Lecture Notes: Muscle and Motility

Overview

• Discussion on muscle and motility using Arnold Schwarzenegger as a reference.
• Systems in living organisms work together, such as immune and digestive systems.
• Focus on the musculoskeletal system which comprises muscles, bones, and joints.

Musculoskeletal System Functions

• Bones: Provide structure, protection to organs, site for blood cell synthesis, storage of minerals, act as levers.
• Cartilage: Reduces friction between bones, provides stability.
• Ligaments: Connect bones to each other, maintain joint stability.
• Muscles and Tendons: Muscles contract to enable movement; tendons connect muscles to bones.
• Neurons: Send signals from the brain to muscles to initiate contraction.

Joint Structure and Function

• Cartilage: Ensures smooth movement by reducing friction.
• Synovial Fluid: Lubricates joints to allow smooth movement.
• Types of Joints:
  • Ball and Socket: Allows movement in multiple directions (e.g., shoulder, hip).
  • Hinge Joint: Allows movement in one plane (e.g., elbow, knee).

Muscle Types

• Skeletal Muscles: Voluntary control, multi-nucleated, striated.
• Cardiac and Smooth Muscles: Involuntary control.
• Skeletal Muscle Structure: Composed of muscle fibers, containing myofibrils (contractile units).

Muscle Contraction

• Begins with nerve impulses triggering the release of neurotransmitters (acetylcholine).
• Calcium is released, exposing binding sites on actin for myosin.
• Sliding Filament Theory: Describes how myosin heads pull actin filaments to contract the muscle.
• Requires ATP for detachment and reattachment of myosin heads.

Muscle Pairs and Movement

• Antagonistic Muscle Pairs: Opposing functions
  • Example: Biceps (flexion) and triceps (extension).
  • Inhalation and exhalation involve intercostal muscles.

Concepts in Musculoskeletal System

• Endoskeleton vs Exoskeleton:
  • Endoskeleton: Inside the body (vertebrates).
  • Exoskeleton: Outside the body, made of chitin (arthropods).
• Range of Motion: Measured by goniometer, important for recovery tracking.
• Titan Fibers: Provide structural support, aid in muscle recoil after contraction.

Adaptations and Examples

• Sessile Organisms: Limited movement, example - Venus flytrap.
• Motile Organisms: Capable of movement within habitat, example - Sloths.
• Swimming Adaptations: Dolphins have streamlined bodies, fluke tails, blowholes for efficient swimming.

Summary

• Understanding the musculoskeletal system's structure and function is essential for comprehending movement and motility.
• Muscles, bones, and joints interact in complex ways to facilitate locomotion and other bodily functions.
• Differences in muscle and skeletal systems across different organisms point to evolutionary adaptations.