Page 457 - Fundamentals of anatomy physiology

444 Unit 3 Control and Regulation

Table 12–4 Representative Neurotransmitters and Neuromodulators

Class and Mechanism Location(s) Comments
Neurotransmitter Chemical Structure of Action Widespread in CNS and PNS; best
known and most studied of the
Acetylcholine CH3 O Primarily direct, through CNS: Synapses throughout brain and neurotransmitters
binding to chemically spinal cord
CH3 N+ CH2 CH2 O C CH3 gated channels PNS: Neuromuscular junctions; Involved in attention and
preganglionic synapses of ANS; consciousness, control of body
CH3 neuroglandular junctions of temperature, and regulation of
parasympathetic division and (rarely) pituitary gland secretion
Biogenic Amines OH Indirect: G proteins and sympathetic division of ANS; amacrine Uncertain functions
Norepinephrine second messengers cells of retina
NH2 CH2 CH
OH CNS: Cerebral cortex, hypothalamus,
OH brain stem, cerebellum, spinal cord
PNS: Most neuromuscular and
Epinephrine OH Indirect: G proteins and neuroglandular junctions of
OH second messengers sympathetic division of ANS
CH2 NH CH2 CH CNS: Thalamus, hypothalamus,
midbrain, spinal cord

OH

Dopamine OH Indirect: G proteins and CNS: Hypothalamus, midbrain, limbic Regulation of subconscious
OH second messengers system, cerebral cortex, retina motor function; receptor
Serotonin NH2 CH2 CH2 Primarily indirect: G CNS: Hypothalamus, limbic system, abnormalities have been linked
proteins and cerebellum, spinal cord, retina to development of
12 Histamine second messengers CNS: Neurons in hypothalamus, with schizophrenia
Indirect: G proteins and axons projecting throughout the Important in emotional states,
Amino Acids OH second messengers brain moods, and body temperature;
Excitatory: several illegal hallucinogenic
NH2 CH2 CH2 drugs, such as Ecstasy, target
Glutamate serotonin receptors
N Receptors are primarily on
Aspartate presynaptic membranes;
N functions in sexual arousal, pain
Inhibitory: N threshold, pituitary hormone
Gamma- NH2 CH2 CH2 secretion, thirst, and blood
aminobutyric pressure control
acid (GABA)
O O Indirect: G proteins and CNS: Cerebral cortex and brain stem Important in memory and
Glycine C CH CH2 CH2 C second messengers CNS: Cerebral cortex, retina, and learning; most important
Direct: opens calcium/ spinal cord excitatory neurotransmitter
HO NH2 OH sodium channels on pre- in the brain
and postsynaptic
O CH CH2 O membranes Used by pyramidal cells in the
NH2 C Direct or indirect brain that provide voluntary
C (G proteins), depending motor control over skeletal
HO OH on type of receptor muscles
Direct effects: open Cl– channels;
O Direct or indirect CNS: Cerebral cortex, cerebellum, indirect effects: open K+ channels
(G proteins), depending on interneurons throughout brain and and block entry of Ca2+
NH2 CH2 CH2 CH2 C type of receptor spinal cord
OH

O Direct: Opens Cl– channels CNS: Interneurons in brain stem, Produces postsynaptic inhibition;
spinal cord, and retina the poison strychnine produces
NH2 CH2 C fatal convulsions by blocking
OH glycine receptors

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