Animal: Lecture 8 Flashcards
Hardened support structures?
Hardened support structures (keep them upright) can be external, internal, or absent.
Hydrostatic skeleton?
Hydrostatic skeleton are fluid filled: fluid held under pressure in a closed body compartment
– E.g., worms, jellyfish, sea anemone
- jellyfish aren’t entirely closed, but they have muscular cells that can close off the gap making it stiff inside.
Endoskeleton?
Hardened internal skeleton
- E.g. sponges, echinoderms (like seastarts), chordates (like humans)
Exoskeleton?
Hardened external skeleton
- E.g. arthropod cuticles and mollusc shells
- Insects, crabs, lobsters, snails.
- The soft part of their bodies is attached to the skeleton that is outside
Peristaltic crawling of earthworms?
Elongation: Longitudinal muscle is relaxed (extended) and the Circular muscle is contracted.
Shortening: Longitudinal muscle contracted and Circular muscle relaxed.
Each segmented piece all gas their own fluid (closed in the cavities).
- Head end is short and middle is long
- Head end is long and middle is short.
- Bristles attach to the ground to continue moving forward.
- They swap positions, creating a wave-like motion
Locomotion with a hydrostatic skeleton?
Antagonistic muscle pairing as they work differently/in contrast to create motion
Can animals with a hydroskeleton jump?
Yes, they have no hard limbs. Jumps by moving fluid around.
How do endo and exo generate movement?
Endoskeletons and exoskeletons generate movement using muscles attached to the hard part of the skeleton (not the surrounding items)
Antagonistic muscles?
Antagonistic muscles generate opposite movements across a
joint
* When one contracts, the other must relax
Human forearm flexion and extension?
Bicep: flexor muscle
Tricep: extensor muscle
- Bicep contracts (flexing), pulling arm bone towards it
- Tricep has to stay relaxed.
- Bicep relaxes
- Tricep contract, opening or extending the arm
THEY ARE ANTAGONISTIC
Grasshopper tibia?
Extensor in the middle stays relaxed, flexor muscle contracts. The leg moves in as a result.
Extensor muscle contracts and the flexor muscle relaxes. The leg moves out as a result.
Vertebrate skeletal muscle is an example of…?
Vertebrate skeletal muscle is an excellent example of hierarchical organization in biological structures
Skeletal muscle is composed of
Muscle fibres (each a multinucleated muscle cell) which are composed of
Myofibrils which are composed of Thin (actin) + thick (myosin) filaments
What is the hierarchical organization of muscles?
- Muscle
- Bundle of muscle fibres
- Single muscle fibre (cells): long tubular cell with many nuclei
- Cells surrounded by plasma membrane
- Myofibril (organelles)
- Sarcomeres (functional units in charge of contraction - shorten length of cell causing contracting)
Myofibrils are compose dof..?
Myofibrils are composed of thin (actin) and thick (myosin) filaments
Actin?
Thin filament
- Two chains of actin molecules
- Have myosin-binding sites
- Connected at the tail end by the Z line
Myosin?
Thick filament
- Multiple myosin molecules with their head exposed.
- A motor protein (ATP ~> movement) they generate movement abdominal creates contraction in the sarcomere
- They look like a bundle
- The myosin are connected at the m-line
Composition of the sarcomere?
A sarcomere is composed of multiple thick and thin filaments bounded by Z lines.
- when contraction occurs - movement of actin filament is toward the m-line.
- Myosin and actin are NOT connected at any point, they just move near or on top of one another at certain times.
Skeletal muscles striated muscle?
Striated evvause they look like a bunch of lines.
- On a photo, the darker parts are where they are connected (darkest at m line and z lines)
Length of thick and thin filaments?
Thin and thick filaments do not change their length; they slide past each other.
- Size and length of thick and thin filaments NEVER changes, only their positions.
Steps of myosin and actin together?
- There is a potential to move muscles because ATP is present. However, myosin head is bent in a bad position (low energy config) meaning it cannot bind to the myosin-binding site.
- Hydolysis of ATP makes ADP and P meaning there is a release of energy from the bonds. The Myosin goes in a high energy configuration and is ready to bind to actin!
- The cross-bridge forms as the myosin attached to the actin.
- Thin filament moves toward the centre of the sarcomere. Movement from front to back pulls actin toward the centre. ADP and P are GONE.
- ATP is re-entered and attaches to the myosin head, and stops the cross bridge.
How does the muscle know when to contract?
Skeletal muscle contraction is initiated by motor neurons
- Results in an increase in free Ca2+ in myofibrils of muscle cells
- Need Ca2+ ad ATP for contraction to happen.
- Ca2+ interacts with thin filament regulatory proteins (tropomyosin
& troponin), exposes myosin binding site, allows myosin binding
Unbound vs. bound Ca2+
Myosin binding sites are blocked when no Ca2+
Myosin binding sites are exposed when Ca2+ is bound
What would happen to a muscle if it
was injected with a drug that degrades tropomyosin?
A. It would contract whenever there is sufficient ATP.
B. It would not be able to contract.
A. It would contract whenever there is sufficient ATP.
Locomotion?
Locomotion is active travel from
place to place
What must happen to move?
To move, an animal must expend energy
to overcome gravity and friction
Environment and opposing force?
The animal’s environment
determines which of these forces
is the dominant force opposing
locomotion
̶ Land and Air: Gravity
̶ Water: Friction
Natural selection - adaptation?
Natural selection favours adaptations
that reduce energy costs of locomotion
* Adaptations are usually anatomical
– E.g., fusiform (tapered at one end- allows efficient gliding) body shape, springy tendons (allows jumping)
* Adaptations can also be behavioural
– E.g., passive descent in diving mammals
Gravity?
Gravity is the dominant force opposing locomotion on land
* Animals that locomote on land require powerful muscles and strong skeletal support to propel themselves and remain upright
Maintaining balance is essential?
When walking, bipedal animals keep one leg on the ground; multi-legged animals keep three legs on the ground
ANT example?
Three legs move, three stay on the ground
Running or hopping?
When running or hopping, all legs can leave the ground; momentum keeps the body upright
Adaptations that are favoured by natural selection can reduce energy expenditure?
- When tendons stretch as the animal lands, they store energy in elastic fibres (allows us to jump using stored potential energy)
- The energy is released to aid the next jump
Gravity in air?
Gravity is the dominant force
opposing locomotion in air
- Wings of flying animals must generate enough lift to overcome gravity’s downward force
- pressure exerted by faster-moving air generating lift and pressure exerted by slower-moving air is below.
Flying animal adaptations?
Flying animals tend to have low body mass – E.g., Birds
* No urinary bladder (birds don’t pee!)
* No teeth (light)
* Hollow air-filled regions in bones (still very strong, just lighter)
A fusiform (tapered) body help reduce drag (AKA friction)
Friction in water?
Friction is the dominant force
opposing locomotion in water
* Most aquatic animals are reasonably buoyant;
i.e., overcoming gravity requires little energy
* But water is a denser and more viscous medium than air; drag (AKA friction) is a problem
* Fusiform body is an adaptation to reduce drag
Skeletons and muscles?
Skeletons and muscles work together to generate movement
Skeletal muscle contraction?
Skeletal muscle contracts when myosin heads change shape to pull actin filaments towards the centre of the sarcomeres.
Ca2+ interactions?
Ca2+ interacts with regulatory proteins to control skeletal muscle contraction
Animal adaptations?
Animals possess adaptations to reduce the energy cost of overcoming gravity and/or friction during locomotion.
