Module 5 - Muscular System
The muscular system and the skeletal system work together to provide movement
for the human body. Muscle tissue is found in
... [Show More] three distinct types in the body;
skeletal, smooth, and cardiac. Skeletal muscles must have a blood and nervous
supply to provide movement. Skeletal muscles are under conscious control,
meaning that a person can consciously decide to use these muscles to complete
an action. Communication within the body to coordinate movement starts in the
brain with a message that is sent through the spinal cord and eventually attaches
to a muscle. Peripheral nerves carry the signal from the central nervous
system (brain and spinal cord) to a specific muscle destination to provide
movement. Messages from the central nervous system to a muscle are
called motor actions. Nerves also carry information from the external environment
to the central nervous system, called sensation or sensory input (Fig 5.1, 5.2).
Spinal nerves combine to form complex networks of peripheral nerves throughout
body.
Figure 5.1 Posterior view of the nervous
system. The brain and spinal cord (central
nervous system) connect to the peripheral
nervous system. Examples of peripheral
nerves are spinal nerves (cervical, thoracic,
lumbar), the upper trunk of the brachial
plexus, and radial nerve.
Figure 5.2 Peripheral nerves carry the
communication from the central nervous
system (brain and spinal cord) to the muscle.
Peripheral nerves also carry information from
the environment to the central nervous
system.
Module 5 - Muscular System
Tendons are connective tissues that connect skeletal muscle to bone at each end.
Tendons are flexible, can bend at the joints, and help cushion against sudden
movement. Ligaments are connective tissue that connects bone to bone, helping
to stabilize joints where bones meet.
Figure 5.3 Skeletal muscles attach to
bones via tendons at points called the
origin and insertion. The origin is the
fixed point while the insertion is the
place that is moved during a muscle
contraction.
All skeletal muscles have an origin, insertion, and action. The origin is the bony
site of attachment that is stationary during the movement. The insertion of a
muscle is the bony site of attachment that is moved by the muscle contraction
(see Figure 5.3).
The origin and insertion can be reversed in different types of movement. For this
module, standard origin and insertion points are referenced from anatomical
position.
The action of the muscle is what effect is produced by the muscle’s contraction.
For example, the triceps are the primary extensor of the forearms.
The innervation is the peripheral nerve that supplies a muscle with the message
from the brain. For example, the innervation of the biceps brachii is the
musculocutaneous nerve (see Figure 5.4).
Module 5 - Muscular System
Figure 5.4 Anterior view of the musculocutaneous nerve (blue) innervates the
biceps brachii.
Muscles are generally studied in groups. The following muscle list is an overview of
some of the major muscles in the body. Study the location of the muscle in the
body. In addition, if listed, study the origin, insertion, innervation and action of
these muscles.
Muscles of Facial Expression
The muscles in this grouping help to facilitate all the actions within the face. All the
varied facial expressions are enabled by these muscles. CN is an abbreviation for
cranial nerve. There are twelve pairs of cranial nerves that originate on the ventral
surface of the brain, controlling muscles and functions of several organs and
glands.
Orbicularis oculi
Action: eye closure
Innervation: facial nerve (CN VII) [Show Less]