biomechanics second half

Four types of tissue

Nervous and Epithelial and Muscle and Connective

Motor unit

A motor unit is made up of a motor neuron and the skeletal muscle fibers innervated by that motor neuron’s axonal terminals

Motor pool

All the motor units within a muscle are considered a motor pool

Behavioral properties of muscle

Extensibility and Elasticity and Irritability and Ability to develop tension and Contraction

Contraction concept for skeletal muscle

When a sarcomere contracts the Z lines move closer together and at full contraction the thin actin and thick myosin filaments overlap

Concentric

Shortening

Eccentric

Lengthening

Isotonic

Constant force

Isometric

Constant length static

Active force

Force generated by the contractile element

Passive force

Force generated by the spring and damper and appears when the muscle is lengthening

Contractile element

Models the active contraction in muscle

Spring and damper

Models the elastic tissue in the muscle that resists contraction

Tendon spring

Models the elastic tissue in tendons

Joint definition

A point of contact between two bones or between two cartilages or between bone and cartilage or between bone and teeth

Fibrous joint

Immobile and connecting bones without synovial cavity example skull and pelvis

Cartilaginous joint

Slightly movable but no synovial cavity and attached by cartilage example vertebrae and ribs

Synovial joint

Presence of synovial cavity example limb

Synovial joints

Filled with synovial fluid and allow diverse range of smooth movements

Synovial joint types

Hinge and Saddle and Plane and Pivot and Ball and socket and Ellipsoid

Planar joint gliding joint

Articulating surface is typically flat or slightly curved and allows gliding and movement is limited and you cannot rotate this joint and examples include carpal bones in the hand and vertebrae and tarsal bones of the feet

Hinge joint

Allows angular movement of one bone while the other remains stationary and example is the elbow

Pivot joint

Permits rotational movement and example is the first and second vertebrae of the neck

Connective tissue definition

Group of tissues in the body that maintain the form of the body and its organs and provide cohesion and internal support

Bone function

Provides a rigid skeletal framework that supports and protects other body tissues and forms a system of rigid levers moved by forces from attaching muscles

Bone material constituents

Calcium carbonate and calcium phosphate give bone stiffness and are primary determinants of compressive strength and Collagen provides flexibility and contributes to tensile strength and Water contributes to bone strength and carries nutrients and waste for living bone cells

Bone structural organization Cortical bone

Porosity is low with 5 to 30 percent of bone volume occupied by nonmineralized tissue

Bone structural organization Trabecular bone

Porosity is high with 30 to 90 percent of bone volume occupied by nonmineralized tissue

Biomechanical properties of bone

Cortical bone is stiffer so it withstands greater stress but less strain than trabecular bone and trabecular bone undergoes more strain before fracturing

Structure function relationship of bone

Function determines structure and shafts of long bones are strong cortical bone and vertebrae have relatively high trabecular content for shock absorbing and both cortical and trabecular bone are anisotropic and bone is strongest in compression and weakest in shear

Short bones definition

Approximately cubical and include carpals and tarsals hands and feet

Flat bones definition

Protect underlying organs and soft tissues and provide large areas for muscle and ligament attachments

Irregular bones definition

Different shapes to fulfill special functions in the body

Long bones definition

Form framework of appendicular skeleton and have a long roughly cylindrical shaft of cortical bone with bulbous ends and contain a medullary cavity

Shoulder five articulations

The shoulder includes five separate articulations which are the glenohumeral joint and the sternoclavicular joint and the acromioclavicular joint and the coracoclavicular joint and the scapulothoracic joint

Glenohumeral joint

Articulation between head of humerus and glenoid fossa of scapula and is a ball and socket joint

Sternoclavicular and acromioclavicular joints

Provide mobility for the clavicle and the scapula which are the bones of the shoulder girdle

Elbow structure

The elbow encompasses three articulations which are the humeroulnar joint and the humeroradial joint and the proximal radioulnar joint and all are enclosed in the same joint capsule which is reinforced by radial collateral and ulnar collateral ligaments

Spine vertebrae count and regions

Spine consists of a curved stack of 33 vertebrae which include 7 cervical and 12 thoracic and 5 lumbar and 5 fused sacral and 4 fused coccygeal

Spine range of motion

Flexion and extension and hyper extension and lateral flexion and rotation

Motion segment definition

Functional unit of spine composed of two adjacent vertebrae and associated soft tissues

Facet joints

Limit range of motion and channel movement and assist in load bearing to resist rotational torsion and shear and sustain up to approximately 30 percent of compressive loads especially in hyperextension and are synovial gliding joints

Intervertebral disc definition and makeup

Intervertebral disc is made up of annulus fibrosus and nucleus pulposus

Intervertebral disc biomechanics

Annulus acts as a coiled spring and nucleus pulposus acts like a ball bearing composed of an incompressible gel and flexion extension and lateral flexion produce compression on one side and tension on the other and rotation creates shear stress

Spine loads

Line of gravity passes anterior to vertebral column producing forward torque and upright standing produces shear and compression components on lumbar spine

Kyphosis

A spinal disorder in which an excessive curve results in abnormal rounding of the upper back

Scoliosis

A sideways curvature of the spine that occurs most often during the growth spurt just before puberty

Types of scoliosis

Idiopathic adolescent and Congenital and Neuromuscular and Adult de novo

Forms of motion

Linear motion is all parts moving same direction at same speed at any instant and Angular motion is all parts moving in circles in same direction at same time and General motion is a combination of linear and angular motion and is most common in the human body

Complexity of human movement keywords

3 linear axes and 3 angular axes equals 6 degrees of freedom and movement can occur at multiple joints at same time and force production varies with muscle length and contraction velocity and activation

Linear kinematics and human movement

Kinematics describes geometry and pattern of motion with respect to time and Kinetics describes forces associated with motion

Distance

Scalar measure of length traveled between initial and final point

Displacement

Vector measure of length traveled between initial and final point

Speed

Scalar measure of how fast an object is moving

Velocity

Vector measure of how fast an object is moving

Acceleration

Measure of rate of change in velocity

Galileo constant acceleration equations

v2 = v1 + a t and d = v1 t + (1/2) a t^2 and v2^2 = v1^2 + 2 a d

Projectile motion definition

Object projected at an angle with a given velocity and continues through influence of gravity only

Analyzing projectile motion steps

Determine appropriate kinematic equations then decompose initial velocity into horizontal and vertical components then create a table for all kinematic variables then plug values into equations to solve missing variables

Projectile motion under gravity

ax = 0 and ay = -g and vx = v0x and vy = v0y - g t

Three mechanical factors for projectile motion

Initial projection velocity and projection angle relative to horizontal and projection height

Angular displacement

Change in angular position or orientation of a line segment

Rotation sign convention

Counterclockwise is positive and clockwise is negative

Angular speed

σ = φ / Δt

Angular velocity

ω = θ / Δt

Angular acceleration

α = Δω / Δt

Curvilinear distance

s = r × angular distance

Linear velocity

V = r × ω

Tangential acceleration

a_t = r α

Radial acceleration

a_r = v^2 / r

Newtons first law

When no external forces act an object at rest remains at rest and if in motion continues at constant velocity

Newtons second law

When an unbalanced external force acts the object accelerates directly proportional to force and inversely proportional to mass

Newtons third law

Action induces reaction equal magnitude and opposite direction

Friction definition

Friction is the force that resists relative motion or tendency toward motion between two surfaces

Maximum static friction

Static friction increases as applied force increases until max static friction is reached then object begins to move and kinetic friction acts

Static vs kinetic friction

μs > μk

Friction reaction

If net force has vertical component it changes vertical reaction force which changes friction force accordingly

Linear momentum definition

Vector product of a body’s mass and velocity

Linear momentum equation

p = m v

Conservation of momentum

Total momentum in an isolated system is constant

Change of linear momentum

Δp = p2 - p1

Linear impulse definition

Product of force and time and equal to change in momentum

Linear impulse equation

F t = Δp

Angular impulse definition

Product of torque and time is equal to change in angular momentum

Angular impulse equation

T t = Δ(I ω)

Work definition

Force applied over a distance

Work equation

W = F d

Power definition

Rate at which work is done

Power equations

P = W / Δt and P = F d / Δt and P = F v

Kinetic energy definition

Energy due to motion

Kinetic energy equation

KE = (1/2) m v^2

Potential energy definition

Energy due to position

Potential energy equation

PE = m g h

Conservation of mechanical energy

PE + KE = constant

Principle of work and energy

Work done by all external forces acting on a system equals change in total system energy

Principle of work and energy equation

W = ΔPE + ΔKE + ΔTE

Torque definition

Torque is the moment of a force

Torque depends on

Depends on magnitude of force and moment arm

Moment arm definition

Perpendicular distance between force line of action and axis of rotation

Torque equation

T = r F sin(θ)