Biol 241 - Locomotion

What does understanding max metabolic rates allow us to make predictions on?

Reproduction, distribution, range, migration, other constraints on survival

What are physiological limitations on MRmax and MR sustained?

Metabolic (cellular) pools of ATP + phosphocreatine + PCr + ADP _> C + ATP

Recovery metabolism

Repaying oxygen debt as aerobic respiration regenerates the ATP + PCr pools

Muscles use ___ to contract, generating what?

ATP, force

The force generated by any muscle will increase as you increase… (2 things)

the number of muscle cells in a muscle

the length of the muscle

The force generated by any muscle will decrease with…

the speed of contraction

A muscle is a bundle of what?

muscle fibres (muscle cells)

During muscle growth, what occurs?

hundreds of myoplasts fuse to form a long, multi-nucleate cell

Muscle fibres are filled with bundles of what?

myofibrils: proteins that are as long as cell length

What do myofibrils consist of?

alternating thick and thin filaments

The myofibrils thick and thin filaments are arranged along the length of the myofibril in what?

repeating sarcomeres (the functional unit of muscle)

Myofibrils are what?

striated: marked with long, thin parallel streaks.

The muscle is denser where?

where the thick and thin filaments overlap = dark bonds

The muscle is less dense where?

where the filaments do not overlap = light bonds

What are thin filaments?

two linear polymers of actin proteins wound around each other

What do tropomyosin proteins wrap around?

the thin filament

What proteins associate with tropomyosin along the length of the filament?

Troponin

What are thick filaments?

Bundles of myosin

each myosin protein is a dimer of what?

dimer of two polypeptide coiled around each other with a globular “head” at one end and a long helical “tail”

dozens of myosin homodimers are arranged into the thick filaments with the head groups sticking which way?

Out

Sarcomeres have a ___ at each end

Z-line

What extends out from each z-line towards the middle of the sarcomere?

actin (thin) filaments

Sarcomeres have a ___in the middle

M-line

what extends out from each M-line towards each end of the sarcomere?

Myosin (thick) filaments

What is a crossbridge?

the interaction between a actin proteins and a myosin head group

each actin protein has a….

myosin binding site and a ATP binding site

where multiple myosin (thick) and actin (thin) filaments overlap what can form?

multiple crossbridges

What increases with number of cross bridges and interaction between thick and thin filaments?

force

What is the sliding filament model?

muscles contract when the myosin filaments pull the opposing actin filaments toward each other

what is sarcoplasmic reticulum

specialized endoplasmic reticulum that surrounds muscle myofibrils

when a signal is received from a motor neuron, what is the first step of activating muscle contraction?

calcium facilitates diffusion, proteins open

when a signal is received from a motor neuron, what is the second step of activating muscle contraction?

Ca 2+ diffuses down its [gradient] back into cytosol

when Ca2+ enters the cytosol, what is the first step of excitation-contraction coupling?

Ca2+ binds the troponin on the thin filaments

when Ca2+ enters the cytosol, what is the second step of excitation-contraction coupling?

Ca2+ binding causes troponin to change shape which causes tropomyosin to shift

when Ca2+ enters the cytosol, what is the third step of excitation-contraction coupling?

tropomyosin covers myosin binding site when it moves, it exposes these binding sites allowing a cross-bridge to form

The crossbridge cycle - what occurs in the first step here?

ATP is used so the myosin pulls on actin filaments

each Z-line will move toward the M-line

Muscle contraction - what do myosin head groups repeat during muscle contraction?

each myosin head group repeats the cross-bridge cycle many times during muscle contraction

muscle contraction - what do myosin filaments work in unison to do?

each myosin filament (containing dozens of myosin molecules) work in unison to pull on six surrounding actin filaments at each end

muscle contaction - what occurs when the thousands of sarcomeres within each myofibril and muscle fiber shorten?

the muscle contracts

the force generated by muscles increases when ____

when the number of cross bridges formed in sarcomere increases

the force generated by any muscle will increase as you increase what?

increase the number of muscle cells in the tissue, more muscle cells = more sarcomere

and

increase the length of the muscle tissue, longer muscle cells = more sarcomeres

the force generated by any muscle will decrease with…

speed of contraction, rapid contraction decreases number of crossbridges

muscle relaxation - when the signal from the motor neuron stops, what is the first step?

the facilitated Ca2+channels in the SR close, Ca2+ can’t leave SR

SR = sarcoplasmic reticulum

muscle relaxation - when the signal from the motor neuron stops, what is the second step?

the Ca2+ -ATPase pumps Ca2+ from cytosol

muscle relaxation - when the signal from the motor neuron stops, what is the third step?

Troponin releases Ca2+, causing tropomyosin to change back into its original shape and block the myosin binding sites

muscle relaxation - when the signal from the motor neuron stops, what is the fourth step?

unable to bind myosin, the actin filaments slide back, lengthening the sarcomeres

Forces acting on a runner

gravity, thrust, muscle action, only a bit of drag

what is mass-specific metabolic rate?

energy (volume of oxygen) required to move 1 unit mass of an organism

What is cost of transport?

the energy required to move 1 unit mass of an organism 1 unit distance

what are the forces acting on a swimmer?

thrust, buoyancy, drag

what are viscous forces?

skin friction drag

what are inertial forces?

pressure drag

what are the forces acting on a flier?

gravity, thrust, lift, drag

wings generate lift + thrust to counter gravity and drag