11.2 MUSCLES & MOVEMENT

IB BIOLOGY

MOVEMENT: THE HUMAN MACHINE

• Joints

• Bones

• Nerves

• Muscles

• Tendons

• Ligaments

THE ELBOW

THE ELBOW• Biceps – bends the arm (flexor)

• Triceps – straightens the arm (extensor)

• Humerus – anchors muscle (muscle origin)

• Radius/Ulna – acts as forearm levers (muscle insertion)

• Radius acts as a lever for the biceps• Ulna acts as a lever for the triceps

• Cartilage – allows easy movement (smooth surface), absorbs shock and distributes load

• Synovial fluid – provides food, oxygen, and lubrication to the cartilage

• Joint capsule – seals the joint space and provides passive stability by limiting range of movement

KNEE JOINT VS HIP JOINT

KNEE JOINT VS HIP JOINT

Similarities:

- Both are synovial joints

- Both are involved in the movement of the leg

Differences:

MUSCLE STRUCTURE

sarcomeres < myofibrils < muscle fibers = MUSCLES

muscle fibers – long multinucleate cells

Within each muscle fiber are cylindrical structures called myofibrils

Myofibrils consist of repeating units called sarcomeres, which have light and dark bands

STRIATED MUSCLE FIBER

STRIATED MUSCLE FIBER

Sarcolemma – specialized plasma membrane

Sarcoplasmic reticulum – specialized endoplasmic reticulum designed for muscle contraction (contains high Ca2+)

Myofibrils – tubular fibers divided into sections called sarcomeres, and made up of two different myofilaments (actin & myosin)

Mitochondria – large numbers in order to produce enough ATP for muscle contraction

STRIATED MUSCLE FIBER

SARCOMERES

SARCOMERES

SARCOMERES

H zone – area only occupied by the thick filaments (myosin)

I bands (light) – regions occupied by only thin filaments (actin)

A bands (dark) - are the region occupied by both filaments (overlap)

Z lines – represent the extremeties of a single sarcomere

SARCOMERES

H zone – area only occupied by the thick filaments (myosin)

I bands (light) – regions occupied by only thin filaments (actin)

A bands (dark) - are the region occupied by both filaments (overlap)

Z lines – represent the extremeties of a single sarcomere

SARCOMERES

H-zoneA bandI band

SARCOMERES

H-zone

A bandI band I band

SARCOMERE CONTRACTION

SARCOMERE CONTRACTION

SARCOMERE CONTRACTION

What do you expect to happen to the: H zone?A band?I band?

SARCOMERE CONTRACTION

SARCOMERE CONTRACTION

SARCOMERE CONTRACTION

Four Stages of Cross Bridge Cycle

1) Cross Bridge Formation

2) Power Stroke

3) Cross Bridge Detachment

4) Reactivation of Myosin Head