Chapter 3: Synaptic transmission Flashcards
Which events in the presynaptic neuron trigger neurotransmitter release?
The release of neurotransmitters from the presynaptic neuron is triggered by the arrival of an action potential at the presynaptic terminal.
What is an ionotropic receptor?
- ion channels that open in response to the binding of neurotransmitters.
- when a neurotransmitter binds to an ionotropic receptor, it causes a conformational change in the receptor protein, which leads to the opening or closing of an ion channel in the receptor.
- the effects of neurotransmitters on ionotropic receptors are typically short-lived.
What are metabotropic receptors
- receptors that activate intracellular signaling pathways when neurotransmitters bind to them.
- when a neurotransmitter binds to a metabotropic receptor, it activates a G protein associated with the receptor, and leads to the opening or closing of ion channels
- The effects of neurotransmitters on metabotropic receptors are typically slower and longer-lasting than the effects on ionotropic receptors, and they can have more widespread effects on the cell and even on other nearby cells.
What happens after the release of neurotransmitters into the synaptic cleft?
they can be removed from the cleft by two main mechanisms: reuptake by transporter proteins and degradation by enzymes.
What is reuptake?
the process by which neurotransmitters are taken up from the synaptic cleft back into the presynaptic neuron.
Once inside the presynaptic neuron, the neurotransmitter can be either recycled for future use or degraded by enzymes.
What is degradation?
the process by which enzymes in the synaptic cleft break down neurotransmitters into inactive metabolites.
What is the typical effect of GABA?
GABA is the primary inhibitory neurotransmitter in the brain.
When GABA is released from a presynaptic neuron and binds to GABA receptors on the postsynaptic neuron, it causes an influx of negatively charged chloride ions into the cell, leading to hyperpolarization of the postsynaptic membrane and a decrease in the likelihood of action potentials being generated.
In other words, GABA inhibits neural activity, and it is essential for maintaining the balance between excitatory and inhibitory signaling in the brain.
What is the typical effect of glutamate?
Glutamate is the primary excitatory neurotransmitter in the brain.
When glutamate is released from a presynaptic neuron and binds to glutamate receptors on the postsynaptic neuron, it causes an influx of positively charged ions, such as sodium and calcium, into the cell, leading to depolarization of the postsynaptic membrane and an increased likelihood of action potentials being generated.
In other words, glutamate excites neural activity and is essential for processes such as learning, memory, and motor control.
However, excessive glutamate release can also lead to neuronal damage and cell death, as is seen in conditions such as stroke and traumatic brain injury.
What are diffuse modulator neurotransmitters?
a class of neurotransmitters that are released by a group of neurons that project widely throughout the brain and can affect the activity of many other neurons.
Unlike classical neurotransmitters, which act rapidly and locally at synapses, neuromodulators act more slowly and more globally, modulating the activity of large populations of neurons.
Neuromodulators can alter the way in which classical neurotransmitters function, as well as influence various other aspects of neural signaling, such as synaptic plasticity, gene expression, and metabolic activity.
What are examples of neuromodulators?
1) Serotonin: is a neuromodulator that is involved in regulating mood, appetite, and sleep, among other functions. Serotonin is synthesized in the raphe nuclei of the brainstem and is released widely throughout the brain.
2) Norepinephrine: is a neuromodulator that is involved in regulating arousal, attention, and mood. Norepinephrine is synthesized in the locus coeruleus of the brainstem and is released widely throughout the brain.
3) Acetylcholine: is a neuromodulator that is involved in regulating attention, memory, and motor control. Acetylcholine is synthesized in the basal forebrain and is released widely throughout the brain.
4) Dopamine: is a neuromodulator that is involved in regulating reward, motivation, and movement. Dopamine is synthesized in the substantia nigra and the ventral tegmental area of the midbrain and is released widely throughout the brain.
What are agonists?
Agonists are drugs that can interact with receptors in the nervous system.
binds to receptors and activates them, mimicking the effects of the neurotransmitter that would normally bind to that receptor.
Agonists can increase the activity of the receptor and amplify the normal signaling pathways that are activated by the neurotransmitter.
Some agonists can be used to treat medical conditions by enhancing the effects of natural neurotransmitters, such as opioid agonists used to relieve pain or nicotine agonists used to aid in smoking cessation.
What are antagonists?
Antagonists, on the other hand, are drugs that bind to receptors and block their activation by the neurotransmitter.
Antagonists can prevent the neurotransmitter from binding to the receptor and inhibit the normal signaling pathways that are activated by the neurotransmitter.
Some antagonists can be used to treat medical conditions by reducing the effects of natural neurotransmitters, such as antipsychotic medications that block dopamine receptors to treat schizophrenia.
