Muscular System
Vocabulary Words
Skeletal Muscle
Visceral Muscle
Cardiac Muscle
Latissimus Dorsi
Pectoralis Major
Isotonic exercises
Overload Principle
Slow twitch
Fast twitch
Isometric exercises
Function of Muscle Tissue
 The main function of the muscular system is movement. Muscles are the
only tissue in the body that has the ability to contract and therefore move
the other parts of the body.
 the maintenance of posture and body position. Muscles often contract to
hold the body still or in a particular position rather than to cause
movement. The muscles responsible for the body’s posture have the
greatest endurance of all muscles in the body—they hold up the body
throughout the day without becoming tired.
 Another function related to movement is the movement of substances
inside the body. The cardiac and visceral muscles are primarily responsible
for transporting substances like blood or food from one part of the body to
 The final function of muscle tissue is the generation of body heat. As a
result of the high metabolic rate of contracting muscle, our muscular
system produces a great deal of waste heat. Many small muscle
contractions within the body produce our natural body heat. When we
exert ourselves more than normal, the extra muscle contractions lead to a
rise in body temperature and eventually to sweating.
The muscular system makes up nearly half the weight of the
human body, this is why when we train we sometimes put on
weight instead of losing it. We put on muscle weight.
The muscles provide the forces that enable the body to
move. Muscles stretch across joints to link one bone with
another and work in groups to respond to nerve impulses.
There are three types of muscle:
Skeletal muscle
•There are nearly 650 skeletal muscles in the
human body!
•Skeletal muscles are attached to the skeleton
•They work in pairs: one muscle moves the bone in
one direction and the other moves it back again
•Skeletal muscles are voluntary muscles - in other
words we think about what movements we want to
make (at least, usually!) and send messages via
our nervous system to tell the appropriate
muscle(s) to contract.
•Muscle contractions can be short, single
contractions or longer ones.
Smooth/Visceral Muscle
 Smooth muscle is found in our internal organs: in our digestive
system, our blood vessels, our bladder, our respiratory organs and, in a
female, the uterus.
 Smooth muscle can stretch and maintain tension over extended
 Smooth muscles are involuntary muscles - in other words we do not
have to think about contracting them because they are controlled
automatically by the nervous system. It would be pretty inconvenient if we
had to think about digesting our food, for example!
 The term “smooth muscle” is often used to describe visceral muscle
because it has a very smooth, uniform appearance when viewed
under a microscope. This smooth appearance starkly contrasts with the
banded appearance of cardiac and skeletal muscles.
Cardiac muscle
 As the name should tell you, cardiac muscle is found only in the heart.
 It can stretch, just like smooth muscle, and contract like skeletal
 It is a twitch muscle - it only does short single contractions
 Like smooth muscle, cardiac muscle is involuntary. It'd be rather dangerous
if it were voluntary - we could stop our heart beating any time we wanted! ,
 cardiac muscle stimulates itself to contract. The natural pacemaker of the
heart is
made of cardiac muscle tissue that stimulates other cardiac muscle
cells to
Gross Anatomy of a Skeletal Muscle
Most skeletal muscles are attached to two bones through
tendons. Tendons are tough bands of dense regular
connective tissue whose strong collagen fibers firmly
attach muscles to bones. Tendons are under extreme
stress when muscles pull on them, so they are very strong
and are woven into the coverings of both muscles and bones.
Muscles move by shortening their length, pulling on tendons,
and moving bones closer to each other. One of the bones is
pulled towards the other bone, which remains stationary. The
place on the stationary bone that is connected via tendons to
the muscle is called the origin. The place on the moving bone
that is connected to the muscle via tendons is called the
insertion. The belly of the muscle is the fleshy part of the
muscle in between the tendons that does the actual
STRENGTH is the amount of force a muscle can exert.
All of us need strength to perform our daily activities.
If you use muscles regularly they will stay strong. If
not, they will weaken. Strength in muscle relates to
good health by helping you: 1)maintain good posture,
2)reduce fatigue, 3)prevent muscle injuries and soreness,
4)prevent backache.
Muscles use oxygen when contracting. The oxygen needed is
carried from the lungs to the muscles by blood (red blood
cells). The more a muscle works (contracts), the more oxygen
is needed. Although muscles can store some oxygen
temporarily, eventually muscle cannot get enough oxygen.
The process of using stored oxygen in a muscle creates a
substance called lactic acid. An accumulation of lactic acid
causes a muscle to lose its’ ability to contract
and sometimes causes cramping.
Principles of Strength Exercising
Overload – a muscle must contract harder than normal if it is
to become stronger; a muscle must work more than normal.
Progression – overload gradually, increase the load over a
period of time to get the best muscle strength.
Specificity – exercise the specific muscles you want to
develop. Leg exercises develop the legs, arm exercises
develop the arm, etc.
IMPROVING MUSCLE STRENGTH : You must exert muscular force against a
ISOTONIC EXERCISES: muscles contract and body parts move ( i.e. weightlifting)
ISOMETRIC EXERCISES: the muscle contracts when working against stationary
object. The muscles work, but the body parts do not move. Isometric muscles are
often recommended after an extended period of inactivity, such as a broken limb.
MUSULAR ENDURANCE: the ability of a muscle to work for long periods of time
without getting tired. Muscular endurance depends on the kind of muscle fibers
that make up the muscles.
LOW INTENSITY EXERCISES - build the muscular endurance needed for daily
activities – use only the body parts you use daily (in other words, do nothing).
MEDIUM INTENSITY EXERCISES - build the muscular endurance needed for good
fitness. Do exercises and body weight calisthenics (pull-ups, push-ups, etc.).
HIGH INTENSITY EXERCISES - build muscular endurance for high-level
performance. Combine strength training with increased repetitions for endurance.
There are 2 kinds of muscle fibers:
SLOW-TWITCH FIBERS. contract at a slow rate.
• 1) use oxygen from the blood to release energy
• 2) do not tire easily
• 3) have the most endurance of all muscles.
FAST-TWITCH FIBERS contract at a fast rate.
• 1) do not use oxygen from the blood to release energy
• 2) have greater strength
• 3) have less endurance.
The relative number of the kind of fibers in a given muscle
does not change, but the kind of exercise you do influences
the size of the fibers and their ability to use oxygen.
Muscle Facts
•Muscle is a soft tissue in the body of humans and animals. Main purpose to produce force and
•The word muscle is derived from the Latin term musculus, meaning "little mouse". This Latin
term could be due to the shape of some muscles or because muscles contracting under the skin
can look like a mouse moving under a rug.
•Skeletal muscle can be further divided into two types, slow twitch and fast twitch.
•Slow twitch (Type I) muscle contain proteins that give it a rich red color. This muscle carries
more oxygen efficiently and using fats, proteins or carbs as energy slow twitch muscle fibers
contract over a long period of time. Therefore type I muscle fiber works well for aerobic sports
i.e. long distance running and cycling.
•Fast twitch (Type II) muscle is whiter in color as it has less myoglobin (a oxygen carrying
protein). Fast twitch fibers contract quickly and powerfully, however they fatigue rapidly.
•Therefore type II muscle fiber is useful for anaerobic exercise such as sprinting or for strength
sports like weightlifting.
•Muscle makes up around half of the total human body weight. Muscle tissue is also around 15%
denser than fat tissue.
•It takes 17 muscles in the face for us to smile and 43 muscles to frown.
•If muscle strength is regarded as the ability to use force on something then the jaw muscle
(masseter) is the strongest in the body.
•The strongest muscles in relation to the job they do is the external muscles of the eye which
are large and about 100 times stronger than they need to be in relation to the small size and
weight of the eyeball.
•The tongue has 8 muscles, so is technically not the strongest muscle in the body.
•The heart cardiac muscle does the most work of any muscle over a lifetime.
•Cerebral palsy is a disorder that affects balance and motor functions, while muscular dystrophy
is a genetic disease that damages muscle fibers.
•Muscle memory is created by practicing an action over and over again. Our muscles fine tune
themselves, becoming more precise and exact in what they do. So practice is very important
when learning a sport!!
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