Muscular System Overview

Study Notes

The muscular system is a complex system that consists of over 600 muscles that make up about 40% of an adult's body weight.
The main function of the muscular system is to facilitate movement, maintain posture, and regulate body temperature.

Skeletal Muscles (Voluntary Muscles):
- Attached to bones and help move the body's skeleton
- Under conscious control
- Examples: biceps, quadriceps, hamstrings
Smooth Muscles (Involuntary Muscles):
- Found in the walls of hollow organs and blood vessels
- Not under conscious control
- Examples: muscles in the digestive tract, blood vessels, and airways
Cardiac Muscles:
- Found in the heart and responsible for pumping blood
- Not under conscious control
- Has a unique structure and function that allows it to contract rhythmically

Movement: Muscles work together with bones to facilitate movement
Support: Muscles help maintain posture and support the body's weight
Stability: Muscles help stabilize joints and maintain balance
Regulation of Body Temperature: Muscles help generate heat through shivering
Protection: Muscles help protect internal organs by surrounding them

Muscle Fibers: The building blocks of muscles, made up of myofibrils, myofilaments, and sarcoplasm
Myofibrils: Contain contractile units called sarcomeres
Sarcomeres: The functional units of muscle contraction, made up of actin and myosin filaments
Neuromuscular Junction: The site where a motor neuron innervates a muscle fiber, allowing for muscle contraction

Sliding Filament Theory: The mechanism by which muscles contract, where actin and myosin filaments slide past each other to shorten the muscle
Muscle Contraction Types:
- Isotonic Contraction: Muscle contracts and shortens, moving the load
- Isometric Contraction: Muscle contracts, but does not shorten, generating force without moving the load

The muscular system makes up around 40% of an adult's body weight, consisting of over 600 muscles.
The main functions of the muscular system include facilitating movement, maintaining posture, and regulating body temperature.

Skeletal Muscles (Voluntary Muscles):
- Attached to bones to facilitate movement of the body's skeleton
- Under conscious control, with examples including biceps, quadriceps, and hamstrings
Smooth Muscles (Involuntary Muscles):
- Found in the walls of hollow organs and blood vessels, not under conscious control
- Examples include muscles in the digestive tract, blood vessels, and airways
Cardiac Muscles:
- Found in the heart, responsible for pumping blood, and not under conscious control
- Has a unique structure and function, allowing it to contract rhythmically

Muscle Fibers: Building blocks of muscles, composed of myofibrils, myofilaments, and sarcoplasm
Myofibrils: Contain contractile units called sarcomeres
Sarcomeres: Functional units of muscle contraction, composed of actin and myosin filaments
Neuromuscular Junction: Site where a motor neuron innervates a muscle fiber, allowing for muscle contraction

Sliding Filament Theory: Mechanism of muscle contraction, where actin and myosin filaments slide past each other to shorten the muscle
Muscle Contraction Types:
- Isotonic Contraction: Muscle contracts and shortens, moving the load
- Isometric Contraction: Muscle contracts, but does not shorten, generating force without moving the load