Muscular system from Tate & Seely

1. JOEL G. SORIA, PT, MD
Chapter 7 - The Muscular System

3. • Body Movement
• Maintenance of Posture
• Respiration
• Production of Body Heat
• Communication
• Constriction of Organs and Blood
Vessels
• Heart Beat
Functions

4. • CONTRACTILITY: ability of skeletal muscle to
shorten with force.
• EXCITABILITY: capacity of skeletal muscle to
respond to a stimulus.
• EXTENSIBILITY: skeletal muscle can be stretched
to their normal resting length and beyond to a
limited degree.
• ELASTICITY: ability of skeletal muscle muscles to
recoil to their original resting length after they
have been stretched.
Functional Characteristics

5. Sarcomere
Sarcoplasmic
Reticulum
Transverse Tubule
Capillaries
Nuclei
Bone
Tendon
Skeletal muscle
Epimysium
(fascia)
Fasciculi
Endomysium
Muscle fiber
Mitochondr
Myofibrils
Actin
Myosin
Sarcolema

7. Sarcomere – Basic structural and functional unit of
skeletal muscle.
– Each sarcomere extends from one Z-disk to
another Z-disk
Z-Disk – a network of protein fibers forming an
attachment site for actin myofilaments

8. Sarcomere – Basic structural and functional unit of
skeletal muscle.
– Each sarcomere extends from one Z-disk to
another Z-disk
Z-Disk – a network of protein fibers forming an
attachment site for actin myofilaments

9. Actin Myosin

10. • Troponin – attached at a specific interval along
the actin and provide calcium binding sites on the
actin myofilament
• Tropomyosin – located along the groove between
the twisted strands of actin myofilament.
Actin

11. Myosin

15. How does Skeletal Muscle Contracts?
1st the Central
Nervous System
gives the order for
muscle contraction
The order (to contract)
reaches the Muscle thru the
Neuro-Muscular Junction

16. Neuro-muscular Junction

17. • Charge Difference
– Higher concentration of Potassium (K+)
inside the cell membrane.
– Potassium is more permeable than other ions
• Action Potential – Rapid depolarization and
repolarization of the cell membrane
IN
- - - -
-
-
K
Potassium
OUT
+ + + + +
+
Na
Sodium
Membranepotential
Cell Membrane

18. Membranepotential

19. 1.Action potential arriving at
the presynaptic terminal
causes synaptic vesicles to
move and to bind with the
cell membrane
2.Synaptic vesicles release
acetylcholine (Ach) into the
synaptic cleft by exocytosis
3.Acetylcholine diffuses
across the synaptic cleft
4.Acetylcholine binds to
Acetylcholine receptor sites
on Na+ channels in
postsynaptic (muscle) cell
membrane
5.Combination of
Acetylcholine with its
receptor site opens Na+
channels and causes and
increase in the permeability
of the muscle cell membrane

20. ACh binds to receptors
in the sarcolema band
spreads in all direction
Sends electrical
impulse to the t-tubules
Releases Calcium

24. Repolarization
Depolarization

25. • Force of contraction:
• Summation – Increase the force of the
contraction
• Recruitment – Increase the number of muscle
fibers contracting
• Tetanus – Sustained contraction
• Rigor mortis – Muscles become rigid

26. – Types of muscle contraction
– Isometric contraction – equal distance
– Isotonic contraction – equal tension
– Concentric contraction
– Eccentric contraction
– Muscle tone – Refers to the constant tension
produced by the muscle over long periods of
time

27. • Agonist – muscle that accomplishes a
certain movement.
• Antagonist – muscle acting to oppose the
agonist.
• Synergist – members of the same group
acting to produce a movement
• Prime movers
• Fixators