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BIOL 111 Lecture Notes - Internal Fertilization, Body Plan, Aposematism

Biology (Sci)
Course Code
BIOL 111

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Bio 111 Alanna Houston
October 25, 2007
-nervous tissue does not first appear in flatworms but in
-Dendrites – receive impulses
-Cell body – contains most organelles
-Axons – conduct impulses away from the cell body
-Axon terminals – synapse with other cells
Vertebrate Nervous System:
-Afferent neurons: bring sensory info to CNS
-Interneurons: in CNS store, integrate, and relay info
-Efferent Neurons: Bring motor info from CNS
Spinal Reflex Arc:
-Example: knee jerk reflex
-Involved: spinal cord (CNS) and 2 neurons (PNS)

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Bio 111 Alanna Houston
-There is a stimulus (rubber mallet on tendon) that hits a sensory
neuron (stretches dendrites) sending impulse up the sensory
neuron to the spinal cord. Impulse is transferred to motor neuron
and travels from spinal cord. This impulse triggers response in
effector and the lower leg extends.
-** A ganglion is a cluster of nerve cells
-Dendrites bring information to the cell body and axon brings it
away from the cell body
How do neurons work?
-Difference in charge across the cell (neuron) membrane and a
charge due to ions (Na+, K+, Cl-) and negatively charged proteins.
-Look at the neurons at rest slide:
oNa+ outside
oK+ inside and outside and Cl- and negatively charged
proteins inside
oElectrochemical gradient across the membrane
oVoltage difference = membrane potential
oVoltage difference when neuron is at rest…FINISH
-measuring membrane potentials:
oelectrodes inserted into axon
ocan chart electrical potential across membrane over course
of an impulse
ouse squid neurons (1 mm)
-Nerve impulse = action potential
oRapid voltage change (1 to 2 milliseconds)
o3 major processes:
depolarization (2,3)
depolarization (4)
Na+/k+ pump (all)

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Bio 111 Alanna Houston
Involve movement of Na+ and K+ FINISH
What controls ion movement?
-Ion channels and ion pumps (membrane proteins)
-Ion Channels:
oMay be gated (voltage or chemically)
oIons flow with gradient
oNo energy used (diffusion)
-Ion Pumps:
oSodium – potassium pump
oIons move against gradient
oUse energy (active transport)
-These proteins are selective: Na+, K+ etc only
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