Muscles & Skeletons Flashcards
Hydrostatic Skeleton
Fluid held under pressure in a closed body compartment
Cnidarians
Jellyfish
1. Hydra can elongate by closing mouth
2. Muscles of gut cavity constrict
3. Water cannot be compressed
4. Therefore, decreasing cavity diameter forces length increase
How do flatwoms move
Movement results from localised muscle constriction on interstitial fluid.
How do nematodes move
Contractions of longitudinal muscles result in thrashing movements
Annelids
Use hydrostatic skeleton for peristalsis - control of form and movement using muscles to change shape of fluid filled segments
Structure of a worm
Made up of individual segments, each made up of circular and longitudinal muscle with bristles for anchorage
Hydrostatic skeleton pro and con
Pros - cushions organs for burrowing and crawling animals
Cons - Cannot support terrestrial activities off the ground (walking/running)
Exoskeleton
Hard encasement deposited on the surface of an animal
Molluscs
Snails, oysters etc
- Enclosed in CaCO3 shell
- Shell enlarged by adding to outer edge as animal grows
- Clams and bivalves hinge their shell by using muscles attached to the inside of the exoskeleton
Anthropods
Crickets, Bees, Xicadas
Exoskeleton is a cuticle, non-living coat secreted by epidermis
How do anthropods move
Muscles attach to knobs and plates on interior, joints have thing a flexible cuticle to allow movement
Anthropods cuticle composition
30-50% chitin and reminder is protein. Relative proportion of chitin and protein influence strength and flexibility.
Endoskeleton
Hard supporting elements such as bones buried in soft tissue
What kind of skeleton does a sponge have and why
Sponges have endoskeletons, their structure is internally reinforced by hard spicules of inorganic material or soft fibres of protein.
Echinoderms (kina)
Contains ossicles (hard plates) beneath skin that are MgCO3 and CaCO3 crystals bound together.
Sea stars vs Sea urchins ossicles
Ossicles are tightly bound in sea urchins as they have limited movement, however are loosely linked in sea stars to allow arms to change shape
What is a chordate
Vertebrates (endoskeleton)
Ligament
Connect bone to bone
Tendon
Connect muscle to bone
Axial Skeleton
Skull, vertebral column, rib cage
Appendicular Skeleton
Limb bones, pectoral and pelvic girdles
Ball and socket joint (example plus movement)
Humerus-shoulder, Femur Pelvic.
Allows rotation in several planes
Hinge Joint (example plus movement)
Humerus-Tibia, fingers, toes, ankles
Restrict movement to a single plane
Pivot (example plus movement)
Head on neck
Allows rotation
How does size correlate to structure
Animals body structure must support its size - Large animals have and NEED different proportions to small ones.
Skeletal Muscle
Bundle of long fibres running parallel to length of the muscle - one fibre = one cell
Myofibril
Tubular organelle containing thin and thick filaments
Thin Filament
Consist of two strainds of actin coiled together
What is thick filament made of
Myosin
Why is skeletal muscle called striated muscle
Regular arrangement of myofilaments create a pattern of light and dark bands
Sarcomere
Contains thin (actin) and thick (myosin) filaments
How do muscles contract
No change in filament length - thin and thick filaments overlap more.
Sliding filament model
Muscle contraction is based on the interaction between actin and myosin molecules. The “head” of a myosin molecule binds to an actin filament, forming a cross-bridge and pulling the thin filament toward the centre of the sarcomere.
Crossbridge
Forms when myosin head attaches to actin
How does sliding filment theory use energy
Myosin head hydrolyses ATP to ADP and inorganic phosphate, producing energy to allow it to propel the actin filament forward.
Speed of sliding filaments
- Each thick filament forms 350 heads. Each head forms and reforms 5 cross-bridges per second
How much muscle contraction does glycolysis support
1 minute of sustained contraction
How much muscle contraction does Aerobic respiration support
1 hour
What makes a skeletal muscle fibre to contract
Stimulation by a motor neuron
Why don’t myosin heads bind to binding sites at rest?
Myosin binding sites on thin filament are blocked by the regulatory protein, tropomyosin
What uncovers binding sites
Ca2+ ions bind to the tropomyosin and uncover binding sites
Synapse
Where motor neurons attach to muscle
What changes strength of contraction
Rate of signals that come down, number of motor neurons being operated, size of motor unit, action potential
What releases Ca2+ ions
Sarcoplasmic reticulum release them around the muscle which opens up binding sites to ALLOW myosin heads to attach and detach.
Prolonged contraction
Involved in maintaining posture - nervous system alternates activation along motor units in muscle (takes turns)
Tetanus
State of smooth and sustained contraction produced when motor neurons deliver a volley of action potentials (smooth, not jerky)
How does sliding filament theory create movement of bones
Muscles are attatched to bone by tendons and connective tissue. Muscle contraction stretches these structures, putting tension on bones.
Slow oxidative muscle
Operates slowly, need oxygen as part of the pathway to get energy
Fast oxidative
Fast operation, also need oxygen
What are fast glycolytic muscles
No oxygen involved, fast but cannot be sustained
Describe slow muscle fibres
Deliberate, slow, sustained. Less sarcoplasmic reticulum, slower calcium pumps, twitches last 5x longer
What are slow muscle fibres used for
Maintenance of posture can sustain long contractions
What are fast muscle fibres used for
Brief, rapid, powerful contraction
myoglobin
Found in oxidative fibers. Brown-red pigment in dark muscle tissue, binds oxygen more tightly than haemoglobin to supply more oxygen.
What determines the proportion of slow and fast fibres
We’re born with all three - genetic determines slow and fast but repeated high endurance activities can cause glycolytic fibres to develop into oxidative fibres
Cardiac Muscle
Consist of striated cells like skeletal muscle
Instead of a motor neuron coming down and choosing a muscle to operate, there are rhythmic depolarisations happening which trigger action potentials without input from nervous system
How cardiac muscle resists fatigue
Lots of mitochondria in its muscle cells
Intercalated discs
Direct electrical coupling between cells - not associated with brain signal and has its own operation
How does the heart contract
Action potential generated by a cell in one part of heart spreads and whole heart contract
Smooth muscle
Found mainly in walls of hollow organs, contractions are relatively slow and may be initiated by the muscles
Is smooth muscle striated
Lack striations due to a different layout of actin myosin filaments
How do smooth muscles contract
Stimulation from neurons (brain down) or by electrical coupling like cardiac muscle
How do flight muscles work
Capable of independent rhythmic contraction - wings can beat faster than action potentials arriving from CNS.
Barrier to locomotion
Overcome friction and gravity
Locomotion
Active travel from place to place
Swimming (4 points)
- Overcoming gravity not a problem
- Overcoming friction is the major problem (streamlined shape to help overcome)
- Water is denser and more viscous than air
- Insects and vertebrates often use legs as oars to pish against the water
Locomotion on land (4 points)
- Walking, running, hopping crawling require animals to support themself and move against gravity
- Air poses little resistance at moderate speeds
- Land animals expend energy to propel and keep upright
- Thus, powerful muscles and a strong skeleton are more important than a streamlined shape
Balance when walking
Have 3 feet on ground at one time for cat dog or horse
Balance when running
All four feet may be off the ground but momentum keeps the body upright
Balance/energy when crawling
Much of body in contact with the ground therefore requires lots of energy to overcome friction
What does flight require
Wings need to develop enough lift to overcome the downward force of gravity
How have birds adapted to flight
Low body mass, no bladder or teeth, streamlined shape, hollow but strong bones
What does energetic cost of locomotion depend on
Mode of locomotion, size of animal, and enivroment
Do larger or smaller animals travel more efficiently
Larger animals are more effecient than smaller animals specialised for the same mode of transport.
Lowest locomotion type for energy expended per meter
Animals specialized for swimming expend less energy per meter travelled than equivalently sized animals specialized for flying or running
Highest energy consumption per minute
flying animals use more energy than swimming or running animals with the same body mass
