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Muscular System. Anatomy and Physiology. Muscular System Functions. Movement is the primary function of the muscular system. All of this movement (running, chewing, stomach churning etc.) is accomplished through muscle contraction. Muscles pull, they never push. men's tumbling.
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Muscular System Anatomy and Physiology
Muscular System Functions • Movement is the primary function of the muscular system. • All of this movement (running, chewing, stomach churning etc.) is accomplished through muscle contraction. Muscles pull, they never push.
Other Muscular System Functions • Holding organs in place. (i.e. Rectus Abdominis) • Generating heat for warmth. • Protection • Cushioning.
Skeletal Muscle Tissue • These muscle cell fibers (muscle cells) are multinucleated. • They can be up to 30 cm in length. • The bands seen in this picture indicate where the myosin and actin fibers overlap each other • Contraction is voluntary and quick. • Contraction is triggered by nervous system • They are enveloped and anchored to connective tissue.
Smooth Muscle tissue • Smooth - involuntary, 1 nuclei per cell, no striations, slow rate of contraction • Found in arterial vessel walls, intestinal walls, alveoli walls
Cardiac Muscle Tissue • Cardiac Muscle tissue • Involuntary, 1 or 2 nuclei per cell, intercalated disks (D), striated, quick contraction • Found only in the Heart • The heart begins beating from the end of the third week of embryonic development.
Cardiac Muscle Tissue • This is a high power (400X) view of cardiac tissue. • See if you can spot the intercalated discs. • This tissue looks different from skeletal muscle tissue. (Look for branching) • If cardiac muscle cells are removed from the heart and kept alive in a culture dish they continue to contract rhythmically. • In the living person the rhythm of the individual cardiac cells is set by the nerve supply to the heart.
Skeletal Muscle Structure • The muscle fiber is analogous to a muscle cell. • The cells are arranged in bundles called fasicles. • The fasicles are arranged in bundles to form a muscle. • Muscles are arranged together in groups (quadriceps, hamstrings).
A sarcomere is a contracting unit of a muscle cell fiber. • There will be hundreds of these repeating units in each muscle cell fiber. • The striations are caused by the overlapping myosin and actin myofibrils.
Satellite Cells New muscle cells form from undifferentiated precursor cells called satellite cells. This is a way for muscle cells to repair themselves. Once you are an adult muscle cell fibers cease to multiply. As a person ages muscle tissue atrophies and is replaced by connective tissue.
A motor unit is a group of muscle cell fibers that are activated by a single neuron.They vary dramatically in size from two to several thousand muscle fibers.A muscle like the biceps brachii may contain thousands of motor units.
Myoneural Cleft • Nerve impulses reaching this gap release acetycholine to carry the impulse to the muscle cell fibers • Acetylcholine causes depolarization of the muscle cell membrane.
Depolarization • Acetylcholine changes the permeability of the cell membrane • This results in a charge reversal across the cell membrane. • Ca+2 is released from the sarcoplasmic reticulum. • This ion flows through the t-tubules of the sarcoplasmic reticulum to reach all of the myofibrils in the muscle cell fiber. • The Ca+2unmasks active sites on the thin (actin) myofilaments
Simple Twitch • A single depolarization produces a single contraction (simple twitch) • The strength of a contraction (strength gradation) depends on how many motor units are stimulated. • Muscles responsible for fine control (i.e. eye movement) have many more motor units. • A muscle fiber stimulated several times, quickly, produces a sustained (tetanic) contraction.
All Vertebrates have two distinct muscle types of skeletal muscle fibers
ATP • Utilized as a source of energy muscle cell contraction • Consists of an organic body plus a tail composed of three phosphate groups. • The last two phosphate groups are attached by high energy bonds which are readily formed and broken
Creatine phosphate is a long term phosphate storage molecule. It allows for a rapid conversion of ADP to ATP
Acetylcholine • acetylcholine (ACh) is made from acetyl CoA and choline • ACh is stored in synaptic vesicles • Nerve impulse releases ACh • ACh binds to and activates receptor sites. • ACh is enzymatically broken down by acetylcholinesterase (AChE) located in the synapse. • Acetylcholine is the neurotransmitter at neuromuscular junctions, synapses in the autonomic nervous system, and at synapses in several parts of the nervous system.
Myoglobin • Red pigment found in most muscles. • Stores some O2 for use in muscle contraction. • Allows muscle to work aerobically for a longer time.
Energy supply comes from glucose • If broken down aerobically, it yields 36 ATP’s and CO2 and HOH • This process happens slowly. • If not enough O2 is available, glucose broken down anaerobically. • This essentially just splits the glucose molecule in half generating 2 ATP’s and Lactic acid. • This process happens quickly.
Isotonic Exercise • This is exercise that involves movement. • This type of exercise leads to an increase in the supply of blood (number of capillaries) to that muscle and the heart muscle as well. • This allows the muscle to receive more oxygen and therefore go into oxygen debt later.
Isometric Exercise • This is exercise without movement. • Great tension is applied to the muscles. • This results in increased muscle strength and size. • It does not increase that muscles or the heart’s vascularity. • It does burn calories and lower cholesterol.
Muscle Strength and Muscle Power • Muscle Strength is directly proportional to muscle size. • The larger a muscle the greater its strength. • Weightlifters tear muscle cell fibers while they are lifting. • The muscle cell fibers repair themselves and get larger (hypertrophy) by increasing the number of myofibrils they have. • Muscle power is the amount of work/time. • Muscle power is related to how fast the contraction can be accomplished.
There is no evidence that being born on another planet will give you super strength.
Having artificial robotic parts will not make you super strong!
Muscle Atrophy • Muscles respond to use and non-use. • When a muscle is not used or cannot be used it atrophies and gets smaller. • Unused muscles can lose as much as 50% of their mass in a month. • Polio is a viral disease that attacks the nerves in various parts of the body. • It can lead to paralysis (President Franklin Roosevelt). • It is now very rare in the US thanks to the Polio vaccine.
Polio • Polio (also called poliomyelitis) is a contagious, viral disease. • Historically, it was devastating and has plagued people since ancient times. • It was virtually eliminated from the Western hemisphere in the second half of the 20th century. • Its most extensive outbreak occurred in the first half of the 1900s. • At the height of the polio epidemic in 1952, nearly 60,000 cases with more than 3,000 deaths were reported in the United States alone. • This is an electron image of a polio virus.
Polio types • In about 95% of cases there are no symptoms (asymptomatic polio). • In the 4% to 8% of cases in which there are symptoms (symptomatic polio), the illness appears in three forms. • A mild form, abortive polio (sickness is limited to flu-like symptoms such as mild upper respiratory infection, diarrhea, fever and sore throat. • A more serious form associated called nonparalytic polio (1% to 5% show neurological symptoms such as sensitivity to light and neck stiffness) • A severe, debilitating form called paralytic polio (this occurs in 0.1% to 2% of cases)
Paralytic Polio • Paralytic polio causes muscle paralysis - and can even result in death. • In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream, attacking the nerves (in abortive or asymptomatic polio, the virus usually just stays in the intestinal tract). • The virus may affect the nerves governing the muscles in the limbs and the muscles necessary for breathing, causing respiratory difficulty and paralysis of the arms and legs.
Contagiousness • Polio is transmitted primarily through the ingestion of material contaminated with the virus found in stool (poop). • Not washing hands after using the bathroom and drinking contaminated water were common culprits in the transmission of the disease.
