| Term | Definition |
|---|
| Muscle Tissue | contractile tissue, derived from mesodermal layer of embryonic germ cell that contain contractile filaments that move past each other & change size of cell producing force & motion |
| Smooth Muscle | Involuntary muscle w/i walls of organs and structures |
| Smooth Muscle Locations | encircles bld vessels; found in walls of digestive, respiratory, urinary, & reproductive organs |
| Functions of Smooth Muscle | move food, urine, & respiratory passageways; controls diameter of respiratory passageways; regulates diameter of bld vessels & contributes to regulation of tissue bld flow |
| Characteristics of Smooth Mucle | NO striations, generally NOT voluntary, cells either functionally syncytial (Unitary) or independent from each other (Multiunit) |
| Contraction & Relaxation of smooth muscle fiber is | both slower & longer lasting compared w/ skeletal&cardiac muscle |
| Smooth muscle can shorten & stretch... | to a greater extent than othe muscle types |
| Smooth muscle fibers contract in response to... | action potentials from autonomic nervous system, stretching, hormones, local factors |
| Smooth Muscle contain | FEW mitochondria & depend, on glycolysis for metabolic needs |
| Smooth Muscle have... | single, oval, centrally located nucleus, NO T-tubules, poorly developed SR, & actin/myosin not in orderly sarcomeres; which contains tropomysin NOT troponin |
| Smooth Muscle contain | dense bodies in the CYTOPLASM, ATTACHED to cell membrane, BOUND to actin filament by alpha-actinin |
| During contraction tension is TRANSMITTED to... | intermediate filaments PULLING on dense bodies |
| Single-Unit vs Multi-Unit | Form muscular walls of hollow organs & are mononucleate cells w/ NO striations |
| Single-Unit (Unitary; visceral) | sheets of electrically coupled cells acting in unison, sparsely innervated, autorhythmic, coupled by low-resistance gap junctions, contract synchronously (spontaneously active), |
| Multi-Unit | made of discrete bundles of cells, few or no gap junctional bridges, DENSELY innervated fibers contracting only to RESPONSE to innervation, funtional similarities to skeletal m., |
| Multi-Unit tissue located | in walls of LARGE arteries airways of lungs, vas deferens, arrector pilli of hair, ciliary muscle that adjust lens & iris of the eye |
| Single-Unit tissue located | in walls of SMALL arteries, hollw organs (uterus, ureters, bronchi, GI track (gut) |
| Varicosities | endings of postganglionic autonomic neurons |
| Autonomic nerve fibers branch & form... | diffuse junctions w/ underlying smooth muscle fibers |
| Varicosities in terminal axons... | contain neurotransmitter |
| Neurotransmitters released from varicosities diffuses to receptors... | on sooth muscle cell plasma membranes |
| Smooth Muscle excitation transmitted by.. | Ca2+ action potential or simple diff. of Ca2+ into fiber |
| Actin/myosin loosely arranged around... | periphery of cell, held by protein dense bodies |
| arrangement of fibers cause cell to become | globular when contracts |
| Myosin slide along actin for long distance w/o | encountering end of sarcomere |
| smooth muscle myosin has... | hinged heads all along its length |
| Smooth Muscle operate over.. | large range of lengths (60-75% shortening possible) |
| smooth muscle very... | energy efficient (O2 consumption ~1% of same weight of skeletal musle @ same tesion |
| smooth muscle can maintain... | force for long periods via latch state |
| smooth muslce can be... | myogenic (spontaneously active) |
| smooth muslce has a... | BELL shaped length tesion curve |
| Poorly develped... | Sarcoplasmic reticulum |
| intermediate filament | forms structual backbone |
| function on nerve supply is not to initiate activity in muscle, but to | modify it |
| Characeristics of Unitary(Single-Unit) smooth muscle | instable membrane potential, shows continuous irregular contractions independent of nerve supply |
| Tonus or Tone | maintained stated of partial contraction |
| Charac. of Multiunit smooth muscle | nonsyncytial, contractions do NOT spread widely causing contractions to be more discrete,fine, & localized |
| Effects of acetylcholine & norepinephrine on unitary smooth muslce emphasis | spontaneous activity in ABSENCE of nervous stimulation, sensitivity to chem. agents released from nerves locally or by circulation |
| Smooth muslce has slower contraction when compared to skeletal muscle b/c | of unique isoforms of myosin & contractile-related proteins & their distinct regulation |
| Plasticity of smooth muslce is | variability of the tension it exerts @ given length, impossible to correlate length & develop tension accurately; no resting length can be assigned |
| Smooth muslce has diverse controls of | edocrine, paracrine, local nervous system, & autonomic nervous system regulation |
| Contraction of smooth muscle | 1. increase in cytosolic Ca@+ initiates contraction 2. Calcium activation of myofilaments works through calmodulin (NOT through troponin) |
| Contraction-relaxation regulation is | myosin based regulations |
| Endothelial cells line inside of bld cells & release EDRF identified as | SECOND messenger mol. Nitric oxide |
| EDRF | endothelia derived relaxation factor |
| cyclic quanosine monophosphate (cGMP) | once in musle NO directly activates a soluble quanylate cyclase producing another 2nd mess. |
| cGMP activates cGMP- specific protein kinases affecting | ion channels, Ca2+ homeostasis, phosphatases, or all that lead to smooth muscle relaxation |
| Bronchoconstriction is a result of | overexcitation of mooth muscle in airways |
| rapid response to inhalers are related | to smooth muscle relaxation |
| ventolin, albuterol, sambuterol | rapid response inhaler drugs frequently target B-adrenergic receptors in airway of smooth muscle |
| NO pathway naturally down reg. by PDE which transforms | cGMP into nonsignaling form, GMP |
| sildenafil, tadalafil, & vardenafil | inhibitors of PDE5, increasinf bld flow in limited regions, adn offsetting erectile dysfunction |
| Structure of meuromuscular junction | branching of motor axons w/ terminals embedded in grooves in muscl fiber's surface |
| Neuromuscular junction | junction of motor neuron axon terminal & muscle fiber sarcolemma |
| During neuromuscular junction acetylholine released | @ junction depolarizes sarcolemma, leading to generation of muscle action potential |
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