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69 Cards in this Set
- Front
- Back
Somatic NS |
there is onl one place where neurotransmitters are released since there is only one synapse! (Neuromuscular junction) |
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all somatic motor neurons release __________ at their synapse with skeletal muscles. their effect is always __________ |
Acetycholine excitatory (EPSPs) |
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Autonomic NS |
since we have a two neuron system we have two synapses to deal with preganglionic fiber>ganglion>postganglionic fiber> smooth or cardiac muscles, glands, or GI neurons |
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Autonomic NS: within the ganglion the signal needs to be ______________. this is similar to the somatic system and thus requires a neurotransmitters that is excitatory |
transmitted from pre=ganglionic neuron to postganglionic neuron. |
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the neurotransmitter released in the synapse between pre- and postganglionic neurons is always |
acetylcholine |
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the actual functional difference between parasympathetic and sympathetic nervous system is |
thus at the level of the postsynaptic neuron and synapse with the effector organ |
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parasympathetic postganglionic neurons release |
acetylcholine |
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sympathetic postganglionic neurons release |
norepinephrine |
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sympathetic activation of the adrenal medulla is a special case because there is |
no postganglionic neuron |
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the activated adrenal medulla releases: |
epinephrine and norepinephine into the bloodstream |
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________________and __________________ are thus two major neurotransmitters released by the ANS |
acetlycholine and norepinephrine |
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ACh is released by all preganglionic neurons of |
PS and S and by all postganglionic PS neurons |
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Postganglionic Sympathetic neurons release |
NE |
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neurons that release ACh are called: |
cholinergic fibers |
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neurons that release NE are called |
adrenergic fibers |
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ANS receptors: |
the receptor, located in the cell membrane of the target cell, is a molecular transducer that sets in motion a series of cellular effects |
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the type of receptor determines |
the specificity of cellular actions |
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the neurotransmitter is the molecular trigger. it requires |
binding to the receptor before the receptor becomes activated |
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primary ligand+agonist= antagonist= |
response no response |
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the two primary ligands, agonists of the ANS are thus |
Acetylcholine and Norepinephrine (epinephrine)
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acetlycholine binds to |
cholinergic receptors |
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norepinephrine binds to |
adrenergic receptors |
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cholinergic receptors |
bind to ACh |
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two kinds of receptors: |
1. nicotinic receptors also called nAChR 2. muscarinic receptors also called mAChR |
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cholinergic nicotinic receptors |
members of superfamily of ligand gated membrane channels that mediate fast signal transmission at synapses |
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all nicotine AChRs are pharmacolically identical in that they bind _______ as a ligand agonist |
nicotine |
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all nicotinic AChRs are _________ |
pentamers: they consist out of 5 polypeptide subunits that are clustered around a central receptor channel |
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there are 2 ligand binding sites formed by the aplha subunits and an adjacent subunit |
binding to both sites needed for channel to open binding to only one site prevents channel activation |
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binding of a ligand to the receptor causes conformational changes that ________ |
open the central channel to mostly Na and some K ions |
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what is the normal physiological ligand in the body |
ACh |
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what occurs in the cell that has this receptor when bond binding sites are occupied with ACh |
the channel that opens and Na rushes into the cell, resulting in depolarization |
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where do we find nicotinic cholinergic receptors |
on post synaptic cell membranes that experience an exotysosis of ACh from presynaptic vesicles and requiring fast depolarization of the postsynaptic area |
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3 areas where find nicotinic cholinergic receptors |
1. on the motor endplates of skeletal muscle (somatic nAChR) 2. on all cell bodies and dendrites of postganglionic neurons of parasympathetic and sympathetic system (ganglionic nAChR) 3. on the hormone producing cells of adrenal medulla |
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the effect of ACh on these receptors is thus always stimulatory. it causes a |
depolarization of the cell (this is your typically chemically gated Na channel) |
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are the nACH receptors the same in the somatic system as the autonomic isystem |
yes, they are similar in structure but have different proteins that make up the channel. different proteins react differently to different drugs/toxins. |
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Epibatidine |
example of nAChR effector isolated from the skin of an exuadorian frog exhibits very potent agonistic properties thus would induce ANS potetiation (hallucinations) and muscular spasms |
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curare |
example of nAChR effector isolated from the bark and leaves of the tropical plant Strychnos Toxifera it is a potent nAChR blocker in the NMJ but affects ganglionic receptors as well used to create muscle paralysis |
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where do we find muscarine cholinergic receptors |
on teh target organs served by cholinergic postganglionic neurons (parasympathetic nerves) |
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cholinergic muscarinic receptors |
these receptors bind ACh as well but the mechanism and response elicited by these receptors differs from previously discussed nAChRs |
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muscarine receptors bind ___________ |
muscarine |
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muscarine |
a component derived from the fly agaric mushroom |
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muscarine receptors operate as ____________ and mediate their response by activating a variety of intra cellular pathways |
G protein coupled receptors |
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there are two important G protein coupled systems determined by the specific enzyme that becomes activated and therefore different product produced. |
this is a very common pathway and is similar in for example smell and taste activation |
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PLPc G protein coupled receptors |
the concept of this pathway is the same except that a different enzyme is activated. |
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pLPc (phospholipase C) makes two products |
Diacylglycerol (DAG) and Insoitol Triphosphate (IP3) |
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the purpose of these pathways is to generate |
intracellular signals to activate specific tissues. those intracellular signals are the product of the activated enzymes (cAMP or DAG and IP3)
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muscarinic receptors are typically found on |
target tissues of the parasympathetic NS |
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if the receptors are located in smooth muscles: if the receptors are located in glands: if the receptors are located in impt metabolic cells |
the purpose is to start or inhibit smooth muscle contraction the purpose is to start or inhibit the secretion of the glands the purpose is to start or inactivate metabolic processes |
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what effects do cAMP and DAG have |
they both activate protein kinases protein kinases in turn will phosphorylate and activate/inactivate proteins this would be a fast way of turning on and off a metabolic pathway |
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IP3 |
acts on smooth ER results is that calcium will be released into the cytoplasm calcium in turn will bind to and activate a protein called calmodulin activated calmodulin can now activate enzymes and other proteins |
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how many different kinds of muscarinic receptors are there |
5 |
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muscarinic receptors are named ______. these receptors are typical for parasympathetic target tissues |
M1 to M5 |
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M2 |
located in the heart action: inhibits adenylate cyclase (thus decreases activities) |
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M3 |
located in gut smooth muscle, glands action: activates PLP-C (mediates contraction) |
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the M2 receptor, when it binds to ACh (released from the vagus nerve) |
will stop production of intracellular cAMP and ithis is the basis for reduced heart rate and heart contraction |
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The M3 receptor when it binds ACh will produce |
IP3 and this is the basis for increases smooth muscle contraction. found in the constrictor muscles of the iris and smooth muscle of digestive system |
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muscarinic antagonists |
prevents activation of parasympathetic target organs |
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atropine: |
plant: atropa belladonna lethal dose: 10 berries dilated pupils, hallucinations, urinary retention |
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adrenergic receptors also called adrenoceptors |
mediate the acitons of epinephrine, norepinephrine and related compounds |
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adrenergic receptors are found on the target organs of the |
sympathetic nervous system |
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epinephrine and norephiinephrine belong to the class of |
catecholamines and are the derivatives from the amino acid: tyrosine |
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these receptors (adrenergic) are also coupled to
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g proteins which stimulate or inhibit intracellular signalling pathways. (signal transcution very similar to muscarinic receptors) |
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alpha 1: location and action |
mostly smooth muscle of peripheral blood vessels, eye, arrector pili
via PLPc, increases IP3 and thus free Ca. results in excitation, vasoconstriction, pupil dilation
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beta 1 |
location: mostly cardiac muscle tissue and kidney action: via Ad. cyclase and cAMP. increased heart rate and contraction, renin release |
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beta 2 |
in smooth muscle of coronaries, bronchi action: via ad. cyclase and cAMP. relaxation and vasodilation |
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beta 3 |
found in adipose tissue. action: lipolysis |
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alpha receptors |
when activated, generally produce exitatory responses of smooth muscles in which they are located |
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beta receptors |
when activated generally produce inhibitory responses of smooth muscle in which they are located |
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complex phyisological responses result from |
catecholamine stimulation because there are multiple receptor types which are differentially expressed in different tissues and cells. |