Biomechanics of Muscle Contraction and Movement

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Questions and Answers

What branch of physics studies the behavior of physical bodies under forces and displacements?

Optics

Mechanics (correct)

Thermodynamics

Kinematics

In which plane do flexion and extension occur for the thumb?

Oblique plane

Frontal plane (correct)

Sagittal plane

Transverse plane

What are the two primary types of motion for the body and its segments?

Translatory and rotary (correct)

Static and dynamic

Cyclic and random

Linear and angular

What is meant by degrees of freedom in relation to joint movement?

The number of planes within which a joint moves Signup and view all the answers

Which movement occurs in the sagittal plane rather than the frontal plane?

Flexion Signup and view all the answers

What type of axis does forearm rotation utilize when it is no longer considered longitudinal?

Anterior-posterior axis Signup and view all the answers

How many degrees of freedom are typically found in joints of the human body?

Three degrees of freedom Signup and view all the answers

The term 'planes of motion' is used to describe what aspect of movement?

The orientation of an object during movement Signup and view all the answers

What happens to a muscle's force development as the speed of concentric contraction slows?

Force development increases. Signup and view all the answers

What characterizes a maximum isometric contraction?

There is no motion involved. Signup and view all the answers

What leads to a decreased ability of a muscle to produce contraction force as shortening speed increases?

Decreased number of crossbridges formed. Signup and view all the answers

How does the moment arm of a muscle impact joint rotation?

It provides leverage around the joint. Signup and view all the answers

What occurs during eccentric contraction in relation to muscle strength?

Muscle strength increases as speed increases. Signup and view all the answers

At what speed do the maximum number of crossbridges form?

At slow speeds of contraction. Signup and view all the answers

What happens to the number of links formed between actin and myosin filaments as the contraction speed increases?

It decreases. Signup and view all the answers

What is the relationship between speed of contraction and the ability to develop force in concentric vs eccentric contractions?

Eccentric contractions develop more force as speed increases, while concentric contractions decrease. Signup and view all the answers

What type of joint is characterized by a spherical head fitting into a cup-like depression?

Ball-and-socket joint Signup and view all the answers

Which of the following types of joints allows for no movement?

Synarthrodial Signup and view all the answers

Which movement involves the circular or conical motion of a body part?

Circumduction Signup and view all the answers

What is the main difference between circumduction and rotation in joint movement?

Circumduction combines multiple movements, while rotation is solely around an axis. Signup and view all the answers

Which joint type includes examples like sutures and gomphoses?

Synarthrodial Signup and view all the answers

What role does the glenoid cavity of the scapula play in the shoulder joint?

It forms the socket of the joint. Signup and view all the answers

What is the main anatomical feature of ball-and-socket joints?

A spherical head fitting into a cup-like depression Signup and view all the answers

Which movement refers to turning or spinning around a central axis?

Rotation Signup and view all the answers

What occurs when a motor unit’s nerve activates its muscle fibers?

All activated muscle fibers contract maximally. Signup and view all the answers

Which principle describes the order of motor unit activation during muscle contraction?

Size Principle Signup and view all the answers

What increases overall muscle tension during contraction?

Recruitment of additional motor units. Signup and view all the answers

What do Golgi Tendon Organs detect?

Force/Tension Signup and view all the answers

How does muscle fiber tension increase according to the excitatory input/rate coding principle?

By increasing the frequency of stimulation of motor units. Signup and view all the answers

Which part of the spinal cord contains motor neurons?

Ventral/anterior horns Signup and view all the answers

What characteristic of joint receptors allows the body to maintain a sense of position in space?

They emit action potentials continuously at rest. Signup and view all the answers

What is the relationship between the number of muscle fibers and control required over a muscle?

Greater control is achieved with fewer muscle fibers per nerve fiber. Signup and view all the answers

Which principle is described by increasing the number of activated motor units leading to greater muscle tension?

Recruitment Principle Signup and view all the answers

Which of the following is true about muscle impulses?

They are action potentials transmitted over muscle fibers. Signup and view all the answers

What is the primary role of proprioception in movement?

To provide sensory input for joint position and movement discrimination Signup and view all the answers

Which statement best describes the nature of motor control?

It is a complex regulation of posture and movement Signup and view all the answers

What characterizes muscle synergy?

It is defined by a coordinated, functional activation of muscles Signup and view all the answers

What distinguishes Type I muscle fibers from Type II muscle fibers?

Type I fibers are generally more resistant to fatigue and suited for endurance Signup and view all the answers

Which condition is NOT necessary for predicting muscle function based on anatomic attachments?

The muscle is fully relaxed Signup and view all the answers

What does heterarchy in motor control systems imply?

Interdependent and parallel functioning of different muscle systems Signup and view all the answers

In the context of muscle activity, what is 'negative work'?

Muscle movements performed against gravity where control is required Signup and view all the answers

Which of the following best defines mobility muscles?

Muscles specifically responsible for dynamic movements Signup and view all the answers

Study Notes

Speed of Contraction

Concentric contractions produce more force when slower, reaching peak force at isometric or zero-velocity contractions.
Maximum crossbridge formation occurs at slow speeds; increased contraction speed reduces actin-myosin links and force.
During eccentric contractions, muscle strength increases with speed, contrary to concentric contractions.

Moment Arm

The moment arm relates to the perpendicular distance from the joint axis to the muscle's force vector, influencing joint rotation.
Mechanics study the behavior of physical bodies under forces and their displacements.

Planes of Motion

Movement occurs along three primary planes: sagittal, frontal, and transverse, defining how the body moves relative to its orientation.
Examples of joint naming utilize the proximal bone first, e.g., RU, AA, SI joints.

Axes of Motion

Imaginary lines around which body parts rotate, distinguished by being perpendicular to the movement planes.

Naming Movements at Joints

Joints named by the accompanying bones.
Movements include medial and lateral rotation at the hip, with rotation occurring around an anterior-posterior axis instead of a longitudinal axis.

Types of Motion

Body segments exhibit either translatory (linear) or rotary (angular) motion.

Degrees of Freedom

Degrees of freedom in joints reflect the number of plane movements allowable, maximized at three.

Joint Structure and Function

Joints are classified into three types:
- Synarthrodial (immovable, e.g., sutures)
- Amphiarthrodial (slightly movable, e.g., pubic symphysis)
- Diarthrodial (freely movable, e.g., ball-and-socket joints like the shoulder).

Circumduction vs. Rotation

Circumduction involves circular or conical movement of a body part through a combination of flexion, extension, abduction, and adduction.
Rotation involves turning around a central point or axis without changing the position of the joint itself.

Synarthrodial Joints

Synarthrodial joints are composed of fibrous connective tissue, allowing minimal to no movement between bones.

Muscle Fibers and Action Potential

Nerve impulses translate into action potentials transmitted over nerve and muscle fibers.
Motor units contract maximally when activated.

Gradiation of Strength of Muscle Contraction

The smallest motor units activate first (Size Principle), while increasing the number of motor units (Recruitment Principles) raises overall muscle tension.
Excitatory input increases muscle tension by raising stimulation frequency.

Joint, Tendon, and Muscle Receptors

Joint receptors continuously emit action potentials, giving the brain a sense of body position.
Golgi Tendon Organs detect muscle force and tension.

Proprioception

Proprioception integrates input from muscle spindles, tendons, and joints to assess joint position and movement.

Motor Control

Motor control encompasses posture regulation and the intricate coordination of movements through muscle synergy.
Movement functions within a heterarchical system, allowing diverse movement combinations.

Types of Muscle Activity

Muscle activity is categorized into isotonic, isometric, and isokinetic movements, each defined by how muscle length and joint movement occur.
Understanding muscle fiber types:
- Type I fibers are postural, supporting stability against gravity.
- Type II fibers are non-postural or mobility muscles, activated for rapid or forceful movements.

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Description

This quiz explores the principles of muscle contraction, focusing on the differences between concentric and eccentric contractions. It also delves into the mechanics of movement through various planes and axes, offering insights into the impact of force and moment arms on joint rotation.