1. Physiology of Muscles The Sliding Filament Theory

2. The Neuromuscular System
Linkage between the _______________system and the _______________ system (nerve impulses from the brain or spinal cord).
Motor Unit
Motor Unit =
Motor Units range from small (eye movements) to large (quadriceps of leg).
Muscle Twitch
A single nervous impulse and the resulting contraction.
Nerves transmit impulses in “waves” that ensure smooth movements.

3. Neuromuscular Joint
Junction point between the nervous and muscular systems.
A chemical neurotransmitter is released (Ach - acetylcholine)
Detected by receptors on surface of muscle fibre.
Results in muscle contraction

4. The “All-or-None” Principle
When a motor unit is stimulated to contract, it will do so to it’s fullest potential (maximum)
Whether a motor unit consists of 10 muscle fibres or 800, either __________________________________________________________________________

5. Outside Anatomy of Skeletal Muscle
Skeletal muscle makes up a substantial portion of human body weight
The _________________ (outer connective tissue) binds groups of muscle fibres called __________________ together which are then bound by the larger/stronger ______________
The ___________________ envelopes the entire muscle, it changes its properties as it becomes one with the tendon
Remember the ______________________ of the long bone?
This is where the tendon of the muscle attaches to the bone
Muscle is attached to bone at two locations:
Origin=
Insertion=

6. Perimysium
Endomysium
Epimysium

7. Inside Anatomy of Skeletal Muscle
The endomysium (sheath of connective tissue) surrounds each individual muscle fibre
Beneath the endomysium is the sarcolemma a plasma membrane containing the muscle cell’s cytoplasm (sarcoplasm)
The endomysium is surrounded by a rich blood supply and, therefore, a good system for O2 and CO2 removal
Nerves also supply the muscle
Thread like structures, myofibrils, run the length of the muscle
Within the myofibril are thin (Actin) and thick (Myosin) filaments
Actin and Myosin are contained within Sarcomeres (compartments)

9. Myofibril Myosin – thick filaments
Actin – thin filaments, contains the proteins:
Troponin –
Tropomyosin –
Together, actin and myosin, have a swivel-locking mechanism
This is the “Sliding Filament Theory”

10. Myofibril

11. Sliding Filament Theory
Myosin head will not attach to actin unless ____________ is released by the sarcoplasmic reticulum (SR)
_______ (acetylcholine) initiates this
_______________ swivels, allowing the binding sites on ___________ filament (_____________) to be exposed
During contraction, protein filaments interact at molecular level causing them to slide across each other (the sarcomere shortens)
REST
the cross-bridges extend toward _____________
The _____________and ______________ are now in a coupled position.
The level of _______________ concentration is low

13. Sliding Filament Theory
STIMULATION:
myosin ___________________ form a type of bond with selected sites on the actin filament
Acto-myosin formation takes place
There is an immediate increase of intracellular _______
This is brought about by the arrival of the action potential at the transverse tubules, which causes Ca2+ to be released by the SR
The inhibitory action of _______________ that prevents actin-mysoin interaction is released when Ca2+ ions bind rapidly with troponin in the actin filament.
Now the muscle is “turned on”

15. Sliding Filament Theory
CONTRACTION
Cross-bridges _________________________
The muscle shortens and the __________ slides over the _______________
Tension develops
The _________ is broken down to ______ plus _____plus energy
Contraction will continue as long as ___________ions remain at a level that inhibits the troponin-tropomyosin system

17. Sliding Filament Theory
RELAXATION
nerve stimulus to the muscle is removed, _________ions move back into the SR
The retrieval of __________from the troponin-tropomyosin proteins “____________” the active sites on the actin filaments
This deactivation accomplishes two things:
It prevents any mechanical link between the myosin cross-bridges and the actin filaments
It reduces the activity of myosin ATPase so there is no more splitting. Muscle now returns to resting state.

19. THE ROLE OF ADENOSINE TRI-PHOSPHATE (ATP)
ATP is a chemical compound stored in muscles, which contains three phosphates attached by high-energy bonds to adenosine.
When the myosin heads on the myosin filaments attach themselves to binding sites on the actin, ATP is broken down and the energy released causes the myosin to pull on the actin.
As the work of the muscle increases, more and more ATP is used up.
ATP  ___________________________

23. For more help on the sliding filament theory