PHYSIO_LE1 - (4) Synapse

Axodendritic synapse?

Axon to Post-synaptic dendrite

Axosomatic Synapse?

Axon to Postsynaptic Soma (body)

Axoaxonic synapse

presynaptic axon to post synaptic axon

Can Action Potentials flow through and occur in the Thick Myelin sheaths?

No, NO AXONS CAN FLOW THRU THICK MYELIN SHEATHS. AP CAN ONLY OCCUR AT NODES OF RANVIER

True or False? Electrical synapses have intercellular gaps to allow for instantaneous transmission hence faster communication

True

How many Connexons comprise 1 gap junction in an electrical synapse?

2

How many connnexins in 1 connexon in a Gap Junction?

6

What is the synapse?

Junction point from 1 neuron to the next. (Pre- and Post-synaptic synapse)

What characterizes a chemical synapse?

Use of a NEUROTRANSMITTER

What characterizes an Electrical Synapse?

the pre and post synapse are joined together by GAP JUNCTIONS

1 gap junction is made up of __ Connexons.

Each connexon is made up of __ Connexins

2 Connexons

6 Connexins

Which type of Synapse has:

• Smaller Intercellular Gap

• Doesnt involve Neurotransmitters

• Doesnt involve Post synaptic receptors

• Bi-directional

• Coordinated Response?

Electrical Synapse

Which type of synapse has:

• Large Intercellular gap

• Involves Neurotransmitters

• Involves Post-synaptic receptors

• Unidirectional only

• Amplified response

CHEMICAL synapse

T or F? The Sum of the

• Excitatory Postsynaptic Potential

• Inhibitory Postsynaptic potential

Determines whether or not there will be an action potential going through the neuron.

True!

Give 3 examples of Synaptic Transmitters.

1) Small-molecule (rapidly acting transmitters)

• e.g. Acetylcholine

• Mostly synthesized in the cytosol of the presynaptic terminal

2) Neuropeptides

3) Gaseous Molecules

Acetylcholine is synthesized in which terminal?

Presynaptic

Acetylcholine is synthesized from acetyl coenzyme A + Choline due to?

Choline acetyltransferase

After being split into Acetate and Choline in the Synaptic cleft by cholinesterase, ___ is actively transported back into the terminal for synthesis of acetylcholine.

Choline

Where can acetylcholine be secreted in?

• Large pyramidal cells from motor cortex

• Basal ganglia

• Skeletal motor neurons

• Autonomic nervous system (ANS)

Norepinephrine is secreted by Pre or post-ganglionic neurons of the sympathetic nervous system?

POSTsynaptic

which neurotransmitted helps control overall activty/mood/wakefulness?

Norepinephrine

T or F? Acetylcholine and Norepinephrine are both synthesized by the Autonomic Nervous System (ANS).

True

(BLANK) is secreted by neurons in the substantia nigra and is involved in the reward pathway

Dopamine

What is the primary inhibitory neurotransmitter in the adult CNS?

GABA

gama-aminobutyric acid

What is the excitatatory neurotransmitter of the nervous system?

glutamate!

What is an inhibitor of the pain-pathways of the spinal cord?

Serotonin

What controls a person’s mood and causes sleep?

Serotonin

T or F? SSRI (selective serotonon reuptake inhibitor) is given to px with depression so Serotoning does not get re-uptaken.

True.

Which neurotransmitters are synthesized in the cell body/perikaryon/soma ?

Neuropeptides

Fate of Neuropeptide vesicles?

They are AUTOLYZED and not reused.

Which neurotransmitters are released in much small quantities, BUT are more potent and have more prolonged actions.

Neuropeptides

Distinctions between Non-peptide transmitters vs Peptide transmitters.

Which one is Synthesized in Active Form?

Non-peptide transmitters

Peptide transmitters are synthesized and packaged in the?

Cell Body.

Non-peptide transmitters are synthesized in the?

Nerve Terminals

Which peptides have to be cleaved first from a much larger polypetide in order to be active?

Peptide transmitters

Which transmitters act quickly but have a shorter duration of effect?

Non-peptide transmitters

Where are vesicles and neurotransmitters created and packaged?

In the Endoplasmic Reticulum and packaged in the Golgi Apparatus.

Which neurotransmitter is responsible for long-term behaviour and memory?

Nitric oxide (NO)

What is the fastest neurotrasmitter produced?

Nitric Oxide.

T or F. Synaptic delay is the minimal amount of time required for thee transmissionn of a neuronal signal from the presynaptic neuron to a postsynaptic neuron.

True

1. Neurotransmitter molecules are packaged into membrane vesicles.

2. Pre-synaptic membrane depolarizes due to Action Potential

3. Depolariation causes Voltage-gated Ca2+ channels to open and allow Ca2+ to enter the terminal

4. The influx of Ca2+ ions leads to Vesicle docking and fusion with the Presynaptic membrane.

5. Neurotransmitters are released into the synaptic cleft.

6. Neurotransmitters bind to receptors on the post-synaptic membrane = post-synaptic event.

7. Trasmitter molecules are eventually cleared away via

   1. Diffusion

   2. Degradation

   3. Active Uptake

What are the relative components of a Vesicle?

• Vacuolar-type H pump

• neurotransmitter transport proteins

• SNARE proteins

• Synaptogamin

In a Vesicle, which component is responsible for catalyzing the movement of H+ into the vesicle using ATP?

Vacuolar-type H+ Pump

In a Vesicle, which component is responsible for mediating the exchange of neurotransmitters in the cytosol for H+ in the vesicle?

Neurotransmitter transport proteins

Which compenent is like a “rope/anchor” that docks the vesicle onto the membrane?

SNARE Proteins or SNA REceptor proteins

Vesicular Transport:

The Vesicular part of the SNARE protein =

The Membranous part of the SNARE protein is =

Vesicular Transport:

The Vesicular part of the SNARE protein (vSNARE)= Synaptobrevin

The Terminal membranous part of the SNARE protein (tSNARE)= Syntaxin & SNAP 25

What is Synaptogamin?

The calcium sensor on a vesicle for Exocytosis.

What does complexin do during vesicular transport?

It inserts into the SNARE complex to prevent spontaneous fusion

How is Complexin counterd? Or what causes complexin to stop preventing fusion of vesicle onto the membrane?

Ca2+ binds to Synaptogamin to displace Complexin.

When fusion is complete,

• Ca2+ is ___ from the cell.

• ____ disociates from the SNARE complex

• The SNARE complex is _____

• ____ undergoes recycling (endocytosed)

When fusion is complete,

• Ca2+ is extruded from the cell.

• Synaptotagmin dissociates from the SNARE complex

• The SNARE complex is degraded

• Synaptobrevin undergoes recycling (endocytosed)

The inactive G protein coupled receptors are composed of?

• GDP

• Alpha Subunit = Activator

• Beta Subunit

• Gamma Subunit

T or F. The INACTIVE Gprotein is bound to GDP

True

In G-Protein coupled receptors, When does the Gprotein bind to the receptor?

Once a neurotransmitter activates the receptor and exposes the binding site

After binding to the receptor, what happens to G protein complex?

It releases GDP so GTP can bind onto it.

The Alpha portion of the Gprotein separates from the Beta & Gamma portions.

After being separated, what can the Alpha -GTP complex perform?

1. Activate cAMP or cGMP in the neuronal cell

2. Activate one or more intracellular ennzymes

3. Activate gene transcription

4. Open Specific ion channels through the post synaptic cell membrane

T or F? Once inactivated due to GTP being hydrolyzed into GDP, the alpha subunit releases itself from the target protein and goes back to the Beta and Gamma subunit.

True

Excitatory postsynaptic receptors usually involve?

Opening of Sodium Channels

T or F? Excitatory postsynaptic receptors usually blocks Chloride and Potassium channels.

True

T or F? Inhibitory Postsynaptic Receptors allow the opening of chloride ion channels and INCREASE the efflux of potassium ions from the neuron.

True

Sodium wants to go?

INTRA

Potassium wants to go?

OUT

Is there higher Sodium Intracellularly or Extracellularly?

Extracellularly

PISO

Is there higher postassium Intracellularly or extracellulary?

Intracellularly

PISO

What is the resting membrane potential?

-65 mV

In the process of Summation, about _to_simultaneous dischages of excitatory postsynaptic potential is needed to INCREASE neuronal potential from -65mV to ___ mV

40 to 80

-65mV to -40mV

True or false? The Axon has has 7x LESSer voltage gated Na+ channels compared to the Soma

FALSE. 7x MORE than the Soma

EPSP increases the permeability of the membrane to ___ for 1-2 ms

Na+

IPSP inncreases the permeability of the membrane to ___and__ for 1-2 ms

K+ Cl-

Do postsynaptic potentials decay?

Yeah over time

(blank) summation is when the same neuron is activated on the same spot at different times and combined to produce an action potential.

Temporal Summation

(blank) summation is when a neuron is stimulated on different spots at the same time to produce an action potential.

Spatial summation

When a presynaptic axon is stimulated twice in rapid succession, it is often found that the postsynaptic potential generated by the ____ stimulus is LARGER in aptitude compared to the ___. This is often known as Facilitation.

Second Stimulus is LARGER in aptitude compared to the First stimulus.

In Post-Tetanic Potentiation, if there is low calcium, there is __ release of neurotransmitters.

Low calcium = low release of neurotransmitters.

What is the key mechanism that distinguishes post-tetanic potentiation (PTP) from facilitation?

A. PTP is a very short-lived effect, lasting only a few milliseconds, while facilitation lasts minutes.

B. PTP is caused by a greater and more sustained buildup of residual calcium in the presynaptic terminal.

C. PTP requires a single stimulus, while facilitation requires a high-frequency train of stimuli.

D. PTP involves postsynaptic changes, while facilitation is exclusively presynaptic.

B. PTP is caused by a greater and more sustained buildup of residual calcium in the presynaptic terminal.

What is the physiological basis for the short-lived nature of facilitation?

The rapid and efficient buffering and removal of residual Ca2+ from the presynaptic terminal.

In the context of synaptic plasticity, a tetanus refers to:

the specific, high-frequency stimulation used to induce phenomena like post-tetanic potentiation.

Facilitation and post-tetanic potentiation are both considered forms of short-term plasticity. What is the fundamental change at the synapse that they both cause?

A. An increased probability of neurotransmitter release from the presynaptic terminal.

B. An increase in the size of the postsynaptic terminal.

C. A decrease in the amount of neurotransmitter released.

D. A prolonged opening of postsynaptic ion channels.

A. An increased probability of neurotransmitter release from the presynaptic terminal.

Both phenomena are caused by an increase in residual calcium in the presynaptic terminal, which directly increases the likelihood that a subsequent action potential will trigger the release of more neurotransmitters.

(BLANK) is caused by a small, residual Ca2+ concentration that adds to the next pulse, while (BLANK) is caused by a large, prolonged buildup that saturates removal systems.

Facilitation is caused by a small, residual Ca2+ concentration that adds to the next pulse, while PTP is caused by a large, prolonged buildup that saturates removal systems.

The (BLANK) are targets for various botulinum toxins

SNARE proteins