Muscular System Flashcards
There are three types of muscle tissue based on their structure and function. They include the following:
MUSCLE TISSUE TYPE CHARACTERISTIC EXAMPLE
Cardiac Muscle - Striated and involuntary Makes up the wall of the heart
Smooth Muscle - Smooth and involuntary Found in other organs such as
those of the digestive system
Skeletal Muscle
(most common muscle tissue in the
human body):
Striated, voluntary, and fatigue easily Attaches to bone, responsible for
all movement
- Skeletal muscle structure
► Sarcomere: the contractile unit of muscle tissue
► Z line: the lateral boundary of the sarcomere where the myolament actin attaches
► Sarcoplasm: the cytoplasm of a muscle ber (unique to muscle cells)
► Glycogen: the stored form of glucose found in the liver and muscles
► Myobrils: parallel laments that form muscle
► Myolaments: the laments of myobrils composed of actin and myosin
► Actin: the thin laments of muscle myolaments where myosin binds to generate muscle contraction
► Myosin: the thick laments of myolaments with a brous head, neck, and tail that binds to actin
► Endomysium: the connective tissue covering each muscle ber
► Epimysium: brous elastic tissue that surrounds a muscle
► Fasciculi: bundles of muscle bers; the singular is “fascicle”
► Perimysium: the connective tissue that covers a bundle of muscle bers
► Tendon: a strong brous connective tissue that attaches muscle to bone
► Periosteum: a dense layer of vascular connective tissue enveloping the bones except at the surfaces of the joints
- Skeletal muscle contraction
► Must receive a signal from the CNS
► Neuromuscular junction: the space between a motor neuron and muscle ber
► Neurotransmitter: a chemical messenger that transmits messages between neurons or from neurons to muscles
► Acetylcholine: the neurotransmitter (unique to the motor neuron) released by an action potential at the
neuromuscular junction
► Sliding- lament theory: the interaction of actin and myosin that describes the process of muscle contraction
Muscles are made up of sarcomeres—a contractile unit of a myofibril (muscle fiber).
The myofibrils have overlapping strands of protein polymers called actin (thin laments) and myosin
(thick filaments).
An electrical trigger stimulates the release of calcium, which binds to actin.
This then allows the interaction with the other contractile protein, myosin.
The myosin can now pull on the actin to begin shortening the muscle.
This series of interactions, the myosin pulling across the actin, is what causes shortening in the
muscle and ultimately a muscle contraction.
1 Brain sends out electrical signal
2 Signal travels through the spinal cord
3 To the spinal nerves
4 To the motor neurons
5 Resulting in the propagation of an electrical
current through the muscle ber
6 Electrical signal triggers the release of calcium
inside the muscle ber
7 The released calcium binds to the contractile
protein ACTIN
8 This permits its interaction with the MYOSIN
contractile protein
9 ATP provides the energy that permits the “walking”
of MYOSIN across the ACTIN
10 This pulling action of the MYOSIN across the
ACTIN results in the shortening of the muscle
fiber during MUSCLE CONTRACTION.
- Size principle of ber recruitment (also called Henneman’s size principle):
principle stating that motor units are
recruited in order according to their recruitment thresholds and firing rates
► In other words, motor units will be recruited in order from smallest and slowest firing rate to largest and
fastest firing rate.
- Types of muscle fibers
► As a trainer, it’s also important to understand the types of muscle fibers as they have different needs,
capabilities, and purposes within the human body.
There are two main types of skeletal muscle fibers:
– Type I: slow-twitch fibers and aerobic (good for endurance)
– Type II: fast-twitch and anaerobic (good for power)
* Type IIa fibers : fast-twitch, moderately fatigable muscle fibers with moderate
mitochondrial density
* Type IIx fibers : fast-twitch, fast-fatigable muscle fibers with low mitochondrial density
(white in color)
Mitochondria (singular “mitochondrion”): an organelle with a double membrane
and many folds inside responsible for generating the chemical energy needed for
biochemical reactions; the “powerhouse of the cell”
- Muscles as movers
► Muscles create movement by pulling on bones within the body. Muscles connect to bones, via tendons, at the origin and insertion.
Origin: the proximal (closer to the midline of the body) attachment
Insertion: the distal (farther from the midline) attachment
Action: the specic movements that each muscle is responsible for
Innervation: the specic distribution of nerves to a particular part of the body
- Muscle fiber arrangement (or the directions in which muscles run) will help tness professionals learn how the
muscles pull on the skeletal system to produce movement.
► Fusiform muscle: spindle-shaped muscle
Example: Biceps brachii
► Convergent muscle (triangular muscle): muscle fiber converging from a broad origin (xed point where the
muscle attaches closest to the torso) to a single tendon of insertion (xed point where the muscle attaches
farthest from the torso)
Example: Pectoralis
► Circular muscle: muscle fiber surrounding an opening in the body
► Parallel muscle: muscle fiber running parallel to the axis of the muscle
Example: Stylohyoid
► Pennate muscle: muscles with fasciculi that attach obliquely (diagonally)
► Unipennate muscle: muscle fiber extending from one side of a central tendon
Example: Flexor pollicis longus
► Bipennate muscle: muscle fiber extending from both sides of a central tendon
Example: Soleus
► Multipennate muscle: muscle fiber extending from both sides of multiple central tendons
Example: Deltoid
- A muscle produces three different types of actions:
► Concentric: muscles that shorten to produce movement. For example, during the pressing motion of a bench
press, the pectoralis is concentrically contracting.
► Eccentric: muscles that lengthen to allow movement. For example, during the downward motion of a biceps
curl, the biceps brachii is eccentrically contracting. When applying tempo training, this is the part of the
movement that should be the focus and, therefore, the slowest portion of the repetition.
► Isometric: muscles where the joint angle and muscle length do not change during movement. For example,
the entire body works to maintain a stable position when performing a plank.
- Muscles typically work together in groups:
CLASSIFICATION RESPONSIBILITY OF MUSCLE TYPE EXAMPLE
Agonist Main muscle responsible for movement;
prime mover Biceps brachii during a biceps curl
Synergist Muscle that plays a secondary role in
movement Brachioradialis during a biceps curl
Antagonist Muscle with an action directly opposite of
the agonist Triceps during a biceps curl
All-or-none principle:
The amplitude—or strength—of a nerve’s action potential is independent of the
strength—or magnitude—of the stimulus.
Stretch-shortening cycle (SSC):
the cycling between the eccentric (stretch) action of a muscle and the
concentric (shortening) action of the same muscle
Three (3) phases:
– Eccentric, Amortization, Concentric
