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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
**Type I Synapse** * location * characteristics/features (5)
**excitatory** typically on **dendrites** **large** active zone **wide** cleft **round** vesicles **denser** material on **pre/postsynaptic membrane**
26
**Type II** Synapse * location * characteristics/features (5)
**inhibitory** typically on **soma** **small** active zones **narrow** cleft **flat** vesicles *(fewer vesicles & receptors)* **sparse** material on **pre/postsynaptic membranes**
27
Which Type of Synapse (I or II) is more influential?
**Type II** Synapses are more influential since **closer to axon hillock**
28
Types of Neurotransmitters * (4) points
* **~ 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
(4) Criteria for **Identifying Neurotransmitters**
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
Types of Neurotransmitters (3)
1) Small-molecule NT 2) Neuropeptides 3) Transmitter Gases
31
1) Small-molecule NT
* **fast-acting** NT * synthesized from chemical precursors in **diet** & packaged in **axon terminal** * can produce **all 3 types** of effects
32
1) Small Molecule Transmitters * **Examples? (3)**
Acetylcholine Amines Amino Acids
33
1) Small Molecule Transmitters * Examples → **a) Acetylcholine**
**acetate** (*vinegar)* + **choline** *(fatty foods → egg yolk)*
34
1) Small Molecule Transmitters * Examples → **Amines** (4)
_Tyrosine_ = precursor (in diet) for: → **dopamine** **→ norepinephrine** **→ epinephrine** (adrenaline) _Tryptophan_ = precursor for: → **seratonin \>\>\>** melatonin
35
1) Small Molecule Transmitters * Examples → **Amino Acids**
Glutamate → GABA
36
2) Neuropeptides
**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
2) Neuropeptides * **examples (2)**
**Oxytocin** **Endorphins**
38
3) Transmitter Gases
NOT stored in vesicles synthesized in cell **as needed** easily **diffuse** across cell membrane
39
3) Transmitter Gases * examples (2)
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
(2) Classes of Receptors
1) **Ionotropic -** direct & fast 2) **Metabotropic -** indirect & slow
41
**1) Ionotropic** Receptors * define * function
**embedded** membrane protein with **binding site** for **neurotransmitter** & **pore** (similar to gated channel) * regulates **ion flow** to **directly & rapidly** change **membrane voltage**
42
2) **Metabotropic** Receptors * define * general function
**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
**Metabotropic Receptors →** Indirect Effects (2)
NT binds to receptor → triggers **G protein** activation → α subunit **detaches** a) binds to **ion channel** b) binds to **enzyme**
44
Metabotropic Receptors → Indirect Effects Detached α subunit... **_a) binds to ion channel_** b) binds to enzyme
binding of α subunit to nearby **ion channel** causes **structural change** in channel → **modifies flow of ions** through it
45
Metabotropic Receptors → Indirect Effects When detached α subunit... a) binds to ion channel **_b) binds to enzyme_**
**enzyme** activates **second messenger** that carries instructions to other **intracellular structures**
46
Metabotropic Receptors → Indirect Effects When detached α subunit... **b) binds to enzyme** * (3) possible effects
**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
Neurotransmitter Systems: ANS **→ SNS**
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
Neurotransmitter Systems: PNS → **ANS**
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
Neurotransmitter Systems: **CNS**
many **neuropeptides** have **specific** & **localized** functions many **small-molecule transmitters** have **general** functions & larger # of **targets**
50
Neurotransmitter Systems: CNS * many **neuropeptides** have **specific** & **localized** functions * example?
**Oxytocin** * as a **hormone →** role in labor contractions, breastfeeding (milk-drop) * as a **NT** → role in **bonding** between **parent/offspring & mates**
51
Neurotransmitter Systems: CNS * many **small-molecule transmitters** have **general** functions * examples? (3)
**GABA →** regulates neural **inhibition** **Glutamate →** regulates neural **excitation** **Activating Systems**
52
Neurotransmitter Systems: **CNS** * Many **Small Molecule Transmitters** have **general** functions **_→ Activating Systems_** * define
**neural pathways** that **coordinate brain activity** through a **single NT** * **cell bodies** are in **nucleus** * **axons** distributed through **wide** **region** of **brain**
53
Activating Systems (4)
1) Noradrenergic 2) Serotenergic 3) Cholinergic 4) Dopaminergic a. nigrostriatial pathways b. mesolimbic pathways
54
1) **Noradrenergic** System
projections from **locus coeruleus** * related to **attention & arousal** * **decreases** related to **depression & ADHD** * **increases** related to **mania**
55
**2)** **Serotenergic** System * projections? * general function * increases/decreases related to?
projections from **raphe nucleus** in brainstem related to **arousal** (wakefulness) * **increases** related to **schizophrenia** * **decreases** related to **depression**
56
2) **Serotenergic** System * targeted by?
**antidepressants** extacy cocaine
57
3) **Cholinergic** System * projections? * related to? * role in? * decreases...
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
4) **Dopaminergic** System * operates in **(2)** distinct **pathways**
a) **Mesolimbic** Dopaminergic System b) **NIgrostriatal** Dopaminergic System
59
4) Dopaminergic System → 2 distinct pathways a) **Mesolimbic** Dopaminergic System * projections * functions (2) * increases related to?
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
4) Dopaminergic System → 2 distinct pathways b) **Nigrostriatal** Dopaminergic System * projections * function * decreases related to?
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
Dopaminergic System → Drugs
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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