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Psych 275 > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

Otto Loewi

A

Frog heart experiment: role of vagus nerve and neurotransmitter acetylcholine in slowing heart rate
↳ changed heartbeat = message passed through fluid

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2
Q

Acetylcholine

A

Activates skeletal muscles in the somatic nervous system

May excite or inhibit internal organs in the autonomic nervous system
↳ excitatory/innibitory action dependent upon the ion channel (not the molecule itself)

Acetylcholine in vagus nerve → inhibits heartbeat

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3
Q

Hormone vs. Neurotransmitter

A

Neurotransmitter: Chemical released by a Neuron onto a target → binds to postsynaptic cell and has an excitatory or inhibitory effect

Hormone: outside of central nervous system, same chemicals circulate in bloodstream → distant targets, action slower than NT

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4
Q

Otto loewi’s subsequent research

A

Epinephrine (EP, or adrenaline) → chemical messenger that acts as a hormone and mobilizes body for fight or flight funny stress: works as NT in the CNS

Norepinephrine (NE, or noradrenaline)→ NT found in brain and in sympathetic division of ANS: accelerates heart rate in mammals

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5
Q

Neurotransmitters→ today’s understanding

A

100 is maximum number of neurotransmitters

Confirmed is 60

Most work being done by 10 → largest influence on human behavior

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6
Q

Electron microscope

A

Projects beam of electrons through thin slice of tissue

Identify vesicles using these images *

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7
Q

Chemical Synapse

A

Junction where messenger molecules (NT) are released from one Neuron to excite or inhibit the next

Most synapses in NS are chemical

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8
Q

Pre-synaptic membrane → axon terminal

A

Where action potential terminates to release the chemical message

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9
Q

Postsynaptic membrane → dendritic spine

A

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

Gates and channels NT bind to

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10
Q

Tripartite Synapse

A

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

Not a structure within a cell

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11
Q

Microtubule

A

Transport structure that brings substances to the axon terminal

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12
Q

Synaptic vesicle

A

Presynaptic

Small membrane-bound spheres that contain one or more neurotransmitters

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13
Q

Storage granule

A

Presynaptic

Membranous compartment that holds several vesicles → large storage compartment

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14
Q

Anterograde synaptic transmission: steps 1-5

A

Transmission between cell A and B → presynaptic to postsynaptic

1.) NT is synthesized inside Neuron

2.) packaged and stored within vesicles at axon terminal

3.) then transported to presynapticmembrane and released into cleft in response to action potential

4.) binds to and activates receptors on postsynaptic membrane

5.) then degraded or removed so it no longer will interact with receptor

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15
Q

Step 1: Neurotransmitter synthesis

A

Synthesized in axon terminal: small-molecule transmitters →made from food consumed → pumped into cell via transporters → protein molecules in cell membrane pump substances across membrane

Synthesized in cell body: peptide transmitters→ created according to DNA → transported on microtubules to axon terminal

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16
Q

Step 2: Neurotransmitter packaging

A

Regardless of origin: NT in vesicles can be found in 3 locations at axon terminal:

Some warehoused in granules
Some attached to microfilaments
Some attached to presynaptic membrane

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17
Q

Step 3: Neurotransmitter release

A

Synaptic vesicles loaded with NT dock near release sites on presynaptic membrane

Vesicles are primed to prepare them to fuse rapidly in response to calcium influx

At terminal, AP opens the voltage-sensitive Ca2+ channels

Ca2+ enters terminal and binds to protein complex

Complex causes some vesicles to empty contents into synapse

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18
Q

Step 4: Receptor-site activation

A

After release, NT diffuses across synaptic cleft to activate receptors on postsynaptic membrane

Transmitter-activated receptors: protein embedded in membrane of cell that has binding site for a specific NT

Properties of receptor determine effect on postsynaptic cell

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19
Q

Postsynaptic neurotransmitter responses

A

Depolarize the postsynaptic membrane → causing excitatory action on the postsynaptic Neuron (EPSP)

Hyperpolarize postsynaptic membrane → causing inhibitory action on postsynaptic Neuron (IPSP)

Initiate other chemical reactions that modulate excitatory or inhibitory effect or influence other functions on receiving Neuron

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20
Q

Autoreceptor

A

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

Retrograde transmission → NT interact with presynaptic cell: feedback loop to regulate NT release

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21
Q

Step 5: Neurotransmitter inactivation

A

Diffusion: some NT simply diffuse away from synaptic cleft and are no longer available to bind to receptors

Degradation: enzymes in synaptic def break down NT

Reuptake: transmitter brought back into presynaptic axon terminal for reuse

Astrocyte uptake: nearby astrocytes take up NT

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22
Q

Flexibility in synaptic function

A

If terminal is very active → amount of NT made and stored increases

If terminal is not often used → enzymes in terminal buttons may breakdown excess transmitter

Axon terminals may even send messages to cell body requesting increased supplies of NT

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23
Q

Synapse types: 7 total

A

Dendrodendritic→ dendrites send messages to other dendrites

Axodendritic→ axon terminal of one Neuron synapses on dendritic spine of another

Axoextracellular→ terminal with no specific target: secretes transmitter into extracellular fluid

Axosomatic → Axon terminal ends on cell body

Axosynaptic → Axon terminal ends on another terminal

Axoaxonic → axon terminal ends on another axon

Axosecretory → axon terminal ends on tiny blood vessel and secretes transmitter directly into blood

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24
Q

Electrical synapses

A

Very fast → eliminate delays in info flow

Gap junction: fused pre and postsynaptic membrane that allows an action potential to pass directly from one Neuron to next

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25
Q

Excitatory Synapse characteristics

A

Located on dendrites

Round vesicles

Dense material on membranes

Wide cleft

Large active zone

26
Q

Inhibitory Synapse characteristics

A

Located on cell body

Flat vesicles

Sparse material on membranes

Narrow cleft

Small active zone

27
Q

Excitatory action within a Neuron

A

Location of excitatory synapse: dendritic tree closer to cell body

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

28
Q

Inhibitory action within Neuron

A

Location of inhibitory synapse: Close to initial segment

Best stopped by inhibiting cell body close to initial segment → inhibition blocks or cuts excitation from passing through postsynaptic cell

29
Q

4 criteria for identifying neurotransmitters

A

1.) transmitter must be synthesized or present in the Neuron

2.) when active, chemical must be released and produce a response in some target

3.) same response must be obtained if done experimentally

4.) mechanism must exist for removing transmitter

30
Q

Neurotransmitter may also

A

Carry message from one Neuron to another by influencing voltage on postsynaptic membrane

Change structure of a synapse

Communicate by sending messages in the opposite direction

31
Q

Classes of neurotransmitters → 4

A

Small-molecule transmitters

Peptide transmitters

Lipid transmitters

Gaseous transmitters

32
Q

Small-molecule transmitters

A

Class of quick-acting NT

Synthesized inside of cell from dietary nutrients and packaged in Axon terminals

Can be quickly replaced at presynaptic terminal

Some drugs designed to emulate the route of small molecule transmitters

33
Q

Examples of small-molecule transmitters

A

Acetylcholine (ACh)→ present at junction of neurons and muscles and the CNS

Amines (common biochemical pathway/relatedness) → dopamine (DA), norepinephrine (NE), epinephrine (EP), serotonin (5-HT)

Amino acids → glutamate: main excitatory transmitter, and GABA: Mann inhibitory transmitter (2 most abundant NT in brain)

Purines→ synthesized as nucleotides: regulate blood flow, sleep, arousal, etc.

34
Q

Peptide transmitters

A

Neuropeptides → short, multifunctional amino acid chain that acts as a NT and can act as a hormone

Synthesized through translation of mRNA from instructions in neurons DNA

Most assembled in ribosomes, packaged in membrane by Golgi bodies, and transported by microtubules to axon terminals

Act slowly and not replaced quickly

Wide range of functions:
↳ act as hormones that respond to stress (cortisol)
↳ enable mother to bond with infant (oxytocin)
↳ regulate eating/drinking and pleasure/pain

Have NO direct effects on postsynaptic membrane voltage → activate receptors that indirectly influence cell

35
Q

Peptic transmitter examples

A

Opioids → Met-enkephalin, beta-endorphin, dynorphin

Neurohypohyseals → vasopressin, oxytocin

Secretins → secretin, motility, glucagon, growth hormone-releasing factor

Insulins → insulin, insulin growth factors

Gastrins → Gastrin, cholecystokinin

36
Q

Lipid transmitters

A

Can’t be stored in resides → created on demand at level of cell membrane

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

37
Q

Endocannabinoids → Lipid transmitter

A

Synthesized at postsynaptic membrane to act on receptors at the presynaptic membrane → postsynaptic Neuron reduces amount of incoming neural signal: Reduces amount of small-molecule transmitter being released

Hypothesized: synthesized on demand after a Neuron has depolarized and calcium has entered

CB1 receptor is target of all cannabinoids

Found at both glutamate and GABA synapses
↳ act as neuromodulators to inhibit release of glutamate and GABA
↳ thus dampen neuronal excitation and inhibition

38
Q

Gaseous and ion transmitters

A

Gaseous → synthesized in cell as needed: not stored in synaptic vesicles; easily can cross cell membrane
↳ chemical messengers in body→ modulate NT production

Ion transmitters → zinc as transmitter: actively transported,packaged into vesicles (usually with another transmitter ie. Glutamate) and released into cleft

39
Q

Ionotropic receptors

A

Embedded membrane protein with two parts:
- binding site for a NT and a PORE that regulates ion flow to directly and rapidly change membrane voltage

Allows 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

40
Q

Metabotropic receptor

A

Embedded membrane protein with a binding site for a NT but NO PORE

Indirectly produces changes in nearby ion channels or in the cells metabolic activity

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

41
Q

Amplification Cascade → metabotropic receptor

A

A single NT binding to a metabotropic receptor can activate an escalating sequence of events

Protiens can be activated or deactivated

42
Q

Metabotropic receptor coupled to ion channel

A

Transmitter binds to receptor

Activates gene protein then ion channel is indirectly activated

The cx subunit of the G protein binds to a channel causing a structural change in the channel that allows ions to pass through it

43
Q

Metabotropic receptor coupled to an enzyme

A

Transmitter binds to receptor

Binding of transmitter triggers the activation of a G protein in both reactions

The cx subunit binds to an enzyme which activates a second messenger

The second messenger can activate other cell processes

44
Q

Receptor subtypes

A

Neurotransmitter → ionotropic → metabotropic

Acetylcholine → nicotinic→ 5 muscarinic
Dopamine → none → 5 dopamine
GABA → GABAa → GABAb
Serotonin → 5-HT3 → 12 5-HT

45
Q

Neurotransmitter systems and behavior

A

A single Neuron may use one transmitter at one synapse and a different transmitter at another

Different transmitters may coexist in the some terminal or synapse or even vesicle

Caution against cause-and-effect assumptions regarding relationship between NT and behavior

46
Q

Neurotransmission in Somatic nervous System

A

Cholinergic Neuron (motor neurons) → use acetylcholine as its main neurotransmitter: excites skeletal muscles to cause contractions

Nicotinic ACh receptor (nAChr)→ opens exclusively to ACh and depolarizes muscle fiber: when ACh or nicotine binds to this receptor, its pore opens to permit ion flow, depolarizing muscle fiber

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

47
Q

Activating System of ANS → sympathetic

A

Sympathetic division: arouses body for action, producing fight-or-flight response

Controlled by acetylcholine neurons that emanate from CNS (spinal cord) → CNS neurons synapse with sympathetic neurons that contain norepinephrine

Cholinergic neurons in CNS synapse with NE neurons to produce fight or flight

During sympathetic arousal norepinephrine turns up heart rate and turns down digestive functions
↳NE receptors on heart = excitatory
↳NE on gut = inhibitory

48
Q

Activating System of ANS → parasympathetic

A

Controlled by acetylcholine neutrons that emanate from 2 levels of spinal cord

Cholinergic neurons in CNS synapse with autonomic ACh neurons in parasympathetic division to prep body for rest-and-digest

Acetylcholine turns down heart rate and turns up digestive functions because receptors on these organs are reversed:
On heart = inhibitory
On gut = excitatory

49
Q

Enteric nervous System

A

Can act without input from CNS

Uses all four classes of NT → more than 30: mainly serotonin and dopamine

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

Neurons attached to gut lining

50
Q

4 activating systems in CNS

A

Cholinergic, dopaminergic, noradrenergic, and serotonergic→ one system for each small-molecule transmitter

Activating system: neural pathways that coordinate brain activity through a single NT
↳ cell bodies lie in a nucleus in the brainstem, and their axons are distributed throughout brain

51
Q

Cholinergic System

A

Normal waking behavior → thought to function in attention and memory

Loss of cholinergic neurons associated with Alzheimer disease

52
Q

Dopaminergic System

A

Involved with movement and motor behavior

Nigrostriatal pathways: active in maintaining normal motor behavior (coordination) → loss of DA is related to muscle rigidity and dyskinesia in Parkinson disease

Mesolimbic pathways: dopamine release causes repetition of behaviors → most affected in addiction behaviors: related to impulse control

Increases in DA may be related to schizophrenia
Decreases in DA activity may be related to deficits of attention

53
Q

Noradrenergic System

A

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

Also may facilitate normal development of the brain and organize movements

Imbalances associated with depression and mania

Decreased NE activity related to ADHD and hyperactivity

54
Q

Serotonergic System

A

Plays a role in wakefulness and learning → maintaining waking EEG pattern

Imbalances associated with depression, schizophrenia, obsessive-compulsive disorder, sleep apnea, sudden infant death syndrome

55
Q

Neuroplasticity

A

The nervous systems potential for change, which enhances its ability to adapt

Required for learning and memory → reconfigure synapses and tissues to maximize learning

Cells that fire together wire together

56
Q

Hebb Synapse

A

Axon of cell A near enough to excite cell B and repeatedly takes part in firing it, some metabolic change or growth process takes place in one or both cells → A’s efficiency as one of the cells firing B is increased

2 neurons proximal to each other → I cell fires enough → firing rate influences other cell → strengthen neural connections

Cells that fire together wire together

57
Q

Eric Kandel and Aplysia → habituation

A

Awarded 2000 Nobel prize for basis of learning experiment using Aplysia (snails)

Used enduring changes in simple defensive behaviors to study underlying changes in nervous system

Habituation: learning behavior in which a response to a stimulus weakens with repeated presentations of the stimulus → Gill withdrawal response to being sprayed with water: lessened

58
Q

Neural basis of habituation

A

Habituation develops → excitatory postsynaptic potentials in motor neuron become smaller: motor neuron is receiving less NT from sensory neuron across synapse (limit action potentials)

Habituation must take place in axon terminal of sensory neuron

Less activity from a habituated Neuron relative to nonhabituated one → Ca2+ influx decreases in response to voltage changes

Less Ca2+ influx results in less NT being released → opposite of sensitization

Reduced sensitivity of Ca2+ channels and decreased release of NT

59
Q

Sensitization response

A

Learning behavior where response to stimulus strengthens with repeated presentations BECAUSE stimulus is novel or stronger than normal

Present Stimulus once, wait a while, show more powerful stimulus

60
Q

Neural basis of sensitization

A

Response to action potential on axon of sensory Neuron → K+ channels are SLOW to open

K+ ions cannot repolarize membrane quickly → AP last longer than normal: prolongs inflow of Ca2+ and more transmitter is released

More Ca2+ influx results in more transmitter being released → opposite of habituation at molecular and behavioral levels

61
Q

Learning relative to 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 → can persist for MONTHS

Number and size of sensory synapses CHANGE
↳ habituated: less connections due to overstimulation
↳ sensitized: builds more connections

Transcription and translation of nuclear DNA initiates structural changes → formation of new synapses and spines

Second-messenger cAMP molecule plays important role in carrying instructions regarding structural changes to nuclear DNA

Psych 275 (6 decks)

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