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 PARTFUNCTION CARTILAGEReduces friction and absorbs compression SYNOVIAL FLUIDLubricates to reduce friction and provides nutrients to the cells of the cartilage JOINT CAPSULESurrounds the joint, encloses the synovial cavity, and unites the connecting bones TENDONSAttach muscle to bone LIGAMENTSConnect bone to bone BICEPS MUSCLEContracts to bring about flexion (bending) of the arm TRICEPS MUSCLEContracts to cause extension (straightening) of the arm HUMERUSActs as a lever that allows anchorage of the muscles of the elbow RADIUSActs as a lever for the biceps muscle ULNAActs 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