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Physiology 2

Physiology 2, Comparison of Muscle Types

CharacteristicSkeletal MuscleMultiunit Smooth MuscleSingle unit Smooth MuscleCardiac Muscle
Location attached to skeleton large blood vessels, eys & hair follicles walls of hollow organs in digestive, reproductive, & urinary tracts & in small blood vessels heart ONLY
Function movement of body in relatin to external environment varies with structure involved movement of contents within hollow organs pumps blood out of heart
Mechanism of Contraction sliding filament mechanism sliding filament mechanism sliding filament mechanism sliding filament mechanism
Innervation somatic nervous systemt (alpha motor nuerons) autonomic nervous system autonomic nervous system autonomic nervous system
Level of Control under voluntary control, also subject to subconscious regulation under involuntary control under involuntary control under involuntary control
Initiation of Contraction Neurogenic Neurogenic Myogenic (pacemaker potentials & slow-wave potentials) myogenic (pacemaker potentials
Role of Nervous Stimulation initiates contractions accomplishes gradation initiaties contraction; contributes to gradation modifies contraction; can excite or inhibit; contributes to gradation modifies contraction; can excite or inhibit; contributes to gradation
Modifying effect on hormones no yes yes yes
Presence of thick myosin & thin actin filaments yes yes yes yes
striated by orderly arrangement of filaments yes no no yes
Presence of troponin & tropomyosin yes tropomyosin ONLY tropomyosin ONLY yes
Presence of T tubules yes no no yes
Level of development of Sarcoplasmic Reticulum well developed poorly developed poorly developed moderately developed
Cross Bridges Turned on by Ca2+ yes yes yes yes
Source of increased cytosolic Ca2+ Sarcoplasmic reticulum extracellular fluid & sarcoplasmic reticulum extracellular fluid & sarcoplasmic reticulum extracellular fluid & sarcoplasmic reticulum
Site of Ca2+ Regulation troponin in thin filaments myosin in thick filaments myosin in thick filaments troponin in thin filaments
Mechanism of Ca2+ Action physically repositions troponin-tropomyosin complex to uncover actin cross-bridge binding sites chemically brings about phosphorylation of myosin cross bridges so they can bind with actin chemically brings about phosphorylation of myosin cross bridges so they can bind with actin physically repositions troponin-tropomyosin complex
Presence of Gap junctions no yes (very few) yes yes
ATP used directly by Contractile apparatus yes yes yes yes
Myosin ATPase Activity; Speed of Contraction fast or slow, depending on type of fiber very slow very slow slow
Means by which gradation accomplished Varying number of motor units contracting (motor unit recruitment) & frequency at which they're stimulated (twitch summation) Varying number of muscle fibers contracting & varying cytosolic Ca2+ concentration in each fiber by autonomic & hormonal influences Varying cytosolic Ca2+ concentration through myogenic activity & influences of the autonomic nervous system, hormones, mechanical stretch, & local metabolites Varying length of fiber (depending on extent of filling of the heart chambers) & varying cytosolic Ca2+ concentration through autonon hormonal, & local metabolite influence
Presence of tone in absense of external stimulation no no yes no
Clear-cut length-tension relationship yes no no yes
Created by: JYarger