Biology 1710 Animal Nervous Systems
Biology 1710 Animal Nervous Systems BIOS 1710
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This 4 page Class Notes was uploaded by Emily McKee on Saturday January 23, 2016. The Class Notes belongs to BIOS 1710 at Ohio University taught by Scott Moody in Fall 2015. Since its upload, it has received 189 views. For similar materials see Biological Sciences II: Ecology, Evolution, Animal Body Systems in Biological Sciences at Ohio University.
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Date Created: 01/23/16
Animal Nervous Systems Chapter 35 Highlight: Key Topics Bold words: Terms to know Nervous system-‐ network of many interconnected nerve cells (neurons) Nerve cells (neurons)-‐ basic functional units of the nervous system Ø Parts of a neuron: Ø Dendrites: receive stimuli and sends it to the cell body Ø Axon hillock: junction of nerve cell body and axon Ø Axon: transmits signals away from the cell body Ø Action potential: brief electrical signal transmitted from the cell body along one or more axon branches (+30mV) Ø Resting potential is -‐70mV Ø Synapse: junction where the axon terminal communicates with another cell Ø Synaptic cleft: space between the axon of the presynaptic cell and the neighboring postsynaptic cell Ø Neurotransmitter: molecule that transmits a chemical signal from the axon to the postsynaptic target cell Ø Sensory neurons Ø Receive & transmit information about the environment or internal physiological state Ø Interneurons Ø Process information received by sensory neurons and transmit it Ø Motor neurons Ø Receives information from interneurons and then produces a suitable response Ø How do two neurons communicate? Ø By using an electrical or chemical signal Ø Neurons are different shape and size due to their different functions Glial Cell-‐ surrounds neurons and provides them with nutrition and support Ø Schwann cell: insulates sensory and motor neurons by forming myelin sheaths Ø Myelin sheath: multiple lipid-‐rich layers formed by glial cells Ø Multiple Sclerosis is a disease where there is a problem with the myelin sheaths Ø Oligodendrocytes: insulates the brain and spinal cord by forming myelin sheaths Ø Astrocytes: surrounds blood vessels in the brain, limiting the size of compounds that can diffuse from blood to the brain Ø Known as the blood-‐brain barrier Membrane Potential-‐ charge difference between the inside & outside of a neuron due to a difference in charged ions (voltage) Ø Action potential: +30mV (for definition look under parts of a neuron) Ø Depolarization: Increase in membrane potential Ø Membrane potential becomes more positive Ø Voltage-‐gated Na channels open at the axon hillock Ø Closed at resting potential & open quickly when depolarization of the cell membrane occurs Ø If signal depolarizes the cell membrane to about 15mV above the resting potential then an action potential is fired at the axon hillock Ø Repolarization: Decrease in membrane potential + Ø Na channels become inactive (close) Ø K channels open and the K leave Ø Membrane potential becomes more negative Ø Hyperpolarization: When to many K leave the cell Ø Causes a refractory period Ø Nerve can’t fire another action potential Ø Causes action potential to only be sent DOWN an axon (directionality) Ø Cell membrane goes back to rest as K reenters the cell Ø Self-‐propagation: Doesn’t need help from an outside source Ø Action potential demonstrate this by how they moving down an axon Ø They open & close adjacent ion channels Ø Can not be generated where myelin sheaths are, so they jump over the sheaths Ø Resting potential: The negative voltage across a membrane at rest (-‐70mV) Ø K leak channels and Na /K pump help maintain resting potential + Ø There are more potassium (K ) ions inside the neuron, there are more sodium (Na ) & chloride (Cl ) ions on the outside of the neuron Ø The imbalance causes an electrical potential Ø Extracellular: Intercellular ratio Ø Na = 9:1 Ø K = 1:20 Ø Ca = 200:1 Synapse (look for definition under parts of a neuron) Ø Parts of a synapse: Ø Presynaptic cell Ø Synaptic cleft Ø Postsynaptic cell Ø Electrical synapse (gap junction) Ø Faster but less flexible compared to a chemical synapse Ø Ions can transfer back and forth (bidirectional) Ø Chemical Synapse Ø Slower but more flexible than an electrical synapse Ø More commonly used Ø Steps on how it works: Ø 1) Action potential arrives at presynaptic terminal Ø 2) Depolarization causes voltage-‐gated Ca channels open Ø 3) Ca causes synaptic vesicles to bind to the presynaptic cleft & neurotransmitters are released into the synaptic cleft Ø 4) Neurotransmitters bind to receptors on the postsynaptic membrane & postsynaptic ion channels open Ø 5) Neurotransmitters are absorbed by the glia or the presynaptic cell Neurotransmitters Ø Acetylcholine Ø Examples: Curare Ø Monoamines Ø Examples: Norepinephrine, Dopamine, & Serotonin Ø Peptides Ø Endorphins Ø Amino Acids Ø Glutamate § Has to deal with learning § Excitatory (an accelerator) Ø GABA § Inhibitory (an inhibitor) EPSP vs. IPSP Ø EPSP Ø Caused by the opening of glutamate receptors + Ø Na ions enter the cell Ø Triggers action potential if higher than the threshold Ø IPSP Ø Caused by GABA receptors Ø Inhibitory Ø Temporal summation Ø EPSP set off an action potential at the same time & location Ø Spatial summation Ø EPSP set off an action potential at the Same time but different location Ø Cancelation summation Ø EPSP & IPSP set off action potentials at the same time but different locations Vertebrate Nervous System Ø Central nervous system (CNS) Ø The brain & spinal cord Ø Peripheral nervous system (PNS) Ø Spinal nerves and other nerves Ø Made up of blood vessels, connective tissue & axons Ø Afferent division Ø Sends sensory info to the CNS Ø Sensory info not only comes from outside the body but also from inside Ø Example: Not seeing your hand behind you, but you know it is there and what it is doing Ø Efferent division Ø Carries commands from CNS to the body Ø Autonomic nervous system (ANS) Ø Parasympathetic Ø Relaxation Ø Sympathetic Ø Fight or Flight (adrenaline rush) Ø Both work together to maintain homeostasis Neuronal circuit responds to stimuli Ø Example: knee-‐jerk reflex
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