Principles of Neurotransmitters

How are neurons classified?

1. Structure 

2. Function

   1. Action 

   2. Connectivity

1. What are the structural classifications?

1. Unipolar or pseudounipolar

2. Bipolar

3. Multipolar

1. Describe a unipolar or pseudounipolar neuron?

1. Dendrite and axon emerging from the same process

1. Describe a bipolar neuron

1. Single axon and single dendrite on opposite ends of the some

1. Describe a multipolar neuron

1. More than two dendrites

   1. Golgi I

   2. Golgi II

What does it mean for a multipolar neuron to be golgi I?

1. Neurons with long-projecting axonal processes

What does it mean for a multipolar neuron to be golgi II?

Neurons whose axonal process projects locally

What are the different types of neurons?

1. General structure of neuron

2. Pyramidal cells

3. Basket cells

4. Double bouquet cells

5. Spiny neuron

6. Purkinje cell

7. Chandelier neuron

1. What are the different neurons when grouped by functional action classification?

1. Excitatory Neurons

2. Inhibitory Neurons

3. Modulatory Neurons

1. What neurons would best fit in the Excitatory neurons when classified under action as functional classification?

1. Glutamatergic

2. Acetylcholine

1. What neurons would best fit in the Inhibitory neurons when classified under action as functional classification?

1. GABA

2. Glycine

What neurons would best fit in the Modulatory neurons when classified under action as functional classification?

1. Dopamine

2. Serotonin

1. What are the different neurons when grouped under functional connectivity classification?

1. Afferent neurons

2. Efferent neurons

3. Interneurons

Describe Afferent neurons grouped under functional connectivity classification?

1. Convey information from tissues and organs into the central nervous system

2. Convey information from one region of the brain to another

1. Describe Efferent neurons grouped under functional connectivity classification?

1. Transmit signals from the central nervous system to the effector cells and are sometimes called motor neurons

2. Transmit signals from one region of the brain another

Describe Interneurons grouped under functional connectivity classification?

1. Connect neurons within specific regions of the central nervous system

Where does protein synthesis occur?

1. In the soma (primarily)

2. In the dendrites

Which is the limiting factor to neuron development?

1. Slow antegrade transport

In which direction does slow anterograde transport occur?

1. Only anterograde

1. Which direction does fast transport occur?

1. Anterograde and retrograde

   1. Anterograde is 2x faster than retrograde

      1. Retrograde is 2x slower than anterograde

1. Why is Fast antegrade transport needed?

1. To transmit signal to make and stop protein production

1. What are the types of glial cells

1. Microglia

2. Macroglia

   1. Oligodendrocytes and Schwann cells

   2. Astrocytes

1. Which glial cell is tiny and technically not part of the brain?

1. Microglia

1. What are the two macroglia?

1. Oligodendrocytes and Schwann cells

2. Astrocytes

1. Where are oligodendrocytes located?

CNS

1. Where are schwann cells located?

PNS

1. What are the functions of astrocytes?

1. Support, structure, and insulation

2. Removing debris

3. Promote efficient signaling

   1. Produce chemicals that neurons need for function

   2. Reuptake of neurotransmitters

4. Control the chemical composition of the fluid surrounding neurons

5. Sometimes regulate the properties of the presynaptic terminal (nerve-muscle synapse)

6. Guide migrating neurons (development) and axonal growth

7. Release growth factors

8. Providing nourishment to neurons

1. What do astrocytes not do?

1. Conduct action potentials

1. How are neurons nourished?

1. Through blood vessels which provide oxygen and nutrition

   1. Microscopic openings that have tight junctions to not allow viruses in

   2. Astrocyte supports tight junctions and gets sugar from blood through glycolysis

Typical capillaries are more open while brain capillaries are more restrictive to things that enter

1. What is the charge of the outside of the cell?

1. +

1. What is the charge of the inside of the cell?

1. -

1. What is the force of diffusion electrostatic pressure?

The attractive force between atomic particles charged with opposite signs or repulsive force between atomic particles charged with the same charge

1. What are the effects of electrostatic pressure and diffusion for K+?

1. Diffusion causes K+ to leave the cell

2. Electrostatic pressure causes K+ to enter the cell

What are the effects of electrostatic pressure and diffusion for Cl-?

1. Diffusion causes Cl- to enter the cell

2. Electrostatic pressure causes Cl- to leave the cell

1. What are the effects of electrostatic pressure and diffusion for Na+?

1. Diffusion and electrostatic pressure cause Na+ to enter the cell

1. Is the concentration of Cl- higher inside or outside the cell?

1. Outside

1. Is the concentration of Na+ higher inside or outside the cell?

1. Outside

1. Is the concentration of K+ higher inside or outside the cell?

1. inside

1. How does communication occur within a neuron?

1. Depolarization

2. Hyperpolarization

3. Cable properties

1. Describe depolarization communication within a neuron?

1. Reduction (toward zero) of the membrane potential of a cell from its normal resting potential

   1. Inside become positive

Describe the hyperpolarization communication within a neuron?

1. An increase in the membrane potential of a cell, relative to the normal resting potential

   1. More negative

2. Propagates using cable properties

   1. Fast and efficient

1. Describe cable properties communication within a neuron?

1. The passive conduction of electrical current, in a decremental fashion, down the length of an axon.

2. Decays with distance

1. What kind of mechanism is an action potential?

1. Active

1. Describe threshold of excitation.

1. The value of the membrane potential that must be reached to produce an action potential

1. Describe an action potential

1. All or none

2. The brief electrical impulses that provide the basis for conduction of information along an axon

1. What are the membrane proteins on the neuron?

1. Ion channel

2. Voltage-dependent ion channel

1. Describe the ion channel

A specialized protein molecule that permits specific ions to enter or leave cells

1. Describe the voltage-gated ion channel

1. An ion channel that opens or closes according to the value of the membrane potential

1. Are the voltage-dependent and ligand-gated ion channel mutually exclusive?

No

1. What are the steps of the occurrence of an action potential?

1. Signal reaches the threshold of excitation

2. Na+ channels open, Na+ begins to enter cell

3. K+ channels open, K+ begins to leave cell

4. Na+ channels become refractory, no more Na+ enters cell

5. K+ continues to leave cell, causes membrane potential to return to resting level

6. K+ channels close, Na+ channels reset

7. Extra K+ channels outside diffuses away

1. What are the two channels involved in the action potential?

1. K+

   1. Voltage gated dependent channel 

   2. K+ channel is delayed to open

2. Na+

   1. Voltage dependent

   2. Inactivation

      1. Timer, moment pass voltage, closes after certain time not matter threshold

1. Describe the sodium-potassium transporter.

1. A protein found in the membrane of all cells that extrudes sodium ions from and transports potassium ions into the cell

2. Requires a lot of energy 

3. Constantly pumping 3 Na+ out and 2 K+ in

   1. To make sure inside is negative and Na+ doesn’t accumulate

1. Describe the all or none law for the action potential 

1. The principle that once an action potential is triggered in an axon, it is propagated, without decrement, to the end of the fiber

1. How does an action potential move fast?

1. A larger diameter 

2. Insolation

   1. Myelin

1. What is saltatory conduction?

1. Conduction of action potentials by myelinated axons. The action potential appears to jump from one node of Ranvier to the next

1. Where is the action potential regenerated?

1. Node of Ranvier

1. How can intensity of an action potential be measured?

1. Frequency (Rate Law)

2. # of neurons in a population activated or types of neurons activated

1. What is the Rate Law?

1. The principle that variations in the in the intensity of a stimulus or other information being transmitted in an axon are represented by variations in the rate at which that axon fires

1. What is the presynaptic membrane?

1. The membrane of a terminal button that lies adjacent to the postsynaptic membrane and through which the neurotransmitter is released

1. What is the postsynaptic membrane?

1. The cell membrane opposite the terminal button in a synapse; the membrane of the cell that receives the message

1. What is the synaptic cleft?

1. The space between the presynaptic membrane and the postsynaptic membrane

1. What is the synaptic vesicle?

1. A small, hollow, beadlike structure found in terminal buttons, contains molecules of a transmitter

What are the different types of synapse connections?

1. Axon and dendrite 

2. Axon and dendritic spine

3. Soma and axon

4. Axon and axon

1. What are the different neurotransmitters?

1. Acetylcholine

2. The monoamines

   1. Serotonin

   2. Dopamine

   3. Norepinephrin

3. Glutamate

4. GABA

5. Histamine

6. Peptides

7. Lipids

8. Nucleosides

9. Soluble Gases

1. What was the 1st neurotransmitter identified?

1. Acetylcholine

1. What are the classical neurotransmitters?

1. Acetylcholine

2. The monoamines

3. Glutamate

4. GABA

5. Histamine

What is classified as an almost classical neurotransmitter?

1. Peptides

1. Why is the peptide considered an almost classical neurotransmitter as compared to classical neurotransmitter?

1. Made in the soma

2. Can be made in the terminal 

3. Can be replenished longer

1. What is a classical neurotransmitter?

1. Made in the synapse

   1. Enzyme made in soma

2. Packed into vesicles and in multiple vesicles

1. Which are not classical neurotransmitters?

1. Lipids

2. Nucleosides

3. Soluble Gases

1. Why are lipids and gases not considered classical neurotransmitters?

1. Retrograde NT

2. Not packed into vesicles

3. Not released by presynaptic cell 

   1. Released by the post-synaptic cell and travel to presynaptic

      1. De Novo

1. Why are non classical neurotransmitters considered de novo?

1. Molecules like endocannabinoids (e.g., anandamide) or gasotransmitters (e.g., nitric oxide) cannot be safely stored in vesicles because they easily pass right through lipid membranes. Because the cell cannot store them or recycle them from the synapse, it must manufacture them fresh from raw molecular components (like membrane lipids or amino acids) the exact moment a surge of calcium triggers their production.

1. What is the release zone?

1. A region of the interior of the presynaptic membrane of a synapse to which synaptic vesicles attach and release their neurotransmitter into the synaptic cleft

1. What are some retrograde neurotransmitters?

1. Nitric oxide (NO)

2. Nerve growth factor (NGF)

1. What are the three dimensions of neurotransmission?

1. Space

2. Time

3. Function

1. Describe space as a dimension of neurotransmission?

1. Anatomically address nervous system

   1. The concept that the brain is a series of hard-wired connections between neurons, not unlike millions of telephone wires within thousands and thousands of cables.

      1. Brain development

      2. Connections

      3. Biochemical

2. Chemically address nervous system

   1. Known as volume transmission

1. In order to chemically address the nervous system what do you need?

1. Proximity

2. Right receptor

1. Describe time as a dimension of neurotransmission?

1. Fast-onset

2. Slow-onset

   1. Can last minutes 

   2. Maintains changes

      1. Can exhaust neuron

1. Compare Glutamate and GABA’s time dimension of neurotransmission.

1. Glutamate (neuron A) is fast in onset and excitatory (+)

2. GABA (neuron C) is fast on onset and inhibitory (-)

1. What is the time dimension of neurotransmission for the neurotransmitter that follows glutamate and GABA signalling?

1. Monoamines and neuropeptides tend to be slow on onset (neuron B) and either excitatory (+) or inhibitory (-). 

1. What are slower-onset neurotransmitters that are long-acting called?

1. Neuromodulators 

   1. Modulate a different signal from other neurotransmitter

1. What occurs if the slow signal from B (monoamines and neuropeptides) is still present when a fast signal from A or C arrives?

1. The B signal will modulate the A or C signal 

   1. A long acting neuromodulating signal of neuron B can set the tone of the postsynaptic neuron, not only by primary action of its own but also by modifying the action of neurons A and C

1. Where are some locations of modulation?

1. Dendrites

   1. Dendritic spines

2. Cell body

3. Axon terminal

What connection between presynaptic terminal and postsynaptic sites are easiest to change?

1. It is easiest to change at the axon terminals 

2. However it is a little less easier to change at the dendrites 

3. And hardest to change at the cell body

1. Describe function as a dimension of neurotransmission.

1. Presynaptic 

2. Postsynaptic

1. Where do receptors exist?

1. Presynaptic

2. Postsynaptic

1. Where is the effector system?

1. Presynaptic

2. Post synaptic

1. Where does the neuron get the energy for the presynaptic neuron to send its axon terminal to form a synapse with a postsynaptic neuron?

1. Provided by the mitochondria in the presynaptic neuron

1. What is considered the first messenger involved in the effector system?

1. Neurotransmitter released from the presynaptic neuron

What causes an effector system to manufacture a second messenger?

1. First messenger bind to its receptor and the bound receptor causes it

1. Where is the second messenger involved in the effector system?

1. Inside the cell of the postsynaptic neuron

   1. It is this second messenger that then goes on to create cellular actions and biological effects

1. Are receptors and effector systems sitting in the presynaptic or postsynaptic portion?

1. Both 

1. What are the steps to neurodevelopment?

1. Stem cell

2. Neurogenesis

3. Selection

   1. Elimination

4. Migration

5. Differentiation

6. Synaptogenesis (presynaptic; axonal growth & connections)

7. Synaptogenesis (postsynaptic; dendritic arborization)

1. When is the start and end of neurogenesis?

1. 4 weeks - Birth

When is the start and end of neuronal selection?

1. 8 weeks - birth

1. When is the start and end of migration from the ventricular zone?

1. 8 weeks - birth

1. When is the start and end of differentiation and myelination?

1. 12 weeks - birth

1. When is the start and end of synaptogenesis?

1. 20 weeks - birth

1. When is the start and end of competitive elimination?

4 months - 60+

1. When does adult neurogenesis not occur in the hippocampus?

1. During depression