1. The Muscular System

2. Four Functions

3. Four Functions
Irritability
Contractibility
Elasticity
Conductivity

4. Types of Muscle Tissue

5. Types of Muscle Tissues

6. Types of Muscle Tissue
All highly vascular for transport of oxygen, CO2, waste and sugars
Human body has three types:

7. Skeletal Muscle

8. Skeletal Muscle Made of elongated cells called muscle fibers
Each fiber has many nuclei and striations
Striations:
Skeletal muscles are voluntary muscles and work in pairs
Antagonistic:

9. Function of Skeletal Muscles
Five major functions:

10. Smooth Muscle

11. Smooth Muscle
Forms the walls of the stomach, intestines, blood vessels, and internal organs
Individual cells are spindle shaped with one nucleus
No striations

12. Cardiac Muscle

13. Cardiac Muscle Location: Cells are cigar shaped Intercalated disc:
Shares three characteristics with other types of muscle:
Intercalated = inserted between

15. Moving Muscles
Muscles are attached to the outer layer of bone with a tough fibrous cord called a tendon
Origin:
Insertion:
Action:
Most muscles work in pairs; one contracts while one relaxes for smooth movement
Flexor:
Extensor:

16. Muscle Structure

17. Muscle Structure From the outside in… Epimysium: Fascicle: Perimysium:
Muscle fiber: muscle cell, large, long, cylindrical, multinucleated and made mostly of microfilaments
Sarcolema
Sarcoplasma
Sarcosomes
Sarcoplasmic reticulum
Endomysium

18. The Sarcomere
Each muscle fiber is made up of threadlike structures called myofibrils
Myofibrils –
Actin:
Myosin:
These overlap, giving the striated appearance
Thin actin filaments are anchored to a structure called the Z line
Region from one Z line to the next is called…

19. The Sarcomere

20. The Sarcomere Unit of muscle contraction is called the sarcomere
Z disc: boundary found on either end of the sarcomere
I, A, H bands: in-between Z discs, alternating light and dark bands
I band – first band moving in from Z disc, composed of actin, light in color
A band – second band, composed of actin and myosin, dark in color
H Zone – middle of sarcomere, only myosin present, relatively light in color but darker than the I band
H Zone – middle of the sarcomere
M line – dark line in the middle of H Zone

21. Sliding Filament Theory
In May 1954, Hugh Huxley and Allan Huxley published their findings of the sliding filament theory
The theory stated that skeletal muscle contracted when two types of filaments, consisting of the proteins myosin and actin, “slid” past each other without either filament’s length actually changing

23. Muscular Contraction

24. Steps of Muscular Contraction
The Central Nervous System initiates a sequence to begin the sequence of events leading to contraction
Action potential from the motor neuron moves down to terminal end and then calcium ions (Ca++) diffuse into the terminal
Ca++ trigger the synaptic vesicles to release acetylcholine (ACh)
ACh diffuses across synaptic clef to a receptor site on the sarcolemma
ACh cause new action potential to spread from nerve to muscle
Action potential spreads over the sarcolemma until it finds an opening
It enters the opening to the sarcoplasmic reticulum, where it triggers the release of Ca++ into the sarcoplasm
Ca++ cause active sites on actin to be exposed
Myosin crossbridges link up with the active sites on actin
Actin moves inward, sarcomere shortens, muscle fibers contract and use ATP
Action potential = impulse

25. Stopping Muscular Contraction
Acetylcholinesterase (AChE - enzyme) is released as muscle contracts and neutralizes the ACh
No more action potential is traveling to muscle
Calcium does not tighten so the crossbridges on mysoin release
Muscles relax