Human Physiology and Pathology

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  • Created on: 15-04-13 19:22
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  • Human Physiology and Pathology
    • Respiration
      • gas exchange needs a large surface area
      • supplies O2 to the cells and collects CO2 from the cells
      • lungs also have a role in the acid base balance and speech and breath control
      • respiratory system also works with the circulatory system
      • respiratory system made up of nasal passage, oral cavity, pharynx, larynx, trachea and lungs
        • larynx contains the vocal chords and the epiglottis which closes when eating
        • respiratory tract has the conducting zone and respiratory zone
          • respiratory zone is from the terminal bronchioles in the conducting zone and ends at the alveoli
          • conducting zone is from  the larynx to the trachea, is considered dead space as its not involved in gas exchange.
            • does humidify the air and trap bacteria and dust
      • diaphragm contracts for inspiration and relaxes for exhilation
      • nasal turbinates are bones in the nasal cavity that circulate and humidify air.
      • mucociliary escalator is the system by which the respiratory tract is lined with ciliated cells and mucus lines it
        • cilia move the mucus up and out of the lungs, taking dust particles with them
      • gas exchange occurs in the alvelor sacs which are 250micro m in diameter
        • gas exchange needs a large surface area
        • alveoli make up 50-100m2 surface area.
          • alveoli contain epithelial cells-type 1 and 2.
            • type 2 secretes pulmonary surfactant
          • have alveolar pores to allow air to circulate
      • alveolar ventilation is the measure of fresh air volume reaching the alveoli each minute
        • uses the equation Va = (Vt X RR) - (DSV - RR)
      • transpulmonary pressure is the force acting on the lungs to expand, uses equation Palv-Pip
      • flow = pressure difference / R
        • a low R gives a high flow
      • lung compliance is the stretchiness of the lungs and determines the compliance, elasticity and surface tension forces
        • use the equation compliance = change in lung volume/ transpulmonary pressure
      • lungs have 2 circulations, the pulmonary and the bronchiole circulation
      • controlled by chemoreceptors, there are central and peripheral chemoreceptors
        • central chemoreceptors are found in the brain stem
          • only increase firing with an increase in CO2 levels in the blood
          • not sensitive to oxygen pressures
        • peripheral chemoreceptors are found near the arteries
          • increases firing rate with a decrease in oxygen levels and an increase in acids and arterial CO2 levels
          • stimulates medullary inspiratory neurons and firing to motor neurons in the diaphragm and external intercostals
          • in direct contact with the blood and use chemical messengers to communicate
      • respiratory failure when PO2 is lower than 60mmHg at sea level and accompanied with raised/lowered PCO2.
        • caused by drugs, head injury or stroke
      • obstructive diseases when there is increased resistance to airflow which can be caused by excessive mucus
        • e.g. COPD
      • restrictive diseases are when the expansion of the lungs is restricted
        • e.g. pulmonary fibrosis
        • lung function tests anre used to diagnose
          • obstructive diseases when there is increased resistance to airflow which can be caused by excessive mucus
            • e.g. COPD
      • airway resistance can be increased by spastic contractions of smooth muscles, increased mucus production, inflammation of bronchiole walls
    • Cardiovascular system
      • 6 CV circulation systmems, cerebral, pulmonary, cardiac, hepatic, renal, systemic
      • The metabolic functions are delivery of nutrients, removal of metabolites, circulation of hormones, temperature regulation
      • arterial circulation takes high oxygenated blood from the heart
      • CO=HR x SV
      • venous circulation takes low oxygenated to the heart
      • cardiac output is the amount of blood pumped by each side of the heart in one minute
      • stroke volume is the amount of blood pumped by each ventricle in one contraction
      • heart is surrounded by pericardium sac, protecting it and is joined to diaphragm
      • cardiac muscle is highly striated with bands of actin and myosin in cross bridge formation
        • 2 major types of cardiac cells, autorhythmic and contractile
          • autorhythmic cells initiate action potential in rhythm cycles
      • blood in venous system has low flow, movement of skeletal muscle that aids movement of the blood
      • capillary bed has 3 types of vessels, terminal, arteriole, postcapillary venule and true capillaries
        • terminal arteriole has precapillary sphincters controlling blood supply to the capillaries
        • postcapillary venule connects directly to arterioles via the vascular shunt
      • pulse is the pressure wave of blood
        • taken as atmospheric pressure as the reference
          • maximum arterial blood flow is 120mmHg and the minimum is 80mmHg
      • mean arterial pressure is the average arterial pressure over the cardiac cycle
        • use CO=(MAP-CVP)/TPR or MAP = CO x TPR
      • heart wall has three layers, epicardium, myocardium and epithelium
      • ventricular muscle is much tcker than atrial muscle and left side has a thicker muscle than the right side
      • two types of valves in the heart, atriventricular valves and semi lunar valves
        • atrium and ventricules separated by atrioventricular valves, left side has two flaps of connective tissue, right side has three flaps of connective tissue
      • ECG is a diagnositc tool
      • Myocyte permeable to potassium not sodium
      • P Wave is the atrial depolarisation
      • QRS complex is the ventricular depolarisation
      • ST segement is the plateau of ventricular action potential
      • T wave is the ventricular repolarisation
      • pacemaker cells can fire action potentials in absence of external stimulus
      • increase heart rate by stimulation of sympathetic nerves, increase rate of rise of pacemaker potential
        • circulating catecholamines increase rate of rise of pacemaker potential
      • decrease heart rate by stimulation of parasympathetic nerve to the heart, decrease in rate of rise of pacemaker potential
      • barorreceptors monitor stretch and feedback information to the cardiovascular centers in the medulla
      • extrinsic control is any regulation of the heart by neural input, circulating hormones or any other factor originating from outside the organ
      • INtrinsic control is when the function is regulated by factors originating from within the organ or tissue itself
      • adrenaline, insulin and glucagon also affect heart rate
      • ventricular contractility is the measure oof ventricles capacity for generating force
      • 2 types of capillary, closed/continuous and fenestrated
        • closed/continuous is present in less active tissue, have basal membrane and capillary membrane fused tight together
        • fenestrated are present in active tissues to allow rapid exchange of materials
      • lymphatic system mops up excess fluid in interstitial fluid
        • lymph supports immune system by carrying the immune bodies
      • factors affecting fluid exchange across capillary walls include capillary hydrostatic pressure, interstitial hydrostatic pressure, plasma colloidal osmotic pressure, interstitial colloidal osmotic pressure
        • capillary hyrdostatic pressure forces fluid out of the capillary
        • interstitial hydrostatic pressure forces fluid into the capillary
        • Untitled
        • plasma collodoidal osmotic pressure draws fluid into the capillary
        • interstitial colloidal osmotic pressure draws fluid out of the capillary
      • adrenaline is a vasoconstrictor in most vascular beds but is a vasodilator in skeletal muscles
      • arrythmias are abnormalities of the cardiac rhythm
        • can cause sudden death, syncope, heart failure, chest pain, dizziness, palpitations
        • two main types of arrythmia bradycardia and tachycardia
    • Blood
      • leukocytes are involved in immune response, have nuclei
        • 5 types-lymphocytes, neutrophils, monocytes, eosinophils and basophils
          • lymphocytes make up 20-40% of all leukocytes, three main types-T B and null
          • basophils are non phagocytic cells. release histamine, heparin and other chemicals associated with allergic reactions
          • monocytes are 2-8% of all the leukocytes, used in phagocytic defense
          • eosinophils are 1-4% of all leukocytes, attack invaders that are too large to ingest, release toxic molecules which can damage normal tissues at the same time
          • neutrophils are 50-80% of all leukocytes, are phagocytes
      • thrombocytes are fragments of cytoplasm and have nucleus, are involved in blood clotting
      • blood cells formed in bone marrow
      • red blood cells are the most abundant, transports gases, no nucleus
        • are biconcave, have flexible plasma membrane
        • replicated every 120 days
        • filtered and destoyred in the spleen
      • made up of 55% plasma and 45% red and white blood cells
      • haematopoiesis is blood cell production
      • active bone marrow is red and found in pelvis, spine, ribs, cranium and ends of large bones
      • cytokines include colony stimulating factors, interleukins, stem cell factors, thrombopoietin and EPO
      • three categories for plasma proteins-albumins, globulins and fibrinogen
        • globulins are proteins that transport lipids, steroid hormones and are important in blood clotting
        • albumins made in liver,
        • fibrinogen is made in the liver
      • haemostasis is the process of blood clotting
        • 3 main steps, vasoconstriction, formation of platelet plug and blood coagulation
      • platelets are activated by contents in intracellular granules
      • INflammation is the response to injury or infection
        • mediators of inflammation are prostaglandins, leukotrienes, histamine, platelet activating factor, ATP, serotonin, bradykinin, substance P and CGRP
      • Immunity is classified into humoral snd cell mediated immunity
        • Humoral immunity is the production of antibodies to tag bacteria and other forgein matter for removal from the body
        • cell mediated immunity is the destruction of infected or abnormal cells
      • immune system is a collection of cells, tissues and molecules that mediate resistance to infections
        • consists of lymphatic tissues and leukocytes
      • lymphoid tissue made of bone marrow, thymus, spleen, lymph nodes and tonsils
        • central and peripheral lymphoid tissue
          • peripheral is the spleen, lymph nodes, tonsils, adenoids, appendix and peyers patches
          • central is the bone marrow and thymus
      • B cells have antibodies marking invaders for destruction. can secrete antibodies
      • T cells directly damage forgein cells when in contact. Includes helper T cells, cytotoxic T cells and suppressor T cells
      • Null cells/natural killer cellsare important against viral infections. Fast acting
        • recognize abnormal/infected cells, cause lysis by secreting perforins
      • Mast cells reside in mucosal and connective tissues/skin, releasing histamine and other inflammatory mediators
      • Lymph nodes filter the blood and lymph.
        • antigen presenting cells capture and present antigens here, activating B and T cells
      • dendritic cells are phagocytes and can activate certain types of T cell. transport antigens to the lymph nodes
      • macrophages involved in phagocytosis. secrete toxic chemicals. present antigens to T cells and secrete cytokines
      • spleen filtersthe blood and lymph
      • the immune response is the coordinated reaction of these cells and molecules to infectious microbes
        • non specific immunity is always present in healthy individuals
          • the non specific defences include inflammation, interferons, natural killer cells, skin, sebum, mucous membranes,
        • Specific immunity stimulated by microbes invading tissues and has slower response to microbes
        • pathogens are viruses, bacteria, fungi, protozoa, multicellular parasites
      • inflammation is a series of events where proteins, fluids and phagocytes in an injured or infected area are accumulated
        • neutrophils and macrophages anre involved
        • four signs are redness, heat, swelling and pain
      • interferons are proteins secreted by leukocytes and virus infected cells
        • 3 types, alpha, beta and gamma
          • alpha and beta secreted when a viral nucleic acid enters host cell. kills host cells and induces death in neighbouring cells
          • gamma secreted by T cells and NK cells, inhibits viral replication
            • also enhanced phagocytosis, boosts antibody production in B cells, activates NK cells and cytotoxic T cellsand inhibits cell division
      • complement system is part of the non specific response, has two pathways of activation
        • alternate and classical pathways
          • classical is binding antibodies to bacteria and is part of specific defense mechanisms
          • alternate is binding to carbohydrates on the bacterial cell walls, part of nonspecific immunity
      • antibodies are made of two heavy and two light chains, with a constant region and a variable region which gives specificty
        • 5 classes of antibody, IgM, IgD, IgG, IgE and IgA
          • antibodies can neutralize, agglutinate, opsonize, activate complement and enhance NK activity
            • opsonization is when the binding of the antibodies enhances the phagocytosis
            • neutralization is when the binding blocks the antigen activity
            • agglutination is when the antibodies bind to the pathogen, clumping it togethre
            • complement activation is when the antibodies activate the complement cascade resulting in lysis of the cell
      • major histocompatibility complex marks cells as self
        • two classes of MHC, class 1 present on all nucleated cells, Class 2 present in macrophages, activated B and T cells and thymus cells
    • Hormones
      • steroid hormones are lipids that enter a target cell
        • are slow acting and long lived
      • peptide hormones bind to a cell surface receptor on a target cell
        • are fast acting and short lived
      • endocrine glands release hormones into the blood
      • adrenal gland, thyroid gland, pituitary, role and control of anterior pituitary, endocrine pathways
      • responsive hormones include adrenalin, cortisol and thyroxine
      • prostaglandins are local hormones released from blood vessels and platelets and dont travel great distances
      • the sympathetic medullary system controls the adrenal gland
      • pheromones are used for sexual attraction and have other roles in synchronization
      • exocrine glands release hormones into a duct
      • trophic hormones come from the pituitary
        • stimulate growth
      • chromaffin cells make adrenalin
      • adrenalin raises blood glucose, suppresses insulin secretion and stimulates glucagon secretion
      • adrenaline and noradrenaline both increase heart rate, dilates voluntary muscle arterioles, constrict arterioles in skin, gut, dilates bronchi
      • adrenalin has two receptors, alpha and beta
      • hypothyroidism symptoms include lethargy, weakness, obesity, bracycardia, dry skin
      • anterior pituitary produces growth hormone, thyroid stimulating hormone, FSH, LH and ACTH
      • adrenal cortex made up of zona reticularis, zona fasciculata, zona glomerulosa
      • cortisol suppresses the immune system
      • hyperthyroidism symptoms include high temperature, nervous, hyperactive, underweight, tachycardia, flushed moist skin
      • hormones in thyroid gland are derived from iodination of thyroglobulin
        • 2 main thyroglobin groups are thyroxine and tri-iodothyronine
        • thyroid gland needed to regulate temperature, growth and development and nervous system activity
      • there are thyroid hormone receptors on nuclei of most cells
      • infundibulum connects the pituitary to the hypothathalamus, contains nerves and vessels
      • osteoid contains crystals of calcium and phosphate, made of osteoclasts and osteoblasts
        • osteoblasts are bone forming cells and produce new matrix which is mineralised
        • osteoclasts are large multinucleate cells that secrete H+ cand hydrolytic enzymes. used in bone resorption
      • pituitary has 2 lobes the anterior at the front and the posterior in the back
      • parathyroid hormone controls amount of calcium in the body
        • the calcium receptors on secretory cells detect extracellular calcium concentration
          • can stimulate osteoclasts to resorb bone, kidney stimulation and intestinal uptake
      • calcitonin inhibits osteoclasts reducing bone absorption
      • hormone secretion controlled by ions, nutrients, neurotransmitters and other hormones
      • peptide hormones are made as preprohormones, then cleaved to prohormones then are activated
      • steroid hormones are derived from cholesterol
      • in females the mullerian ducts develop and the wolffian ducts regress
      • sex hormones are involved in sex differentiation, gametogenesis, behaviour, menstrual cycle, pregnancy, birth and lactation
        • for the first six weeks of gestation the gonads are indifferent
        • under paracrine action
      • SRY genes only present on Y chromosome as it is used to develop testes
        • stimulate release of mullerian inhibiting substance and testosterone. causes mullerian ducts to regress
      • interstital cells/leydig cells respond to LH, producing testosterone
        • leydig and sertoli cells work together as part of the sperm production process
          • sertoli cells all held together by tight junctions, nourish developing sperm
      • oxytocin has roles in birth, feeding infant, promoting contrations in uterus, helps to expel milk after birth
      • lactation uses various placental hormones, prolactin
      • when the ovarian cycle ceases the ovaries are unresponsive to FSH and LH, dont secrete oestrogen and progesterone
    • Renal system
      • kidney is used to maintain extracellular fluid so it is at constant level, regulates plasma ionic composition, plasma volume, osmolarity, pH, removes metabolic waste products, excretes H+ urea, creatin, secretes erythropoietin, renin and activates vitamin D3.
      • urinary system made up of kidneys, ureters, bladder and urethra
        • ureters conduct urine from the kidneys to the bladder
        • the bladder is an expandable organ that stores urine until it is expelled from the body
        • urethra is used to excrete urine from the bladder to outside of the body
      • kidneys are endocrine organs that secrete erythropoietin, stimulate bred blood cell production
        • kidneys secrete renin which is needed for production of angiotensin II
          • Angiotensin II is a hormone involved in regulating salt and water balance needed for long term blood pressure
      • receives 20% cardiac output at rest, is less than 1% of body weight and uses 16% ATP
        • kidney is bean shaped and around 115-170g. has three regions
          • renal cortex is the outer granulated layer
          • renal medulla is a cone shaped tissue with masses called renal pyramids
          • renal pelvis is the central cavity that is continuous with the ureter
      • kidney is bean shaped and around 115-170g. has three regions
        • renal cortex is the outer granulated layer
        • renal medulla is a cone shaped tissue with masses called renal pyramids
        • renal pelvis is the central cavity that is continuous with the ureter
      • 1 million nephrons per kidney, made of renal corpuscle and renal tubule
        • renal corpuscle is formed from two parts-glomerulus and bowmas capsule
          • glomerulus is a tangled capillary network for filtration
          • bowmans capsule is the enclosing chamber made of two layers. it receives the filtrate and the inflow to renal tubules
        • renal tubule made of proxiaml tube, loop of henle, distal convoluted tubule and collecting duct
          • loop of henle is a U shaped structure that has a descending limb to allow water to leave and an ascending limb that pushes out salt
          • collecting ducts serve to carry urine to the renal pelvis
          • proximal convoluted tubule is an epithelial layer with a brush border of microvilli to allow reabsorption of filtrate components
        • 2 types of nephron, cortical and juxtamedullary
          • juxtamedullary has a long loop of henle that extends into the medulla.
            • responsible for medullary osmotic gradient
          • cortical have short loop of henle and are most numerous
      • nephron function is to carry out basic renal exchange processes
        • involved in secretion, reabsorption and glomerular filtration
          • glomerular filtration is when the water and small molecules move from the glomerulus to the glomerular capsule while large molecules and formed elements remain in the glomerular blood
      • juxtamedullary apparatus is part of the distal tubule that comes into contact with nephron's afferent and efferent arterioles
        • two componenets, macula densa and granular cells or JG cells
          • macula densa are specialized clusters of tubule epithelial cells, monitor level of salt contained in fluid within tubule
          • granular cells are specialized cells in the wall of afferent arterioles and have cytoplasmic granules containing renin
      • renal arteries enter the kidney at hilus direct from aorta and the renal veins exit at the hilus

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