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Date Created: 09/08/14
EXAM 1 Animal Form and Function amp The Nervous System Adaptations heritable traits that allow individuals to survive and reproduce in a certain environment better than individuals that lack those traits 39239 If a mutant allele alters the size or shape of a structure in a way that makes it function more efficiently individuals who have that allele will produce more offspring than other individuals and the trait will increase in frequency in population over time TYPES of ADAPTATIONS 1 Behavioral group hunting in lions herding 2 Physiological polyandrous birds with sex role reversal female larger and defends territories while males incubate 3 Molecular ability to produce more hemoglobin at higher altitudes Tradeoffs inescapable compromises between traits 39239 Evidence side blotched lizard females can produce many small eggs or a few large eggs large eggs large offspring have greater chance of survival mothers that produce intermediate numbers of midsized offspring fittest Evolution change in frequency of adaptations traits in a population over time INDIVIDUALS DO NOT EVOLVE occurs within populations change in gene frequencies that code for those adaptations in a population over time selects for individuals that transmit the highest number of copies of their genes to the next generation Acclimatization phenotypic change in an individual during lifetime in response to short term changes in the environment Only a genetic change in a population in repose to natural selection based on environment acclimate by increasing hemoglobin levels adaptation is the ability to be able to do this Adaptive structures found in an animal if it helps the individual survive and produce offspring structures size shape or composition correlates closely with its function Homeostasis maintenance of relatively constant chemical and physical conditions in an animals cells tissues and organs 1 Conformational Homeostasis body temperature remains constant because it conforms to temp of the external environment 2 Regulatory Homeostasis adjust the internal state to keep it within limits that can be tolerated no matter what the external conditions ex panting or shivering regulatory systems monitoring internal conditions temperature blood pressure blood pH blood glucose Regulation and Feedback 39239 Epithelial cells are responsible for forming the internal environment and for maintaining physical and chemical conditions inside animal that are relatively constant 39239 Homeostasis is based on three general components and requires a set point 1 Sensor structure that senses some aspect of external or internal environment 2 Integrator evaluates the incoming sensory info and decides whether response is necessary 3 Effector any structure that helps restore desired internal condition based on negative feedback loop 39239 Negative feedback occurs when regulatory system makes a change in the opposite direction to a change in internal conditions O 90 O 90 Generalized overview of homeostasis External stimuli Perceives magnitude Negative feedback of a parameter EFFECTOR INTEGRATOR Changes parameter Compares sensor input to return it to with set point then set point instructs effectors Thermoregulate control body temperature varies by how animals obtain heat and whether the body temp is held at constant 1 Endotherm produces adequate heat to warms its own tissues 2 Ectotherm relies on heat gained form the environment 3 Homeotherms keep their body temperature constant 4 Heterotherms allow body temperature to rise or fall depending on environmental conditions Importance of Thermoregulation TOO HOT macromolecules lose shape and cease to function tRNA s proteins excessive water loss and dehydration TOO COLD metabolic processes slowed enzyme reactions and energy production damage to structures from ice crystal formation EFFECTORS 1 IfTbody gt Tset dilate blood vessels of skin to increase blood ow amp increase heat loss stimulate sweat glands evaporate heat loss breathing via panting 2 IfTbody lt Tset constrict blood vessels ofskin to decrease blood ow amp decrease heat loss muscle shivering generates heat stimulate cellular respiration to generate metabolic heat TRADEOFFS ENDO THERM Y vs ECTO THERM Y Endotherms enzymes at optimal temperatures at all times remain active in winter and night high levels of aerobic activities running ying must obtain large quantities of energy rich food Ectotherms able to thrive with low food intake more energy goes into reproduction muscular and activity slow down as body temperature decreases more vulnerable to predation in cold weather Adaptations for temperature regulation 1 Biochemical Conformational stability in proteins and macromolecules Heat stress proteins Amino acid substitution in proteins Icefish 2 Physiological brown fat metabolism shivering sweating 3 Behavioral feather uffing tail shading moving into microenvironments water seeking 3 Organisms climate envelope 1 Temperature 2 Precipitation 3 Seasonality Atomic and molecular levels Membrane protein in nerve cells admits a flow of ions Organism level Systems work together to support life Cellular level 4 Electric signal mediated by ion flows travels down length of neuron quot E 5 U Tissue level p1A ax 1 l Electric signals travel from cell to 0 cell in nervous tissue Organ level Nervous tissue and connective tissue in brain aid in sight smell memory and thought System level Nervous system controls breathing digestion movement and other functions Figure 416 Biological Science 2e 2005 Pearson Prentice Hall Inc O 1 ll llllmlm Atomic and molecular levels Membrane protein in nerve cells admits a flow of ions I YQQ algal I la Cellular level Electric signal mediated by ion flows travels down length of neuron Figure 416 part1 Biological Science 2le 2005 Pearson Prentice Hall Inc Cellular level Electric signal mediated by ion flows travels down length of neuron Tissue level Electric signals travel from cell to cell in nervous tissue Figure 416 part 2 Biological Science 2e 2005 Pearson Prentice Hall Inc Tissue level Electric signals travel from cell to cell in nervous tissue Organ level Nervous tissue and connective tissue in brain aid in sight smell memory and thought Figure 416 part 3 Biolo 39 I Science 2e 2005 Pearson Prentice I Inc Organ level Nervous tissue and connective tissue in brain aid in sight smell memory and thought System level Nervous system controls breathing digestion movement and other functions Figure 416 part 4 Biological Science 2e 2005 Pearson Prentice Hall Inc THE NERVOUS SYSTEM Sensing Integrating Acting Sensory input Sensory receptor 1599quot 313 Brain and spinal cord J J Effector v v Peripheral nervous Central nervous system PNS system CNS Copyrlght Pearson Education Inc publlshlng as Benjamin Cummings Sensory neurons Cell body of sensory Gray Sensory stretch receptors neuron in dorsal mane root gang on Quadriceps muscles extensors lnterneurons xx O C I27 Flexor lg muscles 39 Spinal cord Motor neurons cmss se t39 quot serving quadriceps sensory neuron Q Motor neuron Q lnterneuron Copyrlghl Pearson Education Inc publlshlng as Benjamin Cummings DENDRITE 9 CELL BODY 9 AXON HILLOCK 9 AXON Neuron functional unit of nervous system transmit electrical signals produced by changes in permeability of cell39s plasma membrane to ions Dendrites short branches from the cell body that transmit electrical signals and info from other neurons Cell body contains nucleus and organelles Axons nerve impulses that propagate along a single axon away from the cell body Axon Hillock where the axon joins the cell body transmission and integration of nerve signals Synaptic terminal nerve ending that relays signals via neurotransmitters to next neuron Synapse place where synaptic terminals of neuron come into contact with another neuron Peripheral Nervous System PNS all neurons and components of the nervous system that are outside CNS Nerve signals 39239 Electrical within a neuron 9 all membranes have electrical potential caused by differences between ion concentration inside and outside the cell 39239 Chemical between neurons Membrane Potential 39239 Inside Cell mostly potassium K some Sodium Na lots of impermeable macromolecules with negative charge sulfates phosphates resting membrane potential 39239 Outside Cell mostly Na less K lots of Cl resting membrane potential Ions cannot dissolve in lipids but the cell membrane is made of lipids 1 Ungated ion channels 2 Ion pumps 3 Gated ion channels active and change shape 4 PassiveDiffusion Diffusion of ions follows CHEMICAL and ELECTRICAL GRADIENT 39239 if diffusion were left unregulated 9 equilibrium concentration of ions that resulted in lower membrane potential regulated by sodium potassium pump 39239 Sodiumpotassium pump uses energy to pump ions against chemical amp electrical gradient uses ATP Action Potential amp Movement of Ions Across Cell Membrane 39239 All cells have membrane potential 39239 Neurons modulate membrane potential via voltagegated ion channels 39239 Change in membrane potential associated w action potential is caused by a change in concentrations of ions inside the cell 39239 Voltage gated ion channels controls the changes in membrane potential associated w action potential Na fast opening gate amp slow closing gate K slow opening gate once channels open ions follow chemical amp electrical gradient 39239 Tetrodoxin poison that is 100x more lethal than cyanide and blocks the voltagegated sodium channel Have tetrodoxin fish frogs newts snails octopus crabs get it from diet bacteria evolved different voltagegated sodium ion channels 39239 Tetrodoxin immunity small random changes in shape of ion channel to keep toxin from blocking channel individuals w changed ion channels have higher probability of surviving to pass change on 39239 Myelination membranes made of lipids process of axons being enveloped in myelin sheaths lipids are poor conductors of electricity prevents ions from leaking across the membrane allows electrical signals to move faster 39239 Node of Ranvier unmyelineated section of axon that causes the action potential to stop dense concentration of voltage gated Na channels O V Saltatory conduction in myelinated neurons only unmyelinated regions of the axon depolarize impulse moves faster than in unmyelinated neurons Schwann cell Depolarized region node of Ranvier Copyrighl z Pearson Education Inc publlshlng as Benfamin Cummings O V Multiple Sclerosis MS damage to the myelin and impairs electrical signaling causing muscles and coordination to weaken TCells attack Myelin healthy Nerve Cell Fibre Multiple Sclerosis V In ux of Na causes the action potential to begin and propagate down the axons because Na depolarizes adjacent parts of membrane V Glial Cells supporting cells 1 Astrocytes structural metabolic glucose blood brain barrier neurotransmitter regulation extracellular ion concentration regulation 2 Oligodendrocytes provide myelination in CNS 3 Shwann cells form myelin sheaths in PNS STAGES OF ACTION POTENTIAL 1 Resting State both Na and K channels are closed 2 Threshold stimulus opens some Na channels occurs when graded potentials sum to 55mV if in ux of Na achieves threshold then more channels are open triggers action potential axons only 3 Depolarization phase activation gates of sodium channels are open K channels are closed Na rushes into cell making inside of cell more positive positive feedback occurs with opening of Na channels and leads to more open Na channels refractory once Na channels open and close they are less likely to open for a short period 4 Repolarization phase Inactivation gates close Na channels K channels open K leaves the cell 9 inside of cell more negative sodium potassium pump and leak channels always working 5 Undershoot both gates of Na channels are closed K channels remain open because of slow closing gates 6 Back to resting state N I iffirui fi iiifi timfi A Inactivation gate 9 Depolarization phase 0 Repoafizing phase Of the 3W0quot l30t9quotti339 of the action potential 50 Action potential Activation sate VI 4 9 Resting potential 6 139ime 3eJsd cquot39 H H H H Plasma 9 9 Tnresrgoid 50 potential Membrane potential 9 inside Sodium cequot channel 0 Resting state Copyright 3 Pezuson Education inc publishing as Bengamm Cummings Presynaptic Cell Action potential in presynaptic cell Depolarization of presynaptic membrane Voltage gated calcium channels open In ux of calcium ions Synaptic vesicles storage sites for neurotransmitters fuse with presynaptic membrane Neurotransmitter is released from vesicles by exocytosis Synaptic Cleft gap between cells 0 Neurotransmitter diffuses across synaptic cleft in response to increased calcium concentration 39339 NT removed from synaptic cleft Postsynaptic Cell 0 Neurotransmitters bind to receptors in membrane 39 Ion channels coupled to the receptor open Membrane potential chances excitatory change can be depolarizing inhibitory change can be hyperpolarizing at Excitatory postsynaptic potential EPSP electrical change in postsynaptic neuron resulting from binding of neurotransmitter to the receptor opens gated channels that allow Na to enter and K to exit make action potentials more likely at Inhibitory postsynaptic potential IPSP electrical change in postsynaptic neuron resulting from binding of neurotransmitter to receptor opens gated channels that allow Cl to enter and K to exit in postsynaptic cell hyperpolarizes postsynaptic membrane action potential less likely make membrane potential more negative 6 0 90 0 90 0 90 0 90 0 90 0 90 9 9 0 90 0 90 Neural integration neurons react to multiple sources of information Ligand molecule that binds to a specific site on a receptor molecule neurotransmitters Ligand gated ion channels channel proteins that open in response to binding by a specific ligand NT binds to ligand gated ion channel in postsynaptic membrane channel opens and allows ow of ions NT chemical signal changes to electrical and causes change in membrane potential TYPES OF SYNAPSES 9 Neuron to neuron Neuromuscular Neuron to Gland 0 90 0 90 9 9 9 Excitatory Synapse Synaptic terminals Dendrites of of presynaptic neurons postsynaptic 0 neuron m 4quot v i Cell body of postsynaptic neuron Axon hillock M0quot 0 postsynaptic neuron Terminal i branches f m quot V O Excitatory synapse presynapuc 0 Inhibitory synapse 3 neurons Copynghl 0 Pearson Educalion Inc publishing as Beniamin Cummings Inhibitory Synapse Synaptic terminals Dendrites of of presynaptic neurons L postsynaptic neuron 9 Cell body of postsynaptic postsynaptic neuron Terminal h f if gizgcnzst quot I 0 Exeitatory synapse 8 neurons 0 Inhibitory synapse Copyright 0 Pearson Education Inc publishing as Benjamin Cummings
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