Movement and Locomotion Ch. 49 AP Biology Ms. Haut

Locomotion Requires energy to overcome friction and gravity Swimming – Buoyancy reduces gravity issue – Density of water increases friction problem – Shape of organism reduces this problem Locomotion on land – Development of body support and ability to move against gravity and maintain balance Flying – Development of wing structure and ability to develop “lift”

Skeletal Support Essential Cniderians, flatworms, nematodes, and annelids have a Hydrostatic skeleton Movement due to muscles changing shape of fluid- filled compartments Nematodes-longitudinal muscles lead to thrashing Segmented worms-circular and longitudinal muscles lead to Peristalsis

Skeletal Support Essential Exoskeleton-hard encasement deposited on surface of animal – Mollusks have calcareous shells – Arthropods have jointed exoskeleton called cuticle-composed of chitin

Skeletal Support Essential Endoskeleton- consists of bones, buried within soft tissue – chordates

Muscles Move Skeletal Parts Skeletal Muscle – Each muscle fiber is a single cell with many nuclei – Each fiber is composed of a bundle of myofibrils which contain myofilaments Thin filaments—2 strands of actin Thick filaments—staggered arrays of myosin – Striated appearance due to sarcomeres (basic functional unit)

Muscle Contractions: “Sliding-Filament Model” Thin and thick filaments of the sarcomere slide past one another to shorten the length of the muscle

Cyclic Interaction Between Actin and Myosin in Muscle Contraction

Sliding-Filament Model

4.Ca++ binds Troponin 5.Troponin moves Tropomyosin 6.Tropomyosin uncovers myosin binding site on actin 7.Myosin binds actin uses ATP to "rachet" once releases, "unratchets", and binds to next actin 8.Myosin pulls actin chain along in one direction 9.Sarcomere shortens (Z discs move closer together) 10.Whole fiber shortens, Contraction!Contraction! 11.Ca++ ATPase pumps restore Ca++ to S.R Relaxation!

Fast Twitch Muscles Short contraction-relaxation cycles (~30 ms), e.g. muscles that move the eyes Fibers adapted to produce rapid contractions Contain many mitochondria and sarcoplamsmic reticulum to produce a lot of Ca ++ Tire easily. Contain little myoglobin (oxygen- binding proteins) Contain few capillaries. Make up white muscle

Slow Twitch Muscles Long contraction-relaxation cycles (~3 s), e.g. muscles in back to maintain posture Fibers adapted to produce prolonged, steady contractions Contain more mitochondria than fast twitch and do not have or need a lot of Ca ++ Contain a lot of myoglobin (oxygen-binding proteins) Extensive capillaries. Make up red muscle.