Endocrine and Chemical Messengers PDF

Communication 1 : ENDOCRINE AND CHEMICAL MESSENGERS Nea Esparcia Jon Carlo Mancao Lara Vallescas  What is Endocrine? It refers to the tissue that makes and releases hormones that travel in the bloodstream and control the action of other cells or organs. STR...

Communication 1 : ENDOCRINE AND CHEMICAL MESSENGERS Nea Esparcia Jon Carlo Mancao Lara Vallescas  What is Endocrine? It refers to the tissue that makes and releases hormones that travel in the bloodstream and control the action of other cells or organs. STRUCTURES FUNCTIONS Pineal gland help control the circadian cycle of sleep and wakefulness by secreting melatonin secretes hormones that stimulate or suppress the release of hormones in the pituitary gland, in addition to Hypothalamus controlling water balance, sleep, temperature, appetite, and blood pressure Pituitary monitors and regulates many bodily functions through the hormones that it produces. Parathyroid gland produce parathyroid hormone, which plays a key role in the regulation of calcium levels in the blood. Thyroid Regulates of the basal metabolic rate by a production of thyroid hormones that is called as the Calcitonin Produces white blood cells known as T cells, which aid in immunity. It also contributes to the production of Thymus hormones such as insulin STRUCTURES FUNCTIONS produce hormones that help regulate your metabolism, immune system, blood pressure, response to stress and other Adrenal gland essential functions. Pancreas secretes the hormones insulin and glucagon to control blood sugar levels throughout the day Produces hormones that regulate blood pressure, red blood cell production, calcium absorption, and platelet Kidneys production. Testes responsible for making sperm and are also involved in producing a hormone called testosterone Produces and secrete estrogen, progesterone, and small amounts of testosterone that regulate the menstrual cycle Ovaries and promote the development of secondary sexual characteristics. What are Chemical messengers? Chemical messengers refers to the special chemicals that is secreted by humans and animals ductless or endocrine glands that is also called as the hormones. Function of the chemical messengers Chemical messengers act as signals within the body, regulating a wide range of functions by stimulating or inhibiting specific processes. Diversity of chemical messengers Chemical messengers can be categorized as follows: 1. Local chemical messengers 2. Neurotransmitters 3. Neuropeptides 4. Hormones 5. Pheromones Signal Tranduction Pathway Signal Transduction Pathway is a sequence of molecular events that transfer the signal from a receptor (typically found on the cell surface) to the interior of the cell, resulting in a change in gene expression, behavior, or function. These biological steps are how cells transform an external signal (like a hormone or neurotransmitter) into a particular response.  Key Steps in Signal Transduction pathway 1. Signal Reception The process starts when a ligand, also known as an external signaling molecule, attaches itself to a particular receptor either within or on the outside of the cell. This receptor is typically a protein designed to recognize and respond to that particular signal, ensuring only target cells with the correct receptor can respond to the signal. Receptors can be located on the cell membrane or inside the cell. 2. Signal Transduction The receptor triggers a conformational (shape) change as a result of the ligand's binding. The intracellular signal transduction pathway becomes active by this alteration, which also activates the receptor. The signal is then relayed through a series of proteins and secondary messengers inside the cell, this relay involves Protein kinases, G-proteins and Secondary Messengers 3. Signal Amplification One signaling molecule can cause a significant reaction because the signal is frequently amplified as it passes through the pathway. One active receptor, for instance, can set off several cAMP molecules, each of which can activate a number of downstream proteins. 4. Cellular Response The final step in the pathway leads to a specific cellular response. This can involve various cellular activities, like Gene expression, Metabolic changes, Cytoskeletal changes and Ion channel opening. 5. Signal Termination To avoid overstimulation and give the cell time to reset, the signal must be cut off once the response has begun. This termination can occur through receptor internalization, degradation of the signaling molecule, or deactivation of proteins and secondary messengers.  Types of Signal Transduction Pathways Receptor Tyrosine Kinase (RTK) Pathway it involve receptors that add phosphate groups to tyrosine residues in proteins, triggering downstream signaling. Insulin signaling is an example of an RTK pathway. G-Protein-Coupled Receptor (GPCR) Pathways: involved in a wide range of signaling processes. Upon ligand binding, they activate G-proteins, which then trigger various downstream pathways. An example is adrenaline signaling. Ion Channel Pathways In these pathways, ligand binding opens or closes ion channels, leading to changes in ion flow across the cell membrane. This is common in neurotransmitter signaling, such as in the nervous system. Intracellular Receptor Pathways For molecules that can cross the cell membrane (like steroid hormones), the receptors are often located in the cytoplasm or nucleus. These pathways typically result in direct changes in gene expression.  Regulation of Physiological Processes by Hormones  Hormones Hormones are the chemical messengers that play a vital role in regulating numerous bodily functions, including growth, metabolism, reproduction, and mood. These intricate substances are secreted by various glands and travel through the bloodstream, influencing cells and organs throughout the body,  Key Physiological Processes Regulated by Hormones 1. Growth and Development Growth Hormone (GH): Stimulates growth, cell production, and protein synthesis. Insulin-like Growth Factor 1 (IGF-1): Mediates many of GH’s effects, promoting tissue growth and development. Thyroid Hormones: Essential for normal growth and development, particularly brain development. Sex Hormones: Influences secondary sex characteristics, reproductive development, and behavior. 2. Metabolism Insulin: Lowers blood glucose levels by stimulating glucose uptake by cells. Glucagon: Raises blood glucose levels by stimulating glycogen breakdown and glucose production in the liver. Thyroid Hormones: Increase Metabolic rate, affecting energy expenditure and body temperature. Adrenal Hormones: Regulate metabolism, particularly during stress. 3. Homeostasis Antidiuretic Hormone (ADH): Regulates water balance by increasing water reabsorption in the kidneys. Aldosterone: Regulates electrolyte balance, particulary sodium and potassium. Calcitonin & Parathyroid Hormone (PTH): Regulate calcium and phosphorus levels in the blood. 4. Stress Response Cortisol: Released during stress, increases blood sugar levels, suppresses the immune system, and aids in tissue repair. Adrenaline (Epinephrine): Prepares the body for “fight or flight” by increasing heart rate, blood pressure, and blood glucose levels. 5. Reproduction Follicle-Stimulating Hormone (FSH): Stimulates the growth of ovarian follicles in female and sperm production in males Luteinizing Hormone (LH): Triggers ovulation in females and testosterone production in males Estrogen & Progesterone: REgulate the menstrual cycle and pregnancy Testosterone: Promotes male sexual development and function.  Hormonal Regulation Mechanisms Negative Feedback The most common mechanism, where a hormone’s effect inhibits its own secretion. Positive Feedback A less common mechanism, where a hormone’s effect stimulates its own secretion, leading to a rapid increase in hormone levels. Neutral Control The nervous system can directly stimulate hormone release, as seen in the stress response. Humoral Control Changes in the blood composition can trigger hormone release, such as the release of insulin in response to high blood pressure  Endocrine Systems of Amniotes Endocrine systems in avian and nonavian reptiles are very similar to those found in mammals. However, some unique hormonal functions exist: Prolactin Used by birds like pigeons, doves, and flamingos to stimulate the production of "crop milk," a nutrient- rich substance fed to chicks. It also regulates brooding and post-hatching parental behaviors. Arginine Vasotocin Used by chickens and sea turtles to activate oviduct contractions during egg laying. Thyroid Hormones Regulate feather development, molting, and migratory behavior in birds. In nonavian reptiles, they regulate metabolism, but their effectiveness is temperature-dependent. Testosterone Controls secondary sexual characteristics in male reptiles, such as plumage color and spurs, which influence sexual behavior. While testosterone is a common hormone in many animals, its role and dominance can vary. In nonavian reptiles like green anoles, testosterone levels influence the development of secondary sexual characteristics, such as head size, bite force, and dewlap size. Ultimobranchial Glands Are small, paired structure in the neck just bellow the parathyroid glands. They are present in both avian and nonavian anbiotes, and their function is similar to that of the the anamniotes Bursa of Fabricius A unique lymphoid organ found in avian reptiles, it's connected to the cloaca and produces a hormone called bursin. Bursin aids in the maturation of B-lymphocytes, which are essential for the immune system. The bursa of Fabricius is well-developed during embryonic development but begins to regress after hatching.  Endocrine Systems of Mammals Zoologists have a deeper understanding of the endocrine organs, hormones, and target tissues of mammals compared to other animal groups. Pituitary Gland Located directly below the hypothalamus, consists of the anterior (adenohypophysis) is lager and produces hormones and posterior lobes (neurohypophysis) stores and releases hormone produced by the hypothalamus, including antidiuretic hormone (ADH) and oxytocin. The adenohypophysis synthesizes and releases several hormones, including growth hormone (GH) and prolactin (PRL). Thyroid Gland The thyroid gland is located in the pharyngeal area and varies in shape among different vertebrates. It produces two hormones, T3 and T4, which are regulated by thyroid-stimulating hormone (TSH) from the pituitary gland.  T3 and T4 influence growth, development, and metabolic rates. The thyroid gland also produces calcitonin, a hormone that helps regulate calcium levels in the blood by promoting its deposition in bones. Parathyroid Gland are small glands embedded in the thyroid lobes. They produce parathyroid hormone (PTH), which helps regulate calcium levels in the blood by stimulating its release from bones and increasing its absorption in the intestines. Adrenal Gland Located on top of each kidney, the adrenal gland consists of two parts: the adrenal cortex and the adrenal medulla. The adrenal cortex secretes hormones like cortisol (regulates metabolism), aldosterone (maintains fluid balance), and some sex hormones. The adrenal medulla releases epinephrine and norepinephrine, which contribute to the "fight-or- flight" response by increasing heart rate, blood pressure, and blood sugar levels. Pancreas is a gland with both exocrine and endocrine functions. The exocrine part produces digestive enzymes. The endocrine part, called the islets of Langerhans, contains cells that secrete hormones like insulin and glucagon. Insulin lowers blood sugar levels by promoting glucose uptake by cells. Glucagon raises blood sugar levels by stimulating the breakdown of glycogen into glucose. Gonads Testes : Produce testosterone, which is essential for sperm production, development of male secondary sexual characteristics, and maintenance of male sexual behavior. Ovaries : Produce estrogen and progesterone, which regulate the menstrual cycle, prepare the uterus for pregnancy, and contribute to the development of female secondary sexual characteristics. Thymus Located near the heart, the thymus gland is larger in young individuals and shrinks with age. It plays a role in the development and maturation of T-cells, which are a type of white blood cell essential for the immune system. Pineal Gland A small, pea-shaped gland in the brain, located near thee center of the brain, between two hemispheres. It produces melatonin, a hormone that helps regulate sleep patterns.  Some Hormones Are Not Produced by Endocrine Glands Some organs and tissues that are not exclusively endocrine glands also secrete hormones: Heart The heart's right atrium secretes atrial natriuretic peptide (ANP), which helps regulate blood pressure by reducing salt and water reabsorption in the kidneys. Kidney The kidneys produce erythropoietin (EPO), which stimulates the production of red blood cells in the bone marrow. Other Tissues: Adipose tissue, the liver, the gastrointestinal tract, and the placenta also produce various hormones.  Evolution of Endocrine system Cell-to-Cell Signaling This is a fundamental process in all animals, involving both electrical and chemical communication. Nervous tissues and neuropeptides The development of these early in animal evolution facilitated more complex communication systems. Diversity of endocrine systems Different animal phyla exhibit diverse structures and functions of their endocrine systems, reflecting their unique evolutionary adaptations. Thank you!