Lecture #13: Muscles Flashcards
Hydrostatic
Fluid-filled space (ex: earthworm)
Endoskeleton
Bones, living (grows w/ body)
Osteoblasts
bone building cells (B)
osteoclasts
bone destroying
Exoskeleton
Insect, crab (skeleton is outside body, helps prevent water loss + provides protection
- needs to shed (non-living)
Flexim
move toward body
Extension
move away from body
Abduction
to move away from midline
Aduction
to move toward midline (D)
Tendon
connects muscle to bone
Ligament
connect bone to bone
Cartilage
end of long bone
- disks for cushion at joints
How to change intensity (force) of contractions?
- change the number of twitches/sec for individual fiber
- if second twitch occurs before first twitch relaxes, you increase the force - change the number of fibers that twitch
- doesn’t change the intensity of a single twitch
- single twitch is all or none
Tetanus
constant contractions
- greater max force
Smooth muscle
involuntary, no striations (stripes)
- slow, low intensity contractions (wave)
Cardiac muscle
involuntary, striated, light fatigue
Skeletal muscle
voluntary, striated
Oxidative fibers
fatigue slowly, less forceful, lots of mitochondria and myoglobin (reddish tint)
Glycolytic
fast response, forceful contractions, fatigue more quickly
- less mitochondria and myoglobin (paler appearance)
Postural muscles of back
Almost all oxidative fibers
Biceps
mix of oxidative and glycolytic fibers
- fatigue very fast (glycolytic fibers)
Breakdown of muscle?
Whole muscle
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Bundles of muscle fiber
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Individual muscle fiber (individual multinucleated cell (very long))
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Myobril - bundle of myofilaments
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Myofilaments - actin (thin) + myosin (thick)
Motor endplate
motor neuron connected to muscle cells
How are myosin and actin in relaxed state?
myosin and actin are long
How are myosin and actin in contracted state?
Myosin and actic remain the same length but have more overlap, appearing shorter
- sacromere is shorter
Muscle contraction
sources of energy - ATP, creatine phosphate, glucose, glycogen (1st - muscle, 2nd - liver), (fat)
steps to muscle contraction?
- Action potential travels down a motor neuron
- Neurotransmitter (acetycholine) crosses the synaptic gap from the motor neuron toward the muscle cell
- the muscle cell depolarizes, creating an action potential within the muscle cell
- the action potential within the muscle cell causes Ca++ (calcium) to be released from the saracoplasmic reticulum
- Ca++ binds to the actin-troponin-tropomyosin complex, allowing myosin to form cross-bridges to actin
- Using energy from the conversion of ATP to ADP, myosin binds to actin in a high energy configuration
- Myosin relaxes to its low-energy configuration, sliding the actin filament past it, shortening the sarcomere
- Myosin reattaches to actin further along the actin filament, and the process starts over (steps 6 and 7)
- When nervous stimulation stops, muscle contraction stops, and calcium is pumped back into saracoplasmic reticululm
How much ATP does 1 molecule of glucose with oxygen provide (aerobic)?
34 ATP
How much ATP does 1 molecule of glucose WITHOUT oxygen provide (anaerobic)?
2 ATP (less than aerobic)
How to sustain contractions?
Need oxygen to generate ATP from glucose, myoglobin, and mitochondria
Athletic training
Aerobic (stamina)
- make fibers more oxidative-like
- more mitochondria
- more myoglobin
- greater blood supply to muscle
Strength
- thicker muscle fiber (requieres protein for more actin and myosin)
- (little increase in # of muscle fibers)
- more dense bones
