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Unit 3 slide 1
Muscular System ____ Human skeletal
muscles
Unit 3 slide 2
Muscular System
• Helps maintain homeostasis by …– _______– __________ – Communication– Control of body openings and passages– _____ production
Unit 3 slide 3
Muscle Tissues
• 3 types of muscle tissue– Skeletal muscle– _______ muscle– _____ muscle
• Trivia: about ____% of body mass is skeletal muscle in someone of “normal” height and weight
Unit 3 slide 4
Muscles
• A particular muscle, e.g., the biceps brachii, is an organ composed of skeletal muscle tissue, connective tissue, etc.
• “Muscular system” really refers to the ________ muscles
Unit 3 slide 5
Skeletal Muscle
• Connective tissues– ____mysium, around individual muscle
cells (muscle cells = muscle fibers)– ____mysium, around fascicles– ____mysium, around entire muscle, blends
into CT sheets called fascia
Unit 3 slide 6
Unit 3 slide 7
Skeletal Muscle• Attachment to bone
– ________ attachment – epimysium blends into periosteum
– __________ attachment – tendoncomposed of dense regular CT
– Aponeurosis – broad, flat tendon connecting muscle to muscle
Unit 3 slide 8
Origin & Insertion
• ______ – the muscle attachment at the relatively stationary end
• ________ – the muscle attachment at the more mobile end
• Example, triceps brachii– O: scapula, proximal humerus– I: olecranon
Unit 3 slide 9
Unit 3 slide 10
Skeletal Muscle Histology
• “_____” = flesh, so many terms in this unit have “sarco” in their name
• Sarcoplasm = cytoplasm• _________ reticulum
= modified endoplasmic reticulum• ________ = contractile unit
Unit 3 slide 11
Unit 3 slide 12
Sarcomere
• Functional unit of skeletal muscle• Thick filaments
– ______• Thin filaments
– _____– Troponin– __________
• Transverse tubules (T tubules)
Unit 3 slide 13
Thick and Thin Filaments
• Thick:– Myosin sort of looks
like a golf ____• Thin:
– “_____” of g-actin form a twisted pair of strands
– Troponin and tropomyosin attached
Unit 3 slide 14
Sarcomere
• A band• I band• H band • Z disc
• Sarcomere = Z disc to Z disc• Myofibril = many sarcomeres,
end to end
Unit 3 slide 15
Unit 3 slide 16
Contraction
• Occurs when myosin head groups pull on actin filaments
• Binding site blocked by _______– Ca+2 ions bind to troponin, troponin
changes shape and pulls tropomyosin out of the way
– Now myosin can get at the actin
Unit 3 slide 17
Unit 3 slide 18
Excitation-Contraction
Action potential hits T tubules and dives down into sarcoplasm
1. Voltage-gated Ca+2 channels open in terminal cisternae of SR, Ca+2 flows out of the SR and into the sarcoplasm
2. Ca+2 binds to troponinTroponin pulls tropomyosin away from
myosin binding sites on actin filaments
Unit 3 slide 19
Unit 3 slide 20
Excitation-ContractionMyosin-ATP complex hydrolyses ATP
to ADP and Pi (activation)
3. Myosin-ADP-Pi complex binds to actin
4. ADP and Pi float away (power stroke)
5. Myosin releases actin when new ATP binds to head group
Unit 3 slide 21
Unit 3 slide 22
Excitation-Contraction
Motor neuron stops releasing ACh
Acetylcholinesterase (AChE) clears ACh from synaptic cleft
Ca+2 pumped back into SR
Tropomyosin moves back to block the binding sites on the actin filaments
Unit 3 slide 23
Unit 3 slide 24
Muscle Metabolism
• Immediate energy sources– Use the O2 that’s already there in the muscle– Use myokinase and creatine kinase to make ATP
• Short-term energy sources– Emergency use only!– Anaerobic glycolysis (glycogen, lactic acid)
• Long-term energy sources– Back to aerobic cellular respiration as the
blood flow to the muscle increases– A marathon runner tries to go from immediate
energy to long-term energy without short-term
Unit 3 slide 25
Unit 3 slide 26
Unit 3 slide 27
Slow- & Fast-Twitch
• ____-twitch fibers (oxidative)– Endurance fibers, dark meat– Lots of myoglobin, mitochondria, capillaries
• ______-twitch fibers (glycolytic)– Run-away-from-the-tiger fibers, white meat– Low myoglobin and mitochondria,
not so many capillaries, plenty of glycogen
Unit 3 slide 28
Skeletal Muscle Shapes 1
Skeletal Muscle Shapes 2• ________ muscles
– thick in middle and tapered at ends– biceps brachii m.
• _________ muscles have parallel fascicles– rectus abdominis m.
• ___________muscle– broad at origin and tapering to a narrower insertion
• Pennate muscles– fascicles insert obliquely on a tendon– unipennate, bipennate or multipennate– palmar interosseus, rectus femoris and deltoid
• ________ muscles– ring around body opening– orbicularis oculi
Unit 3 slide 31
Cardiac Muscle
• Striated like skeletal muscle• Shorter cells, often branched• Only one nucleus per cell• ____________ discs between cells
Unit 3 slide 32
Unit 3 slide 33
Smooth Muscle
• One nucleus per cell• No visible _________• Contracts in response to changes
in the local environment– chemical stimuli (hormones, low O2, low pH, etc.)
– stretch (bladder,stomach)
• Or in response to ____________ nerve fibers
Unit 3 slide 34
Unit 3 slide 35
Smooth Muscle
• Still myosin pulling on actin, but not arranged in ______________
• Actin anchors to plasma membrane, twisted Nerf football effect
• Calmodulin: Ca+2 binding protein, sort of equivalent to troponin in skeletal muscle
Unit 3 slide 36