Biology 106 Notes Week 13
Biology 106 Notes Week 13 Biology 106- Organismal Biology
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This 7 page Class Notes was uploaded by Emma Silverman on Monday April 20, 2015. The Class Notes belongs to Biology 106- Organismal Biology at Washington State University taught by Dr. Cousins & Dr. Lee in Spring2015. Since its upload, it has received 78 views. For similar materials see Biology 106 in Biology at Washington State University.
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Date Created: 04/20/15
21315 My Low blood glucose causes alpha cells to release the hormone glucagon Glucogon stimulates the liver to break down glycogen releasing glucose Glucose homeostasis Example of use of aminoacid derived hormones insulin and glucagon are pep des Surface receptors on target cells Diabetes mellitus Greek copious urine honey Type autoimmune disorder cells of pancreas are targeted no ability to produce insulin usually occurs during childhood Type II 90 reduced responsiveness of target cells or insulin deficiency usually occurs after age 40 Stress and the adrenal aland Shortterm response Epinephrine adrenaline and norepinephrine Longterm response ACTH and corticosteroids Some effects of epinephrine and norepinephrine Glycogen broken down to glucose Increased blood pressure breathing metabolic rate Corticosteroids mineral and cluqo corticoids released by adrenal cortex Some effects increased blood volume and blood pressure breakdown of protein and fats Final thouqhts DO zebras exnerience stress Baboon studies Take blood samples measure corticosteroids Baboon troops social hierarchy alpha beta Alpha low stress beta high stress Wolf and mongoose studies Can measure hormones in feces and urine May be different Alphas have elevated levels all the time Kevwords reading Io 10221038 Nervous system functions Structure of a neuron Sensory motor inter neurons Membrane potential Sodium potassium ATPase Action potential Depolarization Hyperpolarization Voltage gated ion channels Action potential propagation Node of Ranvier Synapse Presynaptic cell Postsynaptic cell Signal transmission at chemical synapse Nervous System A combination of electrical and chemical signals How do the cells of the body produce electrical signals The membrane potential of living cells Membrane potential Living cells have an electrical potential across their membranes The inside of the cell is more negatively charged than the outside This difference in charge is caled the membrane potential Usually between 50 to 100 mV 41515 What is the basis for the membrane potential Two causes 1 differences in ionic composition of intracellular and extracellular fluid 2 selective permeability of the plasma membrane Ionic composition of intracellular and extracellular fluid Cation positively charged ions composition Intracellular fluid primary cation is K Na is low Extracellular fluid primary cation is Na K is low Ionic composition of intracellular and extracellular fluid Anion negatively charged ions composition Intracellular fluid proteins amino acids sulfate phosphate A Extracellular fluid Cl Recall that the membrane can have channels that allow facilitated diffusion to occur Cell membranes have many more K channels than Na channels What will happen to K Na Flow of K gtgt Na therefore net loss of positive charge from cell Gradient between extracellular and intracellular fluid favors loss of K from the cell Negatively charged ions will want to follow to balance the loss of charge but since the intracellular anions are large molecules like amino acids and proteins they cannot diffuse out This makes the inside of the cell more neqativelv charqed than the outside But there is also a gradient favoring the diffusion of Na into the cell from the outside This could prevent negative charge from building up inside but it doesn t Why not Two reasons Low Na permeability due to few open Na channels Sodiumpotassium ATPase Sodiumpotassium ATPase Active transport antiport Each pumping cycle pumps 3 Na out and 2 K in at the expense of 1 ATP Pumping positive charge outside the cell A net movement of one positive charge each time it does the cycle Effect on the membrane Reinforcing positive outside and negative inside Excitable cells Some cells figured out how to be excitable Most cells have a stable membrane potential of around 70 mV Excitable cells can generate changes in their membrane potentials Excitable cells include neurons and muscle cells Electricity is a way of synchronizing or sending a cell over long distances Electricity is best to synchronize In muscles and nerves Nervous svstems Functions sensory input gt integration gt motor output These functions overlap Example of overlapping function Sensory input visual signal involves peripheral nervous system Integration processing of signal by central nervous system in vertebrates brain and spinal cord Motor output muscular output involves peripheral nervous system Neurons the cells of the nervous svstem Structure of a neuron Cell body Dendrites input Axon output Structural diversitv of neurons Sensory neuron long axon with cell body connected to axon Motor neuron long axon with cell body connected to dendrites lnterneurons found in brain highly branched axons andor dendrites Neurons conduct electrical signals Very fast How do cells convey electrical signals Excitable cells Most cells have a stable membrane potential of around 70 mV Excitable cells can generate changes in their membrane potentials Excitable cells include neurons and muscle cells Action potential Excitable cells can change their membrane potential When signaling becomes more positive depolarization The depolarization is called an action potential The action potential is the basis for electrical signaling HVDerpolarization Threshold potential telling the cell to fire or not Polarization cell is polarized negative charge inside positive outside Making in more negative is hyperpolarization Depolarization If we have it going in a less negative direction it is depolarization Action Potential Action potentials occur because of voltage dated ion channels If the stimulating potential causes the membrane potential to rise about 1520 mV an action potential results This is due to the opening of voltage gated ion channels voltage gated channels open briefly then shut lnitiallv onlv Na channels Open Since there is a large concentration of Na outside the cell Na rushes in making the intracellular fluid less negatively charged This causes the peak of the action potential Voltaqe dated K channels also Open But they are much slower than Na channels They are fully open after the peak of the action potential K flows out of the cell and the membrane potential becomes negative again Tetrodotoxin Produced by pufferfish Blocks Na channels What would be the effect of ingesting tetrodotoxin Lee indicated this as a potential test question 41715 Pr0paqation of the action potential Action potential travels along the axon to the other end of the cell The speed of transmission can be as high as 100 meters per second or 225 mph Propagation is a series of new action potentials that travel along the axon Pr0paqation what happens at the level of the ion channels First action potential gives rise to a depolarization further along the axon Depolarization at second segment results in the opening of voltage gated Na channels and a second action potential occurs Second action potential triggers a third action potential etc High performance axons Faster signal conduction allows more rapid coordination between sensory input and motor output 2 ways to increase action potential transmission speed Increase axon diameter Nodes of Ranvier Nodes of Ranvier Axons of vertebrates are myelinated Insulating layer on axon results from Schwann cells Small gaps of exposed axon surface are present between Schwann cells Nodes of Ranvier Depolarization and action potential only occurs in the nodes Passive conduction of depolarization from node to node By jumping from node to node transmission is faster How do neurons communicate with other cells Cellcell communication occurs at synapses Examples Synapse between sensory receptor and sensory neuron Synapse between motor neuron and muscle cell Synapse between neurons Svnapse between neurons Transmitting cell presynaptic cell Receiving cell postsynaptic cell Two types of synapse Electrical Chemical Electrical svnapse Action potential electrical signal spreads directly Cytoplasm of the two neurons is joined by gap junctions Allows rapid transmission from neuron to neuron Chemical svnapse Narrow gap between the neurons called the synaptic cleft Action potential results in release of neurotransmitter by presynaptic cell Neurotransmitter causes depolarization of postsynaptic cell and can result in another action potential Chemical svnapse a closer look Depolarization at the synaptic terminal results in Ca influx Ca causes vesicles containing neurotransmitter to fuse with presynaptic membrane Neurotransmitter diffuses into synaptic cleft Neurotransmitter binds to ion channels on the post synaptic membrane What happens when neurotransmitter binds to ion channels on the post synaptic membrane lon channels open This results in either a depolarization or hyperpolarization inside becomes more negative Depolarization is stimulatory Hyperpolarization is inhibitory How do the channels close again Enzymatic degradation of the neurotransmitter Uptake of neurotransmitter by other neurons Clicker question Nerve gases like sarin and VX block that acetylcholinesterase that degrades ACh neurotransmitter lf nerve gas results in a Na channel stuck open the membrane potential would remain A 70mV B 50mV C OmV Nervous Svstems 2 Keywords Integration of synaptic signals Neurotransmitters Acetylcholine Norepinephrine Serotonin Dopamine Amino acid neurotransmitters Endorphins Nitric Oxide NO Neurotransmitters Acetylcholine ACh excitatory to vertebrate skeletal muscle other effects at other sites will see again with muscle motor control Bioqenic amine neurotransmitters Derived from amino acids Norepinephrine Dopamine Serotonin Usually function within the central nervous system