MCAT Biology 10-11 Immune System & Homeostasis

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Terms in this set (34)
Components
1. Lymph nodes = filter lymph and help attack bacteria & viruses
2. Bone Marrow = immune cell production
3. Thymus = secretes thymosin, a hormone that stimulates pre-T cells to mature
4. Spleen = storage area for blood, filters blood and lymph, site of B-cell maturation
Innate Immune System
quick response near entry points of body. consists of antimicrobial molecules & phagocytes that activate an inflammatory response, secreting proteins called cytokines that trigger an influx of defensive cells in the blood.

1. macrophages - engulfs invaders
2. mast cells - release histamine for inflammation
3. granulocytes - inflammatory response
4. dendrite cells - present antigens to adaptive cells
5. natural killer cells - destroy own infected cells
Adaptive Immune System
B-cells - secrete antibodies that bind to antigens on invader in order to directly attack it or mark it for destruction. Humoral immunity.
T-cells - recognize antigens displayed on invaders to directly attacks or activate B-cells. Cell-mediated immunity.

Both produce "memory" cells
Hypersensitivity reactions
1. Autoimmunity - attack of self antigens.
Ex:: Diabetes (type 1) where pancreatic B-cells are attacked resulting in insulin deficiency
2. Allergies - attacks of a foreign antigen that is not dangerous
Histamine
a protein that causes vasodilation to allow macrophages to move out of the bloodstream and into the tissue quickly.
Interferon
a protein that non-specifically prevents viral replication and dispersion
Humoral Immunity
involves the production of antibodies (long response) that are specific to invading microbe and produced by B-cells.

B-cells are not constantly active and wait in the lymph notes until their corresponding antigen comes along.

Plasma cells go attack during the primary response and memory stay in the lymph nodes to be prepared for a secondary response (if necessary).
Antibodies
Y-shaped molecules that are made up of 2 identical heavy chains and 2 identical light chains connect by disulfide linkages and non covalent interactions.
Antigen-binding region located at Y tips.
Helper T-Cells
Helper T-cells (T4 cells) express CD4 cell-surface protein and secrete chemicals called lymphokines to coordinate immune response. Responsible for recruiting other immune cells and increasing their activity. These cells are destroyed by HIV and prevent a adequate immune response.
Cytotoxic T-cells
Cytotoxic T-cells (T8 cells) express CD8 cell-surface protein and directly kill virally infected cells by secreting toxic chemicals. Immunosuppressants necessary to suppress these cells during organ transplantations.
Suppressor T-cellsSuppressor T-cells (T8 cells) help to tone down the immune response once the infection has be adequately contained.Immunodeficient Disorders1. HIV - lack of help T-cells (T4 cells) so cannot form CD4 protein to initiate immune response. 2. Bruton's agammaglobulinemia - absence of B-cells in male infants (X-linked) leading to recurrent bacterial infections (no viral or fungal disorder which are handled by T-cells) 3. DiGeorge's syndrome - underdevelopment or absence of the thymus gland so lack of T-cells and impaired defenses against bacterial/fungal infectionsActive ImmunityVaccinations are an example by injecting a weakened or killed form of the microbe, or just a part of the microbe's structurePassive ImmunityTransfer of antibodies to the individual not the B-cells that produce them. Ex. administration of RhoGAM to an Rh- woman to prevent sensitization to her Rh+ fetus blood.Lactealslymphatic vessels tha colles fats from the small intensive vili in the form of chylomicrons to deliver into the bloodstream and bypassing the liver.Kidney StructureCortex - the outermost layer Medulla - beneath the cortz Renal Pelvis - the deepest layer and location of entry/exit for the renal artery, renal vein, and ureter.Nephron StructureThe nephron is the functional unit of the kidney Afferent arterioles - blood enters here from the renal artery. located in the medulla of the kidney. Glomeruli - 1st set of capillaries formed from afferent arterioles Vasa Recta - 2nd set of capillaries formed from afferent arterioles Efferent arterioles - blood enters here from glomeruli and then leads blood back. Bowman's capsule - a cuplike structure that surrounds the net of capillaries. the capsule leads to a long ruble with many distinct areas 1. proximal convoluted tubule 2. descending and ascending limbs go the loop of Henle 3. distal convoluted tubule 4. collecting ductFiltrationNephron's 1st step in osmoregulation. 20% of blood that passes throughout he glomerulus is filtered into Bowman's space - collected fluid is called the filtrate. The filtrate does not contain cells or proteins due to their large size. Filtrate is isotonic to blood so neither the capillaries nor the capsule swell.SecretionNephron's 2nd step in osmoregulation. Nephrons can serete salts, acids, bases, and urea directly into the tubule by both active and passive transport. Ability to remove excess ions or substances in the blood and excrete wastes too large to pass through pores.ReabsorptionNephron's 3rd step in osmoregulation. Glucose, amino acids, and other substances that may be filtered and/or secreted may be reabsorbed back into the body for use.Selective PermeabilityProximal and distal tubules are capable of reabsorption of most substances in the filtrate (such as water), while the ascending (salt not water) and descending (water not salt) limbs of the loop of Henle and the collecting duct (always water) are more selective. Depends on relative hydration of the individual. On hot days, reabsorption is greater and urine is more concentratedOsmolarity Gradientthe osmolarity in the interstitium (tissue surrounding the tubule) can range from isotonic with blood (during H2O excretion) to 4 times as concentrated (under H2O reserve)Flow of Filtrateisotonic until it reaches the descending arm of the loop of Henle, which is only permeable to water. This hypertonic region drives water out of the tubule, which increases the filtrates osmolarity. The ascending limb is permeable only to salts, which will be actively pumped out due to the low concentration outside the tubule. Filtrate is isotonic to the interstitium. Final urine concentrations depend on permeability of the collecting duct.AldosteroneA steroid hormone release by the adrenal cortex in response to decreased blood volume (aka less fluid in the pipes) so low blood pressure (hypotension). Released in response to an increase in angiotensin, which itself id positively regulated by renin. Mechanism: alters the ability of the collecting duct to reabsorb sodium, allowing water to flow with it. also increase excretion of potassium Drugs that inhibit aldosterone receptors are used to treat people with high blood pressure.Antidiuretic Hormone (ADH)aka Vasopressin that is made in the hypothalamus, stored in the posterior pituitary gland, and secreted when blood osmolarity is high. A peptide hormone that directly alters the permeability of the collecting duct but allowing more water to be reabsorbed. Mechanism: ADH does this by making cell junctions of the duct more leaky (permeable) to water so water will re-enter the interstitum. Inhibited by alcohol and caffeine, leading to more frequent excretion of dilute urine.ExcretionAnything that doesn't leave the tubule will be excreted. Filtrate leaves tubule and collects in the renal pelvis, which then flows through the ureter to the bladder, where it is stored until voiding through the urethra. Filtrate mostly composed of urea, uric acid, and excess ions and should never contain blood, protein, or glucose.Liver root word and function"Hepato" refers to the liver and its processes. Think Hepatitis - aka infection of liver due to a bacterial or viral infection. Function: to produce bile, which aids in the absorption of fats by solublizing them. Also glucose regulation and nitrogen waste through urea. Hepatic portal vein brings nutrients absorbed during digestion to the liver.Liver HomeostasisRegulates the storage or break down of glucose depending on amount in blood (did individual eat?). Can also make new glucose by gluconeogenesis from various presursors. When proteins are broken down, the liver prevents ammonia buildup by combining it with carbon dioxide to create urea, which can be excreted by the kidneys. It helps remove nitrogenous waste. Other functions: detoxification, storage of vitamins/cofactors (iron & B12), destruction of old erythrocytes, synthesis of bile, synthesis of various blood proteins, defense against antigens, beta-oxidaation of FA to ketones, interconversion of carbs, fats, and amino acids.Large Intestine HomeostasisCapable of reabsorbing salt and water (not directionally) and can excrete certain salts (Ca & iron).Skin Anatomy16% of total body weight Derived from the ectodermal germ layer. Contains 3 layers starting from the top: epidermis, dermis, hypodermis (subcutaneous layer) The epidermis (top layer) has 5 layers called strata: (1) stratum corneum, (2) stratum lucidum, (3) stratum granulosum, (4) status spinosum, (5) stratum basalis The dermis (middle layer) has layers as well: (1) papillary layer - loose connective tissue (2) reticular layer - denser The hypodermis (last layer) - a layer of connective tissue that connects our skin to our bodies.Melanocytesepidermal cells that secrete the pigment melanin, which helps keep us safe from UV light and consequent DNA damage.ThermoregulationRegulated by vasodilation, vasoconstriction, and sweating.Endotherms vs EctothermsEndotherms: animals that maintain a constant temperature. Ectotherms: animals whose temperature depends on the external environmentAestivation vs HibernationAestivation: desert animals Hibernation: non-desert animals Both recesses result in metabolic rate, heart rate, and respiration far below normal allowing for minimal expenditure of energy in inhospitable environments.