Exam I study guide
Exam I study guide KIN 360
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This 26 page Study Guide was uploaded by Conor McDonough on Friday October 9, 2015. The Study Guide belongs to KIN 360 at Michigan State University taught by A. Parks in Fall 2015. Since its upload, it has received 30 views. For similar materials see Physical Growth and Motor Behavior in Kinesiology at Michigan State University.
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KIN 360 Exam 1 study guide 9142015 lecture notes Maturational Research Myrtle Researched two boys from birth until their 205 At 12 monthsquot Johnnyquot began to receive quottrainingquot in challenging environmental scenarios Researchers picked one of the fraternal twins named Johnny and decided thatJohnny would receive special training pertaining to growth and motor development The twins participated in speci c tests that would gauge their motor development and compare the capability of each boy at completing tasks that require ne motor movement and control These tests were completed at different stages in their infantile development Maturational Research Contribution o Belief that basic skills Will materialize Without facilitation Emphasis on Nervous system as a trigger for behavioral advancement Normative Period Key Researches 1 Anna Espenschade 2 Ruth Glassow 3 G Lawrence Rarick As interest waned from maturational many shifted focus toward the Education standardized tests 0 Motor Development Quantities scores loutcomes Biomechanical Period Key Researcher 1 Ruth Glassow 2 Loas Halverson Theones 1 Maturational Perspective 2 Information Processing Perspective Information Processing Executive directs all movement and change computer approach Theory the brain acts like a computer taking in information processing it and outputting movement Based on thought that the environment causes development Similar to Bandura s Social Learning or Skinner s Behaviorism Information processing became popular in the 1970 s with those specializing in Phys ed Emphasized Stimulusresponse bonds 0 Feedback 0 Knowledge of results Information Processing approached allowed for exploration of Attention Memory Feedback Variability across age Ecological Perspective Interrelationships exist between the individual the task and the environment These interrelationships are the drivers of this movement Newell s Model Dynamic System Belief that an executive would be overwhelmed by needs for movement Theodes Pertubation Attractor states Maturational Nervous system is primary system for development Supports the belief that development ends with puberty Ecological Perspective 0 Movement is composed of several different contributors without which a movement may not be possible 0 Contains 2 branches Dynamical Systems theory Proposed in 19805 Peter Kugler Scott Kelso and Michael Turivik studied the systems involved outside the CNS that contribute to movement Systems involved Nerves hormones muscles skeleton levers and motivation Nikolai Bernstein Studied how much the Central Nervous is involved in different points in different movements He also studied what is the bare minimum for Central Nervous system to be involved to complete a movement Dynamical Systems Theory Our body the individual the environment and our tasks are constantly changing and interacting This system is softly assembled Dynamical Systems Theory Near in nite number of possible combinations and resulting movements What combination of systems do we need to walk to skip Summary Walking is a less complex movement and requires less systems to complete the movement Skipping is a much more complex movement that requires many more systems to be integrated in the body in order to successfully coordinate a continuous skipping motion Crawling The term crawling in this course refers to an army crawl where there are more than 4 points of contact on the oor Creeping The proper term to describe the movement of using your hands and knees Gallop A Gallop is a term used to describe when we Attractor States Perturbation distance of motion course arrangement or states example adjusting the speed on the treadmill Control Parameter In uence the characteristics of the behavior Act as an agent for reorganization expressed as tempo force speed temperature frequency When the behavior loses stability the control parameter is altered and a new behavior emerges Rate Limiters DS theory from a developmental Perspective What does the Basin Diagram look like for a child who is crawling but has just learned to walk Where are the attractor states Which wells are the deepest What are the control parameters between the behaviors What are the rate limiters Answers muscles strength con dence Nervous system failing to coordinate signals and synapses to produce the exact signal or have the signal travel down the axons and reach the motor unit in time This is the trial and error portion in development in which the infant will progress to improve coordination and rearrange synaptic pathways so that the synapse is transmitted and elicits a ned tuned response Aging DST addresses changes in aging Declines in a system may be a rate controller reorganization of the movement Reorganization of the movement Active older adults tend to experience fewer declines thus maintaining movement patterns KIN 360 lecture notes 92115 Mechanical principles Preparatory Phase wind up 1 For the greatest force production maximum angular velocity the joints must be placed into a position for maximum rotation upon muscular contraction 2 In order to generate maximum velocity the body should be place into a position where the force can be applied over as long a period of time and as great a distance as possible 3 A shortened radius is desirable when economy of energy and increased speed are the objectives of the performance 4 The force imparted to objects should be a culmination of all the forces produced by the rotating joints a power train A Force production increases as the number of contributing joints in the power train increases B Maximum angular velocity is achieved when each joint in the power train enter the movement as the preceding joint is rotating at its maximum velocity 5 The greatest transfer of force occurs when a lever is extended to 180 degrees 6 For most efficient movement force should be produced in the line of direction of movement 7 Force must be applied to change the velocity of a body in motion 8 The greater the momentum of an approaching object greater must be the resistance that force if the object is to be stopped 9 Every projectile assumes a parabolic path discounting forces of friction a The path through the air is determined by the magnitude of the projecting force and the angle of appHcann b An airborne object will travel the greatest distance when the horizontal and vertical forces propelling it are equal if the take off and landing points are the same distance from the surface the ideal angle of projection is 45 degrees 10 Accuracy is increased when the ball bat and or body part travels through a linear path just prior to release or contact 11 To avoid interruption of the ballistic movement the antagonistic muscles used to dissipate momentum should not contract until the object is either released or contracted 12 To prevent injury of the body parts involved in the motion the force that are generated during the propulsive phase should be dissipated over as great a distance Physical Growth Maturation and Aging Prenatal development Period vs Trimesters Trimesters are markings of chronological time from the onset of conceonn Periods refer to developmental time ie what is going on with development of the embryo or fetus Phases and period are used interchangeably Phases 0 Germinal period rst two weeks 0 Embryonic period weeks 38 0 Fetal period weeks 9birth Trimesters 0 1st trimester months 13 Germinal period Germinal Period period of the egg 0 1st 2 weeks after fertilization Day 1 fertilization fusion of 2 sex cells Zygote divides continuously Blastomere is formed 0 1215 blastomeres Morula One morula enters the uterus Blastocyst 0 Day 6 Blastocyst implants in endometrium 0 Day 2 4 cell rapid cell division 0 Day 8 blastocyst sunk beneath endometrium Teratogens drugs or chemicals that causes abnormal fetal development alcohol prescription medicine illegal drugs nicotine excessive vitamins o Teratogen introduced in the germinal period will typically cause death of embryo Embryonic Period 0 Weeks 38 of prenatal period 0 What s happening Organ and system formation through differentiation 0 Three distinct layers of the embryonic disc Endoderml digestive amp respiratory Ectoderm gt nervous system sensory receptors skin features Mesodermgt Circulatory excretory Reproductive systems muscles and bones Cells have a distinct role but exhibit plasticity Week 3 2mm long the Neural tube At 8 weeks all the body s features have started to form along with all the organ systems This is when the embryo transitions into a fetus Embryo is most susceptible to in uences of a tetragon Fetal Period 0 Week 9 birth about 40 weeks 0 Rapid body growth 0 Change in size mass and proportions Hyperplasiagt more cells Hypertrophygt bigger cells 0 No new anatomic features 0 Functional development of organs tissues and systems Vulnerable time Direction of growth CephalocaudalHeadtoToes o ProximodistalMiddleOut Rapid growth 0 3rd month 3 inches 0 4th month68 inches 0 5th month 810 0 Growth in later fetal period Triples in weight Active period Fatty deposits distributed 68 pounds in weight KNOW THE GROWTH CYCLE CHART chart from Germinal to Fetal Period The ear eyes and central nervous system are particularly susceptible to damage during prenatal development Know the identifying characteristics of periods Know what parts are developing during the different time periods Trimester Highlights 1st trimester All major body organs and systems are formed but not completely developed 0 Critical period for development of the heart CNS limbs Eyes ears teeth and most organs 0 Any damage at this stage can result in major damage or deformity 2nol trimester Fastest Velocity of growth in whole human life 0 Fetal movements beginthe fetus moves kicks and swallows 0 Mother begins to show 0 End of the 4th month the CNS is past its most valuable 3rCI trimester 0 Body growth in length slows down 0 Most growth during this trimester is in weight 0 The fetus begins developing its own immune system Fetus becomes very cramped in the womb lf born as early as the 7th month the fetus will have a good chance of surviving Age does not always dictate growth Physical Growth 0 Increase in size of the body as a whole or the size attained by speci c parts of the body 0 Changes in size are outcomes of three underlying cellular processes 0 Cell size increase Hypertrophy 0 Cell number increase Hyperplasia 0 Increase in intercellular matter Accretion Why is understanding growth and maturation important 0 Understand individual variability Screendiagnose health and nutritional problems Growth in Length and Stature Distance Curve Graphic illustration of cumulative growth KIN 360 Lecture 92815 Chapter 11 and half of chapter 10 will not be on the exam 107 review before exam is optional attendance Exam format majority of questions are multiple choice and some short answer responses most likely the short answer will test the information in assignment 1 Functional constraint examples fear anxiety There are methods to measure levels of functional constraints but there is no exact measurement Structural constraints Physical attributes that have exact measurements Skeletal System Structure of long bones o The central shaft is the diaphysis Compact bone around the marrow medullary cavity 0 The ends of the bone are epiphyses Compact bone surrounding spongy bone 0 Epiphyseal plate is located in the Metaphysis portion of the bone 0 Metaphysis is the transitional portion located in between the diaphysis and epiphysis The epiphyses contain the epiphyseal plates and are surrounded on the outside by articular cartilage Organization of Bone Tissue Mineral salts 66 of bone weight 0 Calcium phosphate combines with calcium hydroxide to form hydroxyapatite 0 Protein bers 32 of bone weight Collagen portion Elastin Portion Organization of Bone tissue Bone cells Osteocytes Mature bone cells Maintain the surrounding matrix Located within lacunae that are between layers of matrix called lamella Osteoblasts Immature bone cells Located on the inner or outer surface Secrete organic components of matrix osteoid that later ossify osteogenesis Become osteocytes Osteoprogenitor cells bone stem cells Bone stem cells Located in the CT covering and lining on bones Daughter cells differentiate into osteoblasts Osteoclasts Large cells that arise from same stem cells that produce monocytes Located in areas of bone removal Secrete acids and enzymes that break down the matrix osteolysis 0 Timing 6th week post fertilization through adolescence males age 21 females age 17 Process is known as osteogenesis and ossi cation Two types of ossi cation 1 lntramembranous begin with brous CT 2 Endonchondral begins whyaline cartilage Preossi cation Hyaline cartilage model of the bone forms and grows Step 1 As cartilage enlarges chondrocytes near the center enlarge and matrix calci es Step 2 Cells of the periochodium differentiate into osteoblasts The perichondrium is now the periosteum and the cellular layer forms a bone collar Step 3 Capillaries and osteoblasts migrate to center of model Calci ed cartilage matrix breaks down and I replaced by spongy bone This becomes the primary ossi cation center Step 4 As diameter of bone increases spongy bone in the diaphysis is dissolved by osteoclasts to form the marrow cavity Longitudinal Growth increasing bone length 0 Step 1 centers of epiphyses calcify and 0 Step 2 Epiphyses become lled with spongy bone Thin layer of original model remains as articular cartilage KIN 360 lecture notes for 9302016 Changes in muscle ber size 0 Increased muscle ber diameter due to hypertrophy Sex differences emerge by adolescence Males have a greater mean crosssectional area Changes in muscles mass 0 Muscle mass increases with age Muscles aging Only 10 of skeletal muscle mass is lost between 205 and 505 0 After 50 another 30 is lost before 85 0 Another 50 may be lost between 805 and death Declines in muscle and bone mass are constraints for movement as we age 0 This includes cardiovascular health as the hear is a muscles too Adipose tissue Hyperplaisa Proliferation and differentiation of adipoblasts and preadipocytes in adipose tissue adipoblasts originate from mesoderm Preadipocytes contain LPL o Hypertrophy Increased Triacyglycerol accumaltion TAG in exisiting adipocytes Adipocyte size during growth 0 Diameter increases from 3040 um at birth to 80 100 um at adu hood oMostly in 1st year Adipocyte number during growth 0 Number increases from 5x10quot9 at adulthood Little increase to age 1 or 2 Gradual increase to puberty Sharper increase in adolescence with plateau late greater in females vs males Subcutaneous fat during drowth Sharp increase from birth to 1 year Decrease during early cthhood Preadolescentincrease Adolescence girls increase boys decrease o Trunk and limbs are similar during childhood Adolescence boys trunk increases while limbs decrease girls trunk and limbs increase at same pace Subcutaneous vs Visceral fat 0 Ratio of subcutaneous fat to total body fat declines with age from until adolescence Adolescence girls continue to decline boys continue to increase until plateau Not all fat cells are created equal Men large insulin resistant adipocytes adrenergic receptors increase Insulinmediated Antilypolysis Catecholamine mediated lipolysis increase Women have small insulin resistant adipocytes Adipose tissues and aging Average gains in US between 2050 0 Male 82kg 0 Women 118 kg Weight loss with age tends to be associated with bone and muscle mass decreases Subcutaneous fat Limb fat decreases with age Abdominal fat increases with age The facts above both contribute to an increased likelihood of developing cardiovascular disease Endocrine system Hormonal pathwavs oEndocrine Pathway o hormones are carried in the bloodstream to target oParacrine Pathway o Hormone effects neighboring cell oAutocrine pathway 0 Hormones affect the cell producing them olntracrine Pathway o The hormone effects the cell without or before being secreted Endocrine svstem traditional view 0 Pituitary o Thyroid o Parathyroid Pineal body 0 Thymus Adrenals Pancreas Ovaries and testes Modern endocrine system consists of Receptors Number of receptors varies amongst tissues throughout the life cycle Hormone actions 1 Morphogenesis The rate of growth of the body and its parts and the maturation of the gonads and the secondary sex characteristics are regulated by the hormones 2 Integration Through circulation virtually all parts of the body are exposed to the hormones Growth hormone Decreases carbohydrate uptake Enhances mobilization of lipids for energy needs Growth factors 0 GH is similar to 2 growth factors lGFl plays role in regulating linear growth 0 lGFll especially important to growth during fetal development lGFl Effects cartilage Proliferation of cells at the growth plates of long bones 0 Linear growth Occurs without accelerating skeletal maturation or fusion of epiphyseal plate IGF1 concentration increases at a steady rate for both sexes until puberty girls enter puberty earlier so they have an earlier spike in lGFl and also an earlier decrease in lGFl Thyroid hormones Calorigenic stimulate oxygen uptake and energy expenditure Thyroxine GH is unable to function in its absence 0 Hypothyroidism can effect a vast majority of physiological systems Gonadal hormones Females LH amp FSH stimulate the ovary to release estrogen and progesterone which stimulate the hypothalamus Hypothalamus then stimulates the pituitary gland which secretes LH amp FSH Females LH amp FSH stimulate the ovary to release estrogen and progesterone which stimulate the hypothalamus Hypothalamus then stimulates the pituitary gland which secretes LH amp FSH Androgens Testosterone most abundant in males Dihydrotestosterone most potent and responsible for secondary sex characteristics Estrogens o Estradiol Most potent in females lnsulin Essential in carbohydrate metabolism Glucose uptake in skeletal muscles and adipose cells 0 Potential to inhibit adipose tissue lipolysis Can perform lipogenesis Endocrine aging Gradual imbalance theory Nervous system endocrine system and immune system fall out of sync leading to increased risk of disease in older adu s o Thyroid Decrease with age Congestive heart failure has been linked to hyperthyroidism Hypothyroidism is associated with accelerated aging in older adults Gonadal Decrease with age Androgen supplementation may deter muscle wasting and osteoporosis Insulin Similar to younger adults Occurrence of type 2 diabetes increases with age Nervous system Crucial system Genes Early on neurons the cells of the nervous system that receive and transmit information Develop 25000 per minute Month34 all neurons formed Genes produce an abundance to afford pruning of the system Dendrite receives transmissions Cell body functions to keep cell alive Axon carry and transmit information Prenatal development month 6 All neurons are in their nal location Migration process is crucial to normal brain development Neurons specialize Once in place axon grows to connect to the neurons in the region Once in place axon grows to connect to other neurons Prenatal development 0 Birth By birth axons re to strengthen connections Random ring pattern rst nut becomes more organized as you age Maye conne Postnatalgr O Teratogens ffect migration pattern of neurons causes fetal alcohol syndrome Lower le Reading and math disabilities Evidence for epilepsy autism and dyslexia ction owth Birthage 4 o Brain grows to 80 of adult weight o Increase in synapse 1000100000 0 Increase in Glia and Myelin Lower brain 0 Highly developed at birth Supports vital functions such as breathing and animalistic instincts Mediates re exes and reactions 0 Higher brain centers o Associated with occurrence of goaldirected movements o 45 months usually when reaching is a commonly tried movement Spinal cord 0 small and short at birth o Myelination Reaction speed and movement time Reaction speed decreases and movement time slows progressively with age oMostly due to slowing of central processing due to 1 Reduced blood ow 2 Cellular and enzymatic changes Speedaccuracy trade off In most movements there is a tradeoff for the speed at which you initiate a movement and the accuracy of that movement KIN 360 chapter 1 notes from textbook Chapter 1 Theoretical Perspectives in Motor Development Ecological Perspective stresses the interrelationships between the individual the environment and the task According to the ecological perspective you must consider the interaction of all constraints body type motivation temperature and ball size in order to understand the emergence of a motor skill The ecological perspective has two branches one concerned with motor control and coordination dynamical systems and the other with perception perceptionaction The two branches are linked by several fundamental assumptions that differ notably from the maturational and information processing perspective Maturational perspective tend to focus on the central nervous systems as the only system relevant to development and the only rate controller The Dynamical systems approach focuses on many systems and acknowledges that different systems might act as area controllers for different skills Another feature of the dynamical systems approach is that it allows for the study of development across the life span An important motor development concept produced by the dynamical systems approach is the notion of rate limiters or controllers The body s systems do not develop at the same rate rather some might mature quickly and others more slowly and each system should be considered a constraint The dynamical systems approach focuses on may systems and acknowledges that systems might act as rate controllers for different skills Another feature of the dynamical systems approach is that it allows for the study of development across the life span PerceptionAction Approach The second branch of the ecological perspective JJ Gibson proposed a close interrelationship exists between the perceptual system and the motor system emphasizing that these systems evolved together in animals and humans In this approach we cannot study the individual while ignoring the environment In addition we cannot study the individual while ignoring the surrounding environment Gibson used the term affordance to describe the function an environmental object provides to an individual this is related to the size and shape of the object and the individual within a particular setting Gibson also rejected the notion of a CNS executive that performs almost limitless calculations on stimulus information to determine the speed and direction of both the person and the moving objects The information processing perspective holds that such calculations are used to anticipate future positions so that we can for example reach up to catch a thrown ball Body scaling The use of intrinsic relative to body size rather than extrinsic dimension Chapter 3 notes from the textbook Chapter 3 Principles of motion and Stability Newton s 1st law of motion An object at rest stays at rest or an object in motion stays in motion until acted upon by a force It takes force to move something standing still and force to change the direction of something moving Newton s 2ncl law of motion states that the acceleration of a person or object that is proportional to the force applied to it and inversely proportional to the force applied to it and inversely proportional to its mass Newton s 3rCI law of motion states that for every force you exert on an object the object exerts an equal force back on you in the opposite direction Rotational movement individuals move when their limbs rotate around one or several joints KIN 360 Chapter 4 notes from textbook Chapter 4 Physical growth Maturation and Aging Humans as members of a single species experience many common steps and processes in growth and aging Genetic factors drive a very orderly and sequenced pattern of growth and aging so in many respects we know what to expect On the other hand individuals each have their own unique potential and their own timing When we observe a group of preadolescents of the same chronological age we nd a huge range of sizes Growth and aging are also affected by a variety of extrinsic factors such as nutrition and disease Genetic and extrinsic factors combine to in uence physical growth and aging Prenatal Development The growth process begins the instant an ovum egg and spermatozoon fusein fertilization Carried out under the control of genes early development is astonishingly precise Genes then determine the normal spects of development and inherited abnormal development At the same time the growing embryo and later the fetus is very sensitive to extrinsic factors which include the environment in which the fetus is growing the amniotic sac in the uterus and the nutrients deliviered to the fetus via the mother s circulation and placenta So even in the womb individual genetic factors and extrinsic factors interact in the fetus development Prenatal growth is divided into 2 phases 1 Embryonic growth from conception to 8 weeks 2 Fetal Growth From 8 weeks to birth Embryonic Development Development begins with the fusion of two sex cells an ovum from the female and a spermatozoon from the male The genes direct the continuous development of the embryo in a precise and predictable pattern The number of cells increases and the cells differentiate to form speci c tissues and organs The process occurs in a predictable time line Fetal Development The fetal stage from 8 weeks to birth is characterized by further growth and cell differentiation of the fetus leading to functional capacity This continued growth of the organs and tissues occurs in 2 ways 1 Hyperplasia An increase in the absolute number of cells 2 Hypertrophy An increase in the relative size of an individual cell If you examine the landmarks of growth carefully You will also see that growth tends to proceed in two directions One direction is cephalocaudal meaning that the head and facial structures grow fastest followed by the upper body and then by the relatively slowgrowing lower body At the same time growth is proximodistal in direction meaning the trunk tends to advance then the nearest parts of the limbs and nally the distal parts of the limb Body weight increases and the body tissues grow steadily with the rat of growth increasing at about 5 months and continuing at that rapid rate until birth Kin 360 Chapter 5 of textbook notes KIN 360 Chapter 5 notes from the textbook Development of the skeletal system The skeletal system de nes an individual s structure It is not however a hard and static structure it is living tissue It undergoes considerable change over the life span and re ects the in uence of both genetic and external factors Early development of the skeletal system 0 There are two types of ossi cation centers 0 Primary ossi cation centers The primary ossi cation centers appear in the midportions of the long bones such as the humerus upper arm and femur thigh and begin to form bone cells starting at the fetal age of 2 months The bone shafts ossify outward in both directions from these primary centers until by birth the entire shafts are ossi ed 0 Secondary ossi cation centers Postnatal bone growth in length occurs at quotsecondary ossi cation centersquot at the end of the bone shaft A secondary center can also be called the epiphyseal plate aka growth plate or pressure epiphysis The epiphyseal plate has many cellular layers where cartilage cells form grow align and nally erode to leave new bone in place Bone is thus laid down at the epiphyseal plates to increase length of the bone 0 The process of laying down new bone depends on adequate blood supply Any injury that disturbs this blood supply threatens the bone s normal growth in length In contrast to the long bones small round bones such as those in the wrist and ankle simply ossify from the center outward Growth at the ossi cation centers ceases at different times in different bones At the epiphyseal plates the cartilage zone eventually disappears and the shaft or diaphysis of the bone fuses with the epiphysis Once the epiphyseal plates of a long bone fuse the length of the bone is xed Almost all epiphyseal plates are closed by age 18 or 19 0 While the long bones are growing in length they also increase in girth a process called appositional bone growth Girth is increased by the addition new tissue layers under the periosteum a very thin outer covering of the bone much like a tree adds to its girth under its bark There are also epiphyses at the sites where the muscles tendons attach to bones They are called quottraction epiphysesquot A familiar condition that occurs during the growth period in some youths quotOsgood schlatter diseasequot This is an irritation of the traction epiphysis where the patellar tendon attaches to the shin bone below the knee Overuse injuries to traction epiphyses during the growth period can threaten the painfree movement at a joint in later life For example a traction epiphysis near the elbow can be inured by repeatedly and forcefully pronating the forearm as in throwing The Skeletal Svstem in Adulthood and Older Adulthood The skeletal structure itself changes little in young adulthood but bone undergoes remodeling throughout the life span Old bone is replaced by new bone In youth new bone is formed faster than older bone is resorbed allowing for growth In adulthood bone formation begins to slow and eventually cannot keep pace with resorption The result is a loss of bone tissue starting as early as the mid205 and averaging about 1 of bone mass per yeah Bone composition also changes over the life span Children have essentially equal amounts of inorganic and organic components in their bone tissue but older adults have seven times more inorganic material making the bone more brittle and subject to micro fracture Osteoporosis can also lead to micro fractures of the vertebrae in the spine and eventually vertebrae may even collapse resulting in a dramatic change of skeletal structure in which the rib cage collapses forward with the lower edge resting on the pelvis so that the posture becomes stooped and standing height is notably reduced Earlv deve0pment of the muscular svstem Muscle bers cells grow during prenatal life by hyperplasia an increase in the number of muscle cells and by hypertrophy an increase in muscle cell snze At birth muscle mass accounts for 23 to 25 of body weight Muscle cells grow in both diameter and length The amount of increase in muscle ber diameter is related to the intensity of muscle activity during growth Naturally muscles must also increase in length as the skeleton grows and this increase is accomplished through the addition of sarcomeres the contractile units of muscle bers at the muscle tendon junction as well as through the lengthening of the sarcomeres Muscle ber types Human muscle consists of three main types of bers type lsowtwitch bers which are suited to endurance activities 0 type Ila and llb fasttwitch bers which are suited to intense shortduration activities 0 At birth approximately 15 of the muscle bers have yet to differentiate into 0 Type 0 Type lla 0 type llb bers 0 15 of type II bers are not clearly lla or llb types The muscular system in adulthood and older adulthood Body composition begins changing in young adulthood with the proportion of lean body weight decreasing most often as a result of fat weight increasing Only 10 of skeletal muscle mass is lost on average between the midZos and age 50Changes in diet and physical activity level are probably responsible for this shift in body composition The loss in number of bers is small before the 505 only about 5 of the adult number but more rapid thereafter amounting to a loss in the number of muscle bers after age 50 approximately 35 Fibers do not seem to decrease in size until the 705 all three types of muscle bers or whether type II bers undergo a greater loss than type bers do Bone and muscle mass are related to one another throughout the life span Cardiac muscle Cardiac muscle grows by hyperplasia and hypertrophy The right ventricle is larger than the left ventricle at birth but the left ventricle catches up after birth by growing more rapidly than the right so that the heart soon reaches adult proportions The hear generally follows the sigmoid pattern of whole body growth including a growth spurt in adolescence such that the ration of heart volume to body weight remains approximately the same throughout growth Early development of the adipose system The amount of adipose tissue increases in early life It rst appears in the fetus at 35 months and increases rapidly during the last 2 prenatal months Despite this late prenatal increase Adipose tissue accounts for only 05kg11 of body weight at birth After a rapid increase of fat during the rst 6 postnatal months fat mass increases gradually until age 8 in both boys and girls ln boys adipose tissue continues to increase gradually through adolescence but girls experience a more dramatic increase As a result adult women have more fat weight than adult men with averages of 14kg and 10kg respectively Fat weight during growth increases by both hyperplasia and hypertrophy but cell size does not increase signi cantly until puberty Fat Distribution oThe distribution of fat in the body changes during growth During childhood internal fat fat around the viscera increases faster than subcutaneous fat fat under the skin which actually decreases until age 6 or 7 Adipose tissue in Adulthood and older adulthood 0 Both sexes tend to gain fat weight during the adult years re ecting changes in nutrition and activity level Body fat redistributes with aging Subcutaneous fat on the limbs tends to decrease while internal fat in the abdomen tends to increase Development of the endocrine svstem The cells of a living being must be precisely regulated for their content and temperature The control systems regulating the cells of the body are the nervous system and endocrine system so it is not surprising that they play a major role in growth and maturation The endocrine system exerts its control over speci c cellular function through chemical substances called hormones Those secreted by the hypothalamus in the brain regulate the pituitary gland which in turn regulate the adrenal gland the thyroid gland and the release of sex hormones Early development of the Endocrine system 0 The endocrine system s regulation of growth is a complex and delicate interaction of hormones genes nutrients and environmental factors In fact hormone lvels must be delicately balanced Either an excess or a de ciency may disturb the normal process of growth and development 0 There are 3 hormones in the endocrine system that all promote growth in the same way These 3 hormones stimulate protein anabolism constructive metabolism Resulting in the retention of substances needed to build tissues There are speci c times in the growth period when one of these hormones may play a critical role in growth 0 Growth hormone I Growth hormone in uences growth during childhood and adolescence by stimulating protein anabolism so that new tissue can be built I Growth hormone is secreted by the anterior pituitary gland which in turn is stimulated by the hypothalamus I A de ciency or absence of GH results in growth abnormalities and in some cases the cessation of linear growth 0 Gonadal Hormone I The gonadal hormones affect growth and sexual maturation particularly during adolescence by stimulating development of the secondary sex characteristics and the sex organs The androgens speci cally testosterone from the testes and androgens from the cortex of the adrenal glands hasten fusion of the epiphyseal growth plates in the bones Thus these hormones promote skeletal maturationfusion at the expense of linear growth this explains why early measurers tend to be shorter in stature than later matures I Androgens also play a role in the adolescent growth spurt of muscle mass by increasing nitrogen and protein synthesis I This spurt is more pronounced in young men than in young women because men secrete both testosterone and adrenal androgens whereas women produce only the adrenal androgens I In women the ovaries and the adrenal cortex secrete estrogens Increase estrogen secretin during adolescence as with androgens speeds epiphyseal closure but estrogen also promotes fat accumulation primarily in the breasts and hips Men and women both have estrogen and testosterone but in very different proportions o Insulin Insulin has an indirect role in growth Insulin is produced in the pancreas insulin is vital to carbohydrate metabolism stimulating the transportation of glucose and amino acids through membranes Its presence also is necessary for the full functioning of Gh A de ciency of insulin can decrease protein synthesis which is detrimental at any time in life but especially during growth The endocrine system in adulthood and older aldulthood The Gradual imbalance theory The gradual imbalance theory suggest that over time the nervous system endocrine system and immune system gradually fail to function This gradual failure might occur at different rates in the three systems leading to imbalances between them and imbalances and reduced effectiveness within systems leave older individuals at increased risk of disease oThyroid function is an example it tends to decline with aging and thyroid disorders are more prevalent among older adults A longterm increase in thyroid hormone levels can be related to congestive heart failure It is therefore important for older adults to be screened for hyperthyroidism oln contrast insuf ciency of thyroid hormone Or hypothyroidism is associated with acceleration of aging systems Gonadal hormone levels also decrease with age Earlv deve0pment of the Nervous svstem Much of neurological development occurs very early in the life span The course of neurological development is a prime example of the interplay of genetic and extrinsic factors Prenatal growth of the Nervous system oln general the formation of immature neurons their differentiation into a general type and their migration to a nal position in the nervous system occur prenatally The new neurons also travel to a nal destination during the prenatal period Some from the brain stem which controls heartbeat and breathing some the cerebellum which controls posture and some the cerebral cortex where perception and thought take place 0 Generally neurons are in their nal location to which they migrate in this case a part of the brain where visual information arrives The migration process is vital too normal brain development oOnce the neurons are in place they grow an axon along a chemical trial to a general destination in order to connect to other neurons forming the brain s circuitry of about 100 trillion connections or quotsynapsesquot Because of the overproduction of neurons axons compete for the chemical trails Some axons and their neurons die off The neurons re electrical impulses that strengthen some of the connections between neurons oThe neurons ring is somewhat random prenatally but more organized as the fetus and later the infant receive input from the environment Thus there is a natural pruning process of both neurons and their branches and connections Weak or incorrect connections are sacri ced to make the neural network more ef cient Postnatal growth of the Nervous system 0 At birth the brain is about 25 of its adult weight Brain growth increases rapidly after birth and reaches 80 of adult weight by age 4 Then it enters a period of steady growth through adolescence The rapid early growth re ects an increase in the size of the neurons further branching to form synapses and an increase in glia and myelin Brain 0 Injury to the left side of the cerebral cortex early in life leads to de cits in language ability There is also increasing evidence that an infant s early life experiences in uence development of the nervous system Greenough and colleagues found that rats raised with much stimulation grew signi cantly more synapses than those raised without stimuli The same pattern holds for humans Learning is one of the most signi cant extrinsic factors in uencing postnatal development of the nervous system We now know that the brain restructures itself with learning Structures The spinal cord and lower brain structures are more advanced at birth than are the higher brain structures Lower brain centers involved in vital tasks such as respiration and food intake are relatively mature Lower brain centers also mediate many re exes and reactions and these automatic movement response dominate the fetus the newborn s movements
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