BETTER BENG 327 chapter 5 flashcards

What structure connects cells at an electrical synapse

Gap junction

What forms one gap junction channel

Two connexons

How many connexins form one connexon

Six

How many connexins form one complete gap junction channel

Twelve

What is another name for a connexon

Hemichannel

What does a gap junction directly connect

Two cells’ cytoplasm

How many cell membranes does a gap junction channel cross

Two

What passes through gap junctions

Ions and small molecules

How far apart are membranes at electrical synapses

About 4 nm

In which direction can most electrical synapses transmit

Both directions

What factors regulate gap junction opening

pH, Ca2+, and voltage

How does current spread through electrical synapses

Passively

What happens to electrical response amplitude with distance

It decreases

What happens to electrical response duration during passive spread

It broadens

What are two major benefits of electrical synapses

Speed and synchrony

Why is electrical transmission fast

Direct current flow

What do gap junctions help coordinate in glia

Metabolic support

What first arrives at the terminal during typical evoked transmitter release

An action potential

What does the arriving action potential do to the terminal

Depolarizes it

What channels open when the presynaptic terminal depolarizes

Voltage-gated Ca2+ channels

Which ion enters to trigger transmitter release

Ca2+

What does the rise in presynaptic Ca2+ trigger

Vesicle fusion

What is neurotransmitter release by vesicle fusion called

Exocytosis

Where does released neurotransmitter diffuse

Across the synaptic cleft

What does neurotransmitter bind after crossing the cleft

Postsynaptic receptors

What does postsynaptic receptor activation change

Ion channel activity

What terminates transmitter action in the cleft

Reuptake or degradation

Where are small-transmitter synthesis enzymes made

Cell body

How do small-transmitter synthesis enzymes reach the terminal

Slow axonal transport

What is the lecture’s speed for slow axonal transport

0.5–5 mm/day

Where are small-molecule transmitters generally synthesized

Presynaptic terminal

How do transmitter precursors enter the terminal

Plasma membrane transporters

What loads neurotransmitter into synaptic vesicles

Vesicular transporters

What vesicles usually store small-molecule transmitters

Small clear-core vesicles

What is the diameter of small clear-core vesicles

40–60 nm

How quickly do small-molecule transmitters typically act

Rapidly

Where are peptide neurotransmitters synthesized

Cell body

Where are peptide neurotransmitters packaged into vesicles

Cell body

How do peptide-containing vesicles reach the terminal

Fast axonal transport

What is the lecture’s speed for fast axonal transport

About 400 mm/day

What vesicles store peptide neurotransmitters

Large dense-core vesicles

What is the diameter of large dense-core vesicles

90–250 nm

How quickly do peptide neurotransmitters typically act

Slowly

What is the first criterion for identifying a neurotransmitter

Presynaptic presence and synthesis

What is the second criterion for identifying a neurotransmitter

Ca2+-dependent release after depolarization

What is the third criterion for identifying a neurotransmitter

External application mimics stimulation

What does externally applying a candidate neurotransmitter need to reproduce

The postsynaptic response

What is the basic synaptic vesicle cycle

Loading, docking, priming, fusion, retrieval

What is vesicle docking

Attachment at a release site

What is vesicle priming

Preparation for fusion

What happens during vesicle exocytosis

Transmitter exits; membrane is added

What happens during vesicle endocytosis

Vesicle membrane is retrieved

Why is endocytosis necessary after exocytosis

To recover added membrane

Which is generally slower: endocytosis or exocytosis

Endocytosis

What is the reserve vesicle pool

Vesicles stored for recruitment

What is the releasable vesicle pool

Vesicles ready for release

What recycling time was demonstrated using fluorescent labeling

About one minute

What does “Ca2+ is sufficient for release” mean

Ca2+ alone can trigger release

What experiment demonstrated Ca2+ sufficiency

Presynaptic Ca2+ injection

Is an action potential required when Ca2+ is injected directly

No

What does “Ca2+ is necessary for evoked release” mean

Blocking available Ca2+ prevents release

What experiment demonstrated Ca2+ necessity

Presynaptic BAPTA injection

What is BAPTA

A Ca2+ chelator

What does a Ca2+ chelator do

Binds free Ca2+

Does BAPTA necessarily prevent the presynaptic action potential

No

What does BAPTA prevent despite a presynaptic action potential

Evoked transmitter release

What happens when presynaptic Ca2+ channels are blocked

Evoked release decreases or stops

Where are small clear-core vesicles relative to Ca2+ channels

Nearby

Where are large dense-core vesicles relative to Ca2+ channels

Farther away

Which vesicle type responds to a local Ca2+ rise

Small clear-core vesicles

Which vesicle type requires a broader Ca2+ rise

Large dense-core vesicles

What activity favors neuropeptide release

Sustained high-frequency activity

Why does neuropeptide release require stronger stimulation

Ca2+ must spread farther

How quickly can small clear-core vesicles release transmitter

A fraction of a second

How quickly do large dense-core vesicles release in the lecture

More than a second

What transmitter types can low-frequency activity release

Small transmitters and ATP

What additional transmitter type can high-frequency activity release

Neuropeptides

What protein tethers reserve vesicles to actin

Synapsin

What kinase phosphorylates synapsin

CaMKII

What happens when synapsin is phosphorylated

Reserve vesicles are mobilized

Where do mobilized reserve vesicles move

Release sites

What is synapsin’s main role

Reserve-pool tethering

What is CaMKII’s role in vesicle recruitment

Phosphorylating synapsin

What are the three main exocytosis SNARE proteins

Synaptobrevin, syntaxin, SNAP-25

What is another name for synaptobrevin

VAMP

Which main SNARE is on the vesicle

Synaptobrevin

Which main SNAREs act at the plasma membrane

Syntaxin and SNAP-25

What does the SNARE complex bring together

Vesicle and plasma membranes

What processes do SNAREs support

Docking, priming, and fusion

Do SNAREs directly serve as the Ca2+ sensor

No

What protein senses Ca2+ for rapid vesicle release

Synaptotagmin

What happens when Ca2+ binds synaptotagmin

It triggers fusion

Which protein forms the endocytic vesicle coat

Clathrin

What are clathrin’s three-legged units called

Triskelia

What does clathrin help form in the membrane

A coated pit

Which protein pinches off the endocytic vesicle

Dynamin

Where does dynamin assemble

Around the vesicle neck

What protein removes the clathrin coat

Hsc70

What cofactor helps Hsc70 remove clathrin

Auxilin

What is the main endocytosis protein sequence

Clathrin, dynamin, Hsc70