pre14 - Mollusks & Neurons BIOL 111 Organismal Biology...

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1 1 Lecture 14 Mollusks: How does the nervous system work 20 October 2009 BIOL 111 – Organismal Biology 2 lecture outline 1. Neurons Structure/function Types Reflex arc Action potential Speed of transmission 2. Mollusks (Phylum Mollusca) body plans diversity 3 Nervous Systems nerve net ganglia nerves CNS PNS cnidarians Function: annelids mollusks vertebrates 4 Functional unit of the nervous system Neuron (nerve cell) axon dendrites axon terminals cell body dendrites – receive impulses cell body – contains most organelles a xons – conduct impulses a way from cell body axon terminals – synapse with other cell(s) 5 Vertebrate Nervous System brain spinal cord afferent neurons bring sensory info to CNS efferent neurons bring motor info from CNS interneurons in CNS store, integrate, and relay info = effectors = effectors Fig. 46.1 (8 th ed) 6 dorsal ventral Spinal Reflex Arc ex: knee-jerk reflex involved: spinal cord (CNS) +2 neurons (PNS) 1. stimulus 2. sensory stretch receptors trigger impulse ganglion 3. impulse travels to spinal cord via sensory neuron sensory neuron (afferent) motor neuron (efferent) 46.1 (8 th ed)
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2 7 dorsal ventral Spinal Reflex Arc motor neuron (efferent) ex: knee-jerk reflex involved: spinal cord (CNS) +2 neurons (PNS) 4. impulse transferred to motor neuron & travels from spinal cord 6. lower leg extends 5. impulse triggers response in effector 8 How do neurons work? ELECTROCHEMICALLY ELECTRO – difference in charge across the cell (neuron) membrane CHEMICAL – charge due to ions (Na + , K + , Cl - ) and negatively- charged proteins 9 Neuron at rest electrochemical gradient across the membrane • voltage difference = membrane potential Cl - — proteins — proteins Cl - K + • K +
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pre14 - Mollusks & Neurons BIOL 111 Organismal Biology...

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