Movement and LocomotionMovement and Locomotion

Ch. 49

AP Biology

Ms. Haut

LocomotionLocomotion

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 Skeletal Support EssentialEssential

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 EssentialSkeletal Support Essential

Exoskeleton-hard encasement deposited on surface of animal– Mollusks have calcareous shells– Arthropods have jointed exoskeleton called

cuticle-composed of chitin

Skeletal Skeletal Support Support

EssentialEssentialEndoskeleton-

consists of bones, buried within soft tissue– chordates

Muscles Move Muscles Move Skeletal PartsSkeletal 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: Muscle Contractions: “Sliding-Filament “Sliding-Filament

Model”Model”Thin and thick filaments of

the sarcomere slide past one another to shorten the length of the muscle

Cyclic Interaction Between Actin Cyclic Interaction Between Actin and Myosin in Muscle Contractionand Myosin in Muscle Contraction

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! 11. Ca++ ATPase pumps restore Ca++ to S.R. ...... Relaxation!

Fast Twitch MusclesFast 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 MusclesSlow 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.