Download What are the primary divisions of the nervous system?

Psychology 304:
Brain and Behaviour
Lecture 6
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The Structure of the Nervous System
1. What are the primary divisions of the nervous system?
2. How are the components of the central nervous
system protected from injury?
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What are the primary divisions of the nervous
system?
• The nervous system is comprised of two major divisions:
1. Central Nervous System (CNS)
 The CNS is located in the skull and spine.
 The CNS consists of two subdivisions: The brain and
spinal cord.
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Brain
Spinal
Cord
The CNS
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2. Peripheral Nervous System (PNS)
 The PNS is located outside of the skull and spine.
 The PNS consists of nerves that extend throughout
the body. These nerves: (a) carry sensory
information about the external and internal
environment to the CNS, and (b) carry motor signals
from the CNS to other regions of the body.
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The PNS
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 There are 31 pairs of PNS nerves that project to
and from the spinal cord (spinal nerves). There are
12 pairs of PNS nerves that project to and from the
brain (cranial nerves).
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The Spinal Nerves
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Dorsal and Ventral
Roots of Spinal Cord
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The Cranial Nerves
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 The PNS consists of two subdivisions :
The somatic nervous system: Regulates responses
to the external environment.
Composed of afferent nerves that carry sensory
information about the external environment to the
CNS and efferent nerves that carry motor signals
from the CNS to the muscles of the body.
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The autonomic nervous system: Regulates the
body’s internal environment.
Composed of afferent nerves that carry sensory
information from the internal organs to the CNS
and efferent nerves that carry motor signals from
the CNS to the internal organs of the body.
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There are two types of efferent nerves that
characterize the autonomic nervous system:
sympathetic efferent nerves and parasympathetic
efferent nerves.
Sympathetic efferent nerves: Stimulate changes to
the internal organs that prepare the organism for
action (i.e., “fight and flight” responses).
Parasympathetic efferent nerves: Stimulate
changes to the internal organs that prepare the
organism to conserve and rest (i.e., “rest and
digest” responses).
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Some Functions of Sympathetic and
Parasympathetic Activation
Organ
Sympathetic Effect
Parasympathetic Effect
Salivary gland
Decreases secretion
Increases secretion
Heart
Increases heart rate
Decreases heart rate
Blood vessels
Constricts blood vessels
in most organs
Dilates blood vessels in a
few organs
Iris radial and
sphincter muscles
Dilates pupils
Constricts pupils
Sweat gland
Stimulates secretion
No effect
Stomach and
intestine
No effect
Stimulates secretion and
motility
Lungs
Dilates bronchioles
Constricts bronchioles
Arrector pili muscles
Erects hair and creates
gooseflesh
No effect
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The Major Divisions of the Nervous System
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How are the components of the central nervous
system protected from injury?
• The brain and spinal cord are protected by three
anatomical features:
1. Bone:
 The brain is encased in the skull. The spinal cord is
encased in the vertebral column (i.e., spine or
backbone).
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2. Meninges:
 Lay beneath the bone that protects the CNS.
 Consists of three layers:
Dura mater: outer meninx, a tough membrane.
Arachnoid membrane: Immediately inside the dura
mater, a fine spider web-like membrane.
Pia mater: Innermost meninx, delicate membrane
that adheres to the surface of the CNS.
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Anatomical Features that Protect the CNS
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Anatomical Features that Protect the CNS
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3. Cerebrospinal fluid:
 A clear fluid found in three regions:
The subarachnoid space.
The central canal of the spinal cord.
The cerebral ventricles.
 Supports and cushions the brain and spinal cord.
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The Fluid-Filled Ventricles and
Central Canal
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Hydrocephalus
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The Structure of the Nervous System
1. What are the primary divisions of the nervous system?
2. How are the components of the central nervous
system protected from injury?
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