The Muscular System

Overview

• The muscular system enables tasks such as blinking, smiling, running, jumping, and standing upright.
• Comprises over 650 muscles in the body.
• Responsible for the heart beating and maintaining body temperature.

Muscle Types

1. Skeletal Muscle

   • Attaches to bones via tendons.
   • Responsible for most body movements.
   • Under voluntary control through the somatic nervous system.
   • Contains slow-twitch and fast-twitch fibers.
   • Makes up 30-40% of body weight.
   • Examples: Pectorals, biceps, buccinator, stapedius.

2. Cardiac Muscle

   • Found only in the heart.
   • Pumps blood continuously.
   • Controlled by the autonomic nervous system.

3. Smooth Muscle

   • Lines blood vessels and certain organs (e.g., intestines, uterus).
   • Controlled by the autonomic nervous system.
   • Involved in processes like blood flow, digestion, and childbirth.

Muscle Contractions

• Shortening and Lengthening Fibers: Generates opposing forces for movement (e.g., biceps and triceps).
• Stabilizing Force: Keeps muscles rigid, maintaining posture and allowing grip.

Muscle Fiber Types

• Fast-twitch Fibers
  • React quickly, tire out fast.
  • Suitable for activities requiring quick bursts of energy (e.g., sprinting).
• Slow-twitch Fibers
  • Endurance cells, react slowly, sustain energy longer.
  • Suitable for prolonged activities (e.g., maintaining posture).

Energy and Heat Production

• Muscles consume energy to function.
• Generate 85% of body heat.
• Heart and blood vessels distribute this heat to maintain body temperature.

Summary

• The muscular system is essential for almost every action and process in the body, from subtle movements to maintaining vital functions like circulation and temperature regulation.