Neurophys L3: SYNAPTIC TRANSMISSION AND AP

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Questions and Answers

What is the primary direction of transmission in chemical synapses?

Reverse

Bidirectional

Unidirectional (correct)

Lateral

What is the role of Ca in the release of neurotransmitters?

It is necessary for the synthesis of neurotransmitters

It inhibits the release of neurotransmitters

It is not involved in the release of neurotransmitters

It triggers the release of neurotransmitters from vesicles (correct)

What is a characteristic of unconventional neurotransmitters?

They are stored in vesicles

They can carry signals backward (correct)

They always bind to receptors on the postsynaptic cell

They are not involved in signaling

What is the function of GABA in the nervous system?

It is an inhibitory neurotransmitter Signup and view all the answers

What is the main difference between small molecule and large molecule neurotransmitters?

Their size and composition Signup and view all the answers

What is the function of Substance P in the nervous system?

It carries pain signals Signup and view all the answers

What is the role of receptors in conventional neurotransmission?

They bind to neurotransmitters and trigger a response Signup and view all the answers

What is a characteristic of endorphins and encephalins?

They inhibit pain signals Signup and view all the answers

What is the effect of Neuropeptide Y on food intake?

It increases food intake Signup and view all the answers

What is the main difference between excitatory and inhibitory neurotransmitters?

Their function in the nervous system Signup and view all the answers

What is the primary function of dendrites in neurons?

To integrate incoming information and determine action potential production Signup and view all the answers

What is the term for the small membranous protrusions found on dendrites?

Dendritic spines Signup and view all the answers

What is the direction of axonal transport related to synaptic components?

Anterograde Signup and view all the answers

What is the purpose of retrograde transport in neurons?

To recycle membrane and transport cargo for degradation Signup and view all the answers

What is the longest possible length of an axon?

Over 10 meters Signup and view all the answers

What is the site of axonal protein synthesis?

The soma Signup and view all the answers

What is the role of the cytoskeleton in axonal transport?

To work with different proteins to transport multiple cargoes Signup and view all the answers

What type of molecules are endocannabinoids?

Lipid-based neurotransmitters Signup and view all the answers

What is the term for the process by which neurons communicate with each other?

Synaptic transmission Signup and view all the answers

What is the result of an enriched or stimulatory environment on dendrites?

Dendritic growth Signup and view all the answers

What is the function of the cAMP pathway in metabotropic receptors?

Activate one or more intracellular enzymes Signup and view all the answers

What is the function of lysosomes in axons?

To degrade and recycle cellular waste Signup and view all the answers

What is the effect of excitatory neurotransmitters on cation channels?

Induce depolarization Signup and view all the answers

Which of the following is NOT a gasotransmitter?

Anandamide (AEA) Signup and view all the answers

What is the role of nitric oxide in the body?

Signaling to smooth muscle in blood vessels Signup and view all the answers

What is the difference between ionotropic and metabotropic receptors?

Ionotropic receptors directly gate ion channels, while metabotropic receptors act through second messenger systems Signup and view all the answers

What is the function of CB1 and CB2 receptors?

Binding to endocannabinoids Signup and view all the answers

What is the effect of inhibitory neurotransmitters on anion channels?

Induce hyperpolarization Signup and view all the answers

Which of the following is an example of a physiological process regulated by the endocannabinoid system?

Pain sensation Signup and view all the answers

What is the mechanism of action of G protein-coupled receptors?

Activating the cAMP pathway Signup and view all the answers

What is the function of gap junctions?

To allow free movement of ions from the interior of one cell to the interior of the next cell Signup and view all the answers

What is the typical resting potential of a neuron?

-60 to -70 millivolts Signup and view all the answers

What is the purpose of the trigger zone in a neuron?

To generate action potentials Signup and view all the answers

What is the term for the minimal voltage change required to trigger an action potential?

Threshold potential Signup and view all the answers

What is the function of excitatory neurotransmitters?

To open cation channels Signup and view all the answers

What is the term for the type of synapse where the electrical signal passes by to the axon terminal?

En passant synapses Signup and view all the answers

What is the term for the process of summing up graded potentials from different synapses?

Spatial summation Signup and view all the answers

What is the term for the type of synapse where the neurotransmitter opens anion channels?

Inhibitory synapses Signup and view all the answers

What is the term for the speed of conduction of action potentials in neurons?

Conduction velocity Signup and view all the answers

What is the term for the nodes of Ranvier in myelinated fibers?

Nodes of Ranvier Signup and view all the answers

Study Notes

Neurons and Synapses

Neurons are the core components of the brain, spinal cord, and nerves.
Dendrites integrate incoming information and determine whether action potentials will be produced by the neuron.
Dendritic branching patterns can change and may increase or decrease in response to environmental stimuli.

Axons

Axons can be only a few micrometers or over 10 meters long, depending on the species and location.
Axons contain the majority of the cell cytoplasm and several organelles, including neurofibrils, neurotubules, small vesicles, lysosomes, mitochondria, and enzymes.
Axonal proteins are synthesized in the soma and transported to the axon through anterograde transport.

Synaptic Transmission

Chemical synapses are the most common form of synapses, usually involving unidirectional transmission.
The presynaptic neuron secretes a neurotransmitter that acts on receptor proteins in the postsynaptic neuron.
Neurotransmitters can be either excitatory or inhibitory.

Neurotransmitters

There are two main types of neurotransmitters: conventional and unconventional.
Conventional neurotransmitters share basic features, are stored in vesicles, and released in response to action potentials.
Examples of conventional neurotransmitters include:
- Small molecule neurotransmitters (e.g., amino acids, amines, purines)
- Large molecule neurotransmitters (e.g., endorphins, substance P, neuropeptide Y)
Unconventional neurotransmitters do not follow traditional rules and can carry signals backward or act directly on molecules inside the cell.
Examples of unconventional neurotransmitters include:
- Endocannabinoids (e.g., anandamide, 2-arachinonyl-glycerol)
- Gasotransmitters (e.g., nitric oxide, carbon monoxide, hydrogen sulfide)

Receptors

Ionotropic receptors directly gate ion channels, while metabotropic receptors act through second messenger systems.
Examples of ionotropic receptors include nicotinic acetylcholine receptors.
Examples of metabotropic receptors include G-protein-coupled receptors.

Electrical Synapses

Electrical synapses involve direct connection of the cytoplasm of adjacent cells through gap junctions.
They allow for free movement of ions between cells and are bidirectional.
Electrical synapses can coexist and interact with chemical synapses, promoting synchronous firing of interconnected neurons.

Graded Potentials

Graded potentials are brief local changes in postsynaptic membrane potentials generated in response to neurotransmitters.
Their amplitude is directly proportional to the intensity of the stimulus applied at synaptic sites.
Graded potentials can be either excitatory or inhibitory.

Integration of Graded Potentials

The axon hillock integrates graded potentials by algebraic processing, adding or subtracting potential changes.
The sum of all graded potentials must stay under the threshold for an action potential to occur.
There are two modes of summation: spatial and temporal summation.

Action Potentials

Action potentials are generated at the trigger zone and propagate without losing strength due to the "domino effect".
The speed of conduction depends on axon diameter and the degree of myelinization.
In myelinated fibers, action potentials occur only at the Nodes of Ranvier, "jumping" from node to node.

Saltatory Conduction

Saltatory conduction is the process of action potentials "jumping" from node to node in myelinated fibers.
The impulse is transmitted from node to node, and the action potential is regenerated at each node.

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