Cindy Zhu, PSYC271 Fall 2011 Page 1 of 7
Chapter 3: Anatomy of the Nervous System
3.1 General Layout of the Nervous System
Division of the Nervous System
• Central nervous system (CNS): brain and
spinal cord, encased in bone
• Peripheral nervous system (PNS):
located outside skull and spine, including the
somatic nervous system and the autonomic
• Afferent: “sensory” neurons, carry sensory
signals from receptors to CNS.
• Efferent: “motor” neurons, carry motor
signals from CNS to muscles or glands.
• Spinal nerves: 31 pairs of nerves that project from spine, all have both sensory and
• Cranial nerves: 12 pairs of nerves that project from the brain, most have both sensory
and motor fibres except I (olfactory) and II (optic) which are purely sensory.
o The longest are the vagus nerves (X) that have fibres to and from the gut.
Autonomic Nervous System Somatic Nervous System
What about? Internal environment External environment
* Afferent: sensory signals from * Afferent: sensory signals from
internal organs skin, muscles, eyes, ears about
environment and your position in it
* Goal is to maintain homeostasis
Do we control it? Unconscious, involuntary Voluntary
Effector organs Smooth muscle (gut, blood vessels), Skeletal muscles only
cardiac muscle, glands
Effect on targets Excitatory or inhibitory Excitatory only (e.g. muscle contraction)
Neuron structure Two neurons to get to target Single neuron straight from CNS to
(preganglionic and postganglionic target
neurons) Cindy Zhu, PSYC271 Fall 2011 Page 2 of7
The AUTONOMIC NERVOUS SYSTEM (ANS) can be further subdivided:
Parasympathetic Nervous Sympathetic Nervous System
Where from? Brain and sacral spinal cord (at base, Thoracic and lumbar spinal cord (back
near vestigial tail) and lower back)
Postganglionic Second-stage neuron is close to target Second stage neuron is far from target
Ganglion Ganglia are close to target organs Ganglia are far from target organs, lying
close to spinal cord
Effect Conserve energy, psychological Stimulate, organize, mobilize energy in
relaxation: rest and digest threatening situations; arousal: fight or
A target organ can receive opposing
sympathetic and parasympathetic input,
and is thus controlled by the relative
Meninges, Ventricles, and Cerebrospinal Fluid Cindy Zhu, PSYC271 Fall 2011 Page 3 of7
• Meninges: 3 protective membranes for the brain and spinal cord: from outside in:
o Dura mater (“tough mother”): 2 inflexible, tough
membrane layers anchored to skull. Areas where the 2 layers
separate are dural sinuses.
o Arachnoid mater (“spider-like mother”): attached to
inferior surface of dura mater.
o Subarachnoid space: filaments look like spider web,
filled with cerebrospinal fluid (CSF) to support and protect
o Pia mater: innermost, firmly attached to brain/spinal
• Cerebrospinal fluid: fills subarachnoid space, central canal of
spinal cord and cerebral ventricles. Functions: buoyancy (1.4kg to
50grams with CSF, prevents drooping under its own weight),
circulation (provides nutrients, removes waste), and protection
(cushion against skull, without it would have
serious headaches). Subarachoid
• CSF is produced by the choroid plexuses, Space
capillaries that protrude into the ventricles from the
pia mater and filter blood to produce CSF.
• CSF flows through subarachoid space and
subarachoid granulations before being absorbed
into blood-filled dural sinuses (in the dura mater)
and draining into the large jugular veins of the
o If flow is CSF is blocked, the resulting
buildup cause walls of ventricles to expand,
causing hydrocephalus (water head).
• Ventricles: four large internal chambers of the
brain, which are all connected and filled with CSF.
• Cerebral aqueduct: connects third and fourth ventricles.
• Central canal: small CSF-filled central channel that runs the length of the spinal cord.
• Blood-brain barrier: impedes passage of toxic substances to prevent disturbance of the
brain by introduction of unwanted chemicals. This is due to the special tightly packing
structure of cerebral blood vessels, which form a barrier to the passage of proteins and
other large molecules.
• The degree to which drugs can influence brain activity depends on ability to penetrate
the blood-brain barrier. Some necessary molecules, like glucose, are actively transported
3.2 Cells of the Nervous System
Anatomy of Neurons Cindy Zhu, PSYC271 Fall 2011 Page 4 of7
• Neurons: cells specialized for reception, conduction and transmission of
• Internal anatomy: endoplasmic reticulum (rough with ribosomes do protein synthesis,
smooth do lipid synthesis); golgi complex (packages molecules in vesicles), microtubules
(rapid transport of material throughout neuron), mitochondria (aerobic energy release),