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PSYCH 255 > Chapter 5 > Flashcards

Chapter 5 Flashcards

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1
Q

Neurotransmitter

A

chemical released by neuron onto target that has excitatory or inhibitory effect (or other more complex effects)

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2
Q

Hormone

A

chemical circulating in bloodstream (outside CNS)

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3
Q

Structures of Chemical Synapses (4)

A

1) Presynaptic membrane
2) Postsynaptic membrane
3) Synaptic Vesicle
4) Synaptic Cleft

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4
Q

Structure of Chemical Synapses

1) Presynaptic membrane

A

membrane on output side of synapse (axon terminal) that sends out NT

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5
Q

Structure of Chemical Synapses

2) Postsynaptic Membrane

A

membrane on input side of synapse (dendritic spine) that receives NT

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6
Q

Structure of Chemical Synapses

3) Synaptic Vesicle

A

membrane structure that contains neurotransmitters

  • protects NT from breakdown
  • provides measurement (NT in proper quantity)
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7
Q

Structure of Chemical Synapses

4) Synaptic Cleft

A

gap seperating presynaptic membrane from postsynaptic membrane

  • where NT are released when stimulated by AP
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8
Q

Storage Granules

A

large compartments that hold several synaptic vesicles

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9
Q

(4) Steps of Neurotransmission

A

1) Synthesis & Storage
2) Release of NT
3) Receptor Activation
4) Deactivation of NT

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10
Q

Neurotransmission

1) Synthesis & Storage

A

NT derived in 2 ways

Vesicles stored in granules, attached to microfilaments or presynaptic membrane

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11
Q

1) Synthesis & Storage

  • (2) ways in which neurotransmitters are derived
    • which varieties of NT are synthesized via each process?
A

1) synthesized in axon terminal from chemical precursors in food/diet that are pumped into cell via transporter proteins

  • Small-molecule transmitters
  • Transmitter Gases

2) synthesized in soma using DNA code, packaged in vesicles on Golgi bodies & transported on microtubules to axon terminal
* neuropeptides

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12
Q

Storage of Neurotransmitters

  • which are stored & which arent?
A

NO

STORED:

  • Small-molecule Transmitters
  • Neuropeptides

NOT STORED:

  • ​Transmitter Gases
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13
Q

Neurotransmission

2) Release of NT

A

AP propagated on presynaptic membrane

  • opens vs-Ca2+ channels on terminal
  • Ca2+ influx → binds to protein calmodulin
    • forms complex
  • complex binds to vesicles on …
    • presynaptic membrane → empty contents into synaptic cleft via exocytosis
    • microfilaments → replace vesicles ^
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14
Q

2) Release of NT
* Amount of NT released depends on?

A

1) availability (# of vesicles docked @ membrane waiting to be released)
2) amount of Ca2+ entering axon terminal in response to AP

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15
Q

3) Activation of Receptor Sites

A

NT released from vesicle diffuses across synaptic cleft to bind to transmitter-activated receptors embedded in postsynaptic membrane

  • postsynaptic neuron can be affected in 3 ways (depending on type of NT & receptor)
  • also can interact with presynaptic receptors (autoreceptors) to influence cell that released it
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16
Q

3) Activation of Receptor Sites
* (3) ways in which postsynaptic neuron is affected by binding of NT to transmitter-activated receptors

A

a) Depolarization of postsynaptic membrane causing EPSP (open Na+ ion channels)
b) Hyperpolarization of postsynaptic membrane causing IPSP (open K+ or Cl- channels)

c) Initiation of other chemical reactions:
→ that modulate excitatory or inhibitory effect
OR
→ influence functions of postsynaptic neuron

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17
Q

3) Activation of Receptor Site

  • Autoreceptors
    • ​define
    • functions (2)
A

NT may interact with presynaptic receptors (autoreceptors) that influence presynaptic neuron

Self-receptors in neural membrane that respond to NT released by neuron

  • indicates that they received message from their own axon terminals
  • monitor message & see how much NT is used
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18
Q

4) Deactivation of NT

A
  • Once message has stopped & NT has done its work,* NT are removed from receptor sites & synaptic cleft in (4) ways
    1) Diffusion away from synaptic cleft
    2) Degradation via enzymes in cleft or terminal (after reuptake)
    3) Reuptake into presynaptic neuron for subsequent re-use
    4) Glial uptake
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19
Q

Deactivation of Neurotransmitters

1) Diffusion

A

NT diffuse away from synaptic cleft & are no longer available to bind to receptors

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20
Q

Deactivation of Neurotransmitters

2) Degradation

A

by enzymes in synaptic cleft OR in terminal (after reuptake)

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21
Q

Deactivation of Neurotransmitters

3) Reuptake

A

specific membrane transporter proteins bring NT or by-products of enzymatic degradation into axon terminal for reuse

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22
Q

Deactivation of Neurotransmitters

4) Glial Uptake

A

NT taken up by nearby glial cells

  • can store for re-export to axon terminal
  • enzymatic degradation
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23
Q

Although there are many different types of synapses, which (2) do we discuss?

A

Axodendritic: axon terminal ends on dendrite (or dendritic spine) of another

Axomuscular: axon synapses with muscle end plate

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24
Q

(2) Classifications of Chemical Synapses

A

Type I Synapse

Type II Synapse

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25
Q

Type I Synapse

  • location
  • characteristics/features (5)
A

excitatory

typically on dendrites

large active zone

wide cleft

round vesicles

denser material on pre/postsynaptic membrane

26
Q

Type II Synapse

  • location
  • characteristics/features (5)
A

inhibitory

typically on soma

small active zones

narrow cleft

flat vesicles (fewer vesicles & receptors)

sparse material on pre/postsynaptic membranes

27
Q

Which Type of Synapse (I or II) is more influential?

A

Type II Synapses are more influential since closer to axon hillock

28
Q

Types of Neurotransmitters

  • (4) points
A
  • ~ 50 different kinds
  • can be inhibitory at one location & excitatory at another (depending on receptor type)
  • >1 can be active at 1 synapse
  • NO 1-to-1 relationship between single NT & single behavior
29
Q

(4) Criteria for Identifying Neurotransmitters

A

1) Must be synthesized or present in neuron
2) Must be released by active neuron & produce response in target cell
3) Same response must be obtained when chemical is experimentally placed on target
4) Existing mechanism for removal of chemical from site of action after its work is done

30
Q

Types of Neurotransmitters (3)

A

1) Small-molecule NT
2) Neuropeptides
3) Transmitter Gases

31
Q

1) Small-molecule NT

A
  • fast-acting NT
  • synthesized from chemical precursors in diet & packaged in axon terminal
  • can produce all 3 types of effects
32
Q

1) Small Molecule Transmitters
* Examples? (3)

A

Acetylcholine

Amines

Amino Acids

33
Q

1) Small Molecule Transmitters
* Examples → a) Acetylcholine

A

acetate (vinegar)

+

choline (fatty foods → egg yolk)

34
Q

1) Small Molecule Transmitters
* Examples → Amines (4)

A

Tyrosine = precursor (in diet) for:

→ dopamine

→ norepinephrine

→ epinephrine (adrenaline)

Tryptophan = precursor for:

→ seratonin >>> melatonin

35
Q

1) Small Molecule Transmitters
* Examples → Amino Acids

A

Glutamate → GABA

36
Q

2) Neuropeptides

A

chains of AAs synthesized in soma from mRNA based on DNA code

  • shipped to axon terminal
  • often act as hormones
  • slower-acting
  • replaced slower
  • only work at metabotropic receptors*
  • activate synaptic receptors that indirectly influence cell structure/function
37
Q

2) Neuropeptides
* examples (2)

A

Oxytocin

Endorphins

38
Q

3) Transmitter Gases

A

NOT stored in vesicles

synthesized in cell as needed

easily diffuse across cell membrane

39
Q

3) Transmitter Gases
* examples (2)

A

Nitric Oxide (NO)

  • control intestinal wall muscles, BV dilation in active brain regions & sexual organs (erectioN)

Carbon Monoxide (CO)

→ activate metabolic (E-expending) processes in cells

40
Q

(2) Classes of Receptors

A

1) Ionotropic - direct & fast
2) Metabotropic - indirect & slow

41
Q

1) Ionotropic Receptors

  • define
  • function
A

embedded membrane protein with binding site for neurotransmitter & pore (similar to gated channel)

  • regulates ion flow to directly & rapidly change membrane voltage
42
Q

2) Metabotropic Receptors

  • define
  • general function
A

embedded membrane protein with binding site for NT

  • linked to G protein

→ indirectly produce changes in nearby ion channels OR in cell’s metabolic activity

43
Q

Metabotropic Receptors → Indirect Effects (2)

A

NT binds to receptor → triggers G protein activation

→ α subunit detaches

a) binds to ion channel
b) binds to enzyme

44
Q

Metabotropic Receptors → Indirect Effects

Detached α subunit…

a) binds to ion channel

b) binds to enzyme

A

binding of α subunit to nearby ion channel causes structural change in channel

→ modifies flow of ions through it

45
Q

Metabotropic Receptors → Indirect Effects

When detached α subunit…

a) binds to ion channel

b) binds to enzyme

A

enzyme activates second messenger that carries instructions to other intracellular structures

46
Q

Metabotropic Receptors → Indirect Effects

When detached α subunit…

b) binds to enzyme

  • (3) possible effects
A

Enzyme activates second messenger, which can…

a) bind to membrane channel → structural change to alter ion flow
b) initiate reaction → causes proteins in cell to become incorporated into membrane (i.e. form new ion channel)
c) instruct DNA to start/stop production of a protein

47
Q

Neurotransmitter Systems: ANS → SNS

A

Axons of motor neurons in CNS project to skeletal muscles

  • aka cholinergic → ACh = main NT

ACh binds to ionotropic nicotinic receptors (nAChr) on muscle fibers

  • opens channels → K+ outflow & Na+ influx
  • depolarizes membrane → AP → muscle contraction
48
Q

Neurotransmitter Systems: PNS → ANS

A

Both divisions controlled by ACh neurons emanating from CNS

These CNS neurons synapse with…

  • Parasympathetic neurons that contain ACh
  • Sympathetic neurons that contain NE

metabotropic receptors

49
Q

Neurotransmitter Systems: CNS

A

many neuropeptides have specific & localized functions

many small-molecule transmitters have general functions & larger # of targets

50
Q

Neurotransmitter Systems: CNS

  • many neuropeptides have specific & localized functions
    • example?
A

Oxytocin

  • as a hormone → role in labor contractions, breastfeeding (milk-drop)
  • as a NT → role in bonding between parent/offspring & mates
51
Q

Neurotransmitter Systems: CNS

  • many small-molecule transmitters have general functions
    • examples? (3)
A

GABA → regulates neural inhibition

Glutamate → regulates neural excitation

Activating Systems

52
Q

Neurotransmitter Systems: CNS

  • Many Small Molecule Transmitters have general functions

→ Activating Systems

  • define
A

neural pathways that coordinate brain activity through a single NT

  • cell bodies are in nucleus
  • axons distributed through wide region of brain
53
Q

Activating Systems (4)

A

1) Noradrenergic
2) Serotenergic
3) Cholinergic
4) Dopaminergic
a. nigrostriatial pathways
b. mesolimbic pathways

54
Q

1) Noradrenergic System

A

projections from locus coeruleus

  • related to attention & arousal
  • decreases related to depression & ADHD
  • increases related to mania
55
Q

2) Serotenergic System

  • projections?
  • general function
  • increases/decreases related to?
A

projections from raphe nucleus in brainstem

related to arousal (wakefulness)

  • increases related to schizophrenia
  • decreases related to depression
56
Q

2) Serotenergic System
* targeted by?

A

antidepressants

extacy

cocaine

57
Q

3) Cholinergic System

  • projections?
  • related to?
  • role in?
  • decreases…
A

projects from midbrain & basal forebrain nuclei

  • related to arousal
  • role in memory & attention
  • decreases in ACh related to Alzheimer’s​
    • ​loss of cholinergic neurons
58
Q

4) Dopaminergic System
* operates in (2) distinct pathways

A

a) Mesolimbic Dopaminergic System
b) NIgrostriatal Dopaminergic System

59
Q

4) Dopaminergic System → 2 distinct pathways
a) Mesolimbic Dopaminergic System

  • projections
  • functions (2)
  • increases related to?
A

projects from ventral tegmental area

  • role in pleasure & reward
    • ​stimulating this system enhances responses to stimuli → more attractive & rewarding
  • mediates drug addiction
    • DA in this system is most affected in addiction
  • ↑ increases related to schizophrenia (↑mental/motor agitation)
60
Q

4) Dopaminergic System → 2 distinct pathways
b) Nigrostriatal Dopaminergic System

  • projections
  • function
  • decreases related to?
A

projects from substantia nigra to striatum (caudate & putamen)

  • role in normal motor behavior
    • ​​coordinating movement, force/exertion
  • ↓ DA decrease related to Parkinson’s
    • ​muscular rigidity & movement release (dyskinesia)
61
Q

Dopaminergic System → Drugs

A

Drugs cannot selectively target one pathway of Dopaminergic system

→ causes side-effects as a result

  • ex) Drugs to treat Schizophrenia may cause Parkinson’s-like symptoms & vice versa

PSYCH 255 (7 decks)

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