1. Muscle Contraction Energy for Movement
Muscular System
Organization
Muscle Contraction Energy for Movement

2. Functions of the Muscular System
Supports the body
Makes the bones move
Helps maintain constant body temperature
Assists movement in cardiovascular and lymphatic vessels
Helps protect internal organs and stabilize joints

3. Structure of Skeletal Muscle
Each fascicle is a bundle of muscle fibers
Each muscle fiber is a bundle of myofibrils
Whole muscle is a bundle of many fasicles
Each myofibril is made of many sarcomeres
The fascia surrounds the muscle
Each sarcomere is made of actin and myosin fibers

4. Skeletal Muscles Work in Pairs
Muscles contract (shorten) or relax
Muscle contraction pulls on an attached bone
Prime mover = muscle doing the most work
Synergists = muscles assisting prime mover
Antagonist = muscle with action opposite to prime mover
on stationary bone
on bone that moves

5. by direction of muscle fibers by number of attachments
Ways to Name Muscles
by location
by attachment
by direction of muscle fibers
by shape
by number of attachments
by action
by size

6. Structure of a Skeletal Muscle Cell
cytoplasm, contains organelles and myofibrils
plasma membrane
bundle of muscle cells (fibers)
sarcolemma
myofibril
sarcoplasm
Contains actin and myosin filaments for contraction
one myofibril
Skeletal muscle cell (fiber)
contractile unit
one sarcomere
Z line
Z line
extensions of sarcolemma, contact sarcoplasmic reticulum
T tubule
nucleus
Smooth ER, stores calcium
sarcoplasmic
reticulum

7. Applying Your Knowledge
Synergist
Sarcomere
Myofibril
Antagonist
Muscle Fiber
A fascicle is a bundle of ________.
Which one assists the primer mover?
Which one is the contractile unit?

8. Structure of the Sarcomere
Muscle has light and dark bands (striations) corresponding to the placement of myofilaments in the sarcomere.

9. Sliding Filament Theory of Muscle Contraction
Sarcomere shortens when actin filaments slide past myosin filaments and approach one another.

10. Events at the Neuromuscular Junction
Neurotransmitter is released into synaptic cleft between neuron and muscle cell
Neurotransmitter binds to receptors on sarcolemma, impulse spreads down T tubules
Sarcoplasmic reticulum releases calcium to stimulate contraction

11. Events at the Sarcomere
Attached to tropomyosin at regular intervals
Calcium binds to troponin
Arranged over myosin binding sites on actin filaments

12. Events at the Sarcomere
ATPase Enzyme
Energy from ATPADP + P causes myosin heads to form cross-bridges that pull actin filaments toward the center of the sarcomere.

13. Applying Your Knowledge
Troponin
Actin
Tropomyosin
Myosin
Calcium
Which is released by the sarcoplasmic reticulum to stimulate contraction?
Which one has ATPase activity?
Which one binds to calcium?
Which one slides past another fiber to shorten the sarcomere?

14. Whole Muscle Contraction
Strength of Contraction depends on
number of muscle fibers contracting
number of motor units responding
number of muscle fibers within a motor unit

15. Energy for Muscle Contraction
anaerobic
built up in resting muscle
aerobic
anaerobic

16. Slow-and-Fast Twitch Muscle Fibers
Slow twitch
motor units with fewer fibers many mitochondria myoglobin gives dark color
dense capillary beds draw more blood and oxygen
Fast twitch
motor units with many fibers
fewer mitochondria little myoglobin
fewer blood vessels
Motor units with many fibers