Chapter 3: Chemical Signalling by Neurotransmitters and Hormones
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Vak
PSYC 450 (PSYC450)
Instelling
Athabasca University (AU
)
Chapter 3 delves into the intricate mechanisms of chemical signalling by neurotransmitters and hormones within the nervous system. It begins with the basic concepts of synaptic transmission, highlighting the directionality from presynaptic to postsynaptic cells and the structural components of syna...
Unit 3: Chemical Signaling by Neurotransmitters and Hormones
Chemical Signaling in the Nervous System
Basic concepts
- Synapse was coined in 1897 by Charles Sherrington to describe the mechanism underlying
neuronal communication
- Transmission occurs in only one direction from presynaptic to postsynaptic cells
- The most common synapses in the brain are axodendritic synapses
- Axosomatic synapses are synapses between a nerve terminal and a nerve cell body
- Synaptic clefts contain numerous proteins that help organize and maintain the structure of the
synapse
- Mitochondria are cellular organelles responsible for energy production and are needed in
large quantities in the terminals for various functions
- Glial cells play an important role in regulating transmission by amino acid transmitters
- Other synapses involve processes from astrocytes, which are necessary for ion pumping and
transmitter release.
Neurotransmitter synthesis, release, and inactivation
- The nervous system contains thousands of chemical substances, making it important for
neuroscientists to determine which ones function as neurotransmitters.
- Criteria must be met to determine if a substance is a neurotransmitter, including presence of
presynaptic and postsynaptic cells, mechanism for manufacturing and inactivating the
substance, and release from the axon terminal.
- Receptors for the proposed substance should be present on the neurotransmitter and an
agonist or antagonist drug should inhibit both the action of the substance and the e ect of
stimulation.
Neurotransmitters encompass several di erent kinds of chemical substances
- Most neurotransmitters fall into several chemical classes
- Amino acids serve numerous functions besides neurotransmitter activity
- Monoamines such as dopamine, norepinephrine, and serotonin are important transmitters
- Acetylcholine serves key functions at the neuromuscular junction, in the autonomic nervous
system, and in the brain
- Neuropeptides, such as endorphins and enkephalins, play a role in neuropsychiatric illness
and drug treatment
- Orexin plays major roles in feeding behavior, reward-seeking behaviors, and arousal and
sleep.
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Neuropeptides are synthesized by a di erent mechanism than other transmitters
- Neuromitters are synthesized through enzymatic reactions in the cell.
- Neuropeptides are di erent from small-molecule transmitters and cannot be replenished
until large vesicles have been transported.
Neuromodulators are chemicals that do not act like typical neurotransmitters
- Neuromodulators are substances that do not act exactly like typical neurotransmitters
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