Muscoskeletal Systems & Locomotion

Muscular system

One of the two interacting systems that make movement possible in animals.

Skeletal system

One of the two interacting systems that make movement possible in animals.

Hydrostatic skeleton

A fluid-filled cavity surrounded by muscles that contract against the fluid to produce movement.

Example of hydrostatic skeleton

Earthworms.

Exoskeleton

A rigid external covering that protects and supports the body.

Examples of organisms with exoskeletons

Insects and crustaceans.

Endoskeleton

An internal support structure composed of bone and/or cartilage.

Example of endoskeleton

Vertebrates, like humans.

Types of muscle tissues in vertebrates

Skeletal, cardiac, and smooth muscle.

Skeletal muscle

Striated and voluntary muscle tissue.

Cardiac muscle

Striated but involuntary muscle tissue.

Smooth muscle

Not striated and involuntary muscle tissue.

Function of skeletal muscle

It moves the skeleton and is under voluntary control.

Function of cardiac muscle

It contracts to pump blood through the circulatory system.

Function of smooth muscle

It moves contents through internal organs such as the digestive tract.

Muscle fibers

Made of myofibrils.

Myofibrils

Composed of sarcomeres.

Sarcomeres

Made up of actin (thin filaments) and myosin (thick filaments).

Functional unit of muscle contraction

The sarcomere.

Sliding filament model

A model describing how muscles contract as actin filaments slide over myosin filaments.

Triggers sliding of filaments in muscle contraction

The presence of calcium ions and ATP.

Role of ATP in muscle contraction

It provides the energy for the myosin heads to pull on actin filaments.

What happens when ATP binds to myosin

Myosin releases actin, re-*****, and is ready to bind again.

Releases calcium ions in muscle cells

The sarcoplasmic reticulum.

Initiates the release of calcium from the sarcoplasmic reticulum

An action potential from a motor neuron.

Protein that blocks myosin-binding sites on actin at rest

Tropomyosin.

Protein that moves tropomyosin when calcium binds to it

Troponin.

Motor unit

A motor neuron and all the muscle fibers it innervates.

How does the nervous system increase the strength of muscle contraction?

By recruiting more motor units.

What are the two types of muscle fibers?

Slow-twitch and fast-twitch fibers.

Which muscle fibers are more resistant to fatigue?

Slow-twitch fibers.

Which muscle fibers contract quickly but fatigue easily?

Fast-twitch fibers.

Which muscle fiber type contains more mitochondria and myoglobin?

Slow-twitch fibers.

What is the vertebrate endoskeleton primarily composed of?

Bone and cartilage.

What is cartilage?

A flexible connective tissue found in joints, ears, and the nose.

What are the three types of cartilage?

Hyaline cartilage, fibrocartilage, and elastic cartilage.

What is hyaline cartilage?

The most common type, found at joints and respiratory passages.

What is fibrocartilage?

Tough cartilage found in intervertebral discs.

What is elastic cartilage?

Flexible cartilage found in the ear and epiglottis.

What is bone?

A living connective tissue that is rigid and supports the body.

What are the two types of bone tissue?

Compact bone and spongy bone.

What are osteoblasts?

Cells that form new bone tissue.

What are osteoclasts?

Cells that break down bone tissue.

What are osteocytes?

Mature bone cells that maintain bone structure.

What is the Haversian system (osteon)?

The structural unit of compact bone.

What is red bone marrow responsible for?

Producing red blood cells, white blood cells, and platelets.

What does yellow bone marrow store?

Fat.

What are the three types of joints?

Immovable, slightly movable, and freely movable (synovial) joints.

Give an example of an immovable joint.

Sutures in the skull.

Give an example of a slightly movable joint.

The joints between vertebrae.

What are examples of synovial joints?

Hinge joints (elbow), ball-and-socket joints (shoulder).

What are ligaments?

Connective tissue that connects bones to other bones.

What are tendons?

Connective tissue that connects muscles to bones.

What is arthritis?

Inflammation of joints causing pain and stiffness.

What is osteoporosis?

A condition where bones become porous and fragile.

How can osteoporosis be prevented?

Adequate calcium intake, exercise, and hormone regulation.

What role does the skeleton play besides movement?

Protection of organs, mineral storage, and blood cell formation.

How do skeletal muscles produce movement?

By contracting and pulling on bones via tendons.

What are antagonistic muscle pairs?

Pairs of muscles that work in opposition, like biceps and triceps.

What is muscle tone?

A state of partial contraction maintained by muscles at rest.