KNR 282 Exam 4 ISU Marcel

I GPa

1,000,000,000 Pa

1MPa

1,000,000 Pa

1 m2 (cm)

10,000 cm2

1 m2 (mm)

1,000,000 mm2

Mechanical Stress

Internal force (F) divided by the cross-sectional area (A) of the surface on which the internal force acts

Tension

F tends to pull molecules apart causing axial stress.

Compression

F tends to push molecules more tightly together causing axial stress

Shear

F acting parallel cause transverse stress

Changes in orientation of object's molecules​, Measured as a change in angle (Do not worry about the equation)​

Linear

Changes in object's length

Elastic Response

Positively Linear​, Reaction to small loads

Plastic Response

Curvilinear​, Object deformation​, Yield Point: Point where further increases in stress will cause deformation

Steeper slope

Larger elastic modulus​, Stiffer material

Gradual slope

Smaller elastic modulus​, Compliant material

Yield strength

If + Stress = plastic deformation = no regain in shape

Ultimate strength

Total load that can be carried

Failure Strength

Stress corresponding to the end of the stress-strain curve, Usually the same value as ultimate strength

Skeletal Muscle

Active​

Passive​

Anisotropic​

Isotropic​

Bones

Passive​, Anisotropic​, Strength: compressive stress, Weakness: shear stress

Cartilage

Passive​, Anisotropic​, Strength: tensile stress, Weakness: compressive stress

Tendons and Ligaments

Passive​, Anisotropic​, Strength: tensile stress, Weakness: compression and shear stress

Axial Skeleton

(74 bones)​

Skull, vertebral column, and rib cage

Appendicular Skeleton

(126 bones)​

Shoulder girdle - clavicle and scapula​

Pelvic bones - ilium, ischium, and pubis​

Extremities - femur, humerus, tibia, fibula, radius, ulna, etc

Long bones

Humerus, radius, ulna, femur, tibia, fibula, metacarpals, metatarsals, phalanges, and clavicle​

Most involved in motion

Short bones

Carpals and tarsals (wrist and ankle)

Flat bones

Ribs, skull, scapula, sternum, and pelvic bones

Irregular bones

Vertebrae, sacrum, coccyx, and facial bones

Sesamoid bones

Bones that develop in tendons (i.e., patella)

Fibrous (sutures and syndesmoses)

Usually rigid ​

Sutures of the skull

Cartilaginous (synchrondroses)

Joined by cartilage; ​

Rigid or slight movement ​

Pubic symphysis

Synovial

Most common ​

Connected by ligaments​

Joint cavity

Synarthrodial

immovable ​

Fibrous

Amphiarthrodial

slightly movable​

Cartilaginous

Diarthrodial

freely movable​

Synovial

Macrostructure

Muscle​

Fascicle​

Muscle Fiber​

Myofibril​

Myofilaments

Microstructure

Muscle fiber = myocyte = muscle cell​

Sarcolemma​

Conducts electrical impulses​

Myofibrill​

Sarcomere​

Contractile structural unit (z-line to z-line)​

Contains actin and myosin

Connective tissue sheaths

Epimysium (covers whole muscle)​

Perimysium (covers fasciculi)​

Endomysium (covers muscle fiber)

Neurons

Fundamental unit of the nervous system

Dendrites

Branched region where neuron receives connections from other neurons

Soma (cell body)

Contains the nucleus and other organelles

Axon

Long projection from the soma. Carries action potentials (APs) to the terminals

Axon hillock

Final point that summated potentials propagate to. Action Potentials (APs) start here​​

Sensory (afferent)

Peripheral nervous system​

Cell bodies lie outside the CNS​

Interface with interneurons or motor neurons

Motor (efferent)

Central nervous system​

Cell bodies lie within the CNS​

Receive signals from sensory, interneurons, and higher efferent neurons

Interneurons (connector)

Central nervous system

Motor Unit

Motor neuron and the muscle fibers that it innervates. Each neuron is responsible for activating its own muscle fibers

"All or None" Principle

IF... ​MN activated by brain ​

THEN...​ ALL innervated muscle fibers by MN get activated

Golgi tendon organs (GTOs)

Function: To detect changes in musculotendinous tension, Provides joint stability

GTOs located in myotendinous regions

When muscle & tendon are under too much tension, GTOs cause inhibition of the muscle​

Type Ib afferent fibers interneuron(s) motor neuron​

Inhibits motor neurons going to that muscle (i.e. agonist)​

Excites motor neurons going to the antagonist

Improve Technique, Description

Describe to your athletes what you want to see​

Fundamental knowledge, purpose of skill, and characteristics of the most effective technique

Improve Technique, Observation

Observe the performance of your athlete to determine his/her technique

Improve Technique, Evaluation

Compare the ideal technique to the observed performance​

Identify and evaluate errors

Improve Technique, Instruction

Educate the athlete by providing feedback and the instruction necessary to correct those errors

Qualitative Anatomical Analysis Method, Fact #1

Muscle activity cannot be directly observed

Qualitative Anatomical Analysis Method, Fact #2

EMG is not easily accessible

Qualitative Anatomical Analysis Method, Fact #3

With knowledge and observation, you can get a general idea of which muscles are active based on the principles used in an inverse dynamic analysis

Inverse Dynamic Analysis

1. Divide the activity into temporal phases​

2. Identify the joints and movements involved​

3. Determine the type of muscular contraction (concentric, eccentric, or isometric) and identify the predominant active muscle group at each joint​

4. Identify instances when rapid joint angular accelerations occur and where impacts occur​

5. Identify any extremes in joint ranges of motion

Tissue Responses to Stress

A tissue adapts to the level of stress imposed on it (Julius Wolff, 1892)​

As mechanical stress increases, a tissue gains strength through hypertrophy​

This is know as "Wolff's Law"

Pathologic Underload Zone

Distress​

Injury = Atrophy

Low stress continuum

Physiologic Loading Zone

Eustress

Low stress continuum

Physiologic Training Zone

Eustress

High stress continuum

Pathologic Overload Zone

Distress

Injury

High continuum

Overuse Injury

Longitudinal

Fm = Am Om

Pennate

Fm = (Am cos) Om

Torsion

A twisting force

During a push-up, the humerus undergoes what type of stress?

Compressive

The fiber arrangement in ligaments allows more resistance to non-axial loads

True

A section of the patellar tendon is 34 mm2 in cross-section. What would the stress in this section of the tendon be as a result of an 8,500 N tensile force?

250 MPa

The modulus of elasticity (for compression) for a section of compact bone in the femur is 13 GPa (13 × 109 Pa, or 13,000,000,000 Pa). If this bone is subjected to a compression stress of 45 MPa (45 × 106 Pa, or 45,000,000 Pa), what strain results from this compression?

0.00346

The yield strength of a material is 20 MPa (20,000,000 Pa). The yield strain for this material is 0.4%. What is the modulus of elasticity?

5 GPa

The modulus of elasticity for a prosthetic material is 20 GPa (20,000,000,000 Pa). A 3 cm long sample of this material has an area of 0.003 m2. This sample is stretched to 3.004 cm. What tensile force was applied to the material to create this stretch?

80,000 N

A 2.2 cm long section of the patellar tendon stretches to 2.205 cm when it is subjected to a tensile force of 14,500 N. What is the strain in this segment of the tendon? (give the answer as a percentage)

0.227%

Put the following parts in order, from largest to smallest:

1. Fascicle

2. Myofibril

3. Whole muscle

4. Myofilament

5. Myocyte (muscle cell)

3, 1, 5, 2, 4

The form of a bone will be determined by the mechanical stresses imposed on it and its function

True

The basic contractile unit of muscles is the ______________

Sarcomere

Which of the following joint types cannot move about more than one axis (i.e., does not have more than one degree of freedom)? Mark all that apply

Pivot joints

Hinge joints

Which of the following connective tissue sheaths covers the muscle fasciculi?

Perimysium

Which of the following would be an example of a fusiform muscle?

Biceps Brachii

The ______________ is the membrane of a muscle fiber

Sarcolemma

Which of the following types of joints would not allow for flexion or extension movements?

Pivot

A unipennate muscle has a cross-sectional area of 10 cm2 and another cross-sectional area of 11 cm2. The angle of pennation for both cross-sectional areas is 30°. This muscle can produce a maximal isometric contraction force of 500 N. What is the stress during the maximal isometric contraction?

27.49 N/cm2

A longitudinal muscle has a cross-sectional area of 11.5 cm2 and can produce 30 N/cm2 of stress during an isometric contraction. What is the maximal isometric force that this muscle is capable of producing?

345 N

The control of force through the manipulation of motor unit firing rates is referred to as _________

Rate coding

The otolith organs (utricle and saccule) are responsible for detecting rotational movements of the head. True or False?

False

One way a muscle can control force is by how many of the muscle fibers each motor neuron activates. True or Flase?

True

Which of the following reflexes involves the stimulation of Golgi tendon organs (GTOs)?

Inverse myotatic reflex

A high innervation ratio is better suited for _______________

Muscles responsible for gross movements

Which of the following best represents the motor unit recruitment order that would occur due to the size principle?

Small motor units get recruited first, then larger ones

Which type of neuron is efferent?

Motor

Stimulation of which of the following receptors contributes to the stretch-shortening cycle?

Muscle spindles

The long, slender projection on a neuron that carries actions potentials is referred to as ___________________

Axon

Which type of neuron is afferent?

Sensory

Which of the following is not considered a component of physical fitness? Cardiovascular fitness

Flexibility

Psychological capacity

Muscular power

Muscular strength

Psychological capacity

___________ training may involve performing the actual skill or performing drills that mimic specific aspects of the skill

Technical

The first step of a qualitative anatomical analysis is to ______________________________

Break down the performance into specific phases or motions

After determining the primary plane of the movement for the skill, the best place to observe the performance of that skill is ____________________________

Perpendicular to that plane

The Physiologic Training Zone on the stress continuum represents a level of stress _____________ that to which the tissue has adapted

Above

Wolff's Law essentially states that, as mechanical stress _________________, a tissue gains strength through ________________

Increases; Hypertrophy

Which of the following is not one of the steps for using qualitative biomechanical analyses to improve technique?

Simulation

Overuse injuries are often a consequence of ________________

Inadequate recovery time