Basic Skeletal Muscle Anatomy & Physiology PDF

Click icon to add picture Basic Skeletal Muscle Anatomy & Physiology Fun facts There are more than 600 muscles in the human body Biggest muscle: gluteus maximus Smallest muscles found in the inner ear Strongest muscle: masseter The tongue is the only muscle attached at only one end but...

Click icon to add picture Basic Skeletal Muscle Anatomy & Physiology Fun facts There are more than 600 muscles in the human body Biggest muscle: gluteus maximus Smallest muscles found in the inner ear Strongest muscle: masseter The tongue is the only muscle attached at only one end but not the other Accounts for roughly 40% of the body weight Muscles cannot push, they can only pull Functions of skeletal muscle system Works with skeletal system to provide movement Takes part in the body’s posture and positioning (holds it upright) Supports soft tissue (where soft tissue – tissue that support/connect/surround organs) Guards the body’s entrances and exits (mough, throat, spincters, etc.) Produces heat for thermoregulartion Introduction to skeletal muscle anatomy Muscles are made of several layers of tissue working together to allow movement Levels of organization Tendons – tissue that connect muscle to bone Levels of organization Muscle fascicle – a bundle of muscle fibers (s. muscle cells) -allows flexibility and distribution of force *look at cross section – identify difference Levels of organization Muscle fibers- individual skeletal muscle cells responsible for contraction. Structure: ◦Long, cylindrical cells ◦Multinucleated ◦Contains myofibrils made of actin and Levels of organization Myofibril – organelle inside muscle fibers responsible for contracting Recap: levels of organization (Tendon) + Muscles  fascicles  muscle fiber  myofibril *Tendons are not part of the muscle cell. They are a connective tissue that attaches muscle to bone Click icon to add picture SKELETAL MUSCLE PHYSIOLOGY – INSIDE THE MYOFIBRIL Myofibril  sarcomere Sarcomeres make up myofibrils. ◦Basic contractile units of striated muscle cells Anatomy of a Sarcomere Actin: thin filament Myosin: thick filament Z lines: boundary of each sarcomere M line: (middle) connects the myosin Anatomy of a Sarcomere -Contraction occurs when myosin pull actin towards the M line (middle). -Z lines get closer together. *view gif in slideshow mode to make it make sense. Sliding Filament Theory inside the sarcomere) Muscle contraction occurs as actin filaments slide past myosin filaments within the sarcomere. The Z-lines are pulled closer together, shortening the sarcomere and contracting the muscle. Steps of the sliding filament theory 1. Myosin head attaches to actin filaments 2. Myosin heads pivot, pulling actin towards center of the sarcomere (M line) 3. ATP (energy molecule) binds to myosin, causing it to detach from actin 4. ATP hydrolyzed (in layman terms, used up), resetting myosin head for next cycle *view in slideshow mode to see gif movement. This will help make it make sense. Just for fun: This is what happiness really looks like: Molecules of the protein myosin drag a ball of endorphins along an active filament into the inner part of the brain's parietal cortex, which produces feelings of happiness. *EDIT - fact check/fake news: more likely motor protein kinesin, which is similar to myosin but transports longer distances Nervous system control of Muscle Contraction Brain  spinal cord muscle cell ◦ neurons carry messages from brain to muscles via spinal cord Signal travels to muscle cell at the neuromuscular junction ◦ Release of neurotransmitter Acetylcholine (Ach) which triggers muscle contraction Zoom in of Ach released from the neuron into muscle fiber, triggering contraction.