ANS 2: Week 7 Notes
ANS 2: Week 7 Notes ANS 002
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This 5 page Class Notes was uploaded by Mackenzie Hayes on Wednesday May 11, 2016. The Class Notes belongs to ANS 002 at University of California - Davis taught by Dr. James Murray in Spring 2016. Since its upload, it has received 17 views. For similar materials see Introductory Animal Science in Animal Science at University of California - Davis.
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Date Created: 05/11/16
ANS 2: Week 7 Notes (5/9) ● Skeletal muscle = muscle cells bound together by connective tissue sheaths that are independent of individual cell membranes ○ Born with all the muscle fibres you will ever have ○ You’re not building more muscle cells, you’re making them bigger ○ Multi-nucleic = multiple nuclei in one cell ● Two types of muscle fibres ○ Striated - capable of rapid contractions ■ Red- slow twitch - sustained, continued work, more resistant to fatigue - aerobic ■ White - fast twitch - quick movement, fatigues rapidly - anaerobic ○ Smooth ■ Controlled by autonomic nerve system ■ Doesn’t contract rapidly ■ Lines hollow organs ■ Can be excited by stretching as well as nerve impulse ● Skeletal Muscle Terms ○ Epimysium - connective tissue ○ Perimysium - connective tissue ○ Endomysium - connective tissue ○ Fasciculi - bundles of myocytes ○ Myocyte - muscle fiber or muscle cell ○ Sarcolemma - cell membrane of a muscle cell ○ Myofibrils - functional unit of a muscle cell ○ Sarcomere - building block unit of a myofibril ■ Adds length to myofibril ● Structure of a Striated muscle: ○ Epimysium = connective tissue surrounding entire muscle ○ Perimysium = surrounds bundles of 10-20 myocytes (bundles = fasciculi) ○ Endomysium = connective tissue surrounding individual myocytes ● Myocytes : ○ individual muscle fibers = cells ■ *they are multinucleate (have multiple nuclei) ○ Each enclosed by cell membrane - s arcolemma ■ Attaches the muscle fiber to connective tissues ( endomysium) ● And thereby to the tendons ■ Key to generation and propagation of electric potentials responsible for cell contraction ○ Cytoplasm of muscle cells = s arcoplasm ■ Stores glycogen (for energy) and myoglobin (red, stores oxygen) ● Myofibrils ○ Basic units of contraction inside the myocyte ○ Composed of 2 types of fibrous proteins ■ Run along length of muscle fiber ■ Microstructure allows contraction ○ When they contract, the whole cell contracts ○ When parallel muscle fibers contract, the whole muscle contracts (5/11) ● More Muscle = more myofibrils ○ Can grow so much they split ○ Adding sarcomeres also grows muscle ■ Z line defines a sarcomere ● Myofibril: ○ Actin - thin filaments ○ Myosin - thick filaments ○ Contract and expand → leads entire muscle to contract ● Why is growth so important? Production ○ Meat, milk, eggs, fiber = most important agricultural sector ■ Body composition = critical, health of consumer ○ Feed utilization depends on growth efficiency ■ Most cost of this industry = feed ○ Energy partitioning determines reproductive success ■ Also immuno-competence and production performance ■ Tissue / Bone Growth = based on energy + nutrients ○ Fertility has gone down in the selection for production ■ Energy all put toward production, none left for repro ■ Need enough energy storedfor reproduction ■ Sheep Flushing - feed more right before ovulation and insemination = more lambs ● Factors Affecting Growth: life stage ○ Prenatal: ■ Litter size (more young = smaller at birth) ■ Size +nutritional status of mom ■ Genetics of offspring (growth potential and fetal growth) ○ Postnatal - preweaning: ■ Nutritional status of mom ■ Litter size (affects ability to feed) ■ Initial size / aggressiveness of young(also affects feed success) ■ Exposure to disease = parasites (building immunity) ○ Postnatal - postweaning: ■ Gender, genetics, nutrition, disease/parasites, social stress, environmental conditions ● Handlers factor into this ● Hormones: know a few major ones + functions and sources ● Growth: ○ Most basics = increase in weight ○ Growth = increase in weight until mature size is reached ■ Conception → maturity ○ Growth can also be increasing cell number ○ What to measure: ■ Determine how genotype, feed, management affect growth and composition ■ Predict growth responses to specific conditions (breed, feed…) ■ Increasing cell numbers and increasing cell size ● Hypertrophy: increase cell size ○ Muscle and fat tissue grows this way ● Hyperplasia: multiplication of cells ● Nutrition of mother affects oocytes (genetic potential) ○ Get cow → feed well → feed offspring well → offspring’s offspring then have great genetic potential ● Germ Cell Layers: ○ Ectoderm = outside body ■ Skin ○ Endoderm = inside body ■ gut , liver, lungs ○ Mesoderm = everything in between ■ Skeleton, muscle, heart, blood
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