1. Support and Locomotion

2. Muscles Muscles work by contracting: getting smaller in size
Three types of muscles
Skeletal (Striated, voluntary)
Cardiac (Heart)
Smooth (Involuntary)

4. Skeletal Muscle Called striated because of how it looks
Responsible for voluntary actions
Human body has over 700 different skeletal muscles (this makes up ~35% to 45% of the total body weight!)
SkM contracts by having two proteins, actin and myosin, slide past each other

5. Skeletal Muscle
The sarcomere is the functional unit of muscle contraction
Thin filaments consist of two strands of actin and one tropomyosin coiled about each other
Thick filaments consist of myosin molecules

6. Actin (thin filament) and myosin (thick) slide past each other
Myosin has little “feet” called cross-bridges

7. Skeletal Muscle
At rest, tropomyosin blocks the myosin binding sites on actin

8. Skeletal Muscle
When Ca2+ binds to the troponin complex, a conformational change results in the movement of the tropomyosin tropinin complex and exposure of actin’s myosin binding sites

9. Skeletal Muscle
Using ATP, cross-bridges from myosin “grab” binding sites on actin and pull the filaments closer
This action occurs over and over until the muscle fiber is completely contracted

12. Muscles are controlled by the Nervous System
Action potentials run along a neuron until they reach a synapse, where they release neurotransmitters (ACh)
Once at the muscle cells, the action potential releases Ca2+ from the sarcoplasmic reticulum
The Ca ions allow the proteins on the actin and myosin to bind, forming the cross-bridges

14. Cardiac Muscles Cardiac muscles are those that power the heart
Very similar to SkM, except CM is controlled by the SA node, not a motor neuron

15. Smooth Muscles
SmM surround blood vessels and most hollow organs: uterus, bladders, GI tract
Most SmM contraction is slow and sustained, sometimes rhythmic (peristalsis)

16. Smooth Muscles
SmM contraction can be initiated by stretching, hormones, or the nervous system
Most are involuntary, but some can be controlled (urinary bladder)

17. ATP
Large amounts of ATP are required for muscle contraction AND relaxation
Breaks/reforms connections between actin and myosin
Powers pumps that return Ca2+ to the sarcoplasmic reticulum

18. Rigor mortis Stiffening of muscles after death
Muscles run out of ATP after death
Connection between actin and myosin cannot be broken – muscle remains contracted
After ~72 hours, relaxation occurs because of decomposition

19. Skeletons What do skeletons do?
Provide the framework for support of the body
Three basic types:
Hydrostatic Skeleton
Exoskeleton
Endoskeleton

20. Hydrostatic Skeletons
fluid pressure provides support (Cnidarians, Annelids)

21. Exoskeleton
Encase the bodies of Arthropods (insects, crustaceans, and arachnids)
Made of proteins, chitin, or are calcareous
Thin exoskeleton where the animal needs to bend or move

22. Crustacea, Molluska, and Insecta

23. Endoskeleton Found in Echinoderms, Chordates, and Sponges
Serve several functions for vertebrates:
Supports body and protects internal organs
Used as muscle attachment sites to allow locomotion

24. Produce blood parts (RBC’s, WBC’s, and platelets
Serve as storage sites for Calcium and Phosphorus
Some even aid in sensory transduction (hammer, anvil, and stirrup of the middle ear)

25. Cartilage
Consists of chondrocytes embedded in a collagen/elastin matrix
Located at ends of long bones and between vertebrae
Functions as shock absorber

26. Bones
Compact bone provides strength and rigidity as well as attachment sites for muscles
Spongy bone is very porous; site where blood cells are produced (bone marrow)

27. How does the body move? Muscles work in antagonistic pairs
One always extends (bends out) while the other always flexes (bends in)

28. How does the body move?
A muscle attaching two bones is attached to one fairly immovable bone (origin) and one that moves (insertion)
Tendons connect muscle to bone
Ligaments connect bone to bone

30. Joints are where two bones meet
Three basic types of joints:
Fixed: Skull
Hinge: Elbows and knees
Ball-and-Socket: Shoulders and hips

32. Arthritis (joint inflammation)
Osteoarthritis (“wear-and-tear” arthritis)
Cartilage covering the ends of bones slowly wears away, causing stiffness and soreness
Rheumatoid arthritis
Autoimmune disease in which the body’s immune system attacks the synovial membranes