KIN 4512 module 5

Postnatal Neural Development •Experience plays a significant role in increasing synaptic connection •Our neural network becomes more efficient with experience •Strengthening some connections (activated most frequently) •Weakening (pruning) others (if the connections are not used) •Romanian orphan natural experiment (from last lecture?) Institutionalized children show decreased white and gray matter, as compared to children who had never been institutionalized

Experience is incredibly important to increasing and refining synaptic connections. Our neural network becomes more efficient with experience. It reinforces or strengthens some connections that have been activated most frequently ... and weakens or "prunes" other rarely or unused connections. Just like a gardener pruning a bush. If you remember back to the infants institutionalized in Romanian orphanages from the last lecture, the children were institutionalized during a rapid rate of neural growth. As expected, institutionalized children exhibited decreased white and gray matter, as compared to typical children. Further, researchers found that children institutionalized through toddlerhood exhibited the most severe impairments, which encompasses a large portion of rapid neural growth. The children with the least severe impairments were typically only institutionalized through 6 months of age, with plenty of time for enrichment to ameliorate the effects of institutionalization.

•Why effects of aging? •With advancing age, more neural network link breaks cause detours; thus processing time for a signal gets increasingly longer (Cerella 1990) • •Extrinsic factors which can ameliorate the effects of aging: •Exercise: Promotes improved cognitive function and has neuro-protective effects and immunological benefits (Beurskens & Dalecki, 2017) •Early enrichment: Cognitive enrichment à protective effects of age-related cognitive decline later in life (Milgram et al., 2006) •Diet: mild food restriction à Neurons resist dysfunction and death of diseases, such as Alzheimer's, Parkinson's, Huntington's, and stroke (Mattson, 2000)

For example, exercise promotes improved cognitive functioning, has neuroprotective effects, and immunological benefits. I know we are all excited to hear that, considering we are all interested in movement and exercise. Enrichment early in life leads to protective effects of age-related cognitive decline later in life, underscoring the absolute importance of that early period of neural development. Also, mild food restriction induces a resistance to the neural dysfunction and death related to diseases, such as Alzheimer's, Parkinson's, Huntington's, and stroke. Unfortunately, the mechanisms and effects of aging on our brains is not well understood, so researchers are unsure of why.

Endocrine System •Plays role in regulating growth through hormones •Hormone - a chemical substance used to control or regulate body functions • •Excess or deficiency of hormones can alter growth

The endocrine system plays a role in regulating growth through hormones, A hormone is a chemical substance used to control or regulate body functions Depending on the hormone and function it regulates, an excess or deficiency of the hormone alters growth. Below I've copied 2 videos, describing the endocrine system, and how hormones work.

Postnatal Neurological Growth •Brain growth increases rapidly after birth •At birth, the brain is 25% of adult weight •At 4 years, the brain is 80% of adult weight •Rapid early growth reflects: •Hypertrophy: Increases in size of neurons •Branching to form synapses •Increases in glial cells and myelin •Stimulation of learning (experience) increases number of synaptic connections

The high rate of growth of the nervous system continues following birth. An infant's brain is 25% of an adult weight, and 4-year-olds are 80% of an adult's brain. Early postnatal growth is hypertrophy, formation of synapses, and increases in glial cells and myelin. Stimulation of learning and experiences increases the number of synaptic connections.

Muscle Fiber Type The adult muscle is composed of slow twitch and fast twitch fibers. Slow twitch fibers are good for endurance activities, ...while fast twitch fibers are intense short-duration activities. 15% of fibers are undifferentiated into slow versus fast twitch fibers at birth, and by age 1, fiber type is similar to adult distributions. The exact proportions of slow versus fast twitch fibers vary between individuals.

•Adult muscle is composed of slow and fast twitch fibers •Slow twitch fibers (Type I) - good for endurance activities •Fast twitch fibers (Type IIa, IIb) -intense short-duration activities •Differentiation •At birth, 15% of fibers are undifferentiated •By age 1, distribution of muscle fiber type is similar to adult distributions •Exact proportions vary between individuals

Aging: Alzheimer's Dementia Alzheimer's dementia is a very common disease of aging, accounting for 60-80% of all dementia cases. It is a type of progressive dementia causing problems with cognition, memory, and behavior. Although our understanding of Alzheimer's dementia is still in its infancy, researchers are starting to find that extrinsic factors impact the rate of decline. An unexpected finding was that lifelong bilingual adults were protected against the effects of Alzheimer's dementia, as compared to monolingual adults. The proposed reason is that bilingualism encourages cognitive reserve, which resists brain damage. Increases in cognitive reserve slows cognitive decline and delays in neurodegeneration.

•Alzheimer's dementia •Accounts for 60-80% of all dementia cases •A type of progressive dementia causing problems with cognition, memory, and behavior •Bilingual vs. monolingual •Adults practicing lifelong bilingualism were protected against some effects of Alzheimer's dementia, as compared to monolingual adults (Perani et al., 2017)

Skeletal System (Early Development) Ossification begins at the primary ossification centers at 2 months gestational age. A primary ossification center is the area in the midportion of the shafts of long bones, where bone cells are initially formed. Ossification begins starting with the cartilage model bones of the fetal skeleton, from the center outward. By the infant's birth, shafts of long bones are completely ossified, although not all parts of the skeletal structure are ossified.

•At 2 months gestational age, ossification begins at primary centers in the midportions of long bones •Primary Ossification Center - area in the midportion of the shafts of long bones where bone cells are formed •Cartilage-model bones of the fetal skeleton begin ossifying, from the center outward, to form bone shafts

The distribution of fat shifts across development. Children have more visceral fat, than subcutaneous fat. From 6-7 through 12-13 years of age, subcutaneous fat increases in both males and females. Then, males and females diverge in their rate of change for fat. After 12 years, males and females differ in their amount of subcutaneous fat in their extremities. Males sharply decrease, while females continue a consistent rate of increase until 17 years of age. After 13 or 14 years of age, males stabilize their subcutaneous fat in their trunk, while females again continue a consistent rate of increase.

•Children have more visceral(internal)than subcutaneous (external) fat Subcutaneous fat increases from age 6 or 7 years until age 12 or 13 in males and females Subcutaneous fat then continues to increase in females, and change rate of increase for males

This concludes our lecture on the Development and Aging of Body Systems.

•Different body systems interact and influence each other •When focusing on the development of one body system, we should do so in context of the other systems •There are periods where changes in body system(s) are more rapid •More sensitive to influence of extrinsic factors •Development of these systems can impact motor development in different ways.

Skeletal System (Growth Cessation) Growth at the epiphyseal plates stops at different times for different bones and different populations of people. For example, epiphyseal plate closure occurs by age 15 for females and 18 for males. Appropriate levels of exercise encourage normal epiphyseal plate closure growth, while under and over exertion can lead to abnormal development.

•Growth at the epiphyseal plates stops at different times for different bones •Closure occurs at different rates for different populations •All bones are typically closed by age 15 for females and age 18 for males •Level of exercise à normal epiphyseal plate closure growth.

Why is the study of physical growth important to us?

-Physical size changes motor skill acquistition and performance - Determine typical growth patterns ->> Deviation from normal trajectory may be first indiciator of problems- physical, psychological, etc. - Determine constraints on motor development and performance One reason, is because our physical size changes motor skill acquisition and performance. We also need this information to determine typical growth patterns. Without knowledge of typical growth, we may not be able to identify what is uncommon or common. We also use this information to determine constraints on motor development and performance.

Adipose Tissue in Adulthood •Re-distribution in body fat •Subcutaneous fat on the limbs tend to decreases, while visceral/internal fat tends to increase •Higher visceral fat à at risk for disease • •Both men and women tend to gain fat during adulthood, not inevitable •Intrinsic: changes in injury, health condition •Extrinsic: nutrition/diet, activity

: Body fat re-distributes in adulthood. Subcutaneous fat on the limbs tend to decrease, while visceral fat tends to increase. Since visceral fat is less healthy for the body, it can put older adults at greater risk for poor health, like metabolic syndrome, diabetes, or heart disease. Males and females gain fat at relatively similar rates during adulthood, although this increase in fat is not inevitable. Multiple factors change across the lifespan Intrinsic factors, like injury, health condition, pregnancy, mobility Or extrinsic factors, like nutrition, diet, activity, financial circumstances, or community.

Gonadal Hormones •Secreted by gonads •Influence on growth, sexual maturation (sex organs, secondary sex characteristics) •Androgens •Secreted by testes (boys), adrenal glands (boys, girls) •Promote growth of muscle mass •Estrogen •Secreted by ovaries (girls), adrenal cortex (girls, boys) •Promotes accumulation of fat •Androgens and estrogens both hasten epiphyseal growth plate closure •...which is why early maturers tend to be shorter, than late maturers

Gonadal hormones are secreted by the gonads. They have a big influence on growth, but especially sexual maturation of sex organs and secondary sex characteristics. They are secreted by the testes for males and the adrenal glands for both sexes. Androgens promote the growth of muscle mass, which is one reason why males tend to have higher muscle mass, than females. Estrogen is secreted by the ovaries for females and the adrenal cortex for both sexes. They promote the accumulation of fat, which is one reason why females tend to continue to accumulate fat during adolescence, whereas males decrease fat. Androgens and estrogens both hasten epiphyseal growth plate closure, which is why early maturers tend to be shorter, than late maturers.

Growth Hormone •Secreted by anterior pituitary •Necessary for normal growth •Deficiency can result in growth abnormality •Cessation of linear growth •(right) Man with Laron syndrome Picture (insensitivity to growth hormone) and his family

Growth hormone is secreted by the anterior pituitary gland. It is essential for normal growth, ...and a deficiency results in a growth abnormality, like A cessation of linear growth. On the right is a picture of a man with Laron syndrome, which is an insensitivity to growth hormone. You can see that his stature is considerably shorter, than might be expected for an adult male of his age.

Hand and Wrist X Rays to Assess Skeletal Growth

Here are hand and wrist X-RAYS of children at different ages, which show different skeletal growth. The graph on the left shows how males and females might look from 3-4 years, and the graph on the right demonstrates how males and females typically are from 10.5-13 years. You can see the bones are longer and larger in the older children. You can also see more space in between bones and that the epiphyseal plates are less closed in younger children.

•Minimal muscle loss through adulthood until 50 years of age (~10%) •Sarcopenia - loss of muscle mass •Muscle mass can increase or decrease due to extrinsic factors (health, exercise, activity, etc.) • •By 80 years, an average of 30% of muscle mass is lost. •Decrease in number and size of muscle fibers. •Fast twitch fibers undergo a greater loss, than slow twitch (Nilwik et al., 2013) •More fat and connective tissue in limb muscles, than younger adults (Evans & Lexell, 1995). • •Is there anything that can be done to prevent or reduce these declines?

In adulthood, there is sarcopenia, or a loss of muscle mass. The loss of muscle mass is approximately 10% until 50 years of age. But, by 80 years of age, 30% of muscle mass is lost on average. Both the size and the number of fibers are lost, with fast twitch fibers undergoing a greater loss, than slow twitch. Additionally, limb muscles are 25-35% smaller and have significantly more fat and connective tissue, than younger adults. So what can be done to prevent or reduce these declines? Research has shown that changes in activity can reduce the amount of muscle loss. Exercise like resistance or strength training are especially effective. Many adults who lose muscle mass, also gain fat. Reducing the amount of fat on your body through diet and exercise can help maintain this muscle, and treat underlying risk factors for sarcopenia, like metabolic syndrome.

Insulin •Produced in the Pancreas •Vital for carbohydrate metabolism •Necessary for full functioning of Growth Hormone •Especially important during growth •Deficiency can decrease protein synthesis • •Insulin Disorder: Diabetes •Type 1 diabetes results from the pancreas's failure to produce enough insulin due to loss of beta cells. •Type 2 diabetes begins with insulin resistance, a condition in which cells fail to respond to insulin properly. •Gestational diabetes: pregnant women without a prior history of diabetes develop high blood sugar levels

Insulin is produced by the pancreas. It is vital both for the metabolism of carbohydrates and for full functioning of the growth hormone. Insulin is especially important during growth, as a deficiency can decrease protein synthesis. The most commonly known insulin disorder is diabetes. Type 1 diabetes results from the pancreas' failure to produce enough insulin, and type 2 diabetes results from insulin resistance. The third type, gestational diabetes, occurs when pregnant women without a prior history of diabetes develop high blood sugar levels.

Endocrine System in Older Adults •Imbalances may develop between nervous, endocrine, and immune systems •May result in an increased risk of disease •Thyroid disorders are quite prevalent •Long term increase → related to congestive heart failure •Insufficiency → acceleration of aging systems •Decreasing gonadal hormone levels are associated with loss of bone and muscle tissue

Later in adulthood, imbalances may development between the nervous, endocrine, and immune systems. Thyroid disorders are quite prevalent in older populations and put older adults at increased risk of disease. Long term increase or insufficiency are related to congestive heart failure or acceleration of aging, respectively. Decreased gonadal hormone levels can lead to losses of bone and muscle tissue.

•Heart rate variability (HRV) indicates cardiac health •(defn) variation in the time interval between consecutive heartbeats in milliseconds •Higher HRV à indicative of lower cardiac risk and better outcomes (lower morbidity, mortality, improved psychological well-being • •Assessed older adults for indices of HRV and physical activity. (Soares-Miranda et al. 2014) •0ms are unhealthy, 50-100 have compromised health, >100 are healthy

Let's connect this body system to development and aging by looking at a study linking cardiac risk and physical activity in older adults. Heart rate variability is the variation in the time interval between consecutive heartbeats in milliseconds. Typically a higher value of heart rate variability is indicative of lower cardiac risk and better outcomes, including more adaptive stress response, lower morbidity, or lower mortality). Soares-Miranda et al assessed older adults for indices of heart rate variability and coupled with the amount of physical activity, operationally defined as walking distance.

•Achondroplasia •A disorder of bone growth that prevents changing of cartilage to bone (cartilage growth defects) •Most common form of disproportionate dwarfism •Common structural and functional differences, from typical bodies •Shorter fingers •Shorter stature •Enlarged head and forehead •Limited range of motion at elbows •Atypical spine structure (e.g., lordosis of spine: lordotic curve arches too far inward) •Different body proportions (shorter limbs/longer trunk/larger head)

Let's do a quick spotlight on motor development for children with achondroplasia. It is a disorder of bone growth that prevents cartilage being changed to bone and is the most common form of disproportionate dwarfism. Some common structural differences are shorter fingers and stature, an enlarged head, limited range of motion at the elbows, and atypical spine structure. The overall body proportions are shorter limbs with a longer trunk and a larger head.

•Older adults with greater HRV exhibited higher levels of physical activity • • •Adults who increased walking distance or pace over 5 years following the study improved their HRV, as compared to those who decreased.

Let's look at the graph on the right. The X axis is walking distance in blocks per week. Y axis is SSDN, or the gold standard measure of heart rate variability, where a score of <100 indicates compromised health and >100 indicates healthy. The researchers found a positive relation between walking distance and heart rate variability. Adults who walked a longer distance, had a higher SSDN. If you look at the graph, the lowest SSDN values on the Y axis are close to the 100 clinical cut point, differentiating people with compromised health with healthy. In the next 5 years, adults who consistently walked more improved their heart rate variability, as compared to those who decreased their walking distance. Although it is not conclusive, this finding indicates that physical activity, particularly consistent physical activity, may positively impact cardiac health in aging populations.

The Nervous System •Most neurological development occurs very early in the life span. •Genes -> director of nervous system development, •Extrinsic factors exert influence (synaptic connections)

Most neurological development occurs very early in the life span. Initially, nervous system development is seen directed by genes, and extrinsic factors exert influence, especially in the formation of synaptic connections. Below I've embedded a video on the nervous system, if you need a review.

Muscles increase in diameter and length by the addition of: Myofibrils (basic unit of muscle cells) Sarcomeres (basic unit of striated muscle tissue)

Muscles increase their length and diameter through the addition of myofibrils and sarcomere. Myofibrils are the basic unit of muscle cells and sarcomeres are the basic unit of striated muscle tissue If you would like a quick, basic review on muscles, please click this video.

Nervous System •Myelin - lipid-rich substance that surrounds the axon of some nerve cells, forming an electrically insulating layer. Myelination of axons allows... Faster conduction of neural impulses Impulses follow direction of conduction Myelin sheath breakdown -> tremors, loss of coordination, paralysis

Myelin is a lipid-rich substance surrounding the axon of some nerve cells. Myelin forms an electrically insulating layer, and It allows for faster conduction of neural impulses. If there is a breakdown in the myelin sheath, there can be a loss of coordination, paralysis, or tremors.

Adipose System •Adipose tissue = fat •Stores energy •Provides protection and insulation •Fat types •Internal/visceral fat: internal fat around the viscera •Subcutaneous fat: fat under the skin •Fat is not inherently good or bad. •Some fat is needed for healthy development.

The adipose system is composed of adipose tissue, i.e., fat. Fat is necessary for energy storage, insulation, and protection. Fat is broken into 2 types. It is either visceral fat, the internal fat around the viscera, or subcutaneous fat, the fat under the skin. Subcutaneous fat is the most visible fat from the outside. It is important to note that fat is not inherently good or bad. Fat is necessary for healthy development and living; however, an excess of fat or too much visceral fat, can be detrimental to one's health.

Prenatal Neural Development •Process includes formation of neuron, differentiation into type and migration. •250,000 / minute, 200 billion formed •Neurogenesis - division and propagation of neurons from stem cells. •Most active in embryonic stage •After migration, axon forms to carry signals to other cells (neural, glandular, organ, muscle) •Teratogens may disturb normal migration and branching •Effects of teratogens? Spontaneous abortion / unviability, epilepsy, autism, dyslexia, lower IQ, etc. (higher rate of growth=negative influence will be more dmanaging)

Neurons are forming, differentiating into types, and migrating to their location. Neurons form at an incredibly rapid rate - 250,000 per minute! Whoa. Neurons divide and propagate from stem cells, in a process called neurogenesis. Neurogenesis is most active in the embryonic stage. Once neurons have migrated to their proper location, then axons develop and begin signaling to other neural, organ, gland, or muscle cells. During the embryonic stage, neural development is very sensitive to teratogenic or extrinsic effects. They can disturb normal migration and branching. Keep in mind, the embryonic stage has a rapid rate of neural growth, so the influence of teratogens and extrinsic factors early in neural development can have a huge impact on the burgeoning nervous system. Thus, damage or faulty migration can have large repercussions, such as epilepsy, lower IQ, spontaneous abortion of the organism, etc. This is the main reason why the CDC recommends all women of reproductive age take folic acid, because many women find out they're pregnant well into the embryonic stage, after which a folate deficiency could have affected the embryo's nervous system.

Nervous System •Neurons - cells of the nervous system that receive and transmit information •Synapse - connection between 2 neurons •Connection is made by the release of neurotransmitters from an axon

Neurons are the cells of the nervous system which receive and transmit information. Between neurons are synapses. This gap between the neurons is where neurotransmitters are released from the axon to transmit information between neurons.

Achondroplasia -Atypical and delayed patterns of motor development

Since children with achondroplasia have a different body proportion to children with typical development, they exhibit atypical patterns of motor development. The prone position is more difficult to maintain with an enlarged head, so infants with achondroplasia are more likely to locomote by scooting backwards on their heads in supine. Independent sitting is more challenging to maintain with a larger head to hold up and shorter limbs which may not be long enough to support the position. Also, structural differences in the hands, such as trident hand mentioned earlier in the lecture, can lead to differences in strategies for grasping a writing utensil.

•Why effects of aging? •With advancing age, more neural network link breaks cause detours; thus processing time for a signal gets increasingly longer (Cerella 1990) • •Extrinsic factors which can ameliorate the effects of aging:

So, you might be wondering, WHY do we experience age-related effects of aging in the nervous system? Researchers speculate that as neural network links breakdown across time, the brain needs to re-route these connections to maintain the same functionality. These detours lead to longer and longer processing times, since the signal has to travel farther and farther through the network. Thus, people who are aging may still be capable, but they need greater time to process. As we know, some abilities are very time sensitive, such as driving or reacting to a balance loss, so age-related changes in the brain impact their daily lives. However, not all is lost. There are a number of extrinsic factors which can ameliorate the effects of aging, including the usual suspects, exercise, diet, health, and experience.

Nervous System in Older Adults •Neural connections stabilize growth later in life... •...however neuronal connections can change over the lifespan (i.e., exhibit plasticity) Aging in the nervous system Loss of neurons, dendrites, synapses, neurotransmitters, and myelin ...however, neurogenesis has been observed in some brain areas (Verret et al. 2007)

The rate of neural growth stabilize later in life... However, it should be noted that the brain is still plastic across the lifespan. Aging in the nervous system means a loss of neurons, dendrites, synapses, neurotransmitters, and myelin. However, again, it should be noted that neurogenesis has been observed in some areas of the brain. Meaning that neural cells and connections typically decrease during the aging period, but brains may be capable of neurogenesis.

•Smooth- involuntary, non-striated muscle •In organs: stomach, intestines, bladder, uterus, skin, etc. •Cardiac - involuntary, striated muscle •In the heart •Skeletal - voluntary, striated muscle •The muscles you "think" of when you hear muscles, attached to bones by tendons

There are 3 muscle types. Smooth muscles, which are involuntary, non-striated muscles. This muscle is in organs, like the stomach, bladder, or uterus. Then cardiac muscle, which are involuntary, striated muscles. This muscle type is in, well you guessed it, the heart. Finally, skeletal muscle, which include voluntary, striated muscle. These are the muscles you "think" of when you hear about muscles, ones attached to bones by tendons, ones controlling movement, etc.

Thyroid Hormones •Secreted by thyroid gland (duh, right?) •Regulation of metabolism •Triiodothyronine (T3) and thyroxine (T4) •Thyroid function declines with aging •Why changes in weight and thyroid disorders occur in older adults •Disorders •Hyperthyroidism - increases levels of thyroid hormone •Hypothyroidism - insufficiency of thyroid hormone

Thyroid hormone is secreted by ...you guessed it ... the thyroid gland! Thyroid hormone is responsible for metabolism. Thyroid function tends to decline with aging, which is one additional reason why weight gain and increased prevalence of thyroid disorders occurs in older adults. Two disorders are related to thyroid functioning: hyperthyroidism and hypothyroidism.

Now let's compare a normal wrist X-ray to an atypical wrist X-ray of a trident hand.

Trident hand is a hand in which the fingers are of nearly equal length and deflected at the first interphalangeal joint, giving a "trident" or fork-like appearance to the hand. This structural characteristic is common in people with the physical growth disorder, achondroplasia. In the X-rays, you can see the typical hand has longer and larger bones, than the trident hand. The epiphysis is more angular and irregularly shaped, than the typical hand.

Adipose System Growth As with many body systems, adipose tissue increases early in life. At birth, fat only accounts for 1.1 pounds of body weight. Increases in adipose tissue occurs differently for different groups of people. For example, females increase fat at a higher rate, than males do. Females need a higher proportion of fat in order to maintain reproductive functioning. Adipose tissue growth is quite variable between individuals. You may remember this fact in our growth lecture, as we discussed how increases in weight followed a sigmoid curve on average, but was highly variable. That is because increases in fat closely relate to one's lifestyle. Body composition changes across development and early body composition may be relevant or predict later body composition ... but a chubby baby is not destined to be a chubby child. It depends on what factors cause levels of fat or what factors are changed by an increased proportion of fat.

•In early life, the amount of adipose tissue increases •Birth: Only accounts for 1.1lbs of body weight •Increases in adipose tissue differs for different people •Adolescence and puberty: females increase fat more dramatically than males do •For reproductive function, females need these increases in fat •Growth in adipose is variable, based on the individual. •Chubby baby ≠ fat child •BUT early fat/diet is still relevant

Muscular System Muscle growth, like many types of growth, follows a sigmoid pattern Prenatal growth involves hyperplasia and hypertrophy... While postnatal growth largely involves hypertrophy.

•Muscle growth follows sigmoid pattern •Prenatal growth involves hyperplasia and hypertrophy •As a reminder: •Hyperplasia - an increase in the absolute number of cells •Hypertrophy - increases the relative sizes of individual cells •Postnatal growth mainly involves hypertrophy

Body Scaling and Motor Development OK, let's reflect on our knowledge of the skeletal system and our understanding of development. Namely Perception-action theory. Body scaling is when organisms assess the environment based on themselves, rather than an objective standard. In a study by Newell, McDonald, and Baillargeon, researchers thought that an individual's hand size changed movement patterns and hand use during development. They assessed 5-8 month-old infants and college-aged adults. They gave all participants cups of different diameters and marked whether participants used 1 or 2 hands. They found that the frequency of using 2 hands was higher at lower cup diameters for infants, than adults. Look at the graph. The x-axis is cup diameter in centimeters and the Y axis is the frequency of using a hand strategy in %. The lines with solid shapes were adults, and open shapes were infants. You can see that infants switched their use of 2 hands at lower cup diameters, than adults. See how the red line, indicating the increase in frequency of 2 hand use for infants increases sooner over cup diameter, than in the blue adult line for 2 hand use. And, you can see the slope of the infant 2 hand line is steeper than adults, meaning adults switched to consistent 2 hand use less quickly as a group, than infants did. They also found that frequency of number of digits and hands used in a grasp changed as a function of hand length AND cup diameter, regardless of population. In sum, participants with smaller hands used more digits in a grasp and were more likely to use 2 hands instead of one, over participants with larger hands. Thus, demonstrating that the participants assessed how to perform the action by their relative body size, i.e., body scaling.

•Remember body scaling? (Perception action theory) •Organisms assess the environment based on themselves, rather than an objective standard (Chapter 2) •Hand size changes movement patterns (Newell, McDonald, & Baillargeon, 1993) •Infants (5-8 mo) and adults •Participants reached for cups of differing diameters •Researchers marked whether they used 1 or 2 hands • •The frequency of using 2 hands was higher at lower cup diameters for infants, than adults (graph) •Frequency of # of digits and hands used in grasp changed as a function of hand length and cup diameter.

Following primary growth, secondary bone growth occurs in the secondary ossification centers. Typically, these sites are at the end of bones and lead to an increase in the bone's length. These ossification centers are called epiphyseal plates, growth plates, or pressure epiphyses

•Secondary Ossification Centers - sites where bone growth occurs following primary growth •Typically, at the ends of bones and lead to an increase in length •These centers are called epiphyseal plates, growth plates, or pressure epiphyses

Module 5 Development and Aging of Body Systems Body Systems

•Skeletal - an individual's "structure" •Muscular - allows an individual's movement •Adipose - energy storage, insulation, and protection (i.e., fat) •Endocrine - exerts control over certain cellular functions using hormones •Nervous - controls movement, cognition, and speech

Skeletal Structure in Adulthood Throughout most of adulthood, the skeletal structure changes very little until the aging period. Bone density decreases for normal age-related reasons, but also because of diseases, like osteoporosis. According to the Mayo clinic, living bone is constantly being replaced in a healthy adult. Osteoporosis is when the creation of new bone doesn't keep up with the loss of the old bone, thus causing bone to become weak. As a result, osteoporosis leads to rib cage collapse, stooped posture, increased risk of fractures and reduced height. Bone loss is influenced by intrinsic and extrinsic factors, such hormone levels, and extrinsic factors, like diet and activity. Although osteoporosis affects all groups of people, older women past menopause, especially white and Asian women, are at highest risk for developing osteoporosis. A randomized clinical trial found that older men reversed normal age-related bone loss through weight-lifting or jumping exercises.

•Skeletal structure changes little until aging period or with disease •Osteoporosis leads to rib cage collapse, stooped posture, and reduced height •Extent of bone loss is influenced by hormone levels, diet, exercise / activity. •Hormone: Older women past menopause are at the highest risk for developing osteoporosis of all groups •Exercise / activity: Exercising, like weight-lifting or jumping, can reverse age-related bone loss in older men (Hinton, Nigh, & Thyfault, 2015)

Early in development, the embryo's structure is maintained with a cartilage model of the skeleton. For those who don't know what that is, wiggle the end of your nose to feel cartilage. At the ossification centers, bone is deposited at these cartilage model sites to form the organism's eventual skeletal structure.

•The embryo has a cartilage model of the skeleton •Initially, structure is maintained via cartilage •Ossification centers - cartilage model sites where bone is deposited

Cardiac muscle grows in a sigmoid pattern via hyperplasia and hypertrophy. The size of the heart and blood vessels are appropriate for body size in childhood and adolescence. During aging, the heart loses its ability to adapt to increased workloads. The exact reason for this is unknown. This decline may be due to muscle degeneration, decreased elasticity, changes in the fibers of the valves, or changes in activity in everyday life.

•The heart grows in a sigmoid pattern following birth •...by hyperplasia and hypertrophy • •Heart and blood vessel size à appropriate to body size in childhood and adolescence • •Aging: Heart loses its ability to adapt to increased workloads •Why? May be due to degeneration of heart muscle, decreased elasticity, changes in fibers of the valves, or (partly) lifestyle

Fat Distribution Across Childhood For example, young infants with a higher weight and subcutaneous fat levels have an increased risk of motor delay. Slining et al found that overweight infants were 1.8 times more likely to exhibit a motor delay, than infants with a typical weight. The researchers proposed a "cascade of risk." That, a higher weight infant needs greater strength to move their body, which leads to decreased activity in the infant, which translates to delays in motor control and strength. Then, motor delays and less activity causes a cycle of higher weight, lower strength, and decreased activity. Therefore, infants who are higher weight, but do not decrease their activity, are not likely to fall into this "cascade of risk."

•Young infants with higher weight and subcutaneous fat levels had an increased risk of motor delay. •Overweight infants were 1.8 times more likely to exhibit a motor delay, than infants with typical weight.