1. The Muscular System

2. The Muscular System
Muscles are responsible for all movement of the body
There are three basic types of muscle
Skeletal
Cardiac
Smooth

3. 3 Types of Muscles

4. Three types of muscle
Skeletal
Cardiac
Smooth

5. Classification of Muscle
Skeletal-
found in limbs
Cardiac-
found in heart
Smooth-
Found in viscera
Striated, multi- nucleated
Striated, 1 nucleus
Not striated, 1 nucleus
voluntary
involuntary

6. Characteristics of Muscle
Skeletal and smooth muscle are elongated
Muscle cell = muscle fiber
Contraction of a muscle is due to movement of microfilaments (protein fibers)
All muscles share some terminology
Prefixes myo and mys refer to muscle
Prefix sarco refers to flesh

7. Skeletal Muscle Most are attached by tendons to bones
Cells have more than one nucleus (multinucleated)
Striated- have stripes, banding
Voluntary- subject to conscious control
Tendons are mostly made of collagen fibers
Found in the limbs
Produce movement, maintain posture, generate heat, stabilize joints

8. Structure of skeletal muscle
Each cell (fibre) is long and cylindrical
Muscle fibres are multi-nucleated
Typically 50-60mm in diameter, and up to 10cm long
The contractile elements of skeletal muscle cells are myofibrils

9. Skeletal muscle - Summary
Voluntary movement of skeletal parts
Spans joints and attached to skeleton
Multi-nucleated, striated, cylindrical fibres

10. Smooth Muscle No striations Spindle shaped Single nucleus
Involuntary- no conscious control
Found mainly in the walls of hollow organs

11. Smooth muscle Lines walls of viscera
Found in longitudinal or circular arrangement

12. Structure of smooth muscle
Spindle shaped uni-nucleated cells
Striations not observed

13. Smooth muscle - Summary
Found in walls of hollow internal organs
Involuntary movement of internal organs
Elongated, spindle shaped fibre with single nucleus

14. Cardiac Muscle Striations Branching cells Involuntary
Found only in the heart
Usually has a single nucleus, but can have more than one

15. Cardiac muscle Main muscle of heart Pumping mass of heart
Critical in humans
Heart muscle cells behave as one unit

16. Structure of cardiac muscle
Cardiac muscle cells (fibres) are short, branched and interconnected
Cells are striated & usually have 1 nucleus
Adjacent cardiac cells are joined via electrical synapses (gap junctions)
These gap junctions appear as dark lines and are called intercalated discs

17. Cardiac muscle - Summary
Found in the heart
Involuntary rhythmic contraction
Branched, striated fibre with single nucleus and intercalated discs

18. Day 2: Sliding Filament Theory

19. Muscle Control Type of muscle Nervous control Type of control Example
Skeletal
Controlled by CNS
Voluntary
Lifting a glass
Skeletal
Cardiac
Regulated by ANS
Involuntary
Heart beating
Smooth
Controlled by ANS
Involuntary
Peristalsis
CNS = central nervous system ANS = autonomic nervous system

20. Muscular System Functions
Provides voluntary movement of body
Enables breathing, blinking, and smiling
Allows you to hop, skip, jump, or do push-ups
Maintains posture
Produces heat

21. Functions Continued Causes heart beat Directs circulation of blood
Regulates blood pressure
Sends blood to different areas of the body

22. Functions Continued Provides movement of internal organs
Moves food through digestive tract (peristalsis)
Enables bladder control
Causes involuntary actions
Reflex actions
Adjusts opening of pupils
Causes hair to stand on end

23. M u s c l e
Muscles are made up of bundles of muscle fibers, called fascicles
Fascicle is a bundle of muscle fibers
A muscle fiber is a muscle cell….made up of many small myofibrils
Myofibrils contain filaments
Two types of protein filaments
T I s s u e
A n a t o m y
Muscle
Fascicle
Muscle Fibers
Myofibrils
Filaments

24. Myofibril Contain two types of protein filaments
Actin- thin protein filaments
Myosin - thick protein filaments
Z disc - point of anchor of actin
Sarcomere - functional unit of a myofibril, region between Z discs,

25. Structure of skeletal muscle
Muscular System
Structure of skeletal muscle

26. Mechanics of a Muscle Contraction
When each sarcomere becomes shorter it causes each myofibril to become shorter.
When each myofibril becomes shorter it causes the muscle fibers to become shorter
When each muscle fiber shortens the overall muscle contracts.
Sarcomere

27. Sarcomere

28. Sliding Filament Theory

29. Three roles for ATP in the contraction of muscle.
Provide the energy for the power stroke (myosin head bends)
B. Disconnecting the myosin head from actin
Actively transporting Ca++ (calcium) out to the sarcoplasmic reticulum

30. RIGOR MORTIS Condition in which muscles become rigid after death
Why…Lack of ATP leads to the inability of the cells to actively pump calcium back into the sarcoplasmic reticulum and the myosin heads are unable to detach from the actin.