E3 Synapses Flashcards
What are the types of synaptic vesicles?
small, clear synaptic vesicles
small vesicles with a dense core
large vesicles with a dense core
What does the small, clear synaptic vesicles contain?
Acetylcholine
Glycine
GABA
Glutamate
What does the small vesicles with a dense core contain ?
Catecholamines
What does the large vesicles with a dense core contain?
Neuropeptides
What does an influx of calcium activate?
- Synaptotagmin
- partially assembled SNARE complex
What is synaptotagmin?
Calcium sensor
What targets SNAREs?
Bacterial neurotoxins responsible for botulism and tetanus
What does the synaptic terminal of the chemical synapse release?
Neurotransmitters
What do the neurotransmitters bind to?
postsynaptic membrane
What does the chemical synapse produce?
Temporary, localized change in permeability or function of postsynaptic
What does the chemical synapse changes affect?
Affect cell, depending on nature and number of stimulated receptors
How fast are the neurotransmitter responses?
Rapid
What are neurotransmitters linked to?
Ion channel signaling
What are neuromodulators linked to?
G proteins
How fast are neuromodulators?
Slower than neurotransmitters
What do neuromodulators do?
Alter synaptic effectiveness/strength
What kind of potentials are postsynaptic potentials?
Graded potentials developed in a postsynaptic cell
How are graded potentials generated in postsynaptic cell?
Response to neurotransmitters
What are the types of postsynaptic potentials?
excitatory and inhibitory
What are excitatory postsynaptic potentials (EPSP)?
Graded depolarization of postsynaptic membrane
What are inhibitory postsynaptic potentials (IPSP)?
Graded hyperpolarization of postsynaptic membrane
What is effected by a neurotransmitter?
Postsynaptic membrane
What does the effect of a neurotransmitter depend on?
Depends on receptor, not neurotransmitter
Example of neurotransmitter that effects postsynaptic membrane?
Acetylcholine
What does Acetylcholine promote?
Action potentials
What does Acetylcholine inhibit?
Cardiac neuromuscular junctions
What are the known or presumed neurotransmitters or neuromodulators?
- Acetylcholine
- Biogenic amines
- Amino acids
- Neuropeptides
- Miscellaneous
what are the biogenic amines?
Catecholamine
Serotonin (5-HT)
Histamine
What are examples of catecholamines?
Dopamine (DA)
Norepinephrine (NE)
Epinephrine (Epi)
What are examples of neuropeptides?
endogenous opioids
oxytocin
tachykinins
What is part of the miscellaneous neurotransmitters or neuromodulators?
Gases (NO)
Purines (adenosine and ATP)
What is synaptic plasticity?
the ability of synapses to strengthen or weaken over time
What does synaptic plasticity change?
increases or decreases in their activity
What does synaptic plasticity result from?
alteration of the number of neurotransmitter receptors located on a synapse
What is synaptic plasticity responsible for?
upregulation and downregulation
What are the mechanisms that cooperate to achieve synaptic plasticity?
- Changes in quantity of neurotransmitters released
- Changes in how effectively cells respond to neurotransmitters
What does the synaptic plasticity of both excitatory and inhibitory synapses depend on?
postsynaptic calcium release
What are the presynaptic factors to determine the synaptic strength?
- Availability of neurotransmitters
- Axon terminal membrane potential
- Axon terminal calcium
- Activation of membrane receptors on presynaptic terminal
- Certain drugs and diseases, which act via the above mechanisms
What is also associated with the availability of neurotransmitter factor?
- availability of precursor molecules
- amount or activity of the rate limiting enzymes in the pathway for neurotransmitter synthesis
What are the different types of membrane receptors on the presynaptic terminal?
- Axo-axonic synapses
- Autoreceptors
- Other receptors
What are autoreceptors?
When active, reduce further release of neurotransmitters
What are the postsynaptic factors to determine the synaptic strength?
- Immediate past history of electrical state of postsynaptic membrane
- Effects of other neurotransmitters/neuromodulators acting on postsynaptic neuron
- Up/down regulation and desensitization of receptors
- Certain drugs and diseases
What is an example of immediate past history of electrical state of postsynaptic membrane?
Excitation/inhibition from temporal or spatial summation
T/F Distinctions between neurotransmitters and neuromodulators are not always clear
true
How long are the actions of the neuromodulators/neuropeptides?
prolonged actions
What do neuromodulators/neuropeptides do during these prolonged actions?
- Long term changes in number of neural receptors
- Long term opening/closing of certain ion channels
- Changes in number and sizes of synapses
What part of the brain deals with neuron plasticity?
Hippocampus
What are the types of synaptic transmitters?
- small-molecule, rapidly acting transmitters
- neuropeptides, slowly acting transmitters or growth factors
- miscellaneous
What are the class 1 small-molecule, rapidly acting transmitters?
acetylcholine
What are the class 2 small-molecule, rapidly acting transmitters?
Biogenic amines
What are the class 3 small-molecule, rapidly acting transmitters?
Amino acids
What are the class 4 small-molecule, rapidly acting transmitters?
Dissolved gases
What are the neuropeptides, slowly acting transmitters or growth factors?
- Hypothalamic-releasing hormones
- Pituitary peptides
- Peptides that act on gut and brain
- From other tissues
- Purines
- Lipids
What is part of the miscellaneous category of the synaptic transmitters?
Purines
What are the 2 types of amino acids that act as neurotransmitters?
Excitatory
Inhibitory
What are the excitatory neurotransmitters?
Glutamate
Aspartate
What are the inhibitory neurotransmitters?
- GABA (gamma-aminobutyric)
- Glycine
What are the dissolved gasses of class 4 neurotransmitters?
- Nitric oxide
- Carbon monoxide
What are the hypothalamic releasing hormones?
- Thyrotropic releasing hormone
- Somatostatin
- Luteinizing hormone releasing hormone
What does somatostatin target?
anterior pituitary and GI tract
What are luteinizing releasing hormones?
Ovulation and corpus luteum
What are the pituitary peptides?
- ACTH (Adrenocorticotropic hormone)
- Melanocyte stimulating hormone
- Prolactin
- Vasopressin
- Oxytocin
What is vasopressin?
antidiuretic hormone (ADH)
- retains water
What is oxytocin?
plays a role in social bonding, sexual reproduction, childbirth, and the period after childbirth
What are the purines that act as neuropeptides?
- ATP, GTP
- Adenosine
What are the lipids that act as neuropeptides?
Anandamide
What are anandamides derived from?
metabolism of arachidonic acid
What system would you find anandamides?
endogenous cannabinoid system
What neuropeptides act on the gut and brain?
- Substance P
- Opioids (endogenous)
- Gastrin
- Nerve growth factor
- Neuropeptide Y
- Neurotensin
- Insulin
- Glucagon
What are the opioids that act on the gut and brain?
- Enkephalins
- Endorphins
- Dynorphin
What is substance P?
pain
- free nerve endings
What is a ionotropic receptor?
form from an ion channel pore
What is a metabotropic receptor?
indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms, often G proteins
What is inherently metabotropic?
G protein-coupled receptors (GPCRs)
What do neurotransmitters and neuromodulators have a direct effect on?
Membrane ion channels
What are the direct effects on the membrane ion channels?
Ionotropic effect
Ex. acetylcholine, glycine, aspartate
What do neurotransmitters and neuromodulators have an indirect effect on?
- via G proteins
- via intracellular receptors and enzymes
What are the indirect effects via G proteins?
Metabotropic or Ionotropic
Ex. Epinephrine, norepinephrine, dopamine, histamine, GABA
What are the examples of the indirect effects via intracellular receptors and enzymes?
Lipid-soluble gases (NO, CO)