Topic 4-Neurotransmitters Flashcards
Where do neurotransmitters act?
Neurotransmitters act at synapses in the synaptic cleft.
How do neurotransmitters affect target cells?
They have direct, rapid effects on specific target cells.
How quickly do the effects of neurotransmitters typically occur?
The effects of neurotransmitters usually occur quickly, within milliseconds to seconds, and are usually short-lived.
Where do neuromodulators act in relation to the synaptic cleft?
Neuromodulators act at a distance from the synaptic cleft.
How do neuromodulators influence cells?
They are released into the extracellular fluid, affecting many cells.
What is a notable characteristic of the effects of neuromodulators?
The effects of neuromodulators manifest slowly, over seconds, and typically last longer, ranging from minutes to days.
Criteria for classification as a NT: 3
1) Located in presynaptic region (usually in vesicles).
2) Released with activation or depolarization of the presynaptic terminal (Ca 2+ dependent).
3)Specific receptors must be present on the postsynaptic cell.
Two Types of NT
1)Small-molecule neurotransmitters (amino acids, acetylcholine, purines and biogenic amines)
2) Neuropeptides
Example of Excitatory NT:
1) Glutmate (main fasting acting NT in the CNS)
2) Aspartate
Example of Inhibitory NT
1) GABA (major inhibotry) 2) Glycine
Small molecule neurotransmitters can act as both
fast-acting neurotransmitters and neuromodulators.
Examples of small molecule NT
- Dopamine: Reward
Norepinephrine: Alertness
Epinephrine: Stress
Serotonin: Mood
Histamine: Wakefulness
Where is acetylcholine (ACh) primarily found in the nervous system?
ACh is a major conveyer of information in the peripheral nervous system (PNS).
What are the two main receptor subtypes for acetylcholine (ACh)?
ACh has two main receptor subtypes: nicotinic and muscarinic.
What is the role of acetylcholine (ACh) in the central nervous system (CNS)?
In the CNS, ACh is slower-acting and involved in neuromodulation, particularly in movement control and the selection of objects of attention.
How do nicotinic and muscarinic receptors differ in their action?
Nicotinic receptors are fast-acting, as seen at the neuromuscular junction, while muscarinic receptors are slower-acting, G-protein-coupled receptors. Muscarinic receptors are also found in the CNS.
What are the two purines mentioned in neurotransmission?
The two purines are ATP (adenosine triphosphate) and adenosine
What is the role of ATP in neurotransmission?
ATP serves as an excitatory neurotransmitter and is coreleased with other neurotransmitters.
Is adenosine considered a classical neurotransmitter, and why?
Adenosine is not considered a classical neurotransmitter because it is not stored in vesicles. It is generated from ATP by extracellular enzymes or released in a calcium-dependent manner.
How can neuropeptides affect neurosignaling?
Neuropeptides can affect neurosignaling by acting as hormones, neurotransmitters, or neuromodulators.
What type of receptors do slow, modulatory neurotransmitters typically act on?
Slow, modulatory neurotransmitters often act on metabotropic receptors. Examples include biogenic amines, ACh (acting on muscarinic receptors), and neuropeptides.
Typical Effects of NT: 3
1)Fast Excitatory
2) Fast Inhibitory
3)Slow Modulatory
What are examples of neurotransmitters that have fast inhibitory effects and act on ionotropic receptors?
Examples include GABA and glycine (in the spinal cord
What are examples of neurotransmitters that have fast excitatory effects and act on ionotropic receptors in the peripheral nervous system (PNS) and central nervous system (CNS)?
Examples include ACh (acting on nicotinic receptors) in the PNS and glutamate in the CN
Where are ] Where are small molecule neurotransmitters and larger peptide neurotransmitters typically synthesized?
Small molecule neurotransmitters are synthesized in the nerve terminal.
Larger peptide neurotransmitters are typically synthesized in the soma (cell body) of the neuron.
Life Cycle of a NT Steps
1) NT is synthesized in cell body or terminal
2) NT is packaged into vesicles
3) NT is released when vesicles fuse
4) NT binds to and activates post synaptic receptors
5) NT diffuses away and is metabolized and/or trasnported back into the terminal
Which direction does neuronal transport occur in and what is the purpose?
-Occurs in both direction
- Allows for the delivery of organelles and macromolecules from the cell body to the axon terminal.
Where does the synthesis of neuropeptides, neurotransmitter precursors, and enzymes typically take place?
The synthesis of neuropeptides, neurotransmitter precursors, and enzymes usually occurs in the cell body (soma) of the neuron and is packaged in the Golgi apparatus. These substances are then transported down microtubules to their destinations, such as the axon terminal.
NT Production
1,2 - Enzymes for NT synthesis produced in soma & released from Golgi apparatus
3 - Slow axonal transport to presynaptic terminal
4 – NT substrates transported into terminal and assembled using enzymes from soma
5,6 - Packaged in vesicles (5) for release (6)
What triggers the link between the membrane and vesicular docking proteins during neurotransmitter release?
The influx of calcium ions (Ca2+) triggers the link between the membrane and vesicular docking proteins.
What is the role of the fusion pore in neurotransmitter release?
The formation of the fusion pore allows neurotransmitters (NT) to be released from the nerve terminal into the synaptic cleft, where they can bind to receptors on the postsynaptic neuron and facilitate neurotransmission.
What happens to the vesicle membrane after neurotransmitter release into the synaptic cleft?
The vesicle membrane is recycled through a process called endocytosis.
Why is the recycling of neurotransmitter precursors important?
The recycling of neurotransmitter precursors ensures a continuous supply of neurotransmitters to refill the vesicles, allowing for sustained neurotransmission.
Why is it important to remove neurotransmitters from the synaptic cleft quickly?
To avoid making the receiving cell less responsive to future signals and to protect it from potential harm, i
What are the three main methods of neurotransmitter removal from the synaptic cleft?
Neurotransmitters are removed through these methods:
1) Reuptake into neighboring astrocytes (e.g., glutamate).
2) Reuptake into the presynaptic terminal (e.g., dopamine and norepinephrine).
3) Enzymatic breakdown in the synaptic cleft (e.g., acetylcholine).
How do most drugs exert their effects in the nervous system?
Most drugs work by either mimicking or blocking the action of neurotransmitters or neuromodulators.
What are some ways in which drugs can affect neurotransmitters?
Drugs can influence neurotransmitters by increasing or decreasing their synthesis, altering their release, or affecting receptor binding on the postsynaptic membrane.
What is Lambert-Eaton syndrome, and how does it affect transmission at the neuromuscular junction?
Involves antibodies targeting calcium channels, resulting in muscle weakness and affecting neurotransmission at the neuromuscular junction
What is Parkinson’s Disease, and what is its primary cause?
Parkinson’s Disease involves the death of neurons that produce dopamine in the substantia nigra.
What is Alzheimer’s disease characterized by?
Alzheimer’s disease is characterized by disruptions in the normal function of cholinergic neurons.
