Comparitive Biomechanics Exam 2

Viscosity

Relating to thickness; resistance to internal friction and change in shape

Turbulence

Chaotic movement in a fluid

Laminar Flow

Flowing parallel, smoothly at the same speed

Turbulent Flow

Flowing in many directions including swirls at different speeds

How does speed, size, and viscosity affect turbulence?

Increased speed, size, and density, paired with low viscosity results in more turbulence

Reynold’s Number

Reynold’s number describes the relationship between density, velocity, length, and viscosity of a fluid by measuring when it will be laminar or turbulent

Reynold’s Number Formula

Reynold’s Number Definitions

High number: Turbulent

Low number: Laminar

What does fluid flow depend on?

Speed, object size, fluid viscosity, and fluid density

What is laminar flow characterized by?

Slower speeds, smaller object size, high fluid viscosity, and low fluid density

What is turbulent flow characterized by?

Faster speeds, larger object size, low fluid viscosity, and high fluid density

Drag

A resistive force that acts opposite of the motion and object is moving through a fluid

What is necessary for flight?

Lift and thrust, in which the thrust is greater than drag and lift is greater than gravity

How do flight and swimming differ?

Lift is eliminated in swimming

Frictional Drag

When air sticks to the object that it is propelling, creating resistance opposite to the direction of motion

Vortex Drag

A form of pressure drag that results when vacuum like air swirls, due to a lack of forces pushing or pulling on the back of an object

How do birds fly?

They must lift and thrust simultaneously to achieve flight

Thrust

A forward and upward motion that overcomes drag in flight and swimming

Particle Velocimetry

Imaging technology that utilizes lights and lasers to aid in flow identification through the visualization of object movement (measurement of velocity and direction) through a fluid

Vortices

Fluid regions where flow is circular in motion, indicating turbulence

Hydrostatic Skeleton

Fluid filled object (tube) wrapped in muscle that enables movement

eg. worm

Hydrostatic Organ

Fluid filled object (tube) wrapped in connective tissue to prevent bending, that can inflate or deflate

eg. penis and fish swim bladder

Muscle Hydrostat

Muscle filled object (tube lacking fluid, in which the muscles move in all directions

eg. elephant trunk, tongue, and tentacles

Fluid Filled Systems

Hydraulic: Compressed fluid
Pneumatic: Compressed air

Where do the input forces come from for biological levers?

Muscles

Do all muscles work the same way?

Due to differing categorizations, smooth, cardiac, and skeletal, all muscles do not work the same way

Muscle Structure

Muscle, fascicles, muscle fiber, myofibril, sarcomere

Types of Skeletal Muscle

Circular, convergent (fan shaped), fusiform (tapering spindle), parallel

Pennate Skeletal Muscles

Feather-like compact muscles (a large number of muscle fibers in a compact space) that attach at a central tendon

Types of Pennate Skeletal Muscle

Unipennate: Connects to one side of a tendon

Bipennate: Connects to two sides of a tendon

Multipennate: Connects to multiple sides of a tendon

What trade offs do pennate muscles have?

They can be stronger, but have less ROM or speed

Parallel Skeletal Muscles

Muscles that run from one tendon to the other (end to end)

What is the significance of modeling movement?

It can provide visualizations of how muscles move and their strength, utilizing computer simulations

Can the stiffness of things change?

Yes, muscles can change in stiffness depending on how much the muscle flexes

• Amputees are the exception, although they can change the speed at which they move, they can not alter the stiffness of their legs

Feet Categorizations

Biped: Walk on two feet

Quadruped: Walk on four feet
Decapods: Walk on 10 feet → Crustaceans

Hexapods: Walk on 6 feet → Insects

Myriapoda: Walk on many feet → Millipede, centipede, etc.

Human locomotion is . . .

Very efficient

Examples of the efficient locomotion

Persistence hunting: Humans pursuing an animal until they are exhausted

• Dogs are similarly efficient

Aerobic Respiration Formula

What changes occur when shifting from walking to running?

Stride length and speed change

Plantigrade

Walking on the soles of the feet

Digitigrade

Walking on the toes and the ball of the feet

Unguligrade

Walking on the tips of the toes

What form of animal locomotion most efficient?

Hopping

List gait types and how they differ?

Walk, trot, canter, lope, gallop, and pace. These differ in the leg swing and ground contact pattern.

What do ground plates measure?

Locomotion output forces, or ground reaction forces

Inverse Dynamics

Uses dots on joints and video to track how body parts move, given this data force calculations can be estimated

Forward Dynamics

Given a skeleton, estimates of muscle forces and joint torques are acquired

Conservation of Momentum

Applies to Newton’s third law due to the trade off between mass and velocity, in which forces are equal and opposite (constant; neither created or destroyed)

Conservation of Momentum Trade-Off

Large mass = Slow velocity

Small mass = Fast velocity

Moment of Intertia

The ability to resist rotation relates to both Newton’s third law and the conservation of momentum

What concepts are related to cats landing on their feet?

Conservation of (Angular) Momentum

Moment of Inertia

• This also applies to satellite technology

Exaptation

When a preexisting trait changes to serve a new purpose, also known as pre-adaptation

• Eg. Feathers in dinosaurs for warmth, now used mating and flight in birds, and waterproofing in ducks

How can variation be explained?

By adaptation and constraint

Constraint

Factors limiting an organism, causing it to recycle a preexisting trait

• Traits are recycled because organisms cannot introduce new traits by themselves

Convergent Evolution

When unrelated or distantly related organisms evolve or adapt similarly

How are comparative and human biomechanics related?

They are interrelated, and studying either could aid in the understanding of the other

Adaptive Radiations

The rapid evolutionary diversification of a single ancestor into numerous species, each specialized to a distinct ecological niche

Directional Adaptation

A mode of natural selection favoring one phenotype over the others, occurring when organisms adapt in terms of their environment and ecological needs

• This is a driver of adaptive radiation

Vestigial

Body parts that are no longer serving a purpose, and is therefore reduced but still apparent

Why is biomechanics significant?

It can be used to make predictions about ecology, behavior, and evolution. However, it cannot fully inform the previous factors of an organism, thus other data is necessary