THE MUSCULAR SYSTEM

Did you know that ?

• more than 50% of body weight is muscle !
• And muscle is made up of proteins and water

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The Muscular System

• Muscles are responsible for all movement of the body
• There are three basic types of muscle
• Skeletal
• Cardiac
• Smooth

Info About Muscles

• Only body tissue able to contract
• create movement by flexing and extending joints
• Body energy converters (many muscle cells contain many mitochondria)

3 Types of Muscles

Three types of muscle

Classification of Muscle

Characteristics of Muscle

• Skeletal and smooth muscle are elongated
• Muscle cell = muscle fiber
• Contraction of a muscle is due to movement of microfilaments (protein fibers)
• All muscles share some terminology
• Prefixes myo and mys refer to muscle
• Prefix sarco refers to flesh

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Skeletal Muscle

• Most are attached by tendons to bones
• Cells have more than one nucleus (multinucleated)
• Striated- have stripes, banding
• Voluntary- subject to conscious control
• Tendons are mostly made of collagen fibers
• Found in the limbs
• Produce movement, maintain posture, generate heat, stabilize joints

Structure of skeletal muscle

• Each cell (fibre) is long and cylindrical
• Muscle fibres are multi-nucleated
• Typically 50-60mm in diameter, and up to 10cm long
• The contractile elements of�skeletal muscle cells are�myofibrils

Skeletal muscle - Summary

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• Voluntary movement of skeletal parts
• Spans joints and attached to skeleton
• Multi-nucleated, striated, cylindrical fibres

Smooth Muscle

• No striations
• Spindle shaped
• Single nucleus
• Involuntary- no conscious control
• Found mainly in the walls of hollow organs

Smooth muscle

• Lines walls of viscera

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• Found in longitudinal or circular arrangement

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• Alternate contraction of circular & longitudinal muscle in the intestine leads to peristalsis

Smooth muscle - Summary

• Found in walls of hollow internal organs
• Involuntary movement of internal organs
• Elongated, spindle shaped fibre with single nucleus

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Cardiac Muscle

• Striations
• Branching cells
• Involuntary
• Found only in the heart
• Usually has a single nucleus, but can have more than one

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Cardiac muscle

• Main muscle of heart
• Pumping mass of heart
• Critical in humans
• Heart muscle cells behave as one unit
• Heart always contracts to it’s full extent

Structure of cardiac muscle

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• Cardiac muscle cells (fibres) are short, branched and interconnected
• Cells are striated & usually have 1 nucleus
• Adjacent cardiac cells are joined via electrical synapses (gap junctions)
• These gap junctions appear as dark lines and are called intercalated discs

Cardiac muscle - Summary

• Found in the heart
• Involuntary rhythmic contraction
• Branched, striated fibre with single nucleus and intercalated discs

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Muscle Control

Skeletal

Skeletal

Cardiac

Smooth

Where Does the Energy Come From?

• Energy is stored in the muscles in the form of ATP
• ATP comes from the breakdown of glucose during Cellular Respiration
• This all happens in the Mitochondria of the cell
• When a muscle is fatigued (tired) it is unable to contract because of lack of Oxygen

Muscle Attachments

Flexion

Types of Musculo-Skeletal Movement

Extension

Hyperextension

Abduction, Adduction & Circumduction

Rotation

The Skeletal Muscles��There are about 650 muscles in the human body. They enable us to move, maintain posture and generate heat. In this section we will only study a sample of the major muscles.

MASSETER

Elevate Mandible

TRAPEZIUS

Extend Head, Adduct, Elevate or Depress Scapula

LATISSIMUS DORSI

Extend, Adduct & Rotate Arm Medially

DELTOID

Abduct, Flex & Extend Arm

PECTORALIS MAJOR

Flexes, adducts & rotates arm medially

BICEPS BRACHII

Flexes Elbow Joint

TRICEPS BRACHII

Extend Elbow Joint

RECTUS ABDOMINUS

Flexes Abdomen

EXTERNAL OBLIQUE

Compress Abdomen

BICEPS FEMORIS

Extends Thigh & Flexes Lower Leg

GASTROCNEMIUS

Plantar Flexes Foot & Flex Lower Leg