topic 9 - locomotion Flashcards
what happens to skeletal muscle during growth
hundreds of myoblasts fuse to form a long multinucleate cell
each muscle cell runs the entire length of the muscle
what is the cross bridge cycle
ATP binds to myosin causing the cross bridge to release
ATP hydrolysis cocks myosin into position
myosin attaches to actin to form cross bridge
myosin releases ADP and Pi causing working stroke
what happens when the number of cross bridges between actin and myosin in sarcomere increase
more force
what happens when the number of muscle cells in the tissue increases
more force
more muscle cells/fibres = more sarcomeres
what happens when the number of muscle cells in the tissue increases
more force
longer muscle cells/fibres = more sarcomeres
what happens when muscle contracts more slowly
more force
rapid contraction decreases number of cross bridges
what are the physiological limitations on energy production
limit rate of ATP production - critical component to make cross bridges produce force (can’t sprint long distance - only so much ATP we can make so quickly)
delivery of O2 to muscles (takes time)
what is the difference between max and sustained metabolic rates
ability to sustain high level of metabolic rate declines to a level of sustained
amount of energy you can generate to put into an activity reaches an asymptote
focus on the max possible metabolic rate to achieve a certain locomotion
what is the order of contributions to metabolism
pools of stored ATP in cells that provide instant energy (used fast)
have PCr (backup pool of ATP)
- PCr + ADP –> Cr + ATP
glycolysis (starts quickly making ATP)
oxidative phosphorylation (keeps making ATP (starts later, lasts longer)
what is the relationship between MR max and MR sus for long activities
MR max = MR sus
what is recovery metabolism
replenish cellular pools of ATP/PCr and remove lactic acid
what happens at the beginning of exercise
use cellular pools of ATP/PCr and produce lactic acid (anaerobic) creating a “debt”
does active MR max scale with mass
yes
small mass = small energy production
small mass = uses more energy per gram compared to larger animal
what is metabolic scope
capacity for locomotion
- relatively the same for endo and ectotherms
MRmax/RMR or MRsus/RMR
what is the difference in metabolic scope and rate between ecto and endotherms
scope = roughly the same across vertebrates (vertical difference in slope between MRmax or sus and RMR)
rate = overall lower in ectotherms
what does mass specific metabolic rate measure
energy required to move 1 unit mass of an organism over 1 unit of time
kJ/kgh
what is the cost of transport
energy required to move 1 unit mass of an organism 1 unit distance
mass specific MR and divide by velocity (km/h)
kJ/kgkm
what are the factors affecting any type of locomotion
inertia
momentum
drag
what is inertia
tendency of a mass to resist a change in motion
increases with mass
what is momentum
tendency of a moving mass to sustain velocity
increases with mass
what is drag
force generated in the opposite direction of an animals mvmt be the density / viscosity of the medium
increases with mass/velocity
what is the effect of size on drag
large organisms spend less energy overcoming drag than small organisms
small have less SA overall
as velocity increases, more energy has to go to oevrcoming drag
what are the forces acting on a runner
gravity - largest factor in activity budget
thrust - energy needed for forward motion, lots of energy from each step is transferred to growth
drag - force generated in opposition to thrust (negligible in air)
muscle action - constantly supporting mass
how does mass affect a runner
cost of starting = higher for heavier runner
mouse can speed up faster - can overcome inertia better
larger organism can reach higher speed
how does mass affect mass specific MR
higher in smaller
large organisms have longer muscles
small organisms have shorter muscles
more expensive to contract short muscles (less force generated)
how does velocity affect runners
As velocity increases, limbs move faster
- muscles contract faster
- more energy required
small have to work harder to run fast
- limbs / muscles are shorter
- stride is shorter so more contact with the ground (need to overcome gravity each time)
as velocity increases, more energy can go towards generateing forward motion
- momentum increases
- less contact with ground = less energy loss
how does MS MR and CoT change with velocity increase
msMRmax increases linearly for both small and large
small organisms have greater msMR max than larger organisms
COT decreases linearly for both runners because inertia, momentum, and contact with ground decreases
smaller organisms have a steeper increase in MRmax with velocity and higher overall
how to convert msMRmax to CoT
CoT at a velocity as the slope from the origin to the point of an msMR by velocity plot
velocity stays the same when converting (x value)
divide y/x to get CoT value (divide msMR by velocity at that point)
what is the effect of mass on CoT
negative scaling relationship
larger mass = lower CoT for running
what are the forces acting on a swimmer
gravity - negligible factor in activity budget
- big thing that differentiates flying, swimming, and running
thrust - energy needed for forward motion
- body shape is often adapted to minimise drag
buoyancy - generate neutral buoyancy (swim bladders)
drag - biggest cost to a swimmer, density / viscosity of water is greater than air
what are viscous forces
skin friction drag (water has high cohesive properties)
higher in small swimmers (single celled organisms)
high SA to volume ratio means that a lot of water sticks to surface and being small means less mass and therefore less ability to generate force to overcome friction
what are inertial forces
pressure drag
higher in larger swimmers (fish+)
larger organisms (higher volume) are going to create more turbulence which creates pressures that slow it down
what is the optimal d/l ratio to minimise drag
0.25
more SA to volume = more skin friction drag
larger volume = more pressure drag
how does mass affect swimmers
larger swimmers experience less skin friction drag (lower SA to volume ratio)
small swimmers must work harder to move faster (shorter muscles)
how does velocity affect swimmers
as velocity increases, muscles contract faster (muscles contract faster, more energy required)
as velocity increases, pressure drag increases (energy expense rises sharply with velocity to fight pressure drag)
what is the effect of mass on CoT
larger = lower cost
benefit from larger muscles, ability to generate more force, and lower skin friction drag
what is the relationship between velocity and MS MRmax in swimmers
curve (U shape)
CoT at lowest point at an intermediate velocity
why aren’t very small invertebrates shaped like fish
inertial forces are negligible
never go fast enough to generate pressure drag
different shapes help them catch currents
what are the forces acting on a flyer
Gravity - more important at low velocities - effect between runners and fliers
Thrust - energy needed for forward motion
Drag - more important at high velocities - increases as speed increases
Lift - force generated that counters gravity that increases with velocity
how does mass affect fliers overcoming gravity
Larger fliers fight harder (greater mass)
Very small fliers (insects) affected much less (very low mass)
Mass is very important for fliers
(runway for canada geese vs insects being able to fly immediately)
how does mass affect fliers overcoming drag
Very small fliers “swim” through air due to higher relative density / viscosity
Larger fliers must work harder to overcome drag
Skin friction factors come into play
how does velocity affect fliers
As velocity increases, limbs move faster
Muscles contract faster, more energy required
very small fliers have to work hard to move fast - continually beat wings to stay aloft
how does velocity affect lift and drag
as velocity increases, both lift and drag increase
energy expense to fight gravity decreases but energy expense to fight drag increases
drag becomes a tradeoff with gravity
what is induced power vs parasite power
induced power = energy required to counter gravity
(decreases at high velocity)
parasite power = energy required to counter drag
(increases at high velocity)
how to find optimum velocity to fly
where induced and parasite power slopes cross
what are the msMRmax and CoT curves in fliers
CoT minimsed at intermediate velocities
smaller flier = more energy overall than a larger flier
what is the ranking of CoT in different locomotions
runner = higher CoT
flyer
swimmer = lower CoT
why is CoT different in different locomotions
due to relative importance of gravity
negligible in swimmers (buoyancy overcomes)
fliers generate lift to overcome gravity (intermediate effect)
runners fight gravity with every step
