1.Chapter 5Coordination and regulation:Endocrine systems

2. Environments Extracellular environmentExtracellular fluids: Tissuefluid, Plasma, Cerebro-spinal fluid & Lymph Intracellular environment Intracellular fluid: Cytosol Exchange of substances between all, therefore, blood tests can provide info about the state of cells in other parts of the body. 3. Internal Environment 4. Homeostasis Maintenance of a relatively (narrow limits)stable internal environment. 5. What stops / prevents homeostasis occuringeffectively?Cant restore values to a normal state if....infection, trauma, toxic substances, auto-immune diseases, inherited disorders, extremeconditionsWhat variable are subject to homeostasis?NutrientsBlood volumeTemperature Blood pressureWater OxygenIons, such as Na+, Cl- Carbon dioxidepH (H+ concentration) Red blood cells 6. NEGATIVE FEEDBACK Step1: Detect change from a stable state. Step 2: Counteracting change=> NEGATIVEFEEDBACK 7. Controlling Blood Glucose (negative feedback involving hormones)Organ: Pancreas (Islets of Langerhans)Hormones:Insulin GlucagonCells: Beta cellsAlpha cellsTriggered Response:Helps cells absorb Glycogen --> Glucose glucose Decrease blood sugar Increasingblood sugarlevels Draw the summary of events that occur to maintain arelatively constant level of blood glucose in a normalperson. (fig 5.9 p141) Label the sensors and effectors. 8. POSITIVE FEEDBACK Most hormones are regulated via negative feedback but positive feedback exists as well. Hormone produced by a gland acts on same gland and stimulates it to produce more of the hormone Example: Oxytocin produced by pituitary gland 9. Cell communication Signalling molecules: Hormones (Chemical) Neurotransmitters (Electrical) 10. Signalling Molecules eg: hormonesA chemical produced in one part of an organism that can betransported in the blood stream to another part where it exerts itseffectOR act on the of hormone OR diffuse through tissue fluid & act on Types same cell Propertiesnearby cellsAmino acid derivatesstored in vesicles untilrequired, short life spanwater soluble & travel inblood stream (cant passcell membrane)Eg. tyrosine (thyroid glandhormones)Peptide and protein made in advance & storedhormonesin vesicleswater soluble & travel inbloodstreamEg: TSH & InsulinSteroid hormonessynthesised on demand,long life spanEg: testosterone & 11. Cells only respond to signalling molecules if it has aspecific receptor for that molecule (hormone receptors arespecific) Receptors can be located on the membrane ORin thecytosol eg: aa & protein/peptidesteroid1) Hormone binds to receptor (membrane / cytosol)2) Signal detected within cell3) Signal Transduction: passing of the message from thereceptor to the nucleus (which will elicit a response) - series of events from cytosol receptor to nucleus (egsteroids) OR - series of events involving a 2nd messenger or Gprotein (eg aas & pps)4) Response - activation of genetic material 12. Pheromones Pheromones are chemical signalling moleculessecreted by animals (particularly insects) They influence the behaviour of members of thesame species, often as sex attractants. Examples: Moths -> large feathery antennae with smellreceptors. Male follows sent of female. Candetect odours from miles away 13. can pass throughsecond messengercell membrane change cellLipophobicHydrophobicfunction affecting target membrane boundreceptors are in the cellsreceptorcytosolspecific receptorlonger life-spanshorter life-spanSmall signaltransductionprotein carriers fortravel freely in bloodblood transport possible amplificationaas, proteins SteroidsLIPIDWATERSOLUBLESOLUBLE 14. Hormones as plant regulators Auxins Cytokines Gibberellins Abscisic acid Ethylene 15. Auxins Auxins control enlargement and elongation of plantcells They stimulate growth from the apex down thestem Auxin can also inhibit the growthof roots if the concentrationis too high They are produced bythe growing tips of plantsand are water soluble 16. Indoleacetic acid (IAA) Responsible for apical dominanceapical dominance is thephenomenon whereby themain central stem of the plantis dominant over (i.e., growsmore strongly than) other sidestems 17. Tropism and auxins Tropism: the growth of a plant in response to astimulus Phototropism: response to light Geotropism: response to gravity 18. Cytokinins Another growth promoting hormone that acts on shoots, roots and fruits Cytokinins promote cell division and are involved in cell growth and diferentiation They are often used by gardeners (for example, in rooting powder) prior to planting to help promote root developmentwith cytokinins 19. Gibberellins Promote cell elongation and reproduction. Initiate seed germination and bud development. Read p. 157 & draw a flow diagram to represent the way that gibberellic acid promotes the germination of wheat.1) Water (fire / something) is needed to activate gibberellins to make gibberellic acid2) That changes the DNA which allows starch to be converted in glucose3) Respiration can start and growth can begin.Explain how / why some trees can havevery different juvenile leaves compared to theiradultleaves 20. Abscisic acid (ABA) Inhibits growth and influences stomatal closure. What prevents young leaves from falling off a tree? Some plants produce and accumulate abscisic acid in their leaves if they begin to wilt. It reduces water loss by causing the stomata to close.The separation of fruit or leaves from an adult plant:abscission.Before a leaf falls (for example, deciduous trees losingtheir leaves in Autumn), an abscision zone forms. NOTcaused by abscisic acid.Draw a diagram to illustrate this (p.159) 21. Ethylene Ethylene is a gas produced by a range of fruits (eg:apples, bananas, tomatoes, avocados and mangoes). Itassists in the ripening of the fruit by increasing the rateof respiration in the fruits cells. Petals in flowers die because of an increase in ethylenewhich leads to faster cellular respirationFlorigen ???A hormone produced in the leaves and transported via thephloem to the the buds of flowering plants may exert a effecton the production of flowers.Night and day length is known to be of importance butgenerally speaking, the control of flowering 22. C 23. D