Term
| The transmission of information at ??? involves the release of neurotransmitter from a presynaptic cell, diffusion across the synaptic cleft, and binding of the neurotransmitter to specific receptors on the postsynaptic membrane to produce a change in membrane potential. |
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Definition
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Term
o Synthesis: substance is synthesized in the neuron.
o Localization: It is present in the presynaptic terminal
o Release: the substance must be released by the presynaptic cell upon stimulation
o Mimicry: If the substance is applied exogenously to the postsynaptic membrane at physiological concentration, the response of the postsynaptic cell must mimic the in vivo response
o Inactivation: A specific mechanism exists for removing it from its site of action (e.g., synaptic cleft)
Criteria for establishing what molecule? |
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Definition
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Term
| What is the only neurotransmitter that is utilized at the neuromuscular juntion? |
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Definition
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Term
What causes most of the acute responses of nervous
system? For example, transmission of sensory signals to brain and motor signals back to the muscles. |
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Definition
| Small-molecule, Rapid Acting Transmitters |
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Term
What neurotransmitter has the following characteristics?
Large pyramidal cells of the motor cortex, neurons in the basal ganglia, and motor neurons innervating skeletal muscle
Has inhibitory effect on cardiac muscle (vagus nerve)
Transmitter in all preganglionic neurons and postganglionic neurons of parasympathetic nervous system
Transmitter in all preganglionic neurons of sympathetic neurons.
It is also the NT that is released from presynaptic neurons of the adrenal medulla
The NT that is utilized at the neuromuscular junction |
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Definition
| Acetylcholine (Cholinergic) |
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Term
What enzyme present in the postsynaptic membrane degrades ACh to choline & acetate
This degradation terminates the action of ACh at the postsynaptic membrane |
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Definition
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Term
| Epinephrine, Norepinephrine, and Dopamine (Biogenic Amines or Catecholamines) all share what common precursor? |
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Definition
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The chromaffin cells of the adrenal medulla contains the complete enzymatic pathway & secretes this neurotransmitter.In CNS, it is believed to play a role in regulation of BP
In the periphery, is the main circulating excitatory transmitter released during the “fight or flight” stress reactions |
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Definition
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Term
• Secreted by adrenergic neurons
• In the CNS, transmitter in Locus Coreleus has an inhibitory effect
• In the CNS, involved in alertness and wakefulness
• The primary transmitter for postganglionic sympathetic neurons with an excitatory influence.
• Released by internal organs, including gut, spleen, and heart. |
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Definition
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Term
| Dysfunction – Bipolar disorder & schizoprenia, regulation of mood, responsible for some symptoms of depression. This is caused by low levels of ??? |
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Definition
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Term
Dopaminergic neurons prominent in certain midbrain regions
Dysfunction – Degeneration of dopaminergic neurons in basal ganglia of substantia nigra occurs in Parkinson’s Disease
- Treatment is L-Dopa because dopamine cannot cross the BBB |
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Definition
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Term
Degradation of catecholamine (epinephrine & norepinephrine) to inactive substances occurs via two enzymes
o COMT (Catechol-O-methyltransferase)
A methylating enzyme NOT found in the nerve terminals, but it is distributed widely in other tissues, including the liver
o MAO (Monoamine Oxidase)
MAO is located in the presynaptic nerve terminals & catalyzes oxidative deamination. If a NT is degraded by MAO, there must be reuptake of the NT from the synapse
- Found in mitochondria
• Each of the biogenic amines can be degraded by MAO alone, COMT alone, or by both. |
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Definition
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Term
During reuptake, the uptake of NT is by facilitated diffusion.
o Na+ dependent secondary active transport
o Catecholamines can be either taken up into vesicles or broken down by COMT. If it is taken up into the vesicle, then it can be broken down by MAO |
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Definition
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Term
| Antihypertensive drug that acts as a tranquilizer (according to Stanfield) that serves to deplete stores of available stores of NE |
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Definition
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Term
| Prevents the reuptake of NE or Dopamine |
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Definition
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Term
MAO inhibitor that inhibits the breakdown of
catecholamines. This will build up the stores of
catecholamines & thus is an antihypertensive drug |
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Definition
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Term
Serotonin
Another biogenic amine that is produced from tryptophan in serotonergic neurons in the brain & GI tract
Following release, it can be inactivated by reuptake, or it may be degraded in the presynaptic terminal by MAO to 5-Hydroxytryptamine (5-HT)
Mostly inhibitory effects on postsynaptic membrane.
Involved in control of eating, sleep and arousal. (parasympathetic)
Clinical correlate
• Dysfunction – implicated in bipolar disorder, depression.
• Prozac – Antidepressant
o It is an SSRI (selective serotonin reuptake inhibitor)
o Allows more serotonin to stay in the cleft |
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Definition
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Term
o Glutamate – major excitatory amino acid transmitter in the CNS
Plays a significant role in the spinal cord & cerebellum
There are 4 types of glutamate receptors
• Three of the subtypes are ionotropic receptors, or ligand-gated ion channels, including the NMDA receptor that is widely distributed throughout the CNS
• A fourth subtype comprises the metabotropic receptors, which are coupled via GTP-binding proteins to ion channels
• Plays a role in learning and memory
• Can also be taken up by neighboring glial cells |
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Definition
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Term
| GABA and Glycine are ??? amino acid transmitters |
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Definition
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GABA
Gamma amino butyric acid has widespread distribution throughout brain and spinal cord.
Potent inhibitory transmitter necessary for stabilizing electrical activity
GABAa receptor – ligand-gated Cl channel – increases Cl influx to produce IPSPs
Benzodiazepines (e.g., librium) – anticonvulsants and sedatives. Facilitates action of GABA at GABAA (Barbiturates & alcohol)
GABAb receptor activation increases K conductance via activation of a G protein to produce IPSPs
GABA plays a role in learning and memory |
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Definition
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Term
Glycine
• Found in the spinal cord & brain
• Its mechanism of action increases Cl- conductance of postsynaptic cell membrane
• This hyperpolarizes the cell membrane
When glycine receptors are blocked, you experience continuous contraction would occur (lock-jaw). |
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Definition
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Term
Large-Molecule, Slowly Acting Transmitters
o Cause more prolonged actions
o Example – long-term changes in numbers of receptors, long-term opening or closure of certain ion channels
o Neuropeptides act at very low concentrations to excite or inhibit neurons. Neuropeptides may act as hormones, as neurotransmitters, or neuromodulators.
- Neuromodulators
• Substances that act on the presynaptic cell to alter the amount of NT released in response to stimulation
• Alternatively, a neuromodulator may be cosecreted with a NT & alter the response of the postsynaptic cell to the NT
- Neurohormones
• Released from secretory cells into the blood to act at a distant site
Most peptides serve as neuromodulators, but some act as neurotransmitters. |
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Definition
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Term
Synthesized in the neuronal cell body, packaged in secretory vesicles and transported to the tips of nerve fibers by axonal streaming of axon cytoplasm.
Smaller amounts of ??? are released compared to “classical’ transmitters but much more potent causing more prolonged actions. |
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Definition
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Term
| The neurotransmitter does not determine what happens at the postsynaptic membrane, rather the type of receptor that is occupied by the transmitter determines the final event. Many transmitters act on several receptor subtypes and each has its own unique effect. Some presynaptic membranes possess receptors that are used to modify the release of transmitter. |
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Definition
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Term
NONPEPTIDE TRANSMITTERS
Synthesized and packaged in nerve terminal
Synthesized in active form
Present in small, clear vesicles
Released into a synaptic cleft
Action terminated by uptake by presynaptic terminal by Na+ powered active transport
Typically, action has short latency and short duration |
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Definition
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Term
| Substances that act on the presynaptic cell to alter the amount of neurotransmitter released in response to stimulation . Alternatively, may be consecreted with a neurotransmitter and alter the response of the postsynaptic cell to the neurotransmitter |
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Definition
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Term
Regulation of pain information
beta-endorphin |
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Definition
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Term
PEPTIDE TRANSMITTERS
Synthesized and packaged in cell body; transported to nerve terminal by fast axonal transport
Active peptide formed when it is cleaved from a much larger polypeptide that contains several neuropeptides
Present in large, electron-dense vesicles
May be release some distance from the postsynaptic cell
There may be no well-defined synaptic structure
Action terminated by proteolysis or by the peptide diffusing away
Action may have long latency and may persist for may seconds |
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Definition
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