Post on 03-Apr-2018
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Neurotransmitter (NTs)
Department of PhysiologySchool of Medicine
University of Sumatera Utara
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Introduction:
The Nervous System is incrediblycomplex and contains manyimportant chemical messengerscalled neurotransmitters
Neurotransmitters are aminoacid based molecules thatrelay signals between majorsystems of the body.
Neurotransmitters define ourmoods, actions, and health
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Introduction:
The importance of themtranscends their role in thebrain. They act as messengersbetween the: immune,endocrine, digestive, and
nervous system. They are present throughout
the body and required forproper brain and bodyfunctions. The brain uses
neurotransmitters to tell yourheart to beat, your lungs tobreathe, and your stomach todigest
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Introduction:
Neurotransmitters are also
necessary for memory and
thinking, feeling, sleeping,
and your energy. Scientific literature has
established the link
between neurotransmitter
imbalances and clinicalsymptoms
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Some symptoms of NeurotransmitterImbalance
Stress, anxiety, mood swings, depression,irritability, agitation, apathy, panic attacks,difficulty concentrating, developmentaldelays, attention issues, memory decline,
sleep disturbances, headaches, weightissues, food (carbohydrate) cravings,fatigue, addiction, decreased sex drive,hormonal imbalance & PMS, digestive
troubles, autism, and immune systemproblems
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Neurotransmitter Imbalance
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The synthesis of neurotransmitters
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The synthesis of neurotransmitters
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Functional Classification of
Neurotransmitters (NTs)A. Based on effects
excitatorycause depolarization (glutamate)
inhibitorycause hyperpolarization (GABA)
effect of some depends on postsynapticmembrane receptors ACh and NE have different receptor typessome
that cause excitation and other types that causesinhibition
B. Based on mechanism of action direct (channel-linked receptors)
indirect (G protein-linked receptors = secondmessenger system)
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Modes of Action: Direct Action
open ion channels immediate and localized
action
action depends on binding
of NT to receptors followedby channel activation, ion
influx and membrane
potential changes
excitatory examples:
aspartate, acetylcholine
(ACh), glutamate, ATP
*open Na+/K+, Ca2+
channels leading to
depolarization
inhibitory examples:
gamma aminobutyric acid
(GABA), glycine
*open Cl- or K+ channels
leading to
hyperpolarization
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Modes of Action: Indirect Action
slower, longer-lasting effects work through second messengers
binding of NT with receptor activates Gprotein in membrane which works through
cyclic AMP (cAMP = second messenger) to: regulate ion channels (open or close)
activate kinase enzymes within cytoplasm
(activate proteins in cytoplasm)
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Modes of Action: Indirect ActionExamples
Biogenic amines (dopamine, norepinephrine, epinephrine)
Peptides (endorphins, dynorphins, substance P)
ACh (at muscarinic receptors)
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Structural Classes of Neurotransmitters
Classified according to chemicalstructure:
Acetylcholine (ACh)
Biogenic Amines
Amino Acids
Peptides
Novel Messengers
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Acetylcholine (ACh)
first NT to be discovered
excitatory to skeletal muscles
excitatory/inhibitory to viscera
found in CNS and PNS (NMJ with skeletal
muscle, NEJ for parasympathetic nervous
system)
formed from acetyl-CoA and choline
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Acetylcholine (ACh)
degraded by acetylcholinesterase (AChE)
Myasthenia gravis - autoimmune disorder
of skeletal muscle ACh receptors
Alzheimers disease - decreased ACh level
in brain that ultimately results in mentaldeterioration
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Biogenic Amines
synthesized from amino acid tyrosine
found in CNS and PNS
catecholamines norepinephrine [NE], epinephrine, dopamine,
excitatory or inhibitory
indolamines seratonin and histamine
generally inhibitory
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Biogenic Amines
play role in emotional behavior and helpregulate biological clock; norepinephrineis main NT of sympathetic division of ANS
schizophrenia - overproduction ofdopamine
Parkinsons disease - deficient dopaminein basal ganglia
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Amino Acids & Peptides
Amino Acids GABA = gamma amino butyric acid (principal
inhibitory NT in brain),
glycine (generally inhibitory NT, in spinal cord),
glutamate (CNS, excitatory) Peptides (Neuropeptides)
strings of amino acids produced in CNS andPNS:
endorphins and enkephalins (natural opiates)
substance P (mediator of pain signals)
some also produced by nonneural tissues (e.g.,cells of GI tract - somatostatin, cholecystokinin,vasoactive intestinal peptide [VIP])
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Novel Messengers
Neurotransmitters that dont fit other
categories
NO = nitric oxide
involved in long-term synaptic potentiation(learning and memory)
relaxation of intestinal smooth muscles
responsible for brain damage in stroke
patients
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Novel MessengersNeurotransmitters that dont fit other
categories ATP = adenosine triphosphate
promotes synthesis and uptake of other NTs inCNS and PNS
CO = carbon monoxide
enhances neurotransmission in some circuitsinvolved in logic
regulator of cyclic GMP (second messenger)
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Termination of NT Effects
1. removal from cleft by reuptakeinto astrocytes or presynapticmembrane (e.g., norepinephrine)
2. degradation of NT by enzymespresent in postsynaptic membraneor synaptic cleft
e.g., acetylcholine [ACh] degradedby the enzyme acetylcholinesterase -[AChE]
3. diffusion away from cleft
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Causes Neurotransmitters to be out ofbalance
chronic stress,
poor dietary habits,
neurotoxins,
genetics.
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Some symptoms of NeurotransmitterImbalance ; chronic stress
the primary contributor toneurotransmitter imbalance. Stress,both emotional and physical, cancause neurons to use up largeamounts of neurotransmitters to helpus cope with the situation
Chronic daily stress, from a busy
career, a stressed relationship, or abacterial or viral infection, will tax thenervous system, and over time,deplete neurotransmitter supplies
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Some symptoms of NeurotransmitterImbalance; poor dietary habits
Diets with insufficient proteins ortoo many high glycemiccarbohydrates will increase
excretion of neurotransmitters Also, diets low in Omega-3 fatty
acids will lead to poor neuronfunction because our brain cell
membranes are composedprimarily of lipids and Omega-3fats help to stabilize thesemembranes
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Some symptoms of NeurotransmitterImbalance; neurotoxins
There are a vast amount of
environmental toxins, not to
mention the use of alcohol,nicotine, and caffeine that also
affect brain chemistry and nervous
system health.
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Some symptoms of NeurotransmitterImbalance; genetics
Some individuals are metabolically
predisposed to neurotransmitter
deficiencies or excesses. Certainhealth conditions, such as depression
and attention deficit/hyperactivity
disorder, are found to run in families