Muscular system

1. MUSCULAR SYSTEMMUSCULAR SYSTEM
This system is This system is
responsible for the responsible for the
movement and movement and
locomotion of a locomotion of a
body. This system is body. This system is
composed of skeletal composed of skeletal
muscles, cardiac muscles, cardiac
muscles, and smooth muscles, and smooth
muscles.muscles.

2. Smooth MusclesSmooth Muscles
Smooth Muscle lacks Smooth Muscle lacks
the visible cross-the visible cross-
striations, but, unlike striations, but, unlike
skeletal and cardiac skeletal and cardiac
muscle; it is found muscle; it is found
mostly in the walls of mostly in the walls of
hollow viscera such as hollow viscera such as
intestines.intestines.

3. Smooth muscle’s continuous contractions Smooth muscle’s continuous contractions
provide the motive power for digestion, provide the motive power for digestion,
secretion and excretion. Like cardiac muscle, secretion and excretion. Like cardiac muscle,
smooth muscle is normally under the dual smooth muscle is normally under the dual
control of hormones and the autonomic control of hormones and the autonomic
nervous system, but it also has intrinsic nervous system, but it also has intrinsic
contractility and it is not under voluntary contractility and it is not under voluntary
control.control.

4. Cardiac MusclesCardiac Muscles
The hearts of The hearts of
vertebrates are vertebrates are
composed of this composed of this
kind of muscle. kind of muscle.
Compared to the Compared to the
skeletal muscle, it skeletal muscle, it
has a smaller, has a smaller,
interconnected cells, interconnected cells,
each with a single each with a single
nucleus.nucleus.

5. Cardiac muscles also has cross-striations, but, Cardiac muscles also has cross-striations, but,
unlike somatic muscle fibers, its fibers branch unlike somatic muscle fibers, its fibers branch
and interdigitate so that the mass of muscle and interdigitate so that the mass of muscle
tends to function as one unit or syncytium. tends to function as one unit or syncytium.
Cardiac muscle will continue to contract Cardiac muscle will continue to contract
rhythmically when the nerve supply is cut.rhythmically when the nerve supply is cut.

6. Skeletal MusclesSkeletal Muscles
Skeletal muscles are Skeletal muscles are
straited muscle straited muscle
because of their because of their
striped appearance striped appearance
under the under the
microscope. This microscope. This
muscle produce muscle produce
movement of the movement of the
skeleton when they skeleton when they
contract. contract.

7. Skeletal Muscles comprise the great bulk of Skeletal Muscles comprise the great bulk of
the somatic (body) musculature (about 40% of the somatic (body) musculature (about 40% of
the total body weight). Skeletal muscle fibers the total body weight). Skeletal muscle fibers
do not normally contract in the absence of do not normally contract in the absence of
nervous stimulation and they are mostly under nervous stimulation and they are mostly under
voluntary control. The muscles of the arms and voluntary control. The muscles of the arms and
legs are examples. Skeletal muscle is also legs are examples. Skeletal muscle is also
known as striped, striated, somatic or known as striped, striated, somatic or
voluntary muscle.voluntary muscle.

8. Muscle fiber and its compositionsMuscle fiber and its compositions
The functional element of skeletal muscle is the The functional element of skeletal muscle is the
muscle fiber, which may vary from 1 to 50 mm in muscle fiber, which may vary from 1 to 50 mm in
length and 10 to 100 length and 10 to 100 μμm in width. Each muscle fiber m in width. Each muscle fiber
has many fine threads or myofibrils running has many fine threads or myofibrils running
throughout its length.throughout its length.

9. Myofibrils and MyofilamentsMyofibrils and Myofilaments
Each muscle fiber Each muscle fiber
encloses a bundle encloses a bundle
of 4 to 20 elongated of 4 to 20 elongated
structures called structures called
Myofibrils and each Myofibrils and each
myofibrils is myofibrils is
composed of thick composed of thick
and thin and thin
myofilaments.myofilaments.

10. The Myosin and ActinThe Myosin and Actin
Myofibril contains two Myofibril contains two
different types of still different types of still
inner myofilaments. The inner myofilaments. The
thicker myofilaments thicker myofilaments
consist of the protein consist of the protein
myosin and each is myosin and each is
surrounded by a surrounded by a
hexagonal arrangement hexagonal arrangement
of thinner actin of thinner actin
myofilaments.myofilaments.

11. SarcomereSarcomere
Thick and thin myofilaments are stacked together to Thick and thin myofilaments are stacked together to
produce the dark bands, called A-bands; the thin produce the dark bands, called A-bands; the thin
filaments alone are found in the light bands, or I-filaments alone are found in the light bands, or I-
bands. Each I-band in a myofibril is divided in half bands. Each I-band in a myofibril is divided in half
by a disc of protein, called a Z-line because of its by a disc of protein, called a Z-line because of its
appearance in the electron micrographs. The thin appearance in the electron micrographs. The thin
filaments are anchored to these discs of proteins that filaments are anchored to these discs of proteins that
form the Z-line. This repeating structure, called a form the Z-line. This repeating structure, called a
Sarcomere, is the smallest subunit of muscle Sarcomere, is the smallest subunit of muscle
contraction.contraction.

12. The SarcomereThe Sarcomere