Unit 1_Neural Communication Part 2 Flashcards
What are the following steps associated with?
- Transmitter is synthesized and then stored in vesicles.
- An action potential invades the presynaptic terminal.
- Depolarization of presynaptic terminal causes opening of voltage-gated Ca (2+) channels.
- Influx of Ca (2+) through channels.
- CA (2+) causes vesicles to fuse with presynaptic membrane.
- Transmitter is released into synaptic cleft via exocytosis.
- Transmitter binds to receptor molecules in postsynaptic membrane.
- Opening or closing of postsynaptic channels.
- Postsynaptic current causes excitatory or inhibatory postsynaptic potential that changes the excitability of the postsynaptic cell.
- Removal of neurotransmitter by glial uptake or enzymatic degradation.
- Retrieval of vesicular membrane from plasma membrane.
Sequence of events involved in transmission at a typical chemical synapse
What are two types of neurotransmitter receptors?
Ionotropic receptors - direct gathering (Ligand-gated ion channels)
Metabolic receptors - indirect gating (G-protein-coupled receptors)
What type of neurotransmitter receptor includes the following steps:
- Neurotransmitter binds
- Channel opens
- Ions flow across membrane
Ionotropic receptors - direct gathering (Ligand-gated ion channels)
What type of neurotransmitter receptor includes the following steps:
- Neurotransmitter binds
- G-protein is activated
- G-protein subunits or intracellular messengers modulate ion channels
- Ion channel opens
- Ions flow across membrane
Metabolic receptors - indirect gating (G-protein-coupled receptors)
What type of neuron are molecules, lipids, or ions that distribute an external signal (= the “message”) as they are released into the cytosol (= in the cell) upon receptor activation? They affect a wide variety of intracellular enzymes, ion channels, transporters, growth factors, and changes in gene expression (= the process by which information from ageneis used to produce anotherprotein) that are ultimately responsible for the proliferation (= increase in number), differentiation (= becoming more specific), and maturation of nerve cells.
Calcium (Ca2+) and cyclic adenosine monophosphate (cAMP) are examples.
Second Messengers
What is a cellular protein that binds to DNA and regulates the process by which information from a gene is used by the cell to create new proteins? Different signaling pathways in the cell can “activate”.
When it’s “activated” long enough, the genetic information in a strand of DNA is copied (= transcription) into a new molecule of messenger RNA (mRNA). Thereby, DNA safely and stably stores genetic material in the nuclei of cells as a reference or template for new protein synthesis. These are required for lasting structural changes.
cAMP response element binding protein (CREB)
What is released during stress and interacts with glutamatergic synaptic function and can interfere with synaptic plasticity? This can be beneficial with moderate stress but leads to dysfunction when stress becomes chronic. (i.e., learning)
Glucocorticoids (cortisol)
What includes structural (= physical) changes following (short-lived) functional changes, specifically, sustained activity at metabotropic receptors and the activation of the protein synthesis cascade involving second messengers?
The cAMP pathways is among the best understood second-messenger signaling pathways.
Synaptic plasticity
What are released during states of motivation and attention, boost synaptic plasticity?
Dopamine and ACh
What is released during chronic stress, depresses synaptic plasticity?
Cortisol
What can impact neurotransmitter function and long-term synaptic changes?
Pathology or Neurotoxins (drugs)
How can Pathology or Neurotoxins (drugs) impact neurotransmitter function and long-term synaptic changes?
- Blocking neurotransmitter release
- Blocking neurotransmitter sites
- Drug agonists
- Blocking neurotransmitter reuptake or metabolism
What is a deadly condition that results from exposure to the spores produced by the bacteria Clostridium botulinum? Toxic spores can be found in the soil, contaminated foods, or water. The toxin itself is one of the most potent agents known to man - exposure to concentrations as low as 2ng/kg is lethal. The most common symptoms include muscle weakness or paralysis, especially the muscles of the face or the limbs. For about 5% of people who develop this disease, death results from paralysis due to respiratory failure.
It’s known to selectively cleave the proteins that comprise the SNARE complex. There are a few specific types of this toxin with slightly different intracellular targets, but the result is the same on the molecular level: prevention of vesicular fusion eliminating neurotransmitter signals.
Despite being one of the deadliest toxins so far identified, millions of people pay to have a preparation of toxin called “Botox” injected into their face. For most, the injection of botox is a cosmetic procedure that can reduce the appearance of wrinkles by paralyzing the muscles. This toxin is also used medically for conditions resulting from excessive neurotransmitter release, such as muscle spasms, excessive sweating, or migraine.
Botulism
What are linked to numerous neuropsychiatric disorders, such as depression (serotonin), anxiety disorders (serotonin), and neurodevelopmental disorders such as autism, attention deficit hyperactivity disorder, or schizophrenia (dopamine, serotonin, GABA)?
Impairments in neurotransmitter production and receptor function
Nicotine
MDMA/ecstasy
Benzodiazepines
THC/cannabis
What are two examples of stimulants?
Nicotine
MDMA/ecstasy
What are two examples of sedatives?
Benzodiazepines
THC/cannabis
Which of the following neurotransmitters is primarily inhibitory?
GABA
Glutamate
Seratonin
Dopamine
GABA
Which of the following is an example of a second messenger involved in long-term synaptic changes?
Na+
ATP
cAMP (cyclic AMP)
K+
cAMP (cyclic AMP)
Which of the following occurs in response to Ca2+ (calcium ions) entering pre-synaptic terminal?
Removal of neurotransmitter
Exocytosis
Endocytosis
Action potential
Exocytosis
Which of the following best describes the impact of glucocorticoids (cortisol) on long-term synaptic changes?
It binds to Ca2+ recptors
It is inhibitory
It interacts with glutamate’s synaptic functions
It causes neuronal death
It interacts with glutamate’s synaptic functions
When does communication occur?
Between two excitable cells
At chemical synapses, all current injected into the presynaptic cell escapes into the extracellular fluid.
However, the resulting depolarization of the presynaptic cell membrane can produce an action potential that causes the release of what that bind receptors on the postsynaptic cell?
This binding opens ion channels that initiate a change in membrane potential in the postsynaptic cell.
Neurotransmitter molecules
Synaptic vesicles release transmitters by what? This process of transmitter release is very tightly regulated.
Calcium (Ca2+) influx triggers molecular processes that facilitate the vesicle fusion with the presynaptic cell membrane. This protein complex in the active zone brings key elements near this area that enable vesicles to dock, prime, and fuse rapidly in response to the action potential–triggered Ca2+ entry into the presynaptic cell near the docked vesicle.
Exocytosis
After exocytosis, the synaptic vesicle membrane is retrieved by a fast process called what?
Endocytosis
What kind of synapses are typically located at specialized dendritic projections, called spines, and less commonly at the shafts of dendrites?
Excitatory synapses
What kind of synapses are usually located at the cell body (axosomatic), dendritic shaft (axodendritic), axon initial segment (axoaxonic), and presynaptic terminals of another neuron?
Inhibitory synapses
What occurs when different inhibitory neurons target different regions of a postsynaptic cell?
Selective targeting
What is important because the location of inhibitory inputs in relation to excitatory synapses is critical in determining the effectiveness of inhibition?
Selective targeting
What is more effective when initiated at the cell body or near the axon trigger zone?
Inhibition
What can inhibit or facilitate transmitter release by the presynaptic cell?
Axoaxonic synapses
What can elicit postsynaptic excitation (+) or inhibition (-), depending on the nature of the receptors and ion channels activated by the transmitter?
The same transmitter
What force does Glutamate elicit?
postsynaptic excitation
What force does GABA and Glycine elicit?
inhibition
What force does Dopamine and Serotonin elicit?
postsynaptic excitation or inhibition
Nearly all excitatory neurons in the CNS are what?
It is estimated that more than half of all brain synapses release this neurotransmitter.
Glutamatergic
What is the main inhibitory neurotransmitter in the brain?
Only about 25% of neurons in the brain are this (but inhibition and excitation is well balanced).
GABA
What determines whether the postsynaptic effect is excitatory or inhibitory?
The balance between activity at glutamatergic and GABAergic synapses
