1. Chapter 6 Muscular System

2. Types of Muscles Skeletal – striated & voluntary Smooth - involuntary
Cardiac – heart
Striated means it appears striped

3. Structure of a Muscle
Muscles are composed of many FIBERS that are arranged in bundles called FASCICLES.
Muscles are separated from each other by FASCIA, which form the APONEUROSES and TENDONS that connect the muscles to bones.
Muscle Connective Tissue:
Epimysium – outermost layer that surrounds the entire muscle
Perimysium – separates and surrounds fascicles (bundles of muscle fibers)
Endomysium – surrounds each individual muscle fiber

4. Muscle Functions Produces Movement Maintains Posture Stabilizes Joints
The SOLE function of Muscular Tissue is to contract or shorten. As it contracts it:
Produces Movement
Maintains Posture
Stabilizes Joints
Generates Heat

5. Structure of a Muscle Fiber (muscle cells)
Each muscle cell is surrounded by a specialized cell membrane called the SARCOLEMMA.
The cytoplasm is called the SARCOPLASM.
Each muscle cell is filled with MYOFIBRILS which in turn are composed of MYOFILAMENTS.

6. Myofibril Structure
Myofibrils – contain myofilaments of myosin (thick) and actin (thin).
The myofilaments overlap to form I and A bands on the fiber:
DARK BANDS – A bands - myosin
LIGHT BANDS – I bands – actin
In the middle of each I band is a dark line called a Z line.
One Z line to the next is a SARCOMERE.

9. Neuromuscular Junction
The muscle fiber and the motor neuron make up the neuromuscular junction.
Motor end plate – folded area where the muscle and the neuron communicate
Synaptic cleft – the gap between the neuron and the motor end plate
Synaptic vesicles – where the neurotransmitters are stored

11. Neuromuscular Junction
The neurotransmitter that crosses the gap is ACETYLCHOLINE
ACH is broken down by CHOLINESTERASE.

12. Neuromuscular Junction
The theory of how a muscle contracts is the SLIDING FILAMENT THEORY.
The contraction occurs when the THICK filament (myosin) slides past the THIN filament (actin).
The sliding filament theory involves 5 different molecules plus CALCIUM
ATP
Myosin
Actin
Acetylcholine
Cholinesterase

13. Energy Source
The energy for muscle contraction comes from ATP provided by the process of CELLULAR RESPIRATION.
The molecule CREATINE PHOSPHATE helps with the regeneration of ATP.
Much of our body’s heat is produced by this process, which in turns helps maintain homeostasis.

14. Terms related to Muscle Contraction
Threshold stimulus
All or none response
Motor Unit
Recruitment
Muscle tone
Muscle Hypertrophy
Muscle Atrophy
Muscle fatigue
Muscle cramp
Oxygen debt
Origin and insertion
Tetanus
Rigor mortis

15. 1. Threshold Stimulus. Minimal strength to cause a contraction
1. Threshold Stimulus Minimal strength to cause a contraction Motor neuron releases enough Acetylcholine to reach threshold
2. All-or-None Response Fibers don’t contract partially, they either do or they don’t