Chapter 11.2 Flashcards
What are the body systems responsible for the control of movement?
-Skeletal system: consists of bones that act as levers and provide a structure for the muscles to pull
-Muscular system: muscles deliver the force required to move one bone in relation to another
-Nervous system: delivers signals to the muscles which cause them to contract and create movement
What are skeletons?
A rigid framework that function to provide support and protection for body organs
What are the different types of skeletons?
Endoskeleton which consists of numerous bones and Exoskeleton which is made of connected segments
How do skeletons facilitate movement in organisms?
Provide a surface for muscle attachment
What are ligaments?
Bones connected to other bones
What are tendons?
Bones connected to muscles
What are synovial joints?
Are capsules that surround the articulating surfaces of two bones
What is the function of joints?
To maintain structural stability by allowing certain movements but not others
What are the three main features of a synovial joint?
Joint capsule – Seals the joint space and provides stability by restricting the range of possible movements
Cartilage – Lines the bone surface to facilitate smoother movement, as well as absorbing shock and distributing load
Synovial fluid – Provides oxygen and nutrition to the cartilage, as well as lubrication (reduces friction)
What are the six types of synovial joints?
Plane joints (least mobility), hinge joints, pivot joints, condyloid joints, saddle joints, ball and socket joints (most mobility)
What type of joint is the human elbow?
Hinge joint
Where is the elbow joint found?
Between the humerus and ulna/radius
What bones does the muscle connect?
A static bone to a moving bone
How do skeletal muscles exist?
In antagonistic pairs
What are examples of opposing movements?
Flexion vs extension, abduction vs adduction, protraction vs retraction
What allows insects to jump?
Hind legs
What are the different parts of the exoskeleton of the hind leg?
Femur (upper leg), tibia (middle leg) and tarsus (lower leg)
How are the femur and tibia connected?
By 2 antagonistic muscles: flexor tibiae muscle and extensor tibiae muscle
How does the insect prepare for pushing off the ground when jumping?
When the flexor muscle contracts, the extensor muscle relaxes and the tibia and femur are brought closer together
How does the insect eventually jump?
When the extensor muscle contracts, the flexor muscle relaxes and the tibia is pushed away from the femur
What are skeletal muscles consisted off?
Tightly packaged muscular bundles surrounded by connective tissue
What are muscular bundles consisted off?
Muscle fibers which are formed from the fusion of muscle cells
What are the muscle fibers made of?
Myofibrils which run the length of the fiber and is responsible for muscle contraction
How can the myofibrils be divided?
Into sarcomeres which represent one contractile unit
What are the features of muscle fibers which facilitate muscle contraction?
-They are multinucleate
-They have a large number of mitochondria
-Sarcoplasmic reticulum that stores calcium ions
-Tubular myofibrils made up of two different myofilaments – thin filament (actin) and thick filament (myosin)
-Sarcolemma that contains invaginations called T tubules
How are the myofilaments held in a sarcomere?
By dense protein discs called Z lines
How are the myosin filaments held in place?
Due to the actin filaments that radiate from the Z lines
What is the A band?
Centre of the sarcomere that appears darker due to the overlap of both actin and myosin filaments
What is the I band?
Peripheries of the sarcomere that appear lighter as only actin is present in this region
What is the H zone?
Area where only myosin is present
What is the first step of muscle contraction and how does it happen?
Depolarization and Calcium Ion Release. An action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
Acetylcholine initiates depolarization within the sarcolemma, which is spread through the muscle fiber via T tubules Depolarization causes the sarcoplasmic reticulum to release stores of calcium ions (Ca2+)
What is the second step of muscle contraction and how does it happen?
Actin and Myosin Cross-Bridge Formation. On actin, the binding sites for the myosin heads are covered by a blocking complex (troponin and tropomyosin). Calcium ions bind to troponin and reconfigure the complex, exposing the binding sites for the myosin heads. The myosin heads then form a cross-bridge with the actin filaments
What is the third step of muscle contraction and how does it happen?
Sliding Mechanism of Actin and Myosin. ATP binds to the myosin head, breaking the cross-bridge between actin and myosin. ATP hydrolysis causes the myosin heads to change position and swivel, moving them towards the next actin binding site
The myosin heads bind to the new actin sites and return to their original conformation. This reorientation drags the actin along the myosin in a sliding mechanism
What is the last step of muscle contraction?
Sarcomere Shortening. As actin filaments are anchored to Z lines, the dragging of actin pulls the Z lines closer together, shortening the sarcomere. As the individual sarcomeres become shorter in length, the muscle fibers as a whole contracts
