MUSCULAR SYSTEM

FUNCTIONS
• It produces body movement • Performs movement involved in communication
It is responsible for all the movements of our body, It is involved in all aspect of communication like
walking, running and manipulating objects with the speaking, writing, typing, gesturing and facial
hands expressions
• Maintains posture • Constricts organs and vessels
Skeletal muscles constantly maintain tone which keeps The contraction of smooth muscles leads to
us sitting or standing erect constriction and can help propel and mix food in the
• Causes respiration digestive tract, propel secretions from organs and
Muscles of the thorax carry out breathing movements regulate blood flow through vessels
• Produces body heat • Pumps blood
When there is muscle contraction, heat is given off as Contraction of cardiac muscles pumps out blood from
byproduct and is responsible for the maintenance of the heart and is distributed in all parts of the body
body temperature

GENERAL PROPERTIES ON MUSCLE TISSUE

• CONTRACTILITY is the ability of the muscle to fiber contracts spontaneously but also receive
shorten forcefully or contract. Skeletal muscles involuntary signals to modulate force or rate of
cause the structures to where they are attached to contractions. (neural and hormonal)
move. Smooth and Cardiac muscles increase • EXTENSIBILITY means that the muscles can be
pressure inside the organ that surrounds it such as stretched beyond its normal resting length and still
digestive and cardiovascular system be able to contract
• EXCITABILITY is the capacity of the muscle to • ELASTICITY is the ability of the muscle to recoil to its
respond to a stimulus to contract is from nerves that original resting length after it has been stretched
we consciously control. Smooth and cardiac muscle

(striated muscle)

40% of body
weight

SKELETAL MUSCLE STRUCTURE

Actin myofilaments, or thin filaments, are made up of three components: actin, troponin, and tropomyosin. The actin
strands have attachment sites for the myosin myofilaments. They resemble two-minute strands of pearls twisted together,
Troponin molecules have binding sites for Ca2+. Troponin is attached at specific intervals along the actin myofilaments.
Tropomyosin filaments block the myosin myofilament binding sites on the actin myofilaments.

EXCITABILITY OF MUSCLE FIBERS

NERVE SUPPLY & MUSCLE FIBER STIMULATION

• Skeletal muscle fibers do not

contract unless they are stimulated by
motor neurons which are specialized
nerve cells that stimulate muscle to
contract.
• Each branch forms a junction
with a muscle fiber called your
neuromuscular junction. A more
general term, SYNAPSE, refers to the
cell to cell junction between a nerve
cell and either another nerve cell.
MUSCLE CONTRACTION

ENERGY REAUIREMENT FOR MUSCLE CONTRACTION

(1) Muscle fibers are very energy demanding cells whether at rest or during any form of exercise. This energy comes from
either aerobic or anaerobic ATP production. (2) Aerobic respiration usually occurs in mitochondria and requires oxygen
and breaks down glucose to produce ATP, CO2 and H2O. These also can process lipids and amino acids to make ATP. (3)
Anaerobic do not require oxygen breaks down glucose to produce ATP and lactate
ATP IS DERVIVED FROM FOUR PROCESSES IN THE SKELETAL MUSCLE

FATIGUE

ENERGY REAUIREMENT FOR MUSCLE CONTRACTION

• Muscles contract either isometrically or isotonically
ISOMETRICALLY meaning tension increases, but muscle length stays the same
ISOTONICALLY tension remains the same, but the muscle length decreases
• MUSCLE TONE consists of a small percentage of muscle fibers contracting tetanically and is responsible for posture
• It contains a combination of slow twitch and fast twitch fibers
Slow twitch fibers are better suited for aerobic respiration and fast twitch fibers are adapted for anaerobic
respiration
• SPRINTERS have more fast twitch fibers whereas DISTANCE RUNNERS have more fast twitch fibers

SMOOTH AND CARDIAC MUSCLES

SKELETAL MUSCLES TERMINOLOGIES
• Tendons - connects the muscle to the bone
Muscle contraction causes most body movements by pulling one of the bones toward the other across the
movable joint. However, not all muscles are attached to bone at both ends.
• Aponeuroses - broad, sheet-like tendons
• Retinaculum -band of connective tissue that holds down the tendons at each wrist and ankle
• Origin - most stationary, or fixed, end of the muscle; usually, but not always, proximal or medial to the insertion
of a given muscle that is movable
• Insertion - end of the muscle attached to the bone undergoing the greatest movement
• Belly – part of the muscle between the origin and the insertion
• Action - specific body movement a muscle contraction causes

STUDY OF MUSCLES IN GROUPS

The action of a single muscle or
group of muscles (agonist) is
opposed by that of another
muscle or group of muscles
(antagonist).

SYNERGISTS
- Members of a group of muscles working together to produce a movement are called

PRIME MOVER
- one muscle plays the major role in accomplishing the desired movement

FIXATORS
- muscles that hold one bone in place relative to the body while a usually more distal bone is moved.

NAME OF A SPECIFIC MUSCLE IS BASED ON AT LEAST SEVEN CHARACTERISTICS

1. LOCATION. A pectoralis muscle is located in the chest, a gluteus muscle is in the buttock, and a brachial
muscle is in the arm.
2. SIZE. The gluteus maximus is the largest muscle of the buttock, and the gluteus minimus (small) is the
smallest. A longus (long) muscle is longer than a brevis (short) muscle.
3. SHAPE. The deltoid muscle is triangular in shape, a quadratus muscle is rectangular, and a teres muscle is
round.
4. ORIENTATION OF FASCICLES. A rectus muscle has muscle fascicles running in the same direction as the
structure with which the muscle is associated, whereas the fascicles of an oblique muscle lie at an angle to
the length of the structure.
5. ORIGIN AND INSERTION. The sternocleidomastoid has its origin on the sternum and clavicle and its insertion
on the mastoid process of the temporal bone. The brachioradialis originates in the arm (brachium) and
inserts onto the radius.
6. NUMBER OF HEADS. A biceps muscle has two heads (origins), and a triceps muscle has three heads (origins).
7. FUNCTION. Recall from chapter 6 that body movements have names, for example, abduction and adduction.
Abductors and adductors are the muscles that cause that type of movement. Abduction moves a structure
away from the midline, and adduction moves a structure toward the midline
FACIAL EXPRESSION
In humans, facial expressions are important components of nonverbal communication. Several mucles act to move the
skin around the eyes and eyebrows
MUSCLES INVOLVED
• Occipitofrontalis • Zygomaticus
• Orbicularis oculi • Levator labii superioris
• Orbicularis oris • Depressor anguli oris
• Buccinator
Together these muscles are sometimes called the kissing muscles because they pucker the mouth.
The BUCCINATOR also flattens the cheeks as in whistling or blowing a trumpet and is therefore sometimes called the
trumpeter’s muscle.

MASTICATION
The four pairs of muscles for chewing, or mastication are some of the strongest muscles in the body.
MUSCLES INVOLVED
• Temporalis • Lateral pterygoid
• Masseter • Medial pterygoid

TONGUE AND SWALLOWING

The TONGUE is very important in mastication and speech. It moves food around in the mouth and, with the buccinator
muscle, holds the food in place while the teeth grind the food.
MUSCLES INVOLVED
• Intrinsic Tongue muscles - located entirely within • Pharyngeal muscles
the tongue and change its shape
✓ Elevators
• Extrinsic Tongue muscles - located outside the
tongue but are attached to and move the tongue ✓ Constrictors
• Hyoid muscles
✓ Superior
✓ Suprahyoid
✓ Middle
✓ Infrahyoid
✓ Inferior
• Soft palate muscles

SWALLOWING involves a number of structures and their associated muscles, including the hyoid muscles, soft palate,
pharynx (throat), and larynx (voicebox).
 THORAX

The muscles of the thorax are involved almost entirely in the process of breathing.
• external intercostals elevate the ribs during inspiration.
• internal intercostals depress the ribs during forced expiration.

SUPINATION AND PRONATION

• SUPINATION of the forearm, or turning the flexed forearm so that the palm is up, is accomplished by the
SUPINATOR
• PRONATION turning the forearm so that the palm is down, is a function of two PRONATOR

THIGH

The muscles of the lower limb include those located in the hip, the thigh, the leg, and the foot.
Several hip muscles originate on the hip bone and insert onto the femur.

• anterior thigh muscles

– flex the hip
• posterior thigh muscles
– extend the hip
• the medial thigh muscles
– adduct the thigh.
Many of the age-related changes in skeletal muscle can be slowed dramatically if people remain physically
active. As people age, they often assume a sedentary lifestyle. Studies show that elderly people who are
sedentary can become stronger and more mobile in response to exercise
AGING is associated with decreased muscle mass, slower reaction time, reduced stamina, and increased
recovery time.