the muscular system
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THE MUSCULAR SYSTEM. What do you already know about muscle tissue? What is the definition of an organ?. Types of muscle tissue. Skeletal muscle Cardiac muscle Smooth muscle. Functions. Producing body movements by changing chemical energy into mechanical energy Stabilizing body positions

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the muscular system


What do you already know about muscle tissue?

What is the definition of an organ?

types of muscle tissue
Types of muscle tissue
  • Skeletal muscle
  • Cardiac muscle
  • Smooth muscle
  • Producing body movements by changing chemical energy into mechanical energy
  • Stabilizing body positions
  • Generating heat
  • Moving substances

Within the body

skeletal muscle anatomy
Skeletal muscle anatomy
  • Connective tissue around muscle (epimysium)
    • Extends to form tendon (dense regular connective tissue) – connects muscle to periosteum of bone
Muscles: bundles of fascicles (group of fibers – cells) surrounded by perimysium
  • Nerves and blood vessels
    • At least 1 capillary per muscle fiber
Myofibrils= contractile organelles  stripes
  • Sarcoplasmic reticulum - encircles myofibrils= similar to smooth ER; function = stores calcium
  • Filaments (thin and thick)– inside myofibrils; don’t extend length of fiber; contained in sarcomeres
anatomy of muscle fiber
Anatomy of muscle fiber
  • No mitosis
  • Growth: hypertrophy due to hormones (testosterone, HGH)
  • Sarcolemma = cell membrane
  • Sarcoplasm = cytoplasm (glycogen!!)
  • Myoglobin – a protein = binds with/release O2 for the mitochondria
  • Mitochondria = many!
don t write
Don’t write
  • Review:
    • Sarcolemma
    • Sarcoplasm
    • Sarcoplasmic reticulum
    • Myofibrils
    • filaments
how a muscle contracts

A neuron connects to a muscle fiber [called the neuromuscular junction (NMJ)]
  • Arrival of nerve impulse causes release of acetylcholine (ACh: a neurotransmitter – a chemical).
  • ACh diffuses to receptors on muscular membrane (sarcolemma), opening a Na+ ion channel, causing Na+ to enter the muscle fiber
muscle contraction cont
Muscle contraction cont
  • Causes muscle action potential due to change in membrane potential (b/c of addition of Na+ )
  • Sarcoplasmic reticulum releases stored Ca+2 into sarcoplasm
  • Causes muscle contraction (sliding filament mechanism):
    • Unblocks actin (thin) so myosin (thick) heads can bind to them
    • Filaments slide past one another, shortening the muscle
sliding filament mechanism
Sliding filament mechanism
  • Lengths of filaments do not change
  • Sarcomere shortens
  • Causes shortening of muscle fiber and muscle
plants drugs effect nmj
Plants/drugs effect NMJ
  • Botulinum toxin from bacterium Clostridium botulinum blocks exocytosis of ACh
  • Curare – plant derivative – used on arrow/blowgun darts. Binds to/blocks ACh receptors
muscle physiology
Muscle physiology
  • Muscles tug on tendons which pull on bones
  • One bone is pulled towards another
  • Insertion towards origin
  • Most cross a joint
muscle groups
Muscle groups
  • Prime mover and antagonist
  • Opposite actions
  • Switch roles
  • Opposite sides of bone/joint
lever systems
Lever systems
  • Most of the bones of the limbs (arms & legs) act as levers. These levers are powered by muscles.
  • A lever is a rigid rod able to rotate about a fixed point known as a fulcrum, formed by the joint. Any force applied to the lever is called the effort.
  • A force that resists the motion of the lever, such as the downward force exerted by a weight on the bar, is called the load or the resistance.
  • The contraction of the muscles is the effort and the part of the body concerned is known as the resistance or load.
  • Bones of the body act as levers (a mechanical device) which create a mechanical advantage of strength or speed.
muscle contraction
Muscle contraction
  • Muscle fibers: all-or-none
  • Strength of muscle contraction: depends on # of contracting fibers
  • Affects energy usage
providing energy
Providing energy
  • ATP broken down during contraction
  • Store little ATP, must produce it
  • 3 ways:
    • Aerobic respiration: slow, requires O2, lots ATP
    • Anaerobic glycolysis and lactic acid formation: faster, no O2 needed, less ATP
    • Creatine phosphate and ADP: CP not found in other cells, very fast, doesn’t last
muscle fatigue
Muscle fatigue
  • no contraction even with stimulation - occurs from oxygen debt (lactic acid builds up and ATP runs low)
types of muscle contractions
Types of muscle contractions
  • Isotonic: with movement
  • Isometric: muscle against immovable (or almost) object
effect of exercise
Effect of exercise
  • Aerobic (endurance): results in muscles with resistance to fatigue.
  • Resistance (isometric) training: enlarged muscles
in review don t write
In review……… (don’t write)
  • Lifting weights is an example of resistance or endurance training?
  • The reaction of creatine phosphate and ADP generates ATP quickly or slowly?
  • The ability of your body to use oxygen to produce ATP is _____ respiration.
  • True or False: The strength of a muscle contraction is determined by the amount of muscle fibers that are contracting.
don t write1
Don’t write
  • The strength of a muscle contraction depends on what?
  • What is the relationship between the strength of a muscle contraction and energy usage?
  • Muscle fatigue is due to ____ debt
  • Running a 100 yd dash in 12 seconds requires 6L of oxygen.
  • But the max amount that could be delivered and used by your muscles (VO2 max) would be 1.2 L
  • Oxygen debt?
  • = 4.8L
the point
  • The more oxygen your body can take in and use determines your endurance
don t write2
Why are some people better at endurance activities?

Why are some people FAST?

Is it genetic? Is it training?

types of muscle fibers
Types of muscle fibers
  • 1. Slow oxidative fibers
    • Little power (small in diameter); fatigue resistant; many mitochondria. Adapted for maintaining posture & endurance activities
  • 2. Fast oxidative-glycolytic fibers
    • Intermediate in diameter, faster than #1 but briefer in duration. Adapted for: walking/sprinting
  • 3. Fast glycolytic fibers
    • Large diameter (contract strongly/quickly); tire quickly; large amount lactic acid build up
    • Short, rapid, intense movement
    • Adapted for intense anaerobic movements of short duration: weight lifting/throwing a ball
muscle fibers in muscles
muscle fibers in muscles
  • Muscle are a combo of different fibers
  • Proportion of fibers is individual