Chemical Messengers Neurotransmitters Hormones 2013 Pearson Supplemental Education

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Chemical Messengers Neurotransmitters Hormones © 2013 Pearson Supplemental Education, Inc. Chapter 18, Section 6

Chemical Messengers Neurotransmitters Hormones © 2013 Pearson Supplemental Education, Inc. Chapter 18, Section 6 4/13/2013

Chemical Messengers: for coordination of biological processes within an organism § Terms and Definitions:

Chemical Messengers: for coordination of biological processes within an organism § Terms and Definitions: § neuron: a nerve cell. § neurotransmitter: neurotransmitter a chemical messenger between a neuron and another target cell; neuron, muscle cell or cell of a gland. - the molecule acts over a short distance (across a synapse, ~ 0. 1 µm) Eg, Acetylcholine § hormone: a chemical messenger released by an endocrine gland (secretary organ) into the bloodstream and transported there to reach its target cell (its site of action). over a long distance (~ 20 cm). Eg, Insulin © 2013 Pearson Education, Inc. Chapter 18, Section 6

Chemical Messengers § Five Classes: : § Cholinergic Messengers: Acetylcholine, and likes § Amino

Chemical Messengers § Five Classes: : § Cholinergic Messengers: Acetylcholine, and likes § Amino acid Messengers: Glutamate, GABA, etc. § Adrenergic Messengers: Monoamines § Peptidergic Messengers: Insulin, Glucagon, etc. § Steroid Messengers: Androgen, Estrogen, etc. § Messengers are also classified by how they work; § activate enzymes. § affect the synthesis of enzymes. § affect the permeability of membranes. § act directly or through a secondary messenger. © 2013 Pearson Education, Inc. Chapter 18, Section 6

Chemical Communication § Many drugs used in medicine influence chemical communication § Antagonist: a

Chemical Communication § Many drugs used in medicine influence chemical communication § Antagonist: a molecule that blocks a natural receptor and prevents its stimulation. § Agonist: a molecule that competes with a natural messenger for a receptor site; it binds to the receptor site and elicits the same response as the natural messenger. § A drug may decrease or increase the effective concentration of messenger. © 2013 Pearson Education, Inc. Chapter 18, Section 6

§ A neurotransmitter © 2013 Pearson Education, Inc. Chapter 18, Section 6 5

§ A neurotransmitter © 2013 Pearson Education, Inc. Chapter 18, Section 6 5

Acetylcholine (ACh): the main cholinergic messenger the first neurotransmitter found (1914) by Henry Dale

Acetylcholine (ACh): the main cholinergic messenger the first neurotransmitter found (1914) by Henry Dale & Otto Loewi (NP, 1936) § communicate between the nervous system and the muscle. § When stimulated, it releases into the synapse where it binds to muscle cell receptors causing the muscles to contract. Amine (Quaternary) as well as Esther © 2013 Pearson Education, Inc. Chapter 18, Section 6 6

Acetylcholine § Storage and release of acetylcholine (ACh). § The nerve cells that bring

Acetylcholine § Storage and release of acetylcholine (ACh). § The nerve cells that bring messages contain ACh stored in vesicles. § The receptors on muscle neurons are called nicotinic receptors because nicotine inhibits them. § The message is initiated by calcium ions, Ca 2+. § When Ca 2+ concentration becomes more than about 0. 1 m. M, the vesicles that contain ACh fuse with the presynaptic membrane of nerve cells and empty ACh into the synapse. § ACh travels across the synapse and is absorbed on specific receptor sites. © 2013 Pearson Education, Inc. Chapter 18, Section 6

Acetylcholine § Action of the acetylcholine (cont’d) § The presence of ACh on the

Acetylcholine § Action of the acetylcholine (cont’d) § The presence of ACh on the postsynaptic receptor triggers a conformational change in the receptor protein. § This change opens an ion channel and allows ions to cross membranes freely. § Na+ ions have higher concentration outside the neuron and pass into the cell. § K+ ions have higher concentration inside the neuron and leave the cell § This change of Na+ and K+ ion concentrations is translated into a nerve signal. § After a few milliseconds, the ion channel closes. © 2013 Pearson Education, Inc. Chapter 18, Section 6

Acetylcholine in Action © 2013 Pearson Education, Inc. Chapter 18, Section 6

Acetylcholine in Action © 2013 Pearson Education, Inc. Chapter 18, Section 6

Acetylcholine § Removal of ACh § ACh is removed from the receptor site by

Acetylcholine § Removal of ACh § ACh is removed from the receptor site by hydrolysis catalyzed by the enzyme acetylcholinesterase. § This rapid removal allows nerves to transmit more than 100 signals per second. © 2013 Pearson Education, Inc. Chapter 18, Section 6

Acetylcholine is linked to Alzheimer’s disease § In Alzheimer’s disease, ACh levels may decrease

Acetylcholine is linked to Alzheimer’s disease § In Alzheimer’s disease, ACh levels may decrease by 90%. § Aricept, an Alzheimer’s medication, slows the breakdown of ACh in order to elevate the acetylcholine levels in the brain. © 2013 Pearson Education, Inc. Chapter 18, Section 6 12

Catecholamines © 2013 Pearson Education, Inc. § Include dopamine, norepinephrine, and epinephrine § All

Catecholamines © 2013 Pearson Education, Inc. § Include dopamine, norepinephrine, and epinephrine § All of these are closely related in structure and all are synthesized from the amino acid tyrosine. Chapter 18, Section 6 13

Dopamine § produced in the nerve cells of the midbrain and acts as a

Dopamine § produced in the nerve cells of the midbrain and acts as a natural stimulant to give us energy and feelings of enjoyment. § Control muscle movement, improve, cognition, memory, & learning § Cocaine and amphetamine block the reuptake of dopamine resulting in a longer lifetime in synapse. © 2013 Pearson Education, Inc. Chapter 18, Section 6 14

Norepinephrine and Epinephrine § Norepinephrine (noradrenaline) and epinephrine (adrenaline) are hormonal neurotransmitters that play

Norepinephrine and Epinephrine § Norepinephrine (noradrenaline) and epinephrine (adrenaline) are hormonal neurotransmitters that play a role in sleep, attention and focus, and alertness. § Epinephrine is synthesized from Norepinephrine. § Both are normally produced in the adrenal glands. § Both are highly produced during the fight-or-flight response, increasing blood pressure, heartv rate, constrict blood vessel, dilate airways, stimulating breakdown of glycogen. § Administered during cardiac arrest. broncodialator. § Low level leads to Attention Deficit Disorder(ADD) © 2013 Pearson Education, Inc. Chapter 18, Section 6 15

Serotonin (5 -Hydroxytryptamine) § Serotonin helps us relax, sleep deeply and peacefully, think rationally,

Serotonin (5 -Hydroxytryptamine) § Serotonin helps us relax, sleep deeply and peacefully, think rationally, and it provides us a feeling of well-being and calmness. § Serotonin is synthesized from the amino acid tryptophan. § Psychedelic drugs stimulate the action of serotonin at its receptors. § Low serotonin levels may be associated with depression, anxiety disorders, etc. § Prozac and Paxil (antidepressant drugs) are selective serotonin reuptake inhibitors (SSRIs). © 2013 Pearson Education, Inc. Chapter 18, Section 6 16

Prozac and Paxil © 2013 Pearson Education, Inc. Chapter 18, Section 6 17

Prozac and Paxil © 2013 Pearson Education, Inc. Chapter 18, Section 6 17

Histamine § synthesized in the nerve cells in the hypothalamus from the amino acid,

Histamine § synthesized in the nerve cells in the hypothalamus from the amino acid, histidine. § is produced by the immune system in response to pathogens and invaders, or injury. § When it combines with histamine receptors, it produces allergic reactions – inflammation, watery eyes, itchy skin, . etc. © 2013 Pearson Education, Inc. Chapter 18, Section 6 18

Amino Acid Neurotransmitters Glutamate § the most abundant neurotransmitters in the nervous system. §

Amino Acid Neurotransmitters Glutamate § the most abundant neurotransmitters in the nervous system. § stimulates the synthesis of nitrogen monoxide (NO). Both Glutamate & NO involved in learning and memory § Too much glutamate in the spinal cord causes degeneration of nerve cells (Lou Gehrig’s disease of Muscular atrophy). § Too rapid uptake of glutamate may results in schizophrenia: © 2013 Pearson Education, Inc. Chapter 18, Section 6 19

Gamma(g)-Aminobutyric Acid (GABA) § the most common inhibitory neurotransmitter in the brain. § produces

Gamma(g)-Aminobutyric Acid (GABA) § the most common inhibitory neurotransmitter in the brain. § produces a calming effect by inhibiting the ability of nerve cells to send electrical signals to nearby nerve cells. § Alcohol, & sedatives increases the inhibitory effects. § Caffeine decreases the GABA levels in the synapses causing opposite effects. © 2013 Pearson Education, Inc. Chapter 18, Section 6 20

© 2013 Pearson Education, Inc. Chapter 18, Section 6

© 2013 Pearson Education, Inc. Chapter 18, Section 6