BIOL 1140 Chapter Notes - Chapter 19: Highway, Midbrain, Cerebellum

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Human Biology Review Unit 19
Overview: Nervous system
Nervous systema network of cells that transmit and interpret signals to coordinate function of the
trillions of cells of the body
Central nervous system (CNS)receives, processes, stores, and transfers information
Consists of brain and spinal cord
Peripheral nervous system (PNS)consists of input and output subdivisions that transfer
signals to and from the CNS
Consists of all other nervous tissue not in brain and spinal cord
Nervous cells:
o Neuronscells that generate and conduct signals as a means of communication between
tissues of body
Axonlong cell membrane tube that conducts electrical impulses (passes them on)
Dendritereceives impulses from receptors or other neurons
Cell bodyhouses nucleus and all other organelles
o Sensory neuronsrespond to certain stimuli
PNS & sense organs
o Interneuronstransmit signals between CNS and PNS components
Brain & spinal cord
o Motor neuronsPNS components that receive CNS output information
PNS & muscle tissues
o Neuroglial cellsprovide physical support and protect neurons ****do not transmit
signal impulses***
Schwann cells
Neuroglial cells that enclose and protect the axons of many nerve cells in the
PNS
Insulates the axon with myelin
o Myelinmixture of proteins and lipids secreted by neuroglial cells on
the axons of neurons
Nerve signal:
o Resting potentialthe difference in charge across the membrane of a neuron
o Sodium-potassium pumppump sodium out of the cell and potassium into the cell to
create a charge and concentration gradient
Electrochemical gradient--combined effect of a concentration gradient
Ion channelallow certain ions to diffuse across the plasma membrane passively
o Action potentialsudden temporary reversal of membrane charge
Depolarizepositive charge from excess sodium flips charge of membrane
Repolarizepotassium rushing out of the cell reestablishes resting potential
o Synapserelay point between a neuron and receiving cell
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