Neuro Synaptic Transmission

Front 1

What happens to the neurotransmitter once it is exocytosed into the synaptic cleft?

Back 1

1. Neurotransmitter can DIFFUSE through the cleft and bind to specific receptors

2. NT can DIFFUSE out of the cleft and into the blood w/o touching receptors

3. NT can be METABOLIZED into something else (ACh->Choline +acetate)

4. NT can be pumped back into the axon terminal it was released from

Front 2

What is the term for Neurotransmitter diffusing through the cleft & into the blood w/o ever touching a receptor?

Back 2

Washout

Front 3

Where does Washout occur?

Back 3

In the PNS
(doesn't occur in the CNS b/c glia seal around the synapse)

Front 4

When Neurotransmitter is released into the synaptic cleft it can be METABOLIZED to a different structure, no longer an acceptable substrate for receptor binding. How is this accomplished?

Back 4

Acetylcholine is broken down in the presence of ACh Esterase, becoming Choline + Acetate

ACh + ACh Esterase -> Choline + acetate

Front 5

What is the term for a Neurotransmitter being pumped back into the axon terminal, thereby removing it from the cleft?

Back 5

Na+ Dependent High Affinity Reuptake

Front 6

What are the roles of presynaptic density?

Back 6

1. Hold the vesicles in place at the synapse

2. Prevent vesicles from fusing (and exocytosing) w/the cell membrane

Front 7

What keeps the pre- and post-synaptic densities aligned, making transmission more efficient?

Back 7

a Protein Matrix containing Actin & Synapsin

Front 8

What is the link between the action potential & exocytosis?

Back 8

Ca++ entry

Front 9

What are the specific channels found at synapses?

Back 9

N-type Ca++ Channels

Front 10

How are N-type Ca++ channels irreversibley blocked?

Back 10

The poison w-conotoxin irreversibley blocks N-type Ca++ channels

Front 11

What are the postsynaptic structures of note?

Back 11

1. Post synaptic density - is a protein structure that holds transmitter receptors

2. Transmitter receptors

3. Ion channels in the region of the synapse

Front 12

What phosphorylates Synapsin I?

Back 12

CAM Kinase II

Front 13

What happens when Synapsin I is phosphorylated?

Back 13

When phosphorylated, Synapsin I no longer tethers vesicles to actin, resulting in actin bundling together

Bottom line is it is now easier for vesicles to fuse w/membrane

Front 14

Ca++ also activates a membrane bound protein, which acts like what?

Back 14

membrane bound protein acts as a docking station for exocytosis

Front 15

How is Synapsin I inactivated?

Back 15

Phosphatases

Front 16

What type of voltage gated ion channels are found at synapses?

Back 16

N-type Ca++ channels

Front 17

What does w-conotoxin do?

Back 17

w-conotoxin irreversibly blocks N-type Ca++ channels

Front 18

What is significant about Ca++ channels closing?

Back 18

When Ca++ channels close they allow a squirt of Ca++ to Enter the neuron, which can produce a 1,000x increase in free Ca++ locally

Front 19

What is the decreased size of a generator potential in the presence of a constant stimulus referred to as?**

Back 19

Adaptation

Front 20

A mechanism for increasing the importance of a specific synaptic input is through the generation of a __________.

Back 20

Ligand gated Ca++ channel EPSP

Front 21

What is the period during which the potassium permeability is higher than at rest, yet the sodium permeability is the same as at rest?

Back 21

afterhyperpolarization (relative refractory period)

Front 22

What ion stabilizes the membrane and tends to increase threshold?

Back 22

Calcium

Front 23

Conduction of the action potential along an axon in the direction of the cell body is called ________ conduction

Back 23

antidromic

Front 24

The skipping of an action potential from Node to Node of Ranvier is called ________ conduction

Back 24

Saltatory conduction

Front 25

A synapse that occurs along the length of an axon (and not at a synaptic bouton) is called a _______ synapse

Back 25

Enpassant

Front 26

The protein that tethers synaptic vessicles to actin filaments is ___________

Back 26

Synapsin I

Front 27

What are the 4 components of the voltage gated potassium channel?

Back 27

1. activation gate (one gate only)

2. Selectivity filter

3. Conductance pore

4. Voltage sensor (inside protein)

Front 28

What are the components of the Blood-CSF Barrier?

Back 28

1. A basement membranes supporting the capillary

2. A pia mater layer

3. Choroidal endothelium w/tight junctions

4. Fenestrated capillary endothelium

(foot processes of astrocytes)

Front 29

Multiple Sclerosis is a demyelinating disease of the CNS. What would demyelination of neuron process would most likely lead to?

Back 29

A reduction in the velocity of nerve conduction

Front 30

The Basal Nuclei develop from neurotubular epithelium and are a portion of ________.

Back 30

Telecephalon

Front 31

What is the definition of the period of afterhyperpolarization?*

Back 31

1. The period when the potassium gate is open

2. Sodium activation gate is closed

3. Sodium inactivation gate is open

Front 32

The addition of X- (a partially permeable ion) to the extracellular fluid around a neuron should result in?

Back 32

Hyperpolarization of the neuron

Front 33

A patient w/degeneration of the pre motor cortex ("secondary motor cortex") in the left hemisphere will?

Back 33

Exhibit less discrete movements on the right side

Front 34

A person who says to you "Take the thing off the other thing and put it on the thing to the right of the thing" most likely has?

Back 34

Wernicke's aphasia (wrong nouns)

Front 35

What happens during synaptic transmission?

Back 35

Voltage-gated calcium channel opening allows for exocytosis of synaptic vesicles

Front 36

What happens to the potassium & sodium during the peak of the overshoot?**

Back 36

Potassium and sodium permeabilities are both higher than at rest

Front 37

What ion is the primary determinant of the resting membrane potential?

Back 37

Potassium

Front 38

What is likely to be true if a patient's CSF level of potassium is around 8 mM, rather than the normal 4.4 mM and has been rising steadily over the past four hours?

Back 38

The patient probably will have become hyperexitable and may subsequently become lethargic
The patient is at risk for developing a seizure
The patient is at risk to become comatose

Front 39

What are quanta?

Back 39

The contents of a single synaptic vesicle

Front 40

In the absence of an action potential we can see sporatic release of quanta, which would be expected with pre-docking, because intracellular free Ca++ isn't totally absent. What does the sporadic quantal release play a role in?

Back 40

Pre and Postsynaptic alignment. (denervation of a muscle cell results in receptors distributing broadly over the membrane)

Front 41

Can washout occur in the CNS?

Back 41

No because glia seal around the synapse, so it only occurs in the PNS

Front 42

What is washout?

Back 42

NT diffuse out of the cleft and eventually into the blood w/o ever touching a receptor

Front 43

What happens to the neurotransmitter once it is exocytosed into the synaptic cleft?

Back 43

1. NT diffuse through cleft and bind to specific receptors

2. NT can be washed out

3. NT can be metabolized

4. NT can be pumped back into the axon terminal via NA+ dependent High Affinity Reuptake

Front 44

What do MAOIs (Pargyline)do?

Back 44

MAOIs stimulate catecholamine transmission, by preventing MAOs from breaking down catecholamine; resulting in increased secretory vesicle storage

Front 45

How do neurotransmitters alter postsynaptic cell function?

Back 45

The neurotransmitter simply opens a ligand-gated ion channel

The effector is the ionophore (ion channel)

Front 46

T/F
The loading process is ATP dependent and involves pumping neurotransmitter from the cytosol into the vesicle

Back 46

True

Front 47

What does calcineurin do?

Back 47

inactivates the Ca++ channel

Front 48

What generates MEPPs?

Back 48

Miniature End Plate Potentials are generated by sporadic release of Quanta

Front 49

What does chloride especially affect?

Back 49

IPSP
creates a hyperpolarization
moves post-synaptic membrane potential away from threshold

Front 50

What is occuring when multiple PSPs are generating simultaneously at different locations on the post synaptic neuron?

Back 50

Spatial Summation of IPSPs & EPSPs

Front 51

What is happening when a 2nd PSP occurs at a time prior to complete decrement of preceding PSP?

Back 51

Temporal Summation of PSPs

Same one firing twice

Front 52

When an action potential spreads down an axon it is?

Back 52

Orthodromic

Front 53

When an action potential spreads toward the dendrites it is?

Back 53

Antidromic

Front 54

T/F
Soma and dendrites are myelinated

Back 54

False
They are UNmyelinated

Front 55

T/F
Bouton is an end to end synapse and En Passant is an end to axon synapse.

Back 55

True