Musculoskeletal System & Physical Activity

• The musculoskeletal system includes muscles and bones.

Effects of Physical Activity on Well-being:

• Physical activity and exercise can reduce depression.
• Lower anxiety can be achieved through exercise.
• Exercise improves negative moods.
• Sleep disorders can be improved through physical activity.
• Social relationships improve with physical activity and team sports.
• Interventions with physical activity are low cost.
• Chronic diseases are decreased through exercise.
• A heightened sense of identity is achieved with exercise.
• An increased sense of belongingness is achieved through physical activity.
• Life satisfaction is increased with exercise.
• Positive emotions are enhanced with exercise.
• Physical competence is built through physical activity.
• Socio-emotional skills are heightened through exercise.
• Improved self-efficacy is achieved with exercise.
• Self-confidence is increased with physical activity.

Functions of the Muscular System:

• Body movement is a key function performed by skeletal muscles.
• Skeletal muscles are responsible for the maintenance of posture.
• Respiration is a function performed by skeletal muscles.
• The production of body heat is done by skeletal muscles.
• Communication is achieved by skeletal muscles.
• The constriction of organs and vessels is performed by smooth muscle.
• The heartbeat is the function of cardiac muscle.

Skeletal Muscle Structure:

• Fascia is a term for connective tissue sheets.
• Epimysium is an overcoat of dense collagenous connective tissue surrounding the entire muscle.
• Perimysium is fibrous connective tissue that surrounds groups of muscle fibers, or fascicles.
• Endomysium is a fine sheath of connective tissue of reticular fibers around each muscle fiber.

Types of Muscles:

• Skeletal muscle consists of striated, tubular, and multinucleated fibers.
• Skeletal muscle is attached to the skeleton and is voluntary.
• Cardiac muscle consists of striated, branched, and uninucleated fibers.
• Cardiac muscle is found in the walls of the heart and is involuntary.
• Smooth muscle consists of spindle-shaped, nonstriated, and uninucleated fibers.
• Smooth muscle is located in the walls of hollow organs and blood vessels and is involuntary.

Muscle Contraction:

• Two Myofilaments interact during muscle contraction.
• Actin is one of the two types of Myofilaments.
• Myosin is one of the two types of Myofilaments.

Action Potential and Muscle Contraction:

• At rest, the inside of a cell is at -70 microvolts.
• With inputs to dendrites, the inside becomes more positive.
• Resting potential rises above threshold, an action potential starts down the axon.
• An action potential opens the cell membrane to allow sodium (Na+) in.
• The inside of the cell rapidly becomes more positive than the outside.
• Depolarization travels down the axon as the leading edge of the action potential.
• After depolarization, potassium (K+) moves out, restoring the inside to a negative voltage.
• Repolarization occurs when Potassium (K+) moves out, restoring the inside of the cell to a negative voltage.
• Rapid depolarization and repolarization produce a spike discharge pattern.
• Repolarization leads to a voltage below the resting potential, called hyperpolarization.
• Hyperpolarization means the neuron cannot produce a new action potential, known as the refractory period.

Disorders of the Muscular System:

• Duchenne's Muscular Dystrophy causes a progressive symmetrical wasting of skeletal muscles.
• Duchenne's Muscular Dystrophy is an X-linked recessive disorder.
• Muscles are replaced with fats and connective tissue deposits in Duchenne's Muscular Dystrophy.
• Duchenne's Muscular Dystrophy can be treated but not cured.
• Delay in walking, frequent falls, or intermittent calf pain are signs and symptoms of Duchenne's Muscular Dystrophy.
• Waddling gait by 3-4 years old and pronounced by 6 years old is a sign and symptom of Duchenne's Muscular Dystrophy.
• Lordosis or equinovarous foot position are signs and symptoms of Duchenne's Muscular Dystrophy.
• Tachycardia, or rapid muscle wasting, is a sign and symptom of Duchenne's Muscular Dystrophy disorder.
• Obesity is a sign and symptom of Duchenne's Muscular Dystrophy.
• A Child is wheelchair bound by 12 years old if they have Duchenne's Muscular Dystrophy.
• Treatment for Duchenne's Muscular Dystrophy is only supportive.
• Exercise, physical therapy, proper diet, and counseling are supportive treatments for Duchenne's Muscular Dystrophy.
• Myasthenia gravis is an autoimmune disorder.
• Myasthenia gravis impairs nerve impulse transmission.
• Progressive weakness is a sign and symptom of Myasthenia gravis.
• Abnormal fatigability exacerbated by exercise and repeated movement are present in Myasthenia gravis.
• Gradual progressive weakness are signs and symptoms of Myasthenia gravis.
• Fatigue, weak eye closure, Ptosis, Dipoplia, Difficulty in chewing are signs and symptoms of Myasthenia gravis.
• Dysphagia, Bobbing head, Hanging jaw, and weakened respiratory muscles are signs and symptoms of Myasthenia gravis.

Skeletal System:

• The skeletal system provides the framework and support for the body.
• The skeletal system allows movement.
• Protective vital organs is a component of skeletal system function.
• Promotes the synthesis of Vitamin D is a key function of the skeletal system.
• Storage of calcium and other minerals is achieved due to the skeletal system.
• Red blood cells are produced by the skeletal system.

Types of Cartilage:

• Cartilage is a solid and tough connective tissue.
• Hyaline cartilage is firm and flexible.
• Hyaline cartilage contains a generous supply of blood vessels.
• Hyaline cartilage is found at the ends of long bones, nose, ends of the ribs, larynx, and trachea.
• Fibrocartilage is stronger than hyaline cartilage.
• The matrix contains rows of thick collagen fibers in Fibrocartilage.
• Fibrocartilage is able to withstand tension and pressure.
• Fibrocartilage is located in the disks between the vertebrae and cartilage of the knee.
• Elastic Cartilage is more flexible than hyaline cartilage.
• Elastin fibers can be found in Elastic Cartilage.
• Elastic Cartilage is found in earlobes and epiglottis.

Bone Structure:

• The bones have a Diaphysis or shaft.
• The bones have an Epiphysis.
• The bones have a Spongy bone component.
• The bones have a Compact bone component.
• The bones have a Periosteum component.
• The bones have an Endosteum component.

Bone Anatomy:

• Long bones consist of a diaphysis and an epiphysis.
• A diaphysis is a tubular shaft that forms the axis of long bones.
• A diaphysis is composed of compact bone that surrounds the medullary cavity.
• Yellow bone marrow (fat) is contained in the medullary cavity.
• Epiphyses are the expanded ends of long bones.
• The exterior of an epiphysis is compact bone, and the interior is spongy bone.
• The joint surface of an epiphysis is covered with articular (hyaline) cartilage.
• The epiphyseal line separates the diaphysis from the epiphyses.
• The epiphyseal plate is the site of bone growth in length.
• The epiphyseal plate becomes the epiphyseal line when all of its cartilage is replaced with bone.
• Periosteum is the double layer of protective membrane covering the outer surface of bone.
• The outer fibrous layer of periosteum is dense regular connective tissue, which contains blood vessels and nerves.
• The inner osteogenic layer contains osteoblasts, osteoclasts, and osteochondral progenitor cells in periosteum.
• Endosteum is a delicate membrane covering internal surfaces of bone.
• Endosteum contains osteoblasts, osteoclasts, and osteochondral progenitor cells.

Types of Bone Cells:

• Osteoblasts are bone-forming cells.
• Osteocytes are mature bone cells.
• Osteoclasts are responsible for bone resorption.

Bone development:

• Bone development starts at week 8 of embryo development.
• Intramembranous ossification means bone develops from a fibrous membrane.
• Intramembranous ossification occurs in some skull bones, part of the mandible, and the diaphyses of the clavicles.
• Endochondral ossification means bone forms by replacing hyaline cartilage.
• Bones of the base of the skull, part of the mandible, the epiphyses of the clavicles, and most of the remaining skeletal system are related to Endochondral ossification.

Bone Repair steps:

• Hematoma formation is the first step in bone repair.
• Callus formation is the second step in bone repair.
• Callus ossification is the third step in bone repair.
• Bone remodeling is the fourth step in bone repair.

Skeletal Divisions:

• Axial skeletal division includes the Skull, Hyoid bone, Vertebral column, Rib cage, and Sternum.
• Appendicular skeletal division includes the pectoral girdle and upper limb, and pelvic girdle and lower limb.

Diseases of the Skeletal System:

• Scoliosis is a disease of the skeletal system.
• Osteoporosis is a disease of the skeletal system.