MUSCULAR SYSTEM. Kaitlyn Skidmore Qua’Shaya Hammon Camille Torres. The Functions of the Muscular System. The Muscular System : Provides Structure Aids in Movement Production of Heat Stability of Joints. SKELETAL MUSCLE STRUCTURE. MUSCLE FIBER STRUCTURE.
The Muscular System:
Neuromuscular junction- Connection between the motor neuron and the muscle fiber
Motor End Plate-The flattened end of a motor neuron that transmits neural impulses to a muscle
Neurotransmitter- Cytoplasm at the distal ends of these motor neuron axons; rich in mitochondria and contains many tiny vesicles that stores chemicals.
Muscle Contraction- A complex interaction of organelles and molecules in which myosin binds to actin and exerts pulling action.
A protein involved in cell movement: a protein present in all cells and in muscle tissue where it plays a role in contraction.
A muscle protein: a protein in muscles that helps them contract when connected with the protein actin.
The process of contraction begins with:
The stimulation of a motor neuron, which releases
acetylcholine, causing the chemical, calcium (Ca++) to be
This calcium molecule will shift a troponin, making a site
available for the myosin heads to connect to the actin
molecule creating the contraction.
Once the myosin filament attaches to the actin, ATP releases
the bond between the two, then a chemical,
acetylcholinesterase, is released to digest the acetylcholine,
so that it may be recycled and used once again for
Muscle Fatigue: a muscle exercised strenuously for a prolonged period may lose its ability to contract.
A protein, calmodulin binds to calcium ions (no troponin) and activates the contraction mechanism.
Most calcium diffuses in to smooth muscle cells from the extracellular fluid (reduced SR).
Norepinephrine and acetylcholine are smooth muscle neurotransmitters.
4. Contraction is slow and sustained.
Origin is the attachment site of the muscle’s tendon to a more stationary bone. It has very less movement and normally a muscle contracts towards it. Some muscles have more than one origin, for example, biceps brachii.
Insertion is the attachment site of the muscle’s tendon to a more movable bone is known as the muscle’s insertion. It has the greatest motion when the muscle contracts and it tends to be more distal.
An antagonist muscle is one that works in opposition to the movement initiated by an agonist muscle. The antagonist muscle in a muscle set brings a limb or other anatomical part back to its initial position of rest.
A synergist muscle is a muscle which works in concert with another muscle to generate movement. These muscles can work with the agonists or prime movers which surround a joint, or the antagonistic muscles, which move in the opposite direction.
Muscular dystrophies, or MD, are a group of inherited conditions, which means they are passed down through families. They may occur in childhood or adulthood.
The doctor's exam may show:
•Abnormally curved spine (scoliosis)
•Joint contractures (clubfoot, clawhand, or others)
•Low muscle tone (hypotonia)
•Heart testing - electrocardiography (ECG)
•Nerve testing - electromyography (EMG)
•Blood testing - including CPK level
•Genetic testing for some forms of muscular dystrophy
There are no known cures for the various muscular dystrophies. The goal of treatment is to control symptoms
Summation- Occurs in the neuromuscular junction; it is the additive effect of several electrical impulses.
Recruitment- contraction of one motor unit and all muscle fibers at the same time
Sustained contraction- also called a tetanic contraction, occurs when there is an accumulation of acetylcholine in the neuromuscular junction.
-It occurs rapidly, giving no time for the muscle to relax between stimuli
-Remains constant in a steady state; maximal muscle contraction
Muscle Tone- continuous and partial contraction of muscles
-recruitment and summation combined