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Lecture 16

BGYB30H3 Lecture 16 Notes Muscles 2-Nov 3


Department
Biological Sciences
Course Code
BIOD27H3
Professor
Ingrid L.Stefanovic
Lecture
16

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BGYB30H3 Lecture 16 Notes
-skeletal muscles attach to bones by tendons and function by positioning and moving the
skeleton
-somatic motor neurons cause contraction of skeletal muscles
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-smooth muscles are muscles of internal organs that influence movement of materials around,
in and out of the body
-primary extrinsic control of smooth muscles originates from autonomic nervous system
-some smooth muscles can contract spontaneously and can be modulated by hormones
-cardiac muscle is only found in the heart and pumps blood around the body
-cardiac muscles can contract and relax spontaneously
-primary extrinsic control of cardiac muscles also arises from the ANS
-cardiac and skeletal muscles have striations only
-muscles have many nuclei and mitochondria
-origin of skeletal muscles is the point connected to the bone that is most stationary and closest
to the trunk
-insertion is the point of the muscle-bone attachment that is most mobile and distant from
the trunk
-flexor muscles bring bones closer together (e.g. biceps)
-extensor muscles bring bones farther apart (e.g. triceps)
-antagonistic muscle groups have opposite effects on one another (e.g. when bicep relaxes,
triceps contract)
-most joints have one flexor and one extensor
-collections of muscle cells work together as a unit
-muscle fibres are in groups called fascicles that are connected by connective tissue
-nerve cells and blood vessels are found between fascicles
-muscle cells are long and cylindrical
-muscle fibres are parallel and ensheathed in connective tissue
-muscles are coated by tendons
-muscle cytoplasm is called the sarcoplasm while plasma membrane is called the sarcolemma
-muscle ER is called the sarcoplasmic reticulum
-small fibres in the muscle fibre are myofibrils, which contract due to releasing calcium
-t-tubules are found between terminal cisternae of adjacent myofibrils
-thin and thick filaments compose the myofibril
-t-tubules allow depolarization of sarcolemma to reach interior of muscle fibres
-membrane of t-tubule is continuous with sarcolemma
-lumen of t-tubule is continuous with EC fluid
-terminal cisternae store calcium
-cytosol between myofibrils contains glycogen and mitochondria
-muscles have contractile protein and elastic fibres
-one muscle fibre contains >1000 myofibrils
-myofibrils contain six proteins in which two are contractile, two are regulatory and two are
accessory
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