Download Muscular System

Muscular System
Muscular System
1.
The Skeleton and its joints support, protect, and provide flexibility for the body, but the
Skeleton CANNOT Move Itself.
2.
That job is performed by the Muscle Tissue that makes up the MUSCULAR SYSTEM.
3.
A MUSCLE TISSUE IS TISSUE THAT CAN CONTRACT IN A COORDINATED FASHION
AND INCLUDES MUSCLES TISSUE, BLOOD VESSELS, NERVES, AND CONNECTIVE
TISSUE.
4.
Approximately 40 to 50 percent of the MASS of the Human Body is composed of Muscle
Tissue.
5.
THE MUSCULAR SYSTEM IS COMPOSED OF MUSCLE TISSUE (MUSCLE FIBER or
cells) THAT IS HIGHLY SPECIALIZED TO CONTRACT TO PRODUCE MOVEMENT WHEN
STIMULATED.
6.
The Word Muscle is derived from the Latin word "MUS", meaning mouse.
7.
Muscle tissue is found everywhere within the body, not only beneath the skin but deep
within the body, surrounding many internal organs and blood vessels.
8.
The size and location of muscle tissue helps determine the shape of our bodies and the
way we move.
TYPES OF MUSCLE
TISSUE (THREE TYPES)
SKELETAL MUSCLE
Skeletal Muscle
1. Skeletal Muscle is Responsible for moving parts of the body, such
as the limbs, trunk, and face.
2. SKELETAL MUSCLES ARE GENERALLY ATTACHED TO BONES
AND ARE AT WORK EVERY TIME WE MAKE A MOVE.
3. SKELETAL MUSCLES ARE RESPONSIBLE FOR VOLUNTARY
(CONSCIOUS) MOVEMENT.
4. A Skeletal Muscle is made of Elongated Cells called MUSCLE
FIBERS. Varying movements require Contraction of variable
numbers of Muscles Fibers in a Muscle.
5. Skeletal Muscle fibers are grouped into dense bundles called
FASCICLES. A group of Fascicles are bound together by
Connective Tissue to form a MUSCLE.
Skeletal Muscle
• 6. When viewed under a microscope, Skeletal Muscles appear to
have STRIATIONS (BANDS OR STRIPES). This gives Skeleton
Muscle the name of VOLUNTARY OR STRIATED MUSCLE.
• 7. MOST SKELETAL MUSCLES ARE CONSCIOUSLY
CONTROLLED BY THE CENTRAL NERVOUS SYSTEM (CNS).
•
• 8. Skeleton Muscle Cells are LARGE and have MORE than ONE
NUCLEUS. They vary in length from 1mm to 30 to 60 cm.
• 9. Because they are so long and slender, they are often called
MUSCLE FIBERS rather than Muscle Cells.
• 10. Muscle Fiber together with the Connective Tissue, Blood
Vessels, and Nerves form a Skeletal Muscle
Smooth Muscles
Smooth Muscle
1. SMOOTH MUSCLES ARE USUALLY NOT UNDER VOLUNTARY CONTROL.
2. SMOOTH MUSCLE CELLS ARE SPINDLE-SHAPED AND HAVE A SINGLE
NUCLEUS, ARE NOT STRIATED and Interlace to form Sheets of smooth
Muscle Tissue.
3. SMOOTH MUSCLES ARE FOUND IN MANY INTERNAL ORGANS, STOMACH,
INTESTINES, AND IN THE WALLS OF BLOOD VESSELS.
4. Smooth muscle fibers are surrounded by connective tissue, but the connective
tissue Does Not unite to form TENDONS as it does in Skeletal Muscles.
5. Most Smooth Muscle Cells can CONTRACT WITHOUT Nervous
Stimulation. Because most of its movements Cannot be consciously controlled,
Smooth Muscle is referred to as Involuntary Muscle.
6. The contractions in Smooth Muscles move food through our digestive tract,
control the way blood flows through the circulatory system, and increases the
size of the pupils of our eyes in bright light.
Cardiac Muscle
Cardiac Muscle
1. THE ONLY PLACE IN THE BODY WHERE CARDIAC MUSCLE IS FOUND
IS IN THE HEART.
2. Cardiac Cells are Striated, but they are NOT under Voluntary Control.
3. Cardiac Muscle Contract Without Direct stimulation by the Nervous
System. A bundle of specialized muscle cells in the upper part of the heart
sends electrical signals through cardiac muscle tissue, causing the heart to
rhythmically contract and pump blood through the body.
4. The Cardiac Muscle Cell contains ONE Nucleus located near the center,
adjacent cells form branching fibers that allow Nerve Impulses to pass from
cell to cell.
Muscle Structure
1.
A Muscle Fiber is a single, Multinucleated Muscle Cell.
2. A Muscle may be made up of hundreds or even thousands of Muscle
Fibers, depending on the Muscles Size.
3. Although Muscle Fiber makes up most of the Muscle Tissue, a large
amount of Connective Tissue, Blood Vessels, and Nerves are also
present.
4. Connective Tissue Covers and Supports each Muscle Fiber and
reinforces the Muscle as a whole.
5. The health of Muscle depends on a sufficient Nerve and Blood
Supply. Each Skeletal Muscle has a Nerve Ending that controls
its activity.
6. Active Muscles use a lot of Energy and require a continuous supply of Oxygen
and Nutrients, which are supplied by Arteries. Muscles produce large amounts
of Metabolic Waste that must be removed by Veins.
7. Muscle Fibers consist of Bundles of threadlike structures called MYOFIBRILS.
8. Each Myofibril is made up of TWO Types of Protein Filaments- Thick ones and
Thin ones.
9. The THICK FILAMENTS are made up of a PROTEIN called MYOSIN.
10. The THIN FILAMENTS are made of a PROTEIN called ACTIN.
11. Myosin and Actin Filaments are arranged to form overlapping patterns, which
are responsible for the Light and Dark Bands that can be seen in Skeletal
(Striated Appearance) Muscle.
12. Thin Actin Filaments are Anchored at their Midpoints to a structure called the
Z-LINE.
13. The Region From one Z-line to the next is called a SARCOMERE the
Functional Unit of Muscle Contractions
MECHANISM OF MUSCLE
CONTRACTIONS
1. The Sarcomere is the functional unit of Muscle contractions.
2. When Muscle Cells Contract, the light and dark bands contained in
Muscle Cells get closer together.
3. This happens because when a Muscle Contracts, Myosin Filaments
and Actin filaments interact to shorten the length of a Sarcomere.
4. When Myosin Filaments and Actin Filaments come near each other,
many knob (heads) like projections in each Myosin Filament form
CROSS-BRIDGES with an Actin Filament.
5. When the Muscle is Stimulated to Contract, the Cross-bridges
MOVE, PULLING the Two Filaments past each other.
MECHANISM OF MUSCLE
CONTRACTIONS
•
6. After each Cross-bridge has moved as far as it can, it releases the Actin
Filament and returns to its original position. The Cross-bridge then attaches
to the Actin Filament at another place and the cycle is repeated. This action
Shortens the Length of the Sarcomere.
•
7. The synchronized shortening of Sarcomeres along the full length of a
Muscle Fiber causes the Whole Fiber, and hence the Muscle, to Contract.
•
8. WHEN THOUSANDS OF ACTIN AND MYOSIN FILAMENTS INTERACT
IN THIS WAY, THE ENTIRE MUSCLE CELL SHORTENS.
•
9. THIS CONCEPT IS THE SLIDING FILAMENT THEORY.
•
10. Muscle Contractions require Energy, which is supplied by ATP. This
Energy is used to Detach the Myosin Heads from the Actin Filaments.
MECHANISM OF MUSCLE
CONTRACTIONS
11. Because Myosin Heads must Attach and Detach a number of times during a
Single Muscle Contraction, Muscle Cells must have a Continuous Supply of
ATP.
12. Without ATP the Myosin Heads would stay Attached to the Actin Filaments,
keeping Muscles Permanently Contracted.
13. A Muscle Contraction, like a Nerve Impulse, is an All-or-None Responseeither Fibers Contract or they Remain Relaxed.
14. The force of a Muscle Contraction is determined by the number of Muscle
fibers that are Stimulated. As more fibers are activated, the force of the
contraction Increases.
15. Some Muscles, such as the muscles that hold the body in an upright
position and maintain posture, are nearly always at least Partially
Contracted.
CONTROL OF MUSCLE CONTRACTION
1. Muscles are useful only if they Contract in a Controlled fashion.
2. Motor Neurons connect the CNS to Skeleton Muscle Cells
(EFFECTORS); Impulses (ACTION POTENTIALS) from Motor Neurons
Control the Contraction of Skeleton Muscle Cells.
3. The point of contact between a Motor Neuron and a Muscle Cell is called the
NEUROMUSCULAR JUNCTION. 4. Vesicles, or pockets, in the AXON
TERMINALS of the Motor Neuron release molecules of the
NEUROTRANSMITTER ACETYLCHOLINE.
5. These molecules Diffuse across the SYNAPSE, producing and IMPULSE in
the Cell Membrane of the Muscle Cell.
6. The impulse causes the release of Calcium ions within the cell. The Calcium
Ions affect regulatory proteins that allow Actin and Myosin Filaments to
interact and form cross-bridges.
CONTROL OF MUSCLE CONTRACTION
7. A Muscle Cell WILL remain in a state of CONTRACTION until the production
of Acetylcholine STOPS.
8. An ENZYME called ACETYLCHOLINESTERASE, also produced at the
Neuromuscular Junction, DESTROYS ACETYLCHOLINE, permits the
reabsorption of Calcium Ions into the Muscle Cell, and Terminates the
Contraction.
9. You can have a Weak or Strong Contraction depending on what you are
trying to accomplish. The BRAIN (frontal lobes of the cerebrum) decides
what and how many Muscles Cells need to Contract. Blinking your eye
would be a Weak Contraction, but lifting heavy weights, the brain would
signal most Muscle Cells to Contract.
10. MUSCLE SENSE IS THE BRAINS ABILITY TO KNOW WHERE OUR
MUSCLES ARE AND WHAT THEY ARE DOING. Permits us to perform
everyday activities without having to concentrate on muscle position.
HOW MUSCLES AND BONES INTERACT
1. Skeleton Muscles generate Force and produce Movement only by
CONTRACTING or PULLING on Body Parts.
2. Individual Muscles can only PULL; they CANNOT PUSH.
3. Skeleton Muscles are joined to bone by TOUGH CONNECTIVE
TISSUE CALLED TENDONS.
4. TENDONS ATTACH MUSCLE TO BONE; THE ORIGIN IS THE
MORE STATIONARY BONE, THE INSERTION IS THE MORE
MOVABLE BONE.
5. Tendons are attached in such a way that they PULL on the Bones
and make them work like LEVERS. The movements of the
Muscles and Joints enable the Bones to act as LEVERS.
HOW MUSCLES AND BONES INTERACT
6. The Joint functions as a FULCRUM (The fixed point
around which the lever moves) and the Muscles provide
the FORCE to move the Lever.
7. Usually there several Muscles surrounding each Joint
that PULL in DIFFERENT DIRECTIONS.
8. MOST SKELETAL MUSCLES WORK IN PAIRS.
9. When one Muscle or set of Muscles CONTRACTS, the
other RELAXES.
HOW MUSCLES AND BONES INTERACT
10. The Muscles of the upper arm are a good example of this dual action:
ANTAGONISTIC MUSCLES. FLEXOR, A MUSCLE THAT BENDS A
JOINT. EXTENSOR, A MUSCLE THAT STRAIGHTENS A JOINT.
A. When the BICEPS Muscle (on the front of the upper arm, FLEXOR) CONTRACTS,
it BENDS OR FLEXES THE ELBOW JOINT.
B. When the TRICEPS Muscle (on the back of the upper arm, EXTENSOR)
CONTRACTS, it opens, or extends, the elbow joint.
C. A controlled movement requires contraction by both muscles.
11. ANTAGONISTIC MUSCLES ARE OPPONENTS, MUSCLES WHICH HAVE
OPPOSING OR OPPOSITE FUNCTIONS. A muscle pulls when it contracts, but
exerts no force when it relaxes and CANNOT PUSH. When one muscle Pulls a bone
in one direction, another muscle is needed to PULL the bone in the other direction.
12. SYNERGISTIC MUSCLES ARE THOSE WITH THE SAME FUNCTION, OR THOSE
THAT WORK TOGETHER TO PERFORM A PARTICULAR FUNCTION. They also
stabilize a joint to make a more precise movement possible.
HOW MUSCLES AND BONES INTERACT
13. A normal characteristic of all Skeleton Muscles is that they remain
in a state of PARTIAL CONTRACTION.
14. At any given time, some Muscles are being Stimulated while other
are not. This causes a TIGHTENED, or FIRMED, Muscle and is
known as MUSCLE TONE.
15. Muscle Tone is responsible for keeping the back and legs straight
and the head upright even when you are relaxed.
16. EXERCISE IS THE KEY TO MAINTAINING GOOD MUSCLE TONE
WITHIN YOUR BODY.
17. MUSCLES THAT ARE EXERCISED REGULARLY STAY FIRM
AND INCREASE IN SIZE BY ADDING MORE MATERIALS TO THE
INSIDE OF MUSCLE FIBERS.
HOW MUSCLES AND BONES INTERACT
• 18. MUSCLE FATIGUE is a Physiological Inability of a muscle to
contract. Muscle fatigue is a result of a relative depletion of
ATP. When ATP is absent, a state of continuous contraction
occurs. This causes severe muscle cramps.
• 19. OXYGEN DEBT is a temporary Lack of Oxygen. When this
occurs Muscles will switch from the normal Aerobic Respiration to a
form of Anaerobic Respiration called Lactic Acid Fermentation. As
the oxygen becomes Depleted, the muscle cells begin to
switch. Oxygen debt leads to the accumulation of Metabolic Waste
(Lactic Acid) in the muscle fibers, resulting in muscle fatigue, pain,
and even cramps. Eventually, the lactic acid diffuses into the blood
and is transported to the Liver. So if you ever experienced Soreness
after prolong exercise, it may have been caused by Oxygen Debt Your body could not provide your Muscles the Oxygen they needed
to function properly.