locomotion - division of physical & biological sciencesbio.classes.ucsc.edu/bio131/thometz...
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Locomotion
Organization of muscles into musculoskeletal
systems allows the of translation cellular
contraction into animal locomotion.
Musculoskeletal system interacts with the
nervous system to control position and
movement of appendages.
Invertebrates
Most worm-like inverts crawl using
overlapping layers of muscle fibers.
Hydrostatic skeleton:
◦ Simple muscles work in combination with
fluid-filled internal chamber.
Earthworms
Locomotor striated muscles organized
into circular longitudinal layers.
Segmented = more control
◦ Peristaltic waves of contraction
Squid
One of fastest
aquatic invertebrates
Circular muscle that
surrounds the mantle
is composed of 3
layers
Squid
Jet propulsion:
◦ Water enters mantle
◦ Mantle contracts – ejected thru siphon
◦ Creates flume of water, pushing the squid forward
Fish
2 main types of muscle fibers:
White muscle:
◦ glycolytic fiber type, responsible for high
intensity, burst swimming
Red Muscle:
◦ oxidative fiber type, supports slow steady
state cruising activity.
Fish
White Muscle =
◦ 85% of muscle
◦ 60% of body mass
Red Muscle =
◦ Along Lateral Line
◦ Base of Fins
Fish
Myotome:
◦ Blocks of parallel white muscle fibers
connected by thin layers of connective tissue.
Fish
Each myotome connected to posterior
region by tendons.
Skin acts as sheath that connects different
myotomes:
◦ Integrates force of many contractile units
Contraction of a myotome generates a force
that is transmitted to the next myotome.
Muscle Contraction
Oxidative (red) & glycolytic (white)
muscles differ in contractile properties
and produce different types of movement.
Muscle Contraction
Fish:
◦ Red muscle = slow swimming
◦ White muscle = higher velocities
Pattern of sequential activation of muscle contraction = recruitment
Determined by motor neurons, under control of the CNS
Tetrapods
Build individual muscles using
combinations of fiber types.
Muscle fiber types are used in different
combinations to perform many distinct
styles of movement.
Limb Movements
Flexion: when a limb bends at a joint
Extension: limb straightens
Induced in response to the contraction of
antagonistic muscles.
Limb Movement
Antagonistic muscles:
◦ muscles which work in opposition
Locomotor Module:
◦ all of the muscles responsible for a type of
movement.
Fiber Types
3 Main Types:
◦ Different species have different types with
different mechanical properties matched to
their biochemistry and morphology.
1. Slow Oxidative (SO)
2. Fast Oxidative Glycolytic (FOG)
3. Fast Glycolytic (FG)
Fiber Types
Muscle Description Metabolic
Features
Slow Oxidative
(SO)
Red Muscles
Slow Twitch
Endurance Muscles
Marathoners
Fast Oxidative
Glycolytic
(FOG)
White – Pink
Mixed
Oxidative based
metab.
Fatigue Resistant
Fast Glycolytic
(FG)
White
Fast Twitch
Fatigue Sensitive
Quick Response
Muscle Description Metabolic
Features
Slow Oxidative
(SO)
Red Muscles
Slow Twitch
Endurance Muscles
Marathoners
Fast Oxidative
Glycolytic
(FOG)
White – Pink
Mixed
Oxidative based
metabolism
Fatigue Resistant
Fast Glycolytic
(FG)
White
Fast Twitch
Fatigue Sensitive
Quick Response
Fiber Types
Animal %SO %FOG %FG
Sea Otter 56 2 42
Dolphin 43 10 47
Sea Lion 44 18 39
Narwhal 87 ? 13
Energy Metabolism & Muscle Types
Muscle activity demands a great deal of
energy, mainly in the form of ATP.
Locomotor activity is supported by some
combination of anaerobic glycolysis and
mitochondrial aerobic metabolism.
Energy Metabolism & Muscle Types
These two pathways differ in 5 main respects that determine how they support muscle activity:
1. Metabolic Efficiency
2. Rate of ATP Production
3. Dependence on Oxygen
4. Fuel Diversity
5. Range of Mobilization
Metabolic Efficiency
Anaerobic
2 ATP / Glucose
Used during fast /
explosive movements
Aerobic
36 ATP / Glucose
Used during
endurance events
Used during rest and
recovery periods
Rate of ATP Production
Anaerobic
Less Efficient
Much Faster
Runs out of fuel fast
Fatigues
Aerobic
Efficient
Slower
Sustainable
Dependence on Oxygen
Anaerobic
Only option when no
oxygen is present
Aerobic
Needs oxygen
During high intensity activity, oxygen cannot be
delivered to muscles fast enough to meet ATP
demands by oxidative phosphorylation and tissues
become functionally hypoxic.
Fuel Diversity
Anaerobic
Glycolysis relies
exclusively on
carbohydrates
Aerobic
Able to utilize:
◦ carbohydrates
◦ lipids (fatty acids)
◦ proteins (amino acids)
Rate of Mobilization
Muscles possess low levels of fuels that can be oxidized immediately (glucose, fatty acids, glycerol, free amino acids).
These fuels are consumed rapidly, so animals must be able to mobilize stored fuels to sustain muscle activity.
Glycogen stores mobilized much faster than lipid stores
Mitochondrial Content
Mitochondria are the site of oxidative
phosphorylation.
Mitochondrial content is an important
determinant of aerobic capacity.
Mitochondrial Content
Mitochondrial content varies widely
among muscle types and species.
◦ High [Mitochondria] = slow twitch oxidative
◦ Lower [Mitochondria] = fast twitch glycolytic
Fiber Types
Slow Oxidative (SO):
◦ Dense with capillaries
◦ Rich in mitochondria and myoglobin
Fast Oxidative Glycolytic (FOG):
◦ Less dense in mitrochondria and myoglobin
Fast Glycolytic (FG):
◦ Least dense in mitochondria and myoglobin
Muscle Recovery
High intensity activity is fueled by
intramuscular stores of glycogen.
As fast twitch muscles undergo glycolysis,
lactate is produced.
Muscles become exhausted from a
combination of energetic shortfalls, ion
disturbances, and PH imbalance.
Muscle Recovery
Muscles must:
◦ Replenish energy stores
(glycogen, ATP, PCR)
◦ Reestablish ion gradients
(Ca2+ stores and pH)
◦ Remove lactate.
Lactate Removal
1. Used in muscle to rebuild glycogen stores.
1. Blood-born lactate can be oxidized by
other aerobic tissues (eg. Heart)
2. Export lactate to be processed elsewhere.
Cori Cycle
Muscle Recovery
Oxygen consumption increase with increasing activity.
Oxygen stores must be replenished.
Muscles must:
◦ Resynthesize ATP, PCR, and glycogen
◦ Reestablish ion gradients
◦ Repair damaged muscles
Restoring Oxygen Levels
Energy for these processes is provided by
mitochondrial oxidative phosphorylation.
Recovering animals often show elevated
rates of oxygen consumption long after
exercise has ceased = oxygen debt.
Muscles & Locomotion
Metabolic processes must be precisely
coordinated to ensure that ATP
synthesis matches ATP demand.
Hummingbirds
Morning/ first flight - oxidizes fatty acids.
◦ After first nectar it switches to carbohydrate utilization and lipid storage.
Actively feeding - dietary carbohydrates
◦ Stores extra surcose as glycogen and lipid.
Rest - relies on stores.
◦ Also becomes hypometabolic – lowers body temp to reduce MR.
Salmon
Early Stage of Migration:
◦ large fat stores
Mid Migration:
◦ begin breaking down proteins:
muscles and intestinal tract
Late in migration:
◦ glycogen and glucose support
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