Muscular System. Intro to Muscles 1.Nearly half our weight comes from muscle tissue 2.There are...
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Transcript of Muscular System. Intro to Muscles 1.Nearly half our weight comes from muscle tissue 2.There are...
Muscular System
Intro to Muscles
1. Nearly half our weight comes from muscle tissue
2. There are 650 different muscles in the human body
Three Main Functions
1.Responsible for body movement
2.Responsible for body form and shape (posture)
3.Responsible for body heat and maintaining body temperature
4 Characteristics of a Muscle
1.CONTRACTILITY – the capability or quality of shrinking or contracting
2.EXCITEABILITY– the ability to respond to certain stimuli by producing impulses
3.EXTENSIBILITY – the ability to be stretched.
4.ELASTICITY – ability of muscle to return to its original length when relaxing.
Types of Muscle● Skeletal – striated, voluntary, multinucleated, long and run parallel
to eachother, found on bones
● Smooth – non-striated, involuntary, single nucleus, tapered, found in many organs, contract using peristalsis
● Cardiac – striated, involuntary, 1-2 nuclei, long and branched, found in heart, contain intercalated discs, rhythmic contractions
The word “striated” means striped. Skeletal muscle appears striped under a microscope.
Muscles and Muscle Fiber Structure • Individual muscles are separated by FASCIA, which also
forms tendons
**Tendonitis – inflammation of the tendons
• Muscle fibers (cells) are arranged in bundles called FASCICLES
• EPIMYSIUM = outermost layer, surrounds entire muscle.
• PERIMYSIUM = separates and surrounds fascicles (bundles of muscle fibers)
• ENDOMYSIUM = surrounds each individual muscle fiber
This model of the muscles uses straws to represent fibers.
Green = endomysiumYellow = perimysiumBlue = epimysium
Muscle Layers
Epimysium
Perimysium
Endomysium
It is important to remember the hierarchy
ACTIN (light)
FASCICLES
MUSCLE FIBERS
MYOFIBRILS
FILAMENTS
MUSCLE
MYOSIN (dark)
Wrapped in EPIMYSIUM
Wrapped in PERIMYSIUM
Wrapped in ENDOMYSIUM
Sarcolemma = muscle fiber membrane
Sarcoplasm = inner material surrounding fibrils (like cytoplasm)
Myofibrils = individual threads within muscle fiber made of myofilaments
Muscles / Cells
SarcolemmaMitochondrion
Sarcoplasm
Myofibril
Nucleus
Myofibrils are made of
ACTIN = thin filamentsMYOSIN = thick filaments
Myofilaments ACTIN (thin) and MYOSIN (thick)
-- form dark and light bands A band = dArk • thick (myosin) I band = lIght • thIn (actin)
SLIDING FILAMENT THEORY (MODEL) - theory of how muscle contracts
This occurs as the thin filament (actin) slides past the thick filaments (myosin)
Explanation of Skeletal Muscle and Sliding Filament Theory
Start at 1:40
http://www.youtube.com/watch?v=mejCXr7p37U&spfreload=10
How Muscles Work with the Nervous System
NEUROMUSCULAR JUNCTION - where a nerve and muscle fiber come together
Neuromuscular Junction
• Motor neurons stimulate muscle fibers to contract
• Motor neuron secretes neurotransmitter known as ACETYLCHOLINASE
• One motor neuron connected to muscle fibers make up a motor unit
Energy Source-ATP is produced by CELLULAR RESPIRATION; occurs in the mitochondria
-Creatine phosphate increases regeneration of ATP
* Only 25% of energy produced during cellular respiration is used in metabolic processes - the rest is in the form of HEAT.
- maintains body temperature.
Other Terms1. All-or-None Response
2. Motor Unit
3. Recruitment
4. Muscular Hypertrophy
5. Muscular Atrophy
6. Muscle Cramp
7. Origin & Insertion
8. Strain
9. Sprain
10. Hernia
1. All-or-None Response
Fibers do not contract partially, they either do or don't
2. Motor Unit The muscle fiber + the motor neuron
3. Recruitment• More fibers contract as the
intensity of stimulus increases
4. Hypertrophy - muscles enlarge (working out or certain disorders)
5. Atrophy - muscles become small and weak due to disuse
Cardiomyopathy
6. Muscle Cramp - a sustained involuntary contraction
7. Origin and Insertion
Origin = the immovable end of the muscle
Insertion = the movable end of the muscle
8. Strain – tear in muscles/tendons from excessive use
9. Sprain – tear in ligaments
10. Hernia – protrusion of an organ or tissue through a weak muscle or opening
11. Ligaments vs. Tendons
Ligaments – bone to bone
Tendons – muscle to bone
Treatments (R.I.C.E.)
1. Rest
2. Ice
3. Compression
4. Elevation