The Muscular System. Flashcards
What are the three types of muscle?
Skeletal, cardiac and smooth.
What are the 5 major functions of the muscular system?
Produce movement, maintain posture, support soft tissues, guard openings, and generate heat.
From largest to smallest, what are the different units of a muscle? (A box, inside of a box, inside of a box).
Belly/Body, Fascicle, Myofibril, Sarcomere, Myofilament.
The state of physiological inability to contract, even though the muscle still may be receiving stimuli.
Muscle Fatigue.
The extra amount of oxygen that the body must take in for restorative properties - the amount of oxygen required to convert accumulated lactic acid to glucose and to restore supplies of ATP and creatine phosphate.
Oxygen Debt.
Skeletal muscles are described as voluntary, but even relaxed muscles are almost always slightly contracted, a phenomenon called ____.
Muscle tone.
Muscle length changes (decreasing the angle at the joint), and moves the load. Once sufficient tension has developed to move the load, the tension remains relatively constant through the rest of the contractile period.
Isotonic contraction.
What are the two forms of isotonic contractions?
Concentric, and eccentric.
A contraction in which the muscle shortens, and does work - picking up a book, kicking a ball.
Concentric.
The muscle generates force as it lengthens, and are equally important for coordination and purposeful movements. Example: it occurs in the calf muscle as you walk up a steep hill.
Eccentric contraction.
Tension may build up to the muscle’s peak tension-producing capacity, but the muscle neither shortens nor lengthens. Example: the muscles around the knee in a squat.
Isometric contraction.
Compare concentric and eccentric contractions.
In a concentric contraction, the muscle shortens and does work, In an eccentric contraction, the muscle generates force and lengthens.
Compare isotonic and isometric contractions.
In an isotonic contraction, the muscle is either shortened or lengthened as it performs work. However, in an isometric contraction, the tension in the muscle may build up to a peak-tension, but the muscle does not shorten or lengthen.
Attachment of a muscle that remains relatively fixed during muscular contraction.
Origin.
Movable attachment of a muscle.
Insertion.
Cord of dense fibrous tissue attaching muscle to bone.
Tendon.
Fibrous or membranous sheet connecting a muscle and the part it moves.
Aponeurosis.
Bundle of nerve or muscle fibers bound together by connective tissues.
Fascicle.
A slender, threadlike structure or filament.
Fiber.
Sheath of fibrous connective tissue surrounding a muscle
Epimysium.
Connective tissue enveloping bundles of muscle fibers.
Perimysium.
The connective tissue surrounding each muscle cell.
Endomysium.
What causes muscle fatigue?
Muscle fatigue comes from strenuously exercising a muscle for a prolonged period of time. The muscle may lose it’s ability to contract due to interruption in the muscles blood supply, and therefore an interruption in the oxygen supply. However, it is most commonly associated with an accumulation of lactic acid in the muscle.
A wasting away or decrease in size of tissue, such as muscle fibers, usually from lack of use.
Atrophy.
What are the effects of lactic acid?
An increase in blood acidity, muscle fatigue.
How does aerobic exercise effect muscles?
The changes result in more efficient muscle metabolism, and in greater endurance, strength, and resistance to fatigue.
How does resistance exercise effect muscles?
Resistance exercises cause muscle hypertrophy and large gains in skeletal muscle strength.
Rodlike bundle of contractile filaments found in muscle fibers.
Myofibril.
Filament that constitutes myofibrils. Of two types - actin and myosin.
Myofilament.
where thick filaments are: the entire length of the thick filament.
A-Band.
The area of a sarcomere where there are only thin filaments -divided by Z-lines (which hold the actin in place)
I-Band.
Specialized endoplasmic reticulum of muscle cells. It’s interconnecting tubules surround each myofibril; most of these tubulues run longitudinally along the myofibril. Others form larger, perpendicular cross channels at the A-band/I-band junctions - these channels are called terminal cisternae and they always occur in pairs.
Sarcoplasmic reticulum.
At each A-band/I-band junction, the sarcolemma of the muscle cell penetrates into the cell interior, forming an elongated tube.
T-Tubule.
Describe the sliding filament mechanism of muscle contractions:
The sliding filament theory of contraction states that during contraction, the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree. In a relaxed muscle fiber, the thick and thin filaments only overlap at the ends of the A-band, but when muscle fibers are stimulated by the nervous system, the myosin heads latch onto the myosin binding sites on actin in the thin filaments, and the sliding begins.
How is smooth muscle different from skeletal muscle, in structure and action?
Smooth muscle is involuntary and non-striated, whereas skeletal muscle is both striated and voluntary.
What are the four sources of ATP for muscular contraction? Which are the most rapid?
Stored ATP, Creatine Phosphate, Anaerobic glycolysis, and Aerobic respiration - the most rapid is stored ATP.
What is the threshold stimulus/all or nothing concept of muscle stimulation?
The property in muscle and nerve fibres of either responding wholly to a stimulus or not at all. The strength of the stimulus must exceed a particular threshold or there will be no response, but when the response occurs it is total. The law applies to individual fibres and a graded response is obtained by a variation in the number of fibres activated.
What is a motor unit?
A motor neuron and all of the muscle fibers it supplies.
What is a muscle twitch?
The response of a motor unit to a single action potential of it’s motor neuron. The muscle fibers contract quickly and then relax.
Describe the process of creatine phosphate as it relates to ATP.
The CP stored in the muscles are tapped to regenerate ATP while the metabolic pathways are adjusting to the suddenly higher demands for ATP.
Describe the process of anaerobic glycolysis as it relates to ATP production.
As stored ATP and CP are used, more ATP is generated by catbolism of glucose obtained from the blood or by breakdown of glycogen stored in the muscle. During glycolysis, glucose is broken down into two pyruvic acid molecules, releasing enough energy to form small amounts of ATP. While pyruvic acid normally then enters the mitochondria and reacts with oxygen to produce more ATP, but when muscles contract vigorously, the muscles compress blood flow, and most of the pyruvic acid is then transformed into lactic acid.
Describe the process of aerobic respiration as it relates to the production of ATP:
Aerobic respiration occurs in the mitochondria, requires oxygen, and involves a sequence of chemical reactions in whch the bonds of fuel molecules are broken and the energy released is used to make ATP. During this process, glucose is broken down entirely, yielding water, carbon dioxide and large amounts of ATP as the final products.
What is the role of troponin and tropomyosin?
- cross bridge-binding of actin and myosin
- Roles are to regulate formation of cross bridges this regulation is done using Ca, in absence of Ca, tropomyosin blocks the actin myosin binding sites
- When Ca is present it binds to TnC, causing a conformational change to the troponin complex that forces torpomyosin to move away from the actin myosin binding iste
thus allowing actin to bind to myosin and form the cross bridge.
What are spatial or temporal wave summations?
increasing the number of stimuli delivered to a given motor unit per time.
Results in increased Ca concentration which then causes more tension/shortening.
Name the four rotator cuff muscles:
Supraspinatus muscle
Infraspinatus muscle
Teres minor muscle
Subscapularis muscle
What muscles are involved in smiling?
Zygomaticus, orbicularis oris, Levator labii superioris, risorius.
What are the muscles involved in frowning?
Mentalis, depressor anguli oris, depressor labii inferioris.
Condition that occurs when the load is close to the fulcrum, and the effort is applied far from the fulcrum; allows a small effort exerted over a relatively large distance to move a large load over a small distance.
Mechanical advantage.
Condition that occurs when the load is far from the fulcrum and the effort is applied near the fulcrum; the effort applied must be greater than the load to be moved.
Mechanical disadvantage.
What mechanical support system provides power?
Mechanical advantage.
What mechanical support system provides speed?
Mechanical disadvantage.
Partnerships between the muscular and skeletal systems.
Lever systems.
A rigid bar that moves on a fixed point.
Lever.
In the body, the ___ are the fulcrum.
Joints.
In the body, the ___ act as the levers.
Bones.
In the body, the ___ are the applied force.
Muscles.
The weight to be moved.
Load.
In the body, the ____ is the weight of muscle; weight of body or object in hand.
Load.
The fixed point on which a lever moves.
Fulcrum.
The load is the ____ itself, along with overlying tissues and anything else that is trying to be moved.
Bone.
These levers are useful because they provide rapid contractions with a wide range of motion.
Mechanical disadvantage.
Effort farther than than load from fulcrum =
Mechanical advantage.
Effort nearer than load to fulcrum=
Mechanical disadvantage.
In _____, the effort is applied at one end of the lever and the load is at the other, with the fulcrum somewhere between.
First-class lever.
