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Lecture 41

BIOL 1115 Lecture Notes - Lecture 41: Central Nervous System, Myelin, Axon Hillock

5 pages33 viewsSpring 2016

Course Code
BIOL 1115

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ch 41
Rhea Khilnani Sun Dec 11 07:33:04 PST 2016
Central Nervous System (CNS)
Brain and spinal cord
perpheral nervous system
all the nerves outside of the brain or spinal cord
Send and receive electrical and chemical signals to effector cells Effector cells
Cell body or soma
Contains nucleus and organelles
Extensions of cell body, single or branching Receive incoming signals
Extension of cell body Send signals to other cells Typically single May have branches and may be wrapped in myelin
Axon hillock
near cell body
Site of nerve impulse generation
Axon terminals
convey electrical or chemical signals to other cells Typically occur in bundles called nerves
Surround neurons and perform numerous functions
Metabolic support Form the blood-brain barrier
Participate in immune functions
Oligodendrocytes (CNS) and Schwann cells (PNS)
Produce myelin sheath
Sheath is interrupted by noninsulated nodes of Ranvier
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Sensory neurons
Detect information from:
outside world
internal body
Afferent neurons – transmit to CNS
Motor neurons
Send signals away from CNS to elicit response Efferent neurons
Connectors between neurons Interpreter neurons
Reflex arc
Stimulus from sensory neurons sent to CNS (spinal cord); signal interpreted in spinal cord and transmitted to motor neurons to elicit
response Quick and automatic response
Electrical Properties of Neurons andthe Resting Membrane Potential
The functions of the nervous system—sensation, integration, and response—depend on the functions of the neurons The basis for the
Action potential
Neurons communicate
because they possess an excitable membrane
excitable membranes generate signals
Plasma membrane
Regulates what enters and exits a cell Barrier that separates charges
Ions cannot pass through membrane without assistance
Require a transport channel
Transmembrane proteins – channel, carrier
Electrical Properties of Neurons
As with all cells the cell membrane of a neuron is polarized
Inside of cell is negative relative to the outside
Unequal distribution of ions  electrical potential difference
Voltmeter can be used to measure the electrical potential difference across the membrane
Membrane potential
Resting membrane potential
Polarized membranes exhibit a resting membrane potential
Occurs when a cell is not being stimulated or conducting impulses (resting)
-70 millivolts
Degree of polarization
Changes in membrane potential are changes in degree of polarization
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