Human Biology Course Unit 9 PDF

BACHELOR OF SCIENCE IN COMPUTER SCIENCE: HUMAN BIOLOGY COURSE MODULE COURSE UNIT WEEK 2 9 10 Endocrine System and Body Defense Mechanisms ✓ Read co...

BACHELOR OF SCIENCE IN COMPUTER SCIENCE: HUMAN BIOLOGY COURSE MODULE COURSE UNIT WEEK 2 9 10 Endocrine System and Body Defense Mechanisms ✓ Read course and unit objectives ✓ Read study guide prior to class attendance ✓ Read required learning resources; refer to unit terminologies for jargons ✓ Proactively participate in classroom discussions ✓ Participate in weekly discussion board (Canvas) ✓ Answer and submit course unit tasks At the end of this unit, the students are expected to: Cognitive: 1. Identify the major endocrine organs and the hormones that they secrete 2. Understand how hormones initiate both short-term and long-term body changes 3. Describe how the body reacts to the invasion of disease-causing organisms and substances 4. Explain how the body can acquire long-lasting resistance to microbes Affective: 1. Listen attentively during class discussions 2. Challenge ideas and opinions raised by the classmates and instructors with tact and respect.  3. Appreciate how the endocrine system controls bodily processes and the growth and development of an individual Psychomotor: 1. Participate actively during online and face-to-face discussions Goodenough, J. and McGuire, B. A. 2011. Human Biology. Majority of the modules are based on the book Biology of Humans (4th Edition): Concepts, Application, and Issues (pp. 173-191, 238- 257). San Francisco, CA: Pearson Endocrine System Function and Mechanisms of Hormones Endocrine glands release their hormones into the spaces just outside cells, instead of moving their secretions through ducts as observed in other glands. After being released into spaces between cells, the hormones then diffuse into the bloodstream. Endocrine glands and organs that have some endocrine tissue constitute the endocrine system. The endocrine system regulates and coordinates other organ systems and helps maintain homeostasis. Hormones serve as the chemical messengers of the endocrine system and these hormones contact virtually all cells within the body. However, hormones affect only target cells that have receptors for specific hormones. These receptors recognize and bind specific hormones. The hormones can be categorized based on their chemical constitution, and they can be recognized as steroid hormones or peptide hormones Steroid hormones. Image from here Steroid hormones are lipid-soluble, allowing them to cross through the plasma membrane of target cells. Once it enters the cell, these hormones combine with a receptor molecule inside the cell, forming a hormone–receptor complex. In the nucleus, the complex directs synthesis of specific proteins, including enzymes that stimulate or inhibit metabolic pathways. Water-soluble hormones. Image from here Meanwhile, due to their composition, water-soluble hormones, like those made up of peptides and proteins, cannot pass through the lipid bilayer of the plasma membrane. These hormones need to activate second messenger systems in order to perform its function. The hormone binds to a receptor on the plasma membrane. Once the hormone binds to a receptor, it will activate a molecule in the cytoplasm, considered the second messenger. The secondary messenger changes the activity of enzymes and chemical reactions. A common difference in function between the two types of hormones is the kind of process activated. Lipid-soluble hormones prompt the synthesis of proteins, while water-soluble hormones activate existing proteins. Endocrine glands are stimulated to manufacture and release hormones by chemical changes in the blood, hormones released by other endocrine glands, and messages from the nervous system. Hormone secretion is usually regulated by negative feedback mechanisms. However, there are occasions that hormone secretion is made possible by positive feedback mechanisms. Hormones also interact with each other, and the action may either be antagonistic, synergistic, or permissive. Glands of the Endocrine System Different Endocrine Glands in the human body. Image from here Hypothalamus and the Pituitary Gland Both the hypothalamus and the pituitary gland are found in the, or near the, brain. The pituitary gland is divided into two parts, namely an anterior lobe and a posterior lobe. The function of the anterior lobe is influenced by the hypothalamus through a circulatory connection (connection of blood vessels). Neurosecretory cells (nerve cells that release chemical messengers) found in the hypothalamus release hormones that travel by way of the bloodstream to the anterior lobe. These hormones stimulate or inhibit release of hormones produced by the anterior lobe. The anterior pituitary releases six hormones o growth hormone, GH; o prolactin, PRL; o thyroid-stimulating hormone, TSH; o adrenocorticotropic hormone, o ACTH; follicle-stimulating hormone, FSH; and o luteinizing hormone, LH. Four (TSH, ACTH, FSH, LH) of the six hormones are tropic hormones, meaning they influence other endocrine glands. In contrast, the connection between the hypothalamus and the posterior lobe is neural, or by direct connection of nerve cells. Neurosecretory cells in the hypothalamus make oxytocin (OT) and antidiuretic hormone (ADH). These two hormones travel down the axons of the cells to axon terminals found in the posterior lobe. These hormones are then stored in the posterior lobe and released when needed. Thyroid Glands Thyroid gland produces two hormones, namely the thyroid hormone and the calcitonin. The thyroid hormone is responsible for regulating metabolic rate, heat production, and blood pressure, and there are two types of thyroid hormones, which are Thyroxine (T 4) and Triiodothyronine (T3). Meanwhile, Calcitonin maintains low levels of calcium in the bloodstream Parathyroid Glands The parathyroid glands are located at back of the thyroid gland and appears as four small masses of tissues. The parathyroid gland secretes parathyroid hormone (PTH), which has an opposite function to calcitonin. The action of PTH raises blood levels of calcium through the movement of calcium from bone and urine to the blood. Adrenal Glands Each of two adrenal glands are found on top of a kidney and has two regions, identified as adrenal cortex and adrenal medulla. The adrenal cortex (outer region) releases gonadocorticoids, mineralocorticoids, and glucocorticoids. The adrenal medulla (inner region) produces epinephrine (adrenaline) and norepinephrine (noradrenaline). These two hormones are responsible for initiating the fight-or-flight response. Pancreas The pancreas secretes the hormones that help control the sugar levels in the blood. Glucagon increases glucose in the blood while insulin decreases glucose in the blood. The inability to control the blood sugar levels could result in diabetes mellitus. Diabetes mellitus is a group of disorders characterized by problems with insulin production or function. Thymus Gland The thymus gland lies on top of the heart and plays an important role in immunity since its hormones play an important role in the maturation of white blood cells called T lymphocytes. Pineal Gland The pineal gland is located at the center of the brain. This hormone secretes the hormone melatonin, which appears to be responsible for establishing biological rhythms and triggering sleep. Locally Acting Chemical Messengers Some local chemical messengers transfer information between adjacent cells. These kinds of receptors elicit rapid responses in target cells. Examples of local signaling molecules include neurotransmitters, prostaglandins, growth factors, and nitric oxide. Body Defense Mechanisms The Body's Defense System The body’s defense system attempts to attack substances or structures identified to be not part of the body, which may include disease-causing organisms called pathogens as well as cancerous cells. Three Lines of Defense The body has three lines of defense. These lines of defense activate at different periods and each of these defenses perform different functions Image from: Li, Xia & Xiupeng, Wang & Ito, Atsuo. (2018). Tailoring inorganic nanoadjuvants towards next-generation vaccines. Chemical Society Reviews. 47. 10.1039/C8CS00028J. The first line of defense includes both nonspecific physical barriers and chemical barriers. Nonspecific physical barriers include the skin and mucous membranes while chemical barriers include sweat, oil, tears, and saliva. Both physical and chemical barriers which prevent entry of pathogens. The second line of innate defense includes defensive cells and proteins, inflammation, and fever. Phagocytes, eosinophils, and natural killer cells are defensive cells of the second line of defense. Meanwhile, antiviral interferons and complement are proteins that cause cells to burst. The inflammatory response is another part of the second line of defense and it occurs as a result of tissue injury or invasion by foreign microbes. Mast cells in the injured area release histamine. The histamine increases blood flow by dilating blood vessels to the region. Dilating blood vessels increases the permeability of capillaries in the region. Increased blood flow results in the redness and warmth in the region, while the release of fluids from the capillaries causes swelling. Fever is described as an abnormally high body temperature. Fever helps the body fight invading microbes by increasing several body defense mechanisms. The increase in temperature also slows down the growth of many pathogens. The third line of defense, the adaptive immune response, targets specific pathogens, and this line of defense takes advantage of memory of the immune system. Distinguishing Self from Nonself Self markers are present in all body cells. Self markers are proteins that are also called as the major histocompatibility complex (MHC) proteins. Without these markers, cells are considered nonself and are attacked by the immune system. An antigen is a substance that triggers the immune system and are found in nonself cells. Lymphocytes are white blood cells that are responsible for immune responses, and two types of cells (B lymphocytes and T lymphocytes) develop in the bone marrow. However, both cells mature in different places. The B cells stay and mature in the bone marrow, while the T cells migrate and mature in the thymus gland. B cells and T cells have receptors on their respective cell surfaces. These receptors allow each of those cells to recognize an antigen that features a different shape. When an antigen is detected, B cells and T cells with receptors that detect the antigen, causing these cells to replicate repeatedly. These cells form effector cells that destroy the antigen. Once the antigen is destroyed, the cells then form memory cells that remain in the body over years or even decades. These memory cells supply a rapid response on following exposure to the antigen. Antibody-Mediated Responses and Cell-Mediated Responses The antibody-mediated immune response and the cell-mediated immune response can occur simultaneously with the aim to defend the body against the same antigen. Steps of Adaptive Immune Response Image from here Macrophages engulf foreign material or organism they encounter through the process of phagocytosis. After engulfing the material, a part of the destroyed substance will be placed on the surface of the macrophage to serve as an antigen. This will alert lymphocytes to the presence of an invader while at the same time revealing the identity of the foreign body looks like. To prevent other immune cells from attacking the macrophages, these cells also have their own molecular (MHC) markers on their membranes, allowing them to be identified as belonging in the body. The macrophage then presents the antigen to a helper T cell. The latter cell serves as the main switch to the entire immune response after the macrophage secretes a chemical that activates the helper T cell. Once it is activated, the helper T cell releases a chemical that activates the appropriate B cells and T cells, although only the cells for the antigen will be activated. B cells are responsible for antibody-mediated immune responses. Antibodies produced by the B- cells allow the body to respond to antigens that are free in body fluids. These antigens including bacteria, free virus particles, and toxins. Once activated by the helper T cell, a B cell replicates repeatedly, and the B cells results to the formation of two lines of descendant cells. which effector cells that transform into plasma cells and memory B cells. Plasma cells secrete Y-shaped proteins called antibodies into the bloodstream, and these proteins bind to the particular antigen. Once the antigen is bound, the immune system may inactivate it or may remove it from the body. Cytotoxic T cells handle cell-mediated immune responses. These cells are more effective against cellular threats. These cellular threats include infected body cells and cancer cells. Like B cells, T cells form two lines of descendant cells upon activation, and these include effector cells, called cytotoxic T cells, and memory T cells. Cytotoxic T cells secrete perforins, which causes cells to burst and die by placing holes on the cell membrane. After the first encounter with a particular antigen, the primary response is initiated, which may take several weeks to become effective against the antigen. Meanwhile, memory T cells allows for a quicker response in the presence of the same antigen. This response is called a secondary response. Last but not the least, the suppressor T cells dampen the activity of B cells and T cells when the levels of the antigens present in the body decreases. Active and Passive Immunity In active immunity, the body forms memory cells that defend the body against a particular antigen. There are two ways to develop active immunity, and these include the introduction of an antigen that infects the body. Another way to develop active immunity is through vaccination, a procedure that introduces a harmless form of an antigen into the body. Meanwhile, a passive immunity results when a person receives antibodies that were produced by another person or animal. Unlike active immunity, passive immunity only appears and works for a short period of time. Monoclonal Antibodies Monoclonal antibodies are identical antibodies that bind to a specific antigen. Monoclonal antibodies are used in research and in the diagnosis and treatment of diseases. Problems of the Immune System Autoimmune disorders occur when the immune system attacks the body’s own cells. An allergy is a strong immune response against an antigen, which in this case is called an allergen. Allergy occurs when the allergen binds to IgE antibodies on the surface of mast cells or basophils. Once allergens are recognized by the mast cells or basophils, histamines are released. Histamine causes redness, swelling, itching, and other symptoms that are commonly observed in an allergic response. Negative Feedback Mechanism – a mechanism that aims to reduce fluctuations in the output of the system Positive Feedback Mechanism – a mechanism that aims to increase fluctuations in the output of the system First Messenger – an extracellular substance that binds to a receptor at the cell surface. Examples of first messenger include hormones and neurotransmitters. Second Messenger – molecules within the cells that relay the signal from receptors located at the cell surface Pathogen – bacteria, virus, or fungi that could cause disease Active Immunity – process of exposing the body to an antigen to generate a long-lasting immune response. Passive Immunity – provided when a person is given antibodies to combat pathogens present in the body National Institutes of Health (United States). (n.d.). Endocrine Diseases. https://www.niddk.nih.gov/health-information/endocrine-diseases Study Questions Between the nervous system and the endocrine system, which of the two is responsible for the growth spurt that occurs at puberty? Which of the two is responsible for the rapid withdrawal of the hand once exposed to high temperature? Why? Explain how an HIV infection can cause death in individuals even if the virus itself is not direct cause of death of the person infected with the pathogen. Goodenough, J. and McGuire, B. A. 2011. Human Biology. Majority of the modules are based on the book Biology of Humans (4th Edition): Concepts, Application, and Issues (pp. 173-191, 238-257). San Francisco, CA: Pearson Kerr, S and Georgia Institute of Technology. (23 November 2016). Biology 1520: Animal Sensory Systems. http://bio1520.biology.gatech.edu/chemical-and-electrical- signals/sensory-systems-i/