Muscles support the soft tissues and control movement, body position, body temperature, and entrances and exits to parts of the body (mouth, esophagus, stomach, etc.). There are three types of cells or fibers: skeletal (striated and under voluntary control), smooth (not striated, involuntary), and cardiac (involuntary). Skeletal muscles contain fascia (outer casing), epimysium (connective tissue), fascicles, perimysium, muscle fibers, endomysium, myofibrils, and sarcomeres. One theory of muscle movement suggests that a neurotransmitter causes the muscle to release calcium, triggering a power stroke as myosin filaments bond to actin binding sites over and over, powered by ATP. This lecture also covers oxygen debt, lactic acid, fast and slow twitch fibers, and the four characteristics of major muscles: function, location, size, and orientation as well as muscle disorders.
The function of muscles includes movement, maintaining body position, support of soft tissues, regulating entrances and exits of the body, and maintaining body temperature
The 3 types of muscle cells (tissues) includes skeletal (striated), smooth, and cardiac muscle
Skeletal muscle anatomy involves these terms: fascia, epimysium, fascicles, perimysium, muscle fibers, endomysium, myofibrils, and sarcomeres
Sarcomeres are made of groups of myosin, actin, troponin, and tropomyosin
The Sliding Filament Theory describes how myosin (thick) filaments move actin (thin) filaments closer together to contract a myofibril
Acetylcholine, ATP and Calcium are involved in contracting a muscle
Acetylcholinesterase and ATP are needed to relax a muscle
Lactic acid forms in muscle tissue when not enough oxygen is available for the energy demands of that tissue
Creatine phosphate helps quickly regenerate ATP in a muscle fiber
Fast (white) and slow (red) twitch muscle fibers are found in the human body
Muscle names in the body are coined by some combination of their function, location, size, and/or orientation
Muscles of the head and face include the epicranius, zygomaticus, buccinator, and masseter
Muscles of the torso include the deltoid, trapezius, latissimus dorsi, and rectus abdominus
Arm muscles include the biceps brachii, triceps brachii, and brachioradialis
Leg muscles include the gluteus maximus, rectus femoris, and gastrocnemius
Some muscle conditions/disorders are muscular dystrophy, hernia, tetanus, and compartment syndrome
Did you know…
Q: Are any smooth muscles controlled voluntarily?
A: Smooth muscles are defined as being involuntary. They are found in your skin, lining of the gastrointestinal tract, and in blood vessels. However, some skeletal muscles are controlled involuntarily. One example is the muscles associated with breathing. You don’t have to think consciously about inhaling/exhaling, it happens automatically. Now that you’re reading about breathing, you probably just thought about it!
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.
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