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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 (actinmyosin 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)
Larry M. Frolich, Ph.D.
• T-tubules penetrate into cell and contact sarcoplasmic reticulum
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
crossbridges
undergo
cycling
shape
change in
the
presence of
calcium
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
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
Shortening of actin-myosin units
lead to whole muscle contraction
•
•
•
Muscle cells all lined up in skeletal muscle
Contaction of many cells makes whole muscle shorten bringing about body
movements
Larry M. Frolich, Ph.D.
Movement happens across joints between skeletal elements
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 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
Joints
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
Medullary
cavity
• 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
Larry M. Frolich, Ph.D.
bone absorption on inside
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 no
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
Larry M. Frolich, Ph.D.
remedy
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 (actinmyosin 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
crossbridges
undergo
cycling
shape
change in
the
presence of
calcium
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Shortening of actin-myosin units
lead to whole muscle contraction
•
•
•
Muscle cells all lined up in skeletal muscle
Contaction of many cells makes whole muscle shorten bringing about body
movements
Larry M. Frolich, Ph.D.
Movement happens across joints between skeletal elements
Biology Department, Yavapai College
• 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
Joints
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 no
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
Larry M. Frolich, Ph.D.
remedy
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