Biology 225 Exam 3 Spring 2020: Endocrinology and Reproduction

glycogenolysis, lipolysis, and gluconeogenesis

All promoted by glucagon glycogenolysis: glucagon stimulates the liver to take up amino acids from the blood and convert them into glucose. breakdown of glycogen by hepatic processes gluconeogenesis: the formation of glucose from lactate and amino acids during the fasting state. Lipolysis the breakdown of stored triglycerides, into free fatty acids and glycerol. ketogenesis:

enteroendocrine cell (EEC) structure

Enteroendocrine cells are packed with secretory granules, the products of which are secreted from the cell in response to chemical and mechanical stimuli to the wall of the GI tract. The most common EECs have: 1. an apical membrane that is in contact with the lumen of the GI tract, (generally where sensing occurs) 2. a basolateral membrane through which secretion occurs. There are also another type of enteroendocrine cells that do not have part or their membrane in contact with the luminal surfaces of the gut: an example is the enterochromaffin-like cell (ECL) in the gastric epithelium, which secretes histamine.

The female estrous cycle

Estrous cycles are named for the cyclic appearance of behavioral sexual activity closely linked to ovulatory cycle. That occurs in all mammals except for higher primates. -The estrous cycle is the main reproductive cycle of other species females of non-primate vertebrates, for example, rats, mice, horses, or pig. Variety of different forms: -Polyestrous animals where the estrous cycles happens throughout the year, like in pigs, mice, or rats. -Seasonal polyestrous animals, those animals that have multiple estrous cycles only during certain periods of the year, for instance, in horses. -Monestrous cycles only have one estrous cycle per year, like the dogs. -Humans and other primates are polyestrous mammals that undergo undergo estrous cycles through the year, although the estrous cycle is more commonly known as the menstrual cycle. Menstrual cycles, which occur only in primates, are named for the regular appearance of menses due to the shedding of the endometrial lining of the uterus.

endocrine vs exocrine glands

Exocrine glands: release chemical substances through ducts to the outside the body or on to another surface within the body. Exocrine pancreas: the pancreas contains exocrine glands that produce enzymes important to digestion, these enzymes include trypsin to digest protein, amylase for the digestion of carbohydrates or lipase to break down the fats. So we can see here the pancreas with the ducts that release the hormones into the intestine. Endocrine glands: release chemicals substance's directly into the bloodstream, or tissues of the body. The chemical substances released by the endocrine glands are known as hormones. The pancreas is also endocrine gland, and secretes hormones like insulin or glucagon that functions to regulate blood sugar levels.

temperature-dependent sex determination

very common in reptiles, in all crocodiles, marine turtles, and some species of lizards The levels of steroid hormones in yolk changes through the breeding season, and influence the pattern of sex determination during development. At an intermediate ambient temperature, develops an equal number between females and males. At the extremes of the breeding season, the same temperature can yield 75% males or 75% percent females.

Water soluble v lipid soluble hormones

water soluble hormone: lipophobic hormone that binds to a receptor on or within the plasma membrane to initiate an intracellular signaling cascade. Lipid soluble hormone: lipophilic hormones that passes through the plasma membrane of a cell, binds to an intracellular receptor and changes gene expression

sex determination among honeybees

- honeybees sex is normally determined by fertilization or non fertilization of eggs rather than the presence or absence of sex chromosomes. -20% of animal species use haplodiploid mode of reproduction (like honeybees) where sex is normally determined by the fertilization or non-fertilization of eggs Bee sex determination Mechanism: - The male develops from unfertilized eggs and females from fertilized eggs. The males are haploid (1 set of chromosomes) and the females are diploids. When the queen bee mates with a drone (male bee), all the diploid individuals (2n) will became females, with DNA combined from the queen and the drone. By contrast, drones are born by parthenogenesis, in which an egg from the queen will develop into a haploid drone (n)

Altricial species v Precocial species

-Altricial species:Are born with little to no hair, feathers, with eyes and ears closed and must receive maternal care. Advantage: with reach diet provide by parents the initial small brains develop into large adult brains Ex) ducks, horses, or deers, humans -Precocial species: Are born with all their hair, feather, or scales and are able to see, hear and move around their habitat. Advantage of reducing the time spent in incubating or growing after birth. Ex) many birds -larger mammals have longer gestation times and that precocious mamma's have longer gestation times than altricial mammal's with similar size.

Adrenocorticotropic hormone (ACTH)

-Corticotropin-releasing hormone (CRH) is released from the hypothalamus -CRH stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH) -ACTH then acts on its target organ, the adrenal cortex -Adrenal cortex produces cortisol and aldosterone -Stress stimulates the release of ACTH. (negative feedback loop) -Diseases associated with ACTH include Cushing syndrome (caused for prolonged exposure to glucocorticoids)

Ovarian and Uterine cycles

-Cyclic ovarian function is under the control of three interacting components: hypothalamus, anterior pituitary and ovary. -With the exception of humans, most mammalian species coordinate ovulation and copulation Mechanism: -The hypothalamus releases the neuropeptide gonadotropin releasing hormone (GnRH) into the hypophysial portal vasculature, which then acts on the anterior pituitary to stimulate the release of the gonadotropins: LH and FSH -GnRHacts via G-proteincoupled receptors on gonadotropes to stimulate synthesis and secretion of LH and FSH -The gonadotropins acting on the ovary provide the hormonal signals that regulate the ovarian cycle and stimulate production of estradiol and progesterone.

METABOLIC COSTS of HUMAN BRAIN DEVELOPMENT

-Most primates grow slower than other mammals, but human childhood stands out as unusually slow. Some hypothesis have viewed slowed growth as compensation for the brain's high energetic needs. -Because of its large size, the human brain has unusually high energy costs which are particularly elevated compared with the body's metabolic cost early in the life cycle. -The human brain's demand for energy is sufficiently high during these periods that it could require that the body expend less on growth. -It has been estimated that the human brain accounts for between 44% and 87% percent of resting metabolic rate during infancy, childhood, and adolescence, suggesting strong trade-offs with other functions. -studies show that the brain glucose uptake peaks in childhood

Thyroid Stimulating Hormone (TSH)

-Regulates the releases of thyroid hormones from the thyroid. -Hypothalamus secrete thyroid releasing hormone which regulates the release of TSH by the pituitary gland. -The thyroid hormones (thyroxine and triiodothyronine) help maintaining normal heart rate, blood pressure and temperature. Thyroid eye disease in hyperthyroidism (Exophthalmos) -The thyroid hormones, thyroxin and ... T3 and T4 help maintain normal heart rate, blood pressure, and temperature. -The thyroid gland is part of hypothalamic-pituitary- thyroid axis -thyroid hormone secretion is controlled by a classical negative feedback

mammary gland

-The mammary gland is composed of both exocrine cells, which secrete milk, and myoepithelial cells, which control the secretions. -In the final weeks of pregnancy, the alveoli swell with colostrum, that is high in protein but contains less fat and glucose than mature breast milk.

Growth Hormone GH (somatotropin)

-The pituitary releases GH in bursts; levels rise following exercise, trauma, and sleep. -GH production rises during childhood, peaks during puberty, and declines from middle age. -In children and adolescents, it stimulates the growth of bone and cartilage. -In people of all ages, GH boosts protein production, promotes the utilization of fat. Hypersecretion: -In children results in gigantism (8- 9 ft is common) -In adults results in acromegaly Hyposecretion: -In children results in dwarfism (max height of 4 ft) -caused by insufficient amounts of growth hormone in the body

pituitary

-consists of two lobes that come from distinct parts of embryonic tissue: the posterior pituitary, or neurohypophysis, is neural tissue, and the anterior pituitary, also known as adrenohypofisis, is glandular tissue -Oxytocin and antidiuretic hormones are transported through axons of magnocellular neurons into the posterior pituitary where they are stored for eventual release into the bloodstream

OVULATION CYCLE in MAMMALS

1-levels of progesterone and estrogen fall below a critical threshold, hypothalamic GnRH is secreted into the blood, stimulating the anterior pituitary to secrete gonadotropins; LH and FSH. 2-FSH causes granulosa cells to proliferate. The mature follicle produces progesterone and estrogen. -The extrafolliclar cells of the ovary produce and release progesterone -The granulosa produces estrogen 3. Many follicles mature in parallel and as the follicle grows, estrogen production increases (Follicular Phase) 4-Elevated estrogen levels in the blood, blocks GnRH release from the hypothalamic-pituitary axis (negative feedback) 5-Estrogens decline and inhibin levels increases 6-FSH declines and only some follicles sustain maturation 7-Just before ovulation the follicle produce more proges- terone 8-Ovulation marks the beginning of Luteal Phase After ovulation: The remnants of the ruptured follicle is called corpus luteum. The corpus luteum release large amounts of progesterone and lesser amount of estrogen to prepare the uterus for implantation If the ovum is not fertilized, progesterone continues to decline and the next ovulatory cycle begins.

Lecture 28 questions

1-What would happen if the trophoblast did not secrete hCG upon implantation of the blastocyst? a) The cells would not continue to divide. b) The corpus luteum would continue to produce progesterone and estrogen. c) Menses would flush the blastocyst out of the uterus. d) The uterine mucosa would not envelop the blastocyst. 2-The layer of the uterine wall that is shed during menstruation is the: a) endometrium. b) myometrium. c) epimetrium. d) None of the above. 3-What hormone is consistently positively correlated with thickening of the endometrium? a)Progesterone b)Estrogen c)LH d)FSH 4-The production of testosterone in the interstitial cells is stimulated by: a) inhibin. b) luteinizing hormone (LH). c) follicle-stimulating hormone (FSH). d) progesterone. 5-Which of the following produce antagonistic results? A)calcitonin and parathryroid hormone B) FSH and LH C)ADH and vasopressin D)oxytocin and prolactin 6-Androgens are produced by the _______. A) ovaries B) testes C) hypothalamus D) islets of Langerhans.

Lecture 25 Questions

1-Which of the following hormones are produced in the anterior pituitary gland? a) Adrenocorticotrophic hormones b)Oxytocin c)FSH d)Vassopressin e)Growth hormone f)LHg)Thyroid stimulating hormone h)Prolactin 2-In males which hormone stimulates Leydig cells to produce testosterone? a)FSH b)Stradiol c)LH d)cholesterol 3-Which of the following are common symptoms of hyperthyroidism? a) Weight gain b) Heat intolerance c) Tremor d)Urinary frequency e) Diarrhea f) Weight loss 4-Which is a more sensitive measure of thyroid function? a) Free T3 b) Free T4 c) TSH d) Both T3 and T4 5-For Hydrophobic hormones, most of circulating hormones is in this form: a) Free hormone dissolved in plasma b) Hormone bound to binding proteins c) Hormone bound to anions d) Hormone bound to lipid membrane 6-The physiological action of the oxytocin include the following: a)Milk ejection from mammary glands b)Milk production from mammary glands c)Contraction of striated muscle d)Contraction of uterine muscle

Lecture 22 questions

1-Which of the following statements is true about calmodulin? a) It is a protein which binds calcium ions and activates protein kinases b) It is a protein which binds calcium ions and binds to DNA to activate transcription c) It is a protein which transports calcium ions across the cell membrane d) It is a protein which modifies calcium ion concentration within the cell 2-Which of the following terms is used to describe a drug that binds to a receptor, fails to activate it and prevents the endogenous chemical messenger from binding? a) agonist b) antagonist c) partial agonist d) inverse agonist 3-Which of the following statements is not true about neurotransmitters? a) Neurotransmitters are released by nerves. b) Neurotransmitters are required to carry a 'message' from a nerve to a target cell. c) Neurotransmitters have significant distances to cover to reach their target cells. d) Neurotransmitters bind to receptors on target cells. 4-Which of the following is not a neurotransmitter? a) acetylcholine b) cyclic AMP c) noradrenaline d) dopamine 5-Which of the following statements is not true regarding the binding site of a receptor? a) The binding site is normally a hollow or cleft in the surface of a receptor. b) The binding site is normally hydrophobic in nature. c) Chemical messengers fit into binding sites and bind to functional groups within the binding site. d) The binding site contains amino acids which are important to the binding process and a catalytic mechanism.

Lecture 20 questions

1-Which of the following statements is true of ligands?Choose 1 answer: a)The binding of a ligand to a receptor molecule causes the receptor to change shape !! b)All ligands are proteins c)Each ligand is only able to bind to one specific receptor d)Ligands can bind to cell-surface receptors, but they cannot enter the cell 2-Which of the following statements regarding cell signaling is true?Choose 1 answer: a) In endocrine signaling, signals are released from a cell and bind to receptors on its own cell membrane b) Paracrine signaling allows neighboring cells to communicate over relatively short distances !! c) Synaptic signaling is a type of autocrine signaling d) Direct signaling occurs between distant cells.: 3-The number of receptors that respond to a hormone determines...Choose one answer: a)The cell's sensitivity to that hormone b)The cell's affinity for that hormone c)The number of different antagonists that can activate the cell d)The different types of hormone-mediated change 4-Which of the following statements are true?Choose all that apply: a) The amplification of the initial hormone-receptor binding ensure minimal response to a hormone b) Messenger molecules bind to effector proteins c) The concentrations of bound hormone, free hormone, and plasma transport protein are in equilibrium. d) Protein binding reduces the circulating half-life of the hormone

Hormone transport

1. Hormone is secreted 2. bound to proteins in the target tissues, so this is the hormone receptor binding 3. The receptor is activated, elicits a signal transduction 4. biological action. Proteins and polypeptide hormones are generally transported free in the blood, but a significant fraction of steroids and thyroid hormones are transported in blood bound to plasma proteins. The concentrations of bound hormone, free hormone, and plasma transport protein, are in equilibrium. >> If free hormone's levels drop, hormone will be released from the transport protein. >> Free hormone is the biologically active form, but protein bindings have the same purposes, for instance, it prolongs the circulating half-life of the hormone, and represent a reservoir of hormones.

how hormonal signals can be terminated?

1. ligand removed by distant tissues Ex) remove the ligand from extracellular fluid. enzymes in the liver degrade many circulating hormones, when hormone level drops, the bound hormone dissociates from its receptors and signaling terminates 2. ligand taken up by adjacent cells (common mechanism for the removal of neurotransmitter from the synapse) 3. ligand degraded by extracellular enzymes 4. ligand-receptor complex removed by endocytosis Ex) internalization of the ligand receptor-complex that is removed as a whole by endocytosis. receptor inactivation 5. inactivation of signal transduction pathway Receptors can also be inactivated by phosphorylation mechanism, and also they components of the signaling pathway can be targets of inactivation, and the signaling terminates. Protein hormones are removed from blood primarily by endocytosis and lysosomal degradation of hormone-receptor complexes. Many protein hormones small enough to appear in urine in a physiological active from, for example, the follicle stimulating hormone, and luteinizing hormone, are present in urine. Hormonal signals can be terminated in several ways: The hormone receptor internalization, or phosphorylation/ dephosphorylation, proteosomal destruction of the receptors, or generation of feedback inhibitors.

lecture 23 questions

1‐Sporadic blood tests to measure growth hormone levels (select all that applies): a) Are meaningless since high and low levels alternate throughout the day b) It is important to make sure cells are growing at normal pace and not aging faster that they should c) It is a recommended blood test for pregnant womend) It is costly but mandatory in adolescents 2‐Which of the following is a physiological function that is mediated by a hormone released by the posterior pituitary? (Choose one answer) a) Maturation of the egg and sperm b) Decrease in calcium levels c) Water retentiond) Increase in thyroid hormone level 3‐Parturition is an example of: a) Feed‐forward action b) Negative feedback loop c) Positive feedback loop d) Both a) and c) 4‐Inhibitory and releasing hormones are produced by the hypothalamus and function to control the __________ a) hypophysis b) Adenohypophysis c) Neurohypophysis 5‐The thyroid‐stimulating hormone (TSH) is produced by the __________ a) Thyroid gland b) Adenohypophysis c) Adrenal gland 6‐The adrenocorticotropic hormone (ACTH) is produced by the __________ a) pineal gland b) Adenohypophysis c) Adrenal gland

Endocrine regulatory feedback systems

4 types: Direct (atrial natriuretic peptide (ANP) in mammalian heart cells) The atrial natriuretic peptide travels to target cells in the blood vessels and the kidneys to lower the blood pressure. The lowered blood pressure feeds back by reducing the tension on the atrial cells and reduces the release of the peptide 1st order 2nd order (endocrine secretion pathway) 3rd order feedback loop

Insulin

A protein hormone synthesized in the pancreas that regulates blood sugar levels by facilitating the uptake of glucose into tissues • Produced by beta Cells - protein hormone. • Acts through Tyrosine Kinase system. • Hypoglycemic - lowers blood glucose. • Increases glucose uptake and utilization by most body cells - Inserts glucose channels on target cells. • Transport/uptake of glucose, amino acids and free fatty acids into cells. • Anabolic hormone - favors protein synthesis, prevents protein degradation. Is also lipogenic, glycogenic. • Inhibits catabolism - Prevents catabolic events such as glycogenolysis, ketogenesis and gluconeogenesis • Primary targets: skeletal muscle and adipose tissue three pathways for insulin secretion after eating causes blood glucose increase Mechanism 1: 1. The presence of food in the intestine triggers the release of gastrointestinal tract hormones, and this is the initial trigger for insulin production and secretion by the beta cells of the pancreas. 2. Once nutrient absorption occurs, the resulting increase of blood glucose levels further stimulates insulin secretion. 3. Activates a tyrosine kinase receptors, triggering the phosphorylation of many substrates within the cell 4. Triggers movement of intracellular vesicles containing facilitative glucose transporters to the cell membrane. Mechanism 2: The glucose receptors in the digestive tract are activated and release cholecystokinine (CCK) which stimulates the secretion of insulin. Mechanism 3: The food in the stomach stretches the receptors in the digestive tract, and these receptors send a signal to the integrating center in the neurons around the digestive tract. Integrating center in turn, sends a signal back via the nervous system, to the pancreas to release insulin.

Characteristics of Fertilization

A. Females use sperm storage to ensure uninterrupted reproduction: Sperm storage enables a female to fertilize her ova long after mating, which is adaptive in animals that might encounter mates infrequently. Ex) fruit flies can store sperm in the spermathecal for around one week, honeybees mated female can retain viable sperm for several years and also, some large snakes in captivity have laid fertilized eggs 5 years after mating. B. Polyandry- many males. -rare mating system occurring in less than 1% of all bird species. - polyandry is when one female mates with many males but male mates with only one female. In birds, there are two types: 1. Simultaneous: The eggs are fertilized from many male sperm, or sequential. 2. Sequential: the eggs are fertilized by one male, the female leaves, the male (stay) with eggs and she mates again. -Often, the polyandry is accompanied with role reversal; male incubates the eggs instead of female. C. embryonic diapause- some species interrupt normal development, pausing at an early phase of embryogenesis-significance: can help improve the odds of survival by controlling when birth takes place Two types of embryonic dispose: 1. Facultative diapause, which is induced by physiological conditions (suckling), and 2. obligate diapause, which is induced by season of the year. The process of embryonic diapause includes three phases: Onset, maintenance, and reactivation. D. Gene Imprinting- Even though both parents contribute equally to the genetic content of their offspring, sometimes there is an exclusive expression of specific genes from only one parent -Imprinted genes are more vulnerable to the negative effects of mutations, because the other parental gene is silenced. -Imprinting does not occur on every chromosome; only nine chromosomes are known to have regions of genes that are imprinted. -Imprinting occurs by a pattern of methylation: a copy of the gene to be inactivated is coated with methyl groups. This takes place before fertilization.

Hormones of Posterior Pituitary: oxytocin and ADH

Antidiuretic Hormone/ADH/Vasopressin: increases water absorption into the blood by the kidneys. Secretion regulated by water/salt balance. -Has vasoconstrictor effects in the vasculature -Prolonged high salt intake promotes pathological plasticity in the circuit that controls the secretion of vasopressin (negative feedback loop) Oxytocin: Stimulates contraction of the uterus during child birth (positive feedback loop). Stimulates mammary glands associated in milk ejection. Secretion regulated by the nervous system. -involved in several pathophysiological functions such as: autistic, anxiety disorders, and maternal depression.

colostrum

Colostrum is secreted during the first 48 to 72 hours postpartum, and only a small volume of colostrum is produced but it is sufficient for the newborn in the first few days of life. Colostrum is rich with immunoglobulins, which confer gastro-intestinal, and also likely systemic, immunity as the new born adjusts to a non sterile environment. The colostrum also has a trypsin inhibitor that protects the vital proteins in the colostrum from digestion in the infant's the gastrointestinal tract, and the infant's gastrointestinal track is able to transport antibodies intact to its own circulation.

Endocrinology in the Digestive System

Digestion involves the neuroendocrine system with the brain monitoring and releasing digestive hormones at distinct periods throughout the process. Mechanism 1. In the stomach, during the Gastric phase, protein detection causes glands to release two hormones, gastrin and histamine, which stimulate the production of hydrochloric acid and increase gastric juices that break down food into chime. 2. The arrival of chime in the duodenum causes the release of several hormones which shut down the digestive process in the stomach and will begin pacing the movement of chime through the rest of the system. 3. Gastric inhibitory peptide or GIP, slows stomach churning. 4. Secretin and cholecystokinin or CCK then induce the sphincter between the stomach and duodenum to close, limiting the release of chime: 5. Secretin also inhibits gastric juice production and, and stimulates the release of bicarbonates from the pancreas to neutralize the acidity of the chime 6. CCK stimulates digestive enzymes from the pancreas and bile from the gallbladder. 7. Peptide YY is a hormone released by the ilium, the end of the small intestine and the colon. It slows the movement of chime into the colon so that water and electrolytes can be readily absorbed. (Peptide YY is also like "I'm full" signal sent to the brain to halt the eating process.)

Downregulation and Upregulation of receptors

Downregulation: is the decrease in the number of receptor on the surface of target cells, making the cell less sensitive to a hormone or another agent. Ex) insulin receptors in type two diabetes. Ex) consumption of opioids, the number of opiate receptors on the target cell decreases in an attempt to reduce the intensity of the pleasure signal and maintain homeostasis so addicts must consume more and more of the drug in order to achieve the same effects. Upregulation: increase in the number of receptors on the surface of target cells, making the cell more sensitive to a hormone or another agent. Ex) there is an increase in uterine oxytocin receptors in the third trimester of pregnancy, promoting the contraction of the muscle of the uterus. Ex) Another example is caffeine, which binds antagonistically to receptors for the neurotransmitter adenosine. Binds without activating the receptor so acts as a stimulant remove the calming effect of adenosine. The brain responds to the removal of his calming signal by increasing the number of adenosine receptors on these brain cells, with the ultimate goal of homeostasis, restoring the normal brain activity.

the role of gut hormones in the control of energy homeostasis

Exposure of gastrointestinal enteroendocrine cells to ingested nutrients leads to secretion of gut hormones including CCK. Pancreatic polypeptides, insulin and amylin, are secreted in response to nutrient ingestion. In contrast, fasting leads to secretion of ghrelin from gastric cells. Leptin circulates in concentration proportionate to adiposity. And the gut hormones act on multiple organs and tissues including skeletal muscle and liver. In the central nervous system, they act directly and indirectly on nuclei, brainstem, hypothalamus, and reward centers. In the hypothalamus, the gastric hormone ghrelin activates the neurons that stimulate appetite. Anorectic peptides, including PYY and GLP-1, inhibit these neurons, suppressing appetite, and decreasing energy intake.

Transmembrane receptors consist of:

Extracellular binding domain, a membrane domain, and the intracellular domain. Their conformation change when the ligand binds to the receptor

Prembryonic state of development

Following fertilization, the zygote and its associated membranes continue to be projected towards the uterus by the action of the Falopian Tubes. During its journey into the uterus, the zygote undergoes five or six rapid mitotic cell divisions. Although each cleavage results in more cells, it does not increase its total volume. Each daughter cell produced by cleavage is called blastomere. Blastos means gem in the sense of a seed or sprout. After three days of fertilization, the embryo reaches the uterus, the cells are now compact, a look more like a solid mass. The name given to this structure is the morula means little mulberry. Once inside the uterus, the embryo freely moves for several more days. It continues to divide, creating a ball of approximately 100 cells, and consuming nutritive endometrial secretions called "uterine milk" while the uterine lining thickens. The ball of now tightly bound cells starts to secrete fluid and organize themselves around fluid-filled cavity. At this developmental stage, it is referred to as a blastocyst. Within this structure, a group of cells forms into an inner cell mass, which is fated to become the embryo. The cells that form the outer shell are called throphoblasts, ("throphe" means to feed or to nourish). The cells will develop into the chorionic sack or chorion and the fetal portion of the placenta (the organ of nutrients, waste, and gas exchange between the mother and the developing offspring), is called the placenta. >> And at the same time, the inner cell mass form the amniotic cavity, and the cells that surround the amniotic cavity differentiate to form the amnio. The remaining cells on the blastocyst inner cell mass form the embryo, which grows to become a fetus. The inner mass of embryonic cells is totipotent during this stage, meaning that each cell has the potential to differentiate into any type in the human body. Totipotency lasts only for a few days before the cell fates are set as being the precursors to a specific lineage of cells. As the blastocyst forms,the throphoblast excretes enzymes that begin to degrade the zona pellucida. In a process called "hatching", It breaks free of the zona pellucida in preparation for implantation. At the end of the first week, the blastocyst comes in contact with the uterine wall and adheres to it, embedding itself in the uterine lining via the throphoblast cells. Thus begins the process of implantation, which signals the end of the pre-embryonic state of development.

Types of receptors: G-protein receptor

Guanine nucleotide binding protein, that consists of a receptor protein associated with a G protein on the cytoplasmic side, G-protein interacts with the target protein, an enzyme or a channel protein G-protein-coupled receptors constitute the largest family of cell surface receptors. Mechanism: 1. Hormone-receptor binding conformation change in the receptor 2. G protein substitute GTP for GDP activation of G protein 3. The G protein interacts with another membrane protein (enzyme or channel protein) 4. Cellular response. Examples: Inositol signaling and adenylate cyclase

Types of chemical regulation

Hemocrine (Endocrine): The messenger molecule is released into the bloodstream and acts on a distant target tissue- the classical hormone. Paracrine (regulation of neighboring cells): the action of a secreted molecule from one cell on a neighboring target cell as I mentioned before, in detail, paracrine signals are released by one type of cell and act on another type. Ex) the type of cells in the stomach. They are called the enterochromaffin-like cells that secrete histamine. Histamine stimulates the production of acid by neighboring parietal cells. ex) Estrogens produced by the ovaries, and the estrogens act in the maturation of ovarian follicles before ovulation. autocrine (self regulation): Cell to cell regulation of local hormones Ex) A form of autocrine signaling is the secretion of Interleukin-1by macrophages, the binding of interleukin-1 by receptors of macrophages, (this is some type of cell of the immune system), further activates macrophages and triggers the secretion of more cytokines, including more interleukin-1. Direct Signaling: This is the contact dependent signaling in which a membrane-bound signaling molecule of one cell, binds directly to a plasma membrane receptor of another cell. Ex) immune responses, and also in cancer cells.

How do hormones produce specific biological effects?

Hormones are also referred to as ligands and agonists. When they are binding to a receptor results in a cellular response. Receptor must have high affinity and specificity for its hormone

Thyroid Disorders: Hypothyroidism v Hyperthyroidism

Hypothyroidism: a common endocrine disorder defined by a lack of thyroid hormones caused by autoimmune Hashimoto's thyroiditis Since iodine is not available to synthesize T4 and T3, hyper-stimulation from pituitary results in excessive growth of thyroid tissue. produces greater TSH levels than normal, which stimulates the thyroid to make more cells that make T3 and T4, but can't be made without iodine Hyperthyroidism: occurs when your thyroid gland produces too much of the hormone thyroxin (T4) Cretinism- fetal hypothyroidism happens in the fetal stages and results in severe mental retardation and growth defect due to the lack of TH during fetal development Myxedema- hypothyroidism later in life. Abnormal accumulation of water and protein throughout the body and disturbances in general metabolism, protein and fluid accumulation, alter the facial features, this can be fatal if not treated.

endocrine cells

In certain organs that the primary purpose is not endocrine, like for instance, the heart produces a hormone called atrial natriuretic peptide.

Inhibin

Inhibin is secreted by the gonads (by Sertoli cells in the male and the granulosa cells in the female ovaries) Role is to inhibit the production of follicle-stimulating hormone by the pituitary gland. Males: Inhibin is capable of feedback antagonizing follicle-stimulating hormone action by reducing the follicle stimulating hormone-releasing expression at ovarian level via a short feedback loop. It also inhibits the production of estrogen A negative feedback system occurs in the male with rising levels of testosterone acting on the hypothalamus and anterior pituitary to inhibit the release of an gonadotropin-releasing hormone, follicle stimulating hormone, and luteinizing hormone. The Sertoli cells produce the hormone inhibin, which is released into the blood when the sperm count is too high. Females: apart from their essential role in the selective control of follicle-stimulating hormone secretion, inhibins are currently recognized as paracrine ovarian (also testicular) regulators that have multiple paracrine effects in the utero-placental unit. In the human ovary, inhibin has been shown to increase androgen production by theca cells. theca cells use progesterone to produce androgens inhibin in females in the human ovary, increases then androgen production by these theca cells.

sex determination among mammals and birds

Mammals: Y chromosome is the one that determines the sex and a male results when the zygote is heterogametic (XY) and a female when is homogametic (XX) birds and butterflies: for instance, the female is the heterogametic (ZW) and the male is homogametic, ZZ. In other species, the sex is determined by many factors so the genotype is not the predictor of the sex like honey bees

Diabetes Pathophysiology: diabetes mellitus

Most common endocrine disorder. Insulin Dependent Diabetes mellitus (Type I Diabetes): -Insufficient insulin production. -autoimmune-mediated destruction of pancreatic beta cells -Rare cases: insulin made is defective because of altered gene -Most times: antibodies target a protein in insulin production pathway (when supposed to attack virus) Insulin Independent Diabetes Mellitus (Type II Diabetes): -Adult onset diabetes due to nonresponsive insulin receptors. Often referred to as Life-style disorder. -Receptors lose sensitivity when stimulated too often by insulin (the ligand) -Causes: eating too often, no exercise to stabilize blood glucose -Problem: osmolality of blood changes , blood is thicker so more pressure needed to push blood through body, kidneys work harder to get sugar out of blood diabetic coma: mainly caused by an extremely high or low blood sugar level

sexual and asexual reproduction

Most forms of asexual reproduction in animals are by parthenogenesis ("virgin birth") and in contrast to sexual reproduction, no male is involved. It is important in many species of invertebrates and the females reproduced by parthenogenesis when the second polar body fertilizes the ovum, we've seen before that the second polar body degenerates but in this case, fertilizes the ovum. In Thelytoky the homogametic females produce only female offspring. In Arrhenotoky, heterogametic females produce male offspring through parthenogenesis. In the honeybee, when the queen bee mates with a drone (this is the male bee) all the diploid individuals will become females with the DNA combined from the Queen and the drone. By contrast, drones are born by parthenogenesis, in which an egg from the queen will develop into a haploid drone.

Protein/Peptide/Amino Acid Hormones

Obtain the specificity from the primary amino acid sequence from post-translational modifications, specially glycosylation. Most of the hormones are produced as pro-hormones that are inactive or less active, are required the action of an enzyme to trim away the inactive sequences. synthesized in endoplasmic reticulum and sore in vesicles and later released by exocytosis in response to stimulus. Most are hydrophilic- soluble in body fluids with a few exceptions, like growth hormones, and circulate in blood having a short biological half-life. Cannot pass thru plasma membrane, must bind to transmembrane receptors with rapid effects Many protein hormones are small enough to appear in urine in a physiological active form. For example, the follicle stimulating hormone. Here we can see examples of amino acids- derived hormones, the tryptophan derived hormone and tyrosine derived hormone.

Hormones follow the same receptor-ligand interactions

One hormone may bind to multiple types of receptors and triggers multiple types of actions. A hormone may have different types of receptors on different target cells, different actions on different target cells. Ex) adrenaline/epinephrine: has effects on multiple tissues that gives an appropriate coordinated response to a situation of danger. Actions like increased heart rate, dilation or relevant blood vessels, especially those in skeletal muscle, constriction of blood vessels, especially in the skin and digestive, digestive tract, and mobilization of metabolic fuels such as glycogen in liver, skeletal muscle, or the stored fat in adipose tissue are all part of this response, the response of the adrenaline. These effects are mediated by two classes of structurally related receptors, the alpha and beta adrenergic receptors

The target cells of a lipid soluble hormone such as cortisol, are able to respond to it because of which of the following? a) Their genome includes the appropriate transcriptional response elements b) They have membrane bound cell surface receptors c) Only target cells express appropriate cytosolic receptors d) The hormone-receptor complex stimulates the phosphorylation/dephosphorylation of subsequent proteins in the signalling pathway

Only target cells express appropriate cytosolic receptors

High blood pressure can be a side effect of some medicines. Which of these can raise blood sugar? a) Ibuprofen b) Antidepressants c) Thyroid medicines d) Oral esteroid medicines

Oral esteroid medicines

MATERNAL CHANGES in PREGNANCY

Physiological changes occur in pregnancy to nurture the developing fetus and prepare the mother for labour and delivery: -Plasma volume increases progressively throughout normal pregnancy. Most of this 50% increase occurs by 34 weeks' gestation -Pregnancy causes a two- to three-fold increase in the requirement for iron -Changes in the coagulation system during pregnancy produce a physiological hypercoagulable state (in preparation for haemostasis following delivery -Changes in the cardiovascular system in pregnancy are profound, the cardiac output has already increased by 20%. The primary event is probably peripheral vasodilatation -There are also adaptive changes in renal vasculature: Renal vasodilation. Relaxin mediates vasodilation of renal arteries via nitric oxide (NO) synthesis. -Endocrine changes: Pregnancy is associated with a relative iodine deficiency. The causes for this are active transport of iodine from the mother to the feto-placental unit -Hypercortisolism in late pregnancy is the result of the production of corticotropin-releasing hormone by the placenta - one of the triggers for the onset of labour -The pituitary gland enlarges in pregnancy and this is due to proliferation of prolactin-producing cells in the anterior lobe. Serum prolactin levels increase in the first trimester and are 10 times higher at term. Levels of (FSH) and (LH) are undetectable during pregnancy due to the negative feedback from elevated levels of oestrogen, progesterone and inhibin. -Serum growth hormone levels are increased due to growth hormone production from the placenta -Oxytocin levels increase in pregnancy and peak at term

glucagon

Produced by a cells of endocrine pancreas - protein hormone. Hyperglycemic - increases blood glucose Acts through cAMP system Anabolic hormone that promotes: Glycogenolysis, Lipolysis, Gluconeogenesis Mechanism: The receptors in the pancreas sense decline in blood glucose levels (such as during periods of fasting) In response to this, the alpha cells of the pancreas secretes the hormone glucagon The activity of glucagon is regulated through a negative feedback mechanism; rising blood glucose levels inhibit further the glucagon production and secretion.

Normal blood glucose physiology

Rate of glucose entering the circulation balanced by the rate of glucose removal from the circulation Circulating glucose: -intestinal absorption during the fed state, -glycogenolysis (breakdown of glycogen by hepatic processes) -gluconeogenesis (the formation of glucose from lactate and amino acids during the fasting state) Glucoregulatory hormones: insulin, glucagon, amylin, epinephrine, cortisol, and growth hormone.

CONTRACTIONS of UTERINE MUSCLE

Receptors on the surface of myometrial cells that affect contractility: Oxytocin receptors: Contractility agonist Estrogen receptors: Contractility agonist Progesterone receptors: Contractility antagonist Beta2 adrenergic receptors: Contractility antagonist The positive feedback mechanism of oxytocin further catalyzes the onset of labor. While the smooth muscle growths in strength, progesterone disrupts excitation-contraction coupling to prevent the smooth muscle from contracting prematurely. Function: The primary function of uterine contractions is to expel the fetus from the uterine cavity. However, contractions also play an important role in minimizing postpartum bleeding Mechanism: -Some studies suggest mechanical stretch and hormones work together to initiate contractions in normal labor. However, due to the role of inflammation in preterm labor, other studies suggest that inflammatory mediators, such as cytokines and prostaglandins, initiate uterine contractions.

Cells that do not require insulin for reuptake

Red blood cells, brain, liver, kidneys, and the lining of the small intestine, do not have insulin receptors on their cell membranes

G-protein Inositol (IP3) signaling pathway

Regulates functions such as muscle contraction, glycogen degradation in the liver, water reabsorption in the vertebrate kidney, and immune function This Phosphatidylinositol- bisphosphate is an essentially lipid involved in metabolic processes, it is integral to cell membrane of all animal and acts as a second messenger in a variety of signaling pathways. The ultimate goal in this cascade is the activation of the serine/threonine PKC to alter the proteins and influence the transcription of genes and production of new proteins.

G protein signal transduction via adenylate cyclase

The G-proteins that interact with the cAMP signal transduction pathway can be excitatory and inhibitory. In this pathway PKA is involved and If the cAMP levels are low, the reaction tends to dephosphorylate target proteins. The signaling molecule, ligand or hormone binds to a receptor located on the cell membrane. The signaling process is not complete, the signal must be passed on through other molecules in the cell. Binding initiates a signaling pathway.

Embryonic development and positive pregnancy test

The blastocyst typically implants in the fundus of the uterus or on the posterior wall. However, if the endometrium is not fully developed and ready to receive the blastocyst, the blastocyst will detach and find ea better spot. A significant percentage (from 50 to 75%) of blastocysts fail to implant, when this occurs, the blastocyst is shed with the endometrium during menses. The high rate of implantation failure is one reason why pregnancy typically requires several ovulation cycles to achieve. The throphoblast secrets human chorionic gonadotropin hormone, hormone that directs the corpus luteum to survive, enlarge, and continue producing progesterone and estrogen to suppress menses during pregnancy. These functions of human chorionic gonadotropin are necessary for creating an environment suitable for the developing embryo. As a result of this increased production, human chorionic gonadotropin accumulates in the maternal bloodstream and is excreted in the urine Implantation is complete by the middle of the second week. Just a few days after implantation, the throphoblast has secreted enough human chorionic gonadotropin for an at home urine pregnancy test to give a positive result. Later in pregnancy, the placenta itself, becomes the main source of progesterone and estrogen, and the corpues luteum degenerates. In some mammals, the corpus luteum remains the main source of steroid hormones throughout the pregnancy. The placental membranes separates maternal blood from fetal blood. The fetal part of the placenta is known as the chorion. The maternal component on the placenta is known as the decidua basalis.

Ejaculation

The control of erection in a mammalian pennies is the result of a signaling pathway, depending on nitric oxide that activates a soluble guanylate cyclase, that in turn, stimulates PKG. Sperm are induced to swim by an external signal that activate them. Sperm alter activity in response to chemokinetic and chemotaxic molecules and depending on the reproductive strategy, the sperm might have to swim certain distance to encounter the eggs. The female reproductive tract releases chemo-tactic chemicals, (inducing the sperm to swim toward higher concentration of the agent) or chemokinetic chemicals (stimulating the sperm to swim faster, but not necessarily in any particular direction).

Endometrial Cycle

The endometrial cycle is as follows: Ovulation cycle parallels the endometrial cycle. -The Proliferative phase: endometrial cells are multiplying and spreading During this phase, estrogen levels rise. This causes the endometrium to thicken. The ovaries also prepared an egg for release. And at this time, the ovulatory cycle is in the follicular phase. There is an hypertrophy of the endometrium with blood vessels growing, epithelial and glandular cells replicating. -The secretory phase of the endometrium coincides with the luteal phase of ovulatory cycle. The endometrial cells secrete numerous regulatory factors, such as cytokines and prostaglandins. There are distinct changes in spiral arteries of the uterus, and they rapidly lengthen, outpacing endometrial thickening Menses follows the secretory phase hormones of cycle slide 21

hypothalamic-pituitary complex

The hypothalamus controls many functions such as heart rate, blood pressure, body metabolism, is involved in obesity and diabetes, stress, biological rhythms by alerting the pituitary gland to release certain hormones to the rest of the endocrine system HP complex ensures body homeostasis via secretion of several hormones that directly produces response in target tissues, as well as hormones that regulate other glands. Portal system: The axons of neurosecretory cells in the hypothalamus extend into the posterior lobe of the pituitary via magnocellular neuron (long axons) to release the antidiuretic and oxytocin hormones. They are stored in posterior pituitary until they are needed in the system. Parvocellular neurons (small) release their contents (the releasing or inhibiting hormones) in the hypophyseal artery. (targets anterior pituitary) The stored hormones are going to go to the anterior pituitary, and are going to be released to the different parts of the body.

Protein Kinases

The kinases are a group of protein that phosphorylate other proteins which activates other proteins

Ligand-receptor binding obeys the Law of Mass Action

The more receptor that is bound to the ligand, the greater the response in the target cell, but eventually the receptors could become saturated with ligands once all available receptors are bound to the hormone. most ligands bind reversibly to their receptors target cells with high concentration of receptors will be more sensitive to the presence of the of the ligand than target cells with lower concentration receptors.

oogenesis in the silk moth

The ova develops in four ovaries (ovarioles) and each contains many follicles arranged in series. The follicle closest to the gonopore undergoes oogenesis first, and after a couple of hours, the next follicle enters oogenesis and so on until the last one. The ova are released down the oviduct and then into the uterus where they are fertilized with the sperm that was collected and stored in the spermathecal after previous mating.

Gametogenesis: Spermatogenesis

The overall goals of spermatogenesis are: (1) to enable the male to transfer genetically recombined DNA by contributing to half of the offspring's genome (2) to equip the spermatozoa to effectively navigate through the female reproductive tract and deliver the genetic material to the ovum. -spermatogenesis: meiosis continues and each secondary spermatocyte divides to produce two haploid spermatids. -The testes are composed of the seminiferous tubules. -Sperm cells are produced within the walls of the tubules. -Sertoli cells nourish the immature sperm cells and transport sperm cells to central channel of the seminiferous tubule -Leydig cells produce regulatory factors that act on Stertoli cells to control spermatogenesis In the nucleus of the primary sperm cells there are 46 chromosomes; in each of the secondary sperm cells there and only 23 chromosomes, as there are in the egg. Mammalian spermatogenesis is characterized by a dramatic cellular change to transform the non-polar spermatogonia into the highly polarized, functional spermatozoon. The acquisition of the cell polarity is a requisite step for formation of viable sperm.

Endocrine Pancreas

The pancreas is a long organ, most of which is located posterior to the bottom half of the stomach primarily an exocrine gland involving the acinar cells that secrete a variety of digestive enzymes into the small intestine by the pancreatic duct BUT has endocrine functions too: The islets of Langerhans secrete the hormones: glucagon insulin, somatostatin (this is the growth hormone) and pancreatic polypeptide, endocrine function involves the secretion of insulin produced by beta cells, and glucagon produced by alpha cells within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body.

Hormones that control appetite: Ghrelin and Leptin

This perpetual drive to eat is periodically suppressed by inhibitory impulses, generated by the presence of food in the gastrointestinal tract, the flow of nutrients into the blood, and other factors. After this satiety factors have dissipated, they desire to eat returns. Key hormones: Ghrelin- which is termed "the hunger hormone", and tells our brain that we're hungry. It is produced by the stomach where it promotes appetite, how food is turned into energy, and storage of fat. Leptin: produced by fat cells when we eat and signals to the brain that we are full. Characteristics go leptin: synthesized and secreted predominantly by fat cells (or adipocytes) a major side of leptin receptors is in the hypothalamus, which is known to play an important role in control of food intake, and metabolic rate. has the characteristic that the plasma levels of leptin rise and fall in parallel with body fat content. As body fat mass increases, so does the concentration of leptin in blood. Injection of leptin into leptin deficient animals leads to reduction in body weight by suppressing food intake and increasing metabolic rate and energy expenditure.

Prolactin

Two functions: milk production and also has influence in maternal behavior. In mammals, prolactin and steroid hormones work in conjunction to alter the biochemistry of the brain and behavior of the female. Female mice with prolactin receptors knocked out show less interest in caring for their pups. Paternal care is also controlled by prolactin, and the degree paternal behavior and is linked to both hormonal change and experience. The attending fathers usually have higher levels of prolactin in the blood than do non- paternal males. -During pregnancy, prolactin stimulates growth of the breast, but high estrogen and progesterone secretion prevent milk production -Prolactin Releasing Hormone (PRH) and nursingof a baby stimulate the release of Prolactin, there's no negative feedback loop from the mammary gland for prolactin! -Suckling, via neural connections inhibits dopamine secretion, increasing prolactin secretionand stimulating milk production in the breast

In the two-cell stage during embryonic development, there is a division of the parental genomes that allows for a differential influence a. True b. False

a

When the native binding site of a ligand to its receptor is preferred to other binding sites on the same receptor, we can talk about: a. Specificity b. Enzymatic site c. Affinity d. Transmembrane domain e. Conformational change

a

Which of the following is true about vitellogenesis? a. The mixture of proteins and lipids are retained during oogenesis b. Occurs during fertilization and the fertilized egg stores the proteins and lipids inside the yolk sac c. The pathway begins in the liver (from either invertebrates or vertebrates) d. In mammalians, the yolk sac is abundant e. Some of the nutrients are produced by the embryo

a

melanocyte-stimulating hormone (MSH)

a collective name for a group of peptide hormones produced by the skin, pituitary gland, and hypothalamus. production by the skin and pituitary is enhanced and this plays a key role in producing a colored pigmentation found in the skin, hair, and eyes. It does this by inducing specialized skin cells called melanocytes to produce a pigment called melanin. Melanin protects cells from DNA damage which can lead to skin cancer or melanoma, although named for its stimulatory effect on pigment cells melanocyte-stimulating hormone produced in the hypothalamus can also suppress appetite by acting on receptors in the hypothalamus in the brain. Melanocyte stimulating hormone also affects a range of other processes in the body, it has anti-inflammatory effects, and can influence the release of the hormone aldosterone, which controls salt, and water balance in the body as we already know. not thought to be controlled by a direct feedback mechanism.

Cyclic GMP

a second messenger molecule that modulates a variety of downstream effects including vasodilation, retinal phototransduction, calcium homeostasis, and neurotransmission.

Bisphenol A (BPA)

a well-characterized endocrine disruptor compound Polycarbonate plastic are often used in containers that store food and beverages such as water bottles Experimental studies suggested that prenatal, perinatal, and postnatal exposure to BPA can impair several steps of ovarian development, induce ovarian morphology rearrangement. and impair ovarian function, as well as can impair uterus morphology and function in female adult animal and offspring. BPA already has been linked to obesity in both human and animal studies. The associations are especially prevalent for children exposed while they are developing. Also, BPA is a concern because of possible health effects of the brain of fetuses, infants and children, and it can also affect children's behavior. Additional research suggest a possible link between BPA and increased blood pressure and has been reported to adversely impact the central nervous system, especially with respect to learning and memory. BPA affects the neuronal activity of the chick embryo. Now we have some questions, a few questions about the past lectures. In the next lecture is going to be reproduction.

saturation

all the binding sites are occupied, meaning that there is no further increase in binding with increasing ligand concentration receptors will be saturated at high ligand number more free ligands or receptors will increase the response until saturation is reached

Hormone types

amino acid derivative: dopamine, catecholamine, and thyroid hormone. interact with cells surface membrane receptors small neuropeptides: gonadotropin releasing hormone or thyrotropin releasing hormone. interact with cells surface membrane receptors large proteins: insulin or luteinizing hormone interact with cells surface membrane receptors steroid hormones: cortisol, and estrogen that are synthesized from cholesterol based precursors interact with intracellular nuclear receptor, although many also interact with membrane receptors or intracellular signaling proteins as well. vitamins derivatives: retinoids (this is Vitamin A or Vitamin D). interact with intracellular nuclear receptor, although many also interact with membrane receptors or intracellular signaling proteins as well.

species that use internal fertilization

arthropod, reptiles, and some fish possess a copulatory organ or intromittent organ birds are the exception because they transfer the sperm directly from the male's cloaca to the female's cloaca.

In the myometrial contractions, a. Activation of progesterone receptors induces uterine contraction b. Hypothalamus and uterine lining synthesize oxytocin c. None of the answers are correct d. Activation of B2 receptors induce myometrial contractions e. All answers are correct

b

What hormone is consistently positively correlated with thickening of the endometrium? a) Progesterone b) Estrogen c) LH d) FSH

b) Estrogen

Which of the following statements about the menstrual cycle is false? a. Progesterone levels rise during the luteal phase of the ovarian cycle and the secretory phase of the uterine cycle b. Menstruation occurs just after LH and FSH levels peak. c. Estrogen levels rise before ovulation, while progesterone levels rise after d. Menstruation occurs after progesterone levels drop e. In the absence of fertilization, progesterone levels decline due to atresia of the corpus luteum

b.

animal developmental stages

begins with a single cell which divides repeatedly and have different stages. These stages are zygote, blastula, and gastrula that differentiate to form tissues in the morphogenesis The primary sex characteristics, are the gonads and are acquired during the embryonic stage and develop with the ultimate goal of mating, which is under the influence of environmental conditions.

receptor antagonists

bind to a receptor. and lock the receptor in an inactive state in which the receptor is unable to induce a cellular response

Hormones can mediate changes vis

binding directly to intracellular hormone receptors to modulate gene transcription or bind to cell surface receptors to indirectly stimulate signaling pathways

receptor agonist

binding to a receptor results in a cellular response

Polyestrous animals: a. All the answers are correct b. None of the answers are correct c. Undergo estrous cycles through the year d. Have multiple estrous cycles seasonally Have only one estrous cycles through the year

c

Based on your knowledge of hormones, which of the following will be transported in the plasma by being bound to a binding protein? a) Oxytocin b) antidiuretic hormone c) testosterone d) epinephrine

c) testosterone

Hyperglycemic hormone control in invertebrates

case study in circulating glucose regulation by crustacean hyperglycemic hormone. crustacean has neurohormones termed crustacean hyperglycemic hormone (CHH) that plays a principal role in glucose regulation, and it is greatly different than in mammals. These neurohormones regulates blood glucose via a negative feedback mechanism.

Types of receptors: enzyme linked protein receptors

cell-surface receptors with intracellular domains that are associated with an enzyme Types of receptor-enzymes: 1. The receptor guanylate cyclases that convert GTP to c-GMP Mechanism: The extracellular receptor domain recognizes specific peptide ligands like the atrial natriuretic peptide and changes its conformation. Then, the activated receptor catalyzes the conversion of GTP to cyclic GMP. The cyclic GMP acts as a second messenger within the cell. The second messenger, cGMP, binds to a protein called c-GMP-dependent protein kinase, and the signal is amplified through the cell (phosphorylation cascade). Atrial natriuretic peptide lowers the blood pressure as part of negative feedback system to regulate the blood pressure 2. tyrosine kinases: play an important role in a variety of cellular processes including growth, motility, differentiation, and metabolism. Misregulation can be cancer causing Ligands include: insulin, epidermal growth factor, or vascular endothelial growth factor. Mechanism: When a chemical messenger binds to the receptor, associates with other same type receptor and form dimers in the membrane. The coupled receptors phosphorylate each other in a process called autophosphorylation. The phosphorylated receptors interact with intracellular signaling proteins called kinases and these kinases signal, they are going to signal to Ras proteins, (Ras is an intracellular GTP-ase switch protein), that switches between the active and inactive forms and activates a serine/threonine phosphorylation cascade. The insulin receptor is a crucial tyrosine kinase receptor and functions as a dimer. 3. Mitogen activated protein (MAP) Kinase: plays role in many aspects of immuno-mediate inflammatory responses. Mechanism: Ras activates the MAP-KKK, that phosphorylates other MAP-kinase that results on a phosphorylation cascade that greatly amplifies the original chemical signal. 4. the receptors serine/threonine kinase: directly activate the phosphorylation cascade without activating Ras proteins. Mechanism: The ligand binds and changes its confirmation once activated. Then phosphorylates other proteins activating a phosphorylation cascade that greatly amplifies the signal in a target cell. Ex) Transforming growth factor beta, (TGF beta receptor) mutation in this receptor has been linked in the development of human cancers. Transforming growth factor type beta (the family ligands) are pleiotropic, so they have different, pleiotropic cytokines and regulate proliferation and differentiation of many cell types. TGF beta mediates its effects by binding to and activating cell surface receptors that possess serine/threonine kinase activity.

Many substances can be both paracrine and endocrine regulators of the GI function

cholecystokinin, which is released from the duodenum, in response to dietary protein and lipid acts locally on nerve terminals in a paracrine fashion and also affects the pancreas.

Gonadotropes are receptors: a. Located in the gonads b. Located in the Fallopian Tubes c. Located in the neurophypophysis d. Located in adenohypophysis e. Located in Hypothalamus

d

control mechanisms involved in the regulation of gastrointestinal function: endocrine, paracrine and neuroendocrine.

endocrine: Sensing cell in the GI tract, enteroendocrine cell (EEC), responds to a stimulus by secreting a regulatory peptide or hormone that travels via the bloodstream to target cells different from the point of secretion. Examples of endocrine hormones: gastrin, CCK, secretin. paracrine: Paracrine regulation describes the process whereby a chemical messenger or regulatory peptide is released from a sensing cell, often an EEC, in the intestinal wall that acts on a nearby target cell by diffusion throughthe interstitial space. Example of paracrine hormones: CCK, secretin. -Paracrine agents exert their actions on several different cell types in the wall of the GI tract, including smooth muscle cells, absorptive enterocytes, secretory cells in the glands, and even other EECs. -paracrine mediators like prostaglandins, adenosine, nitric oxide and histamine are capable of producing changes in GI function. -histamine: diffuses through the interstitial space to neighboring parietal cells and stimulates the production of acid. Serotonin released from enteric neurons, mucosal mast cells, and specialized EEC cells called enterochromaffin cells, regulate smooth muscle function and water absorption across the intestinal wall. neuroendocrine: Nerves and neurotransmitters play an important role in regulating the function of the GI tract. In its simplest form, neural regulation occurs when a neurotransmitter is released from a nerve terminal located in the GI tract and the neurotransmitter has an effect on the cell that is innervated. Example: gastrin cells in the antrum of the stomach are innervated by excitatory neurons that utilize gastrin releasing peptide as the primary neurotransmitter - has sensory neuron, an interneuron, and the secretor motor neuron.

Gametogenesis: Oogenesis

gametogenesis: The gametes are formed by the process of meiosis -oogenesis: the primary oocyte growths and remains quiescent for a very long time. Later it will divide. Then the primary oocyte divides asymmetrically, in secondary oocyte and the first polar body, this one will be degraded. Secondary oocyte divides asymmetrically, again and results in the mature ovum, and also, a second polar body that will be degraded too. the primary oocyte is diploid, by meiosis gives rise, secondary oocyte, and the first polar body is going to be degraded, and then, is going to divide again (the secondary oocyte) giving the mature ovum and another second polar body that's going to be degraded. In the spermatogenesis what happens is that the secondary spermatocyte divides continuously giving spermatids and then mature in the sperm.

hormones secreted by the GI tract: gastrin

gastrin: released from enteroendocrine cells located in the wall of the distal part on the stomach. Release is stimulated by activation of parasympathetic outflow to the GI tract, gastrin potently stimulates gastric acid secretion in the postprandial period which is after meals.

thyroid gland: parathyroid gland and PTH

gland is embedded in the posterior surfaces of thyroid gland where they continuously monitor and regulate blood calcium level. Produces parathyroid hormone (PTH) that is essential for life. PTH controls calcium metabolism. PTH is Hypercalcemic - increases blood calcium by increasing bone resorption, increasing renal tubular resorption, and Ca++ uptake from the gut. Mechanism stimulates the calcium re-uptake by the kidneys, and also stimulates the calcium release from bones. The active vitamin D increases the calcium uptake in the intestine, and this calcium level in the blood rises, achieving homeostasis. acts antagonistically with calcitonin

Falopian Tubes

have small hair-like projections called cilia on the cells of the lining. These tubal cilia are essential to the movement of the egg through the tube into the uterus. Following fertilization, the zygote and its associated membranes continue to be projected towards the uterus by the action of the Falopian Tubes.

Hormonal disfunction: hypofunction and hyperfunction

hormone concentration in blood affected by an inactive, under- active or overactive endocrine gland, may also result from inefficient hormone synthesis or metabolism or receptor disfunction Hypofunction: can be caused by lack of active hormone or by hormone resistance as a result of inactivation of hormone-receptor, or both receptor defects. ex) testicular feminization syndrome, in which the androgen receptor is mutated and cannot be activated by androgen. The androgens in these patients increase in levels and are converted peripherally to estrogens, then the individuals are genetically male but have a strongly feminized external phenotype. Hyperfunction: results from ovestimulation by the pituitary but is most common due to enlargement of the gland itself, many times due to benign pituitary cancer. Can be due to antibodies that can stimulate peripheral endocrine glands, as occurs in hyperthyroidism. Enzyme defects in the synthesis of peripheral endocrine hormone can result in over production of hormones.

signal amplification

hormones are produced in small quantity but their effects are large and diverse the signal amplification after the ligand binds to the receptors and cause a conformational change. there is a cascade of effects. ex: the epinephrine binding to beta adrenergic receptors. Epinephrine is the adrenaline. The amplification signal is as follows: >> The hormone binds to receptors on the plasma membranes surface and triggers a signaling pathway to change the cells activity by inducing production of various cell products that affect the cell in the short-term. The hormone is called a first messenger, we can see here. >> And the cellular component is called a second messenger. >> G-proteins activate the second messenger cyclic AMP triggering the cellular level response, response to hormone binding is amplified as the signaling pathway progresses.

Gonadotropins (FSH and LH)

hormones synthesized and released by the anterior pituitary which acts on the gonads (testes and ovaries) GnRH is released from hypothalamus to anterior pituitary which stimulates release of LH and FSH which act on gonads Mechanism: The hypothalamus receives signals from the brain and blood hormones, and results in releasing gonadotropin releasing hormones (GRH) into the pituitary. the parvocellular neurons in the anterior pituitary receive the signals through the portal vessels and secrete luteinizing and follicle stimulating hormones are released into the blood and transported to the gonads when they start synthesizing steroid hormones The LH hormone and follicle-stimulating hormone are gonadotropins, what means that stimulate the gonads (in males, the testes and in females, ovaries) and are essential for reproduction. FSH and LH are secreted by the anterior pituitary gland. FSH is present in the plasma of males and females of all ages. FSH stimulates growth and maturation of ovarian cells, the follicle; stimulates estrogen secretion and also, (both of them) promote endometrial changes, (changes in the uterus); stimulates spermatogenesis in males Sertoli cell: produces androgen binding globulin Leydig cell: produces testosterone in the presence of LH Luteinizing hormone, plays a key role in gonadal function, and in synergy with follicle-stimulating hormone stimulates follicular growth and ovulation. Thus, normal follicle growth is the result of complementary action of follicle stimulating hormone and luteinizing hormone. In the males LH stimulates some cells to produce the testosterone.

Tropic hormones

hormones that have other endocrine glands as their target.

hydrophillic v hydrophobic chemical messengers

hydrophillic: stored in intracellular vesicles secreted via exocytosis transported via dissolved in extracellular fluids binds transmembrane receptors rapid effect hydrophobic: not stored, synthesized on demand secreted via diffusion across membrane short distance transport- dissolved in extracellular fluid long distance transport- bound to carrier proteins slower effects

pleiotropic action

in target tissue, hormone may lead to multiple responses ex) insulin

homeostatic regulation of the levels of blood glucose

insulin and glucagon act antagonistically Blood glucose concentration is tightly maintained between 70 and up to 100 milligrams per decilitre. If blood glucose concentration rises above this range, insulin is released, which stimulates the body cells to remove glucose from the blood. If blood concentration drops below the range glucagon is released, which stimulates body cells to release glucose into the blood. insulin lowers blood sugar, the glucagon raises it.

progesterone, androgens, and estrogens

typical reproductive hormones Steroids hormones regulate diverse physiological functions: secondary sexual characteristics, responds to stress, neuronal functions, and various metabolic processes. They are synthesized from cholesterol, mainly in the adrenal gland and gonads, in response to tissue-specific specific tropic homes. the reproductive hormones share similar structure

Thyroid gland: Calcitonin

involved in helping to regulate levels of calcium and phosphate in the blood (opposing the action of parathyroid hormone) a hormone that is produced in humans by parafollicular cells, (commonly known as C-cells) of the thyroid gland. decreases blood calcium (hypocalcemic) by inhibiting calcium uptake in the gut, and increases bone mineralization. very important in childhood because stimulate the bone growth and the mineral deposition in the skeleton. Also appears to be important in reducing the loss of bone mass during prolonged starvation, and in the late stages of pregnancy, when the maternal skeleton competes with the developing fetus for calcium ions absorbed by the digestive tract. Mechanism: Calcitonin is released following stimulus (rise in blood calcium levels) Gland is stimulated and calcitonin is released acts on the kidneys that stimulates the calcium excretion, and also stimulates the calcium uptake by bones. The blood calcium level falls and is reached the homeostasis which is a certain amount of blood calcium level. acts antagonistically with PTH

Types of receptors: ligand gated ion channels:

ligand gated ion channels: The channel is closed when there is no ligand bound to the receptor. When the ligand binds, the channel changes its conformation and the channel opens to some ions. But sometimes the channel is open, and when a ligand or hormone binds the channel closes. Ligand-gated ion channels are large multisubunits, four or five unit receptors that form a membrane ion channels that when open, allows the passage of sodium, potassium, calcium or chloride. Once the receptor channel complex is activated, the membrane potential may become depolarize or hyperpolarize depending on the direction of the ion flow and the ion involved. Typically each subunit contains 4 hydrophobic transmembrane domains linked by hydrophilic groups. Activation of this channel leads to a rapid response about milliseconds, allowing ions to flow down their electrochemical gradient. Nicotinic cholinergic, GABA, and 5HT3 (serotonin) receptors are examples of ligand-gated ion channels sites.

Steroid Hormones

made by the adrenal cortex, ovary, testis, and the placenta. These hormones are basically modifications of cholesterol molecule. Steroid hormones are hydrophobic and pass through cell membrane easily. The classic steroid hormones are located intracellular and regulate the gene expression, although there are some steroids receptors that mediate non-genomic action of steroid hormones. Steroid hormones also include the vitamin D

renin-aldosterone system

manages blood pressure and osmoregulation Mechanism: 1. As the nephrons are filtering blood, juxtaglomerular cells monitor blood pressure, and if they detect a decrease in pressure, they released the hormone renin into the bloodstream. 2. The drop in pressure induces the release of one hormone, renin by these cells into the bloodstream. 3. Renin then interacts with angiotensin antigen, a precursor molecule released by the liver and cleaves it into the hormone angiotensin one. 4. Meanwhile, and enzyme released in the lungs called Angiotensin Converting Enzyme or ACE, converts angiotensin one into angiotensin two. (Angiotensin two has two functions: One is a vasoconstrictor, constricting small blood vessels and temporarily increasing blood pressure. And the other to induce the release of the hormone aldosterone from the adrenal cortex.) 5. When aldosterone reaches the brain, it stimulates the release of anti-diuretic hormone or ADH, from the hypothalamus. 6. Together, ADH and aldosterone then stimulate the kidneys to increase the reabsorption of water and sodium from the nephrons, which increases renal blood volume and overall blood pressure hormones are interconnected

Configurations of negative feedback loops v positive

negative: gives stability by keeping physiological parameters within a normal range. Two basic configurations of neg: 1. response driven feedback loop The response-driven feedback loop is observed in these endocrine glands: The glands that control blood glucose level (pancreatic islets), glands that control blood calcium (parathyroid glands), or also blood osmolarity and volume, (the hypothalamus/posterior pituitary gland) and the glands that control blood sodium, potassium or hydrogen levels. In the response-driven configuration, the secretion of a hormone is stimulated or inhibited by a change in the level of a specific extracellular parameter, like an increase in blood glucose level that stimulates insulin secretion. 2. endocrine-axis driven feedback- the primary feedback loop involves feedback inhibition of pituitary tropic hormones and hypothalamic releasing hormones. Each axis consists of the hypothalamus, pituitary gland, and the peripheral endocrine glands An important aspect of the endocrine axis is the ability of descending and ascending neuronal signals to modulate the release of the hypothalamic releasing hormones and controlling the activity of the axis (Ex: SCN) Mech: hypothalamic neuroendocrine neurons, that secrete releasing hormones. Then the releasing hormone stimulates the production and secretion of tropic hormones from the pituitary gland, then, the tropic hormones must stimulate the production and secretion of hormones from peripheral endocrine glands that have pleiotropic actions on numerous cell types. Positive: There are also a few examples of positive feedback in endocrine regulation. A positive feedback loop in which a hormone increases levels of a specific component, and this component stimulates secretion of the hormone confers instability. Ex) control processes that lead to rupture of a follicle through the ovarian wall, or, as we already know, expulsion of a fetus from the uterus.

chemical messengers

neurotransmitters- the chemical is released from a neuron at a specialized cell-cell junction called synapse. The chemical diffuses to the post-synaptic target cell, and binds to the receptors. Has local effects only. T neurohormones- hormones they are chemical released from a neuron, or an endocrine cell or another type of cell, and travels through the blood to have different effect on target cells. different than neurotransmitters because they travel in blood, and have widespread effect rather than only local effect. paracrine factors- The chemical is released from a non-neuronal cell and diffuses locally through the interstitial fluid to act on nearby targets cells. Not specialized junction is required in the paracrine agent and also has local effects. autocrine factor: The chemical is released from a non-neuronal cell and acts on the same cell that released it. this is basically a subset of paracrine

Hormones

organic molecules secreted by a specific cells in the blood vascular system or extracellular fluid, and produce their effect, generally, at some distance from the site of production. Site of action could be a short distance away, so we call them local regulators, or far away, and we call them hormones.

pineal gland and melatonin

place of melatonin production and regulation Melatonin plays a role in regulating sleep patterns or also called circadian rhythms. contains special secretory cells called pinealocytes These cells synthesize hormone melatonin from molecules of neurotransmitter serotonin (derives from the amino acid tryptophan) The body produces melatonin in response to light hitting the retina on the eye. Light reception inhibits the release of melatonin, and in contrast, the absence of light at night time will be read as a signal to produce more melatonin (necessary to regulate sleep) the human retina that emit a signal to the suprachiasmatic nucleus (SCN) of the hypothalamus. (possible negative feedback loop) Other pineal functions (regulated by melatonin): -Light sensitivity -Role in the timing of puberty: -Antioxidant Effects -Alzheimer Disease (Reduced pineal gland volume and pineal calcification, accompanied by cognitive decline)

Capacitation of sperm

process by which spermatozoa become activated for fertilization; occurs in the vagina An important feature of spermatogenesis is the change in the cytoskeleton that occurs throughout this pathway. In some species, the sperm released from the males are not yet capable of fertilizing an egg, so has to go on under capacitation, (capacitation after they entered the female reproductive tract). It is exposed to regulatory factors that change the sperm metabolism and make it capable of fertilizing the ovum. -Spermatogenesis is initiated through the neurological axis by the hypothalamus, which releases gonadotropin releasing hormone, which in turn, signals follicle stimulating hormone and luteinizing hormone to be transmitted to the reproductive tract. -Luteinizing hormone interacts with Leydig cells to produce androgens. -Follicle stimulating hormone interacts with Sertoli cells that provides support and nutrition for the sperm proliferation and development.

Stages of the Estrous Cycle:

proestrus, estrus, metestrus, diestrus •1-Proestrus•follicle enlarges•estrogen increases•vascularity of the female reproductive tract increases•endometrial glands begin to grow•estrogen levels peak• 2-Estrus•allows male to mount•estrogen decreases•LH surge occurs•ovulation 24-48 hr after surge of LH•uterine motility high with contractions moving toward oviduct•sperm transport is optimal•cervical mucus volume increases• 3-Metestrus•estrogen low•corpus hemorrhagicum present•ovulation in cow•uterus•contractions subside•endometrial glands continue to grow and become coiled•in cattle bleeding occurs•FSH increases, triggering growth of follicles• 4-Diestrus•progesterone high•FSH low but increases at some point to cause growth of pre-ovulatory follicle•Uterus•secrets fluid but the volume of fluid decreases over time•contraction stop•corpus luteum regresses at the end of this period if female is not pregnant

RAS

protein that activates many phosphorylation cascades in the cell and participates on cellular growth and metabolism. Mutations in the genes encoding RAS accounts, account for 30% of the human cancers.

Amniotes

reptiles, birds, mammals Amniotes that lay eggs the shell of the egg provides protection for the developing embryo while being permeable enough to allow for the exchange of carbon dioxide and oxygen. The albumin (or egg white) provides the embryo with water and protein, whereas the fattier egg yolk, is the energy supply for the embryo, as is the case with the eggs of many other animals, such as amphibians. However, the eggs of amniotes contain three additional extra embryonic membranes: the chorion, ammnion, and allantois. Extra embryonic membranes, are membranes present in amniotic eggs that are not part of the body of the developing embryo. The inner amniotic membrane surrounds the embryo itself, the chorion surrounds the embryo and yolk sac. The chorion facilitates exchange of oxygen and carbon dioxide between the embryo and the egg's external environment. The amnios protects the embryo from mechanical shock and supports hydration. The allantois stores nitrogenous wastes produced by the embryo and also facilitates respiration. In mammal's membranes that are homologous to the extra embryonic membranes in eggs are present in the placenta.

Synergistic Actions of Hormones

results of study involving injection of Glucagon, epinephrine, and cortisol in dogs: When the hormones are injected alone, they cause an increase in blood sugar. When the glucagon, and epinephrin are injecting together the increase in blood glucose is equivalent to the sum of the increase of each hormone. And this is called additivity. When the three hormones are injected in combination, the net effect is much greater than the sum of the effects observed when one hormone is injected alone. This is synergism Another example: when two hormones are required for an adequate response: both follicle stimulating hormone from the pituitary gland and estrogens from the ovaries are required for the maturation of the female ova

anterior pituitary (adenohypophysis)

secretes various Tropic Hormones that stimulate various peripheral endocrine glands Hormones include: FSH, LH, ACTH, TSH, prolactin, GH, MSH, and endorphins

milk composition among mammals

slide 16 the milk for marine mammals, for instance, can be in excess of 60% of lipids, important for the needs of insulation. Lipids provide both energy and bio-synthetic precursors and sugars are also a source of energy, and serve as biosynthetic precursors as well. The milk protein is called casein that is a source of amino acid. This is protein, is highly phosphorylated, so binds high amount of calcium that the infant will need.

Main modes of reproduction: ovipary, ovovivipary, and vivipary

slide 8 Ovipary refers to the development of an embryo within an egg outside the mother's body. This occurs in most amphibians, and reptiles, and in all birds. Ovovivipary, refers to the development of an embryo inside an egg within the mother's body until it hatches, the mother provides no nourishment to the developing embryo inside the egg. This occurs in some species of fish and reptiles. Vivipary refers to the development and nourishment of an embryo within the mother's body. Birth may be followed by a period of parental care of the offspring. This reproductive strategy occurs in almost all mammals.

Thyroid hormones (T3 and T4)

thyroxin, also known as T4, and triiodothyronine, also known as T3 Thyroid hormones facilitate: 1. Somatic growth (tissue and bone) 2. Brain Development - Differentiation 3. Intermediary metabolism (regulates entire metabolism) • Determines how much ATP we'll produce 4. Thermogenesis (maintain body temp, by using calories) 5. Oxygen consumption / Respiratory metabolism 6. Reproduction 7. Hair growth in mammals (humans) / Molting in birds 8. Amphibian metamorphosis (tadpoles to frogs) and differentiation derivatives of the amino acid tyrosine Thyroid follicles of thyroid gland serve as both factory and storage for production of thyroid hormone Synthesis Mechanism (negative feedback): 1-THS secreted by the anterior pituitary in response to feedback from circulating thyroid hormone acts directly on the TSH receptors expressed on the thyroid follicular in the thyroid gland and stimulates multiple biosynthesis steps 2-Thyroglobuline are secreted by exocytosis from the thyroid follicular cell to the follicle colloid 3-Thyroperoxidase catalyzes both iodination and coupling reactions. T3 and T4 are released from thyroglobulin. 4-Both T3 and T4 are released into serum, iodine is recycled and the colloid contains hormone reserve.

Second messenger

small molecules that carry signals received at receptors on the cell surface to target molecules in the cytosol or in the nucleus also amplify the strength of the signal three major classes: 1. cyclic nucleotides, (for instance, cAMP and cGMP) -Enzyme adenylyl cyclase converts ATP to cAMP. -Enzyme phosphodiesterase converts cAMP to AMP. Ex) epinephrine-stimulated cAMP synthesis: the stimulatory effects of epinephrine are mediated through the activation of cAMP resulting in the stimulation of kinase phosphorylation cascade that act to increase heart rate or to dilate blood vessels in skeletal muscles, and to break down also the glycogen to glucose in the liver. 2. inositol triphosphate (IP3) and diacylglycerol (DAG) IP3 Mech: ligand binds to endoplasmic reticulum calcium channels releasing calcium in the cytoplasm. IP3 phosphorylates IP4 and this also leads to diverse actions. DAG and calcium activate PKC, as we can see here, and also leads to a different responses. 3. calcium ions have critical role in the rapid response of neurons and muscle cells for contraction, as well as fertilization and neurotransmitter release second messenger in G-protein and tyrosine-kinase pathways. activates calcium calmodulin which binds many kinases, phosphatases, and signaling proteins, and also structural proteins affecting a wide variety of processes, including neurotransmitter release, muscle contraction, metabolism, apoptosis, inflammation, membrane protein organization, and also cytoskeleton movement. Mechanism: At rest, cells maintain a low concentration of calcium in the cytoplasm, expending energy to pump these ions out of the cell. When activated, cells rapidly increase the cytoplasmic calcium concentration by opening channels in the cell membrane, which allow calcium ions outside the cell to enter rapidly. various protein pumps transport Ca++ outside the cell or inside the endoplasmic reticulum or other organelles. the amount and duration of the flow of calcium will determine the type and duration of its effect on Intracellular signaling.

Endorphins and beta-endorphins

small peptides, that bind to opioid receptors in the central nervous system. beta-endorphins- neuropeptides involved in pain management, possessing morphine-like effects, and are involved in natural reward circuits such as feeding, drinking or maternal behavior Endorphins Mechanism: Beta endorphins produce analgesia, (abolish the pain) by binding to opioid receptors mu, at both pre- and postsynaptic nerve terminals. When bound, a cascade of interaction results in inhibition of the release of substance P (a key protein involved in the transmission of pain) Beta endorphins Mechanism: bind mu opioid receptors and exert their primary action at the presynaptic nerve terminals. Instead of inhibiting substance P, they exert their analgesic effect by inhibiting the release of gaba, an inhibitory neurotransmitter resulting in excess production of dopamine. Dopamine is associated with pleasure.

specificity and affinity

specificity: the hormones the hormones can distinguish the highly specific binding partner from less specific partners. >> Binding of a hormone to its receptor involves the same type of interaction as those between an enzyme and its substrate. affinity: allows the specific hormone with high affinity to remain bound even if there are high concentrations of less specific partners with lower affinity. The dissociation constant describes the affinity between receptors, and their ligands.

The male reproductive tract

sperm is released from the wall of seminiferous tubules and carried along their reproductive tract, and as they pass through epididymis and vas deferens the secretions from the accessory glands provide seminal fluid. slide 21 The internal organs of the male reproductive system: vas deferens, epidydimis, seminal vesicle, prostate gland, and bulbourethral (Cowpers gland) -the vas deferens transports mature sperm to the urethra in preparation for ejaculation seminal vesicles, sac-like pouches that attach to the vast deference near the base of the bladder, the vesicles produced molecules such as fructose, that serves as energy source for sperm. -The seminal vesicles produces the seminal fluid that is alkaline to neutralize the acidic of ovarian fluid to allow the sperm to swim. -The prostate gland, is a walnut-size structure located below the urinary bladder, urinary bladder in front of the rectum, it contributes additional fluid to ejaculate that serves as nourishment for sperm. -The bulbourethral gland, or Cowper's gland are pea-size structures located on the size of the urethra just below the prostate gland. This glands produce a clear, slippery fluid that empties directly into the urethra. The fluid produced by these glands lubricates the urethra and neutralize acidity associated with residual urine. The external organs of the male reproductive system: penis, scrotum, epididymis, and testes. -The penis is the male sexua organ for intercourse and urination, Semen and urine leave the penis through the urethra. -The scrotum is a loose sac of skin that hangs behind the penis containing the testes. The scrotum has protective function including the maintenance of optimal temperatures for the sperm survival and function. For sperm development the testes must maintain a temperature, slightly cooler than body temperature. Special muscles in the wall of the scrotum contract and relax in order to move the testes near the body. -The epidydimus is located at the back of the testes and connects the testes to the vas deferens. Its function is to store and carry sperm. -The testes is the location for testosterone production. The collection of tubes within the testes are the seminiferous tubules. Within these tubules, spermatogenesis takes place. It transports and stores sperm cells that are produced in the testes and also brings the sperm to maturity since the sperm that emerges from the testes are immature and incapable of fertilization.

Function of the endocrine system

to regulate organs within the body to meet the growth and the productive needs of the organism. And also, to maintain homeostasis.

True or False: Most signaling molecules are found in low concentrations inside the cytoplasm

true

the hypothalamus

the connector between the endocrine and the nervous system -Receive inputs from CNS and projects to brainstem ad spinal cord -Role in integration of parasympathetic and sympathetic nervous system activity: heart rate, vascular function, blood pressure... -Produces releasing and inhibiting hormones (RH, IH) -Detects humoral secretion from target tissues and adjust hormone production to maintain an optimal internal environment -has been implicated in the regulation of biological rhythms or the regulation of fat metabolism and food intake by its response to a protein called leptin, leptin hormone that regulates satiety. synthesizes two hormones: Vasopressin (ADH) and oxytocin from neurosecretory cells

the major glands of the endocrine system

the endocrine tissues of the pancreas the parathyroid glands at the level of the neck the thyroid gland pituitary gland in association with the hypothalamus, the pineal gland the adrenal glands on the top of the kidneys, gonads, which are the testis and ovaries, placenta white adipose tissue that produces adipokynes that participate in glucose and lipid metabolism

Ovarian Follicle structure

the follicle cells surrounding the oocyte have the basal lamina, some nursing cells (this is in the invertebrate follicle), and vertebrate follicle with follicle cells, zona pellucida, oocyte and the theca. also the granulosa cell, the antrum, the zona pellucida, similar here, the secondary oocyte and the theca.

oogenesis and folliculogenesis

the growth process in which the preliminary egg cell (or ovum) becomes a mature ovum. The eggs development starts before the female birth. In humans, eight to twenty weeks after the fetus has started to grow, cells that are to become mature ova, have been multiplying, and by the time that the female is born, all of the egg cells that the ovaries will release during the active reproductive years of the female are already present in the ovaries. These cells, known as the primary ova, number around 400 thousand. The primary ova remain dormant until just prior to ovulation, when an egg is released from the ovary. Some primary egg cells may not mature for 40 years and others degenerate and never mature. Mechanism: 1-Primordial germ cells migrate into the developing gonad early in embryogenesis (oogonia). 2-Oogonia proliferates into primary oocyte 3-Primary oocyte begins first meiosis 4-First meiosis is stopped until sexual maturity 5-At sexual maturity, some oocytes complete meiosis I and become secondary oocytes under FSH stimulation. 6-Secondary oocyte is contained in the secondary follicle. 7-Secondary follicle keeps growing until ovulation 8-Secondary oocyte is ovulated from a mature follicle and enters into the fallopian tubes. folliculogenesis: which typically leads to ovulation of one follicle approximately every 28 day

Vitellogenesis

the production of yolk, which is a mixture of proteins and lipids produced outside the oocyte and retained later by the oocyte early in the formation of the ovum. Nutrients from the extracellular fluid passes from the blood to the oocyte (some through endocytosis like vitellogenin) and then, it is stored in vesicles. Vitellogenesis starts in response to environmental conditions or developmental programs, the pathway begins centrally in the brain initiating a hormonal cascade that causes the syntheses of vitellogin At the end of the vitellogenesis, the ovary is packed with yolky oocytes which subsequently undergo maturation and ovulation under favorable environmental conditions

endocrine regulation describes the process whereby....

the sensing cell in the gastrointestinal track (enteroendocrine cell, EEC), responds to a stimulus by secreting a regulatory peptide or hormone that travels via the bloodstream to target cells different from the point of secretion. Cells responding to gastrointestinal hormone express specific receptors for the hormone. Hormones released from the GI tract have effects on cells located in other regions of the GI tract and also on glandular structures associated with the GI tract, such as the pancreas. In addition, gastro-intestinal hormones have effects on other issues that have no direct role in digestion and absorption, including endocrine cells in liver and brain.

endocrinology

the study of hormones, and is a subdivision of the field of physiology. Endocrine signaling is characterized by the regulated secretion of a signaling molecule, which is a hormone, into the extracellular fluid. The endocrine signaling is also characterized by the diffusion of the hormone into the vasculature and its circulation through the body And is also characterized by the diffusion of the hormone out of the vasculature into the extracellular space, and binding to a specific receptor.

Types of receptors: Intracellular (nuclear) receptors

• Small hydrophobic hormones bind to intracellular (nuclear) receptors - e.g., thyroid hormone and steroid hormones. • Regulate the transcription of target genes -slow effects. Mechanism: the hydrophobic ligands pass through the cell membrane, and the activated intracellular receptor acts as a transcription of target genes by binding to a specific DNA sequences and increasing or decreasing mRNA production from the target gene. Binds hydrophobic ligands like steroid or thyroid hormones Structure: A ligand-bind domain, a DNA binding domain, and trans activation domain.

Prolactin (PRL)

• Stimulates milk synthesis (positive feedback loop) • Role in promoting maternal behavior through effects on brain. • Prolactin found in all vertebrates • mammary gland is major target -also has many other functions, including reproduction and lactation, water and salt balance, growth and morphogenesis, metabolism, behavior, immune regulation and even effects on the skin