Chapter 22: Homeostasis, Reproduction and Development PDF

Chapter 22: Homeostasis, Reproduction and Development SCB 101 Prof. Calkins Homeostasis Homeostasis: the process that maintains constant internal environment despite changes in the external environment Accomplished in a series of steps to return departure...

Chapter 22: Homeostasis, Reproduction and Development SCB 101 Prof. Calkins Homeostasis Homeostasis: the process that maintains constant internal environment despite changes in the external environment Accomplished in a series of steps to return departures from the genetically determined normal state back to the set point  Maintaining balance in the body What are some ways our bodies need to maintain balance? Water levels Salt concentration Homeosta Blood glucose levels Oxygen concentration sis Heart rate Breathing rate Blood pressure ALL ORGANS WORK TOGETHER TO MAINTAIN HOMEOSTASIS Homeostatic Pathways Homeostatic pathways: the steps used to return to the set point Large fluctuations in external conditions produce little or no change in the overall state. For example: Even when the outside temperature is very hot or cold, the human body’s internal temperature stays within the narrow range required for survival. Set point: the normal state of the organism Homeostatic pathways seek to return to the set point when they deviate from them  Sensors measure the property or unit of a system The controller establishes the set point and tells the system what to do to get back there Effectors change the value of the system Homeostatic Pathways Homeostatic Pathways Negative feedback loops: turn Positive feedback loops: off or reduce the output of a increase the output of the same processIf body temperature deviates from Example: process Example: The process of blood clotting the set point, the body tries to correct it by releases chemicals that lead to even more pushing temperature in the opposite blood clotting. direction Negative Feedback Importance of Homeostasis Most enzymes in the human body work efficiently at 37°C Illness or extreme conditions can overwhelm the body’s natural homeostatic state From Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Homeostasis: Body Temperature Sensor: Temperature sensors in the skin and brain Controller: The brain establishes a set point Effector: Cooling effector: sweat Warming effector: shiver  Recap: Homeostasis is: a. The ability to produce heat and maintain an internal temperature b. The ability to maintain an exact internal body state c. The ability to fluctuate internal body state to match the environment d. The ability to maintain constant internal conditions in the face of varying external conditions  Recap: Why is the body temperature maintained at about 37°C? a. That’s the temperature that most pathogens are killed. b. That’s how much heat our metabolic processes can produce. c. That’s the temperature at which our metabolic processes and enzymes are most efficient. d. That’s the average body temperature of all animals.  Recap: What does “Negative Feedback” mean in homeostasis? a. When the system deviates, a force is applied in the opposite direction b. When Prof. Calkins gets mad. c. When the system deviates and a force is applied in the same direction d. When a system deviates and there is no way to fix it  The Brain’s Role in Homeostasis Hypothalamus: located at base of the brain, is in charge of homeostasis for most systems Connected to pituitary gland, which secretes regulatory hormones Nerve cells inside the hypothalamus send signals to the pituitary gland, which will send hormonal signals  Human Reproduction Human reproduction is sexual reproduction: – Requires the joining of a haploid male gamete and a female gamete – Male gamete: sperm – Female gamete: egg – Forms a diploid zygote Diploid: having both of all pairs of chromosomes 46 human chromosomes Haploid: having only one of each pair of chromosomes 23, rather than 46, human chromosomes Asexual reproduction: cells from only one individual produce the offspring – All the offspring’s genes come from only one parent. Variety of Reproductive Systems in Animals Spermatogen esis Spermatogenesis: the production of mature sperm capable of fertilizing an egg – Meiosis produces sperm and occurs in the seminiferous tubules of the testes. – A healthy young male produces 300 million sperm each day. – Unused sperm degrade and are reabsorbed. How Do Men Produce Sperm? After meiosis is complete, the sperm mature in the epididymis, a coiled structure that sits atop each testis. Sperm is stored in the epididymis until arousal where it will move into the vas deferens then up past various glands to create semen. Hormones and Sperm Production  Recap: Where do the hormones FSH and LH come from and what do they do in men? a. The pituitary gland; FSH causes cells in the testes to produce sperm, and LH causes cells in the testes to secrete testosterone b. The hypothalamus; FSH causes cells in the testes to secrete testosterone , and LH causes cells in the testes to produce sperm c. The prostate gland; both FSH and LH causes cells in the testes to estrogen d. The ovary; FSH causes cells in the testes to produce sperm, and LH causes cells in the testes to secrete testosterone  Recap: Why does it make sense that the testes are actually housed outside the body core? a. Because male mammals get selected by females based on the size of their testes b. Because they need more oxygen than would be found inside the body for the sperm to function properly c. Because they need to be kept at a warmer temperature than normal body temperature in order for the sperm to function properly d. Because they need to be kept at a cooler temperature than normal body temperature for the sperm to function properly  Recap: Sperm cells are formed initially in the testes. What path do they follow to get to ejaculation? a. Epididymis, vas deferens, urethra b. Prostate gland, epididymis, vas deferens, urethra c. Epididymis, vas deferens, vulva, urethra d. Vas deferens, prostate gland, urethra  How Do Women Produce Eggs? Ovarian cycle: Develops eggs – Once puberty starts, one oocyte develops into a mature egg each month – After egg matures, it bursts from the ovary, which is called ovulation. Uterine Cycle: Prepares uterus for possible pregnancy – Thickening of the uterine lining The Ovarian Cycle: Oogenesis Oogenesis: the production of mature eggs capable of being fertilized – Begins before birth in humans – Germ line cells develop via meiosis into immature diploid egg cells called primary oocytes. – At birth, the female has about 1–2 million primary oocytes. – At puberty, generally only one oocyte per month matures into a haploid egg. About 10–13 years of age – Only about 400,000 primary oocytes remain by then. Hormones and the Ovarian Cycle  Recap: Where do the hormones FSH and LH come from and what do they do in women? a. The pituitary gland; FSH causes a follicle in the ovary to mature and release an egg, and LH stimulates estrogen secretion. b. The hypothalamus; FSH stimulates estrogen secretion, and LH, causes a follicle in the ovary to mature and release an egg c. The prostate gland; FSH causes a follicle in the ovary to mature and release an egg, and with LH, stimulates testosterone secretion. d. The ovary; FSH causes a follicle in the ovary to mature and release an egg, and LH stimulates estrogen secretion.  Recap: During ________ an egg ruptures from the ovary. a. Secretion b. Ovulation c. Menstruation d. Menopause From Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press The Uterine Cycle Prepares the uterus for possible pregnancy Endometrium, or uterine lining, thickens to house a fertilized egg This process is guided through positive feedback loops and hormonal cues  Recap: FSH and LH cause the ovaries to produce the hormone ___________, which does what to the uterus? a. Estrogen, causes menstruation b. Estrogen, thickens endometrium c. ProEstrogen, causes menstruation d. ProEstrogen, thickens endometrium  Recap: Which part of the brain monitors and regulates levels of testosterone and estrogen? a. The pituitary gland b. The hypothalamus c. The cerebral cortex d. It’s not known how these hormone levels are monitored  Recap: Menstruation is part of the uterine cycle. Why does it happen? a. Scientists have not entirely explained why women menstruate. b. When an egg is released, there is also a release of endometrial fluid from the ruptured follicle. This must be shed in order to prepare the uterus for possible pregnancy. c. Estrogen levels increase at ovulation, causing the development of the ovarian lining in preparation for pregnancy. If there is no pregnancy, the lining is shed. d. When an egg is released, the endometrium or uterine lining develops to support an embryo in case of pregnancy. If pregnancy does not occur, the lining is shed. Fertilization Fertilization takes place in the oviduct, resulting in a zygote that develops in the uterus  Hormones and Pregnancy After ovulation, the egg only has a short time to encounter sperm. After fertilization, a signal is needed that will prevent menstruation. Human chorionic gonadotropin (hCG) is released, which allows the corpus luteum to survive (and keep secreting hormones that prevent menstruation).  Embryonic and Fetal Development Human fetal development takes 38 weeks. Embryonic Development (First trimester): – The single-celled zygote develops into an embryo with all the main tissues. Fetal Development (Second/Third trimesters): – Organ systems develop and fetus increases in size. – Organ systems mature.  Embryonic Development Embryonic Development is how the zygote develops into an embryo with all it’s main tissues – Occurs via mitosis – The embryo becomes a fetus when all organ systems are established. Three phases of Embryonic Development Cleavage: stem cells and placenta develop Gastrulation: cells grow into a type of tissue Differentiation: cells differentiate into specific cell types Cleavage When embryo reaches the 16-cell stage The outer ring of cells make the placenta, connecting fetus to mother The inner ring of cells, termed embryonic stem cells, produce all the cell types of the body Gastrulati on Cells move to new locations and grow into organs.  The zygote can produce any type of cell; adult cells are Differentiati specialized The change in cells from unlimited potential to cells on that are specialized is cell differentiation Cells take on specific structures and functions  Recap After fertilization of an egg, what are the stages of embryonic development? a. Immunization, Fertilization, Gastrulation b. Cleavage, Gastrulation, Differentiation c. Gastrulation, Cleavage, Fertilization d. Cleavage, Differentiation, hybridization Gene Expression Cell differentiation depends upon Cell communication via chemical signals Gene expression (different genes are used in different cells)  Recap All diploid cells in an organism contain the same DNA or genetic material. True or False? a. False. The genetic material is scrambled at every replication, so not every gene is passed along. b. True. But only the genes necessary for a given cell to do its particular “job” are expressed. c. True. All the genes are necessary for every cell to do its “job.” d. False. It would be a waste of energy to copy the chromosomes unnecessary for a cell to do its particular job, so they are not all copied. From Bozzone, Biology for the Informed Citizen, © 2014 by Oxford University Press Fetal Development Second trimester: Organ systems develop and fetus increases in size. Third trimester: Organ systems mature. Respiratory and circulatory systems prepare for a transition from a fluid to a gaseous environment. With the help of today’s technology, a fetus has a reasonable chance of extrauterine survival by the beginning of the third trimester.  Recap What is the main difference between embryonic and fetal development? a. There isn’t any real difference. b. Embryonic development is about growth and in fetal development the major organ systems and structures are organized. c. Fetal development is mainly about growth after the body systems and structures have mostly all been differentiated during embryonic development. d. Embryonic development is all about cell differentiation, and fetal development is more organ and structure differentiation.  Childbirth Hormonal changes in the mother prepare both the mother and the baby for birth. Oxytocin: a hormone secreted by the fetus and the mother’s pituitary gland – Stimulate uterine muscle contraction (labor) – Stimulate placenta to secrete prostaglandins The placenta secretes prostaglandins: – Increases contractions Increased contractions cause more oxytocin to be released. – Positive feedback loop The cervix opens and birth begins.  Contractions The cervix stretches causing a uterine contraction The hormone oxytocin is released, stimulating more contractions As the head of the fetus pushes downward, the cervix stretches 3 Stages of Labor and Delivery  Recap Why are contractions in labor necessary for successful delivery of the baby? a. They push the fetus downward which dilates the cervix such that the baby can fit out. b. They alert the mother that the baby is ready to be born. c. They turn the fetus around so it can be born headfirst. e. They trigger the production of breast milk.