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The Muscular System By: Lydia Alpizar Emily Blazak Stephanie Checchio Chris Kinney Muscular System Overview There are over 630 muscles in the human body. They account for about 40% of body weight. Muscles can’t push, they pull. Skeletal muscles with bones to form the musculoskeletal system. Muscle is attached to end of bone by tendon, stretches across a joint, and attached to another bone. Functions of Muscles Motion- fine and gross muscles movement, involuntary muscle movement Maintenance of Posture- keeping the body in an upright position Heat Production- the metabolism that occurs is essential for maintenance of body temperature Characteristics of Muscles Excitability - responds to stimuli Contractility - able to shorten in length Extensibility - stretches when pulled Elasticity - tends to return to original shape & length after contraction or extension Types of Muscles: Skeletal Skeletal Voluntary, only move in response to central nervous system Striated Attached to bones by tendons Controlled by Somatic Nervous System Human skeleton muscle Functions of Skeletal Muscles Most abundant tissue in the body Controls fine and gross motor skills Ex. Walking, writing, swimming, cutting with scissors Types of Muscles Flexor - decreases the angle at a joint Extensor - increases the angle at a joint Abductor - moves a bone away from the midline Adductor - moves a bone closer to the midline Levator - produces an upward movement Depressor - produces a downward movement Supinator - turns the palm upward or anteriorly Pronator - turns the palm downward Sphincter - decreases the size of an opening Tensor - makes a body part more rigid Rotator - moves a bone around its longitudinal axis Types of Muscles: Visceral Visceral Involuntary Smooth (not striated) Controlled by Autonomic Nervous System Smooth muscle, uterus Functions of Visceral Muscles Located in walls of hollow organs to move particles Muscles contract and relax to push particles along Ex. Small blood vessels, digestive tract, urinary system, and reproductive system. Types of Muscles: Cardiac Cross between striated an involuntary muscle Moves in spiraled motion to pump more blood through Controlled by autonomic nervous system Cardiac Muscles Functions of Cardiac Muscles Plays the most important role in contraction of the atria and ventricles of heart Causes rhythmical beating of the heart which circulates the blood Types of Muscle Cells Cardiac: striated bands, contain one nucleus Skeletal: striated bands, multiple nuclei Smooth: thin elongated cells, also contain one nucleus How A Muscle Contracts 1. Nervous system sends signal from the brain to muscle nerves in order to begin the contraction. 2. During muscle use, calcium channels open up and attaches to troponin protein, which is found between the actin filaments 3. Myosin protein moves along the actin to create “friction” and the overall contraction of the muscle. 4. ATP attaches to myosin head, breaking the bond between myosin and actin, ending the contraction. 5. Once there is no more calcium present, troponin acts as a barrier between myosin and actin to prevent any further contractions. How A Muscle Contracts Important components of a muscle contraction: •Actin – muscle protein •Myosin – another muscle protein •Troponin – another muscle protein •Calcium – important ion •ATP – energy molecule How A Muscle Contracts Muscle Animation All-or-Nothing Principle There is a certain activation energy that acts as a catalyst for muscle movement. If the energy is below a certain threshold nothing will happen; if it’s above that threshold and the stimulus will activate. Regardless of how much the energy exceeds the specific threshold, nothing more will happen and the strength of the movement will be no greater or no less. Tetany Occurs when there is a depleted level of calcium and other high energy phosphates, mostly ATP Best described as involuntary muscle convulsions Example, hyperventilating, overbreathing Fatigue Occurs when the body cannot exert a normal amount of force or requires extra effort to reach a certain force Causes can range from fatigue to severe disease Physical disease is product of extreme physical activity If untreated this disease can cause heart issue and paralysis Muscular Dystrophy A group of disorders that involve muscle weakness and a loss of muscle tissues that worsens over time. MD is genetic. The genes cannot make the proteins that are necessary for muscles to properly function Symptoms: muscle weakness that slowly gets worse delayed development of muscle motor skills difficulty using one or more muscle groups eyelid drooping difficulty walking Physical exam and medical history will help doctors diagnose type of muscular dystrophy. Breathing exercises, physical therapy, and medications like steroids help people with MD. There is currently no cure. Periodic Paralysis A group of rare genetic diseases that lead to weakness or paralysis. Caused by irregular level of potassium in the blood Symptoms: Muscles respond irregularly to stimulation Weakness in limbs Diagnosed by doctor by symptoms and blood test that checks the potassium levels in the blood Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease) Disease effecting motor neurons in the brain and spinal cord that control voluntary muscle movement. These neurons in the brain and spinal cord shrink and disappear causing muscles to no longer receive signals from the brain. 10% of cases are genetic, 90% are sporadic. Symptoms: Weakness Cramps Muscles twitches Dropping things Having difficulty speaking Doctors diagnose ALS by tests such as electromyogram, MRIs, spinal tap, or muscle and nerve biopsies. ALS inevitably leads to loss of control in voluntary muscles. The survival rate is 3 to 5 years on average.
