Control Systems in Plants o Types of plant hormones Auxins Stem elongation differentiation apical dominance Cell division germination Seed bud fruit development Stem elongation different than auxins Cytokinins Gibberellins Abscisic acid Ethylene Inhibits growth closes stomata prevents germination Promotes fruit ripening programmed cell death leaf abscission response to mechanical stress Normal growth and development xylem differentiation pollen tube Apical dominance germination attract mycorrhizal fungi to the root Brassinosteroids elongation Strigolactones o Examples of hormone function Auxin in stem elongation Apical meristem produces auxin Transported down the shoot only Produces a decreasing concentration gradient High concentrations of auxin inhibit stem elongation Low concentrations of auxin promote stem elongation by activating H active transport mechanisms Auxin and Cytokinin in Apical Dominance Auxins inhibit lateral shoot development Cytokinins stimulate lateral shoot development o High concentration in roots low concentration in stem Opposite impacts on root branching Key Features Broad effects controlling major physiological processes Most occur in antagonistic pairs Plant Rhythms Some plant processes flowering etc follow a daily cycle suggesting plants have rhythms How do plants keep track of time o How much of something is degraded or produced Photoperiodism Some plants flower only when the days are long Some flower only when the days are short What is the mechanism Night length is what is critical Plants contain pigments call phytochromes o One part functions as a photoreceptor the other a protein kinase How does this control flowering Short day plant long night At night Pfr is slowly naturally converted to Pr Light flashes can reverse this process Chemical Signaling in Animals o Two major systems Endocrine neurons o Differences Endocrine system Nervous system o Similarities Hormones secreted into blood stream Nervous Neurotransmitters secreted into the synapse junction between Broadcasts the signal throughout a broad area via blood stream Sends the signal directly to a target cell via neuron s Many hormones are neurotransmitters Some neurons secrete hormones Both systems involve cells communicating with other cells Types of Hormones o Lipid soluble o Water soluble Speed of Response o Gene regulation Bind to cytoplasmic receptors Bind to membrane bound receptors Most often results in a slow response steroid hormones o Direct Cytoplasmic Response Generally a rapid response water soluble hormones Endocrine Glands o Glands that secrete release hormones into the blood stream o TABLE 45 1 Major ones kinds and functions Left side only o FIGURE 45 4 o Hypothalamus o Pituitary 2 types of hormones Posterior Anterior 7 hormones Controls other endocrine glands Portal vessels heart Endocrine System Regulation o Antagonistic pairs o Example blood glucose levels Glucagon and insulin 2 hormones secreted by neurosecretory cells in the hypothalamus o Heart artery capillary portal vessels capillary vein Both produced by the pancreas Glucagon o Stimulates the breakdown of glycogen to glucose Insulin o Stimulates the conversion of glucose to glycogen If blood glucose levels rise what happens o Insulin released If they fall what happens o Glucagon released Insulin release increases If you eat a big meal and blood glucose levels rise sharply what happens Six hours after that meal blood glucose levels are dropping what happens Glucagon release increases o Negative feedback system Example thyroid hormones regulate overall metabolism Hypothalamus THR anterior pituitary TSH thyroid thyroxine triiodothyronine hypothalamus anterior pituitary thyroid What would be expected to happen to the levels of TSH if the TRH receptors in the anterior pituitary are constantly bound and stimulated with TRH like active molecules Increase Type 1 Diabetes occurs when the pancreas stops producing insulin type 2 diabetes occurs when your cells no longer respond to insulin both result in uncontrollable blood glucose levels Based on the data below choose the most likely diagnosis for the Patient 1 Blood Glucose Mg dL Normal 90 100 Patient 1 210 Insulin mU mL 32 162 CORRECT ANSWER Type 2 Diabetes Integration of Endocrine and Nervous Systems o Neurosecretory cells Neurons that secrete hormones Form an important link between endocrine and nervous systems Turkey and Sleep Nervous System o Tryptophan is required for serotonin and melatonin synthesis o Serotonin is a neurotransmitter signal molecule linked to sleep and sleep patterns o Melatonin is a hormone related to circadian rhythm o Composed of specialized cells that can transmit action potentials from one cell to another one location in the body to another o Neurons Types of neurons Sensory o Receptor to CNS Interneuron o Between sensory and motor neurons Motor o From CNS to effector cell Structure of neurons Cell body Dendrites Axon Axon hillock o Place where cell body and axon are connected Myelin sheath some o Schwann cell wraps around axon o Not continuous coat Membrane Potentials o All cells have and electrical gradient or electrical potential across their cell membrane o Measured with outside being 0 o Inside is generally 50 to 100 mV o High Na outside o High K inside o High organic molecules inside o Na K pump pumps ions unequally o Na and K diffuse across the membrane at different rates Action potentials o All cell have membrane potentials o Muscle and nerve cells are excitable They can generate a change in membrane potential o If a depolarization is great enough threshold it will stimulate an action potential This involves voltage gated channels Gated channels o Excitable cells have special ion channels called gated ion channels A stimulus will cause a change in the gated channels o If K channels open causes Hyperpolarization o If Na channels open causes Depolarization Voltage Gated Channels o Differ in Ions allowed through Number of gates o Can have Na and K Na Channels 2 gates Activation gate opens Inactivation gate closes K Channels 1 gate Opens slow Action potential Na gate open o Is the result of the Na gate opening causing a rapid depolarization of the membrane o Follows by the closing of the Na inactivation gate and the opening of the K gate causing a repolarization of the membrane o This is then propagated along the neuronal membrane o The formation of an action potential in one location causes a depolarization in the surrounding areas
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