the body, the substantia nigra had degenerated on the side opposite that of the symptoms ~Chemical examination of the brains of Parkinson patients showed that disease symptoms appear when the level of dopamine (DA), then a proposed neurotransmitter, was reduced to less than 10 percent of normal in the basal ganglia ~Confirming the role of dopamine in a neural pathway connecting the substantia nigra to the basal ganglia, Urban Ungerstedt found in 1971 that injecting a neurotoxin called 6-hydroxydopamine into rats selectively destroyed these dopamine-containing neurons and produced symptoms of Parkinson disease -Loss of dopamine-containing substantia nigra neurons has been linked to environmental factors such as insecticide, herbicide, fungicides, flu virus, and toxin drugs; about 10% of people with Parkinson disease have a mutation in one of several specific genes, and it may also be the case that people who are susceptible to environmental influences also have a genetic predisposition -Treatments for neurological diseases are usually much more effective the earlier they are started, so early detection is important -Motor system disorder correlated with dopamine loss in the substantia nigra; and reduction in voluntary movement

Answer 47

- Itself in other brain areas has been linked not only to motor behavior but also to some forms of learning and to neural structures that mediate reward and addiction - Amine neurotransmitter involved in coordinating movement, attention, learning, and reinforcing behaviors

Answer 48

- Common round granule that contains neurotransmitter molecules - Membranous compartment that encloses a fixed number (called a quantum) of neurotransmitter molecules

Answer 49

- Central to synapse function because neurotransmitter chemicals must bridge this gap to carry a message from one neuron to the next - Gap separating the neuronal presynaptic member from the postsynaptic membrane

Answer 50

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

Answer 51

- The junction where messenger molecules are released from one neuron to interact with the next neuron - The junction at which messenger molecules are released when stimulated by a action potential

Answer 52

- Forms the axon terminal | - Axon terminal membrane on the transmitter, or output, side of a synapse

Answer 53

- Forms the dendritic spine, and the space between the two is the synaptic cleft - Membrane on the transmitter, or input, side of a synapse

Answer 54

- The axon terminal are specialized structures, including mitochondria, the organelles that supply the cell's energy needs large compartments that hold several synaptic vesicles; and microtubules, which transport substance, including neurotransmitter, to the terminal - Membranous compartment that holds several vesicles containing a neurotransmitter

Answer 55

-A five-step process of transmitting information across a chemical synapses from the presynaptic side to the postsynaptic neuron ~The neurotransmitter is synthesized somewhere inside the neuron ~It is packed and stored within vesicles at the axon terminal ~It is transported to the presynaptic membrane and released into the cleft in response to the action potential ~It binds to and activates receptors on the postsynaptic membrane ~It is degraded or removed, so it will not continue to interact with a receptor and work indefinitely

Answer 56

- Several main classes of transmitters, and they are derived in different ways - The small-molecule transmitters are synthesized in the axon terminal from building blocks that are often derived from food - Transporters - Mitochondria - Peptide transmitter - Lipid transmitter - Gaseous transmitter - Ion transmitter - 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 in the terminal, and still others are attached to the presynaptic membrane; these sites correspond to the steps by which a transmitter is transported from a granule to the membrane, ready to be released into the synaptic cleft

Answer 57

- Are protein molecules that move substances across cell membranes, and they are responsible for packaging some neurotransmitter classes into vesicles - Protein molecules that pumps substances across a membrane

Answer 58

-The axon terminal provide the energy needed both to synthesized precursor chemicals into the transmitter and to power transporters

Answer 59

- Are synthesized in the cell body according to instructions in the neuron's DNA, packaged in membranes on the Golgi bodies, and transported on microtubules to the axon terminal - May also be manufactured within the presynaptic terminal by ribsomes using mRNA transported to the terminal

Answer 60

-Cannot be packaged and stored in vesicles, which are composed of lipids, but are rather synthesized "on demand" when an action potential reaches the axon terminal

Answer 61

- Also generated within the cells by enzymes, but they differ from classical signaling molecules in many ways - Production is regulated, are able to permeate cell membranes and this are not stored within the cell

Answer 62

- Are not biochemically synthesized - Like all other atoms heavier than helium, they are made in the heart of dying stars - Can be packaged and stored in vesicles, usually along with other transmitter types, and then released into the synaptic cleft

Answer 63

- Synaptic vesicles loaded with neurotransmitters must dock release sites on the presynaptic membrane - The vesicles are primed to prepare them to fuse the presynaptic membrane, voltage changes on the membrane set the release process in motion - Calcium cation play a critical role - Presynaptic membrane is rich in voltage-activated calcium channels, and the surrounding extracellular fluid is rich in Ca2+ - The action potential's arrival opens these calcium channels, allowing an influx of calcium ions into the axon terminal - Primed vesicles quickly fuse with the presynaptic membrane in response to the calcium influx and empty their contents into the synaptic cleft by exocytosis - The vesicles from storage granules and on filaments and then move up to replace the vesicles that just emptied their contents

Answer 64

- Transmitter-activated Receptors - Ionotropic Receptors - Metabotropic Receptor - Autoreceptors - Quantum

Answer 65

- Have binding sites for the transmitter; these properties of the receptors on the postsynaptic membrane determine the effect on the postsynaptic cell - Protein that has a binding site for a specific neurotransmitter and is embedded in the membrane of a cell

Answer 66

- Associated with a pore that can open to allow ions to pass through the membrane voltage in one of two possible ways; these ion channels may allow Na+ to enter the neuron, depolarizing the postsynaptic membrane, and so have an excitatory action on the postsynaptic neuron. - Or they may allow K+ to leave the neuron or Cl- to enter the neuron, hyperpolarizing the postsynaptic membrane, and so typically have an inhibitory action on the postsynaptic neuron - Embedded membrane protein act as (1) a binding site for a neurotransmitter and (2) a pore that regulates ion flow to directly and rapidly change membrane voltage

Answer 67

- May initiate intracellular messages systems; this may open an ion channel, this modulating either excitation or inhibition or influencing other functions of the receiving neuron - 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

Answer 68

- A neurotransmitter may interact with receptors on the presynaptic membrane:it may influence the cell that just released it - A neurotransmitter may activate presynaptic receptor to receive messages from their own axon terminals - Serve a critical function as part of a negative feedback loop, providing information about whether adjustment to synaptic communication should be made

Answer 69

- Varies in size, but each size appeared to be a multiple of the smallest potential - 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 it's output

Answer 70

-The smallest postsynaptic potential is produced by the release of the contents of just one synaptic vesicles -The number of neurotransmitter molecules ~Producing a postsynaptic potential large enough to initiate a postsynaptic action potential requires the stimultaneous release of many quanta fr the presynaptic cells

Answer 71

-Show that the number of quanta released fr the presynaptic membrane in response to a single action potential depends on two factors ~The amount of Ca2+ that enters the axon terminal in response to the action potential ~The number of vesicles docked at the membrane, waiting to be released *Both factors are relevant to synaptic activity during learning

Answer 72

-Chemical transmission would not be an effective messenger system if the neurotransmitter lingered within the synaptic cleft, continuing to occupy and stimulate receptors; if this happened, the postsynaptic cell could not respond to other messages sent by the presynaptic neuron -After a neurotransmitter has done it's work, it is quickly removed from receptor sites and from the synaptic cleft -Inactivation is accomplished in at least four ways ~Diffusion ~Degradation ~Reuptake ~Astrocyte Uptake -Highlighting the flexibility of the synaptic function, an axon terminal has chemical mechanisms that enable it to respond to the frequency of its own use -If the terminal is minal is not often used; however, enzymes within the terminal buttons may break down 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

Answer 73

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

Answer 74

-Enzymes in the synaptic cleft break down the transmitter

Answer 75

-Membrane transporters specific to that transmitter may bring it back into the presynaptic axon terminal for reuse. The by-products of degradation by enzymes also may be taken back into the terminal to be used again in the cell

Answer 76

-Some neurotransmitters are taken up by neighboring astrocytes. Astrocytes can also store certain transmitters for re-export to the axon terminal

Answer 77

-Which an axon synapses with a muscle end plate, releasing acetylcholine ACh

Answer 78

-Which the axon terminal of a neuron synapses with a dendrite or dendritic spine of another neuron synapses with a dendrite or dendritic spine of another neuron

Answer 79

-Have no specific targets but instead secrete their transmitter chemicals into the extracellular fluid

Answer 80

-A termianl synapses with a tiny blood vessel, a capillary, and secretes its transmitter directly into the blood

Answer 81

-Dendrites also may send messages to other dendrites

Answer 82

-Can modulate the fraction of large areas of tissue or even the entire body

Answer 83

-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 -Formed when connexin proteins in one cell membrane make a hemichannel that connects to a hemichannel in an adjacent cell's membrane, allowing ions to pass from one neuron to the other in both directions -Constitute a regulated gate between cells because they can either be open or closed -Eliminate the brief delay in information flow- about 5 milliseconds per synapse- of chemical transmission -Are found in mammalian brain as well, where in some regions they allow groups of interneurons to synchronize their firing rhythmically -Also allow glial cells and neurons to exchange substances -There are different connexin subunits that give rise to different pore sizes, which allows selectivity for specific small molecules ~Large biomolecules such as nucleic acids and proteins cannot fit through gap junction -Further increase the signaling diversity between neurons ~Intraneuronal communication may occur via dendrodendritic and axoaxonic gap junction -At axon terminals synapsing on dendrites can cell bodies allow for dual chemical and electrical synaptic transition -Allow no such plasticity and are built for speed and efficient communication

Answer 84

-Have only recently been discovered, and their functional properties have yet to be determined in the mammalian

Answer 85

-Can show plasticity; they can amplify or diminish a signal and thus mediate learning

Answer 86

-It influences transmembrane ion flow either to increase or to decrease the likelihood that the cell with which is comes in contact will produce an action potential

Answer 87

- Are typically on the shafts or spines of dendrites | - Have round synaptic vesicles

Answer 88

- Are typically on the cell body | - Are flattened

Answer 89

-Is denser and wider in an excitatory synapse that it is in inhibitory synapse

Answer 90

-On an excitatory synapse is larger than that on a inhibitory synapse

Answer 91

- An excitatory dendritic tree - An inhibitory cell body - If the message is to be stopped, it is best stopped by inhibiting the cell body to close to the initial segment

Answer 92

-Inhibition blocks excitation by using "cut em off at the pass" strategy -Excitation overcoming inhibition -Excitatory synaptic inputs that are farther away from the soma are larger, to counteract the loss signal that occurs over distance -Inhibited state, the only way to generate an action potential is to reduce cell body inhibition "open the gates" strategy ~The excitatory message is like a racehorse ready to run down the track ~But first the inhibitory starting gate must be removed

Answer 93

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

Answer 94

-A suspect chemical that has not yet been shown to meet all the criteria in the CNS

Answer 95

- Circular set of connections - Made by the axon collateral and the interneuron in the spinal cord forms a feedback circuit that enables the motor neuron to inhibit itself from overexcitation, should it receive a great many excitatory inputs from other parts of the CNS - If the loop is blocked, as can be done with the toxin strychnine, motor neurons become overactive, producing convulsion that can choke off respiration and so cause death

Answer 96

-Is used more broadly now than it was when researchers began to identify these chemicals -The term applies to chemicals that ~Carry a message from the presynaptic membrane of one neuron to another by influencing postsynaptic membrane voltage ~Change the structure of a synapse ~Communicate by sending messages in the opposite direction *These retrograde (reverse-direction) messages influence the release or reuptake of transmitters on the presynaptic side

Answer 97

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

Answer 98

-Quick-acting neurotransmitter synthesized in the axon terminal from products derived from the diet -Has been released from a terminal button, is can quickly be replaced at the presynaptic membrane -Main components are derived from the food we eat, diet can influence their abundance and activity in our bodies ~This fact is important in the design of drugs that act on the nervous system -Many neuroactive drugs are designed to reach the brain by the same route that small-molecule transmitters or their precursor chemicals follow: the digestive tract

Answer 99

-ACh is present at the junction of neurons and muscles, including the heart, as well ass in the CNS -Are synthesized from choline and acetate by two enzymes and then broken down -Choline is among the breakdown products of fats in foods such as egg yolk, avocado, salmon, and olive oil -Acetate is a compound found in acidic foods, such as vinegar and lemon juice -Acetyl Coenzyme A (acetyl CoA) carries acetate to the synthesis site, and a second enzyme, choline acetyltransferase (ChAT), transfers the acetate to choline to synthesize acetycholine -After ACh has been released into the synaptic cleft and diffuses to receptor sites on the postsynaptic membrane, a third enzyme, acetycholinesterase (A ChE), reverses the process, breaking down the transmitter by detaching acetate from choline ~The breakdown products can then be taken back into the presynaptic terminal for reuse

Answer 100

- Dopamine (DA) - Norepinephrine (NE) - Epinephrine (EP) - DA loss figures in Parkinson disease - EP is the excitatory transmitter at the amphibian heart - NE is the excitatory transmitter at the mammalian heart - The biochemical sequence in which these amines are synthesized; the precursor chemical is tyrosine, an amino acid abundant in food (hard cheese and bananas are good sources) - The enzyme tyrosine hydroxylase changes tyrosine into L-dopa, which other enzymes convert into dopamine, then norepinephrine, and finally, epinephrine - The supply of the enzyme tyrosine hydroxylase in limited, so the rate of dopamine, norepinephrine, and epinephrine can be produced, regardless of how much tyrosine is present or ingested - The rate-limiting factor can be bypassed by the oral administration of L-dopa, which is why L-dopa is a medication used in treating Parkinson disease

Answer 101

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

Answer 102

- The amine transmitter serotonin, (5-HT for 5-hydroxytryptamine) is synthesized from the amino acid L-tryptophan - Tryptophan us abundant in pork, turkey, milk, bananas, among other foods.

Answer 103

-Amine neurotransmitter; helps to regulate mood and aggression, appetite, and arousal, perception of pain, and respiration

Answer 104

- Two amino acid transmitters, glutamate (Glu) and gamma-aminobutyric acid (GABA), are closely related - These two transmitters are the workhouse of the brain because so many synapses use them - In the forebrain and cerebellum, glutamate is the main excitatory transmitter and GABA is the main inhibitory transmitter - Histidine is an amino acid the serves as the primary bilogical source of the transmitter histamine (H)

Answer 105

- Amino acid neurotransmitter; typically excites neurons - Is a neurotransmitter in excitatory synapses - Is widely distributed in the CNS neurons, but it becomes a neurotransmitter only if it is appropriately packaged in vesicles in the axon terminal

Answer 106

- Amino acid neurotransmitter; typically inhibits neurons | - Is a neurotransmitter in inhibitory synapses

Answer 107

-Is a much more common inhibitory transmitter in the brainstem and spinal cord, where it acts within the Renshaw loop

Answer 108

-Neurotransmitter that controls arousal and walking; can cause the constriction of smooth muscles; when activated in allergic reactions, constricts airway and contributes to asthma

Answer 109

-Are synthesized as nucleotides- the kind of molecules that make up DNA and RNA -Adenosine triphosphate (ATP) consist of a molecule of adenine attached to a ribose sugar molecule and three phosphate groups ~Removal of the three phosphate group leaves adenosine, a molecule that plays a central role in promoting sleep, suppressing arousal, and regulating blood flow to various organs through vasodilation (dilation of the blood vessels)

Answer 110

-More than 50 short amino chains of various length form the families of peptide transmitters, or neuropeptides -Synthesized through the translation of mRNA from instructions contained in the neuron's DNA, neuropeptides are multifunctional chains of amino acids that act as a neurotransmitter -Are made in the axon terminal, but most are assembled in the neuron's ribosome, packaged in the membrane by Golgi bodies, and transported by the microtubules to the axon terminals ~The entire process of neuropeptide synthesis and transport is relatively slow compared with the nearly ready-made small-molecule transmitters -Act slowly and are not quickly replaced -A part of the amino acid chain in each of these naturally occurring opioid peptides is structurally similar to the other ~Enkephalins ~Dynorphins ~Endorphins -Morphine mimics this part of the chain; this discovery of naturally occurring morphine-like neuropeptides suggest that one or more of them might have analgesic properties and may take part in pain perception ~It turns out that beta-endorphin, released in response to exercise and thought to be responsible for runner's high, has many times the analgesic potency of morphine

Answer 111

-Short, multifunctional amino acid chain (fewer than 100 amino acids); act as a neurotransmitter and can act as a hormone; may contribute to learning -Perform an enormous range of functions in the nervous system, as might be expected from their large numbers -Act as hormones that respond to stress, enable a mother bond with her infant, regulate eating and drinking and pleasure and pain, and probably contribute to learning -Are metabotropic and have no direct effects on postsynaptic membrane voltage ~Instead peptide transmitters activate synaptic receptors that indirectly influence cell structure and function -Digestive processes degrade neuropeptide amino acid chains, so they generally cannot be taken orally as drugs,, whereas small-molecule transmitters can

Answer 112

-Opium, morphine, and related synthetic chemicals such as heroin- long known both to produce euphoria and to reduce pain- mimic the actions of endogenous brain opioid neuropeptides ~Enkephalins ~Dynorphins ~Endorphins

Answer 113

-Class of lipid neurotransmitters, including anandamide and 2-AG, synthesized at the postsynaptic membrane to act on receptors at the presynaptic membrane; affects appetite, pain, sleep, mood, memory, anxiety, and the stress response -Anandamide and 2AG (2-arachidonoylglycerol), both derived from arachidonic acid, an unsaturated fatty acid ~Poultry and eggs are especially good sources -Participate in a diverse set of physiological and psychological processes that affect appetite, pain, sleep, mood, memory, anxiety, and the stress response -Are lipophilic (fat-loving) molecules, they are not soluble in water and are not stored in vesicles ~Rather that endocannabinoid are synthesized on demand after a neuron has depolarized and calcium has entered -Calcium activates the enzyme transacylase, the first step in producing anandamide -One anandamide and 2-AG is synthesized, it diffuses across the synaptic cleft and interacts with it's receptors on the presynaptic membrane -Both molecules act as retrograde neurotransmitters, for a time reducing the amount of small-molecule transmitter being released -The postsynaptic neuron reduces the amount of incoming neural signal

Answer 114

- Receptor is the target of all cannabinoids, weather generated by the body (endocannabinoid), from plants (phytocannabinoids), or synthetically - Are found at both glutamate and GABA synapse, so cannabinoids acts as a neuromodulators to inhibit release of glutamate and GABA - Cannabinoids this dampen both neuronal excitation and inhibition

Answer 115

-Are obtained from the hemp plant Cannabis Sativa and Cannabis indica -These plants have been used medically and recreationally for thousands of years, but only recently was an extract from cannabis synthesized -Early in the last century many constituents of cannabis, including tetrahydrocannabinol (THC) and cannabidiol (CBD), were isolated and their chemical structure determined -In 1967, Gaoni and Mechoulam reported the structure of the THC molecule, the main psychoactive constituent in cannabis -Next, investigators determined how THC is metabolized ~The process is quite slow, which explains why THC can be detected in urine for weeks after cannabis use -Research on the physiological and psychological effects of THC in animals and people, which began after it's isolation and purification, is ongoing -24 years after the structure of the THC molecule was determined, the first cannabinoid receptor (CB1) was found. -Receptor are activated by endogenous molecules, which motivated researchers to look for endogenous cannabinoids -In 1992, anandamide was isolated and it's structure determined, but it took another couple of decades to figure out the endocannabinoids acts as retrograde transmitters

Answer 116

-Gaseous neurotransmitter; acts for example, to dilate blood vessels, aid digestion, and activate cellular matablism

Answer 117

-Gaseous neurotransmitter; activates cellular metabolism

Answer 118

-Gaseous neurotransmitter; slows cellular metabolism

Answer 119

-As water-soluble gases, they are neither stored in synaptic vesicles nor released from them; instead, the cell synthesizes them on demand -After synthesis, each gas diffuses away, easily crossing the cell membrane and immediately becoming active -Both NO and CO activate metabolic (energy-expanding) processes in cells, including processes modulating the production of other neurotransmitters -H2S prevents oxygen from binding in the mitochondria and thus functions to slow down metabolism -All three serve as chemical messengers in many parts of the body -No and H2S control intestinal wall muscles and dilate blood vessels in active brain regions, allowing these regions to receive more blood ~Since they dilate the blood vessels in sexual organs, both are active in producing penial erection *Drugs used to treat erectile dysfunction in men (Viagra and Cialis), act by enhancing the chemical pathways influenced by NO **No does not of itself produce sexual arousal

Answer 120

-An ion transmitter that is packaged and stored in vesicles and that is then released and interacts with several receptors Zinc is not biologically synthesized but rather, was formed by fusion reactions in starts -Is actively transported, packaged into vesicles- usually with another transmitter like glutamate- and released into the synaptic cleft -Zinc interacts with several different receptors to cause biological change -When vesicular Zinc becomes dysregulated, cognitive decline associated age and Alzheimer disease occur, whereas maintaining Zinc homeostasis or correcting it with drug treatment protect cognitive ability

Answer 121

-Allow ions such as K+, Na+, Cl-, and Ca2+ to move across a membrane -An ionotropic receptors has two parts ~A binding site for a neurotransmitter ~A pore, or channel -When a neurotransmitter attaches to the binding site, the receptor quickly changes shape, either opening the pore and allowing ions to flow through it or closing the pore and blocking the ion flow -Bring about rapid changes in membrane voltage and are usually excitatory (they trigger an action potential)

Answer 122

- A binding site for a neurotransmitter but lacks its own pore through which ions can flow - Through a series of steps, activated metabotropic receptors indirectly produce changes in nearby membrane-bound ion channels or in the cell's metabolic activity - Consist of a single protein that spans the cell membrane, it's binding site facing the synaptic cleft - Also allow for the possibility that a single neurotransmitter's binding to a receptor can activate an escalating sequence of event called an Amplification Cascade

Answer 123

-Guanly nucleotide-binding protein coupled to a metabotropic Receptor; when activated, binds to other proteins -Consist of three subunits ~Alpha ~Beta ~Gamma

Answer 124

-A protein molecule that assembles with other protein molecules

Answer 125

- Detaches when a neurotransmitter binds to the G protein's associated metabotropic receptor - The detached subunit can then bind to other proteins within the cell's membrane or it's intracellular fluid - Binds to nearby ion channels in the membrane, the channel structure changes, modifying influence the membrane's electrical potential

Answer 126

- Chemical that initiates a biochemical process when activated by a neurotransmitter - Carries instructions to other cell structures - Bind to a membrane-bound channel, causing the channel to change it's structure and thus alter ion flow through the membrane - Initiate a reaction that incorporates intracellular (within the cell) protein molecules into the cell membrane, resulting, for example, in the formation of new ion channels - Bind to sites on the cell's DNA to initiate or cease the production of specific proteins

Answer 127

-Effect result in may downstream proteins being either activated or deactivated

Answer 128

-Each reactor has many ionotropic or metabotropic receptors -Each subtype has slightly different properties, which confer different activities ~Can include the presence or absence of binding sites for other molecules, how long a channel remains open or closed, and the ability to interact with intracellular signaling molecules

Answer 129

- Neuron that uses acetylcholine as it's main neurotransmitter; cholinergic applies to any neuron that uses ACh as it's main transmitter - Involves the SNS, without the system movement would not be possible - A skeletal muscle, cholinergic neurons are excitatory, producing muscular contractions

Answer 130

- Just as a single main neurotransmitter servers the SNS, so does a single main receptor, a transmitter-activated ionotropic channel - When ACh binds to this receptor, it's pore opens to permit ion flow, thus depolarizing the muscle fiber - Is large enough to permit the stimultaneous efflux of K+ and influx of Na+ - The molecule structure of nicotine, a chemical found in tabacco, activates the nAChr in the same way that ACh does, which is how this receptor got its name - The nicotine molecular structure is sufficiently similar to Each that nicotine acts as a mimic, fitting into ACh receptor binding sites

Answer 131

- Other neurotransmitter also occupy these cholinergic axon terminals and are released into the muscle along with ACh - One neuropeptide called Calcitonin gene (CGRP), acts through CGRP metabotropic receptors to increase the force with which a muscle contracts

Answer 132

- Neural pathways that coordinate brain activity through a single neurotransmitter; it's cell bodies lie in a brain stem nucleus; axons are distributed through a wide CNS region - Cholinergic - Dopaminergic - Noradrenergic - Setotonetgic

Answer 133

- Active in maintaining attention and waking EEG pattern - Thought to play a role in memory by maintaining neuron excitability - Death of cholinergic neurons and decreased in ACh in the neocortex are thought to be released in Alzheimer disease

Answer 134

-Nigrostriatal Pathways ~Active in maintaining normal motor behavior ~Loss of DA is related to muscle rigidity and dyskinesia in Parkinson disease -Mesolimbic Pathway ~DA release causes repetition of behavior ~Thought to be the neurotransmitter system most affected by addictive drugs and behavioral addictions ~Increases in DA activity may be related to schizophrenia ~Decreases in DA activity may be related to deficits of attention -When dopamine neurons in the substantia nigra are lost, the result is a condition of extreme muscular rigidity -Opposing muscles contract at the same time, making it difficult for an affected person to mover ~Also exhibit rhythmic tremors, especially of the limbs, which signals a release of formerly inhibited movement -Parkinsin disease can actually be triggered by the ingestion of certain toxic drugs -The Case of the Frozen Addict ~Those drugs may act as selective neurotoxins that specifically kill DA neurons in the substantia nigra -May be the neurotransmitter most affected in addiction- to food, to drugs, and to other behaviors that involve a loss of impulse control ~Common feature of addictive behaviors is that stimulating the mesolimbic dopaminergic system enhances responses to environmental stimuli, thus making those stimuli attractive and rewarding -Some Parkinson patients who take dopamine receptors agonist as medications show a loss of impulse control that manifests in such behaviors as pathological gambling, hypersexuality, and compulsive shopping -Play a role in Schizophrenia

Answer 135

- Active in maintaining emotional tone - Decreases in NE activity are thought to be related to depression - Increases in NE are thought to be related to mania (overexcited behavior) - Decreases NE activity is associated with hyperactivity and attention-deficit/ hyperactivity disorder - May play a part in learning by stimulating neurons to change their structure - NE may also facilitate healthy brain development and contribute to organizing movement - Some symptoms of major-depression

Answer 136

-Active in maintaining waking EEG pattern -Changes in serotonin activity are related to obsessive-compulsive disorder, tics, and schizophrenia -Decreases in serotonin activity are related to depression -Abnormalities in brainstorm 5-HT neurons are linked to disorders such as sleep apnea and SIDS -Serotonin plays a role in learning ~Some symptoms of depression may be related to decrease activity in serotonin neurons, and drugs commonly used to treat depression act on 5-HT neurons -Decreases serotonergic activity is related to symptoms observed in obsessive-compulsive disorder -Evidence also points to a link between abnormalities in serotonergic nuclei and conditions such as sleep apnea and sudden infant death syndrome (SIDS)

Answer 137

- Degenerative brain disorder related to aging; first appears as progressive memory loss and later develops into generalized dementia - Whci begins with minor forgetfulness, progresses to major memory dysfunction, and later develops into generalized dementia, show a profound loss of cholinergic neurons at autopsy

Answer 138

- Are drugs that either inhibit the enzyme ACh (elevating the levels), or raise the number of nicotine receptors - each is synthesized from nutrients in food, the role of diet is maintaining ACh levels also is being investigated

Answer 139

- Behavior disorder characterized by delusions, hallucinations, disorganized speech, blunted emotion, agitation or immobility, and a host of associated symptoms - Is one of the most common and most debilitating psychiatric disorders, affecting about 1 in 100 people

Answer 140

- Appeared very suddenly after drug injection; they would find themselves "frozen"- only able to move in "slow motion" - Patient 1, had to think through every moment, and describe himself as stiff, slow, almost mute, and catatonic - MPTP (1-methly-4-phyenl-1,2,3,6-tetrahdropyridine) poor technique during the drug's (heroin) synthesis - MPP+ (1-methyl-4-phyenlpyridinium) a neurotoxin - Autopsy of MPTP overdose showed selectively lost dopamine neurons in the substantia nigra - Fetal neurons, before they develop dendrites and axons, can survive transplanting, mature, and secrete neurotransmitters

Answer 141

-Mood disorder characterized by prolonged feelings of worthlessness and guilt, the disruption of normal eating habits, sleep disturbances, a general slowing of behavior, and frequent thoughts of suicide -May be related to decreased activity of noradrenergic neurons ~Some symptoms of Mania

Answer 142

- Disordered mental state of extreme excitement | - May be related to increased activity in these same neurons

Answer 143

-Decreases in NE has also been associated with the disorder

Answer 144

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

Answer 145

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

Answer 146

-Relatively persistent or even permanent change in behavior that results from experience

Answer 147

- Hebb theorized "When an axon of cell A is near enough to excite cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic changes take place in one or both cells such as A's efficiency, as one of the cells firing B, is increased" - Simply put cells that fire together wire together - A synapse that physically adapts in this way

Answer 148

-Learned behavior in which the response to a stimulus weakens with repeated presentations -Develops with all our senses; become insensitive to the customary background sensations of sound, touch, smell, taste, and even vision -Does not result from an inability of either sensory neuron or the motor neuron to produce action potentials; in response to direct electrical stimulation, both the sensory and motor neuron retain the ability to generate action potentials after habituation -Electrical recordings from the motor neuron shows that as habituation develops, the excitatory postsynaptic potentials (EPSPs) in the motor neuron become smaller ~The most likely way in which EPSPs decrease in size is that motor neurons is receiving less neurotransmitter from the sensory neuron across the synapse; if less neurotransmitter is being received, then the changes accompanying habituation must take place in the presynaptic axon terminal of the sensory neuron -Less Ca2+ influx results in less neurotransmitter being released -The change takes place in calcium channels

Answer 149

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

Answer 150

- Learned behavior in which the response to a stimulus strengthens with repeated presentation - An enhanced response to some stimulus, is the opposite of habituation - The organism becomes hyperresponsive to stimulus rather than accustomed to it - The opposite of habituation at the molecular level as well as at the behavioral level - More Ca2+ influx results in more transmitters being released - The change takes place in potassium channels

Answer 151

- Syndrom characterized by physiological arousal associated with recurrent memories and dreams arising from a traumatic event that occurred months or years earlier - A heightened response to stimuli, suggesting that the disorder is in part related to sensitization

Answer 152

-Small but Mighty, summarizes experimental evidence about structural changes in dendritic spine

Answer 153

-Plays an important role in carrying instructions regarding these structural changes to nuclear DNA -Involvement come from studies of the fruit fly Drosophila ~Two genetic mutations in the fruit fly can produce similar learning deficiencies ~Both render the second messenger cAMP inoperative- but in opposite ways *One mutation, called dunce, lacks the enzymes necessary to degrade cAMP, so the fruit fly has abnormally high cAMP levels *Other mutation, called rutabaga, reduces the level of cAMP below the normal range for Drosphila neurons ~Fruit flies with either mutation are impaired in acquiring habituated and sensitized responses because their cAMP cannot be regulated *New synapses seem to be required for learning to take place, and the second messenger cAMP seems to carry instructions to form them -More lasting habituation and sensitized are mediated by relatively permanent changes in neuronal structure- by fewer or more synaptic connections- and the effects can be difficult to alter ~As a result of sensitization for example, symptoms of PTSD can persist indefinitely

Module 5 Neurons' Electrochemical Signals to Communicate and Adapt Flashcards

(178 cards)