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Muscular System

The system composed of approximately 600 muscles, accounting for about 48% of body weight.

Muscle Calculation

Formula used to estimate muscle weight: Body Weight x 0.48.

Pectoralis Major

A large muscle located in the chest responsible for adduction of the arm.

Function of Pectoralis Major

Plays a critical role in upper body movement including flexion and internal rotation.

Quadriceps Femoris

Composed of four muscles located at the front of the thigh.

Function of Quadriceps Femoris

Primarily responsible for extending the leg at the knee.

Latissimus Dorsi

A large muscle located in the back, vital for upper body movement.

Function of Latissimus Dorsi

Extends and adducts the arm, essential for swimming and climbing.

Hamstrings

Muscles located at the back of the thigh responsible for knee flexion.

Function of Hamstrings

Aids in hip extension and muscle thickness increases during flexion.

Movement

The major visible function of muscles that enables bodily actions.

Role of Muscles in Posture Maintenance

Muscles maintain partial contraction to help sustain body position.

Heat Production by Muscles

Generated by metabolic processes during muscle activity.

Joint Stabilization

Muscles that cross joints enhance their strength and protection.

Skeletal Muscle

Voluntary muscles responsible for movements of bones.

Cardiac Muscle

Involuntary striated muscle found in the heart, responsible for pumping blood.

Smooth Muscle

Involuntary muscle found in hollow organs, regulating functions like digestion.

Regeneration Capacity of Cardiac Muscle

Limited due to specialized cells that can only partially regenerate.

Skeletal Muscle Regeneration

Shows capacity to repair via satellite cells upon injury.

Voluntary Control in Skeletal Muscle

Requires neural stimulation for muscle contraction.

Muscle Atrophy

Muscles shrink when not exercised due to disuse.

Muscles of the Tongue

Includes Thyloglossus and Palatoglossus, enabling speech and swallowing.

Facial Muscles

Muscles responsible for facial expressions critical for non-verbal communication.

Muscles of Eye Movement

Six muscles that coordinate to enable complex eye movements needed for tracking.

Diaphragm

A muscle that separates thoracic and abdominal cavities important for respiration.

Muscle Structure Overview

Muscles connect to bones via tendons and aponeurosis.

Fascia

Connective tissue enveloping muscles, providing support.

Tendons

Cord-like structures connecting muscles to bones, influencing movement efficiency.

Aponeurosis

Sheet-like connective structures that attach muscles to the bone.

Muscle Architecture Types

Includes parallel, fusiform, convergent, and pinnate muscles.

Fusiform Muscles

Muscle type featuring a belly tapering at both ends, like Biceps Brachii.

Muscle Strength Factors

Determined by muscle cross-sectional area and lever arm length.

Pinnate Muscles

Allow for more muscle fibers and greater strength.

Muscle Fibers

Basic unit of skeletal muscle, also known as myofiber.

Sarcoplasm

Cytoplasm of muscle fibers containing organelles essential for function.

Mitochondria in Muscle Fibers

Powerhouses of the cell providing ATP crucial for sustained muscle activity.

T Tubules

Transverse tubules that connect the outer surface of muscle fibers to the interior.

Calcium Ions and Muscle Contraction

Essential for interaction between actin and myosin during contraction.

Excitation-Contraction Coupling

Mechanism linking muscle stimulation to contraction through calcium release.

Relaxation Process of Muscles

Involves ATP for detaching myosin heads and restoring resting state.

ATP in Muscle Energy Sources

Primary energy source derived from metabolic processes.

Myoglobin Function

Stores oxygen in muscle fibers for aerobic respiration.

Muscle Fatigue Causes

Results from ATP depletion and lactic acid buildup.

Rigor Mortis Process

Stiffening of muscles post-mortem due to calcium influx and lack of ATP.

Fast Muscle Fibers

Rely primarily on anaerobic metabolism, enabling quick bursts of energy.

Slow Muscle Fibers

More focused on endurance and resistant to fatigue through aerobic metabolism.

Isometric Contraction

Muscle contracts without changing its length; an example is pushing against a wall.

Isotonic Contraction

Muscle changes length while contracting, can be concentric or eccentric.

Smooth Muscle Features

Involuntary, non-striated muscles controlling slow rhythmic contractions.

Single-unit Smooth Muscles

Act as a single functional unit due to interconnections.

Cardiac Muscle Characteristics

Striated, involuntary muscle type uniquely adapted for synchronous contractions.