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66 Cards in this Set
- Front
- Back
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smaller motor units |
-fewer fibers -recruited first -slow-twitch oxidative -contract and relax slowly -contribute less force |
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larger motor units |
-more fibers -recruited later -fast-twitch glycolytic -contract and relax quickly -contribute more force |
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soleus |
posture muscle |
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activation of autonomic division |
-pupillary dilation -adrenaline rush -increased heart rate -increased blood pressure |
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sympathetic system |
"fight-or-flight" energetic |
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parasympathetic |
"rest-and-digest" restorative |
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main characteristics of autonomic motor division |
-dual antagonistic input to target tissues -diffuse release of NT on target tissue -typically involuntary -homeostatic |
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mechanistic themes for maintaining homeostasis in autonomic division |
-dual antagonistic control -tonic control -variable receptor expression |
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hypothalamus |
synthesizes and secretes certain neurohormones which control body temperature, hunger, thirst, fatigue, sleep, and circadian rhythms |
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medulla |
functions of breathing, heart rate and blood pressure |
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pons |
sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture |
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main autonomic control regions |
hypothalamus medulla pons |
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dorsal root |
sensory input enters here |
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ventral root |
somatic input exits here |
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ganglion |
collection of cell bodies and tissues |
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general organization of autonomic motor neurons |
-two efferent neurons -first neuron is in the CNS -second neuron is in the PNS (autonomic ganglia) |
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distribution of parasympathetic ganglia |
exit CNS at brainstem and sacral (bottom of spinal cord) |
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distribution of sympathetic ganglia |
near spinal column thoracic and lumbar (mid spinal cord) |
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parasympathetic axons |
preganglionic axons arise from cranial nerves and S2-S4 spinal nerves vagus nerve contains 75% of all parasympathetic fibers |
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sympathetic axons |
preganglionic axons arise from T1-L2 spinal nerves |
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sympathetic neurotransmitters |
preganglionic neuron releases ACh which binds to nicotinic receptor on autonomic receptor this releases norepinephrine to an adrenergic receptor on target tissue |
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metabotropic |
GPCR pathway |
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adrenergic |
metabotropic pathway for norepinephrine and epinephrine |
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cholinergic |
pathway for acetylcholine |
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nicotinic |
cholinergic ionotropic pathway |
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muscarinic |
cholinergic metabotropic |
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varicosities |
chain of release sites for neurotransmitters |
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release of norepinephrine from varicosity to target cell |
1. action potential arrives at varicosity 2. depolarization opens voltage-gated Ca channels 3. Ca entry triggers exocytosis of synaptic vesicles 4. NE binds to adrenergic receptor on targets 5. Receptor activation ceases when NE diffuses away from the synapse 6. NE is removed from synapse 7. NE can be taken back into synaptic vesicles for re-release 8. NE is metabolized by monoamine oxidase (MAO) |
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cholinergic synapses |
parasympathetic varicosity releases acetylcholine to a muscarinic receptor which activates an amplifier enzyme and ACh is removed by AChE |
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adrenergic synapses |
sympathetic varicosity releases nor/epinephrine to an adrenergic receptor which activates an amplifier enzyme and is removed from monoamine transporter (MAT) |
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parasympathetic responses |
pupil constriction, slow heart rate, lung constriction, increased digestion, bladder release, erection |
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sympathetic responses |
pupil dilation, fast heart rate, lung dilation, decreased digestion, bladder retention, skin vessel constriction, muscle vessel dilation, ejaculation |
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cocaine |
-indirect agonist -blocks reuptake of NE into adrenergic nerve axon terminals by binding membrane transporter or uptake site -extends NE's excitatory effect on target -"upper" |
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anti-depressants |
-indirect agonists that act on membrane transporters (SSRIs) -prevention of degradation (MAOIs) |
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side effects of MAOIs |
-heart problems -constipation and urination difficulty -sexual dysfunction |
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iris sphincter |
constricts eye, parasympathetic, muscarinic ACh receptors |
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iris dilator |
dilates eye, sympathetic, α1 adrenergic cause contraction |
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sympathetic response is dominant when |
sympathetic response is enhanced OR parasympathetic response is inhibited |
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parasympathetic response is dominant when |
parasympathetic response is enhanced OR sympathetic response is inhibited |
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atropine |
dilating drug: mydriatic muscarinic antagonist blocks the muscarinic ACh receptor "parasympatholytic" drug |
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phenylephrine |
dilating drug: mydriatic adrenergic agonist stimulates α1 adrenergic receptors "sympathomimetic" drug |
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chromaffin cells |
make up adrenal medulla secrete 80% epinephrine and 20% norepinephrine |
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multiunit smooth muscles |
blood vessels |
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resting tonic control |
sympathetic release of norepinephrine to arteriole/vein |
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constriction of arteriole/vein |
more NE released to arteriole/vein, α1 receptor (intestine/skin) |
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dilation of arteriole/vein |
less NE released to arteriole/vein |
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epinephrine receptor |
B2 receptor, vessel dilates (skeletal muscle) |
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phosphorylation |
transfer of a phosphate group |
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dephosphorylation |
removal of a phosphate group |
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why have different receptors that respond to the same set of ligands? |
fine control of local physiological responses, even with systematic release of hormone |
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smooth muscle lining BV of intestine/skin |
more α1 adrenergic receptors, more norepinephrine |
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smooth muscle lining BV of skeletal muscle/bronchi |
more B2 adrenergic receptors, more epinephrine |
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calcium initiates contraction |
1. intracellular Ca concentration increases when Ca enters cell and is released from SR 2. Ca binds to calmodulin in cytosol 3. Ca-calmodulin activates myosin light chain kinase 4. MLCK phosphorylates light chains in myosin heads and increases myosin ATPase activity 5. active myosin crossbridges slide along actin and create muscle tension |
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calcium desensitization |
increase in MLCP activity overrides increases in Ca |
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smooth muscle relaxation |
ratio of MLCK: MLCP, MLCK dependent on Ca-CaM 1. free Ca in cytosol decreases when Ca is pumped out of cell or back into SR 2. Ca unbinds from CaM (MLCK activity decreases) 3. myosin phosphatase removes phosphate from MLC which decreases myosin ATPase activity 4. less muscle ATPase activity results in decreased muscle tension |
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Calcium entry to cytosol from ECF |
voltage-gated Ca channels open in response to depolarizing stimulus ligand-gated Ca channels open in response to ligand binding stretch-activated channels open in response to change in muscle tone |
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Calcium-induced calcium release |
RyR on SR open in response to small amounts of Ca entering from ECF IP3 channels on SR open through adrenergic receptor activation |
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α1 adrenergic receptor |
affinity for norepinephrine, only needs Ca from SR to cause contraction activates PLC -> IP3 -> releases Ca from SR -> activates MLCK via Ca-CaM dependent kinase |
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B2 AR |
affinity for epinephrine, causes relaxation activates adenylyl cylase -> cAMP -> PKA -> phosphorylates MLCK ALSO inhibits IP3 binding to receptor enhances Ca-ATPase activity at SR membrane enhances MLCP activity |
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α2 AR |
promotes contraction by inhibiting adenylyl cyclase |
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anaphylaxis |
systematic allergic reaction -respiratory distress -hypotension -hives immediately inject epinephrine |
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epi-pen |
α1 receptor prevents and relieves hypotension and shock & relieves upper airway obstruction B2 receptor decreases wheezing and decreases hives |
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asthma |
airway constriction and excess mucous secretion histamine release triggered by allergens or airway irritants; smooth muscle of airway constricts in response to histamine |
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treatment for asthma |
albuterol which dilates lung air passages |
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electromechanical coupling depolarization can cause contraction |
intracellular Ca conc increase when Ca enters cell and is released from SR |
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pharmomechanical coupling ligand-binding causes contraction |
IP3 induced calcium release |
