Topic 11 – Human health & physiology 11.2 – Muscles and Movement

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. JOINTS

joints http://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 Bones

Muscles Tendons Provide force for movement to occur. Antagonistic pairs – constriction then release for return to original position. Attach muscles to bone. Cords of dense connective tissue. For movement to occur, it is essential that skeletal muscles are attached to bones.

Ligaments Nerves Tough, band-like structures that serve to strengthen the joint. Help to prevent over-extension of the joint and its parts. Ligaments have many different types of sensory nerve endings to monitor positions of joint parts

Label a diagram of the human elbow Include: cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps). Label a diagram of the human elbow http://sambal.co.uk/?page_id=238

The elbow joint involves the humerus, radius and ulna bones 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 parts of the elbow

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. The elbow is a hinge joint

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 knee

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. The hip

Comparison: Knee to Hip Hip Joint Knee 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 Freely movable Angular motion in one direction Motions possible are flexion and extension Convex surface fits into a concave surface Comparison: Knee to Hip

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 definitions

3 types: skeletal (striated), cardiac, and smooth (non-striated) Striated muscle – skeletal muscle (involved in skeletal movement) muscle

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 Striated muscle cells

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 More muscle cell structure

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 Myofibril 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 Sarcomere structure

Two contractile proteins Actin Myosin Thin filaments (8nm in diameter) Contains myosin-binding sites Individual molecules form helical structures Includes two regulatory proteins, tropomyosin and troponin 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 Two contractile proteins

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. Muscle contraction and the sliding filament theory

Key events of muscle contraction Action potential reaches neuromuscular junction Neurotransmitter (acetylcholine) into gap between axon terminal and sarcolemma Acetylcholine binds to receptors on the sarcolemma Sarcolemma ion channels open and sodium ions move through the membrane This generates a muscle action potential Key events of muscle contraction

Muscle contraction cont… Muscle AP moves along membrane and through T tubules Acetylcholinesterase ensures one directional AP propagation Muscle AP releases calcium ions from sarcoplasmic reticulum (Ca ions flood sarcoplasm) Ca ions bind to troponin on actin myofilaments exposing myosin-binding sites Myosin heads include ATPase (releases energy from ATP) Myosin heads bind to myosin-binding sites on the actin with help of protein tropomyosin

More muscle contraction The myosin-actin cross-bridges rotate toward the center of the sarcomere. This produces the power or working stroke ATP binds to myosin head resulting in detachment of myosin from actin No more AP = fall of Ca ions in sarcoplasm; troponin-tropomyosin complex returns to original position blocking myosin-binding sites; muscle relaxes More muscle contraction

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 Little extra - Botox

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 Any questions?