The Nervous System
Divisions of the Nervous
System
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Central versus Peripheral
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Central – Brain and spinal cord
Peripheral – Everything else
Somatic versus Autonomic
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Somatic – Nerves serving conscious
sensations and skeletal muscles
Autonomic – Nerves serving vegetative
functions, smooth muscles.
Branches of the Autonomic
Nervous System
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Sympathetic Branch – prepares the
body for emergency action
Parasympathetic Branch – serves the
more vegetative existence.
But this division is over-simplified;
sometimes the two branches cooperate.
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Functions of the Spinal Cord
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Convey sensory inputs to other levels of
the spinal cord and to the brain.
Convey motor commands from the
brain and spinal cord to motor neurons.
Provide local command and control for
coordinated movement (mediate the
spinal reflexes).
The Brain
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The picture to
right shows the
human brain
bisected along
the midline.
Major Parts of the Brain
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The brainstem – looks like the stem of a
head of cabbage.
The midbrain
The forebrain – divided into the two
cerebral hemispheres
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Major Parts of the Brainstem
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The Medulla
The Pons
The Cerebellum
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(not shown)
The Reticular
Formation
[Note: Picture shows
some higher levels of
the brain as well]
The Medulla
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Lowest part of the brain
Includes sensory and motor tracts
connecting brain and spinal cord.
Basic physiological functions
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Heart rate
Blood pressure
Respiration
The Pons
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About 90% of sensory- and motor-tract
fibers cross to the opposite side of the
brain here.
Centers involved in sleep/waking.
Connections to cerebellum.
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The Cerebellum
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Large structure hanging off back of
pons.
Balance, smooth motor coordination.
Certain types of motor learning involve
this structure.
The Reticular Formation
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Located along the central core of the
brainstem and midbrain.
Serves to regulate arousal.
The Midbrain
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Structures here are involved in visual
and auditory reflexes, the modulation of
pain, and other functions.
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The Forebrain or
Diencephalon
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Here the brain divides into two distinct
halves. Some important structures
include
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Hypothalamus
Thalamus
Basal Ganglia
Limbic System
Cerebral Hemispheres
The Hypothalamus
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Basic drives – hunger, thirst, sex drive
Body temperature regulation
Upper end of the autonomic nervous
system.
Controls the output of the pituitary
gland (the so-called “master” endocrine
gland).
The Thalamus
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Major relay station between the lower
brain and the cerebral cortex.
Located just above the hypothalamus.
Crucial for conscious experience.
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The Basal Ganglia
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Involved in motor control and
coordinated movement.
Damage here can produce strange
behavior, e.g., “hemiballism.”
Loss of certain inputs from the
brainstem produces Parkinson’s
Disease.
The Limbic System
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This is a major component of the
emotion circuitry of the brain.
Structures include the septum,
amygdala, hippocampus, and
hypothalamus, with connections to the
frontal lobes of the cortex.
The Cerebral Cortex
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Divided into two
hemispheres
Each has four lobes:
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Frontal lobe
Parietal lobe
Occipital lobe
Temporal lobe
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Frontal Lobe
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Planning
Movement (motor strip at rear)
Speech production (Broca’s area)
Social inhibitions
Integration of reasoning and emotion
Parietal Lobe
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Touch (somato-sensory strop at front)
Sense that body belongs to self
Recognition
Spatial orientation -- wayfinding
Occipital Lobe
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Located in the back of the cortex.
Mainly devoted to vision.
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Temporal Lobe
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Hearing
Language comprehension (Wernicke’s
area)
Storing of long-term memories
(hippocampus)
The Corpus Callosum
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Large bundle of nerve fibers (about 2
million) connecting the two cerebral
hemispheres.
Integrates the information being
processed in the two hemispheres.
Severing creates two separately
conscious minds (!)
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