1. Animal Movement
Chapter 30

2. Overcoming Forces

3. Skeletal Support Hydrostatic Exoskeleton Endoskeleton
Soft bodies: hydra, earthworm
Fluid filled cavity – remember water is not compressible
Exoskeleton
Hard external skeleton: arthropods (chitin ), mollusks (calcium carbonate)
Shell of nonliving material secreted by living cells
Exoskeleton is molted occasionally during growth or outer edge is added
Endoskeleton
Hard elements alongside soft tissue
Vertebrates – cartilage and bone, echinoderms – inorganic material

4. Human Skeleton Ancestral traits – 375 myo tetrapod body plan
Axial skeleton
Appendicular skeleton
Bipedalism frees hands for other uses
Vertical backbone supports weight unevenly
Flexible joints provide versatility
Ligaments hold bones together
Ball-and-socket joint
Hinge joint
Pivot joint

5. Bone Structure Bones are complex living organs
Living cells secrete the bone matrix
Calcium and phosphate (hard) and collagen (flexible) make up the matrix
Yellow bone marrow stores fat
Red bone marrow produces RBCs

6. Bone Health Bone repair – bones are continually being repaired
Bone fractures heal stronger so long as the bone remains immobilized for a period of time
Osteoporosis is the result of slow replacement of bone tissues
Becoming more common, even in men
Bones need stress to remain strong

7. Muscle-Skeleton Pairing
Muscles attach to bone via tendons
To move in two directions muscles are arranged in antagonistic pairs
Ex. Triceps and biceps
One muscle is contracted while one is relaxed

9. Structure of Skeletal Muscle
Skeletal muscle attaches to bone, moves body
One muscle fiber contains many myofibrils
Sarcomeres are the repeating units of myofibrils
Thin filament – actin
Thick filament – myosin

10. Muscle Contraction
Sliding-filament model of muscle contraction – follow z-lines
Motor neuron allow interaction between actin and myosin, ATP allows for movement

11. Sliding filament

12. Motor Neurons
Neuron cell bodies in CNS transmit action potential via axon
Axon forms neuromuscular junctions with muscle fibers
Acetylcholine is released across junctions making muscle fibers contract
Acetylcholine in muscle cells causes the release of calcium ions (Ca2+) from the ER (endoplasmic reticulum)
Ca2+ allows for interaction between thick and thin filaments by removing the barrier (regulatory protein) between them
Muscle contraction force is dependent on the number of motor neurons activated