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Bio II Notes 3/3

by: Rocket

Bio II Notes 3/3 BIO 1144

GPA 4.0

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About this Document

Notes covering CNS and PNS system overview, neurons, and impuleses
Thomas Holder
Study Guide
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This 5 page Study Guide was uploaded by Rocket on Wednesday March 16, 2016. The Study Guide belongs to BIO 1144 at Mississippi State University taught by Thomas Holder in Spring 2016. Since its upload, it has received 24 views.


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Date Created: 03/16/16
Nervous System­ Ch. 41, 42, 43  +Closely tied with Sensory system  ❖ Central Nervous System (CNS)  ­Increase of size of brain relative to body size  (the more advanced the organism is)  and nervous system functions    ­CNS composed of Brain + Spinal Cord  ex.  Fish: 2:1        Reptiles: 25:1        Humans: 55:1    ➔ Peripheral Nervous System (PNS)  ­All neurons and projections outside of CNS   +Invertebrates  ­ simple system but difficult to distinguish between CNS and PNS    ❏ Neurons  ­Nerve cells which are the basic structural and functional units of Nervous systems  ­Found in all phyla except porifera   +Functions:  ­ Send and receive chemical and electrical signal   +Structure:  ­ Soma (cell body):  nucleus and regular organelles  ­ Dendrites: extensions of plasma membranes, incoming signals  ­ Axons:  extensions of plasma membranes, sending signals                      ★ Glial Cells  ­ More abundant in nervous tissue than neurons x1000 fold  ­ Provide support    + Myelin Sheath  ­ Allows for more efficient and insulation of impulses  ­Oligodendrocytes (CNS)  ­Schwann cell (PNS)    ­ Microglial cells: remove dead cells, cleaners  ­ Astrocytes: metabolic support, associated with nutrition of neurons  ­ Radial Glial Cell: layout pathway for neuron migration during embryonic development   *Last 2 groups often called “Stem cells” able to produce more glial and neuronal cells     3 Types of Neuron   + Sensory  ­ “Afferent” transmitting signals to CNS  + Motor   ­ “Efferent” carry signals away from CNS to elicit response   + Interneurons  ­ Interconnecting cells between other neurons     Reflex Arc  Involuntary Act:  Stimulus → Receptor (striking knee) → sensory and interneurons neurons send to → CNS→  motor neurons and interneurons carry response back → (received at flexor muscles) Effector→  Response     Electrical Properties  +Membrane Potential  ­ Gatekeeper, only neurons and muscles cells generate electrical signals  ­ Difference in charge between inside and outside   +Ion concentration and Electrical differences  ­ Provides concentration differences  ­ Cell considered “polarized”  ­ Ions will move through channels if open  ­ Different restrictions depending on chemical    +Resting Membrane Potential  ­When neurons are not sending signals  +Selectively Permeable to chemicals leading to difference in charge  ­ Cation (+)  ­ Anions (­)  ­Inside is more (­)             Combined together  ­Outside is more (+)            makes it polarized   +Anions inside drawn to cations on outside to edge                              3 Factor Contributing to Resting Membrane Potential  1. Sodium­Potassium Pump expenditure of ATP to pump molecules                3 Na +  pumped out for every   2 K + in        2.  Ion specific channels allows passive ion movement  ­ Works as long as channels are open  ­ Membrane is more permeable to K+  ­ K+ channels more frequently open at resting potential        3. More (­) charged ions are inside cell (polarity)    Electrochemical Gradient   ­ No net movement of molecules­ opposing forces of electro + chem can cause NEAR  equilibrium (equal charges no K+ flow)  ­ Ion movement (+) or (­)  ­ Chemical movement of K+ Na+ Cl­  ­ Imbalance normal created by inside and outside membrane    Neuron Signaling   ­ Changes in membrane potential, changes in degree of polarization  +Depolarization  ­ Membrane becomes less negative to surrounding solutions  ­ gated channels for Na + movement in so becomes more positive  ­ Membrane becomes less polarized  +Hyperpolarization  ­ membrane becomes more negative   ­ K+ moves out becoming less positive  ­ membrane becomes more polarized    *ALL cells exhibit membrane potential*  *ONLY neurons and muscles cells are “excitable”­ capacity to generate electrical signals  *Use of gated ion channels:  ­ Voltage­ gated: open/close in response to voltage charges  ­ Ligand (chemical) gated: open/close in response to chemicals    ● Nerve Impulse  Frequency: “language” higher frequency =  greater excitation  1. Resting Potential  ­ Imbalance between K+ and Na+   ­ Charge imbalance (gradient) between  inside and outside axon  +At rest → membrane selectively permeable  to K+      2. Action Potential “Electric potential” of  impulse  ­Rapid/brief change of nerve fiber  ­ “self­propagating”  ­ After passing membrane it quickly returns to resting positions  ­At a given point­ Na+ channels open  Na+ diffuses in  K+ diffuses out (due to electrical gradient changes)    3. Sodium/Potassium Pump  ­Complex of proteins in membrane  ­Pump out Na+    Both require   ­Carry in K+             ATP expenditure  ­ 3Na+ : 2K+      Impulse Conduction Rate  Conduction Rate:   +Variable  ­ Sea anemones: 0.1m/second  ­ Mammals: 120m/second  +Inverts  ­ Speed is directly related to axon diameter  +Vertebrates  ­ Speed related directly between axon diameter and layers around myelin sheath  ­ Myelin sheaths is in sections: Nodes of Ranvier  ­ Saltatory conduction: “jumping”      


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