MCB 135e Midterm 2 Review November 3, 2006

1. MCB 135eMidterm 2 ReviewNovember 3, 2006

2. Midterm 2 • Wednesday, November 8 12:10 – 1:00 p.m. • Covers material from Labor and Delivery on 10/6/06 to Growth and Endocrinology (II) on 11/3/06 • Development of the Nervous System (Part 3) will be covered on final

3. Format of Exam • Same as Midterm 1 • Multiple Choice (30 points) • True/False (20 points) • Short Answer (50 points)

4. Sections covered on exam • Labor and Delivery • Cardiorespiratory Changes after Birth • Infant at Risk • Thermoregulation • Lactation • Gastrointestinal Function • Liver • Development of Kidney Function/Kidney and Acid-Base Balance • Growth and Growth Patterns • Growth & Endocrinology (I and II)

5. Labor and Delivery • Parturition • birth of the baby • a biological and social event • Delivery 38 weeks after fertilization or 40 weeks after last menstrual period • Mechanism of onset of labor not completely understood • Mechanical and hormonal factors are important

6. Hormones Involved in Labor • Fetal Hormones • Corticotropin Releasing Hormone (CRH) • Adrenocorticotropic Hormone (ACTH) • Placental Hormones • Estrogen (E) • Progesterone (P) • Prostaglandins • Maternal Hormones • Oxytocin • Relaxin (produced by ovary and also placenta)

7. Fetal Hormones • Corticotropin Releasing Hormone (CRH) • Secreted by hypothalamus • Adrenocorticotropic Hormone (ACTH) • Secreted by anterior pituitary • Cortisol • Secreted by adrenal cortex • Stimulates Estrogen secretion from placenta • Inhibits Progesterone secretion

8. Placental and Maternal Hormones • Increased E secretion and decreased P secretion, leads to: • High E:P ratio • Uterine contractions, because: • E stimulates contractions • P inhibits contractions • Contractions stimulate the maternal hypothalamus to secrete Oxytocin • Oxytocin further stimulates contractions

9. Prostagladins and Relaxin • Prostagladins • Released from the placenta • Stimulated by E and oxytocin • Stimulates oxytocin and promotes contractions • Relaxin • Produced by corpus luteum of the ovary • Loosens ligaments and softens cervix • Increases number of oxytocin receptors

11. Cardiorespiratory Changes after Birth • Transition from prenatal to postnatal life • Must be rapid • Requires critical changes in pulmonary and circulatory systems • Expansion of lungs for first breath • Closure of ductus venosus, ductus arteriosus, and foramen ovale • Removal of fluid from lungs

12. Closure of Foramen Ovale • Results from pressure change in atria • Increased pulmonary blood flow increases pressure in LA • Pressure in left heart greater than right (after birth) • Also, decreased flow from placenta to IVC

13. Closure of Ductus Arteriosus • Results from reduced pulmonary resistance • Pulmonary pressure falls and equals aortic pressure • Lack of pressure gradient reduces blood flow through DA, causing it to shut

14. Fetal Lung Fluid • Composed of amniotic fluid and fluid secreted by the lungs itself • Chloride ion drives fluid into potential airspace of lungs • Generates pressure to stretch the lungs and stimulate growth • Function of the fluid: • Important for growth and specialization of lung components prior to birth • Influences lung resistance

15. Removal of Fetal Lung Fluid • Absorption of Na+ ion at birth switches lung’s capacity to an absorptive state • Membrane of lungs switches from predominantly Cl- secreting to predominantly Na+ absorbing • Reverses flow of fluid in the lungs • Fluid exits the interstitial space via the lymphatic ducts and microcirculation

16. Infant at Risk • Fetal Distress • Low oxygen • Meconium aspiration • Fetal bowl content discharged at birth that could be inhaled and block airways • Sepsis • Blood poisoning • Congenital anomalies • Maternal Diseases • Toxins • Premature birth

17. Thermoregulation • Process of regulating body temperature • Environment, vascular and metabolic adaptations, shivering and sweating are various ways in which adults regulate body temp. • Newborns and infants have reduced capability of regulating body temp.

18. Thermoregulation in Newborns/Infants • Primarily occurs through Non-shivering Thermogenesis • Exposure to cold stimulates hypothalamus • Norepinephrine (NE) is released and stimulates receptors on brown fat cells • Triglycerides are broken down into fatty acids and glycerol through the action of lipase • Fatty acids broken down (oxidized) in mitochondria of BFC • Uncoupling protein leads to heat production instead of ATP • Also, leads to conversion of T4 to T3 • Increased metabolic rate leads to increased body heat production

19. Mechanisms of Heat Loss • Conduction • Transfer of heat from one solid body to another • Convection • Transfer of heat from a solid to the surrounding gas or liquid • Evaporation • Air passing over body evaporates water on surface and removes heat • Largest source of heat loss in infants • Radiation • Exchange of infrared (IR) photons with surroundings • Heat is gained/lost depending on temp. gradient

20. Lactation • Survival and growth of an infant depends on: • Mother’s ability to breastfeed • Baby’s ability to suck • Proper development/function of GI system • Proper development/function of CNS

21. Witches’ Milk and Colostrum • Witches’ Milk • Baby secretes milk few days after birth under the influence of maternal estrogen • Occurs in full-term infants, not pre-mature • Estrogen levels may not be high enough for pre-mature infants • Colostrum • First milk that precedes the production of true milk • Yellowish in color • Rich in antibodies and minerals • High in carbohydrates, proteins, but no fat

22. Milk Production • Stimulated by the hormone Prolactin (PRL) • Secreted by anterior pituitary gland • Levels of PRL increase 20 fold during pregnancy • However, its action is inhibited by high E and P levels • Therefore, milk production is suppressed until birth (except for small amount of colostrum)

23. Milk Production (after birth) • Once the levels of E and P decrease, milk is produced. • With each feeding, secretion of PRL is stimulated.

24. Milk Ejection • Stimulated by the hormone Oxytocin • Suckling stimulates hypothalamus to release oxytocin from posterior pituitary • Oxytocin increases contraction of myoepithelial cells around the ducts • Forces milk out of alveoli and into the large ducts (sinuses) and then out the nipple

25. Benefits of Breastfeeding • Infant • Reduction in infections • Initial increased growth • Decreased obesity in adulthood • Positive effects on mental development • Mother • Rapid weight loss • Decreased risk of breast cancer • Psychological benefits

26. Breastfeeding Not Always Ideal • Maternal illness • Stress • Inadequate milk production • If drugs and toxins are taken by mother • Increased risk of HIV transmission

27. Gastrointestinal Function • Major functions • Digestion and absorption • Defense • Biochemical and immunologic mechanisms • Endocrine • Hormones that regulate GI secretion and motility • Mechanical and chemical mechanisms • Break-down of food, propulsion of food along GI tract, excretion of feces, enzymatic reactions, transport reactions

28. Increased Risk of Dehydration • Smaller size of organs of GI system in early postnatal development • Food contents are liquid, so rapid transit • Shorter duration of food in stomach and throughout GI system • Reduced rate of digestion/absorption • Reduced water reabsorption of intestinal mucosa • Proteins used for growth and development • Very little urea is excreted • A byproduct of proteins • Produced in liver • Helps reabsorb water in the kidneys

29. Liver • Complex functions of digestion and body growth • Formation of bile • CHO storage and release • Formation of urea • Metabolism of cholesterol • Manufacture of plasma proteins • Regulation of fat metabolism • Metabolism of some hormones • Reduction and conjugation of steroid hormones • Vitamin D metabolism • Detoxification of drugs/toxins

30. Jaundice • Caused by high levels of bilirubin in blood • Begins with breakdown of RBCs • Heme from Hb is broken down to bilirubin • Bilirubin enters liver • Conjugation of bilirubin to form a water soluble product and secretion into bile • Conjugated bilirubin excreted in feces • Jaundice occurs when bilirubin is not excreted and instead accumulates in the blood

31. Kidney • Major functions: • Regulation of water and electrolytes • Maintenance of pH • Excretion of waste and byproducts of metabolism • Secretion of hormones • Erythropoietin • Renin • Vitamin D3

32. Functions of Hormones • Erythropoietin • Increases the number of RBCs so there is better oxygen transport (Hematopoiesis – increased formation of RBCs) • Renin • Involved in the secretion of angiotensin • Secreted by juxtaglomerular apparatus of kidneys in response to low blood volume or low body NaCl • Vitamin D3 • Important for calcium metabolism, by increasing calcium absorption in the intestine

33. Hormones that Regulate Kidney Function • Aldosterone Decreased blood pressure/Low blood flow to kidneys Release of Renin from JGA of kidneys AngiotensinogenAngiotensin I Angiotensin IIStimulation of Adrenal CortexAldosterone Secretion ACE = Angiotensin Converting Enzyme Function: Aldosterone leads to increased salt and water retention by kidneys ACE

34. Hormones that Regulate Kidney Function • Antidiuretic Hormone (ADH or vasopressin) • Secreted by hypothalamus • Stored and released from posterior pituitary • Acts on loop of Henle, distal tubules, collecting ducts • Function: • Stimulates cAMP and increases number of water channels • Increases water reabsorption

35. Risk of Dehydration in Infants • Skin – Greater water loss through skin (increased surface area) • GI Tract – Less mature, faster transit so less time for water reabsorption • Kidney – malformations at 5 developmental stages, less urea, shorter loop of Henle (less water through medulla) • Posterior Pituitary – Less ADH Secreted, less sensitivity of cells that line collecting duct • Adrenal Cortex – less aldosterone

36. Changes in Urinary pH in Premature Infants • First week of life • pH tends to be more alkali (pH 6-7) • Second week of life • pH much more acidic (pH 5) • Maintenance of pH difficult in newborns (esp. premature infants) • Kidneys not fully developed • Systems are less efficient

37. Growth • Increase in an organism’s size and weight • Reflection of how well you are (all other systems of body must be functioning properly for growth to occur) • Occurs when anabolic processes predominate over catabolic processes Anabolic: simple substances converted to complex compounds Catabolic: complex substances converted to simple compounds

38. Factors that Affect Growth • Prenatal Period • Genetic factors • Environmental factors • Availability of nutritional substances • Parental age • Parity (amount of time between successive childbirths) • Multiple births • Fetal sex

39. Changes in proportion of human body during growth

40. Comparison of Kwashiorkor and Marasmus Kwashiorkor: West African, means “disease that occurs when displaced from the breast by another child.” Major pathology: protein deficiency Marasmus: Progressive emaciation due to diet deficient in all calories & nutrients

41. Catch-up growth Malnutrition and severe disease cause • Growth retardation However Establishment of adequate nutrition and recovery from illness • Induces growth rate acceleration until individual growth patterns and normalcy in terms of chronologic age are restored.

42. Compensatory Growth • Growth that usually follows the loss of an organ or part of an organ or tissue • Examples: • Cellular hypertrophy (increase in SIZE of cell) as in growth of muscle • Increase in contralateral kidney size when one kidney is removed • Increase in size (hypertrophy and hyperplasia) in response to increased functional demand (e.g., adrenal enlargement during stress) • Hyperplasia: increase in NUMBER of cells

43. Reminder • No discussion section on Monday, Nov. 6 • My office hours on Monday: • 9:10 – 10:00 a.m. Free Speech Café • 1:10 – 2:00 p.m. 105 GPB • Bring pen and pencil to exam