Stimuli arriving in close sequence causing larger contractions. Sustained by release of calcium into the sacroplasm from the sarcoplasmic reticulum.
Sustained but wavering contraction as a result of partially relaxing inbetween each 20-30 stimuli per second. Sustained by the release of calcium in the sarcoasm by the sarcoplasm reticulum.
When a skeletal muscle fiber does not relax at all because of the steady rate of 80-100 stimuli per second, the contractions are sustained. There are no twitching. Sustained by the reslease of calcium into the sarcoplasm by the sarcoplasm reticulum.
Motor unit recruitment
Process by which the number of motor units is increased. Helps produce smooth movements instead of jerky ones.
Consists of one motor neuron plus all the skeletal muscle fibers it stimulates. Larger motor neurons are less precise and are found in theigh muscles or example. Smaller motor units are more precise and are found in the eye muscle. One motor neuron makes contact with 150 muscle fibers and make them contract at the same time.
A brief contraction of all the muscle fiber in a motor unit in response to single nerve impulse to its motor neuron.
The record of a muscle contraction. Includes the latent, contraction and relaxion period.
A small amount of tautness or tension in the muscle due to weak, involunary contractions of its motor units. Keeps firmness but doesn't allow movement.
A state of limpness in which muscle tone is lost in response to damaged motor neurons.
"Equal tension" change in the length of muscle but no change in tension. Its used for body movements and the movement of objects. Two subtypes.
Concentric istonic contractions
Muscle shortens nd pulls on another structure such as a tendon to produce movement and reduce an angle at a joint. Tension in the myosin heads is greater the the resistance of the object being moved and the muscle shortens. Ex picking up a book off a table
Eccentric isotonic contraction
When the length of muscle increases during a contraction. The tendion exertef by the myosin ad resist contraction of another muscle or pull of gravity slowing the lenthening process. Produces unexplained muscle damage. Ex lowering a book
"Same measure" holding an object steady with no movement. When the resistance equals or exceeds the muscle tension. Important in maintaining posture.
ATP use in muscle fibers
3 differnt times where ATP is needed-> to pump calcium up its concentration gradient back into the sarcoplasmic reticulum at contraction rest, to power the myosin head's power stroke, as myosin heads bind to ATP they detach from actin.
Produced only in muscle fibers and acts as a resivoir. Its the fastest way to make ATP from ADP and the high-energy phosphate group creatine stores. Sufficient for short bursts of physical activity.
Anaerobic cellular respiration
This process does not require oxygen and breaks down glucose to make two ATP molecules. Glucose from the blood passes into the contracting muscle fibers and breaks it down into two pyruvic acids and 2 ATP. This process is called glycolysis and uses two ATP to have it happen. The pyruvic acid converts into lactic acid that diffuses into the blood and brought to the liver to convert it back to glucose. The glucose tabilizes blood acidity and provides muscles with more glucose.
Aerobic cellular respiration
Requires oxigen. This process produces 36 molecules of ATP with in the mitochondria per glucose molecule. Pyruvic acid from anaerobic cellular respiration enters the cell and is oxidized generating ATP, CO², H²O and heat. Hemoglobin from blood supplies the mitochondria with oxygen and myglobin binds to oxygen to supply it to the mitochondria as well. Breakdown of triglycerides in adipose tissue supplies fatty acids to the muscle cell and it contains oxygen. Also oxygen is supplied by amino acids from the break down of proteins. In activities that lasts more then 10 minutes this type of process supplies most of the ATP gor muscle contractions.
The inability of a muscle to contract forcefully after prolonged activity. Inadequate release of calcium ions from the sarcoplamic reticum, insufficieant oxygen supply causing a lack of ATP, depletion of nutrients/glucose, build up of lactic acid/ADP, and failure of ACh to release nerve impulses may be the culprit.
Oxygen debt/recovery oxygen uptake
After prolonged periods of uscle contraction it takes from a couple of minites to a couple of hours to restore the oxygen needed for aerobic cellular respiration. The oxygen converts lactic acid back into glycogen in the liver, resynthesize creatine phosphate/ATP, and eplace oxygen removed from myoglobin.
Slow oxidative fibers
Has the smallest in diameter, appear dark red and are the least powerful type of skeletal muscle fibers. These fibers have many mitochondria and generate ATP by aerobic cellular respiration. These slow contracting fibers are very resistant to fatigue and have a high stamina.
Fast oxidative-glycolytic fibers
Intermediate in diameter, are dark red in color And generates ATP through aerobic and and anaerobic cellular respiration. Glycogen level is high. Can generate ATP faster and contract faster then slow oxiative fibers.
Fast glycolytic fibers
Largest in diameter, contains the mdt myofibrils, and generate the most powerful contractions. Uses anaerobic respiration and are white fibers due to the lack of myoglobin and blood capillaries. These fibers contract the fastest and the strongest but fatigue quickly. Muscle enlargement is due to the increased synthesis of muscle proteins in these fibers.
Located in the heart walls, has a stair step appearance, a centrally located nucleus and the fibers are shorter in length.
Cardiac muscles interact with one another by irregular transverse thickenings of the sarcolemma containing desmosomes and gap junctions.
Holds the muscle fibers together and is part of the intercalated discs of cardiac muscles.
Allows muscle action potentials to spread quickly from one cardiac muscle fiber to another and is part of the intercalated discs.
Skeletal muscle fibers
Fiber diameter -> large 10-100 Appearance-> long cylindrical with peripherally located nuclei and striated. Location-> attached to bones by tendons. Connective tissue components-> endomysium, perimysium, epimysium. Sarcomeres -> yes. Sarcoplasmic reticulum -> abundant. T-tubules-> yes, @ A-I band junction. Junctions between fibers -> none. Autorhymicity-> no. Source of calcium -> SR. Speed -> fast. Nervous control -> voluntary. Contraction regulated by -> ACh released by somatic motor neurons. Regeneration -> limited, satelite cells
Cardiac muscle fibers
Appearance -> branch cylindrical, one centrally loc. nucleus, intercalated dics join other fibers, striated. Loc-> heart. Fiber diameterr -> 50-100. Sarcomeres -> yes. SR -> some. T-tubules -> yes, z disc. Junctions-> intercalated discs have gap junctions and desmosomes. Autorhythmicity -> yes. Calcium source -> SR and interstitial fluid. Speed -> moderate. Nervous control -> involuntary. Contraction regulated by -> ACh/norepinepherine released by autonomic neuron motor neurons, several hormones. Regeneration-> limited under certain conditions
Smooth muscle fibers
Appearance -> thickest in the middle, tapered at each end, one. Centrally positioned nucleus, not striated. Location-> walls of hollow vicera, blood vessels, iris/ciliary body of eye, arrector pilli. Diameter-> small 5-10. Sarcomeres-> no. SR -> scanty. T-tubules -> no. Junctions-> gap junctions in visceral smooth but none in multiunit smooth. Calcium source -> SR and interstitial fluid. Speed -> slow. Nervous control -> involuntary. Contraction regulated by -> ACh/norepinepherine released by autonomic motor neurons, several hormones, local chemical changes, stretching. Regeneration -> considerable but not as much as epithelia
Multiunit smooth muscle tissue
Individual fibers with their own motor unit terminals and few gap junctions between neighboring fibers. Can stimulate one muscle fiber at once or many. Ex large arteries, lung airways, arrector pilli, internal eye muscles
Visceral smooth muscle tissue
Most common smooth muscle type found in sheets and form part of the walls of small arteries/veins/walls of hollow organs. Its stimulates one fiber as the action potential is transmitted to neighboring fibers.
Muscle tissue function
Producing body movements, stabilizing body positions, storing/moving substances with in the body, generating heat, electrical excitability, contractility, extensability, elasticity
Connective tissue that seperates muscle from skin and is composed of areolar, adipose and is higbly vascular supplying the muscle with blood/nutrients.
A sheet or broad band of dense connective tissue that supports/surrounds muscles and other organs of the body. Funct-> holds muscles with similar functions togethe, allows free mvmnt of muscles, carries nerves/blood vess/lymph vess, and fills spaces inbetween muscles.
Classified as a fascia, this layer encircles the entire muscle. Made of dense irregular connective tissue.
classified as a fascia, this tissue surrounds groups of 10-100 individual muscle fibers seperating them into fascicles. Made of dense irregular connective tissue.
This layer penetrates e interior of each fascicle and seperates each muscle fiber. Made of areolar connective tissue.
Cord of dense regular tissue composed of parallel bundles of collagen fibers that attach a muscle to the periosteum of a bone.
A tendon in the shape of a sheet.
Neurons that stimulate skeletal muscles fibers to contract.
Enlargement of existing muscle fibers after birth caused by human growth hormones and other hormones -> testosterone.
Increase in the number of muscle fibers.
When muscle tissue is not actively used, it loses its size and strength.
Retain the capacity to fuse with one another or with damaged muscle fibers to regenerate functional muscle fibers. The number of muscle fibers regenerated is not enough to compensate for significant muscle damage.
The replacement of muscle fibers by fibrous scar tissue. Skeletal muscle tissue can regenrate only to a limited extent.