Thursday, July 12, 2007

Compendium Six – Body Movement: Muscles, Joints, and Bones

Katie Meyers

Compendium Six – Body Movement: Muscles, Joints, and Bones


  • Muscle names
  • Muscle movement overview
  • Muscle tissue
    • 3 types
  • Muscle fiber cell
  • Motor unit
  • Muscle’s 4 possible energy sources
  • Muscle cell – 3 ways they acquire ATP
  • Muscle twitch
  • Muscle fiber – 2 types
  • Calcium
  • Sliding filament model


  • Joints – 3 types
  • Technical joint movement names

Bones (and cartilage)

  • Skeletal system
    • 5 functions
  • Skeleton – 2 groups
  • Bone
  • Long bone anatomy
  • 3 cell types associated with bones
  • Bone growth
    • Ossification – 2 types
  • Bone remodeling
    • Medullary cavity
    • Calcium regulation
    • 2 hormones that regulate blood calcium level
    • Osteoporosis
  • Bone repair
    • 4 steps
  • Cartilage
    • 3 types

Movement Summary


  • Muscle names are derived from their…
    • Size
    • Shape
    • Location
    • Direction of muscle fibers
    • Attachment
    • Number of attachments
    • Action
  • Muscle can only pull, not push
  • Overview of muscle movement – “neuron brings impulse (or action potential) to synapse with muscle; muscle cells shorten by sliding protein filaments (actin-myosin units)” (found on slide 4 of Movement – BIO 156 PowerPoint presentation)

  • (found on slide 4 of Movement – BIO 156 PowerPoint presentation)
  • Tetanus – maximal sustained muscle contraction
  • Fatigue – when muscle relaxes, even though stimulation of that muscle continues
  • Muscle tissue

  • (found at
    • 3 types
      • Smooth muscle
        • Fibers are spindle-shaped cells
        • Not striated
        • Located in the walls of hollow internal organs
        • Involuntary contraction
      • Cardiac muscle
        • Forms heart wall
        • Striated, tubular, branched
        • Relaxes completely between contractions, preventing fatigue
        • Involuntary contraction
      • Skeletal muscle
        • Supports body
        • Striated
        • Makes bones move; contraction causes movement of bones at a joint
        • Helps maintain constant body temperature
          • Contraction causes ATP to break down
        • Contraction assists movement in cardiovascular and lymphatic vessels
        • Helps protect internal organs and stabilize joints
        • Work in pairs
        • Well organized
          • Contains fascicles (bundles of skeletal muscle fibers)
            • Each fascicle and each fiber of a fascicle are surrounded by connective tissue
        • Covered with connective tissue called fascia, which extends beyond muscle and becomes that muscle’s tendon (connecting to the appropriate nearby bone[s])
  • Muscle fiber cell

(found on slide 6 of Movement – BIO 156 PowerPoint presentation)

    • Large cells, visible with the naked eye
    • Sarcolemma – the plasma membrane that forms T tubules
      • An “excitable” membrane that can generate an action potential, just like neuron membranes do
    • T tubules – extend into muscle fiber, convey impulses causing calcium to be released from the sarcoplasmic reticulum
      • Penetrate into cell, contacts sarcoplasmic reticulum
      • Membrane extensions
      • Crucial in actin-myosin, or muscle, movement
    • Sarcoplasm – muscle cell’s version of cytoplasm; contains organelles, including myofibrils
    • Sarcoplasmic reticulum – made of smooth endoplasmic reticulum (ER) that has expanded portions that store calcium, which is essential for muscle contraction
      • A muscle cell/muscle fiber contracts when calcium leaves the sarcoplasmic reticulum, and relaxed when calcium returns to the sarcoplasmic reticulum.
    • Glycogen – stores energy for muscle contraction; is a polysaccharide
    • Myoglobin – red pigment; stores oxygen for muscle contraction
    • Myofilament – actin filament or myosin filament that are accountable for muscle striations and contractions
      • Thick filament – myosin proteins, shaped like a golf club
      • Think filament – actin proteins; tropomyosin and troponin are important to thin filament because they help myosin bind to actin
      • Sliding filament – movement of actin filament in relation to myosin filament
    • Myofibril – myofilament bundle that contracts
      • Each cell has hundreds of myofibrils
      • Each myofibril contains myofilaments and the actions they perform
  • Motor unit – a nerve fiber and all the muscle fibers it innervates
    • Obeys the all-or-none law
    • A whole muscle usually has many motor units
  • Muscle’s 4 possible energy sources
    • 2 stored in muscles
      • Glycogen
      • Fat (triglycerides)
    • 2 stored in blood
      • Blood glucose
      • Plasma fatty acids
  • Muscle cells – 3 ways they acquire ATP

    • (found on slide 10 of Movement – BIO 156 PowerPoint presentation)
    • Formation of ATP by creatine phosphate (CP) pathway
      • Anaerobic
      • Simplest, most rapid way to produce ATP
      • Consists of one reaction only, makes it very fast transaction
      • Used for high-intensity exercise over 5 seconds or less
    • Formation of ATP by fermentation
      • Anaerobic
      • Produces only 2 ATP
      • Pathway most likely to begin with glycogen
      • Fast-acting
      • Results in lactate buildup
    • Formation of ATP by cellular respiration
      • Aerobic; involves use of oxygen by mitochondria
      • Does not immediately supply ATP for muscle contraction
      • More likely to supply ATP when exercise is submaximal in intensity
  • Muscle twitch – single contraction that last only a fraction of a second
    • 3 stages
      • Latent period
      • Contraction period
      • Relaxation period
  • Muscle fiber – 2 types
    • Fast-twitch muscle fiber
      • Is anaerobic – uses primarily fermentation and CP pathway
      • Has explosive power
      • Fatigues easily
    • Slow-twitch muscle fiber
      • Is aerobic – prefers to use cellular respiration
      • Has steady power
      • Has endurance
  • Calcium – how it is released into muscle
    • 1) “Motor neuron impulse arrives to axonal terminus” (found on slide 7 of Movement – BIO 156 PowerPoint presentation)
    • 2) “Neuro-muscular junction synapse passes message on to muscle cell”; in other words, this is where the message is passed on (quote found on slide 7 of Movement – BIO 156 PowerPoint presentation)
    • 3) Sarcolemma has the action potential passed all along the cell membrane and into the T tubule system
    • 4) This voltage change then causes calcium to be released into the (muscle) cell
    • 5) As a result, the released calcium causes the sarcomeres, or actin-myosin units, to shorten
  • Sliding filament model

    • (found on slide 8 of Movement – BIO 156 PowerPoint presentation)
    • “Rowing” – the myosin, or thick, filaments pull on the actin, or thin, filaments
    • Calcium in sliding filaments
      • Binding calcium allows…
        • Myosin to undergo change (so it will interact with actin)
        • Cycling of molecular cross bridges what changes their shape
    • Uses ATP
    • Here is an image portraying the importance and use of ATP and calcium in sliding filaments

    • (found on slide 9 of Movement – BIO 156 PowerPoint presentation)
    • Muscle cells are lined up in skeletal muscle. When many of them contract simultaneously, the whole muscle shortens and brings about body movement.


  • “Movement happens across joints between skeletal elements” (from slide 11 of Movement – BIO 156 PowerPoint presentation)
  • “Joints connect skeletal elements” (from slide 13 of Movement – BIO 156 PowerPoint presentation)
  • Joints – 3 types
    • Fibrous – immovable; e.g. sutures between cranial bones
    • Cartilaginous – slightly moveable, connected by hyaline cartilage (e.g. costal cartilage that joins ribs to sternum) or fibrocartilage (e.g. intervertebral disks)
    • Synovial – freely moveable, has a cavity filled with synovial fluid (lubricates joint)

      • (found on slide 13 of Movement – BIO 156 PowerPoint presentation)
      • Generalized synovial joint – e.g. knee
      • Ball-and-socket joins – e.g. shoulder
      • Hinge joint – e.g. elbow
      • “Skeletal elements linked by synovial joints move when muscles pull on those skeletal elements; this is how movement happens” (from slide 13 of Movement – BIO 156 PowerPoint presentation)
  • Technical names for specific movements across joints

  • (found on slide 14 of Movement – BIO 156 PowerPoint presentation)

Bones (and cartilage)

· Skeletal system

o 206 bones in the adult body

o Fibrous connective tissue makes up the ligaments and tendons that hold it together

o 5 functions

§ Supports body

§ Protects soft body parts

§ Produces blood cells

§ Stores minerals and fat

§ Permits flexible body movement when combined with muscle

· Skeleton – 2 groups

· (found at

o Axial skeleton

§ Skull – cranium, facial boned

§ Hyoid bone – only bone in body that does not articulate with another bone

· Attached to temporal bones and muscle and ligament

· Attached to larynx by a membrane

§ Vertebral column – 33 vertebrae

· 4 curvatures – this makes it stronger than it would be if it were a straight column

§ Rib cage (thoracic cage) – thoracic vertebrae, ribs (12 pairs) and their associated cartilages, sternum

o Appendicular skeleton – bones within the pectoral and pelvic girdles and their attached limbs

§ Pectoral girdle, left and right – scapula and clavicle

· Upper limb

o Arm – humerus

o Forearm – radius and ulna

o Hand – carpals, metacarpals, phalanges

§ Pelvic girdle, left and right – coxal bones

· Lower limb

o Thigh – femur (longest and strongest bone in the body)

o Leg – tibia and fibula

o Foot – tarsals, metatarsals, phalanges

· Bone – a tissue with nerve and blood supplies and cells

o Primary calcium storage site (calcium needed for muscle contraction)

o Compact bone

§ Highly organized

§ Composed into osteons (tubular units)

· Osteocytes live in lacunae

o Tiny chambers in concentric circles around a central canal

· Matrix fills rest of space between

o Spongy bone

§ Unorganized appearance

§ Contains trabeculae (thin plates) that are unequally spaced

§ Spaces filled with red bone marrow

§ Also has osteocytes in trabeculae

· Long bone anatomy

o (found on slide 16 of Movement – BIO 156 PowerPoint presentation)

o Shaft (main part) called diaphysis

§ Large medullary cavity

· Lined with endosteum (thin, vascular membrane)

· Filled with yellow bone marrow (stores fat)

o Expanded region at the end (epiphysis)

§ Composed mostly of spongy bone

§ Coated with thin layer of hyaline cartilage (also called articular cartilage in this case, because it is at a joint)

o Covered with periosteum (fibrous connective tissue)

o Cartilage is at the ends of the bone

o Growth plate – between diaphysis and epiphysis at both bone ends

§ Cartilaginous growth plate – where bone growth occurs

· (found on slide 18 of Movement – BIO 156 PowerPoint presentation)

· 3 cell types associated with bones

o Osteoblasts – bone-forming cells

o Osteocytes – mature bone cells derived from osteoblasts

o Osteoclasts – bone-absorbing cells

· Bone growth

o Ossification – the formation of bone

§ 2 types during skeletal formation in embryonic development

· Intramembranous ossificaction FIND ONLINE PIC

o Bones develop between sheets of fibrous connective tissue

o Develops only flat bones, e.g. skull

· Endochondral ossificiation

o Most human bones formed this way

o Bone replaces cartilaginous bone models

o (found on slide 17 of Movement – BIO 156 PowerPoint presentation)

o 5 steps/parts

§ Cartilage model – made by hyaline cartilage being laid down by chondrocytes in future bone’s shape

· Eventually chondrocytes die off

§ Bone collar – newly formed periosteum makdes osteoblasts

· Osteoblasts secrete organic bone matrix, which begins to calcify

§ Primary ossification center – osteoblasts brough to interior of bone by blood vessels; osteoblasts begin to make spongy bone

· The first bone formation center in the bone

§ Medullary cavity and secondary ossification sites

· Spongy bone of diaphysis is absorbed by osteoclasts

o This results in the medullary cavity

· Secondary ossification centers from in epiphyses shortly after birth

§ Epiphyseal (growth) plate

· Cartilage band between primary ossification center and each secondary ossification center

· 4 layers (starting nearest to the epiphysis)

o Resting zone – where cartilage remains

o Proliferating zone – produces new cartilage cells

o Degenerating zone – cartilage dies off here

o Ossification zone – where bone forms

· Bone remodeling – when bones change in size, shape, and/or strength due to stress; e.g. bone fractures, after which it heals

o 18% of bone is recycled each year in the body

o Keeps bones strong

o Why bones respond to stress: medullary cavity

§ (found on slide 19 of Movement – BIO 156 PowerPoint presentation)

§ Located in diaphysis

§ Hollow tube filled with bone marrow

§ Where blood and nerves are in the bone

§ This structure makes the bone stronger than it would be if it were a solid bone through and through

o Allows body to regulate amount of calcium in the blood

§ Bones store calcium

o 2 hormones regulate blood calcium level

§ Parathyroid hormone (PTH)

· Accelerates bone recycling

§ Calcitonin

· Opposite action of PTH

§ Calcium regulation negative feedback system

o (found on slide 20 of Movement – BIO 156 PowerPoint presentation)

o Osteoporosis – comes from the calcium need outweighing the bone support role

§ Affects elderly, particularly females

§ Happens when bone resorption happens faster than deposition

§ Possibly from low estrogen levels

§ Leads to higher fracture incidence, especially in hip, vertebrae, long bones, pelvis

§ Remedies

· Estrogen treatments tried, and now discouraged because of its link to higher cancer rates

· Keep calcium in the diet, especially green leafy calcium, which is considered better for a person than dairy calcium

o Also, make sure person has enough vitamin D, as it aids body in correctly using its calcium

· Best remedy – lifelong habit of activity (particularly weight-bearing)

§ Here is an image of an osteoporotic bone on the left and a healthy bone on the right

· (found on slide 21 of Movement – BIO 156 PowerPoint presentation)

· Bone repair

o 4 steps

§ Hematoma – after fracture, blood forms clotted blood mass at the space of bone break; takes 6-8 hours

§ Fibrocartilaginous callus – tissue repair beings, fibrocartilaginous callus forms at the break; takes 3 weeks

§ Bony callus – osteoblasts…

· Produce trabeculae of spongy bone

· Convert fibrocartilage callus to bony callus (joins bones together again)

§ Remodeling – osteoblasts build new compact bone at the periphery, while osteoclasts absorb spongy bone

· Cartilage

o Not as strong as bone, more flexible

o Made of chondrocyte cells

§ Are irregularly grouped in lacunae

o Has no nerves or blood vessels

o 3 types

§ Hyaline cartilage – firm, somewhat flexible

§ Fibrocartilage – stronger than hyaline cartilage; able to withstand tension/pressure

§ Elastic cartilage – more flexible than hyaline cartilage

Movement Summary

1. “Neurons trigger muscle to contract based on stimuli or sensory input”

2. “Muscle contracts by sliding filaments”

3. “Muscle pulls on bone to cause movement across joint”

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Studying for Bio

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