Biomechanics Exam 3

Stress is defined as the __.

Force per area

Identify the true statement

Increasing the surface area over which a force is distributed decreases the amount of stress acting on the surface

Which of the following terms is defined as the deformation in shape or size of an object due to externally applied forces?

Strain

which of the following types of forces exerts a sliding effect on the body acted upon?

Shear

In the figure below, which of the following best describes the mechanical stress that is observed at the analysis plane? (image of hanging from a bar - humerus)

Tension

In the figure below, which of the following best describes the mechanical stress that is observed at the analysis plane? (image of high plank - humerus)

Compression

As a bone is bent, which of the following best describes the combination of mechanical stresses that occur in the bone at the analysis plane?

compression on the low side, tension on the high side

The slope of the linear portion of a stress-strain curve represents which term?

Elastic modulus

A material exhibits a steeper slope on its stress-strain curve when it is stiffer.

True

When a stretched material does not return to its original shape, it is called

plastic

When a stretched material returns to its original shape, it is called

elastic

The point on the stress-strain curve where further stress will cause permanent deformation is called the yield point.

True

Considering the viscoelastic properties of biological tissue, stiffness is __ when the load is applied rapidly

greater

Muscle tissue under a constant stress will result in a __ in strain over time

increase

Muscle tissue will undergo __ when in a constant position.

stress relaxation

Bones are __, meaning that they do not have the same mechanical properties in every direction.

anisotropic

which of the following terms is used to describe bone with relatively high porosity?

cancellous

Bone is stronger in compression than it is in tension.

True

The axial skeleton comprises the extremities, shoulder girdle, and pelvis.

False

The functions of the skeletal system include

Blood cell formation, support, protection

The scapula is an example of a __ bone

flat

The type of joint that allows for the greatest range of motion is called

diarthrodial

The shoulder joint is an example of a __ joint.

ball-and-sockett

Organize the following muscular tissues from most internal to most external.

1. whole muscle

2. fascicle

3. myofibril

4. muscle fiber

3-4-2-1

The basic contractile unit of muscle is __

sarcomereW

which area in the sarcomere contains thick myosin filaments but no thin actin filaments?

H zone

which area in the sarcomere just contains actin filaments?

I bandWhe

When the sarcomere contract

the perimysium is a connective tissue that surrounds __

the fascicles

Based on the alignment of the fibers in the muscle pictured below, the figure is a representation of a __ muscle

bipennate

Generally, parallel muscles can change their length by a greater percentage than pennate muscles

true

generally, parallel muscles can generate more tension compared to similarly sized pennate muscles

falseten

tension developed in muscle depends on

number of crossbridges in contacts, length of the sarcomere, passive tension in the muscle

muscles can exert greater forces during concentric contractions than in isometric contractions

falsea

according to the force-velocity relationship, more tension (force) can be produced by a muscle concentrically when the velocity of shortening is

slow

which of the following types of contractions develops the greatest force?

eccentric

type I muscle fibers have a faster rate of tension development than type IIb muscle fibers

falseThe

the central nervous system consists of

the brain and the spinal cordthe

the peripheral nervous system consists of

all the nervous tissue outside the brain and spinal column

Afferent neurons carry sensory information from muscle to the central nervous system

true

A single motor neuron and all the muscle fibers with which it synapses define

a motor unit

muscles where fine control of force is needed have greater muscle fibers per motor unit

false

When a threshold level for activation is reached by the motor neuron of a specific motor unit,k all of the muscle fibers in the motor unit are activated. This is known as

the all-or-none principle

the size of the force produced in a whole-muscle contraction can be controlled by

altering the number of active motor units, altering the rate of stimulation

the complete summation of twitches is called

tetanus

when a muscle is stretched quickly, the resulting stretch reflex causes the

muscle to contract

slow stretch of a muscle initiates a larger stretch reflex response than a fast stretch

false

what reflex initiated during the backswing is critical in enhancing performance on a forehand drive in tennis?

stretchi

In response to increased tension in a muscle, the reflex action initiated by the golgi tendon organ tends to cause the

muscle to relax

Identify the statement below that is NOT true

EMG is typically used to measure heart function