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52 Cards in this Set
- Front
- Back
define sympathomimetic?
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mimic effects of SNS on heart and circulation (Epi, NE, Dopamine, Isuprel)
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Define sympatholytics?
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Inhibit the function of the SNS . ( anti-adrenergics: Beta-blockers)
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What higher center regulates the SNS?
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Hypothalamus: the lateral and posterior nuclei are sympatheteic and stimulation results in discharge of the Sympatho-adrenal system
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Where do the Sympathetic preganglionic nerves pass out of the spinal cord via which nerve roots?
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Sympathetic preganglionic nerves originate in the lateral horns (INTERMEDIOLATERAL HORNS of the GRAY matter) of teh thoracolumbar segments (T1-L3) and pass out of the s.c nia the anterior roots.
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where do the sympathetic preganglionic nerve fibers arise from what segments of the spinal cord?
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T1-L2 in adults or T1- L3 neonate to adol.
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What is the only organ innervated by sympathetic preganglionic neurons?
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The adrenal (suprarenal) medulla is the only organ innervated by sympathetic preganglionic neurons
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Identify four groups of sympathetic ganglia?
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1. paravertebral ganglia(superior, middle and inferior)
2. Celiac ganglia 3. superior mesenteric ganglia 4. Inferior mesenteric ganglia |
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What is the hypogastric plexus and what pain is transmitted by it?
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The hypogastric plexus is a retroperitoneal structure that is formed by confluence of the bilateral lumbar symp chains. ..situated between the bodies of L5 & S1.
Pelvic pain caused by inflammatory diseases or cancer is transmitted via this plexus and can be relieved by a superior hypogastric plexus block. |
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Postganglionic Symp neurons originate from where?
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Postganglionic Symp neurons arise from the autonomic ganglia (paravertebral ganglia)
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What two sympathetic ganglia form teh stellate ganglion?
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The inferior cervical ganglion and the first toracic ganglion form the stellate ganglion. (In 80% of population, the inferior cervical and first thoracic ganglia are fused)
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Are the effects of sympathetic stimulatiion of a motor or sensory nature?
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Motor (efferent)
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Sympathetic nerves arising from the T5-T12 innervate what organs? How about L1-L2?
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Sympathetic nerves arising from T5-T12 innervate organs in the abdomin(intestine liver, kidneys, adrenal medula)
L1-2 innervate the bladder, colon, and rectum. |
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What are the two POSTganglionic sympathetic nervous transmitters?
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Norepinephrine (released from symp. postganglionic ceurons to viscera, heart, lungs, sm musc, salivary glands)
Acetylcholine is released t sweat glands and piloerector muscles |
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Where do PREganglionic parasympathetic nerves originate?
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CN 3,7, 9, 10 in the brainstem and from Sacral segments 2-4
(Craniosacral division) |
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Which nerve contains teh most parasympathetic fibers?
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Vagus nerve (CN X) contains 75% of all parasympathetic nerve fibers
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What autonomic nerves are cholinergic in nature?
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The nerve fibers that release acetylcholine are cholinergic
--Sym & Parasym PREganglionic --Parasym POSTganglionic --Sympathetic POSTganglionic(sweatglands and piloerector muscles) |
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What is the only endogenous compound that causes simultaneous bradycardia and hypotension
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Acetylcholine
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Where are the muscarinic sites in the autonomic system?
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Muscarinic receptors are found in tissues innervated by the parasympathetic postganglionic neurons.
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What general classes of drugs interrupt muscarinic transmission peripherally?
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Antimuscarinics (anticholinergics) such as atropine, scopolamine, and glycopyrrolate.
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Where are the nicotinic sites in the peripheral nervous system?
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Nicotinic receptors are found on cell bodies of sympathetic and parasympathetic postganglionic neurons , on chromaffin cells of the adrenal medulla and the motor end plate of the skelatel neuromuscular junct.
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What general classes of drugs interrupt the nicotinic transmission periperally?
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Nondepolarizing neuromuscular blockers interrupt nicotinic receptor transmission at the neuromuscular jx.
--the ganglionic blocker trimethaphan (Arfonad) and 2 NDMR (d-tubocurarine and metocurine) interrupt nicotinic receptor transmission at the ganglia |
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What causes Horner's syndrome?
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blockade of teh stellate ganglion with local anesthetic produces horner's synfrome (also a SE of intersccalene or supraclavicular approaches to the brachial plexus)
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What are 6 S/Sx of Horner's syndrome?
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1. Miosis
2. anhydrosis 3. vasodilation 4. nasal congestion 5. increased facial temp 6. ptosis (occur on ipsilateral side) |
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Norepi released from Sympat POSTganglionic nerve terminals has its actions terminated primarily by what mechanism normally?
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reuptake!
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Identify 2 forms of the enzyme MAO?
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Type A (MAO-A) : metabolizes serotonin, dopamine, epinephrine, and norepinephrine
Type B (MAO-B): metabolizes tyramine and phenylethylamine and dopamine |
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whaere is Monoamine oxidase (MAO-A) type A found:
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MAO-A is present in the CNS, adrenergic nerve endings, liver and gastrointestinal tract.
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In addition to respiratory and cardiovascular, what other centers are found in the brainstem?
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along with Resp and CV centers are the vomiting center, the cough center, and the swallow center.
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What are the chemical steps in the synthesis of catecholamines beginning with Phenylalamine?
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Phenylalamine
Tyrosine Dopa Dopamine Norepinephrine Epinephrine |
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What is the release of Ach from the vesicles of the nerve terminal dependent on?
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Calcium influx.
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What two properties of neuronal tissue enables them to respond to stimuli?
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1. the presence of a resting membrane potential
2. the presence of voltage gated sodium channels permit neurons to respond to stimuli |
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What is the major cation of the neuron? and outside?
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Inside: Potassium (140mM)
outside: sodium (142mM) |
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What is responsible for creating the resting membrane potential?
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Potassium diffusing out of cells through potassium leak channels
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when do voltage gated potassium channels snap open?
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when the axon depolarizes to threshold
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In what state are the voltage gated channels during the absolute refractory period?
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they are closed and no additional action potential can be evoked no matter how intense the stimulus
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Do rapidly conducting nerves have larger or smaller diameter? Are they myelinated or unmyelinated?
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Large and myelinated
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Wat ion deals with repolarization of the neuron?
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potassium
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what membrane ion channels play a role in cell repolarization
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the voltage-gated sodium channel.
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what neurotransmitter is the most common excitatory neurotransmitter in the CNS?
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glutamate
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List 3 ionotropic glutamate receptors in the central nervoous system?
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NMDA, AMPA, kainate
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What is the principle neurotransmitter of the efferent (motor) somatic nervous system?
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Acetylcholine
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What do efferent nerves of the somatic nervous system innervate?
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skeletal muscle
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How is neurotransmitter release affected by hypercalcemia, hypocalcemia, hypermagnesium, hypomagnesium?
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release is increased with hypercalcemia and hypomagnesium. and is decreased with hypocalcemia, and hyper magnesium.
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What enzyme catalyzes the synthesis of acetylcholine (ACh) ? Where does ACh synthesis occur?
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Synthesis of ACh occurs in the cytoplasm of nerve terminals.
Choline acetyltransferase (ChAt) catalyzes the formation of ACh from the precursors choline and Acetyl-CoA . |
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The action of acetylcholine is terminated by what mechanism?
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It is terminated by metabolism by acetylcholinesterase, located in the postsynaptic membranes nearbt cholinergic receptors.
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What are the two types of cholinergic receptors, and where are they found peripherally?
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MUSCARINIC and NICOTINIC receptors.
Muscarinic are cound on target tissue opposite the Parasympathetic postganglionic nerve endings. Nicotinic are located at autonomic ganglia at the neuromuscular jx. |
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what is up-regulation ?
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Up-regulation is an increase in teh number of receptors when the prevailing concentration of agonist is decreased.
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What causes upregulation of
ach receptos at the motor end plate of skeletal muscle? |
Denervation or trauma to skeletal muscle
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define down regulation?
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A decrease in the number of receptors occuring in response to an increased concentration of agonists.
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What is the first step in the termination of NE?
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Diffusion away from the receptor
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What are the three mechanisms that NE is terminated from the receptor?
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1. Diffusion
2. metabolism(MAO in tissues & COMT in blood /liver) 3. reuptake (80% of the loss of efficacy ) |
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In what proportion is NE and Epi normally released from the chromaffin cells in the adrenal medulla?
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80% Epi (Eighty/Epi)
20% NE |
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what are the 7 ligand binding sites of teh
GABA receptor? |
1. GABA
2. Barbituates 3. Benzodiazepines 4. Propofol 5. Alcohol/ anesthetic 6. steroids 7. Picrotoxin |