11.2 - movement Flashcards
1
Q
what is an exoskeleton?
A
- the external skeleton surrounds and protecting most of the body surface of animals including insects and crustaceans
2
Q
what are bones?
A
- the internal skeletons found in animals with an endoskeleton such as mammals and fish
3
Q
what are muscles?
A
- connected to the outside of bones by tendons, and attached to the
insides of exoskeletons
4
Q
what are levers?
A
- Bones and exoskeletons facilitate movement by providing an anchor for muscles, thus acting as levers.
- This allows for changing size and direction of forces generated.
- The relative position of the effort force (E), the fulcrum (F, aka pivot point), and the resultant force (R); in which these determine the class of lever
5
Q
what are Synovial joints?
A
- The structure of a joint (joint capsule and ligaments) determines the movements that are possible
- Synovial joints are the most movable joints in the body and therefore provide the greatest range of motion
6
Q
what is synovial fluid?
A
- In synovial joints, the surfaces of the bones are covered in a thin layer of strong cartilage and a very thin layer of slippery joint fluid
7
Q
what are skeletal muscles?
A
- Skeletal muscles occur in pairs and are called antagonistic because when one muscle contracts, the other relaxes
- antagonistic muscles produce opposite movements at a joint
- the elbow joint, the triceps extends the forearm and the biceps flex the forearm
8
Q
drawing a diagram of an elbow?
A
- include cartilage, synovial fluid, joint capsule, named bones and named antagonistic muscles
- elbow joint works on both a hinge
joint and pivot joint –together it allows for a vast range of movements - joint is where the bones meet
- cartilage is tough, smooth tissue that prevents bones rubbing together (friction) and absorbs shocks to decrease fractures of bones
- Synovial fluid fills the cavity between the joint and cartilage
- The joint capsule is a tough ligamentous covering to the joint
9
Q
what are the Antagonistic pairs in an insect leg?
A
- The hindlimb of a grasshopper is specialised for jumping, and it is a jointed limb with three parts
- When the grasshopper prepares to jump, the flexor muscles will contract and the extensor muscles relax (antagonistic pair), bringing the femur and tibia closer together. This is known as flexing
- When the extensor muscles contract and the flexor muscles relaxes, the tibia is extended and it produces a powerful propelling force
10
Q
what is the structure of a skeletal muscle?
A
- Skeletal muscles are attached to bones (outside) and used to move the body
- Skeletal muscles consist of bundles of large multinucleate striated cells called muscle fibres
- The term fibres is used as it provides structural support, and it is striated as the muscles viewed using a microscope will have visible stripes
11
Q
what is the structure of muscle cells?
A
- Each muscle cell is surrounded by a plasma membrane called the sarcolemma
- The muscle cell has special cytoplasm called sarcoplasm
- An internal membrane called the sacroplasmic reticulum (SR) conveys the signal for muscle contraction
- Large numbers of mitochondria are present to provide sufficient ATP for muscle contraction
12
Q
what are Myofibrils?
A
- sacroplasmic reticulum surrounds structures called myofibrils found inside each muscle cell
- myofibrils are thin parallel and elongated fibres
- has alternating light and dark bands, which gives the striped pattern on skeletal muscles
- the centre of each light band is a discshaped structure called the Z-line
13
Q
how are Myofibrils made up of sacromeres?
A
- The sacromere is the functional unit of the muscle.
- The myofibrils are divided into compartments by Z-lines.
- The distance between two Z-lines is called the sacromere.
- Therefore, myofibrils consist of repeating units called sacromeres.
- Myofibrils have two types of myofilaments: myosin and actin.
- Both myosin and actin are proteins.
- The myosin filaments are thick and seen as dark bands.
- The actin filaments are thin and seen as light bands.
- Actin filaments are attached to one end of the Z-line.
- Six actin filaments surround one myosin filament to form cross-bridges during contraction.
14
Q
drawing the sacromere.
A
- Diagrams of the sacromere structure should include Z-lines, actin filaments, myosin filament heads, and the region of light and dark bands.
15
Q
how is a muscle contracted?
A
- The contraction of muscle is due to the sacromeres in the myofibrils becoming shorter.
- This is achieved by the sliding of actin and myosin filaments over each other with the use of energy (ATP).
- Contraction shortens the sacromeres by about 35% and therefore shortens the overall length of the muscle fibres.
- However, it does not change the length of the thick (myosin) and thin (actin) filaments.
16
Q
how are muscle contraction controlled with ATP and Ca2+ ions?
A
- depolarisation and calcium (Ca2+) ion release,
- actin and myosin cross-bridge formation,
- sliding mechanism of actin and myosin filaments, and
- sacromere shortening for muscle contraction.
17
Q
how does Depolarisation and calcium (Ca2+) ion release work?
A
- action potential from a motor neuron triggers the release of acetylcholine into the motor end plate
- causes the sacrolemma to depolarise and this is transmitted down the T-tubules to all muscle fibres.
- This triggers the release of calcium (Ca2+) ions from the sacroplasmic reticulum
18
Q
how does the Actin and myosin cross bridge formation work?
A
- Actin filaments have a binding site for the myosin heads and also have two proteins, tropomyosin and troponin
- In a relaxed muscle, tropomyosin blocks the myosin binding sites on actin by forming two strands that wind around the actin filament
- Ca2+ ions bind to troponin, troponin
causes the myosin to move and so it reconfigures the complex to expose the myosin binding sites - myosin filament heads can attach to the binding side of actin filaments in order to pull them together for cross-bridge formation.
19
Q
how does the Sliding mechanism of actin and myosin filaments work?
A
- ATP binds to the myosin head and causes it to break the cross-bridges between actin and myosin
- The myosin head gains energy from the hydrolysis of ATP to ADP and Pi, and changes shape ready to bind to the next binding site on actin
- The myosin head binds to the new exposed actin binding site and returns to the original conformation.
- This reorientation drags the actin further from the centre along the myosin in a sliding mechanism.
- The ADP and Pi are released, and the myosin head push the actin filament towards the centre of the sacromere.
- This is called the power-stroke
20
Q
how does the Sacromere shortening for muscle contraction.
A
- The repeated reorientation of the myosin heads drags the actin filaments along the length of the myosin.
- As the actin filaments are anchored to the Z-lines, the Z-lines are pulled closer together; thus shortening the sacromere.
- As individual sacromeres become shorter, the muscle fibres as a whole contracts.
- When no more nerve impulse arrives, Ca2+ ions move back into vesicles of the sacroplasmic reticulum by active transport.
- The binding sites on actin are covered again and the muscle relaxes.
21
Q
how to look at a muscle contraction.
A
- Next to the Z-line is the light band of actin, this is called the I band (i for light).
- The I band is longer in a relaxed muscle.
- In the centre of the sacromere is the darkest band consisting of myosin and actin, this is called the A band (a for dark).
- There is no change in length of the A band in both relaxed and contracted muscle.
- In the centre of the A band is a grey zone of only myosin. This is called the M-line.
- In a relaxed muscle, there is more visible light on either side of the M-line.
- The Z-lines are farther apart when the sacromere is relaxed, and so the light bands are wider for a longer sacromere.
- The Z-lines are closer together when the sacromere is contracted, and so the sacromere is shorter as the myosin and actin have slid over one another.
- The I band becomes smaller and there is less light on either side of the M-line.
22
Q
what are the results of Muscle contractions and fluorescence studies?
A
- Fluorescence is the emission of electromagnetic radiation, often visible light, by a substance after it has been illuminated by electromagnetic radiation of a different wavelength
- Muscle research relies on fluorescence, in particular calcium-sensitive bioluminescent protein, aequorin found in Aequorea victoria (jellyfish)
- injected into giant single muscle fibres of Balanus nubilus and the when muscles were stimulated, there was a strong bioluminescence coinciding with the release of Ca2+
from the sacroplasmic reticulum. The bioluminescence decreased as the stimulus was removed. - Separately, scientists cut open Nitella axillaris cells that have a network of actin filaments below the membranes.
- Researchers added a fluorescent dye to myosin molecules to show that myosin “walks along” actin filaments. Researchers also showed the ATP-dependence of myosin too
