Neurotransmitters Flashcards
The amino acid tyrosine is the precursor of dopamine, norepinephrine, and epinephrine. Tryptophan is the precursor of serotonin (5-hydroxytryptamine), and histamine derives from the amino acid histidine. Choline, an amino alcohol, is the precursor of acetylcholine, and the common amino acid glutamic acid is the precursor of the GABA. Note that DOPA decarboxylase is also known as aromatic L-amino acid decarboxylase, AADC.
Glycine is primarily found in inhibitory interneurons in the spinal cord, where it blocks impulses traveling down the cord in motor neurons to stimulate skeletal muscle. The glycine receptor on motor neurons is ionotropic and is blocked by strychnine; motor impulses can then be passed without negative control, which accounts for the rigidity and convulsions caused by this toxin.
Glycine
Norepinephrine, epinephrine, and dopamine (bio genic amines), known as catecholamines, are all derived from the amino acid ______
Tyrosine
Norepinephrine (also known as noradrenaline) is a major transmitter in the _______ nervous system
Sympathetic
Norepinephrine is the transmitter for these_________ nerves, whereas the transmitter at the intermediate ganglia is ACh.
Postganglionic
The stimulatory effects of ____________are caused by their close chemical similarity to catecholamines or biogenic amines
Amphetamines
The effects of neurotransmitters can be altered by changing their effective concentrations or the number of receptors. Concentrations can be altered by
■ changing the rate of synthesis,
■ altering the rate of release at the synapse,
■ blocking reuptake, or
■ blocking degradation.
__________ is the most important excitatory transmitter in the CNS
Glutamate
Epinephrine (also known as adrenaline) is produced by the __________ under the influence of ACh-containing nerves, analogous to the sympathetic preganglionic nerves
Adrenal medulla
The receptors for norepinephrine and epinephrine are called _______ They are divided into α- and β-receptor classes and subclasses on the basis of their pharmacology
adrenoceptors
Epinephrine acts on all classes of the receptors, but norepinephrine is more specific for _________
α-receptors
__________ is taken up into cells by a high-affinity transporter and catabolized by the enzyme monoamine oxidase (MAO). Further oxidation and methylation by catecholamine- O -methyltransferase (COMT) convert the products to metanephrines and vanillylmandelic acid
Norepinephrine
β-Blockers , such as atenolol, are used to treat hypertension and chest pain (angina) in ischemic heart disease because they antagonize the stimulatory effects of catecholamines on the heart
Nonspecific α-blockers have limited use
There are five known dopamine receptors, falling into two main groups ( D 1 -like : D 1 and D 5 ; and D 2 -like : D 2 , D 3 , and D 4 ) that differ in their signaling pathways. D 1 receptors increase the production of cAMP, whereas D 2 receptors inhibit it.
Antipsychotic drugs such as phenothiazines and haloperidol tend to inhibit D 2 -like receptors, suggesting that excessive dopamine activity may be important in causing the symptoms of schizophrenia.
The D 2 receptor is a major receptor in the nerves that interconnect the basal ganglia. Because it is known that destruction of these nerves causes Parkinson’s disease , it is not surprising that antipsychotic drugs that inhibit the D 2 receptor tend to have the side effect of causing abnormal movements.
The central role of serertoin 5-HT in
Controlling brain function
