Muscular system
FUNCTIONS OF THE MUSCULAR
SYSTEM
1. Movement of the body. Contraction of
skeletal muscles is responsible for the overall
movements of the body, such as walking,
running, and manipulating objects with the
hands.
2. Maintenance of posture. Skeletal muscles
constantly maintain tone, which keeps us sitting
or standing erect.
3. Respiration. Muscles of the thorax carry out
the movements necessary for respiration.
4. Production of body heat. When skeletal
muscles contract, heat is given off as a Muscle Fiber Structure
by-product. This released heat is critical to the
maintenance of body temperature. ● A muscle fiber is a single cylindrical fiber, with
5. Communication. Skeletal muscles are several nuclei located at its periphery. The
involved in all aspects of communication, largest human muscle fibers are up to 30 cm
including speaking, writing, typing, gesturing, long and 0.15 mm in diameter.
and facial expressions.
6. Constriction of organs and vessels. The
contraction of smooth muscle within the walls of
internal organs and vessels causes those
structures to constrict. This constriction can
help propel and mix food and water in the
digestive tract, propel secretions from organs,
and regulate blood flow through vessels.
7. Contraction of the heart. The contraction of
cardiac muscle causes the heart to beat,
propelling blood to all parts of the body.
, Characteristics of skeletal Muscle: ● Concentric Contraction: isotonic contraction
in which muscle tension increases as
muscle shortens.
● Constitute approximately 40% of body weight
- Many common movements are produced by
Striated muscle
concentric muscle contractions.
● Eccentric Contraction: are isotonic
Four major functional characteristics contraction in which tension is maintained as
muscle lengthen.
● Contractility: ability of skeletal muscle to - Eccentric contractions are used when a person
shorten with force slowly lowers a heavy weight.
● Excitability : capacity of skeletal muscle to - occurs in the hamstring muscles when a person
respond to a stimulus runs downhill.
● Extensibility: skeletal muscle can be stretched
● Elasticity: ability to recoil to their original Gross Anatomy
resting length after they have been stretched
Some muscle are attached to the bone
Muscle Twitch ● Facial muscles are attached to the skin
● Muscle is connected to a bone by a TENDON
● is the contraction of a muscle fiber in response ● Tendon: very short or almost non-existent
to a stimulus. - long, cable-like structure
- some are broad, sheetlike structures, called
Three Phases of Muscle twitch APONEUROSIS
1. Lag Phase: or latent phase, is the time between General Principles
the application of a stimulus and the beginning
of contraction
● Most muscles extend from one bone to another
2. Contraction Phase: is the time during which
and cross at least one joint. At each end, the
the muscle contracts,
muscle is connected to the bone by a tendon.
3. Relaxation Phase: is the time during which
● Some broad, sheetlike tendons are called
the muscle relaxes.
aponeuroses
● A retinaculum (bracelet) is a band of
Muscle Tone connective tissue that holds down the tendons at
each wrist and ankle.
● Refers to constant tension produced by muscle - Muscle contraction causes most body
of the body over long periods of time. movements by pulling one of the bones
toward the other across the movable
❖ Fatigue: Decreased capacity to do work and joint.
reduced efficiency that normally follows a period ● Some muscles are not attached to bone at both
of activity. ends.
- Without fatigue, muscle fibers would be worked - For example, some facial muscles attach
to the point of structural damage to them and to the skin, which moves as the muscles
their supportive tissues. contract.
Types of Muscle Contraction Muscle attachment
● Isometric Contractions: amount of tension ● Muscles are attached to bones by tendons. The
increases during the contraction process, biceps brachii has two origins that originate on
but the length of the muscle does not change. the scapula. The triceps brachii has three origins
- Isometric contractions are responsible for that originate on the scapula and humerus. The
the constant length of the body’s postural biceps tendon inserts onto the radial tuberosity
muscles, such as the muscles of the back. and onto nearby connective tissue. The triceps
● Isotonic Contraction: amount of muscle brachii inserts onto the olecranon of the ulna.
tension is constant but the length of the muscle
decreases.
- Movements of the arms or fingers
FUNCTIONS OF THE MUSCULAR
SYSTEM
1. Movement of the body. Contraction of
skeletal muscles is responsible for the overall
movements of the body, such as walking,
running, and manipulating objects with the
hands.
2. Maintenance of posture. Skeletal muscles
constantly maintain tone, which keeps us sitting
or standing erect.
3. Respiration. Muscles of the thorax carry out
the movements necessary for respiration.
4. Production of body heat. When skeletal
muscles contract, heat is given off as a Muscle Fiber Structure
by-product. This released heat is critical to the
maintenance of body temperature. ● A muscle fiber is a single cylindrical fiber, with
5. Communication. Skeletal muscles are several nuclei located at its periphery. The
involved in all aspects of communication, largest human muscle fibers are up to 30 cm
including speaking, writing, typing, gesturing, long and 0.15 mm in diameter.
and facial expressions.
6. Constriction of organs and vessels. The
contraction of smooth muscle within the walls of
internal organs and vessels causes those
structures to constrict. This constriction can
help propel and mix food and water in the
digestive tract, propel secretions from organs,
and regulate blood flow through vessels.
7. Contraction of the heart. The contraction of
cardiac muscle causes the heart to beat,
propelling blood to all parts of the body.
, Characteristics of skeletal Muscle: ● Concentric Contraction: isotonic contraction
in which muscle tension increases as
muscle shortens.
● Constitute approximately 40% of body weight
- Many common movements are produced by
Striated muscle
concentric muscle contractions.
● Eccentric Contraction: are isotonic
Four major functional characteristics contraction in which tension is maintained as
muscle lengthen.
● Contractility: ability of skeletal muscle to - Eccentric contractions are used when a person
shorten with force slowly lowers a heavy weight.
● Excitability : capacity of skeletal muscle to - occurs in the hamstring muscles when a person
respond to a stimulus runs downhill.
● Extensibility: skeletal muscle can be stretched
● Elasticity: ability to recoil to their original Gross Anatomy
resting length after they have been stretched
Some muscle are attached to the bone
Muscle Twitch ● Facial muscles are attached to the skin
● Muscle is connected to a bone by a TENDON
● is the contraction of a muscle fiber in response ● Tendon: very short or almost non-existent
to a stimulus. - long, cable-like structure
- some are broad, sheetlike structures, called
Three Phases of Muscle twitch APONEUROSIS
1. Lag Phase: or latent phase, is the time between General Principles
the application of a stimulus and the beginning
of contraction
● Most muscles extend from one bone to another
2. Contraction Phase: is the time during which
and cross at least one joint. At each end, the
the muscle contracts,
muscle is connected to the bone by a tendon.
3. Relaxation Phase: is the time during which
● Some broad, sheetlike tendons are called
the muscle relaxes.
aponeuroses
● A retinaculum (bracelet) is a band of
Muscle Tone connective tissue that holds down the tendons at
each wrist and ankle.
● Refers to constant tension produced by muscle - Muscle contraction causes most body
of the body over long periods of time. movements by pulling one of the bones
toward the other across the movable
❖ Fatigue: Decreased capacity to do work and joint.
reduced efficiency that normally follows a period ● Some muscles are not attached to bone at both
of activity. ends.
- Without fatigue, muscle fibers would be worked - For example, some facial muscles attach
to the point of structural damage to them and to the skin, which moves as the muscles
their supportive tissues. contract.
Types of Muscle Contraction Muscle attachment
● Isometric Contractions: amount of tension ● Muscles are attached to bones by tendons. The
increases during the contraction process, biceps brachii has two origins that originate on
but the length of the muscle does not change. the scapula. The triceps brachii has three origins
- Isometric contractions are responsible for that originate on the scapula and humerus. The
the constant length of the body’s postural biceps tendon inserts onto the radial tuberosity
muscles, such as the muscles of the back. and onto nearby connective tissue. The triceps
● Isotonic Contraction: amount of muscle brachii inserts onto the olecranon of the ulna.
tension is constant but the length of the muscle
decreases.
- Movements of the arms or fingers
