IB Standards / Review

Annie Lee, Sarah Bartley, Lauren Thames

Skeletons

The three main functions of a skeleton: support, protection, and movement (11.2.1)

A hard skeleton provides protection for soft tissues and provides a framework for our bodies.– Name some examples?

Three types of skeletons– Hydrostatic skeletons, Exoskeletons, and

Endoskeletons

Hydrostatic Skeletons

Consists of fluid held under pressure in a closed body compartment– Cnidarians, flatworms,

nematods, and annelids These animals are able

to change shape because of the fluid-filled compartments– Flexibility– Ex. Worms.

Exoskeletons

This type of skeleton is a hard encasement deposited on the surface of the animal.

Ex. Molluscs Arthropods have cuticle

exoskeletons, a non-living coat. The cuticle contains chitin (polysaccharide similar to cellulose).

Endoskeleton

Consists of hard supporting elements, like bones.– Buried within the soft

tissues of an animal.

Echinoderms have endoskeletons of hard plates called ossicles beneath their skin.– Sea urchins vs. Sea

Stars

Joints

IB specifically wants you to know the human elbow joint. (11.2.2)

Specifically the cartilage, synovial fluid, joint capsule, named bones, and antagonistic muscles. – Make sure you can label

these things !!

Elbow Joint Continued

IB also wants you to know the functions of the structures in the human elbow joint (11.2.3)

Cartilage– A type of connective tissue with an abundance of collagenous fibers

embedded in chondroitin sulfate.– Cartilage is retained in certain locations

• Disks that acts of cushions between vertebrae and the caps on the ends of some bones

• Absorbs physical impact Synovial Fluid

– Thick stringy fluid found in the cavities of Synovial joints.– Reduces friction between the cartilage and other tissues in joints

Joint Capsule (Articular Capsule)– Envelope surrounding the Synovial joint– Covers the end surfaces of bones

Joints Continued

Three types of joints: Ball-and-socket joint

– Where the Humerus contacts the shoulder girdle, and our femur contacts the pelvic girdle

Hinge Joint– Between the Humerus and the head of the Ulna

Pivot Joint– Same place above

The Hip Joint and Knee Joint

IB wants you to know the comparison between the knee joint and the hip joint (11.2.4)

Knee Joint– Hinge joint, and is the biggest joint in our body

Hip Joint– Ball-and-socket type of joint, specifically called a

synovial joint.

Muscles

The purpose of muscles is to provide movement to the body by the providing ability to move bones. (11.2.1. IB wants you to know the purpose of muscles)

The action of a muscle is to contract– Muscles only extend passively

Antagonistic pairs, each member of the pair working against each other.– Ex. Flexing an arm

Vertebrate Skeletal Muscle

The skeletal muscle Structure (11.2.5 IB

wants you to know the skeletal muscle structure and its components)– Hierarchy of smaller and

smaller units– A muscle fiber = bundle of

smaller myofibrils– Myofibrils = two types of

myofilaments (thin filaments and thick filaments)

Structure Continued

Thin filaments– Two strands of actin and one

strand of regulatory protein Thick filaments

– Staggered arrays of myosin molecules

The arrangement of myofilaments make a pattern of light and dark bands. Each repeating unit is called a sarcomere.

There are two bands– I Band: area near the edge of

sarcomere where there are only thin filaments

– A Band: broad region that corresponds to the length of the thick filaments

• There is an H zone, which is in the center of the sarcomere

The Structure of the Sarcomere

Things to note (11.2.6)– Z lines– Light band– Dark band– H zone

Sliding-Filament Model

When the muscle contracts, thin and thick filaments do not change in length when the sarcomere shortens

There is an overlap between both filaments instead. – Results in the I band and

the H zone shrinking

Sliding-Filament Model Continued The sliding/overlap of the filaments

result from Myosin-Actin interactions Take a look at the diagram

Myosin-Act Interaction (11.2.7. IB wants you to know

how this works…so pay attention)

Role of Calcium and Regulatory Proteins Skeletal fiber only contracts when

activated by a motor neuron. This is where the Calcium and

Regulatory Proteins come into work

Role of Calcium and Regulatory Proteins (11.2.7)

The Stimulus

The stimulation provided by the motor neuron is an action potential that makes a synapse with the muscle fiber.

The synaptic terminal releases neurotransmitters, called acetylcholine– Depolarization, causes it to produce action potential

The action potential spreads into …– A plasma membrane called transverse (T) tubules– And then the sarcoplasmic reticulum (SR) which the

tubes make close contact with• The action potential opens Calcium ion channels in

the SR• (look at diagram on pg. 1070)

A quick look at the standards..

11.2.1: State the roles of bones, muscles, etc in human movement

11.2.2: Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule…etc.

11.2.3: Outline the functions of the structures in the human elbow joint named in 11.2.2

11.2.4: Compare the movements of the hip joint and knee joint 11.2.5: Describe the structure of striated muscle fibers, including

myofibrils with light and dark bands… etc 11.2.6: Draw and label a diagram to show the sarcomere,

including Z lines, actin filaments, myosin..etc 11.2.7: Explain how skeletal muscle contracts, including the

release of calcium ions from the SR, formation of cross bridges…etc.