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emma_royal
Mind Map by , created more than 1 year ago

Mind map detailing key points on Section 1 of the OCR Complete Revision Course

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emma_royal
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Biology F214: Section1Communication and HomeostasisNervous SystemEndocrine SystemCommunicationReceptors and EffectorsResponding to the EnvironmentTo aid survivalmake sure conditions are optimal for metabolismAny change to the internal or external environment (e.g. temperature, lightintensity or pressure is called a stimulusReceptors are specific - e.g. pressure, light, glucose conc. therefore there aremany different types of receptor, some are on the CSM and some are whole cellsEffectors are cells that bring abouta response to produce an effect.These include muscle or cells from inglandsCell signallingBoth nervous and hormonalWays in which cells communicate with each otherTypes of NeuronMotor NeuroneSensory NeuronsShort dendritesOne long dendron tocarry impulses fromreceptor cells to the cellbodyShort axon that carries impulses fromthe cell body to the CNSShort dendrites (CNS to Cell Body)One long axon (Cell Body to Effector cells)Sensory ReceptorsAct as transducers (they convert one form of energy intoanother)Resting PotentialResting state, the inside of the cell is -ve so there is a p.d. acrossthe membrane. This is maintained by ion pumps and ionchannelsGenerator PotentialChange due to a stimulusDue to the cell membrane becoming excitedand more permeable, makes the inside of thecell more +veThe bigger the stimulus the bigger the generator potentialAction PotentialIf the g.p. is big enough it'll trigger an a.p. (threshold level)The Nervous Impulser.p. => -70mVSodium (3 x Na+) and Potassium (2 x K+)Use active transport to move Na+ out for K+into cellElectrochemical GradientPotassium channels alsoexist that allow K+ to moveout by facilitated diffusionAction PotentialSTIMULUS - Sodium channels open, neurone becomes less negativeDEPOLARISATION - p.d. reaches threshold (-55mV), voltagegated channels open so more sodium ions move in.REPOLARISATION - At +30mV, the sodium ion channels close andthe potassium channels open. Neurone becomes more negative.HYPERPOLARISTION - Overshoot, P.d. becomesmore -ve than resting potentialn (less than -70mV)R.P. - ion channels are resetRefractory period - too negativeto become excited agian, makesa time delay, also it means theimpulse can't travel backwardsWaves of DepolaristionMexican wave of sodium channels opening. Theimpulse propagates along the neuron, movement ofaction potentialAll-or-nothingThe stimulus must reach the threshold to becomean active action potentialThe bigger the stimulus themore frequent the impulsesSpeed of conductionSaltatory conduction, caused by the impulsejumping between nodes of Ranvier (betweenmyelin sheaths made of Schwann cells)Faster if - big axon diameter or a highertemperature (until 40 degrees as enzymeswill denature in the cells)SynapsesNeurotransmitters are removed from thesynaptic cleft so the response doesn't keephappening, they're taken back to thepre-synaptic cleft, or they are broken downExample: Cholinergenic SynapseNeurotransmitter: Acetylcholine1. ARRIVAL OF ACTION POTENTIALArrives as impulse at the presynaptic knob, this stimulates voltage-gated calcium ionchannels. They diffuse in and are actively transported out.2. FUSION OF VESICLESCa+ causes vesicles containing acetylcholine to fuse with the presynaptic membrane3. DIFFUSION OF AChACh diffuses across the cleft and binds to the specific cholinergic receptors on the postsynapticmembrane. This causes sodium ion channels in the postsynaptic neurone to open, which causesdepolarisation. An action potential is generated if the threshold is reached.ACh is removed by acetylcholinerase (AchE) and the productsare reabsorbed by the presynaptic neurone to make more AChDisruption of synaptic transmissionRoles of synapsesSame shape as neurotransmittersNicotineAGONISTSBlock receptorsMuscle can't be stimulated, paralysis.Inhibit breakdown enzymeMore neurotransmitters in the synaptic cleft tobind to receptors and they're there for longerLoss of nerve controlInhibit the release of neurotransmittersFewer receptors are activatedBlock the calcium channels in the presynapticknob, meaning fewer vesicles fuse with themembraneDivergenceOne neuron is connected to many neurones, thereforeinformation can be dispersed to different areas of the bodyConvergenceAmplificationSpatial summationMultiple synapses that together surpass the threshold potentionTemporal SummantionTwo or more nerve impulses arrive in quicksuccession from the same presynaptic neuronUnidirectionalThe presense of a pre and postsynaptic neuron meansthe impulse can only travel in one directionHormonal CommunicationInformation via chemical signals (hormones) that are secreted by glands. Manyproteins are peptides e.g. insulin, however some are steriods, e.g. progesteroneGlands can be stimulated by a change in concentration ofa specific substance or by electical impulseDiffuse directly in the blood, binds to specific receptors on target cells.Tissues that contain a lot of target cells are kknown as target tissuesGlandsendocrine - secrete hormones directly into the bloodexocrine - secrete chemicals through ductsAction of HormonesHormones are first messengers, fromthe endocrine gland to the receptorCatalyses the action of a secondmessenger inside the cellSecond messengers activate a cascade inside the cellAdrenalineAdrenal GlandRelease when there is low concentration of glucose in the blood, when stressed and when exercisingActivates glycogenolysis(As a first messenger) Adrenaline binds to receptors on many cells like liver cellsIt then activates an enzyme in the membrane that activates the second messenger called cAMPcAMP activates a cascade (that makes glucose more available to the cell)Cortisol /AdrenalinThe PancreasIslets of LangerhanAlpha cellsBeta cellsGlucagonInsulinEndocrine FunctionExocrine FunctionMakes up most of the pancreasAcinar cellsSecrete digestive enzymes into the pancreatic ductHomeostasisThe maintenance of a constant internal environmentKeeping your internal environmentroughly constant (within limits)TemperatureAs the rate of metabolic reactions increases (so does thekinetic energy) the temperature's increases in turnToo hot and enzymes will denature, to low and theenzyme activity will be reduced/Negative feedbackInvolves receptors, a communication system and effectorsThe receptors detect change and theeffectors counteract the changeOnly works within certain limits, always in fluxPostive feedbackAmplifies the changeE.g. cervical dilation or platelets to form a clotTemperatureEctothermsRelies on external temperature, also more active at higher temperatureEndothermsControl body temperature using internal homeostasisConstantly have a high metabolic rateCan constantly be active at any temperatureMechanismsTo reduce temperatureSweating, hairs lie flat, vasodilationTo increase temperatureShivering, hormones, much less sweat, hairs stand up, vasoconstrictionUses the hypothalamus and thermoreceptorsBlood ConcentrationIncreases the permeability of cell membranesto glucose and activates glycogenesisBinds receptors onto the cellmembranes of liver cells (torelease glycogen) and activesglycogenolysis (breaks downglycogen) and gluconeogenesis)LowHighDiabetes MellitusInsulin from GM bacteria(rather than from a pigs pancreas) Cheaper, more produced,human so less likely to trigger an allergic response or berejected, ethical reasons such as religion or vegetarianism.Could possibly cure with differentiated stem cellsStructure of the Nervous SystemCNSPeripheral NSSomatic NS (conscious activities)Autonomic NS (unconscious activities)Sympathetic NS (fight or flight)Parasympathetic NS (rest and digest)Example: Heart RateHigh Blood PressureImpulses sent to m. oblongata which sends impulses alongPARASYMPATHETIC neurones. ACETYLCHOLINE binds to SANLow Blood PressureBaroreceptors detect. Impulses sent to m. oblongata which sendsimpulses along SYMPATHETIC neurones.NORADRENALINE binds to SANHeart rate decreasesHeart rate increasesHigh Blood O2, Low CO2 or high blood pHChemoreceptors detectBaroreceptors detectLow Blood O2, High CO2 or high blood pHChemoreceptors detectAdrenalineWhen an organism is threatened, adrenaline is released, it binds to specificreceptors on the heart to increase contraction frequency and strengthDouble click this nodeto edit the textClick and drag this buttonto create a new node