Transcript Brain and Spinal Cord

The Brain
Anatomy and Physiology
Membranes cover the brain and
spinal cord
• Membranes are
called meninges
• Three layers: dura
mater, arachnoid
mater, and pia mater
• Dura mater is outer,
arachnoid is middle,
pia is innermost.
Meninges
Meninges
Meninges
• Between the arachnoid
and pia maters is the
subarachnoid space,
which contains
cerebrospinal fluid.
• A series of spaces in
the brain, called
ventricles, also contain
cerebrospinal fluid.
Cerebrospinal Fluid
• Is secreted by
specialized
capillaries of the
dura mater layer.
These special tissues
are called choroid
plexuses.
• The fluid circulates
through the
ventricles and is
reabsorbed into the
blood
Cerebrospinal Fluid
• The pressure remains
fairly constant, as fluid
is secreted and
absorbed continuously
• The brain and spinal
cord “float” in the
fluid, which supports
and protects them
• Also controls ions and
carries waste to blood
Pressure can be measured,
and samples of fluid can be
taken to diagnose infections
Meningitis
Meninges become inflamed,
may be viral or bacterial
Major Regions of the Brain
• Cerebrum: largest part;
sensory and motor
functions, higher
reasoning skills
• Diencephalon: processes
sensory info
• Cerebellum: coordinate
voluntary muscle
• Brain Stem: regulates
visceral activities
Cerebrum
• Divided into lobes
• Lobes are named after the
skull bones they underlie
• Two hemispheres divided
by corpus callosum
• Convoluted surface
• Outermost part is the
cerebral cortex
Cerebrum
Cerebrum
Cerebral Cortex
Diencephalon
• Located between
cerebral hemispheres
and above the
midbrain
• Contains the thalamus,
hypothalamus, optic
tracts, posterior
pituitary gland, pineal
gland
Diencephalon
Brain Stem
• Connects cerebrum to
the spinal cord
• Consists of midbrain,
pons, medulla
oblongata
Functions of Brain Stem
• Relay center
• Reflex center
• Medulla oblongata
contains regulatory
centers for heart rate,
constriction and
dilation of blood
vessels, respiration
Cerebellum
• Reflex center for
integrating sensory
information
concerning the
position of body parts
• Coordinates complex
skeletal muscle
movements
Hemisphere Dominance
• Everyone uses both
hemispheres in basic
functions
• Right side controls
motor functions of the
left side; left side
controls motor
functions of the right
side. (stroke)
Hemisphere Dominance
• Most people have a
dominant hemisphere,
although you can be
equally right and left
brained
• “Right brained” or “left
brained” refers to which
hemisphere is dominant
• Determines your manner
of thinking; they are not
the same!
Hemisphere Dominance
Left Brain thinkers are
• Logical and sequential
• Rational
• Analytical
• Objective
• Look at the parts
Right brain thinkers are
• Random
• Intuitive
• Holistic
• Synthesizing
• Subjective
• Look at wholes
Hemisphere Dominance
“Right brains” often choose
as careers
• Athletes
• Entrepreneurs
• Sales
• Artist
• Musician
• Craftsman
• dancer
Hemisphere Dominance
“Left brains” often
choose careers in
• Law
• Accounting
• Science
• Medicine
Cranial Nerves
• Twelve pairs of cranial
nerves arise from the
inferior side of the brain
• 1st pair comes from
cerebrum
• Other 11 pairs originate
from brain stem
• Lead to parts of the head,
neck, and trunk
Each nerve has a name and a
roman numeral
A Career Cut Short by Spinal Cord
Injury
The Spinal Cord
• Two functions: conduct
nerve impulses; reflex
center
• Is part of the CNS
• Is a nerve column going
down from brain into the
vertebral column
• Ends near the 1st or 2nd
lumbar vertebrae
• Surrounded by meninges,
which continue below the
L1 and L2 vertebrae
Where would you do a spinal tap
to collect CSF without damaging
the spinal cord?
Spinal Cord
• A cross section shows
a core of gray matter
surrounded by white
matter
• Gray matter =
unmylenated axons
and neuron cell
bodies
• White matter =
masses of mylenated
axons
Notice the three layers of
meninges
• The white matter
contains 3 sections of
longitudinal bundles
called nerve tracts
(posterior, anterior,
and lateral)
• Ascending tracts of
nerves carry sensory
information to the
brain
• Descending tracts
carry motor impulses
to muscle or glands
Spinal Cord
posterior
lateral
Anterior
Spinal Nerve
Tracts
Posterior section of white
matter contains only
ascending nerve tracts
The anterior and lateral
sections of white matter
contain both ascending and
descending nerve tracts
Spinal Nerves
• Coming off the spinal
cord are 31 pairs of
spinal nerves
• Grouped and labeled
according to the level
of vertebrae they come
from
• These nerves are part
of the PNS
C1-C8; T1-T12; L1-L5; S1-S5
Spinal Nerves
• The 31 pairs branch
out to serve various
parts of the body
• Which nerve serves
which parts of the
body can be seen on a
dermatome map
Autonomic vs Somatic nervous
Systems
• Somatic: motor pathways
of PNS that lead to the
skin and skeletal muscles
• Autonomic: happens
without conscious effort—
maintains homeostasis by
regulating smooth
muscles, blood pressure,
breathing rate, heart rate,
etc.
Two Divisions of Autonomic
• Sympathetic, which
prepares the body for
stressful, emergency
situations
• Parasympathetic,
which is most active
during ordinary,
restful conditions, and
returns the body to
normal conditions
after the emergency
Autonomic Nerve Fibers
• Are arranged slightly
differently than
somatic nerve fibers
• A pathway from the
brain or spinal cord to
the skeletal muscle
contains two neurons
instead of just one
Page 241 in your
textbook
Autonomic Nerve Fibers
• The first neuron leaves
the brain or spinal
cord and joins with a
mass of neurons called
a ganglion. This
neuron is
preganglionic. The
second neuron that
leaves the ganglion is
called postganglionic
Autonomic
Neurotransmitters
• Acetylcholine is the
neurotransmitter secreted by
preganglionic fibers of both
the sympathetic and
parasympathetic divisions.
The postganglionic fibers of
the parasympathetic also
secrete acetylcholine
• Norepinephrine is the
neurotransmitter secreted by
the postganglionic fibers of
the sympathetic division.
Autonomic Control
• Brain and spinal cord
control most of its
activities
• Medulla oblongata
receives sensory impulses
and send motor responses
• Hypothalamus regulates
body temp, hunger, thirst,
water and electrolyte
balances.
• Other brain areas control
autonomic system during
emotional stress