3 - Neurotransmitters Flashcards
More than __ neurotransmitter chemicals have been identified
100
The synaptic cleft, is about __ __
20 nm
The synapse is surrounded by processes (fibers) from __ (__ __)
Astrocytes | Glial Cells
Two kinds of Autoreceptors
Terminal Autoreceptors: activated by the neurotransmitter; inhibit further transmitter release.
Somatodendritic Autoreceptors: on cell bodies or dendrites, slow the rate of neuron firing, which reduces the rate of transmitter release
*Some drugs block or stimulate autoreceptors
One axon synapses on the terminal of another axon.
- Permits the presynaptic cell to alter neurotransmitter release from the postsynaptic cell directly at the terminals
- Reduced transmitter release from the terminal: presynaptic inhibition.
- Enhanced release of transmitter: presynaptic facilitation
Axoaxonic Synapses
A presynaptic axon terminal communicates with a dendrite of the postsynaptic cell
Axodendritic Synapse
Most neurotransmitters are made in the __ __. Enzymes for their synthesis are transferred there.
Axon Terminals
An Axon Terminal synapses on the body of a nerve cell
Axosomatic Synapses
Classical Neurotransmitters (4)
- those studied first
- can be synthesized anywhere in the cell
- follow the neurotransmitter criteria
- acetylcholine
- amino acids
- monoamines
- purines
Small vesicles contain __ __ only
Classical transmitter(s)
Large vesicles may contain __ and __ transmitters
Classical | Neuropeptide
__ and __ readily pass through membranes and can’t be stored in __ __. They must be made on demand and simply diffuse out through the cell membrane. Once in __ __, they may travel to other cells nearby
Lipid & Gaseous Transmitters | Synaptic Vesicles | Extracellular Fluid
Numerous __ in the axon provide ATP for __ __ and __ __.
Mitochondria | Ion pumping | Transmitter release
Synapse between a neuron and a muscle cell
Neuromuscular Junction
Synapse receiving cell may be another neuron, a muscle cell, or a cell specialized as a __/__ __
Neuron | Muscle Cell | Hormone/Secretory Cell
Replenishment of __ is slower than for small molecules because precursors are shipped from the cell body to axon terminals in large vesicles
Neuropeptides
A chemical substance packaged in synaptic vesicles and released by a neuron to communicate across a synapse (with another neuron, muscle cell, organ, or a hormone-producing cell in an endocrine gland)
Neurotransmitter
Neurotransmitter Criteria
- Presynaptic cell contains the chemical and a mechanism to make it
- Lipids and Gases are retrograde messengers
- Mechanism for inactivating the chemical present
- Chemical is released from axon terminal when neuron is stimulated
- Receptors for chemical are present on postsynaptic cell
- Direct application of chemical or agonist has same effect on post-synaptic cell as stimulating the presynaptic neuron
- Applying an antagonist that blocks receptors inhibits both the chemical’s action and effect of stimulating the presynaptic neuron
Proteins located on cell membranes to which a transmitter binds to activate it. Result may be exitatory or inhibitory.
Neurotransmitter Receptors
Non-Classical Neurotransmitters (3)
- gases
- lipids
- neuropeptides
Vessicles do not transport the other __ __
Nonclassical Neurotransmitters
Individual neurons can make from __ to __ neurotransmitters
One | Several
Transmission occurs in one direction from __ __ to the __ __
Presynaptic Cell | Postsynaptic Cell
Neuropeptides are made from __ __
Protein Precursors
Some psychoactive drugs block transporters, and signal transmission is enhanced
- Cocaine blocks transporters for DA, 5-HT, and NE.
- Many antidepressants block 5-HT transporter, NE transporter, or both.
Lipid and Gaseous Transmitters typically released by the postsynaptic rather than the presynaptic cell
Retrograde Messengers
__ __ in the axon terminals are filled with several thousand molecules of a neurotransmitter
Synaptic Vesicles
