Larry M. Frolich, Ph.D. Biology Department, Yavapai College Movement—muscle and bone Muscle...
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Transcript of Larry M. Frolich, Ph.D. Biology Department, Yavapai College Movement—muscle and bone Muscle...
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Movement—muscle and bone• Muscle structure and contraction• Movement across joints• Bones
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Movement—muscle and bone• Muscle structure and contraction• Movement across joints• Bones
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Overview• Neuron brings
impulse to synapse with muscle
• Muscle cells shorten by sliding protein filaments (actin-myosin units)
• Great in-depth molecular understanding of how muscle moves
• Movements at protein level cause whole muscle to rapidly shorten or contract
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Muscle cell structure• Muscle cells are large
—visible with naked eye as “fibers of meat/chicken/fish
• Each cell contains hundreds of myofibrils
• Each myofibril contains actin/myosin filamentous proteins all lined up (gives striated appearance in microscope)
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Parts of muscle cell
• Sarcolemma—muscle cell membrane (“excitable” membrane like neuron can generate action potential)
• Sarcoplasmic reticulum—endoplasmic reticulum in muscle (holds Ca+2 ions)
• T-tubules penetrate into cell and contact sarcoplasmic reticulum
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Calcium release in muscle
• Motor neuron impulse arrives to axonal terminus• Neuro-muscular junction synapse passes
message on to muscle cell• Sarcolemma (muscle cell membrane) undergoes
action potential all along length of cell membrane and into T-tubule system
• Voltage change causes release of Ca+2 ions into muscle cell
• Calcium causes actin-myosin units (sarcomeres) to shorten
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Sliding filament model• Thick
filaments (myosin) “row” or pull in thin filaments (actin)
• Molecular cross-bridges undergo cycling shape change in the presence of calcium
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Muscle contraction requires energy
• Three sources of energy, all part of cellular respiration
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
• Muscle cells all lined up in skeletal muscle• Contaction of many cells makes whole muscle shorten bringing about body
movements• Movement happens across joints between skeletal elements
Shortening of actin-myosin units lead to whole muscle contraction
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Movement—muscle and bone• Muscle structure and contraction
• Movement across joints• Bones
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Joints
• Joints connect skeletal elements
• Synovial joints are lubricated, mobile joints
• Skeletal elements linked by synovial joints move when muscles pull on those skeletal elements
• This is how movement happens
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Technical vocabulary for movement across joints—very specific
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Movement—muscle and bone• Muscle structure and contraction• Movement across joints
• Bones
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Structure of a bone
• Bone is alive• Has nerves, blood
supply, cells• Connective tissue
very organized in layers around blood vessels
• Cells make bone tissue, dissolve bone tissue, live inside bone tissue
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Fetal bone formation
• Cartilage model forms first• Then bony tissue fills in around blood vessels• Final bone has three parts: central shaft (diaphysis) and two
ends (epiphyses)
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Growth plate
• New bone tissue forms within cartilage• Bone growth occurs at cartilaginous growth plate
between diaphysis and epiphysis at either end of bone
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
• Inside of diaphysis is hollow tube called medullary cavity• In life filled with bone marrow, where blood cells form• Diameter of bone grows by bone formation around outside and
bone absorption on inside
Medullary cavity
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Calcium regulation and bone• Bone also serves as
calcium storage• Calcium is needed
for many aspects of cell metabolism, but especially in muscle cells
• Calcium regulation is negative feedback mechanism
• Release of calcium by degrading bone can be contrary to support role of bone
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Osteoporosis is result of calcium need outweighing bone support role
• Affects elderly, especially women• Bone resorption proceeds faster than deposition• Low estrogen levels implicated but estrogen replacement now
considered risky• Importance of calcium in diet???• Leads to fractures
– Compression fractures of vertebrae– Neck of femur
• Lifelong habit of weight-bearing activity is probably best remedy
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Total Movement Picture• Neurons trigger
muscle to contract based on stimuli or sensory input
• Muscle contracts by sliding filaments
• Muscle pulls on bone to cause movement across joint
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Movement—muscle and bone: Review• Muscle structure and contraction• Movement across joints• Bones
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Overview• Neuron brings
impulse to synapse with muscle
• Muscle cells shorten by sliding protein filaments (actin-myosin units)
• Great in-depth molecular understanding of how muscle moves
• Movements at protein level cause whole muscle to rapidly shorten or contract
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Muscle cell structure• Muscle cells are large
—visible with naked eye as “fibers of meat/chicken/fish
• Each cell contains hundreds of myofibrils
• Each myofibril contains actin/myosin filamentous proteins all lined up (gives striated appearance in microscope)
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Sliding filament model• Thick
filaments (myosin) “row” or pull in thin filaments (actin)
• Molecular cross-bridges undergo cycling shape change in the presence of calcium
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
• Muscle cells all lined up in skeletal muscle• Contaction of many cells makes whole muscle shorten bringing about body
movements• Movement happens across joints between skeletal elements
Shortening of actin-myosin units lead to whole muscle contraction
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Joints
• Joints connect skeletal elements
• Synovial joints are lubricated, mobile joints
• Skeletal elements linked by synovial joints move when muscles pull on those skeletal elements
• This is how movement happens
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Structure of a bone
• Bone is alive• Has nerves, blood
supply, cells• Connective tissue
very organized in layers around blood vessels
• Cells make bone tissue, dissolve bone tissue, live inside bone tissue
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Calcium regulation and bone• Bone also serves as
calcium storage• Calcium is needed
for many aspects of cell metabolism, but especially in muscle cells
• Calcium regulation is negative feedback mechanism
• Release of calcium by degrading bone can be contrary to support role of bone
Larry M. Frolich, Ph.D.Biology Department, Yavapai College
Osteoporosis is result of calcium need outweighing bone support role
• Affects elderly, especially women• Bone resorption proceeds faster than deposition• Low estrogen levels implicated but estrogen replacement now
considered risky• Importance of calcium in diet???• Leads to fractures
– Compression fractures of vertebrae– Neck of femur
• Lifelong habit of weight-bearing activity is probably best remedy