B.1: Muscles & Movement

Joints Joints = articulation or arthrosis Joints allow the movement of our body and hold it together. Joints include bones, ligaments, muscles, tendons, and nerves.

Types of Joints

B.1.1 – The role of bones in human movement Bones are organs made up of different types of tissues. Functions: Hard “framework” for body support Protection of organs and soft tissue Form blood cells in bone marrow Store minerals, especially Calcium and Phosphorus Act as levers for movement

B.1.1 – The role of muscles in human movement Muscles provide the force necessary for movement. This happens by shortening their cells (muscle fibers) when the nerve signals. They must exist as antagonistic pairs, so that the body part can return to normal after one muscle contracts.

B.1.1 – The role of tendons in human movement Tendons attach muscles to bones – this is essential for movement. Tendons are cords of dense connective tissue. By acting as levers, bones magnify the force provided by muscles.

B.1.1 – The role of ligaments in human movement Ligaments are tough, band-like structures that strengthen and stabilize the joint. Ligaments connect bone to bone.

B.1.1 – The role of nerves in human movement Nerves send the signal to muscles of when to contract. Special nerves in ligaments allow proprioception (your body’s ability to sense it’s own position & movement). This helps prevent over-extension of the joint.

B.1.2 – Hinge Joint: Human Elbow Joint B.1.2 – label a diagram of the human elbow joint, including: cartilage, synovial fluid, joint capsule, named bones (radius, ulna ,humerus) antagonistic muscles (biceps and triceps).

Pictures

Quick Video: http://www.youtube.com/watch?v=o2DpznoBqNY

Joint Part Function Humerus Acts as a lever that allows the origin of the elbow muscles. Radius Acts as a lever where the biceps muscle inserts. Ulna Acts as a lever where the triceps muscle inserts. Biceps muscle Contracts to cause flexion (bending) of the arm. Triceps muscle Contracts to cause extension (straightening) of the arm. Tendons Attach muscle to bone. Ligaments Connect bone to bone. Cartilage Reduces friction & absorbs compression Synovial fluid Lubricates to reduce friction and provide nutrients to the cells of the cartilage. Joint capsule Surrounds the joint, encloses the synovial cavity, and unites the connecting bones.

B.1.4 – Hinge Joint: Knee The knee is a freely movable (diarthrotic) joint

B.1.4 – Ball and socket joint: Hip The hip joint is also diarthrotic, but has many different types of movement possibilities.

Hip vs. Knee Joints Hip Joint Knee Joint Freely movable Ball-like structure of femur fits into a cup-like depression in hip (the acetabulum) Convex surface fits into a concave surface. Movements = flexion, extension, abduction, adduction, circumduction and rotation. Movements = flexion & extension in one direction

Muscle Contraction – “sliding filament hypothesis” http://www.youtube.com/watch?v=0kFmbrRJq4w http://www.youtube.com/watch?v=InIha7bCTjM

Process of Contraction 1. Nerve signal (action potential) travels to the end of a motor neuron (nerve that controls a muscle). End portion is called a synaptic end-bulb. Motor Neuron Synaptic end bulb Membrane Inside of muscle cell Point of connection = neuromuscular junction

2. Synaptic vesicles within neuron dump Acetylcholine (ACh) into synapse (gap between the neuron and muscle) ACh diffuses across to muscle and lands on ACh receptor proteins. Membrane AcetylCholine ACh receptor proteins

3. ACh receptors start a new action potential (A. P 3. ACh receptors start a new action potential (A.P.) that spreads out across the sarcolemma. They will continue to send out A.P. until the Ach is broken down.

4. A.P. spreads out across the sarcolemma and deep within muscle fiber via transverse tubules 5. As the action potential passes by sarcoplasmic reticulum (SR) the SR release Ca +2 which diffuse to the thin (actin) filaments.

6. Thin filaments are made of actin (to which myosin heads can attach). Ca +2 binds to actin , making it change shape so that it can accept myosin heads

7. Myosin heads (with an attached ADP + P) binds to actin, forming a cross-bridge. This triggers the heads to bend, pulling on the thin filaments towards the H Zone using energy of the now released ADP + P to shorten the sarcomere.

8. ATP will attach to myosin causing it to release the actin 8. ATP will attach to myosin causing it to release the actin. Thus, the cross-bridges are broken. The crossbridges will reattach further down on actin and keep pulling as long as there is Ca+2 and ATP is available.

9. Once the action potential stops, SR pump Ca+2 back in (using ATP). Muscle contraction ends.

Muscle fibers Stages: fully relaxed, slightly contracted, moderately contracted, fully contracted