The Muscular System

or “Everything you ever wanted to know about

Muscles, but were afraid to ask” !!!

How many muscles do we have???

Did you know that ?

- more than 50% of body weight is muscle !

- And muscle is made up of proteins and water

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)

Muscles have

• Fascia- which is tough sheet like membrane

3 Types of Muscles

Three types of muscle

Skeletal Cardiac Smooth

Classification of Muscle

Skeletal-

found in limbs

Cardiac-

found in heart

Smooth-

Found in viscera

Striated, multi- nucleated

Striated, 1 nucleus

Not striated, 1 nucleus

voluntary involuntary involuntary

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

Shapes of Muscles

• Triangular- shoulder, neck

• Spindle- arms, legs

• Flat- diaphragm, forehead

• Circular- mouth, anus

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 ofskeletal muscle cells aremyofibrils

Skeletal muscle - Summary

• 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

• Found in longitudinal or circular arrangement

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

Structure of smooth muscle

• Spindle shaped uni-nucleated cells

• Striations not observed

• Actin and myosin filaments are present( protein fibers)

Smooth muscle - Summary

• Found in walls of hollow internal organs

• Involuntary movement of internal organs

• Elongated, spindle shaped fibre with single nucleus

Cardiac Muscle

• Striations

• Branching cells

• Involuntary

• Found only in the heart

• Usually has a single nucleus, but can have more than one

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• 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

Muscle Control

Type of muscle

Nervouscontrol

Type of control

Example

SkeletalSkeletal Controlled by CNS

Voluntary Lifting a glass

Cardiac Regulated by ANS

Involuntary Heart beating

Smooth Controlled by ANS

Involuntary Peristalsis

Types of Responses

• Twitch-– A single brief contraction– Not a normal muscle function

• Tetanus– One contraction immediately followed by

another– Muscle never completely returns to a relaxed

state– Effects are compounded

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

Exercise and Muscles

• Isotonic- muscles shorten and movement occurs ( most normal exercise)

• Isometric- tension in muscles increases, no movement occurs (pushing one hand against the other)

How are Muscles Attached to Bone?

• Origin-attachment to a immovable (fix) bone

• Insertion- attachment to an movable bone

• Muscles are always attached to at least 2 points

• Movement is attained due to a muscle moving an attached bone

Muscle Attachments

Origin

Insertion

Flexion

Types of Musculo-Skeletal Movement

Extension

Hyperextension

Abduction, Adduction & Circumduction

Rotation

More Types of Movement……

• Inversion- turn sole of foot medially

• Eversion- turn sole of foot laterally

• Pronation- palm facing down

• Supination- palm facing up

• Opposition- thumb touches tips of fingers on the same hand

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.

SternocleidomastoideusFlexes and Rotates Head

TrapeziusExtend Head, Adduct, Elevate or

Depress Scapula

Latissimus DorsiExtend, Adduct & Rotate Arm Medially

DeltoidAbduct, Flex & Extend Arm

Pectoralis MajorFlexes, adducts & rotates arm medially

Biceps BrachiiFlexes Elbow Joint

Triceps BrachiiExtend Elbow Joint

Rectus AbdominusFlexes Abdomen

DiaphragmInspiration

Gluteus MaximusExtends & Rotates

Thigh Laterally

Quadriceps femoris

• Muscle on the front of the thigh that extends the leg

Muscle properties and characteristics:

• Excitability: irritability, the ability to respond to stimulus such as nerve impulse

• Contractibility: muscle fibers that are stimulated by nerves contract, or become short and thick, which causes movement

• Extensibility: the ability to be stretched

• Elasticity: allows the muscle to return to its original shape after it has contracted or stretched

• Muscles attach by origin, insertion and by – Fascia: a tough, sheet-like membrane that covers and

protects the tissue

– The deep muscles of the trunk and back, which are surrounded by the lumbodorsal fascia

• Muscles are partially contracted at all times, even when not in use

– Muscle tone- state of partial contraction

– Atrophy- loss of muscle tone when muscles are not used for a long period

– Contracture- a severe tightening of a flexor muscle resulting in bending of a joint

• Foot drop is a common contracture, but the fingers, wrists, knees, and other joints can also be affected

Diseases and Abnormal Conditions

• Fibromyalgia: chronic, widespread pain in specific muscle sites– Symptoms: muscle stiffness, numbness or tingling in

the arms or legs, fatigue, sleep disturbances, headaches, and depression

– Cause is unknown, but stress, weather, and poor physical fitness affect the condition

– Treatment: directed toward pain relief and includes physical therapy, massage, exercise, stress reduction, and medication to relax muscles and relieve pain

Muscular Dystrophy• A group of inherited diseases that lead to chronic,

progressive muscle diseases that lead to muscle atrophy– Usually appears in early childhood

– Most types result in total disability and early death

– Most common type: Duchenne muscular distrophy, which is caused by a genetic defect

• At birth the infant is healthy, as muscle cells die, the child loses the ability to move

• Onset usually occurs between 2 and 5 years of age

• By age 9-12, the child is confined to a wheelchair

• Eventually, the muscle weakness affects the heart and diaphragm, resulting in respiratory and/or cardiac failure that causes death.

• Life expectancy: late teens to the early twenties

• No cure, but physical therapy is used to slow progress

Myasthenia Gravis• Chronic condition where nerve impulses are

not properly transmitted to the muscles

• Leads to progressive muscular weakness and paralysis

• Affects respiratory muscles, can be fatal

• Cause is unknown, though is thought to be autoimmune (antibodies attacking the body’s own tissue)

• No cure; Treatment is supportive

Muscle Atrophy

• Inherited chronic progressive disorder in which results in muscle shrinking

» Results in complete disability

» Early death

Strain• An overstretching of or injury to a muscle and/or

tendon• Frequent site include the back, arms, and legs• Cause: Prolonged or sudden muscle exertion • Symptoms: myalgia (muscle pain), swelling, and

limited movement• Treatment: rest, muscle relaxants or pain

medications, elevating the extremity, and alternating hot and cold applications

Muscle Spasms

• Muscle spasms, or cramps, are sudden, painful, involuntary muscle contractions

• Usually occur in the legs to feet and may result from overexertion, low electrolyte levels, or poor circulation

• Gentle pressure and stretching of the muscle are used to relieve the spasm

• Draw where each of these muscles are on a poster paper.• For each describe the type of movement they perform…

For example: Pectoralis- are in the upper chest and adducts and flexes the arms.

Must be neat and have color • Gastrocnemius Biceps brachii• Triceps brachii Deltoid• Sternocleidomastoid Rectus Abdominus • Gluteus maximus Intercostals• Latissimus dorsi• Quadriceps femoris• Tibialis anterior• Trapezius• Pectoralis