AB TEST 1

Purpose of muscles

Produce movement, maintain posture, stabilize joints, generate heat, and control movement.

Newton's 1st Law

An object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force; also called the law of inertia.

Newton's 2nd Law

Force equals mass times acceleration (F = ma).

Newton's 3rd Law

For every action, there is an equal and opposite reaction.

Action potential

An electrical signal that travels along a neuron and allows the nervous system to communicate.

Depolarization

Sodium (Na+) enters the neuron, making the membrane more positive.

Repolarization

Potassium (K+) leaves the neuron, making the membrane more negative.

Hyperpolarization

The membrane temporarily becomes more negative than its resting potential.

Structural classification of joints

Fibrous, cartilaginous, and synovial.

Fibrous joint

A joint connected by dense connective tissue; example: skull sutures.

Cartilaginous joint

A joint connected by cartilage; example: pubic symphysis.

Synovial joint

A freely movable joint with a joint cavity and synovial fluid; example: knee.

Kinesiology

The study of human movement.

Biomechanics

The study of forces and their effects on living organisms.

Mechanics

The study of forces and motion.

Kinematics

The study and description of motion without considering the forces causing it.

Anatomical position

Standing upright, facing forward, arms at the sides, palms facing forward, and feet facing forward.

Functional position

The position a body part assumes while performing a specific activity.

Stability

The ability to resist unwanted movement or maintain position.

Balance

The ability to maintain body position and equilibrium.

Center of gravity

The point where the body's mass is considered to be concentrated.

Equilibrium

A state in which forces acting on an object are balanced.

Proprioception

The body's ability to sense position, movement, and joint orientation without looking.

Bilateral

Relating to both sides of the body.

Unilateral

Relating to one side of the body.

Medial

Toward the body's midline.

Lateral

Away from the body's midline.

Anterior

Toward the front of the body.

Posterior

Toward the back of the body.

Superior

Toward the head or upper part of the body.

Inferior

Toward the feet or lower part of the body.

Proximal

Closer to the trunk or point of attachment.

Distal

Farther from the trunk or point of attachment.

Superficial

Closer to the surface of the body.

Deep

Farther from the surface of the body.

Lever

A rigid structure that rotates around an axis or fulcrum.

Three parts of a lever

Axis/fulcrum, force/effort, and resistance/load.

Axis

The point around which a lever rotates.

Force arm

The distance from the axis to where the force is applied.

Resistance arm

The distance from the axis to where the resistance is applied.

Torque

The turning effect of a force; torque equals force multiplied by the moment arm.

First-class lever

The axis is between the force and resistance; example: neck extension.

Second-class lever

The resistance is between the axis and force; example: standing on the toes.

Third-class lever

The force is between the axis and resistance; example: biceps curl.

Most common lever in the human body

Third-class lever.

Purpose of levers

To produce movement, increase speed, increase range of motion, increase force, or change the direction of force.

Mechanical advantage

The ability of a machine or lever to multiply force.

Mechanical advantage formula

Mechanical advantage = force arm ÷ resistance arm.

Force arm increases

Torque and mechanical advantage increase, assuming resistance arm stays the same.

Resistance arm increases

Mechanical advantage decreases, assuming force arm stays the same.

Force and velocity relationship

As concentric contraction velocity increases, the amount of force a muscle can produce generally decreases.

Eccentric force

Muscles can generally produce more force while lengthening than while shortening.

Parallel muscle fibers

Muscle fibers run parallel to the long axis; they generally favor greater shortening, speed, and range of motion.

Pennate muscle fibers

Muscle fibers attach to a tendon at an angle; they generally allow more fibers to fit into a muscle and favor greater force production.

Purpose of parallel muscles

Generally provide greater shortening, speed, and range of motion.

Purpose of pennate muscles

Generally provide greater force production.

Concentric contraction

The muscle shortens while producing force.

Eccentric contraction

The muscle lengthens while producing force.

Isometric contraction

The muscle produces force without changing length.

Isotonic contraction

The muscle changes length while producing force; includes concentric and eccentric contractions.

Isokinetic contraction

The muscle contracts while movement occurs at a constant velocity, usually using specialized equipment.

Joint mobility

The amount of movement available at a joint.

Joint stability

The ability of a joint to resist unwanted movement.

Mobility vs stability

Generally, increased mobility comes with decreased stability, while increased stability comes with decreased mobility.

Sagittal plane

Divides the body into left and right portions; primarily contains flexion and extension.

Frontal plane

Divides the body into front and back portions; primarily contains abduction and adduction.

Transverse plane

Divides the body into upper and lower portions; primarily contains rotation.

Hinge joint

Primarily allows flexion and extension; example: elbow.

Pivot joint

Primarily allows rotation; example: atlantoaxial joint in the neck.

Ball-and-socket joint

Allows movement in multiple planes and rotation; examples: shoulder and hip.

Saddle joint

Allows movement in multiple directions; example: thumb.

Condyloid joint

Allows flexion, extension, abduction, and adduction; example: wrist.

Plane/gliding joint

Allows bones to glide across one another; examples: some wrist and ankle joints.

Open-packed position

Joint position where surfaces are less congruent, the capsule is more relaxed, and there is more joint play.

Closed-packed position

Joint position where surfaces are maximally congruent and ligaments and capsule are tight, producing maximum stability.

Open-packed vs closed-packed

Open-packed favors mobility and joint play; closed-packed favors stability.

Angle of pull

The angle between a muscle's line of pull and the bone it acts on.

Rotary component

The component of muscle force that produces rotation or movement.

Parallel component

The component of muscle force that can compress or distract a joint.

90-degree angle of pull

Produces the greatest rotary component of muscle force.

Length-tension relationship

The amount of force a muscle produces depends on its length and actin-myosin overlap.

Force-time relationship

The longer a muscle has to develop force, the more force it can generally produce up to its limits.

Force-frequency relationship

Increasing stimulation frequency can increase muscle force through summation until maximal contraction occurs.

Velocity

Speed in a specific direction.

Velocity formula

Velocity = displacement ÷ time.

Friction

A force that opposes motion between surfaces.

Static friction

Friction that prevents an object from beginning to move.

Kinetic friction

Friction that acts when surfaces are already moving against each other.

Bone functions

Support, protection, movement, mineral storage, and blood cell production.

Muscle attachment to bone

Muscles attach to bones through tendons.

Dendrite

The part of a neuron that primarily receives signals.

Axon

The part of a neuron that carries electrical signals away from the cell body.

Axon terminal

The end of an axon that communicates with another neuron or muscle cell.

Motor unit

One motor neuron and all the muscle fibers it controls.

All-or-none principle

When a motor neuron fires, all muscle fibers within that motor unit contract.

Na+ and action potential

Sodium enters the neuron during depolarization.

K+ and action potential

Potassium leaves the neuron during repolarization.

Shoulder joint

Highly mobile but generally less stable than the hip.

Hip joint

Generally more stable than the shoulder but less mobile.