Download The Nervous System: Overview The nervous system Divisions of the

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The nervous system
 Responsible for:
 Detecting changes in the internal and external The Nervous System: Overview
environments
 Relaying messages to the endocrine system
 Relaying messages to the musculoskeletal system
e ay g essages to t e uscu os e eta syste
Section 9.1
Section
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Divisions of the nervous system
 Cognitive processes
 Perception
Divisions of the nervous system
Two main divisions:
1. Central nervous system (CNS): The brain & spinal cord
NERVOUS SYSTEM
2. Peripheral nervous system (PNS): All of the other parts of the nervous system
of the nervous system
central nervous system (CNS)
 Somatic
 Autonomic
peripheral nervous system (PNS)
somatic nerves
autonomic nerves
control muscles, bones, and skin
control internal organs of the body
The peripheral nervous system
Nerve cells
The somatic nervous system is associated with conscious processes, and contains two types of neuron:
 Motor neurons
 Sensory neurons
Two different types of cells make up nerve tissue:
The autonomic nervous system is associated with unconscious processes, and has two divisions:
 Sympathetic
 Parasympathetic
1.
Glial cells (support cells)
2.
Neurons (functional cells):
(
)
 Sensory neurons – Relay environmental information to the CNS for processing
 Interneurons – Link neurons within the body; all neurons within the CNS are interneurons
 Motor neurons – Relay instructions to muscles, organs, and glands, in order to produce responses
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Neuron: Anatomy
Receive information from other nerve cells;
Conduct nerve impulses towards the cell bodies
Conduction of nerve impulses
Neurons conduct electrochemical messages from one neuron to the next.
Contain the nucleus,
cytoplasm, organelles
y p
, g
The gap between neurons is called a synapse.
Extension of cytoplasm, originating from the cell body;
Project nerve impulses away from the cell body, towards other nerve cells
Synapse
Neuron: Anatomy (2)
 First neuron =
 Myelin sheath presynaptic neuron
(fatty protein)
 Insulation
 Formed by Schwann p
g cells))
cells ((special glial
 Second neuron =
postsynaptic neuron
postsynaptic neuron
 Nodes of Ranvier
 Increase speed of transmission
Speed of impulses
White matter vs. Grey matter
 Factors:
 White matter is myelinated
 Myelination
 Grey matter is not
 Diameter of axon (smaller = faster)
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Arrangement of nerve cells
Neural circuits
 Nerve cells sometimes meet in bundles called ganglia
Typical neural circuit:
sensory receptor  spinal cord  brain  spinal cord  motor neurons
(singular ganglion)
 Near the spine (dorsal root ganglia)
 Chain of ganglia, parallel to the spine (autonomic ganglia)
Reflex arc:
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sensory receptor  spinal cord  motor neurons
 Allows communication between central and peripheral nervous systems
Reflex arcs
 Much faster than typical neural circuits
 Allows quick response to environmental stimuli
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