Module 11: Human Health and Physiology II 11.2 Muscles and Movement

Assessment Statements State the roles of bones, ligaments, muscles, tendons and nerves in human movement. Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps). Outline the functions of the structures in the human elbow joint named in Compare the movements of the hip joint and the knee joint. Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcplasmic reticulum, nuclei and the sarcolemma. Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands. Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads. Analyse electron micrographs to find the state of contraction of muscle fibres.

State the roles of bones, ligaments, muscles, tendons and nerves in human movement. Also acts as source of blood cells/storage of minerals Attached to bones for movement

Label a diagram of the human elbow joint, including cartilage, synovial fluid, joint capsule, named bones and antagonistic muscles (biceps and triceps). The elbow is a hinge joint that acts similarly to a door. (Also called a synovial joint) Joint capsule

Antagonistic pair Arm flexed- 1. Biceps contracted (Thick and short) 2. Pull up Radius 3. Triceps relaxed (Long and thin) Arm extended- 1.Triceps contracted (Thick and short) 2. Pull down Ulna 3. Biceps relaxed (Long and thin) Scapula Radius Ulna Look at the videovideo

Outline the functions of the structures in the human elbow joint named in Joint PartFunction Cartilage Synovial fluid Joint capsule Tendons Ligaments Biceps muscle Triceps muscle Humerus Radius Ulna

Compare the movements of the hip joint and the knee joint. Hinge Joint: Knee joint Ball and socket: Hip joint Both of these joints are also referred to as diarthrotic joints – joints that are freely movable

Compare the movements of the hip joint and the knee joint. Task: Complete the following table using page 294 for reference, CharacteristicHip jointKnee joint Diarthrotic? Type of movements Possible movements Structure Yes Multiple angular motions Rotational Angular motion in one direction Flexion, extension, abduction, adduction, circumduction, rotation Flexion and extension Ball that fits into depression Convex surface fits into concave surface

Compare the movements of the hip joint and the knee joint.

Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcplasmic reticulum, nuclei and the sarcolemma. Striated (skeletal) muscle 1.Tendons 2.Muscle 3.Muscle bundle 4.Muscle fibre (cell) 4. Muscle cells are multi-nucleated and the plasma membrane is called the sarcolemma. Each cell is made up of multiple myofibrils. The sarcoplasmic reticulum is like the ER.

Describe the structure of striated muscle fibres, including the myofibrils with light and dark bands, mitochondria, the sarcplasmic reticulum, nuclei and the sarcolemma. Myofibril 4. Sarcomeres are repeating units of movement that make up myofibrils (from Z line to Z line). It’s made up of myosin and actin filmaents Dark band Light band

Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands. Myosin head

Draw and label a diagram to show the structure of a sarcomere, including Z lines, actin filaments, myosin filaments with heads, and the resultant light and dark bands. ActinMyosin H zone A band I band M line Task: Complete the following table by looking at the diagram      What happens during muscle contraction?muscle contraction

Sarcomere before and after:

Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads. The Sliding Filament Theory of Muscle Contraction 1. Action potential arrives at the neuromuscular junction. Achetylcholine is released and binds to receptors on the sarcolemma. T tubules spread the action potential and the sarcoplasmic reticulum releases Ca 2+ into the sarcoplasm

At rest, the actin-myosin binding site is blocked by tropomyosin, held in place by troponin Myosin heads cannot bind to actin filaments Myosin is bound to ATP (ADP + P i ) actin filament troponin tropomyosin myosin complex myosin filament ADP PiPi Rest

Ca 2+ (from sarcoplasmic reticulum) binds to troponin, changing its shape As a result, tropomyosin is pulled out of the binding site and this exposes the myosin binding site on actin Ca 2+ troponin

Ca 2+ activates ATPase, breaking down ATP to ADP + P i Myosin binds to actin to form crossbridge after the P i is released Energy provided moves the myosin head forward, pulling acting filament along in what is known as the power stroke. The ADP is released in the process ADP PiPi Ca 2 +

Free ATP binds to head, changing myosin back to its original shape Actin-myosin cross bridge breaks (site if occupied by ATP) The head returns to original shape

With continued stimulation the cycle is repeated

If stimulation ceases, Ca 2+ is pumped back into sarcoplasmic reticulum Troponin and tropomyosin return to original positions Muscle fibre is relaxed

Important points to note: The lengths of actin and myosin DO NOT change; they simply slide over each other The I band and H band disappear Myosin heads move towards the middle pulling actin towards the M line.

Explain how skeletal muscle contracts, including the release of calcium ions from the sarcoplasmic reticulum, the formation of cross-bridges, the sliding of actin and myosin filaments, and the use of ATP to break cross-bridges and re-set myosin heads. Task 1: Using the link, complete the assessments and make any necessary additions to your notes: s/student_resources/shared_resources/animations/m uscles/muscles.html Task 2: Arrange the key events of the sliding filament theory into the correct order

Analyse electron micrographs to find the state of contraction of muscle fibres. Which one is contracted and which one is relaxed? How do you know?