Results for "gray matter"

all nerves white and gray matter

gray matter and white matter (lecture 1)

White vs Gray Matter

Internal Anatomy and Fiber Systems of the Cerebrum: Gray Matter, Nuclei, and Connectivity

Gray Matter vs White Matter

NEUS 609 - Overview of the Nervous System I

NEUS 609 - Generation, Migration, & Survival of Neural Cells I

Neuron Parts + White/Gray Matter + Electrical Conductivity

Lab #4 - Spinal Cord - Gray Matter

Chapter 6: Adolescence Growth in Adolescence Puberty is a period of rapid growth and sexual maturation. These changes begin sometime l between eight and fourteen. Girls begin puberty at around ten years of age and boys begin approximately two years later. Pubertal changes take around three to four years to complete. Adolescents experience an overall physical growth spurt. The growth proceeds from the extremities toward the torso. This is referred to as distalproximal development. First the hands grow, then the arms, hand finally the torso. The overall physical growth spurt results in 10-11 inches of added height and 50 to 75 pounds of increased weight. The head begins to grow sometime after the feet have gone through their period of growth. Growth of the head is preceded by growth of the ears, nose, and lips. The difference in these patterns of growth result in adolescents appearing awkward and out-of-proportion. As the torso grows, so do the internal organs. The heart and lungs experience dramatic growth during this period. During childhood, boys and girls are quite similar in height and weight. However, gender differences become apparent during adolescence. From approximately age ten to fourteen, the average girl is taller, but not heavier, than the average boy. After that, the average boy becomes 223 both taller and heavier, although individual differences are certainly noted. As adolescents physically mature, weight differences are more noteworthy than height differences. At eighteen years of age, those that are heaviest weigh almost twice as much as the lightest, but the tallest teens are only about 10% taller than the shortest (Seifert, 2012). Both height and weight can certainly be sensitive issues for some teenagers. Most modern societies, and the teenagers in them, tend to favor relatively short women and tall men, as well as a somewhat thin body build, especially for girls and women. Yet, neither socially preferred height nor thinness is the destiny for many individuals. Being overweight, in particular, has become a common, serious problem in modern society due to the prevalence of diets high in fat and lifestyles low in activity (Tartamella et al., 2004). The educational system has, unfortunately, contributed to the problem as well by gradually restricting the number of physical education courses and classes in the past two decades. Average height and weight are also related somewhat to racial and ethnic background. In general, children of Asian background tend to be slightly shorter than children of European and North American background. The latter in turn tend to be shorter than children from African societies (Eveleth & Tanner, 1990). Body shape differs slightly as well, though the differences are not always visible until after puberty. Asian background youth tend to have arms and legs that are a bit short relative to their torsos, and African background youth tend to have relatively long arms and legs. The differences are only averages, as there are large individual differences as well. Sexual Development Typically, the growth spurt is followed by the development of sexual maturity. Sexual changes are divided into two categories: Primary sexual characteristics and secondary sexual characteristics. Primary sexual characteristics are changes in the reproductive organs. For males, this includes growth of the testes, penis, scrotum, and spermarche or first ejaculation of semen. This occurs between 11 and 15 years of age. For females, primary characteristics include growth of the uterus and menarche or the first menstrual period. The female gametes, which are stored in the ovaries, are present at birth, but are immature. Each ovary contains about 400,000 gametes, but only 500 will become mature eggs (Crooks & Baur, 2007). Beginning at puberty, one ovum ripens and is released about every 28 days during the menstrual cycle. Stress and higher percentage of body fat can bring menstruation at younger ages. Male Anatomy: Males have both internal and external genitalia that are responsible for procreation and sexual intercourse. Males produce their sperm on a cycle, and unlike the female's ovulation cycle, the male sperm production cycle is constantly producing millions of sperm daily. The main male sex organs are the penis and the testicles, the latter of which produce semen and sperm. The semen and sperm, as a result of sexual intercourse, can fertilize an ovum in the female's body; the fertilized ovum (zygote) develops into a fetus which is later born as a child. Female Anatomy: Female external genitalia is collectively known as the vulva, which includes the mons veneris, labia majora, labia minora, clitoris, vaginal opening, and urethral opening. Female internal reproductive organs consist of the vagina, uterus, fallopian tubes, and ovaries. The uterus hosts the developing fetus, produces vaginal and uterine secretions, and passes the male's sperm through to the fallopian tubes while the ovaries release the eggs. A female is born with all her eggs already produced. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the fallopian tubes. Females have a monthly reproductive cycle; at certain intervals the ovaries release an egg, which passes through the fallopian tube into the uterus. If, in this transit, it meets with sperm, the sperm might penetrate and merge with the egg, fertilizing it. If not fertilized, the egg is flushed out of the system through menstruation. Secondary sexual characteristics are visible physical changes not directly linked to reproduction but signal sexual maturity. For males this includes broader shoulders and a lower voice as the larynx grows. Hair becomes coarser and darker, and hair growth occurs in the pubic area, under the arms and on the face. For females, breast development occurs around age 10, although full development takes several years. Hips broaden, and pubic and underarm hair develops and also becomes darker and coarser. Acne: An unpleasant consequence of the hormonal changes in puberty is acne, defined as pimples on the skin due to overactive sebaceous (oil-producing) glands (Dolgin, 2011). These glands develop at a greater speed than the skin ducts that discharges the oil. Consequently, the ducts can become blocked with dead skin and acne will develop. According to the University of California at Los Angeles Medical Center (2000), approximately 85% of adolescents develop acne, and boys develop acne more than girls because of greater levels of testosterone in their systems (Dolgin, 2011). Experiencing acne can lead the adolescent to withdraw socially, especially if they are self-conscious about their skin or teased (Goodman, 2006). Effects of Pubertal Age: The age of puberty is getting younger for children throughout the world. According to Euling et al. (2008) data are sufficient to suggest a trend toward an earlier breast development onset and menarche in girls. A century ago the average age of a girl’s first period in the United States and Europe was 16, while today it is around 13. Because there is no clear marker of puberty for boys, it is harder to determine if boys are maturing earlier too. In addition to better nutrition, less positive reasons associated with early puberty for girls include increased stress, obesity, and endocrine disrupting chemicals. Cultural differences are noted with Asian-American girls, on average, developing last, while African American girls enter puberty the earliest. Hispanic girls start puberty the second earliest, while European-American girls rank third in their age of starting puberty. Although African American girls are typically the first to develop, they are less likely to experience negative consequences of early puberty when compared to European-American girls (Weir, 2016). Research has demonstrated mental health problems linked to children who begin puberty earlier than their peers. For girls, early puberty is associated with depression, substance use, eating disorders, disruptive behavior disorders, and early sexual behavior (Graber, 2013). Early maturing girls demonstrate more anxiety and less confidence in their relationships with family and friends, and they compare themselves more negatively to their peers (Weir, 2016). Problems with early puberty seem to be due to the mismatch between the child’s appearance and the way she acts and thinks. Adults especially may assume the child is more capable than she actually is, and parents might grant more freedom than the child’s age would indicate. For girls, the emphasis on physical attractiveness and sexuality is emphasized at puberty and they may lack effective coping strategies to deal with the attention they may receive. 226 Figure 6.4 Source Additionally, mental health problems are more likely to occur when the child is among the first in his or her peer group to develop. Because the preadolescent time is one of not wanting to appear different, early developing children stand out among their peer group and gravitate toward those who are older. For girls, this results in them interacting with older peers who engage in risky behaviors such as substance use and early sexual behavior (Weir, 2016). Boys also see changes in their emotional functioning at puberty. According to Mendle, Harden, Brooks-Gunn, and Graber (2010), while most boys experienced a decrease in depressive symptoms during puberty, boys who began puberty earlier and exhibited a rapid tempo, or a fast rate of change, actually increased in depressive symptoms. The effects of pubertal tempo were stronger than those of pubertal timing, suggesting that rapid pubertal change in boys may be a more important risk factor than the timing of development. In a further study to better analyze the reasons for this change, Mendle et al. (2012) found that both early maturing boys and rapidly maturing boys displayed decrements in the quality of their peer relationships as they moved into early adolescence, whereas boys with more typical timing and tempo development actually experienced improvements in peer relationships. The researchers concluded that the transition in peer relationships may be especially challenging for boys whose pubertal maturation differs significantly from those of others their age. Consequences for boys attaining early puberty were increased odds of cigarette, alcohol, or another drug use (Dudovitz, et al., 2015). Gender Role Intensification: At about the same time that puberty accentuates gender, role differences also accentuate for at least some teenagers. Some girls who excelled at math or science in elementary school, may curb their enthusiasm and displays of success at these subjects for fear of limiting their popularity or attractiveness as girls (Taylor et al/, 1995; Sadker, 2004). Some boys who were not especially interested in sports previously may begin dedicating themselves to athletics to affirm their masculinity in the eyes of others. Some boys and girls who once worked together successfully on class projects may no longer feel comfortable doing so, or alternatively may now seek to be working partners, but for social rather than academic reasons. Such changes do not affect all youngsters equally, nor affect any one youngster equally on all occasions. An individual may act like a young adult on one day, but more like a child the next. Adolescent Brain The brain undergoes dramatic changes during adolescence. Although it does not get larger, it matures by becoming more interconnected and specialized (Giedd, 2015). The myelination and 227 development of connections between neurons continues. This results in an increase in the white matter of the brain and allows the adolescent to make significant improvements in their thinking and processing skills. Different brain areas become myelinated at different times. For example, the brain’s language areas undergo myelination during the first 13 years. Completed insulation of the axons consolidates these language skills but makes it more difficult to learn a second language. With greater myelination, however, comes diminished plasticity as a myelin coating inhibits the growth of new connections (Dobbs, 2012). Even as the connections between neurons are strengthened, synaptic pruning occurs more than during childhood as the brain adapts to changes in the environment. This synaptic pruning causes the gray matter of the brain, or the cortex, to become thinner but more efficient (Dobbs, 2012). The corpus callosum, which connects the two hemispheres, continues to thicken allowing for stronger connections between brain areas. Additionally, the hippocampus becomes more strongly connected to the frontal lobes, allowing for greater integration of memory and experiences into our decision making. The limbic system, which regulates emotion and reward, is linked to the hormonal changes that occur at puberty. The limbic system is also related to novelty seeking and a shift toward interacting with peers. In contrast, the prefrontal cortex which is involved in the control of impulses, organization, planning, and making good decisions, does not fully develop until the mid-20s. According to Giedd (2015) the significant aspect of the later developing prefrontal cortex and early development of the limbic system is the “mismatch” in timing between the two. The approximately ten years that separates the development of these two brain areas can result in risky behavior, poor decision making, and weak emotional control for the adolescent. When puberty begins earlier, this mismatch extends even further. Teens often take more risks than adults and according to research it is because they weigh risks and rewards differently than adults do (Dobbs, 2012). For adolescents the brain’s sensitivity to the neurotransmitter dopamine peaks, and dopamine is involved in reward circuits, so the possible rewards outweighs the risks. Adolescents respond especially strongly to social rewards during activities, and they prefer the company of others their same age. Chein et al. (2011) found that peers sensitize brain regions associated with potential rewards. For example, adolescent drivers make risky driving decisions when with friends to impress them, and teens are much more likely to commit crimes together in comparison to adults (30 and older) who commit them alone (Steinberg et al., 2017). In addition to dopamine, the adolescent brain is affected by oxytocin which facilitates bonding and makes social connections more rewarding. With both dopamine and oxytocin engaged, it is no wonder that adolescents seek peers and excitement in their lives that could end up actually harming them. 228 Because of all the changes that occur in the adolescent brain, the chances for abnormal development can occur, including mental illness. In fact, 50% of the mental illness occurs by the age 14 and 75% occurs by age 24 (Giedd, 2015). Additionally, during this period of development the adolescent brain is especially vulnerable to damage from drug exposure. For example, repeated exposure to marijuana can affect cellular activity in the endocannabinoid system. Consequently, adolescents are more sensitive to the effects of repeated marijuana exposure (Weir, 2015). However, researchers have also focused on the highly adaptive qualities of the adolescent brain which allow the adolescent to move away from the family towards the outside world (Dobbs, 2012; Giedd, 2015). Novelty seeking and risk taking can generate positive outcomes including meeting new people and seeking out new situations. Separating from the family and moving into new relationships and different experiences are actually quite adaptive for society. Adolescent Sleep According to the National Sleep Foundation (NSF) (2016), adolescents need about 8 to 10 hours of sleep each night to function best. The most recent Sleep in America poll in 2006 indicated that adolescents between sixth and twelfth grade were not getting the recommended amount of sleep. On average adolescents only received 7 ½ hours of sleep per night on school nights with younger adolescents getting more than older ones (8.4 hours for sixth graders and only 6.9 hours for those in twelfth grade). For the older adolescents, only about one in ten (9%) get an optimal amount of sleep, and they are more likely to experience negative consequences the following day. These include feeling too tired or sleepy, being cranky or irritable, falling asleep in school, having a depressed mood, and drinking caffeinated beverages (NSF, 2016). Additionally, they are at risk for substance abuse, car crashes, poor academic performance, obesity, and a weakened immune system (Weintraub, 2016). Troxel et al. (2019) found that insufficient sleep in adolescents is a predictor of risky sexual behaviors. Reasons given for this include that those adolescents who stay out late, typically without parental supervision, are more likely to engage in a variety of risky behaviors, including risky sex, such as not using birth control or using substances before/during sex. An alternative explanation for risky sexual behavior is that the lack of sleep negatively affects impulsivity and decision-making processes. Figure 6.7 Source Why do adolescents not get adequate sleep? In addition to known environmental and social factors, including work, homework, media, technology, and socializing, the adolescent brain is also a factor. As adolescent go through puberty, their circadian rhythms change and push back their sleep time until later in the evening (Weintraub, 2016). This biological change not only keeps adolescents awake at night, it makes it difficult for them to wake up. When they are awake too early, their brains do not function optimally. Impairments are noted in attention, academic achievement, and behavior while increases in tardiness and absenteeism are also seen. 229 To support adolescents’ later sleeping schedule, the Centers for Disease Control and Prevention recommended that school not begin any earlier than 8:30 a.m. Unfortunately, over 80% of American schools begin their day earlier than 8:30 a.m. with an average start time of 8:03 a.m. (Weintraub, 2016). Psychologists and other professionals have been advocating for later school times, and they have produced research demonstrating better student outcomes for later start times. More middle and high schools have changed their start times to better reflect the sleep research. However, the logistics of changing start times and bus schedules are proving too difficult for some schools leaving many adolescent vulnerable to the negative consequences of sleep deprivation. Troxel et al. (2019) cautions that adolescents should find a middle ground between sleeping too little during the school week and too much during the weekends. Keeping consistent sleep schedules of too little sleep will result in sleep deprivation but oversleeping on weekends can affect the natural biological sleep cycle making it harder to sleep on weekdays. Adolescent Sexual Activity By about age ten or eleven, most children experience increased sexual attraction to others that affects social life, both in school and out (McClintock & Herdt, 1996). By the end of high school, more than half of boys and girls report having experienced sexual intercourse at least once, though it is hard to be certain of the proportion because of the sensitivity and privacy of the information. (Center for Disease Control, 2004; Rosenbaum, 2006). Adolescent Pregnancy: As can be seen in Figure 6.8, in 2018 females aged 15–19 years experienced a birth rate (live births) of 17.4 per 1,000 women. The birth rate for teenagers has declined by 58% since 2007 and 72% since 1991, the most recent peak (Hamilton, Joyce, Martin, & Osterman, 2019). It appears that adolescents seem to be less sexually active than in previous years, and those who are sexually active seem to be using birth control (CDC, 2016). Figure 6.8 Source Risk Factors for Adolescent Pregnancy: Miller et al. (2001) found that parent/child closeness, parental supervision, and parents' values against teen intercourse (or unprotected intercourse) decreased the risk of adolescent pregnancy. In contrast, residing in disorganized/dangerous neighborhoods, living in a lower SES family, living with a single parent, having older sexually 230 active siblings or pregnant/parenting teenage sisters, early puberty, and being a victim of sexual abuse place adolescents at an increased risk of adolescent pregnancy. Consequences of Adolescent Pregnancy: After the child is born life can be difficult for a teenage mother. Only 40% of teenagers who have children before age 18 graduate from high school. Without a high school degree her job prospects are limited, and economic independence is difficult. Teen mothers are more likely to live in poverty, and more than 75% of all unmarried teen mother receive public assistance within 5 years of the birth of their first child. Approximately, 64% of children born to an unmarried teenage high-school dropout live in poverty. Further, a child born to a teenage mother is 50% more likely to repeat a grade in school and is more likely to perform poorly on standardized tests and drop out before finishing high school (March of Dimes, 2012). Research analyzing the age that men father their first child and how far they complete their education have been summarized by the Pew Research Center (2015) and reflect the research for females. Among dads ages 22 to 44, 70% of those with less than a high school diploma say they fathered their first child before the age of 25. In comparison, less than half (45%) of fathers with some college experience became dads by that age. Additionally, becoming a young father occurs much less for those with a bachelor’s degree or higher as just 14% had their first child prior to age 25. Like men, women with more education are likely to be older when they become mothers. Eating Disorders Figure 6.9 According to the DSM-5-TR (American Psychiatric Association, 2022), eating disorders are characterized by a persistent disturbance of eating or eating-related behavior that results in the altered consumption or absorption of food and that significantly impairs physical health or psychosocial functioning. Although eating disorders can occur in children and adults, they frequently appear during the teen years or young adulthood (National Institute of Mental Health (NIMH), 2016). Eating disorders affect both genders, although rates among women are 2½ times greater than among men. Similar to women who have eating disorders, men also have a distorted sense of body image, including muscle dysmorphia, which is an extreme desire to increase one’s muscularity (Bosson et al., 2019). The prevalence of eating disorders in the United States is similar among Non-Hispanic Whites, Hispanics, African-Americans, and Asians, with the exception that anorexia nervosa is more common among Non-Hispanic Whites (Hudson et al., 2007; Wade et al., 2011). Source Risk Factors for Eating Disorders: Because of the high mortality rate, researchers are looking into the etiology of the disorder and associated risk factors. Researchers are finding that eating disorders are caused by a complex interaction of genetic, biological, behavioral, psychological, and social factors (NIMH, 2016). Eating disorders appear to run in families, and researchers are working to identify DNA variations that are linked to the increased risk of developing eating 231 disorders. Researchers from King’s College London (2019) found that the genetic basis of anorexia overlaps with both metabolic and body measurement traits. The genetic factors also influence physical activity, which may explain the high activity level of those with anorexia. Further, the genetic basis of anorexia overlaps with other psychiatric disorders. Researchers have also found differences in patterns of brain activity in women with eating disorders in comparison with healthy women. The main criteria for the most common eating disorders: Anorexia nervosa, bulimia nervosa, and binge-eating disorder are described in the DSM-5-TR (American Psychiatric Association, 2022) and listed in Table 6.1. Table 6.1 DSM-5-TR Eating Disorders Anorexia Nervosa  Restriction of energy intake leading to a significantly low body weight  Intense fear of gaining weight  Disturbance in one’s self-evaluation regarding body weight Bulimia Nervosa Binge-Eating Disorder  Recurrent episodes of binge eating  Recurrent inappropriate compensatory behaviors to prevent weight gain, including purging, laxatives, fasting or excessive exercise  Self-evaluation is unduly affected by body shape and weight  Recurrent episodes of binge eating  Marked distress regarding binge eating  The binge eating is not associated with the recurrent use of inappropriate compensatory behavior Health Consequences of Eating Disorders: For those suffering from anorexia, health consequences include an abnormally slow heart rate and low blood pressure, which increases the risk for heart failure. Additionally, there is a reduction in bone density (osteoporosis), muscle loss and weakness, severe dehydration, fainting, fatigue, and overall weakness. Anorexia nervosa has the highest mortality rate of any psychiatric disorder (Arcelus et al., 2011). Individuals with this disorder may die from complications associated with starvation, while others die of suicide. In women, suicide is much more common in those with anorexia than with most other mental disorders. The binge and purging cycle of bulimia can affect the digestives system and lead to electrolyte and chemical imbalances that can affect the heart and other major organs. Frequent vomiting can cause inflammation and possible rupture of the esophagus, as well as tooth decay and staining from stomach acids. Lastly, binge eating disorder results in similar health risks to obesity, including high blood pressure, high cholesterol levels, heart disease, Type II diabetes, and gall bladder disease (National Eating Disorders Association, 2016). 232 Figure 6.10 Source Eating Disorders Treatment: To treat eating disorders, adequate nutrition and stopping inappropriate behaviors, such as purging, are the foundations of treatment. Treatment plans are tailored to individual needs and include medical care, nutritional counseling, medications (such as antidepressants), and individual, group, and/or family psychotherapy (NIMH, 2016). For example, the Maudsley Approach has parents of adolescents with anorexia nervosa be actively involved in their child’s treatment, such as assuming responsibility for feeding the child. To eliminate binge eating and purging behaviors, cognitive behavioral therapy (CBT) assists sufferers by identifying distorted thinking patterns and changing inaccurate beliefs

[OT 104] Lec. 4: Gray Matter of Spinal Cord

EXTERNAL AND INTERNAL STRUCTURE OF THE BRAIN STEM DR A. A. NWAKANMA THE BRAINSTEM •The brainstem is made up of the medulla oblongata, pons and midbrain •It is stalklike in shape and connects the narrow spinal cord with the expanded forebrain •Occupies the posterior cranial fossa of the skull Loading… FUNCTIONS OF BRAINSTEM •It serves as a conduit for the ascending and descending tracts connecting the spinal cord to the different parts of the higher centers in the forebrain •It contains important reflex centers associated with the control of respiration and CVS. •It is also associated with the control of consciousness •It contains important nuclei of cranial nerves II through XII EXTERNAL FEATURES OF MEDULLA OBLONGATA • The medulla oblongata connects the pons superiorly with the SC inferiorly •The junction of the medulla and SC is at the origin of the anterior and posterior roots of the first cervical nerve which corresponds approximately to the level of the foramen magnum Loading… EXTERNAL FEATURES OF MEDULLA •The medulla oblongata is piriform in shape •It has a broad superior part – open part •And a lower closed part •The central canal of the SC continues upward into the lower half of the medulla •In the upper half of the medulla it expands as the cavity of the fourth ventricle EXTERNAL FEATURES OF MEDULLA •On the ant. Surface of the medulla is the anterior median fissure which is continous inferiorly with the ant. Median fissure of the SC •On each side of the median fissure is a swelling called the pyramid EXTERNAL FEATURES OF MEDULLA •The pyramids are composed of bundles of nerve fibers, corticospinal fibers which originate in large nerve cells in the precentral gyrus of the cerebral cortex •The pyramids tapers inferiorly and majority of the descending fibers cross over to the opposite side forming the decussation of the pyramids here •The ant. External arcuate fibers are a few nerve fibers that emerge from the ant. Median fissure above the decussation and pass laterally over the medulla oblongata to enter the cerebellum EXTERNAL FEATURES OF MEDULLA •Posterolateral to the pyramids are the OLIVES which are oval elevations produced by the underlying inf. Olivary nuclei •In the groove b/w the pyramid and olive emerges the rootlets of the hypoglossal nerve •Post. To the olives are the inf. Cerebellar peduncles which connect the medulla to the cerebellum EXTERNAL FEATURES OF MEDULLA •In the groove b/w the olive and the inf. Cerebellar peduncle emerges the roots of the glossopharyngeal and vagus nerves and the cranial roots of accessory nerve •The post. Surface of the sup. Half of the medulla forms the lower part of the floor of the 4th ventricle External features of medulla •The post surface of the inf. Half continues with the post. Aspect of the SC and possesses a post. Median sulcus •On each side of the median sulcus is an elongated swelling , the Gracile tubercle produced by the underlying gracile nu. •Lat. To the gracile tubercle is the cuneate tubercle produced by the underlying cuneate nu. Loading… INTERNAL STRUCTURE OF MEDULLA •The internal structure of the medulla oblongata is usually considered at 3 levels •Level of pyramidal decussation •Level of olive •Level of sensory or lemniscal decussation T/S OF MEDULLA AT THE LEVEL OF OLIVE •This level corresponds to the floor of the 4th ventricle and the cranial n. Nuclei seen include •Hypoglossal n. • Vestibular nuclei •Dorsal nu. Of vagus •Solitary tract and its nu. •Nu. Ambigus • dorsal and ventral cochlear nu. T/S OF MEDULLA AT THE LEVEL OF OLIVE •The other masses of gray matter seen at this level include •The medial and dorsal accessory olivary nu. •Lat. Reticular nu. •Arcuate nu. •The descending tracts seen include •Pyramid •Rubrospinal tract •Spinal nu. And •Tract of trigeminal n. T/S OF MEDULLA AT THE LEVEL OF OLIVE •The ascending tracts include •Medial lemniscus lying in the middle and is L shaped •Spinothalamic T •Spinocerbellar T. •Spinotectal T. •The reticular formation and the inf. Olivary nu. Are also prominent features found at this level T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •The level represented by this section lies a little above the level of the pyramidal decussation •The structures found at this level include •Central canal surrounded by gray matter •Medial lemniscus •The pyramids the nu. And fasciculus cuneatus •Spinal nu. Of trigeminal n. •The reticular formation T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •Internal arcuate fibers which arise from the nu. Gracilis and cuneatus and arch forward on the medial side of the gray matter crossing in the midline to form the lemniscal or sensory decussation •Accessory cuneate nu. Lying dorsolateral to the cuneate nu. T/S OF THE MEDULLA AT THE LEVEL OF LEMNISCAL DECUSSATION •The cranial nerve nuclei seen at this level include •Hypoglossal nu. •Dorsal motor nu. Of vagus •Arcuate nu. •Nu. Of solitary tract •Nu. Ambigus •Other structures include •Lower part of inf. Olivary nu. •Lat. Reticular nu. •Arcuate nu. •Lat. & ventral spinothalamic tr. •Doral and ventral spinocerebella tr. •Spino-olivary tr. •Pyramids •Vestibulospinal tr. •Corticospinal tr. •Medial longitudinal fasciculus Connections of the Inferior Olivary Complex • The main afferents of the inferior olivary nucleus are from the cerebral cortex and from the spinal cord • The main efferents are to the cerebellar cortex. • An olivospinal tract is traditionally described, but some authorities hold that the inferior olivary nuclei do not send any fibres to the spinal cord. •The nucleus may be regarded as a relay station on the cortico-olivo-cerebellar and spino-olivo-cerebellar pathways. • The accessory olivary nuclei are connected to the cerebellum by parolivo-cerebellar fibres. THE PONS •The pons is the middle part of the brainstem •Its continuous below with the medulla oblongata and above with the midbrain •It is seperated from the cerbellum by the 4th ventricle •Pons has two surfaces: •Ventral and dorsal External Features Of Ventral Surface Of Pons •The ventral surface of pons shows the following features •The ventral surface is convex and has a shallow groove in the midline called the basilar groove which lodges basillar artery •Transvesely running fibers connecting the pons to the cerebellum thru the middle cerebellar peduncle •The two roots of trigeminal nerve (sensory and motor) emerge at the jxn b/w the ventral surface of pons and middle cerebellar peduncle EXTERNAL FEATURES OF DORSAL PONS •The dorsal surface of pons shows the following features •Median sulcus in the median plane •Medial eminence – shows rounded elevation in the lower part called facial colliculus which overlies the nu. Of abducent n. •Sulcus limitans – is lat. To the medial eminence and seperates medial eminence from vestibular area T/S THROUGH CAUDAL PART OF PONS •The features seen at this level include •Medial lemniscus in the most ant. Part of the tegmentum •The facial nu. Lies post to the lat. Part of the medial lemniscus •The fibers of the facial nerve wind around the nu. Of the abducent nerve producing the facial colliculus T/S THROUGH CAUDAL PART OF PONS •The medial longitudinal fasciculus is situated beneath the floor of the 4th ventricle on either side of the midline •The medial longitudinal fasciculus is the main pathway that connects the vestibular and cochlear nuclei with the nuclei controlling the extraocular muscles (oculomotor, trochlear and abducent) •The medial vestibular nu. Is situated lat. To the abducent nu. And in close relationship to the inf. Cerebellar peduncle T/S THROUGH CAUDAL PART OF PONS •The sup. Part of the lat. And inf. Part of sup. Vestibular nu. Are found at this level •Post. And ant. Cochlear nu. Are also found at this level •The spinal nu.of trigeminal nerve and tract lie on the anteromedial aspect of the inf. Cerebellar peduncle T/S THROUGH CAUDAL PART OF PONS •The trapezoid body is made up of fibers derived from the cochlear nuclei and the nuclei of trapezoid body •They run transversely in the ant. Part of the tegmentum •The basilar part of the pons at this level contain masses of nervr cells called pontine nuclei T/S THROUGH CAUDAL PART OF PONS •The axons of these cells give origin to the transverse fibers of the pons which cross the midline and intersect the corticospinal and corticonuclear tracts breaking them up into small bundles Loading… INTERNAL STRUCTURE OF CRANIAL PART OF PONS •The internal structure of the cranial part of pons is similar to that seen at the caudal level but contains the motor and principal sensory nuclei of the trigeminal nerve •The motor nu. Of the trigeminal nerve is situated beneath the lat. Part of the 4th ventricle within the reticular formation INTERNAL STRUCTURE OF CRANIAL PART OF PONS •The principal sensory nu. Of the trigeminal nerve is situated lateral to the motor nu. •The sup. Cerebellar peduncle is situated posterolat. To the motor nu. Of trigeminal nerve EXTERNAL FEATURES OF MIDBRAIN •Midbrain measures about 2cm in length and connects the pons and cerebellum with the forebrain •The midbrain is traversed by a narrow channel – the cerebral aqueduct ( which is filled with CSF) •On the posterior surface are four rounded eminences that are divided into superior and inferior pairs •The sup. Colliculi are centers for visual reflexes while the inf. Are lower auditory centers •In the midline below the inf. Colliculi emerges the trochlear nerves EXTERNAL FEATURES OF MIDBRAIN •Each colliculi is related to a ridge called brachium •The sup. Brachium passes from the sup. Colliculus to the lat. Geniculate body and the optic tract •The inf. brachium connects the inf colliculus to the medial geniculate body EXTERNAL FEATURES OF MIDBRAIN •On the anterior aspect of the midbrain is a deep depression in the midline called the interpeduncular fossa which is bounded on either side by the crus cerebri •Many blood vessels perforate the floor of the interpeduncular fossa and this region is termed the post. Perforated substance INTERNAL STRUCTURE OF MIDBRAIN •The midbrain is divided into two parts – •An upper tectum and •A lower part called cerebral peduncles •The upper part (tectum) contains mainly the colliculi of the two sides and represents the dorsal part of the midbrain •The cerebral peduncles are subdivided by the substantia nigra into •The tegmentum and •Crus cerebri STRUCTURE OF MIDBRAIN AT OF INF. COLLICULUS •The structures seen at this level include •Crus cerebri- this contain descending fibers from different parts of the cerebral cortex •The medial 1/6 contain frontopontine fibers •The intemediate 2/3 contain corticospinal and corticonuclear fibers •The lat. 1/6 contain temporopontine fibers •Other structures include •Substantia nigra •Cerebral aqueduct : this is surrounded by the central gray matter. •Ventral to this aqueduct is the oculomotor and trochlear nerves STRUCTURE OF MIDBRAIN AT OF INF. COLLICULUS •Reticular formation b/w the substantia nigra and gray matter •Inferior colliculus •Mesocephalic nu. Of trigeminal nerve •Compact bundle of fibers lies in the tegmentum dorsomedial to the substantia nigra •This bundle consistsof the medial lemniscus, trigeminal lemniscus and spinal lemniscus •Medial longitudinal fasciculus •Superior cerebellar peduncle •Rubrospinal tract Structure of midbrain at the level of sup. colliculus •The following structures are seen at this level •Sup. Colliculus in the tectum •Red nu. In the tegmentum dorsomedial to the substantia nigra •Oculomotor nuclei near the central gray matter •Bundles of ascending fibers consisting of medial lemniscus, spinal lemniscus and trigeminal lemniscus Structure of midbrain at the level of sup. colliculus •Dorsal tegmental decussation : this consists of fibers originating in the sup. Colliculus, it crosses to the opp. Side and descend as the tectospinal tract •Ventral tegmental decussation : this originates in the red nu

White Matter/Gray Matter/Multiple sclerosis

SPINE AND GRAY MATTER

Slides - Gray Matter, Spinal Cord, Eye, Nerve

Front Back Acousto- Hearing Af- Toward Alges/o Sense of pain Audi/o Hearing, sound Aur/o Ear Blephar/o Eyelid Cac/o Bad or ill Cerebell/o Cerebellum; small hind brain Cerebr/o Brain, cerebrum; large outer brain Chrom/o Color Conjunctiv/o Conjunctiva; lining of the surface of the eye Corne/o Cornea Cor/o Pupil Core/o Pupil Dacry/o Tears, tear duct Dendr/o Tree Disk Flat, round structure; intervertebral disk Dur/o Tough Echo- Reflected sound Ef- Away from Encephal/o Brain Esthesi/o Feeling, sensation Fovea Pit or depression -ferent Carry Furc/o Branch; forked Gangli/o Ganglion; mass of nerve tissue -glia Gluey substance Gloss/o Tongue Hydr/o Water -ia State of, condition,, process -ictal Seizure, attack Irid/o Iris Kerat/o Horn, hard tissue Cornea transparent part of the coat of the eyeball that covers the iris and pupil and admits light to the interior Labyrinth Labyrinth; maze Lacrim/o Tears -lepsy Seizure Lingu/o Tongue Mal- Bad, abnormal -mania Madness Meat/o Passage, opening meatus Megal/o Large Mening/o Meninges; lining of the central nervous system -mentia Mental, mind Myel/o Bone marrow or spinal cord Myring/o Eardrum, tympanic membrane Narc/o Numbness, stupor Neur/o Neuron, nerve Noct/i/o/u Night Ocul/o Eye Olfact- Smell -opia Vision (condition of) Opt/o Vision Ophthalm/o Eye Ot/o Ear Pachy- Thick Phasia Speak or speech Phas/o Speech -phobia Fear -phonia Sound or voice Phon/o Sound Phot/o Light -phrenia Disorder of the mind Poli/o Gray matter disease Presby/o- Old age Psych/o Mind, soul -ptosis Prolapse, drooping Pupill/o Pupil of the eye Radicul/o Nerve root, spine Reticul/o Network of cells Retin/o Retina; inner lining of the eye Rhiz/o Nerve root -schisis Split, fissure Schiz/o Split Scler/o Sclera; white of the eye or hardening Sens- Feeling Son/o Sound -spasm Sudden, involuntary muscular contraction Staped/o- Stapes; bone of the middle ear Ton/o Tension, pressure Tympan/o Eardrum Vitre/o Glass-like Achromatism (condition of) Absence of color; colorless; unable to see color Acoustic Pertaining to hearing Afferent To carry toward Anesthesia Without feeling or sensation Aphasia Without speech Audiogram Record of hearing Audiometer Instrument to measure hearing Audiometry Measurement of hearing Auditory Pertaining to hearing Auricle Outer ear Binocular Pertaining to two eyes Blepharitis Inflammation of the eyelid(s) Blepharoplasty Surgical repair of the eyelid(s) Blepharoptosis Drooping of the eyelids Blepharospasm Involuntary contraction of the eyelid Cacophony Bad sound Cerebrospinal Pertaining to the brain and spinal cord Conjunctivitis Inflammation of the conjunctiva Dacryocystorhinostomy Surgical creation of an opening between lacrimal sac and nose Dendrites Branch of a neuron Dementia Memory impairment Diplopia Double vision Dysphasia Difficulty speaking Efferent To carry away from Encephalitis Inflammation of the brain Encephalotomy To dissect the brain Epilepsy Recurring seizures Exophthalmic Eyes slightly out Fovea Pit Hydrocephalus Condition of water in the brain Hyperopia Far vision (referring to farsighted) Insomnia Not being able to sleep Intraocular Within the eye Iridectomy Removal of the iris Keratometry Measurement of the cornea Keratoplasty Repair of the cornea (corneal transplant) Keratotomy Incisions into the cornea (corrects mild to moderate myopia) Lacrimal Related to the tear ducts Malaise A feeling of general discomfort or uneasiness Megalomania Madness about great or large(having an over- inflated ego) Meninges Meninges or coverings of the brain Meningitis Inflammation of the brain coverings (meninges) Meningocele Herniation or protrusion of the meninges Microglia small glue; specialized neuroglial cells Monochromatic One color or hue Motor Referring to movement Myelography The process of recording a picture of the spinal cord Myopia Nearsightedness Narcolepsy Sleep seizures Neuralgia Nerve pain Neuroglia(l) Nerve glue (supporting nerve cells) Neurology The study of nerves Neuron Pertaining to the nerve Oculomotor Movement of the eye Olfactory Referring to smell Oligodendrocyte Specialized neuroglial cells Ophthalmologist One who studies the eyes Ophthalmoplegia Paralysis of the eye(s) Ophthalmoscope Instrument to view the interior of the eye(s) Optic Having to do with the eye Optometry Measurement of the eyes Ossicle Small bones ( especially tiny middle ear bones) Otitis media Middle ear infection Otolaryngologist one who specializes with the ear, nose and throat Otoscope Instrument to view inside the ear Photophobia Fear of light (what it really means is to be light sensitive) Polyneuritis Inflammation of many nerves Presbyopia Aging vision Radiculopathy Nerve root disease Reticular Net-like Reticulocyte Net cell Retinopathy Disease of the retina Schizophrenia Condition of split mind Sense Feeling Somnambulism State of sleep walking or other motor acts during sleep Spinal Spine or spinal cord Stapedectomy Removal of the stapes (to correct conductive deafness) Tonometer Instrument to measure pressure (used for glaucoma) Trigeminal Relating to cranial nerve Tympanitis Inflammation of the ear drum Vitrectomy Removal of the vitreous Vitreous Glass-like fluid of the eye Myringotomy Incision into the ear drum Poliomyelitis Inflammation of the gray matter of the spinal cord (disease)

Central - brain and spinal cord Peripheral - everything else soma - body dendrites - the fingers that extend from the soma or cell body afferent - from the body to the central nervous system (sensory information) Sensory info - coming into the CNS (from the body) Afferent neuron Interneuron - in between CNS and PNS Motor info - coming out of the CNS (to the body) Efferent neuron Neurons: nerve cells Receive information in dendrites Information flows through the axon Eventually reaches an effector Synapse: gap between two neurons Synaptic terminals Glial cells Support the neurons Schwann cells & Oligodendrocytes Myelin sheath On the axon Function: prevents cross-talk and accelerates the speed of action potential Schwann cell - produces myelin sheath in PNS Oligodendrocytes - produces myelin sheath in CNS Like an octopus: many arms wrapping around different / same neurons unlike Schwann cell Node of Ranvier - space in between schwann cells Saltatory conduction Presence of node of Ranvier allows jumping of signals → much faster nerve impulse jumps from node to node Grey matter - cell body, dendrites, synapses White matter - myelinated axons (white color comes from lipid) Dorsal root ganglion Large collection of afferent neurons near the spinal cord Cell body Location is different in Sensory vs. peripheral neurons Sensory neurons - cell body in dorsal root ganglion Peripheral neurons - cell body in gray matter (make sure to know how to identify which microscope took what kind of pictures) SEM vs. TEM SEM - outer surface TEM - inner matter, more detail? Interneurons Help with more complicated types of signals such as reflex Non-decremental action potential: does not die out over space Energy at first same as energy at the end Nerve impulse Resting membrane potential: Inside of axon is -70 mV due to negatively charged proteins inside Inside: potassium outside: sodium Ions cannot diffuse in and out of membrane: requires proteins to allow exchange Depolarization (sodium influx) Threshold hit: open voltage gated sodium channel → facilitated diffusion of sodium ions (NA+) into the cells → inner charge becomes more positive Repolarization (potassium efflux) Voltage gated potassium channels open a little later → facilitated diffusion of potassium ions (K+) to out of the cells → inner charge becomes more negative hillock Refractory period Absolute: absolutely will not get an action potential during this period Relative: membrane potential lower than -70mV → can get an action potential depending on the size of the stimulus because it requires a bigger stimulus to reach the threshold Sodium-potassium pump Active transport (against concentration gradient) resets the sodium and potassium to allow the nerve impulse to happen again pumps 3 sodium out, pumps 2 potassium in Intensity is indicated by the frequency of action potentials Ex. very hot - thousands of action potentials Ex. nice and warm - some action potentials

White & Gray matter

White & Gray matter

white or gray matter