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Bio 162 Module 4
Ppts: 14, 15, 16 , 17
| Question | Answer |
|---|---|
| What are the 2 types of systems we could have? | Closed and Open Systems |
| What is a closed system? | When nothing goes in or out (it is separate from the environment) |
| Does a closed system tend towards or away from equilibrium? | Tends towards equilibrium |
| What is equilibrium? | When there is stasis, no change, no movement, no life |
| What is an open system? | When stuff goes in or out (allows for interaction with the outside world) |
| Does an open system tend towards or away from equilibrium? | Tends away from equilibrium |
| Are most biological systems open or closed? | Open |
| What is flow? | The movement of some variable in an open system (ex. water, hormone, energy) |
| What are the 2 types of open systems? | Steady and Non-Steady States |
| What is a steady state? | When the rate of the flow in equals the rate of the flow out |
| What is a non-steady state? | When the rate of the flow in does not equal the rate of the flow out |
| T or F: A steady state means you are at equilibrium. | False, equilibrium has no movement, change or flow, whereas a steady state does, just the rate in equals the rate going out |
| What are the two types of organismal systems? | Conformers and Regulators |
| What is a conformer? | An organisms that adobt the same characteristics as their environment for a given variable |
| Can conformers control flow? | No, conformers cannot control flow |
| What is a regulator? | An organism that maintains a particular characteristic for a given varaible regardless of environmental conditions |
| Can a regulator control flow? | Yes, regulators can control flow (within limits) |
| What are the 3 principles of regulations? | 1) Organisms must control/regulate (at least some aspects of their) internal environment 2) Homeostasis 3) Organisms only regulate what they must for survival because regulation has a cost |
| What is homeostasis? | When organisms maintain a target "setpoint" for select physiological processes |
| T or F: Regulation costs. | True |
| Can an organism be an intermediate between a conformer and regulator? | Yes, some organisms have some ability to regulate, but not very much |
| What are feedback systems? | Where the present state of the system influences and directs the next state |
| What are the 2 feedback systems? | Positive and Negative Feedback Systems |
| What is a positive feedback system? | When the present condition accelerates a deviation in the same direction (reinforces deviations further) |
| Can a positive feedback system move below the y-axis average? | Yes, as long as it is deviating from the average it is positive feedback |
| What is a negative feedback system? | Present condition initiates events that return the system to pre-existing value or minimizes disturbances (minimizes deviations) |
| What feedback system do biological systems often use to regulate important variables and maintain homeostasis? | Negative feedback |
| What are the 4 functional elements of a negative feedback system? | Sensor, Set Point, Comparator, and Effector |
| What is a sensor in a negative feedback system? | Senses the level of a variable (ex. temperature) |
| What is a set point in a negative feedback system? | The desired level of the variable (ex. 98.4 degrees F in humans) |
| What is a comparator in a negative feedback system? | Compares the output of the senor with that of the set point: -If outputs are similar, no change is initiated -If outputs are different, comparator generates an error signal |
| What is an effector in a negative feedback system? | Regulates the level of variable to bring it to the setpoint |
| T or F: Two or more systems often work antagonistically to achieve better regulation. | True |
| What are the two types of communication that biological systems can do? | Chemical (both metazoans and embryophytes) and Electrical (metazoans) |
| What is an example of an endocrine chemical communication system? | Hormones |
| What are the elements of a communication system? | The source (the information), the channel (the signal), and the receiver (results in meaning) |
| T or F: Receivers do not give signals | False, receivers give signals |
| What does distortion do? | Changes the information in the channel |
| What does noise do? | It can compete with the signal at the receiver |
| What are the 3 chemical communication systems in animals? | 1) Autocrine 2) Paracrine 3) Endocrine |
| What is the autocrine system? | When the message acts on the cell secreting it |
| What is the paracrine system? | When the message travels via diffusion to act on cells nearby the secreting cell |
| What is the endocrine system? | When the message travels via bulk flow (circulatory system) to act on cells far away from the secreting cell |
| What are endocrine glands? | Ductless glands, in which cells secrete signals that diffuse to the circulatory system, and the signals circulate to target tissue (ex. polar and non-polar hormones) |
| What are exocrine glands? | Secrete into a duct that typcially leads to the GI tract or surface of the organism (ex. pheromones) |
| What are pheromones? | A chemical substance produced and released into the environment by an animal, especially a mammal or an insect, affecting the behavior or physiology of others of its species (ex. Nasonov's gland in honeybees) |
| What are the 2 types of hormones? | Polar and Non-polar hormones |
| What are polar hormones? | Hydrophilic molecules that are dissolved directly into the plasma, but need receptor (protein) to enter cell |
| What are non-polar hormones? | Hydrophobic molecules that need protein carriers to travel through blood, but can cross the cell membrane un-aided (without a receptor) |
| T or F: Non-polar hormones travel in the blood without carrier proteins. | False, non-polar hormones need carrier proteins to travel in the blood |
| What is the source in the hormone communcation system? | The endocrine glad--> releases the signal that diffuses to the circulatory system |
| What is the channel in the hormone communication system? | The hormones--> bulk flow signal travels via the circulatory system (polar and non-polar) |
| What is the receiver in the hormone communication system? | The target cell--> expresses the receptor(s) for a particular hormone and changes in response to the hormone |
| Receptors (in membrane, cytoplasm, or nucleus) can vary in their... (2) | 1) Affinity 2) Concentration |
| What are the 2 types of target cell receptors? | Membrane bound receptors and cytoplasmic/nucleoplasmic receptors |
| What do membrane bound receptors do? | Increase/decrease concentration of second messangers or produce intramembrane second messangers |
| What do cytoplasmic/nucleoplasmic receptors do? | Act as transcription factors and modify the rate of synthesis of mRNA for one or more proteins |
| T or F: Metazoan endocrine signals often travel via the circulatory system. | True |
| Are cnidarians radially or bilaterally symmetrical? | Radially symmetric |
| What serves as the bulk flow system in cnidarians? | Movement of fluid in the gut |
| What constraints dictate the size and shape of cnidarians? | Constraints of diffusion...at large sizes, increasing complexity of the gut cavity increases surface area for diffusion |
| Is bulk-flow directed or non-directed in cnidarians? | Bulk flow is non-directed |
| How is fluid movement generated in cnidarians? | By muscles in the body wall and cilia in the gut cavity |
| Is there any differences in the circulatory systems of other metazoans that have bilateral symmetry compared to cnidarians? | No, just soem will develop/evolve a second gut opening (anus) |
| Is there any differences in the circulatory systems of metazoans with body cavities (pseudocoelomate and coelomate) compared to cnidarians? | Yes, their fluid filled body cavities that surround organs and the GI tract, can serve as a bulk flow system (rather than just the gut) |
| Is there any differences in the circulatory systems of metazoans with vascular systems (open and closed) compared to cnidarians? | Yes: -They carry fluid from loading sites to unloading sites, at which gasses, nutrients, metabolic waste, and hormones diffuse between the circulating medium and the tissues -Bulk flow is directed -Fluid movement is generated by a pump (heart) |
| What are vessels? | Tubes that organize and direct bulk flow in vascular systems |
| What manages the direction of fluid flow in vascular systems? | Valves |
| What are the 2 types of vascular systems? | Open Vascular Systems and Closed Vascular Systems |
| What is an open vascular system? | When connective fluid (hemolymph) moves through defined vessels, but exchange occurs in open sinuses (see arthropods example of slide 14) |
| What is a closed vascular system? | Connective fluid (blood) moves through defined vessels and exchange occurs across walls of small vessels called capillaries (see cephalopods example on slide 14) |
| Hemolymph v. Blood | Hemolymph--> does not contain red blood cells and hemoglobin Blood--> contains red blood cells and hemoglobin |
| Is the plant embryo dependent on its parent for nutrition or can it rely on its own photosynthesis? | Plant embryos cannot rely entirely on their own photosynthesis for nutrition |
| What is a dormant state for a plant embryo? | In a dormant state, a plant embryo is waiting for the proper conditions to begin growth |
| What is germination for a plant embryo? | When conditions are correct for a dormant seed to resume growth |
| How does a plant embryo break seed dormancy? | The embryo mobilizes its reserves: It imbibes (takes up) water and swells, and secretes gibbberellins that turn on the synthesis of enzymes that assist in breaking down the stored nutrients in the endosperm, so that the embryo can easily use them |
| What are gibberellins? | Plant hormones that turn on the synthesis of enzymes that assist in breaking down the stored nutrients, so that the embryo can easily use them |
| What is phototropism? | Movement in plants; while plants can't move from where they are rooted, they can still make movements that allow them to find more favorable light (including in competition with other plants) |
| Who ran the phototropism experiments? | Charles Darwin and his son Francis |
| What is a coleoptile? | A sheath of cells that surrounds shoot apical meristem in certain plants |
| How did the Darwins run their phototropism experiment and what was the result? | They blindfolded certain areas of the plant and discovered that the tip of the coleoptile sensed light -- not the entire structure, as only the tips bent away from the light |
| How does phototropism work? | Light is sensed by specialized proteins called phototropins, the hormone auxin is moved to the side of the plant that is in the shade, away from light, which leads to cell expansion by making the cell wall acidic and breaking bonds between fibers |
| What are phototropins? | Specialized proteins that sense light |
| What is auxin? | The hormone that is responsibel for phototropism |
| What is phototropism in simpler terms? | Cell expansion on the "shady side" that causes the plant to bend towards light |
| How does auxin increase cell expansion? | It activates proton (H+) pumps in the plasma membrane that reduce the pH (more H+) in the cell wall, allowing cell expansion |
| T or F: Embrophyte signals can travel via a variety of channels. | True |
| Summarize the movement of water, minerals, and horomones from the roots. (3) | - One direction - Short distances--> apoplast and symplast - Long distances--> convection through the xylem (tubes composed of stacked hollow, dead cells) |
| Summarize the movement of photosynthetic products in plants. (3) | -Multi-directional -Short distances--> apoplast and symplast -Long distance--> convection in the phloem (tubes composed of stacked living cells) |
| What 2 things are responsible for embryophyte local travel? | The apoplast and the symplast |
| How does local travel through the symplast work? | Entry to the symplast requires crossing a cell membrane... once in the symplast, water and solutes can also move through plasmodesmata |
| How does local travel through the apoplast work? | Water and solutes can move through the apoplast without passing through the cell membrane |
| How does water move in the xylem? | The very small diameter tubes allow for capillary action, involving a cohesion-tension mechanism |
| What is cohesion? | A result of strong bonding between water molecules |
| What is adhesion? | Bonding between the walls of the tube and water |
| What is capillary action? | In thin tubes, there is a high internal SA/V ratio, where water interacts with tube walls by adhesion and tends to climb the walls against gravity, while cohesion pulls up water not in contact with the walls |
| T or F: Due to the mass of water, large tubes with low SA/V are able to pull water better against gravity | False, small tubes with high SA/V are able to pull water better against gravity |
| What is water potential? | The energy gradient that describes how water "wants" to move in response to both osmotic potential (concentration gradient) and pressure potential |
| Does water move towards areas of lower water potential or higher water potential if there is a path? | To areas of lower water potential |
| T or F: Water in the xylem is pushed, not pulled. | False, water in the xylem is pulled, not pushed |
| Is water potential higher in the soil or in the air? | Water potentials are highest in the soil, where there is a high level of solutes in the water, whereas it is lowest in the air |
| What is transpiration in plants? | The process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems, and flowers |
| What are xylem used to transport? | Water, minerals, and hormones |
| What is phloem used to transport? | Photosynthates (sugars) |
| Is electrical or chemical communication faster? | Electrical communication is faster than purely chemical communication |
| T or F: The nervous system is found in all Metazoans (except sponges). | True |
| How is biochemical communication achieved? | By changing the concentration of charged particles (ions) across a cell membrane |
| What are ions? | Charged particles |
| What are the only two types of cells that generate action potentials? | Neurons and muscle cells |
| What are the 4 parts of a neuron? | Dendrites, cell body/soma, axon hillock, and axon |
| What are dendrites? | The main structure to receive signals from other neurons |
| What is the cell body/soma? | The area that contains the nucleus and most cell organelles, and can receive the signal from the dendrites |
| What is the axon hillock? | The location of summation, in which information collected by the dendrites is integrated and generates action potentials |
| What is the axon? | The area that carries and passes along a signals |
| What kind of membrane is a metazoan cell membrane? | A lipid bilayer |
| Can ions diffuse across the lipid bilayer membrane? | No |
| Can the ions move in the aqueous solutions on either side of the membrane? | Yes |
| What do you need in order to move ions across membrane? | Driving forces and pathways |
| What are the 2 types of driving forces for ions? | Chemical gradients and electrical gradients |
| What is a chemical gradient and what is the driving force? | Aka concentration gradient... the concentration differences across the membrane that can exist... driving force is high to low concentration |
| What is an electrical gradient and what is the driving force? | Charge differences across the membrane can exist... driving force is attraction to the opposite charge |
| T or F: Driving forces can be in the same or opposite directions depending on the situation. | True |
| What is permeability? | The ability of a given ion to move across a membrane |
| What are pumps? | Proteins that require energy to move ions across the membrane against their concentration gradient...establish ion concentration differences in the process |
| What are thr 2 pathways across the membrane for ions? | Pumps or channels |
| What are channels? | Transmembrane proteins that allow movement of ions through the membrane |
| What are the 2 types of channels? | Leak channels and gated channels |
| What are leak channels? | They always are open and allow specific ions to cross the membrane in accordance with electrochemical gradients |
| What are gated channels? | They open and close under specific conditions (bonding to a ligand or voltage change), changing local charge distribution when they open or close |
| What is membrane potential (Em)? | Measured as the difference in charge across the membrane |
| What is resting membrane potential (Erest)? | The charge difference when no signals are being sent |
| When there is no external signal, you are at... | resting potential |
| What are everywhere in the neuron? | Na+/K+ pumps and K+ leak channels |
| What is depolarization? | A change in membrane potential (Em) in a positive direction from resting membrane potential (Erest) (more positive ions in) |
| What is hyperpolarization? | A change in membrane potential (Em) in a negative direction from resting membrane potential (Erest) (positive ions out) |
| What is repolarization? | A return towards resting membrane potential (Erest) after a disturbance |
| Do external signals cause changes in membrane potential? | Yes |
| What are synapses? | The points of communication between neurons |
| What are the two types of synapses? | Chemical--> the cells approach but do not touch; communication is paracrine (to other cell via diffusion) Electrical--> the cells are joined by gap junctions and the action potential simply travels from one cell to the next |
| What are the 3 components of chemical synapses? | - Presynaptic cell -Postsynaptic cell -Synaptic cleft |
| What is the presynaptic cell? | The axon terminal (with neurotransmitters) |
| What is the postsynaptic cell? | Contains receptors that can bind to the presynaptic neurotransmitter |
| What is the synaptic cleft? | The space between the two cells |
| What is an excitatory post-synaptic potential (EPSP)? | Ion channels open and positive charges enter the postsynaptic neuron (depolarization), causing an EPSP |
| What is an inhibitory post-synaptic potential (IPSP)? | Ion channels open and the postsynaptic neuron gains negative charges or loses positive charges (hyperpolarization), causing an IPSP |
| T or F: The same neurotransmitter may interact with both inhibitory and excitatory receptors. | True |
| What are the receivers in the ion pathway and what occurs? | The soma and the dendrites are the recievers, as ligand-gated channels respond to a neurotransmitter to generate a passive/graded potential |
| What are passive (graded) potentials? | Relatively small disturbances in membrane potential (Em) from resting membrane potential (Erest) that may be a depolarizing or hyperpolarizing signal (moves away from the origin in either direction) |
| In a passive (graded) potential, what happens to the signal as it moves away from the origin? | Its strength decays expontentially |
| Can passive (graded) potentials sum? | Yes, passive potentials produced in different places of the cell can add together |
| What are neurotransmitters? | Chemical substances that bind to receptors on the postsynaptic cell, triggering changes in ion permeability and generating passive (graded) potentials (postsynaptic potentials) |
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