1. THE MUSCULAR SYSTEM What do you already know about muscle tissue?
What is the definition of an organ?

2. Types of muscle tissue
Skeletal muscle
Cardiac muscle
Smooth muscle

3. Functions
Producing body movements by changing chemical energy into mechanical energy
Stabilizing body positions
Generating heat
Moving substances
Within the body

4. Skeletal muscle anatomy
Connective tissue around muscle (epimysium)
Extends to form tendon (dense regular connective tissue) – connects muscle to periosteum of bone

5. Nerves and blood vessels
Muscles: bundles of fascicles (group of fibers – cells) surrounded by perimysium
Nerves and blood vessels
At least 1 capillary per muscle fiber

6. 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

7. 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!

11. Review: Sarcolemma Sarcoplasm Sarcoplasmic reticulum Myofibrils
Don’t write
Review:
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Myofibrils
filaments

12. HOW A MUSCLE CONTRACTS

13. 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

15. 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

16. Sliding filament mechanism

17. Sliding filament mechanism
Lengths of filaments do not change
Sarcomere shortens
Causes shortening of muscle fiber and muscle

18. 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

19. Muscle physiology Muscles tug on tendons which pull on bones
One bone is pulled towards another
Insertion towards origin
Most cross a joint

20. Muscle groups Prime mover and antagonist Opposite actions Switch roles
Opposite sides of bone/joint

21. 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.

22. Muscle contraction Muscle fibers: all-or-none
Strength of muscle contraction: depends on # of contracting fibers
Affects energy usage

23. 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

24. Muscle fatigue
no contraction even with stimulation - occurs from oxygen debt (lactic acid builds up and ATP runs low)

25. Types of muscle contractions
Isotonic: with movement
Isometric: muscle against immovable (or almost) object

26. Effect of exercise
Aerobic (endurance): results in muscles with resistance to fatigue.
Resistance (isometric) training: enlarged muscles

27. 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.

28. The strength of a muscle contraction depends on what?
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

29. example 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

30. THE POINT
The more oxygen your body can take in and use determines your endurance

31. Why are some people better at endurance activities?
DON’T WRITE
Why are some people better at endurance activities?
Why are some people FAST?
Is it genetic? Is it training?

32. 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

33. muscle fibers in muscles
Muscle are a combo of different fibers
Proportion of fibers is individual