Biomechanics - Musculoskeletal system

Question 1

What are the components of the musculoskeletal system?

Answer 1

Skeletal system, synovial joints, muscular system

Question 2

What is an endoskeleton?

Answer 2

When the bone and cartilage are buried within the soft tissue

Question 3

What is the skeletal type in which organisms have a hard outer layer called?

Answer 3

Exoskeleton

Question 4

What is the skeletal system?

Answer 4

Rigid levers

Question 5

What is synovial joint?

Answer 5

the linkage system

Question 6

What is the muscular system?

Answer 6

force production

Question 7

What are the main functions of the skeletal system?

Answer 7

Hematopoiesis (red cell production), mineral storage (FYI particularly calcium and phosphorous), protection of vital organs (e.g. rib cage) and support and motion

Question 8

How many new red blood cells are made every day?

Answer 8

~500 billion

Question 9

How much of the bodies calcium is stored in the bones?

Answer 9

90%

Question 10

How many bones does an adult human have?

Answer 10

206

Question 11

How are our bones connected?

Answer 11

They are either fused or connected by joints (synovial joints)

Question 12

How are joints characterised?

Answer 12

By they functional degrees of freedom

Question 13

What does degrees of freedom refer to?

Answer 13

How many different directions joints can move

Question 14

What are the tissues that make up human bones?

Answer 14

Cartilage, spongy bone, compact bone, central cavity, yellow bone marrow, fibrous connective tissue, blood vessels

Question 15

What is spongy bone?

Answer 15

Porous structure

Question 16

What are the structural properties of compact bone? what does it do?

Answer 16

It is dense and strong, provides structural support and produces red blood cells

Question 17

What is yellow bone marrow?

Answer 17

Mostly fat cells

Question 18

What is fibrous connective tissue?

Answer 18

Collagen fibres and cells producing new bone tissue

Question 19

What is the structural strength of bone related to?

Answer 19

The microstructure alignment of cortical and trabecular spongy bone and the calcification of the spongy bones

Question 20

What happens if the spongy bone is not well calcified?

Answer 20

It remains spongy and doesn’t have structural strength

Question 21

What is Wolff’s law of bone remodelling?

Answer 21

Bone undergoes active remodelling in response to its local mechanic environment

Question 22

How much bone remodels every year?

Answer 22

~10% a year

Question 23

What are some examples of bone remodelling?

Answer 23

Humeral torsion in throwing athletes (e.g. bones in arm rotate to aid in throwing force), in microgravity bone density decreases

Question 24

What is articular cartilage and what is its function?

Answer 24

Covers the end of bones and provides frictionless contact between the joints

Question 25

What is the composition of articular cartilage?

Answer 25

70% water, 25% collage fibres and 5% proteoglycans

Question 26

What are proteoglycans? What is their function?

Answer 26

- 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

Question 27

What is the function of the collagen fibres?

Answer 27

Hold the cartilage together as there is so much water being held it is almost bursting

Question 28

What is degeneration of the cartilage called?

Answer 28

osteoarthritis

Question 29

How are skeletal muscles attached to the bone?

Answer 29

By tendons

Question 30

What does muscle activity respond to?

Answer 30

inputs from the nervous system

Question 31

What is the action of a muscle always?

Answer 31

to contract

Question 32

What does skeletal muscles consist of? What is their arrangement? What are they surrounded by?

Answer 32

bundles of long muscle fibres that run parallel to the length of the muscles that are surrounded by connective tissue

Question 33

How do muscle fibre cells differ from normal cells?

Answer 33

they don't have a nucleus

Question 34

What is each muscle fibre made of? What is their appearance?

Answer 34

Muscle fibres is made of smaller subunits of myofibrils and they have a striped/striated appearance

Question 35

What creates the striped appearance of myofibrils?

Answer 35

alternation thick filaments and thin filaments

Question 36

What are the thick and thin filaments?

Answer 36

``` Thick = Myosin protein Thin = actin protein ```

Question 37

What do the repeating units of bands form? What is their function?

Answer 37

Sarcomeres and are the muscles contracting unit

Question 38

What are the structures of skeletal muscle in decreasing size from muscle tissue?

Answer 38

Muscle tissue, fascicle (bundles of muscle fibres), muscle fibres, myofibril, sarcomere, thick and thin consign and actin filaments

Question 39

What is the model used to describe how muscle contract? What is the basics of it?

Answer 39

Sliding filament model where thick and thin filaments slide past each other longitudinally

Question 40

What is the process of muscle contraction via sliding filament model?

Answer 40

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

Question 41

How many times a second can a myosin head undergo this sliding filament model?

Answer 41

5 times per second

Question 42

How many myosin heads does each thick filament have?

Answer 42

about 350 per filament

Question 43

What is the optimal fibre length for a muscle? what does it mean?

Answer 43

It is where a muscle produces an optimal amount of force which occurs at its mid range of operating length

Question 44

What happens when the muscle fibre is too short of long?

Answer 44

When muscle fibre is too short sarcomere can't slide past each other when it is too long it loses potential binding sites

Question 45

How much force can muscle produce?

Answer 45

30N of force per cm2 of muscles

Question 46

What makes the optimal fibre length the best length for maximum force?

Answer 46

It is where the maximum number of cross-bridges exist between myosin and actin

Question 47

What is muscle force production proportional to?

Answer 47

The physiological cross-seciontal area (PCSA) of the muscle fibres (e.g. then umber of sarcomeres in parallel)_

Question 48

How can muscle produce different force?

Answer 48

If it is undergoing active shortening or lengthening

Question 49

When is the muscle moving at its fastest velocity?

Answer 49

When it is at zero muscle force

Question 50

When is the muscle producing the least force?

Answer 50

When it is moving fastest

Question 51

When is the muscle moving slowest and producing most force?

Answer 51

As the muscle is lengthening

Question 52

Where is damage most likely to occur? what is this called?

Answer 52

When the muscle is lengthening, called hypertrophy

Question 53

Why is producing the most speed when there is least power and vice verse?

Answer 53

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

Question 54

What is power?

Answer 54

Force X velocity

Question 55

when does maximum power occur?

Answer 55

At a point around mediums velocity and medium force

Question 56

What is the difference between ligaments and tendons?

Answer 56

Tendons transfer forces from muscle to bone | Ligaments connect bone to bone

Question 57

What is the composition of tendons and ligaments?

Answer 57

~60% water | dry weight = ~75% collage, 1-3% elastin and 1-2% proteoglycan

Question 58

What do both tendon and ligaments do?

Answer 58

resist tonsil loads (e.g. stretch)

Question 59

How does the orientation of collagen fibre affect tendons and ligaments?

Answer 59

Determines the primary direction of tonsil resistance

Question 60

What is mechanic behaviour mostly dependent of?

Answer 60

Cross-Sectional area (e.g. larger size = bigger cross sectional area)

Question 61

What are the mechanical functions of tendons? give some figures

Answer 61

Store and return elastic energy during locomotion: return ~90% of energy used to stretch it which saves ~50% of metabolic cost

Question 62

In skeletal loads, what are the calculations necessary to determine the forces exerted on the joints?

Answer 62

``` Fx = 0 Fy = 0 ∑M = 0 ```