4 AuxinIs used for any chemical substance that promotes cell elongation in different target tissuesAuxin transportersMove the hormone out of the basal end of one cell, and into the apical end of neighboring cellsAuxinIs involved in the formation and branching of roots
5 Other Effects of Auxin Auxin affects secondary growth By inducing cell division in the vascular cambium and influencing differentiation of secondary xylemDeveloping seeds synthesize auxintomatoes grown in greenhouse conditions sprayed with auxin induce fruit development without a need for pollinationThis allows for seedless tomatoes
6 Charles Darwin and his son Francis Conducted some of the earliest experiments on phototropism, a plant’s response to light, in the late 19th centuryIn 1880, Charles Darwin and his son Francis designed an experiment to determine what part of the coleoptile senses light. In 1913, Peter Boysen-Jensen conducted an experiment to determine how the signal for phototropism is transmitted.EXPERIMENTIn the Darwins’ experiment, a phototropic response occurred only when light could reach the tip of coleoptile. Therefore, they concluded that only the tip senses light. Boysen-Jensen observed that a phototropic response occurred if the tip was separated by a permeable barrier (gelatin) but not if separated by an impermeable solid barrier (a mineral called mica). These results suggested that the signal is a light-activated mobile chemical.CONCLUSIONRESULTSControlDarwin and Darwin (1880)Boysen-Jensen (1913)LightShadedside ofcoleoptileIlluminatedTipremovedTip coveredby opaquecapcoveredby trans- parent capBase coveredby opaque shieldTip separatedby gelatin blockby mica
7 In 1926, Frits WentWent concluded that a coleoptile curved toward light because its dark side had a higher concentration of the growth-promoting chemical, which he named auxin.The coleoptile grew straight if the chemical was distributed evenly. If the chemical was distributed unevenly, the coleoptile curved away from the side with the block, as if growing toward light, even though it was grown in the dark.Excised tip placedon agar blockGrowth-promoting chemical diffuses into agar blockAgar block with chemical stimulates growthControl (agar block lacking chemical) has no effectControlOffset blocks cause curvatureRESULTSCONCLUSIONIn 1926, Frits Went’s experiment identified how a growth-promoting chemical causes a coleoptile to grow toward light. He placed coleoptiles in the dark and removed their tips, putting some tips on agar blocks that he predicted would absorb the chemical. On a control coleoptile, he placed a block that lacked the chemical. On others, he placed blocks containing the chemical, either centered on top of the coleoptile to distribute the chemical evenly or offset to increase the concentration on one side.EXPERIMENTExtracted the chemical messenger for phototropism, auxin, by removing the coleoptile tip & placed it on a block of agar. This will allow the chemical to travel through.
8 Photoperiodismplant's ability to flower in response to changes in the photoperiod: the relative lengths of day and night.research has shown that the dark period is more important than the light period. For example, if SDPs are grown under short-day conditions but the dark period is interrupted by a flash of light, the SDPs will not flower. The long night that normally accompanies a short day is interrupted by the flash. An interruption of the light period with dark has no effect.
12 Fixed Action Patterns (FAP) FAP is an instinctive behavioral response triggered by a very specific stimulus.Once triggered, the FAP behavior can’t be stopped ‘midstream’, but must play out to completion.
13 Egg Rolling and the Greylag Goose If one of the gooses' egg rolls away from the nest, the goose automatically rolls the egg back to the nest with a repeated, specific action. When the female notices an egg outside the nest (sign stimulus), she begins this repeated movement to drag the egg with her beak and neck.If, while the goose is rolling the egg back to the nest, the egg slides off to the side, or is removed by an observer, the goose continues to repeat the stereotypic movements, until she reaches the nest. She'll then relocate the missing egg and begin the process all over again.
16 HabituationAn organism decreases or ceases to respond to a stimulus after repeated presentations.
17 Operant Conditioninga method of learning that occurs through rewards and punishments for behavior. Through operant conditioning, an association is made between a behavior and a consequence for that behavior.
18 Classical Conditioning A learning process that occurs through associations between an environmental stimulus and a naturally occurring stimulus.It's important to note that classical conditioning involves placing a neutral signal (bell) before a naturally occurring reflex (salivating in response to food).Classical conditioning basically involves forming an association between two stimuli resulting in a learned response.
19 Taxis and KinesisTaxis has a specific and directed motion while kinesis has a random and undirected motion.Woodlice prefer moist areas so they will move around less than in dry areas. In dry areas they will move around a lot (randomly) until they hit upon a moist area
21 Magnification = size of image actual size of specimen 2. In Figure 12 the actual length of the mitochondrion is 8µm.(a) Determine the magnification of this electronmicrograph. (b) Calculate how long a 5 µm scale bar would be onthis electron micrograph. (c) Determine the width of the mitochondrion.Magnification = size of imageactual size of specimena) Magnification = image size = mm µm = 7875x ~ 8000xactual size µm µm8000 = X__ x 5 = 40,000µm = 40mm5µmc) Depending on your measurement location the image width is b/w 20mm & 23mm.We will use 20mm.magnification (8000) = 20,000 µm = ,000 / = 2.5µmX
23 Ionic Bonding A strong bond Opposite charge atoms bond & an electron is lost by one atom & gained by the other.Cation: when the charge of an atom is positiveThe atom lost an electronAnion: when the charge of the atom is negativeThe atom gained an electron
24 Ionic Bonds The formation of the ionic bond in table salt Everyday tablesaltNaCl Crystal
27 pHA convenient way to express the hydrogen ion concentration of a solutionpH=log [H+]_The pH scale is logarithmicA difference of one unit represents a ten-fold change in H+ concentrationAcidDissociates in water to increase H+ concentrationBaseCombines with H+ when dissolved in water
29 Buffers Hydrogen ion reservoirs that take up or release H+ as needed The key buffer in blood is an acid-base pair (carbonic acid-bicarbonate buffering system)Response to a rise in pHH2OWater inblood plasmaCO2Carbon dioxide+H2CO3Carbonic acid+–HCO3–BicarbonateionH+HydrogenResponse to a drop in pH
31 Hydrogen Bonds Give Water Unique Properties Water molecules are polar moleculesUnequal sharing of electrons & V-like shapeThey can thus form hydrogen bonds with each other and with other polar moleculesEach hydrogen bond is very weakHowever, the cumulative effect of enormous numbers can make them quite strongHydrogen bonding is responsible for many of the physical properties of water
33 THERMAL PROPERTIES High Heat of Vaporization High Specific Heat Water absorbs a lot of heat, hydrogen bonds break, then water turns to vapor & then evaporates.Water can absorb or release a lot of heat without changing its own temperature by very much.
35 Salt dissolves when all ions have separated from the crystal SOLVENT PROPERTIESMost of the important molecules in and out of the cell are polar molecules. These molecules create solutions that enable for biochemical processes to occur.Water is a versatile solvent because of its polarityProtein synthesis & glycolysisGas ExchangeSalt dissolves when all ions have separated from the crystalWater forms a hydration shell around each solute ion.Light independent processes of photosynthesis
39 SYNTHESIS AND BREAKDOWN OF POLYMERS Enzymes helpDehydration (Condensation) reactionTo connect monomers togetherA water molecule is releasedOne molecule gives up a hydroxyl group& the other a hydrogenHydrolysisPolymers are broken apart to monomersA water molecule is added to split apartthe monomersEX: Digestion
40 VARIOUS MONOSACCHARIDES What do all of these sugars have in common?They are made of one carbonyl group and several hydroxyl groups.What’s the difference between the top row of sugars compared to the bottom row?The top sugars have their carbonyl group at the end of the carbon skeleton & the bottom ones have their carbonyl group in the middleIdentify the difference between glucose & galactose.
41 Lipids Large nonpolar molecules that are insoluble in water They are NOT polymers but they are large molecules assembled from smaller molecules.Three major typesTriglyceridesPhospholipidsSteroids
42 Phospholipids A modified fat One of the three fatty acids is replaced by a phosphate and a small polar functional groupEssential to cells: they make up the cell membrane.
43 Nucleic Acids Serve as information storage molecules Store, transmit and help express hereditary informationLong polymers of repeating subunits termed nucleotidesA nucleotide is composed of three partsFive-carbon sugarNitrogen-containing basePhosphate
44 Protein Structure Primary structure Secondary structure The specific amino acid sequence of a proteinSecondary structureThe initial folding of the amino acid chain by hydrogen bondingTertiary structureThe final three-dimensional shape of the proteinQuaternary structureThe spatial arrangement of polypeptides in a multi-component protein
45 Enzymes Influence the rate of reaction A set of reactants present with enzymes will form products at a faster rate than without enzymes.Enzymes cannot force reactions to occur that would not normally occurThe enzymes role is to lower the energy level needed to start the reaction.Enzymes lower the activation energy of reactionsEnzymes are not used up during the reaction
47 EUKARYOTIC PROKARYOTIC Smaller & simpler Less than 10µm in diameter DNA in ring form without proteinDNA is free floatingNo mitochondria70S ribosomesNo internal compartmentalization to form organellesThought to be the 1st cells on Earth.Reproduce by Binary FissionEX: BACTERIABigger & more complexMore than 10µmDNA with proteins as chromosomes/chromatinDNA enclosed in nucleusMitochondria is present80S ribosomesInternal compartmentalization present to form many types of organelles.EX: EVERYTHING EXCEPTBACTERIA
49 Variations among Eukaryotic Cells Plant cellsAnimal cellsExterior of cell includes cell wallHave chloroplastsPossess large vacuole that’s centrally locatedStore carbohydrates as starchDo not contain centriolesHas a fixed often angular shapeExterior of cell includes plasma membraneNo chloroplastsVacuoles are usually not present or are very smallStore carbohydrates as glycogenHave centriolesIs flexible and more likely to be rounded in shape.
50 HOW ARE THE MITOCHONDRIA AND CHLOROPLASTS SIMILAR TO PROKARYOTIC CELLS? BOTH HAVE THEIR OWN DNASIZETHEY REPRODUCE IN A SEMIAUTONOMOUS MANNERTHEY ARE NOT PART OF THE ENDOMEMBRANE SYSTEMSOME PROTEINS NEEDED ARE MADE BY THEIR RIBOSOMES LOCATED IN THEIR MEMBRANE & OTHER PROTEINS ARE BROUGHT IN FROM THE CYTOSOL
51 Why do mitochondria & chloroplasts have so many membranes in them? For increased surface area used for the energy conversion processes that occur in these organelles.
53 Oxidation and Reduction Loss of electronsGain of electronsGain of oxygenLoss of oxygenLoss of hydrogenGain of hydrogenResults in many C – O bondsResults in many C – H bondsResults in a compound with lower potential energyResults in a compound with higher potential energyA useful way to remember: OIL = Oxidation Is Loss (of electrons)RIG= Reduction Is Gain (of electrons)These two reactions occur together during chemical reactions= redox reactions. One compound’s or element’s loss is another compound’s or element’s gain.
54 Respiration Glycolysis The citric acid cycle (Krebs Cycle) Breaks down glucose into two molecules of pyruvateThe citric acid cycle (Krebs Cycle)Completes the breakdown of glucoseOxidative phosphorylationIs driven by the electron transport chainGenerates ATP
55 Energy investment phase GlycolysisCitric acid cycleOxidative phosphorylationATP2 ATP4 ATPusedformedGlucose2 ATP + 2P4 ADP + 42 NAD+ + 4 e- + 4 H +2 NADH+ 2 H+2 Pyruvate + 2 H2OEnergy investment phaseEnergy payoff phase4 ATP formed – 2 ATP used2 NAD+ + 4 e– + 4 H +Figure 9.8GlycolysisHarvests energy by oxidizing glucose to pyruvateGlycolysisMeans “splitting of sugar”Breaks down glucose into pyruvateOccurs in the cytoplasm of the cellTwo major phasesEnergy investment phaseEnergy payoff phase
57 Before the Krebs cycle can begin….we have the link reaction Pyruvate must first be converted to acetyl CoA, which links the cycle to glycolysisCYTOSOLMITOCHONDRIONNADH+ H+NAD+231CO2Coenzyme APyruvateAcetyle CoASCoACCH3OTransport proteinO–Figure 9.10
58 The Krebs Cycle 6 NADH's are generated 2 FADH2 is generated 2 ATP are generated4 CO2's are releasedTwo turns for each molecule of glucose because each glucose is converted to 2 molecules of acetyl CoA.
59 ETC The resulting H+ gradient Electron transfer causes protein complexes to pump H+ from the mitochondrial matrix to the intermembrane spaceThe resulting H+ gradientStores energyDrives chemiosmosis in ATP synthaseIs referred to as a proton-motive force
60 Where do the electrons for the ETC come from? How does electronegativity play a part in the electron transport chain?Because each electron acceptor in the chain is more electronegative than the previous, the electron will move from one electron transport chain molecule to the next, falling closer and closer to the nucleus of the last electron acceptor.Where do the electrons for the ETC come from?NADH and FADH2 which got theirs from glucose.What molecule is the final acceptor of the electron?Oxygen, from splitting O2 molecule & grabbing 2 H+ .What’s consumed during this process?O2What’s gained by this process?H+ inside the inner membrane space
61 FADH2 enters the ETC at a lower free energy level than the NADH. Results in FADH2 produces 2 ATP’s to NADH’s 3Oxygen is the final electron acceptorThe electrons + oxygen + 2 hydrogen ions = H2OImportant to note that low amounts of energy is lost at each exchange along the ETC.
62 The Energy-Coupling Mechanism Chemiosmosis:The Energy-Coupling MechanismINTERMEMBRANE SPACEH+P i+ADPATPA rotor within the membrane spins clockwise when H+ flows past it down the H+ gradient.A stator anchored in the membrane holds the knob stationary.A rod (for “stalk”) extending into the knob also spins, activating catalytic sites in the knob.Three catalytic sites in the stationary knob join inorganicPhosphate to ADP to make ATP.MITOCHONDRIAL MATRIXFigure 9.14ATP synthaseIs the enzyme that actually makes ATP32-34 ATP
63 Electron transport chain Oxidative phosphorylation and chemiosmosisGlycolysisATPInnerMitochondrialmembraneH+P iProtein complexof electroncarnersCyt cIIIIIIIV(Carrying electronsfrom, food)NADH+FADH2NAD+FAD+2 H+ + 1/2 O2H2OADP +Electron transport chainElectron transport and pumping of protons (H+),which create an H+ gradient across the membraneChemiosmosisATP synthesis powered by the flowOf H+ back across the membranesynthaseQOxidative phosphorylationIntermembranespacemitochondrialmatrixFigure 9.15
64 Is cellular respiration endergonic or exergonic? exergonic Is it a catabolic or anabolic process?catabolicIf one ATP molecule holds 7.3kcal of potential energy, how much potential energy does 1 glucose molecule produce in cell respiration?One molecule of glucose actually contains 686 kcal/mol of potential energy. Where does the remaining energy go when glucose is reduced?What is the net efficiency of cell respiration if glucose contains 686kcal and only 277.4kcal are produced?At its maximum output, 38 x 7.3kcal = 277.4kcalIt’s lost as heat-which is why our bodies are warm right now.277.4/ 686 x 100 = 40% energy recovered from aerobic respiration
65 OCCURS IN CYTOSOLOCCURS IN MITOCHONDRIAOCCURS IN CYTOSOL
66 Anaerobic Respiration Fermentation enables some cells to produce ATP without the use of oxygenGlycolysisCan produce ATP with or without oxygen, in aerobic or anaerobic conditionsCouples with fermentation to produce ATP
67 Anaerobic Respiration Fermentation consists ofGlycolysis plus reactions that regenerate NAD+, which can be reused by glyocolysisAlcohol fermentationPyruvate is converted to ethanol in two steps, one of which releases CO2Lactic acid fermentationPyruvate is reduced directly to NADH to form lactate as a waste product
68 Stage 2: If oxygen is absent- Fermentation -Produces organic molecules, including alcohol and lactic acid, and it occurs in the absence of oxygen.Cells not getting enough oxygen, excess pyruvate molecules are converted into lactic acid molecules, raising the pH in the cells.Yeast uses alcoholic fermentation for ATP generation.
70 Animal and plant cellsHave cell junctions that directly connect the cytoplasm of adjacent cellsPlasma membranesPlasmodesmatabetween plant cellsGap junctionsbetween animal cellsFigure 11.3(a) Cell junctions. Both animals and plants have cell junctions that allow moleculesto pass readily between adjacent cells without crossing plasma membranes.
71 In local signaling, animal cells May communicate via direct contactEX: immune system & embryonic development(b) Cell-cell recognition. Two cells in an animal may communicate by interactionbetween molecules protruding from their surfaces.
72 Cell to Cell Communication (no distance; passing a note)
73 Cell to Cell Communication (short distance…on the board message) NeuronsLocal regulator = neurotransmitters
74 diffuses across synapse In other cases, animal cellsCommunicate using local regulators(a) Paracrine signaling. A secreting cell acts on nearby target cells by discharging molecules of a local regulator (a growth factor, for example) into the extracellular fluid.(b) Synaptic signaling. A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell.Local regulatordiffuses throughextracellular fluidTarget cellSecretoryvesicleElectrical signalalong nerve celltriggers release ofneurotransmitterNeurotransmitterdiffuses across synapseis stimulatedLocal signalingGrowth factorsNeurotransmitters
75 Cell to Cell Communication (long distance; hit a lot of cells…advertisement in local paper) Message gets sent to a lot of different cells. Some will act on it and some won’t.The ones that do act may not all act in the same way.
76 Long-distance signaling In long-distance signalingBoth plants and animals use hormonesHormone travelsin bloodstreamto target cells(c) Hormonal signaling. Specialized endocrine cells secrete hormones into body fluids, often the blood Hormones may reach virtually all body cells.Long-distance signalingBloodvesselTargetcellEndocrine cellHormonal signalingAKA: endocrine signaling
77 Plant hormonesSometimes travel through vessels but more often travel through the air as gas (ethylene).
78 What are theses types of signals? Are they short/local or long distance? Are they specific or general?Paracrine signalingSynaptic signalingHormonal signalingShort/local & generalShort/local and specificLong distance and general or specific
79 The Stages of Cell Signaling: A Preview Earl W. SutherlandEstablished that epinephrine causes glycogen breakdown without passing through the membrane.Discovered how the hormone epinephrine acts on cellsSutherland suggested that cells receiving signals went through three processesReceptionTransductionResponse
80 Reception- target cells detection of a signaling molecule (ligand) that binds to a receptor protein, causing it to change shapeTransduction-several steps where each molecule brings about a change in the next moleculeResponse occurs with the last molecule in the transduction pathway & triggers the cell’s response.
81 Plants have cellular receptors That they use to detect important changes in their environmentFor a stimulus to elicit a responseCertain cells must have an appropriate receptor
82 The potato’s response to light Is an example of cell-signal processingFigure 39.3CELLWALLCYTOPLASM 1 Reception2 Transduction3 ResponseReceptorRelay moleculesActivationof cellularresponsesHormone orenvironmentalstimulusPlasma membrane
83 Other Type of Intracellular Receptors Are cytoplasmic or nuclear proteinsSignal molecules that are small or hydrophobicAnd can readily cross the plasma membrane use these receptorsLike undercover cops hidden in a crowd
84 Receptor tyrosine kinases (insulin uses these) Can trigger more than 1 signal transduction pathway-coordinates many aspects of cell growth & reproduction-abnormal tyrosine receptors (function w/o signal molecules) may contribute to some cancers.Signal moleculeSignal-binding siteaCYTOPLASMTyrosinesSignal moleculeHelix in theMembraneTyrDimerReceptor tyrosine kinase proteins (inactive monomers)PCellular response 1Inactive relay proteinsActivated relay proteinsCellular response 2Activated tyrosine-kinase regions(unphosphorylateddimer)Fully activated receptortyrosine-kinase(phosphorylated6 ATP ADPFigure 11.7Kinase is an enzyme that catalyzes the transfer of phosphate groupsLike a friend who brings together 2 people who otherwise don’t hang out (unless it’s with this friend); the 3 have a greater time whenever they are together.
85 SIGNAL TRANSDUCTION PATHWAYS A phosphorylation cascade Signal moleculeActiveproteinkinase123Inactiveprotein kinaseCellularresponseReceptorPATPADPPPActivated relaymoleculeiPhosphorylation cascadeP Like flipping the switch of a mechanical toy which goes full speed when it is turned on and is completely still when turned off.A relay moleculeactivates protein kinase 1.12Active protein kinase 1transfers a phosphate from ATPto an inactive molecule ofprotein kinase 2, thus activatingthis second kinase.Active protein kinase 2then catalyzes the phos-phorylation (and activation) ofprotein kinase 3.3Enzymes called proteinphosphatases (PP)catalyze the removal ofthe phosphate groupsfrom the proteins,making them inactiveand available for reuse.5Finally, active proteinkinase 3 phosphorylates aprotein (pink) that bringsabout the cell’s response tothe signal.4
86 TransductionChanging the chemical message outside the cell to a message inside the cell.Inactive until g-protein attachesConverts ATP into cAMPHas regulatory factors and catalytic factorscAMP attaches & breaks regulatory factors away & catalytic factors become energized with the help of ATP (phosphorylation)ResponseActivate phosphorylase to breakdown glycogen into glucose in liver cells & muscle cells.
87 How long does it last?The cAMP boost does not last without another surge of epinephrine.If there is no epinephrine another enzyme, phosphodiesterase, converts cAMP to AMP.Like the trigger on a water gun, each time the trigger is pulled the reaction is immediate and temporary; cAMP is produced each time there is a cell signal stimulant (such as epinephrine) but the cAMP does not stay present long.
88 Maintaining blood glucose levels. WHAT INSULIN DOES…Feedback inhibition (negative)
90 What mechanisms drive molecules across the membrane? Passive TransportDiffusionOsmosisFacilitated diffusionActive TransportSodium Potassium Pump/Electrogenic pumpCotransportExocytosisEndocytosis
91 Solutions of Osmosis HYPERTONIC: Has a higher solute concentration and a lower water potential compared to the solution on the other side of the membrane.HYPOTONIC:Has a lower solute concentration and a higher water potential than the solution on the other side of the membraneISOTONIC:Have equal water potentials
92 Turgor Pressure most plant cells live in hypotonic environment water moves into cells, pushing cell membrane against cell wallcell wall is strong enough to resist pressurepressure from the water is called turgor pressure
93 Plasmolysis plant cells in hypertonic environment water leaves cells cell membrane moves away from cell wallloss of turgor pressure (wilting in plants)
95 MOVE CHARGED POLAR MOLECULES ACROSS MEMBRANE FACILITATED DIFFUSIONCHANNEL PROTEINEX: aquaporinsHydrophillic passagewayMOVE CHARGED POLAR MOLECULES ACROSS MEMBRANECARRIER PROTEINEX: Cysteine transporter
96 WHICH MEMBRANE PROTEINS ARE USED? ACTIVE TRANSPORTWhere free energy (often provided by ATP) is used by proteins embedded in the membrane to “move” molecules &/or ions across the membrane & to establish or maintain concentration gradients.Membrane proteins are necessaryWHICH MEMBRANE PROTEINS ARE USED?CARRIER PROTEINS
97 SODIUM-POTASSIUM PUMP AN EXAMPLE OF ACTIVE TRANSPORTSODIUM-POTASSIUM PUMPContributes to the membrane potentialPumps 3 Na+ out of cell for every 2 K+.Creates a positive charge from cytoplasm to extracellular fluid.Stores energy in the form of voltageMajor electrogenic pump of animalsProton pump for plants, fungi, & bacteria.
98 What is a nerve impulse?Nerve impulse is misleading. We will call it an action potential insteadCan be measured in the same way as electricity is measuredVoltageMillivoltsThe conductor of a neuron is the axonIs covered by a myelin sheathIncreases the rate at which an action potential passes down an axon.
99 Resting potentialArea of a neuron that is ready to send an action potential but is not currently sending one.This area is considered polarizedCharacterized by the active transport of sodium ions (Na+ ) out of the axon cell & potassium ions (K+) into the cytoplasm.There are negatively charged ions permanently located in the cytoplasmThis collection of charged ions leads to a net positive charge outside the axon membrane & negative charge inside.
100 Action PotentialDescribed as a self-propagating wave of ion movements in and out of the neuron membraneThis is the diffusion of the Na+ & the K+ .Sodium channels open & then potassium ones do to.This is the “impulse” or action potentialIt is a nearly instantaneous event occurring in one area of the axon = depolarizationThis area initiates the next area on the axon to open up the channels.This action continues down the axon.Once an impulse is started at the dendrite end that action potential will self-propagate itself to the far axon end of the cell.
102 Return to Resting Potential Remember that one neuron may send dozens of action potentials in a very short period of time.Once an area of the axon sends an action potential it cannot send another until the Na+ & K+ have been restored to their positions at the resting potential.Active transport is required to move the ions = repolarizationThe time it takes for a neuron to send an action potential & then repolarize is called: the refractory period of that neuron.
104 So… what causes diffusion of ions? Electrochemical gradientElectrical forceConcentration gradientEX: Na+ concentration inside a resting nerve is much lower than the concentration outside it.When the cell is stimulated gated channels open & Na+ “fall” down their electrochemical gradient driven by the concentration gradient of the Na+ & the attraction of the cations to the negative side of the membrane.
106 Villi of the small intestine Why is your small intestine infested with villi?
107 Function of villi Location of absorption of molecules All but the fatty acids are absorbed into thecapillaries.Fatty acids are absorbed into the lacteal.Lacteal is a vessel that is part of the lymphatic systemVilli are thin for easy absorption & has an abundance of capillaries and lymph vessels.All absorbed molecules are taken to body cells by the circulatory systemNutrient molecule can be used for energy (glucose) or as a component to build a larger molecule (amino acids).The process of building a bigger molecule is called: assimilation
108 Absorption vs Assimilation Absorption occurs when the food enters the body as the food molecules pass through a layer of cells and into the bodies tissues. This occurs in the small intestine which has many villi that are specialized for absorption.Assimilation occurs when the food molecules becomes part of the bodies tissue. Therefore, absorption is followed by assimilation.
109 The Human Heart “Pumps Your Blood” Valves close to prevent backflowvenulesarteriolesClosing of the valves produces the “lub dub” sound of you heartWhy is the muscle thicker at the left ventricle?
110 Where would you suppose the highest blood pressure is and why? The aorta because this is the first place blood travels from the heart pumping it out.Where would you suppose the lowest blood pressure is and why? Veins- this is the last area blood travels before entering the heart again. They have valves to prevent back flow
111 Control of your heart rate Hearts are made of muscle tissue; cardiac muscle.Contracts & relaxes = myogenic muscle contractionMass of tissue in the right atrium known as the sinoatrial node (SA node)Acts as a pacemaker by sending electrical signals for the artrias to contract (aka stimulate the myogenic contraction)2nd mass is known as the atrioventricular node (AV node)On a 0.1 second delay from the SA node in which it sends a signal for both ventricles to contract.
112 What happens during exercise? Increased demand for oxygen so heart beat speeds up.Also an increased build up of CO2 in the bloodstream.The medulla chemically senses the rise of CO2sends signal through the cardiac nerve to the SA node to increase your heart rateLater sends another signal to decrease heart rate through the vagus nerve
113 Adrenaline Chemical that is able to influence your heart rate. High stress times and times of excitement triggers the adrenal glands to release adrenaline into your bloodstream.The SA node “fires” more frequently causing an increase in your heart rate.
114 Pump, pump, pumps your blood. The right atrium's where the process begins, Where the C02 blood enters the heart Through the tricuspid valve to the right ventricle The pulmonary artery and lungs. Once inside the lungs it dumps its carbon dioxide And picks up its oxygen supply Then it's back to the heart through the pulmonary vein Through the atrium and left ventricle." "Pump, pump, pumps your blood."The aortic valve’s where the blood leaves the heart Then it's channeled to the rest of the bodThe arteries, arterioles, and capillaries too Bring the oxygenated blood to the cells The tissues and the cells trade off waste and CO2 Which is carried through the venules and the veins Through the larger vena cava to the atrium and lungs And we're back to where we started in the heart. Pump, pump, pump, pumps your blood