Biomechanics - Musculoskeletal system Flashcards
What are the components of the musculoskeletal system?
Skeletal system, synovial joints, muscular system
What is an endoskeleton?
When the bone and cartilage are buried within the soft tissue
What is the skeletal type in which organisms have a hard outer layer called?
Exoskeleton
What is the skeletal system?
Rigid levers
What is synovial joint?
the linkage system
What is the muscular system?
force production
What are the main functions of the skeletal system?
Hematopoiesis (red cell production), mineral storage (FYI particularly calcium and phosphorous), protection of vital organs (e.g. rib cage) and support and motion
How many new red blood cells are made every day?
~500 billion
How much of the bodies calcium is stored in the bones?
90%
How many bones does an adult human have?
206
How are our bones connected?
They are either fused or connected by joints (synovial joints)
How are joints characterised?
By they functional degrees of freedom
What does degrees of freedom refer to?
How many different directions joints can move
What are the tissues that make up human bones?
Cartilage, spongy bone, compact bone, central cavity, yellow bone marrow, fibrous connective tissue, blood vessels
What is spongy bone?
Porous structure
What are the structural properties of compact bone? what does it do?
It is dense and strong, provides structural support and produces red blood cells
What is yellow bone marrow?
Mostly fat cells
What is fibrous connective tissue?
Collagen fibres and cells producing new bone tissue
What is the structural strength of bone related to?
The microstructure alignment of cortical and trabecular spongy bone and the calcification of the spongy bones
What happens if the spongy bone is not well calcified?
It remains spongy and doesn’t have structural strength
What is Wolff’s law of bone remodelling?
Bone undergoes active remodelling in response to its local mechanic environment
How much bone remodels every year?
~10% a year
What are some examples of bone remodelling?
Humeral torsion in throwing athletes (e.g. bones in arm rotate to aid in throwing force), in microgravity bone density decreases
What is articular cartilage and what is its function?
Covers the end of bones and provides frictionless contact between the joints
What is the composition of articular cartilage?
70% water, 25% collage fibres and 5% proteoglycans
What are proteoglycans? What is their function?
- negatively charged molecules that retain water
- enable water to distribute forces more evenly in the articular cartilage, without these the collage fibres takes the load which results in insufficient padding for bone
What is the function of the collagen fibres?
Hold the cartilage together as there is so much water being held it is almost bursting
What is degeneration of the cartilage called?
osteoarthritis
How are skeletal muscles attached to the bone?
By tendons
What does muscle activity respond to?
inputs from the nervous system
What is the action of a muscle always?
to contract
What does skeletal muscles consist of? What is their arrangement? What are they surrounded by?
bundles of long muscle fibres that run parallel to the length of the muscles that are surrounded by connective tissue
How do muscle fibre cells differ from normal cells?
they don’t have a nucleus
What is each muscle fibre made of? What is their appearance?
Muscle fibres is made of smaller subunits of myofibrils and they have a striped/striated appearance
What creates the striped appearance of myofibrils?
alternation thick filaments and thin filaments
What are the thick and thin filaments?
Thick = Myosin protein Thin = actin protein
What do the repeating units of bands form? What is their function?
Sarcomeres and are the muscles contracting unit
What are the structures of skeletal muscle in decreasing size from muscle tissue?
Muscle tissue, fascicle (bundles of muscle fibres), muscle fibres, myofibril, sarcomere, thick and thin consign and actin filaments
What is the model used to describe how muscle contract? What is the basics of it?
Sliding filament model where thick and thin filaments slide past each other longitudinally
What is the process of muscle contraction via sliding filament model?
1 - ATP binding releases myosin from actin
2 - Myosin head goes from a low to a high energy state when ATP hydrolysis supplies energy changing its shape
3 - Myosin attaches to actin forming a cross-bridge
4 - Energy is used to slide acting filament and myosin return to low energy stat releasing ADP + P ion
How many times a second can a myosin head undergo this sliding filament model?
5 times per second
How many myosin heads does each thick filament have?
about 350 per filament
What is the optimal fibre length for a muscle? what does it mean?
It is where a muscle produces an optimal amount of force which occurs at its mid range of operating length
What happens when the muscle fibre is too short of long?
When muscle fibre is too short sarcomere can’t slide past each other
when it is too long it loses potential binding sites
How much force can muscle produce?
30N of force per cm2 of muscles
What makes the optimal fibre length the best length for maximum force?
It is where the maximum number of cross-bridges exist between myosin and actin
What is muscle force production proportional to?
The physiological cross-seciontal area (PCSA) of the muscle fibres (e.g. then umber of sarcomeres in parallel)_
How can muscle produce different force?
If it is undergoing active shortening or lengthening
When is the muscle moving at its fastest velocity?
When it is at zero muscle force
When is the muscle producing the least force?
When it is moving fastest
When is the muscle moving slowest and producing most force?
As the muscle is lengthening
Where is damage most likely to occur? what is this called?
When the muscle is lengthening, called hypertrophy
Why is producing the most speed when there is least power and vice verse?
When muscle contracts faster less cross bridges form between filament so less power, when muscle contracts slower more cross bridges form between filaments so more power
What is power?
Force X velocity
when does maximum power occur?
At a point around mediums velocity and medium force
What is the difference between ligaments and tendons?
Tendons transfer forces from muscle to bone
Ligaments connect bone to bone
What is the composition of tendons and ligaments?
~60% water
dry weight = ~75% collage, 1-3% elastin and 1-2% proteoglycan
What do both tendon and ligaments do?
resist tonsil loads (e.g. stretch)
How does the orientation of collagen fibre affect tendons and ligaments?
Determines the primary direction of tonsil resistance
What is mechanic behaviour mostly dependent of?
Cross-Sectional area (e.g. larger size = bigger cross sectional area)
What are the mechanical functions of tendons? give some figures
Store and return elastic energy during locomotion: return ~90% of energy used to stretch it which saves ~50% of metabolic cost
In skeletal loads, what are the calculations necessary to determine the forces exerted on the joints?
Fx = 0 Fy = 0 ∑M = 0
