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Muscular, Karina Salazar, Per.2 - Coggle Diagram
Muscular, Karina Salazar, Per.2
Major functions of the muscular system
Skeletal muscle
Skeletal muscles are the only muscles that can be consciously controlled. They are attached to bones, and contracting the muscles causes movement of those bones.
Any action that a person consciously undertakes involves the use of skeletal muscles
Smooth Muscle
Smooth muscle lines the inside of blood vessels and organs, such as the stomach
It is the weakest type of muscle but has an essential role in moving food along the digestive tract and maintaining blood circulation through the blood vessels.
Smooth muscle acts involuntarily and cannot be consciously controlled.
Cardiac muscle
Located only in the heart, cardiac muscle pumps blood around the body. Cardiac muscle stimulates its own contractions that form our heartbeat. Signals from the nervous system control the rate of contraction. This type of muscle is strong and acts involuntarily.
Functions;Mobility, Stability, Posture, Circulation, Respiration, Digestion, Urination, Childbirth, vision, organ protection, Temperature regulation
3 types of muscles & their functions
Skeletal (Skeletal muscle)
Movement of bones at joints, maintenance of posture
Contracts and relaxes rapidly when stimulated by a motor neuron
Smooth (found in Walls of hollow viscera, blood vessels)
Movement of viscera, peristalsis, vasoconstriction
Contracts and relaxes slowly; single unit type is self-exciting(involuntary) ; rhythmic
Cardiac (only found in the heart)
involuntary contraction and relaxation of the cardiac muscle are vital for pumping blood throughout the cardiovascular system. To accomplish this, the structure of cardiac muscle has distinct features that allow it to contract in a coordinated fashion and resist fatigue
Complex membrane junctions, called intercalated discs, join cells and transmit the force of contraction from one cell to the next
Names of all the skeletal muscles
Pectoralis major
: named for size and location; large size, located in chest
Deltoid
: named for shape; shaped like a triangle
Extensor digitorum
: named for action; extends digits (fingers, toes)
Biceps brachii
: named for number of attachments and location; has 2 origins/heads, and is found in the arm (brachium)
Sternocleidomastoid
: named for attachments; attaches to sternum, clavicle, and mastoid process
External oblique
: named for location and direction of fibers; located near outside of body, and fibers run at a slant
Sarcomere
(are many units made up of myofibrils, Joined end-to-end)
A
sarcomere
extends from one
Z line
to the next
I bands (light bands)
are made up of actin filaments, which are anchored to the Z lines
A bands (dark bands)
are made up of overlapping thick and thin filaments
In the center of the A band is the
H zone
, which consists of myosin filaments only
The M line, in the center of the
H zone
, consists of proteins that hold the myosin filaments in place
Neuromuscular junction
(a synapse between a motor neuron and a muscle fiber that it regulates)
Skeletal muscle fibers contract only when stimulated by a
motor neuron
Each skeletal muscle fiber (cell) is functionally (not physically) connected to the axon of a motor neuron, creating a
synapse
The neuron communicates with the muscle fiber by way of chemicals called
neurotransmitters
, which are released at the synapse
The cytoplasm of the distal end of the motor neuron contains numerous
mitochondria
and
synaptic vesicles
storing neurotransmitters
The muscle fiber membrane in this area contains a specialized region called the
motor end plate
, in which the sarcolemma is tightly folded
When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitter into the
synaptic cleft
, the gap between the membranes of the neuron and muscle fiber
The neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract
Sliding filament theory of muscle contraction
The sliding filament theory explains muscle contraction based on how muscle fibers (actin and myosin) slide against each other to generate tension in the overall muscle
Step 1.)
A muscle contraction starts in the brain, where signals are sent along the motor neuron. Within the motor neuron are vesicles that contain the neurotransmitter, acetylcholine. Acetylcholine reaches the receptors on the muscle sarcolemma which causes an impulse.
Step 2.)
The impulse travels down the membrane and into the transverse tubules where it causes calcium to be released from the sarcoplasmic reticulum. The sarcoplasmic reticulum is only partially pictured.
Step 3.)
Calcium binds to a structure on the actin that causes it to change shape
Step 4.)
The change in shape alliows myosin heads to form cross-bridges between the actin and the myosin
Step 5.)
Energy from ATP is used to create a "power stroke" between the two filaments. The actin filament then slides inward and shortens, or contracts the whole muscle
Action potential in a muscle fiber
An action potential is a special type of electrical signal that can travel along a cell membrane as a wave
This allows a signal to be transmitted quickly and faithfully over long distances
Muscle coverings
Each muscle is wrapped in a sheath of dense, irregular connective tissue called the
epimysium
allows a muscle to contract and move powerfully while maintaining its structural integrity
separates muscle from other tissues and organs in the area, allowing the muscle to move independently.
Inside each skeletal muscle, muscle fibers are organized into individual bundles, each called a fascicle, by a middle layer of connective tissue called the
perimysium
it allows the nervous system to trigger a specific movement of a muscle by activating a subset of muscle fibers within a bundle, or fascicle of the muscle
Each muscle fiber is encased in a thin connective tissue layer of collagen and reticular fibers called the
endomysium
The endomysium contains the extracellular fluid and nutrients to support the muscle fiber. These nutrients are supplied via blood to the muscle tissue