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Chapter 44
The Nervous System
28
Biology
Undergraduate 1
02/04/2008

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Term
Central Nervous System
Definition
Portion of nervous system where most association occurs; in vertebrates, composed of brain and spinal cord
Term
Peripheral Nervous System
Definition
Consists of neurons connecting the CNS to the rest of the body.
Term
Somatic Motor Neruons
Definition
Alpha motor neurons; large lower motor neurons of the brainstem/spinal cord
Term
Autonomic Motor Neurons
Definition
Part of the PNS that acts as a control system, maintaining homeostasis in the body
Term
Sympathetic Neurons
Definition
Involved in the ANS; becomes more active during times of stress, comprises fight-or-flight response
Term
Parasympathetic Neurons
Definition
Involved in the ANS, generally functions in opposition to the sympathetic nervous system.
Term
Cell Body
Definition
The central structure of a neuron; contains the cell nucleus
Term
G Proteins
Definition
GTP-Binding membrane proteins that couple many extracellular receptors to intracellular effector proteins
Term
Myelin / Myelin Sheath
Definition
A fatty layer surrounding the long axons of motor neurons in the PNS of vertebrates
Term
Node of Ranvier
Definition
Gap formed at the point where 2 Schwann cells meet and where the axon is in direct contact with surrounded intracellular fluid
Term
Gray Matter
Definition
Cerebral cortex; composed of nerve cell bodies and blood vessels
Term
White Matter
Definition
A type of neural tissue in the brain/spinal cord composed primarily of myelin-covered axons
Term
Resting Membrane Potential
Definition
The charge difference (difference in electric potential) that exists across a neuron at rest (about 70 mV)
Term
Graded Potentials
Definition
Membrane potentials that vary in magnitude
Term
Summation
Definition
Repetitive activation of the motor neurons resulting in maximum sustained contraction of a muscle
Term
Threshold
Definition
Minimum amount of stimulus required for a nerve to fire (depolarize)
Term
Action Potential
Definition
Transient, all-or-none reversal of the electric potential across a membrane; in neurons, initiates transmission of a nerve impulse
Term
Saltatory Conduction
Definition
Very fast form of nerve impulse conduction in which the impulses leap from node to node over insulated portions
Term
Synapse
Definition
Junction between a neuron and another neurons or muscle cell; the 2 cells do not touch, the gap being bridged by neurotransmitter molecules
Term
Synaptic Vesicles
Definition
Vesicle of a neurotransmitter produced by the axon terminal of a nerve
Term
Synaptic Cleft
Definition
Space between adjacent neurons
Term
Neurotransmitters
Definition
Chemical released at the axon terminal of a neurons that travels across the synaptic cleft, binds a specific receptor on the far side, and, depending on the nature of the receptor, depolarizes or hyperpolarizes a 2nd neuron or a muscle/gland cell
Term
EPSP (Excitatory Postsynaptic potential)
Definition
Depolarization of the post-synaptic cell upon excitation
Term
IPSP (Inhibitory Postsynaptic Potential)
Definition
Hyperpolarization of the postsynaptic membrane in response to a particular neurotransmitter
Term
GABA (Gamma-Amino Butyric Acid)
Definition
An amino acid that acts as a inhibitory neurotransmitter
Term
Habituation
Definition
A learned behavior in which an animal exhibits a lessened response with repetition of a stimulus
Term
Limbic System
Definition
A network of structures in the brain involved in memory and emotions
Term
Knee-Jerk Reflex
Definition
The test conducted by striking the Patellar tendons of the knee for reflex indications of a lesion
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