Topic 11 – Human health & physiology11.2 – Muscles and Movement

JOINTS

• Rheumatology – branch of medicine devoted to joint diseases and conditions.

• Joints provide mobility and hold the body together.

• Joints include: bones, ligaments, muscles, tendons, and nerves.

JOINTShttp://www.youtube.com/watch?v=SOMFX_83sqk

Bones

• Bones are composed of many different tissues, considered organs.

• Function- Framework for support- Protect soft tissues- Levers for movement- Bone marrow blood

cells- Storage of minerals

For movement to occur, it is essential that skeletal muscles are attached to bones.

Muscles

• Provide force for movement to occur.

• Antagonistic pairs – constriction then release for return to original position.

Tendons

• Attach muscles to bone.• Cords of dense

connective tissue.

Ligaments have many different types of sensory nerve endings to monitor positions of joint parts

Ligaments

• Tough, band-like structures that serve to strengthen the joint.

Nerves

• Help to prevent over-extension of the joint and its parts.

Label a diagram of the human elbow

Include: cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps).

http://sambal.co.uk/?page_id=238

The parts of the elbow

• The elbow joint involves the humerus, radius and ulna bones. The synovial fluid is present within the synovial cavity. This cavity is located within the joint capsule. The joint capsule is composed of dense connective tissue that is continuous with the membrane of the involved bones.

The elbow is a hinge joint

• Provides an opening-and-closing type of movement (imagine hinges on a door).

• The knee is a similar joint.

• Freely movable joints.• Freely movable –

diarthrotic joints.

JOINT PART FUNCTION

CARTILAGE Reduces friction and absorbs compression

SYNOVIAL FLUID Lubricates to reduce friction and provides nutrients to the cells of the cartilage

JOINT CAPSULE Surrounds the joint, encloses the synovial cavity, and unites the connecting bones

TENDONS Attach muscle to bone

LIGAMENTS Connect bone to bone

BICEPS MUSCLE Contracts to bring about flexion (bending) of the arm

TRICEPS MUSCLE Contracts to cause extension (straightening) of the arm

HUMERUS Acts as a lever that allows anchorage of the muscles of the elbow

RADIUS Acts as a lever for the biceps muscle

ULNA Acts as a lever for the triceps muscle

The knee

Notice that the Tibia and Femur do not actually make contact.

• Although the knee is a hinge joint it also allows for some pivotal movement.

The hip

• Ball-and-socket joint (allow the greatest degree of movement)

• Head of femur (thigh bone) fits into cup-like depression of the hip bone called the acetabulum.

Comparison: Knee to Hip

Hip Joint

• Freely movable• Motion in many directions

and rotational movements• Motions possible are

flexion, extension, abduction, adduction, circumduction and rotation

• Ball-like structure fits into a cup-like depression

Knee Joint

• Freely movable• Angular motion in one

direction• Motions possible are

flexion and extension• Convex surface fits into a

concave surface

definitions

• Flexion = decrease in angle between connecting bones• Extension = increase in angle between connecting bones• Abduction = movement of bone away from body midline• Adduction = movement of bone toward midline• Circumduction = distal or far end of a limb moves in a

circle• Rotation = a bone revolves around its own longitudinal

axis

http://www.midsouthorthopedics.com/education.html

muscle

• 3 types: skeletal (striated), cardiac, and smooth (non-striated)

• Striated muscle – skeletal muscle (involved in skeletal movement)

Striated muscle cells

• Muscles made up of cells• Cellular arrangement

produces banded appearance

• Muscle cell elongated shape = muscle fibers

• Contain multiple nuclei• Membrane of muscle

cells called sarcolemma• Cytoplasm of muscle

fibers called sarcoplasm

More muscle cell structure

• Sarcoplasmic reticulum is a fluid-filled system of membranous sacs surrounding muscle myofibrils (much like smooth ER)

• Myofibrils – rod-shaped bodies that run the length of the cell

• Many myofibrils running parallel to each other

• Numerous mitochondria squeezed in between

• Contractile elements of muscle cells

• Reason for striation

Myofibril structure

• Made up of sarcomeres (units that allow movement)

• Z lines mark ends of sarcomere

• A bands (both myosin and actin) = dark

• H bands (only myosin) = light in middle of A bands

Sarcomere structure

• Support protein in middle of myosin produces the M line (holds myosin filaments together)

• I bands (contain only actin) = light color

• Two types of filaments (myofilaments) cause banded appearance of muscle fiber

• Composed of two contractile proteins

Two contractile proteins

Actin

• Thin filaments (8nm in diameter)

• Contains myosin-binding sites

• Individual molecules form helical structures

• Includes two regulatory proteins, tropomyosin and troponin

Myosin• Thick filaments (16 nm in

diameter)• Contains myosin heads that

have actin-binding sites• Individual molecules form a

common shaft-like region with outward protruding heads

• Heads are referred to as cross-bridges and contain ATP-binding sites and ATPase enzymes

Muscle contraction and the sliding filament theory

• Muscle contract when actin myofilaments slide over myosin myofilaments.

• The myofilaments do not actually shorten.• When the actin component slides over the myosin, the

sarcomere is shortened.• With multiple fibers and sarcomeres in a muscle working

together, this causes the movements necessary for the organism.

Key events of muscle contraction

1) Action potential reaches neuromuscular junction

2) Neurotransmitter (acetylcholine) into gap between axon terminal and sarcolemma

3) Acetylcholine binds to receptors on the sarcolemma

4) Sarcolemma ion channels open and sodium ions move through the membrane

5) This generates a muscle action potential

Muscle contraction cont…6) Muscle AP moves along membrane

and through T tubules

7) Acetylcholinesterase ensures one directional AP propagation

8) Muscle AP releases calcium ions from sarcoplasmic reticulum (Ca ions flood sarcoplasm)

9) Ca ions bind to troponin on actin myofilaments exposing myosin-binding sites

10) Myosin heads include ATPase (releases energy from ATP)

11) Myosin heads bind to myosin-binding sites on the actin with help of protein tropomyosin

More muscle contraction

12) The myosin-actin cross-bridges rotate toward the center of the sarcomere. This produces the power or working stroke

13) ATP binds to myosin head resulting in detachment of myosin from actin

14) No more AP = fall of Ca ions in sarcoplasm; troponin-tropomyosin complex returns to original position blocking myosin-binding sites; muscle relaxes

Little extra - Botox

• Bacteria Clostridium botulinum

• Blocks release of acetylcholine and prevents muscle contraction

• Can affect diaphragm so breathing stops and death may occur

• Active ingredient in Botox• Typically used to relax the

muscles that cause facial wrinkles

Any questions?

Little more extra

• When a person dies calcium ions leak and bind to troponin

• ATP production has stopped and the actin slides causing rigor mortis (rigidity of death)

• Lasts for ~24 hours until further muscle deterioration occurs