Chapter 5 - Synaptic Communication

Question 1

electrical current (ions) flowing from one cell to another - no NT release

Answer 1

electrical synapses

Question 2

An organized collections of protein channels in cell membranes that allows ions and small molecules to pass between adjacent cells. The protein channels that make up _______ consist of two connexons.
One connexon resides in the membrane of one cell. It aligns and joins the connexon of the neighboring cell, forming a continuous aqueous pathway by which ions and small molecules can freely pass (passively) from one cell to the other.

Each connexon consist of six subunits called connexins.
Connexon - the channel, the functional unit
Connexin protein - subunits making up the channels (6 sub units)

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Neurites of two cells connected by a gap junction. An enlargement showing gap junction channels, which bridge the cytoplasm of the two cells. Ions and small molecules cal pass in both directions through these channels. Six sonnecin subunits comprise one connexon, two connexons comprise one gap junction channel, and many gap junction channels comprise one gap junction

Answer 2

gap junction

Question 3

the most numerous and diverse neuroglial cells in the CNS

Answer 3

astrocytes

Question 4

Why electrical synapses?

Answer 4

1) speed (fast)
2) high threshold to fire (Ohms law) but, they fire synchronously
3) metabolic signals: components that can pass through non-selective channels.

Question 5

chemical synapses

Answer 5

can mediate excititory or inhibitory signalling
more complex - plasticity
amplifies signals

Question 6

axon to dendrite

Answer 6

axondendritic

Question 7

axon to cell body

Answer 7

axosomatic

Question 8

axon to axon

Answer 8

axoaxonic

Question 9

dendrite to dendrite

Answer 9

dendrodendritic

Question 10

asymmetrical synapses, excititory

Answer 10

gray’s type I

Question 11

symmetrical synapses, inhibioty

Answer 11

Gray’s Type II

Question 12

is a synapse between a motor neuron and skeletal muscle. (outside the CNS)

Answer 12

neuromuscular junction

Question 13

What are the seven basic steps of neurochemical release?

Answer 13

1) NT synthesis
2) load NT into synaptic vesicles
3) vesicles fuse to presynatpic terminal (membrane)
4. NT release into synaptic cleft
5) binds to postsynaptic receptors
6) biochemical/electrical response elicited in postsynaptic cell
7) removal of NT from synaptic cleft

Question 14

Classes of Neurotransmitters

Answer 14

1) Amino acids ex: glycine
2) Biogenic Amines ex: DA
3) Peptides ex: Dynorphin

Question 15

a single neuron always produces the same transmitter at every one of its synapses.

Answer 15

Dale’s law

Question 16

process by which vesicles release their contents

Answer 16

Exocytosis

Question 17

types of endocytosis

Answer 17

kiss and run
merge and recycle
bulk endocytosis

Question 18

release most NT, reseals and moves into cytoplasm to be refilled.

short amount of time.
release most NT
recycled quickly

Answer 18

Kiss and Run (leave)

Question 19

vesicle fuses completely with the membrane

Answer 19

Merge and Recycle

Question 20

Large pieces of the membrane fold in to reform vesicles

Answer 20

bulk endocytosis

Question 21

A receptor protein that forms part of a ligand-gated ion channel, so that binding of ligand (e.g. a hormone or neurotransmitter) to the receptor causes opening of the channel, permitting ions to flow through it.
- Ionotropic receptors are not opened (or closed) all the time. They are generally closed until another small molecule (called a ligand — In our case, a neurotransmitter) binds to the receptor.
As soon as the ligand binds to the receptor, the receptor changes conformation (the protein that makes up the channel changes shape), and as they do so they create a small opening that is big enough for ions to travel through.
Therefore, ionotropic receptors are “ligand-gated transmembrane ion channels”.

Answer 21

Ionotropic Receptor

Question 22

do not have a “channel” that opens or closes. Instead, they are linked to another small chemical called a “G-protein.”
As soon as a ligand binds the metabotropic receptor, the receptor “activates” the G-Protein (it basically changes the G-Protein). Once activated, the G-protein itself goes on and activates another molecule. This new molecule is called a “secondary messenger.”

Answer 22

Metabotropic (G-coupled) receptors

Question 23

A neurotransmitter receptor located in the presynaptic terminal of the same neuron that produces the neurotransmitter. Autoreceptors have a higher affinity for the neurotransmitter than does the postsynaptic receptor, and thus have an autoregulatory function.

• Presynatpic receptors that are sensitive to the neurotransmitter released by the presynaptic terminal
  Typically G-protein-coupled receptors that stimulate second messenger formation
  Common effect is inhibition of NT release and in some cases, NT synthesis.
• safety valve to reduce release when [NT] is synaptic cleft gets too high.

Answer 23

Autoreceptor

Question 24

transient postsynaptic membrane depolarization by presynaptic release of neurotransmitter

Answer 24

Excitatory postsynaptic potential (ESPS)

Question 25

Transient hyperpolarization of postsynaptic membrane potential caused by presynaptic release of NT

Answer 25

Inhibitory postsynaptic potential (ISPS)

Question 26

mechanisms of NT removal

Answer 26

1) diffusion 2) enzymatic degradation 3) reuptake

Question 27

a type of passive transport, therefore, it is a net movement of molecules in and out of the cell across the cell membrane along a concentration gradient.

Answer 27

diffusion

Question 28

a specific enzyme changes the structure of the neurotransmitter so it is not recognized by the receptor. For example, acetylcholinesterase is the enzyme that breaks acetylcholine into choline and acetate.

Answer 28

enzymatic degradation

Question 29

the whole neurotransmitter molecule is taken back into the axon terminal that released it. This is a common way the action of norepinephrine, dopamine and serotonin is stopped...these neurotransmitters are removed from the synaptic cleft so they cannot bind to receptors.

Answer 29

reuptake

Question 30

increase or facilitate activity of the NT

Answer 30

agonist

Question 31

decrease or inhibit the activity of a NT

Answer 31

antagonist

Question 32

inhibits of neurotransmitter receptors

Answer 32

receptor antagonists

Question 33

bind and blocks nicotinic receptors, the ionotropic receptors at the neuromuscular junction causes paralysis

Answer 33

curare

Question 34

binds and blocks muscarinic receptors many of these metabotropic receptors are in the brain high doses disrupt memory

Answer 34

Atropine

Question 35

mimic actions of naturally occuring neurotransmitters at receptor

Answer 35

receptor agonist

Question 36

process by which multiple synaptic potentials combine within one postsynaptic neuron

Answer 36

synaptic integration

Question 37

elementary units of synaptic release

Answer 37

synaptic vesicles

Question 38

an indivisible unit | when NT are released, they are released in multiples based on this unit

Answer 38

Quantum - each quantum thought to = ~ 500 molecules from each vesicle

Question 39

mini

Answer 39

minature postsynaptic potential

Question 40

The size of the postsynaptic response to this spontaneously released NT can be measured electrophysiologically. The tiny response is called a ______. Each ____ is generated by the transmitter contents of one vesicle. The amplitude of the postsynaptic EPSP evoked by a presynaptic action potential is simply an integer muktiple of the mini amplitude - the results of stimulation of 2000 nitonic Ach channels

Answer 40

minature postsynaptic potential (mini)

Question 41

a method of comparing amplitudes of miniature and evoked postsynaptic potentials, can be used to determine number of vesicles that release during neurotransmission

Answer 41

Quantal analysis

Question 42

is a way of achieving an action potential in a neuron with input from multiple presynaptic cells. It is the algebraic summation of potentials from different areas of input, usually on the dendrites.

Answer 42

spatial summation

Question 43

Two (or more) distinct synaptic inputs onto the postsynaptic cell same time cell is depolarized

Answer 43

Spatial summation: Summation of EPSP

Question 44

Two (or more) independent inhibitory inputs | postsynaptic cell hyperpolarization

Answer 44

Spatial summation: Summation of IPSPS

Question 45

EPSP (depolarizing) and IPSP (hyperpolarizing) input not net change in membrane potential stronger input wins

Answer 45

Spatial summation: Summation of EPSP and IPSP

Question 46

single synapse initiating a sequence of membrane events.

Answer 46

Temporal summation

Question 47

the process of information transfer at a synapse

Answer 47

synaptic transmission

Question 48

special proteins that span narrow gap between two cells in a gap junction

Answer 48

connexin

Question 49

six connexins combine to form a challen called a

Answer 49

connexon

Question 50

two connexons (one from each cell) combine to form a

Answer 50

gap junction channel

Question 51

because electrical current (in the form of ions) can pass through these channels, cells connected by gap junctions are said to be

Answer 51

electrically coupled

Question 52

receptors known as ______ are membrane-spanning proteins consisting of four or five subunits that come together to form a pore between them. In the absence of NT, the pore is usually closed. When NT binds to specific sites on extracellular region of the channel, it induces a conformation change - just a slight twist of the subunits - which within microseconds causes the pore to open.

Answer 52

transmitter gated ion channels

Question 53

a transient postsynaptic membrane depolarization caused by the presynaptic release of neurotransmitter

Answer 53

excititory postsynaptic potential (EPSP)

Question 54

bring the membrane away from thresholf for generating action potentials

Answer 54

inhibitory

Question 55

a transient hyperpolarization of the postsynaptic membrane cause by presynatpic release of neurotransmitter

Answer 55

inhibitory postsynaptic potential (IPSP)

Question 56

G-protein coupled receptors

Answer 56

1) neurotransmitter molecules bind to receptor proteins embedded in the postsynaptic membrane 2) The receptor proteins activate small proteins called G-proteins that are free to move along the intracellular face of the postsynaptic membrane 3) the activated G-proteins activate "effector" proteins

Question 57

because G-protein-coupled receptors can trigger widespread metabolic effects, they are often refered to as ____

Answer 57

metabotropic repceptors

Question 58

despite continuous presence of NT, the NT-gated channels close

Answer 58

desensitization

Question 59

study of nervous system tissue

Answer 59

neuropharmacology

Question 60

inhibit the normal function of specific proteins involved in synaptic transmission

Answer 60

inhibitors

Question 61

inhibitors of neurotransmitter receptors | bind to the receptors and block (antagonize) the normal action of the NT

Answer 61

receptor antagonists

Question 62

mimic the actions of naturally occuring NT

Answer 62

receptor agonistst

Question 63

indivisible unit that reflects the number of transmitter molecules in a single synaptic vesicle and the number of postsynaptic receptors available at the synapse

Answer 63

quantum

Question 64

several stimuli control the opening/closing of ion channels

Answer 64

1) ligand gated 2) phosphorylation gated 3) voltage-gated 4) stretch (mechanical)

Question 65

ionotropic: direct gating

Answer 65

receptor is part of the channel protein 5 sub-units 4 membrane spanning a-helices - also called receptor channels or ligand gated channels

Question 66

steps of NT action on GPCRs

Answer 66

- bind receptor proteins - activate small proteins (g-protein) - activate "effector" proteins - directly gate channel - activate second messenger systems

Question 67

metabotropic: indirect gating

Answer 67

simplified steps: - activated GTP-binding proteins - second messenger cascade effects: may be to open/close phosphorlyation gated channel - typical receptor has single subunit - 7 a helices - binding regions is within the plane (pore) of the membrane

Question 68

ionotropic

Answer 68

fast actions relatively transient responses (msec) found: systems with rapid responses (reflex)

Question 69

metabotropic

Answer 69

- slower synaptic actions (sec-mins) alter excitability of neurons and strength of synaptic connections crucial for learning