Chapter 39 Structural Support and Movement

Hydrostatic Skeleton Muscles work against an internal body fluid and redistribute it within a confined space Radial cells are relaxed; longitudinal ones contracted Radial cells are contracted; longitudinal ones relaxed

Exoskeletons An exoskeleton is a hard encasement deposited on the surface of an animal – chitin Exoskeletons are found in most mollusks and arthropods Arthropods have a jointed exoskeleton called a cuticle, which can be both strong and flexible An arthropod must shed and regrow its exoskeleton when it grows

Endoskeleton An endoskeleton consists of a hard internal skeleton, buried in soft tissue – provides a rigid structure to which muscles attach – function in support, protection, and movement A mammalian skeleton has more than 200 bones Some bones are fused; others are connected at joints by ligaments that allow freedom of movement

ossicletube foot Echinoderm s Echinoderms have endoskeletons located within their dermis

Endoskeleton All vertebrates Fins or limbs attach to skeleton at pectoral and pelvic girdles pelvic girdlepectoral girdle Generalized mammal

Vertebrate skeletons Vertebrate Skeletons

SKULL cranial bones facial bones sternum RIB CAGE ribs VERTEBRAL COLUMN vertebrae intervertebral disks PECTORAL GIRDLES AND UPPER EXTREMITIES clavicle scapula humerus radius ulna carpals metacarpals phalanges pelvic girdle femur patella tibia fibula tarsals metatarsals phalanges PELVIC GIRDLE AND LOWER EXTREMITIES

Functions of Bone interact with muscle to enable movement support and anchor muscles enclose and protect internal organs store minerals – calcium – phosphorus produce blood cells – red bone marrow blood cells, platelets

Functions of Bone – yellow bone marrow mostly fat – fills cavities of adult long bones can be converted into red bone marrow – times of severe blood loss

Bone Growth / Renewal adjusts bone strength and helps maintain Ca levels – osteoblasts – osteoclasts compact bone – resists mechanical shock spongy bone – pockets with open spaces – often filled with red bone marrow

Long bone formation Bone Structure

Structure of a femur Bone Structure

Bone Density Exercise can increase bone density Osteoporosis is a decrease in bone density – May occur when the action of osteoclasts outpaces that of osteoblasts – May also occur as a result of inability to absorb calcium

Bone Density

Joints areas of contact or near contact between bones 3 types – fibrous joints exist between cranial bones immovable

Joints – cartilaginous joints between vertebrae slightly moveable

Joints – synovial movable joints ligaments – connect bone to bone – osteoarthritis cartilage wears away – rheumatoid arthritis joint members become inflamed

Tendons Attach Muscle to Bone muscle tendon bursae synovial cavity

Impacts, Issues Video Pumping Up Muscles

Muscle contraction overview Muscle Contraction

Muscles 3 types – smooth – cardiac – skeletal maintains posture allows movement maintains body temperature provide joint stability contraction of muscle causes ATP breakdown

Structure of skeletal muscle Skeletal Muscle Structure

A muscle is made up of muscle cells A muscle fiber is a single muscle cell Each fiber contains many myofibrils – contain actin and myosin filaments Sacromere – functional unit of a muscle

Muscle Bundle of muscle fibers Nuclei Z lines Myofibril Single muscle fiber (cell) Sarcomere Plasma membrane

Structure of a sarcomere Sarcomere

Muscles components – sarcolemma cell membrane of muscle cell – sarcoplamsic reticulum stores Ca – essential for muscle contraction – myofibrils have striations formed by units called sarcomeres – myosin – actin

Muscle Microfilaments thin filaments like two strands of pearls twisted together pearls are actin other proteins in grooves in filament thick filaments composed of myosin each myosin molecule has tail and a double head

Muscles sliding filament model – controlled by troponin and tropomyosin – actin filaments slide past mysoin – sarcomeres shorten

Nervous System Controls Contraction Signals from nervous system travel along spinal cord, down a motor neuron Endings of motor neuron synapse on a muscle cell at a neuromuscular junction

Neuromuscular Junction Axon terminal fits into depression in sarcolemma Nerve impulse travels down axon to axon terminal ACH is released into synaptic cleft and binds with receptor sites Travels into T-tubules which cause Ca to be released from sarcoplasmic reticulum – Ca alters the configuration of actin and causes a change in binding site on actin

Troponin and Tropomyosin lie in groove in actin filament when muscle is relaxed, tropomyosin blocks myosin binding site myosin binding site blocked actin troponin

Troponin and Tropomyosin when troponin binds calcium ions, it changes shape and moves tropomyosin cross-bridge formation and contraction can now proceed myosin head actin

Troponin and tropomyosin Troponin and Tropomyosin

Neuromuscular Junction Ach – contraction – activates release of Ca Ache – relaxation – recyles Ach – causes Ca to be reabsorbed into sarcoplasmic reticulum

Sliding filament model Muscle Contraction

Contraction Requires Energy muscle cells require huge amounts of ATP energy to power contraction the cells have only a very small store of ATP three pathways supply ATP to power muscle contraction

Energy Pathways creatine phosphate – storage form – gets things started – donates a phosphate to APD aerobic Respiration – primary source – produces 20 times the ATP – takes longer to produce anaerobic Respiration – produces ATP faster than aerobic – cost  build up of lactic acid

Energy sources for contraction ATP for Contraction

Pathway 1 Dephosphorylation Creatine Phosphate Pathway 2 Aerobic Respiration Pathway 3 Glycolysis Alone creatine oxygen glucose from bloodstream and from glycogen break down in cells ADP + P i relaxation contraction

Motor Unit one neuron and all the muscle cells that form junctions with its endings when a motor neuron is stimulated, all the muscle cells it supplies are activated to contract simultaneously each muscle consists of many motor units

Types of contractions Muscle Contractions

Muscle Fatigue An inability to maintain muscle tension Occurs after a period of tetanic contraction Different types of muscle show different fatigue patterns