Biomechanics

If the biceps brachii, attaching to the radius 2.5 cm from the elbow joint at an angle of 60°, is exerting a tension of 200N in the muscle, and the triceps brachii, attaching to the radius 3cm away from the elbow joint also at an angle of 60°, exerts a force of 150N of tension in the muscle, how much net torque is present at the joint, in the unit of Nm? (PICTURE)

.43 Nm

Muscular system quiz 2: If the biceps muscle force F = 25N, the muscle attaches to the radius bone at 4cm from the elbow joint, and the attachment angle θ = 30∘, compute the torque exerted by the muscle (in Nm). (picture)

.5 Nm

Muscles with lots of sarcomeres in series can achieve high (PICTURE)

Range of Motion

Which descending pathway originates from the brainstem?

Reticulospinal tract

Reflexive movement is mainly mediated by

Spinal cord

Describe how stress-strain function is computed and the major components of its curve.

Stress is computed by the force divided by the area, as where strain is computed by dividing the change in length divided by length. The major components consist of elastic modulus (k), yield point, the elastic region, plastic region, and the failure point. The elastic modulus is the slope of the linear section of the curve. It indicates the stiffness in the material, and is computed by stress divided by the strain. The yield point is the structure when it is elastic region and past the yield point is the plastic region. The elastic region is where the material can return back to its original length once stress is removed. The plastic region is where the molecular components of the material is permanently displaced and where stress is decreased. The failure point is if the applied force continues past the plastic region, the tissues will eventually fall,

In the force-length curve, the total isometric force produced by the muscle at a given length is equal to

Sum of active and passive tension

Shin splints occur when the tibialis anterior pulls on its attachment site on the tibia and on the interosseous mebrane between the tibia and the fibula. What kind of loading is this?

Tensile

Which of the following is an example of angular motion

The arm of a golfer during a golf-swing

Describe what are the factors that make the hip a stable joint.

The hip is also a a ball and socket joint, allowing for stability with the depth. It consists of strong ligaments and a thick capsule.

Describe what are the factors that make the shoulder a flexible joint.

The shoulder is a ball and socket joint where it has multiple degrees of freedom, specifically allowing the shoulder to move with adduction, abduction, flexion, extension, internal rotation, external rotation. There are many muscles that surrounded the shoulder.

Which of the following is NOT true for flexor reflexes

They are mediated by the monosynaptic spinal pathway... So these are true :They evoke crossed extensor reflex in the contralateral limb, They excite flexors and inhibit extensors in the stimulated limb, They involve the quick withdrawn response upon noxious stimulus

Which of the following are the properties of fast twich fibers

They are smaller in diameter than slow twitch fibers, They fatigue quickly, They exhibit a shorter electrochemical delay than slow twitch fibers

Which of the following are the properties of slow twitch fibers

They are smaller in diameter, They contract slowly to maximum force, They exhibit a shorter electrochemical delay.

Which of the following is NOT a property of short-latency stretch reflexes

They can integrate a wide range of arbitrary cortical level input.

Which of the following is NOT a property of short-latency stretch reflexes

They can integrate a wide range of arbitrary to cortical level input

If a person holds a 100 N weight in their hand 0.4 m from the elbow, what is the elbow flexor muscle force? Assuming the forearm weight is 11N, forearm center of mass is 0.16m from the elbow joint, biceps brachii muscle attachment site is 0.03m from the elbow joint, and attachment angle is 60. (PICTURE)

1,607.34N

EMG activation is higher when the same force is generated using concentric contraction compared to eccentric contraction.

True

Hemiplesia can be a result from both primary motor cortex and corticospinal tract.

True

When stimulated by an action potential at rest, the same muscle always produces the same amount of tension regardless of other factors such as joint position and angle.

True

Compute the torque (in Nm) exerted by the muscle in the following figure, assume muscle force F= 110N, the muscle attaches at the bone with an angle of 30°, 2.5cm from the joint.

1.37 Nm - work

A muscle was estimated to have a force producing capacity of 80N per square centimeter (k=80Ncm2). To produce a desired tendon force of 110N, what must be the effective minimum PCSA of the muscle (in cm2)? (PICTURE)

1.59 cm^2

A muscle's force-producing capacity k was estimated as 17N/cm2, and its attached at the bone with 30° angle. What must be the effective minimum physical cross-section area (PSCA) in cm2 of the muscle to produce a tendon force of 150N?

10.17 - work

The forearm has ____ degrees of freedom, which is made possible by how many joints ____

2, 2

The hip joint is one of the most stable joints in the human body. How many degrees of freedom does the hip joint have?

3

If the biceps brachii, attaching to the radius 2.5 cm from the elbow joint at an angle of 60°, is exerting a tension of 200N in the muscle, and the triceps brachii, attaching to the radius 3cm away from the elbow joint also at an angle of 60°, exerts a force of 150N of tension in the muscle, how much extension torque is present at the joint, in the unit of Nm? (PICTURE)

3.89 Nm

If the biceps brachii, attaching to the radius 2.5 cm from the elbow joint at an angle of 60°, is exerting a tension of 200N in the muscle, and the triceps brachii, attaching to the radius 3cm away from the elbow joint also at an angle of 60°, exerts a force of 150N of tension in the muscle, how much flexion torque is present at the joint, in the unit of Nm? (PICTURE)

4.33Nm

Compute the torque the shoulder must exert (in Nm) when forearm is flexed (shown in posture B). (PICTURE)

5.26Nm

Compute the torque the shoulder must exert (in Nm) when forearm is extended (shown in posture A). (PICTURE)

7.5Nm

If the fibers of a pennate muscle are oriented at a 45° angle to a central tendon, how much tension is produced in the tendon when the muscle fiber contract with 110N of force? (PICTURE)

77.8

Muscular quiz 1: If the fibers of a pennate muscle are oriented at a 30° angle to a central tendon, how much tension is produced in the tendon when the muscle fiber contract with 110N of force? (PICTURE)

95.3

Select the best match of the word representing the letter from the picture.

A. Dendritic branch, B. Soma, C. Node of Ranvier, D. Axon terminal

Neural control 2: Match the letters corresponding the appropriate brain area and the words listed. (PICTURE)

A. Prefrontal Cortex (PFC), B. Premotor Cortex (PMd/PMv) , C. Supplementary Motor Area (SMA), D. Primary Motor Cortex (M1), E. Central Sulcus, F. Somatorsensory Cortex (S1), G. Posterior Parietal Cortex (PPC)

This figure shows the stress-strain curves obtained from cortical bone specimens. What mechanical property of the bone this figure highlights?

Anisotropy

Which exercise exerts more tension at the knee? (PICTURE)

Back squat

Parkinson's disease

Basal ganglia

What type of loading force is typically responsible for ski boot fracture?

Bending

Which component of bone contributes most to its elasticity?

Calcium phosphate: Inorganic component is the major contributor to the elastic property of the bone. Organic materials mainly contribute to the viscoelastic property.

ataxia

Cerebellum

Your friend Sarah was trying to strengthen her quadriceps in an strengthening exercise. She would like to produce the maximum amount of load with the same weight block. Should she place the weight block close to her knee or her ankle?

Close to the ankle

Which of the following lifestyle choices may reduce the risk of osteoarthritis?

Combine strength training exercises with weight-bearing and balance exercises

Which of the following statements best describes the stretch-shortening cycle?

Concentric muscle action is preceded by an eccentric muscle action.

The knee joint has two degrees of freedom and is a ___ joint.

Condyloid

When the alpha motoneurons activate the muscle, for the muscle to continue its contraction, gamma motoneurons are simultaneously to ______, which maintains stretch of the muscle spindles at the same rate as the whole muscle. This ensures that the muscle spindles continue to send information to the brain about muscle position and ________, and recruit more motoneurons.

Contract the intrafusal fibers, length

If a stroke occurs in the left side of the brain, the right side of the body will be affected, producing hemiparesis/hemiplegia on the right side of the body. The affected side of the body is the ______ side.

Contralesional

Which descending pathway contains monosynaptic projections?

Corticospinal tract, Cotocomotorneuronal pathway, Pyramidal tracts

Osteoarthritis is a leading cause of disability in people 65 and older. It is caused by

Degeneration in articular cartilage

A motor unit consists of a group of muscles that are innervated by the same motor neuron.

False

Because stretch reflexes are mediated by the monosynaptic spinal pathway and are primitive and stereotypical, they resist modifications by other systems.

False

Which reflex causes you to jerk your limb back from a painful stimulus?

Flexor

Muscles with lots of sarcomeres in parallel can achieve high (PICTURE)

Force

Put the following types of synovial joints in order from the least mobile to the most mobile

Gliding, Pivot, Saddle, Ball and Socket

______ describes a condition featuring muscle weakness and impaired control of contralateral limbs resulting from damage to the ______; ______ describes a condition involving the loss of skilled movements that is not due to muscle weakness and is caused by damage to ______.

Hemiparesis, motor cortex; Apraxia, premotor-parietal cortex

Which joint is typically the most stable?

Hip

Following the size principle, in what order are motor units recruited?

I, IIa, IIb

Above images are from different stages of clean and jerk weightlifting. If you were to analyze a short time-window (~0.1 s) around when the photo was taken, which stages would qualify for static analyses? (Select all that apply.)

In both stages C and D, the weightlifter is holding the weights and the bar steady.

Describe three types of muscle contractions during a free-weight exercise.

Isometric contraction is when the muscle contracts, but there is no change in the length of the muscle. The force of contraction equals the external force. Concentric contraction is when the muscle contracts towards the center, shortening in its length, causing joint rotation. Force of contraction is greater then the external force. Eccentric force is when the muscle contracts away from the center, increasing its length. Force of contraction is less than the external force.

Describe the Hill Muscle Model and use it to explain force-length relationship.

It consists of the contractile component (active) where the element that converts stimulation to force. the muscle is also shortening through actin and myosin. The passive components has parallel elastic (connective tissues) and series (tendon muscle). Reflects elasticity inherent in the muscle, the force length relation of a single fiber is determined by the overlap of actin and myosin. For the whole muscle it must account for active and passive components. The arrangement of fibers influences the ROM or force production.

Which one of the following statements about the corticospinal tract is false?

It facilitates flexors and suppresses extensors ipsilaterally.. so these are true: It passes through brainstem, It supports dexterous control, It contains both direct and indirect pathways

The examination of projectile characteristics of a high jumper is an example of which type of analysis?

Kinematic

The examination of projectile characteristics of a high jumper is an example of which type of analysis? (picture)

Kinematic

Which of the following is NOT a factor that contributes to EMG signals?

Length of connective tissue in the muscles... so these do: Motor unit firing rate, Active motor units, Distance from skin surface to muscle fiber

Describe the major symptoms of hemiparesis after stroke and explain the major neural mechanism contributing to these symptoms.

Major symptoms include, weakness, difficulty walking, and loss of balance. A cause can be an imbalance between flexors and extensors due to loss of CST. Also damage to the M1, where there is weakness or loss of coordination and control of one halfs body.

What is Wolff's law? Using an example, describe the biological and mechanical property changes that obey the Wolff's Law.

Wolff's law is when you don't use it, you lose it. A biological example would be, a dominant arm of a baseball player has more cortical bone then the other arm. A mechanical example is a new runner versus a regular runner. For the new runner would not be as use to the load as an regular runner (bone degeneration).

The _____ motor neurons activate the ______ fibers to produce the force required for the action, and the _____ motor neurons activate the ______ fibers to set the desired level of feedback from the muscle spindles.

alpha, skeletal muscle, gamma, intrafusal

In the following picture, three lifting strategies were used. Which one exerts the largest amount of tension at the hip and the lumbar spine? (PICTURE)

c

Name five sections of the spine in a top-down order.

cervical, thoracic, lumbar, ,sacral ,coccygeal

Which one is an example of a kinetic study?

Measuring push-off force of sprinters when they take off from the starting blocks, and Calculating the drag force experienced by the runners when they take off from the starting blocks (Measuring acceleration is a kinematic analysis.)

Compute the elastic modulus of the specimen.

PICTURE: 3,125

The above figure shows the stress-strain curve for a biological material. The stress-strain curves are different for different loading rates. What is this property of a material called?

PICTURE: Viscoelasticity

In the three-component Hill Model of muscle, which component most closely corresponds to the tissues surrounding the sacromere?

Parallel elastic component

Apraxia

Parietal cortex

The curves above represents the relationship between tensile stress (σ) and tensile strain (ε) for four different biological materials. The "dot" on each curve indicates the yield point/elastic limit and the "x" represents the rupture point. Fill in the blank spaces below with the correct number referring to a material (numbers are listed above corresponding material). You CAN use the same number more than once.

Picture: The most ductile material is 1, The most brittle material is 4, The strongest material is 1, The toughest material is 1, The Stiffest material is 1

The region between Y and R is called (PICTURE)

Plastic

hemiparesis

Primary motor cortex

In the stress-strain curves of different kinds of body tissues (shown below), ligament is more _____ compared to cortical bone.

compliant

When in ascending stairs your quadriceps contract and the leg straightens. This type of contraction is called

concentric contraction- Quadriceps are hip flexors and knee extensors. They undergo concentric contraction (shortening) when the leg is straightened.

The passive tension produced when a muscle is stretched beyond its resting length is mainly due to

connective tissues such as endomysium, epimysium and perimysium

The "new M1" originates ____ pathway.

corticomotoneuronal

Neurons in M1 exhibit ______ at the single neuron level; whereas ______ is determined by _____ at the population level.

direction tuning, a net direction, population vector

At 75% of muscle activation, which of the following produce the highest level of force? (PICTURE)

eccentric contraction using the dumbell

Muscle spindles are the primary sensory receptors for the musculoskeletal system that alert the CNS of joint position, muscle length, and muscle tension.

false

During an isotonic contraction, movement has _____ resistance, ______ speed.

fixed, variable

In the question above, given the computed net torque, what motion would the forearm undergo?

flexion

During two-legged hopping, the feet contact the ground at touchdown and then leave the ground at toe-off. During the touchdown phase, the quadricepts and triceps surae muscles ____ and velocities of these muscles are ____. (PICTURE)

lengthen, negative

When Sarah moved the weight block from knee flexion to extension, did she need to exert more or less force?

more force

Compared with a pennate muscle of the same volume, a fusiform muscle will have (PICTURE)

more sarcomeres in series

Analysis of EMG signals in the frequency domain can provide information on:

muscle fatigue during isometric contraction

When muscle spindles are taut

muscles will be more responsive to stretch

A flexor reflex results from

pain such as heat

The following figure shows five typical types of muscle architecture. Type C-E are called ______ fibers, and they typically have more sarcomeres arranged in _____.

penniform, parallel

Which plane is this movement performed in? (Free throw picture)

sagittal

Order the following muscle structure from the smallest to the largest

sarcomere, myofibril, muscle fiber, fascicle, muscle, muscle group

In isometric contraction, muscle can produce the greatest force when the length is

slightly longer than resting length

Describe the size principle of motor neuron recruitment.

smaller neurons are recruited faster because it has a smaller surface, than a higher post synaptic potential, but conducted slowly.

Short-latency stretch reflexes are mediated via _ pathways and mainly regulate _ muscles; long-latency stretch reflexes are mediated via __ pathways and mainly regulate _ muscles.

spinal, proximal; cortical, distal

If recording from the motor cortex, the population vector for a single movement would be calculated as

the summed activity of neurons that that have preferred directions in all possible directions.

In the stress-strain curve for tendon shown in the Achilles Tendon video, the uncrimping of fibers is the _____region of a typical stress-strain curve, and the 8% strain point is typically called _____.

toe, failure point

Apraxia typically results from lesions that damage secondary motor areas while sparing primary motor cortex.

true

Motor nerves exiting the spinal cord at the ___ roots carry the ____ copy of the motor command.

ventral, efferent

Three motor units are shown in the figure below. Identify the large fast-fatigable motor unit(s).

C

Homework 2: Section 'C' of the myogram indicates which physiological process? (PICTURE)

C is unfused tetanus; D is fused tetanus.

In the three-component model of muscle, which component most closely corresponds to the tendon?

Series elastic component

Explain the difference between short- and long-latency stretch reflex.

Short latency- 20-30 ms; mediated by spinal reflexes pathways, more result to modification; responsible for regulating proximal muscle contractions. Long-latency is 50 -100 ms ; mediated by cortical pathways; more easily modified by cortical input; regulating distal muscle contraction.

Which joint is typically the most flexible?

Shoulder

The point U represents

strength

EMG is NOT a good tool for measuring ______.

the amount of load lifted in pounds... so it is good when a muscle turns on and off, the number of active motor units, muscle fatigue