The Muscular System

Structure and Function of Muscle Tissue

Muscle type

Skeletal Cardiac Smooth

Striated?

Voluntary?

Location?

Regenerate

Function?

Structure and Function of Muscle Tissue

Muscle type

Skeletal Cardiac Smooth

Striated?

Voluntary?

Location? Throughout

Body

Heart Digestive tract, etc.

Regenerate Limited No Yes

Function? Movement Movement Movement

Functions of muscle tissue important for Homeostasis

MovementStabilizes bodyRegulates organ

volumeProduces heatMovement of food,

urine, blood

Layers of deep dense CT that surrounds muscle SG pg 108

Epimysium – entire muscle

Perimysium – bundle of muscle fibers

Endomysium – individual fibers

Muscle MicroanatomyA band – darkest color – most dense

thick and thin filaments overlapH band - medium color – medium density

thick filaments onlyI band – lightest color – least dense

thin filaments only

Z disc – separate one sarcomere from another

M line – dark middle of sarcomereMyofibrils – 1 – 2 micrometers in diameterSarcomere – contractile unitSarcolemma – plasma membrane of muscle

fiberSarcoplasm – cytoplasm of muscle fiber

Sarcoplasmic reticulum – fluid-filled sacs around each myofibril

During the contraction phase – thin filaments move towards M line

Ach (acetylcholine) released at neuromuscular junction

Muscle Ultrastructure Muscle fiber Myofibrils Filaments

Basics of Muscle Contraction SG pg 110

Animation of Muscle Contraction

Isometric exercises – exercise with an immovable resistant object

Contraction with NO movement

Isotonic exercises (aerobic exercise) – exercise with movement

Contraction with movement

Skeletal muscles cooperate!Muscles can only pull or contract – so most

body movements are the result of muscles acting together or against each other.

Prime moversAntagonistsSynergists Fixators

Origin – end of muscle attached to immovable bone

Insertion – end of muscle attached to movable bone

Naming MusclesAction

Direction of Fibers

Location

Number of Origins

Points of attachment of origin and insertion

Size or Shape

ANATOMY STUDY WEBSITE

ANATOMY ARCADE GAMES

Muscles that move the Head and Neck

Muscles that move the Trunk

Posterior

Pelvis, Hip, and Thigh

Lower Leg

Atrophy – shrinking of muscle tissue from lack of use

Hypertrophy – enlargement of existing muscle cells

Hyperplasia – increase in the number of muscle fibers

Muscles and Aging

Beginning at around 30 years, slow, progressive loss of skeletal muscle tissue

Replaced by fibrous CT and adipose tissue

Decrease in muscle strength

Slower muscle reflexes

Loss of flexibility

Common Muscle disordersMyasthenia gravis –

Autoimmune disorder that causes chronic, progressive damage of the neuromuscular junction

Muscles of face and neck

1 in 10,000 peopleMostly women

Muscular DystrophyA group of inherited

muscle-destroying disorders that target specific muscle groups

Cause is the lack of a protein muscle fibers

No cureEx. Duchenne’s MD

FibromyalgiaPainful,

nonarticular rheumatic condition

more common in women

Affects fibrous CT of muscles, tendons, and ligaments

Abnormal contractionsSpasm

Sudden involuntary contraction of a single muscle in a large group of muscles

CrampPainful spasmodic

contractionInadequate blood flow,

overuse, dehydration, injury

Holding a position for a long time

Low potassium level

Tremor Rhythmic, involuntary,

purposeless contraction Quivering or shaking

motionFasciculation

Twitching often seen in MS

Fibrillation Spontaneous

contraction only seen by electromyography

Tic – spasmodic twitching of a muscle normally under voluntary control

Muscle cramps Not enough

CalciumLack of oxygen

Muscle strainTearing of a

muscleBleeding within

muscle and severe pain

Treat with RICERestIceCompressionElevation

Causes of muscle fatigueMuscle fatigue –

when a muscle is unable to contract even when it is still being stimulated

Oxygen depletion/debt from prolonged muscle activity

Lactic acid buildupATP depletion

Oxygen DebtO2 debt, which

occurs after vigorous muscle activity, must always be “paid back”

This “pay back” begins when a person breathes rapidly and deeply after activity – this continues until the muscles have enough O2 to get rid of the lactic acid buildup