Unit 4 option C: Human health & fitness C.1 Body systems; musculo-skeletal system By Mr. Wilson

Human skeleton

Synovial joints Characterised by a ‘space’ between the articulating bones. Characterised by a ‘space’ between the articulating bones. Freely moveable. Freely moveable. The whole joint is contained in a fibrous capsule containing connective tissue & collagen fibres. The whole joint is contained in a fibrous capsule containing connective tissue & collagen fibres.

Synovial joints Synovial membrane – Loose connective tissue with elastin and varying quantities of adipose. Secretes SYNOVIAL FLUID. Synovial membrane – Loose connective tissue with elastin and varying quantities of adipose. Secretes SYNOVIAL FLUID. Synovial fluid – Hyaluronic acid (lubrication) and, blood plasma derived, interstitial fluid. More viscous in joints with less movement. Serves to lubricate the joint and nourish the articular cartilage. Synovial fluid – Hyaluronic acid (lubrication) and, blood plasma derived, interstitial fluid. More viscous in joints with less movement. Serves to lubricate the joint and nourish the articular cartilage.

Synovial joints Articular cartilage – Hyaline cartilage covered with synovial fluid to reduce friction. As joint load increases it can absorb water increasing the concentration of hyaluronic to reduce friction. Articular cartilage – Hyaline cartilage covered with synovial fluid to reduce friction. As joint load increases it can absorb water increasing the concentration of hyaluronic to reduce friction.

Synovial joints Other ligaments: Other ligaments: Extracapsular ligament – May be present to offer additional structural support to a joint. Such as in the knee. Extracapsular ligament – May be present to offer additional structural support to a joint. Such as in the knee. Intracapsular ligament – such as cruciate ligaments of the knee. They are located within the articular capsule. Intracapsular ligament – such as cruciate ligaments of the knee. They are located within the articular capsule.

Synovial joints Synovial joints are the most common in the human body. Synovial joints are the most common in the human body. Identify & locate some! Identify & locate some!Link: /JOINTS.html /JOINTS.html /JOINTS.html /JOINTS.html

Muscle 3 types in the body: 3 types in the body: Cardiac – Myogenic & found in the heart only. Cardiac – Myogenic & found in the heart only. Smooth/involuntary – Walls of gut, uterus, urethra, blood vessels & bladder. Not under conscious control. Smooth/involuntary – Walls of gut, uterus, urethra, blood vessels & bladder. Not under conscious control. Skeletal/voluntary/striated – Attached to the skeleton by tendons. Under conscious control. Striped appearance. Skeletal/voluntary/striated – Attached to the skeleton by tendons. Under conscious control. Striped appearance.

Muscle structure Muscle is made from numerous contractile units called SARCOMERES. Sarcomeres form thin striped threads called MYOFIBRILS. Many myofibrils form a MUSCLE FIBRE and Muscle fibres make up the tissue we call MUSCLE. Muscle is made from numerous contractile units called SARCOMERES. Sarcomeres form thin striped threads called MYOFIBRILS. Many myofibrils form a MUSCLE FIBRE and Muscle fibres make up the tissue we call MUSCLE. Myofibrils are made of overlapping strands of protein filaments called ACTIN & MYOSIN. Myofibrils are made of overlapping strands of protein filaments called ACTIN & MYOSIN.

Muscle structure

The area between the Z bands or lines is one sarcomere. The area between the Z bands or lines is one sarcomere. ACTIN filaments are thin and MYOSIN filaments are thick. ACTIN filaments are thin and MYOSIN filaments are thick. They overlap in a region called the A band. Only ACTIN is present in the I bands which overlap separate sarcomeres. They overlap in a region called the A band. Only ACTIN is present in the I bands which overlap separate sarcomeres.

Muscle Structure There is also an H band in the centre which contains only MYOSIN. There is also an H band in the centre which contains only MYOSIN. Around each myofibril are tubes containing Ca 2+ Ions. Around each myofibril are tubes containing Ca 2+ Ions. The ACTIN filaments also contain the proteins TROPONIN and TROPOMYSIN. These proteins are involved in the process of muscle contraction. The ACTIN filaments also contain the proteins TROPONIN and TROPOMYSIN. These proteins are involved in the process of muscle contraction.

Muscle Structure

Muscle structure

Muscle Contraction When a muscle contracts the ACTIN filaments slide over the MYOSIN filaments shortening the sarcomere. When a muscle contracts the ACTIN filaments slide over the MYOSIN filaments shortening the sarcomere. I bands become shorter. I bands become shorter. A bands stay the same size. A bands stay the same size. Z membranes/lines move closer together Z membranes/lines move closer together H zone becomes narrower. H zone becomes narrower.

Sliding Filament Theory Nerve impulse reaches N-M junction. Nerve impulse reaches N-M junction. Acetylcholine depolarises membrane of muscle fibre = Action potential! Acetylcholine depolarises membrane of muscle fibre = Action potential! Ca Ions are released into the muscle fibres and bind with TROPONIN altering it’s shape. Ca Ions are released into the muscle fibres and bind with TROPONIN altering it’s shape. TROPONIN displaces TROPOMYOSIN (which was blocking the ACTIN-MYOSIN binding site). MYOSIN ‘heads’ now bind to ACTIN = ACTOMYOSIN BRIDGE. TROPONIN displaces TROPOMYOSIN (which was blocking the ACTIN-MYOSIN binding site). MYOSIN ‘heads’ now bind to ACTIN = ACTOMYOSIN BRIDGE.

Muscle Contraction During this binding, enabled by energy from ATP, the MYOSIN heads tilt causing the ACTIN filaments to slide past detaching the MYOSIN heads, which attach to the next binding site thus sliding the ACTIN filaments along. During this binding, enabled by energy from ATP, the MYOSIN heads tilt causing the ACTIN filaments to slide past detaching the MYOSIN heads, which attach to the next binding site thus sliding the ACTIN filaments along. Ca Ions are absorbed back into the tubes between filaments, TROPONIN changes back to it’s original shape and TROPOMYOSIN again blocks the A-M binding site. Ca Ions are absorbed back into the tubes between filaments, TROPONIN changes back to it’s original shape and TROPOMYOSIN again blocks the A-M binding site.

Muscle Contraction/Ratchet Mechanism