Unit 1D: The Central Nervous
System
Protective Tissues
• The CNS consists of the brain
and spinal cord
• The CNS is surrounded by
layers of protective tissue
known as the meninges.
– Swelling of the meninges due to
bacterial or viral infection is
known as meningitis.
CSF and the Ventricles
• The brain has a series of internal chambers that make and
distribute CSF. They are known as the ventricles.
• CSF is made from blood in the
ventricles and resembles blood
plasma
• The CSF:
– Supports weight of brain (makes it
neutrally buoyant)
– Cushions it (protects from injury)
– Maintains chemical balance
• If there is a blockage to the draining
of the CSF, brain damage can result
Spinal cord
• Long cable of axons that connects the brain
to the peripheral nervous system.
• Runs down the inside of the vertebral
column
• Size:
– As thick as your pinkie finger
– Only 2/3 the length of the vertebral column
(17-18in)
• Function
– Carries information through motor neurons
from brain to muscles and glands
– Carries information through sensory neurons
from sense organs to brain
– Creates some reflexes
Spinal Nerves (PNS)
• Nerves branch off of the
spinal cord at each
vertebral joint.
• These nerves follow blood
vessels and carry sensory
and motor neuron axons
• The extent of damage
from injury can be
determined by location of
injury
Hindbrain
• The hindbrain is responsible for lifesaving functions common to all
vertebrates.
• Major areas:
– Cerebellum
• Receives visual, auditory, vestibular and
somatosensory information and
coordinates it.
• Works to make muscle movement smooth
and coordinated.
Hindbrain (cont)
– Pons
• Involved in sleep, respiration, swallowing, bladder
control, hearing, equilibrium, taste, eye movement,
facial expressions, facial sensation, and posture
• Also controls switch from inhalation to exhalation
• Damage to this area can lead to “locked-in syndrome”
– Aware and awake but unable to communicate!
Hindbrain (cont)
– Medulla
• Regulates vital functions such as breathing, heart rate,
blood pressure, etc.
• It is the brain’s connection to the spinal cord.
Midbrain
• Functions:
– primary processing of auditory and visual
information (before it is passed to thalamus and
cortex)
• In lower vertebrates, these are the only processing
areas.
– Motor functions
– Species-typical behaviors
– Sleep/arousal
Forebrain
• Thalamus
– Major relay center of information coming into the
brain from the senses
– Regulates states of sleeping and wakefulness
Forebrain
• Hypothalamus
– rests below the thalamus and
above the pituitary
– It is the link between the
autonomic nervous system and
the endocrine system
– It is responsible for maintaining
homeostasis
• hunger, thirst, body temp, sleep
Forebrain
• Basal Ganglia
– Involved in
movement
selection and
initiation
– Allows muscles to
relax in motion
Forebrain
• Amygdala
– Responsible for fear,
aggression, emotion
• Hippocampus
– Responsible for
formation of longterm memories
Forebrain
• Cerebrum:
– Largest part of human brain (most evolved)
– Where conscious “thinking” takes place
• Cerebral Cortex
– Outer 3mm of cerebrum (surface area = 2.5ft2)
– Highly convoluted (2/3 of area is in folds)
– Mostly made of cell bodies of neurons (grey matter)
• The rest of the cerebrum is made of the myelinated axons of these
neurons and the fat makes this area look white - “white matter”
Regions of the Cortex
• In all cases:
– the “primary cortex” area
for a sense receives input
directly from sense organs
• Damage causes loss of sense
– The “association areas” get
input from primary cortex
areas and process it. Also
where memories tied to
those senses are stored.
• Damage causes loss of
understanding
– With the exception of taste and smell, the cortex receives
information from the contralateral side of the body
Regions of the Cortex
• Visual Cortex and
Association Area
– Sight
• Auditory Cortex and
Association Area
– Sound
• Motor Cortex and
Prefrontal Cortex (Motor
Assoc. Area)
– Controls movement and
planning for movement
– Specific areas control
specific body parts.
Regions of the Cortex
• Somatosensory Cortex and
Association Area
– Strip that transects the
cerebrum is divided into areas
that respond to specific body
parts (touch, feel, etc.)
– The more input and processing
required for a region, the more
area it is given
– Tongue/mouth and thumb/hand
get most
Regions of the Cortex
• The Cerebral Cortex is often divided
in lobes based upon the bones on
top of the areas:
– Frontal lobe
• Higher thinking, morality, decision
making
– Parietal Lobe
• Integrates sensory info and determines
spatial sense and navigation
– Temporal Lobe
• Auditory and visual processing, speech
and long-term memory
– Occipital Lobe
• Vision and dreams
Regions of the Cortex
Some tasks are shared equally by the hemispheres, and some tasks
are lateralized. Each hemisphere has a majority of responsibility for
the following:
• Left:
–
–
–
–
–
–
–
Sequence
Analysis
Details
Talking
Understanding
Reading
Writing
• Right
– Synthesis
– Perceiving
shape and size
– Read maps
– Building objects
– Creativity
The Corpus Callosum bridges the gap between the two hemispheres.