12 04 2014 Chemical Information Transfer I Hormones are formed and secreted in specialized cells travel in body fluid act on specific target cells their job is to change that cell s function Types of hormones Endocrine o Hormones are secreted into long distance transport system blood o Travel a far distance and trigger a response o Most common Paracrine o Works locally o Secreted and acts on neighboring cells o Common in developmental daughter cells Helps the daughter cell determine its path differentiate o Act by diffusion Autocrine signaling Synaptic neurons Neuroendocrine o Cells signal themselves quorum sensing o Signaling between 2 cells where one or both of them are o Signal is a neurotransmitter o Leaves the synapse and effects the receptors of the other cell o Neuron releases neurotransmitters into the bloodstream for long distance transport to effect cells throughout the body Hormonal signaling stimulus Input cell takes up a stimulus Output of the cell is the release of the hormone as a result of the Vesicles inside the cell End result of STP is the fusion of the vesicle with the plasma membrane releasing the hormone Hormones in vesicles need to be water soluble but not fat soluble because if they were fat soluble they would just diffuse out of the vesicle You must get the hormones into long distance transport systems This hormone is a stimulus for another cell that will trigger an internal or external response Stimuli That Trigger Hormone Release Chemical signals o Binding to a receptor Dependent on concentration More chemical signal you have the more the signal will be read o Redox signals You can oxidize or reduce some part of the receptor protein causing a conformational change Light o In pants it is important for photosynthesis o Circadian rhythms Biological clock o We need a photoreceptor to respond to light o Absorption of a photon causes conformational change Mechanical Neurotransmitter o Stretch receptors when you get touched o Released by neuron o If it effects another neuron its job will be to create an action potential o If it effects another type of cell it can have many different responses usually messenger Responses to hormones are always mediated at the cellular level The response to the hormone is always intracellular within you but the whole thing is extracellular because the hormone is coming from another cell so it is the coupling of 2 hormones All or nothing response Concentration of the stimulus determine the response Minimum concentration needed for a response threshold Due to positive feedback Feedback is most likely in the form of the response not the hormone Concentration dependent The more of the hormone you have the higher the response Graded potential o Epinephrine controls heart rate Supporting hormones o Development and sex hormones o Thyroxin helps maintain a constant metabolism o Levels are relatively stable over time Antagonistic hormones o Involved in achieving homeostasis o Insulin and glucagon fight each other to maintain blood glucose levels o Even at set point the hormones are constantly being released Complex neuro endocrine pathways Neurons in the hypthalymus will secrete hormones into the posterior pituitary which will dump them into the blood Binding of hormone to neuron can trigger action potential because if a hormone can bind to the same receptor that a neurotransmitter can it will have he same effect Competancy to respond Different cells and tissues have different responses to the same Whether or not you will respond to a given hormone is determined hormone during development o During development the daughter cells will gain new characteristics from extracellular signals like which pathway to take o One of these characteristics will be which hormones to respond to by have the right signal transduction pathway Pheromones Released into the environment or outside the organism Can often go into the gas phase and be detected Often present during sex Often volatile compounds Cause aggression Chemical Information Transfer II In a plant cell the hormones are secreted into the apoplast The apoplast and interstitial fluid are basically equivalent because they are both liquid areas where diffusion can occur between neighboring cells and the hormones are both secreted in both Covalently bond hormone to something membrane impermeable like a sugar to be able to store it inside a vesicle There must be a transport protein to get a hormone into the capillaries but the hormone can leak out via the gap junctions o This is good because this way hormones will only enter into the places they are meant to enter o But you can get things into the blood without transport proteins if they are small enough like alcohol Auxin Coleoptile responds to directional light via phototrophic movement Exhibits polar transport shoot to root When photons hit coleoptile the auxin is the hormone that is being activated Since pH is lower outside the cell auxin will go into the cell and ionize and it will leave via reflux transporters Diffusion occurs between two cells and cytoplasmic streaming speeds things up in the cell The shoot apical meristem are located on the top tip of the baby seedling this creates all the above ground plant matter this utilizes auxin movement in every direction to create more plant matter Phytochrome Plant photoreceptor Red light photoreceptor When red light comes in contact with it it starts to germinate When the ratio of red to far red is very low not germinating it makes the plant grow taller to try to get more sunlight Phytochrome and photoperiodism Short day plants winter only flower when there are long nights and Long day plants summer only come up when there is short nights short days and long days Biological clock Circadian rhythms Between 16 30 hours Biological clock is synchronized with environmental clock o Entrainment how the environmental clock and biological clock synchronize o Every morning when the sun comes up the clocks Hormone concentration is not what turns the pathway on or off it is synchronize Feedback regulation the response that does that Electric Information Transport I Ion concentration as a cellular signal o calcium ions act as a second messenger in many of the signal transduction pathways of the body Membrane Potential and Electrically Excitable Cells o There is a voltage difference between the cytoplasm of the electrode and the reference electrode o The voltage the cell relative to the voltage outside the cell