Download Gross Anatomy

Introduction to
Central Nervous
System
• Located btwn the
diencephalon and the
pons.
– 2 bulging cerebral
peduncles on the ventral
side. These contain:
• Descending fibers that go
to the cerebellum via the
pons
• Descending pyramidal
tracts
– Running thru the midbrain
is the hollow cerebral
aqueduct which connects
the 3rd and 4th ventricles of
the brain.
– The roof of the aqueduct (
the tectum) contains the
corpora quadrigemina
• 2 superior colliculi that
control reflex movements
of the eyes, head and
neck in response to visual
stimuli
Midbrain
•Cranial nerves 3&4
(oculomotor and trochlear)
exit from the midbrain
•Midbrain also contains the
headquarters of the
reticular activating system
Midbrain
• On each side, the
midbrain contains a red
nucleus and a
substantia nigra
– Red nucleus contains
numerous blood vessels
and receives info from
the cerebrum and
cerebellum and issues
subconscious motor
commands concerned w/
muscle tone & posture
– Lateral to the red nucleus
is the melanin-containing
substantia nigra which
secretes dopamine to
inhibit the excitatory
neurons of the basal
nuclei.
• Damage to the
Pons
• Literally means “bridge”
• Wedged btwn the midbrain &
medulla.
• Contains:
– Sensory and motor nuclei for 4
cranial nerves
• Trigeminal (5), Abducens (6),
Facial (7),
and Auditory/Vestibular (8)
– Respiratory nuclei:
• Apneustic & pneumotaxic
centers work w/ the medulla to
maintain respiratory rhythm
– Nuclei & tracts that process and
relay info to/from the cerebellum
– Ascending, descending, and
transverse tracts that
interconnect other portions of
the CNS
•
Medulla
Oblongata
Most inferior region of
the brain stem.
• Becomes the spinal
cord at the level of the
foramen magnum.
• Ventrally, 2 ridges (the
medullary pyramids) are
visible.
– These are formed by the
large motor corticospinal
tracts.
– Right above the medullaSC junction, most of
these fibers cross-over
(decussate).
•
Medulla
Oblongata
Nuclei in the medulla are
•
associated w/ autonomic
control, cranial nerves,
and motor/sensory relay.
Autonomic nuclei:
– Cardiovascular centers
•
•
Cardioinhibitory/cardioacc
eleratory centers alter the
rate and force of cardiac
contractions
Vasomotor center alters
the tone of vascular
smooth muscle
– Respiratory rhythmicity
centers
•
Receive input from the
pons
– Additional Centers
•
Emesis, deglutition,
coughing, hiccupping, and
Medulla
Oblongata
•
Sensory & motor nuclei of 5
cranial nerves:
–
•
Auditory/Vestibular (8),
Glossopharyngeal (9), Vagus
(10), Accessory (11), and
Hypoglossal (12)
Relay nuclei
–
–
Nucleus gracilis and nucleus
cuneatus pass somatic sensory
information to the thalamus
Olivary nuclei relay info from the
spinal cord, cerebral cortex, and
the brainstem to the cerebellar
cortex.
What brainstem
structures are
visible here?
Limbic
System
•
•
•
Includes nuclei and tracts along the
border btwn the cerebrum and the
diencephalon.
Functional grouping rather than
anatomical
Functions include:
1.
2.
3.
•
•
Establishing emotional states
Linking conscious cerebral cortical
functions w/ unconscious functions of
the brainstem
Facilitating memory storage and
retrieval
Limbic lobe of the cerebrum consists of 3 gyri that curve along the corpus
callosum and medial surface of the temporal lobe.
Limbic system  the center of emotion – anger, fear, sexual arousal,
pleasure, and sadness.
Reticular
Formation
• Extensive network of
neurons that runs thru the
medulla and projects to
thalamic nuclei that
influence large areas of the
cerebral cortex.
– Midbrain portion of RAS most
likely is its center
• Functions as a net or filter
for sensory input.
– Filter out repetitive stimuli.
Such as?
– Allows passage of infrequent
or important stimuli to reach
the cerebral cortex.
– Unless inhibited by other brain
regions, it activates the
cerebral cortex – keeping it
How might the “sleep centers”
of your brain work? Why does
alcohol make you tired?
Protection
• What is the major protection for the
brain?
• There are also 3 connective tissue
membranes called the meninges:
• Cover and protect the CNS
• Protect blood vessels
• Contain cerebrospinal fluid
• The 3 meninges from superficial to
deep:
• Dura mater
• Arachnoid mater
• Pia mater
Skin
Galea Aponeurotica
Connective Tissue
Bone
Dura Mater
Arachnoid mater
Spinal Cord
• Functions to transmit
messages to and from the
brain (white matter) and to
serve as a reflex center (gray
matter).
• Tube of neural tissue
continuous w/ the medulla at
the base of the brain and
extends about 17” to just
below the last rib. (Ends at
L1)
• Majority of the SC has the
diameter of your thumb
• Thicker at the neck and end of
the cord (cervical and lumbar
enlargements) b/c of the large
group of nerves connecting
Spinal Cord
• Surrounded by a single
layered dura mater
and arachnoid and pia mater.
• Terminates in cone shaped
structure called the conus
medullaris.
– The filum terminale, a fibrous
extension of the pia mater, extends
to the posterior surface of the
coccyx to anchor the spinal cord.
• The cord does not extend the
entire length of the vertebral
column – so a group of nerves
leaves the inferior spinal cord
and extends downward. It
resembles a horses tail and is
called the cauda equina.
Spinal Cord
• Notice the gross features
of the spinal cord on the
right.
• 31 pairs of spinal nerves
attach to the cord by
paired roots and exit from
the vertebral canal via the
intervertebral foramina.
Cross Sectional Anatomy of the Spinal Cord
• Flattened from front to back.
• Anterior median fissure and posterior median sulcus
partially divide it into left and right halves.
• Gray matter is in the core of the cord and surrounded
by white matter.
• Resembles a butterfly.
• 2 lateral gray masses connected by the gray
commissure.
• Posterior projections are the posterior or dorsal horns.
• Anterior projections are the anterior or ventral horns.
• In the thoracic and lumbar cord, there also exist lateral
Gray Matter
• Posterior horns contain
interneurons.
• Anterior horns contain some
• interneurons as well as the cell
bodies of motor neurons.
– These cell bodies project their axons via the
ventral roots of the spinal cord to the skeletal
muscles.
– The amount of ventral gray matter at a given
level of the spinal cord is proportional to the
amount of skeletal muscle innervated.
Gray Matter
• Lateral horn neurons are
sympathetic motor neurons
serving visceral organs.
– Their axons also exit via the
ventral root.
• Afferent sensory fibers
carrying info from
peripheral receptors form
the dorsal roots of the
spinal cord. The somata of
these sensory fibers are
found in an enlargement
known as a dorsal root
ganglion.
• The dorsal and ventral
roots fuse to form spinal
nerves.
White Matter
• Myelinated nerve fibers.
• Allows for communication btwn the brain and spinal cord or
btwn different regions of the spinal cord.
• White matter on each side of the cord is divided into columns
or funiculi.
– Typically, they are ascending or descending.
• What does that mean?
Spinal Nerves
• 31 nerves
connecting the
spinal cord and
various body
regions.
• 8 paired cervical
nerves
• 12 paired thoracic
nerves
• 5 paired lumbar
nerves
• 5 paired sacral
nerves
Spinal Nerves
• Each connects to the
spinal cord by 2 roots –
dorsal and ventral.
• Each root forms from a
series of rootlets that
attach along the whole
length of the spinal cord
segment.
• Ventral roots are motor
while dorsal roots are
•
Spinal
Nerves
The 2 roots join to
form a spinal nerve
prior to exiting the
vertebral column.
• Roots are short
and horizontal in
the cervical and
thoracic regions
while they are
longer and more
horizontal in the
sacral and lumbar
• regions.
Almost immediately after emerging from its intervertebral
foramen, a spinal nerve will divide into a dorsal ramus, a
ventral ramus, and a meningeal branch that reenters and
innervates the meninges and associated blood vessels.
• Each ramus is mixed.
• Joined to the base of the ventral rami of spinal nerves in the
thoracic region are the rami communicantes. These are
sympathetic fibers that we’ll deal with shortly.
• Dorsal rami supply the posterior body trunk whereas the thicker
ventral rami supply the rest of the body trunk and the limbs.
The Brain
• 3 primary divisions:
– Forebrain
• cortex (folded stuff)
• limbic system, etc (stuff around brain stem)
– Midbrain (top of brainstem)
– Hindbrain (bottom of brainstem + cerebellum)
Hindbrain
Medulla
Pons
Cerebellum
Pons
Medulla
Cerebellum
http://wwwunix.oit.umass.edu/~psyc335c/lectures/hindbrain.gif
Medulla:
Controls vital reflexes: breathing,
heart rate, vomiting, salivation,
coughing, sneezing
- Via cranial nerves
Damage to medulla can be fatal
Large doses of opiates can be fatal
b/c suppress activity of
medulla…why…?...b/c receptors
there!
Pons:
Also has cranial nerves
Location of axon decussation
(where axons cross from one side
of the brain to the other…so left
brain controls right body and vice
versa)
Reticular formation: motor control,
arousal, consciousness
Midbrain:
Cerebral aqueduct
More cranial nerves
Superior colliculus (visual info)
Inferior colliculus (auditory info)
Substantia nigra: dopamineproducing cells, structure that is lost
in Parkinson’s Disease
http://en.wikipedia.org/wiki/Midbrain
Brainstem
Medulla
Pons
Midbrain
Some
forebrain
structures
Senses: Information comes in the cranial nerves and eventually ends up in the cortex
Cranial Nerves
Table 4.4, page 87
Olfactory nerve:
Smell
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Optic nerve:
Vision
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Occulomotor
nerve:
Eye movement,
pupil constriction
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Trochlear nerve:
Eye movement
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Trigeminal nerve:
Skin senses from
face
Jaw muscles for
chewing and
swallowing
(muscles of
mastication)
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Abducens nerve:
Eye movements
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Facial nerve:
Taste
Facial
expressions
Crying
Salivation
Dilation of head’s
blood vessels
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Acoustic nerve:
Aka
vestibulocochlear
or statoacoustic
Hearing
Equilibrium
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Glossopharynge
al nerve:
Taste
Swallowing
Salivation
Throat
movements
during speech
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Vagus nerve:
Sensation from
neck and thorax
Control of throat,
esophagus,
larynx
Parasympathetic
nerves to
stomach,
intestines, etc
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Spinal accessory
nerve:
Aka Accessory
nerve
Neck and
shoulder
movements
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial Nerves
Table 4.4, page 87
Hypoglossal
nerve:
Muscles of
tongue
http://www.besthealth.com/besthealth/bodyguide/reftext/images/
cranial_nerves.jpg
Cranial nerve signs help determine
the location of a lesion in the brain
• Essential element in clinical neuroanatomy
• Neurological exam:
http://www.vhct.org/case1799/neurologic_
examination.shtml
• Example: patient is asked to stick out
tongue. If the tongue deviates to the left,
the lesion involves the nucleus of the left
hypoglossal nerve.
Nerve key
Nerve
Type of function
On
Optic
Some = sensory
Old
Olfactory
Say
Olympus
Occulomotor
Marry = motor
Towering
Trochlear
Money
Tops
Trigeminal
But = both (S&M)
A
Abducens
My
Fin
Facial
Brother
And
Acoustic*
Says
German
Glossopharyngeal
Bad
Viewed
Vagus
Boys
Some
Spinal accessory**
Marry
Hops
Hypoglossal
Money
* Acoustic-vestibulocochlear, stateocochlear
** Spinal accessory = accessory
Forebrain
•
•
•
•
•
•
•
Thalamus
Hypothalamus
Pituitary gland
Basal ganglia
Basal forebrain
Hippocampus
Limbic system
Thalamus:
Relay station for all sensory info on its way to brain (except
olfactory info)
Many specialized nuclei (ex: LGN, MGN…don’t have to know
these!)
Hypothalamus
Communicates with pituitary gland to alter hormone release
Involved in feeding, drinking, temperature regulation, sexual
behavior, fighting, arousal (activity level)…4 Fs
Pituitary gland
Endocrine gland (hormone producing)
Attached to base of hypothalamus by stalk
Makes and releases hormones into bloodstream
Basal Ganglia
Motor control, but also
memory and emotional
expression
Lose dopamine neurons in
SN  Parkinson’s Disease
http://www.uni.edu/walsh/basalganglia-2.jpg
thalamus.wustl.edu/ course/cbell6.gif
Lose dopamine neurons in
caudate & putamen 
Huntington’s chorea
Don’t memorize image!!! Just
understand that this is a very
complex system!
Basal forebrain
Anterior and dorsal to
hypothalamus
Important for arousal,
wakefulness, attention
http://memorylossonline.com/summer2003/glo
ssary/basalforebrain.jpg
Lose cells in nucleus
basalis  decreased
attention & intellect (AD,
PD)
Hippocampus
Memory formation
HM: temporal lobes
removed for intractable
epilepsy  no longer
formed new memories
http://www.hermespress.com/Perennial_Tradition/hippocampus.gif
http://www.umassmed.edu/bnri/graphics/crusiofig1.gif
Limbic System
important for motivated & emotional behaviors (eating,
drinking, sexual activity, aggressive behavior)
Ventricles
Contain
cerebrospinal fluid
(CSF)
CSF reabsorbed
into blood vessels,
so continuous
turnover
Protective
Reservoir for
hormones, nutrients
http://mywebpages.comcast.net/epollak/PSY255_pix/ventricles.PNG
Ventricle size can indicate
problems
• Enlarged ventricles
as in Alzheimer’s
patients (cell loss).
• Lack of ventricles
due to tumors etc.
Cortex
• 2 hemispheres
– Communicate via
corpus callosum &
anterior commisure
• 4 lobes
http://pegasus.cc.ucf.edu/~Brainmd1/brmodelc.gif
http://www.urmc.rochester.edu/neuroslides/slides/slide201.jpg
http://trc.ucdavis.edu/mjguinan/apc100/modules/Nervous/grosscns/images/brain10.jpg
6 laminae (layers of cells)
The lobes of the cortex
• Frontal
– Thinking
– Prefrontal cortex
• Planning
• Working memory
• Socially
appropriate
behavior
• Delayed-response
task
• Lobotomies
– Primary motor
cortex
• Broca’s aphasia
The lobes of the cortex
• Parietal
– Sensing
• Primary sensory
cortex
Homunculus
The lobes of the cortex
• Temporal
– Spoken language
comprehension
• Wernike’s aphasia
– Hearing
– Vision
• Movement
perception
• Face recognition
– Emotional
motivational
behavior
The lobes of the cortex
• Occipital
– Vision
• Primary visual
cortex
• Damage
causes
“cortical
blindness”
Evolution of Gene Related to
Brain's Growth
• A gene that helps determine the size of the human
brain has been under intense Darwinian pressure in
the last few million years.
• It has changed its structure 15 times since humans and
chimps separated from their common ancestor.
• Evolution has been particularly intense in the five
million years since humans split from chimpanzees
Changes in the architecture of the ASPM protein over the
last 18 million years are correlated with a steady
increase in the size of the cerebral cortex (2002) Dr.
Bruce T. Lahn at U. Chicago. A disrupted form of this
gene was identified as the cause of microcephaly
(people born with an abnormally small cerebral cortex).
Functions
• Forebrain
– the cool stuff (thinking, perceiving, big part of emotion)
• Midbrain
– sensory pathways
• Hindbrain
– motor control, reflexes (breathing, heart rate, etc)
Spinal Cord & Spinal Nerves
• Spinal cord
– Truly the pathway between body and mind
– Conducts impulses to and from the brain
– Carries out spinal reflexes
• Spinal nerves
– 31 pairs
– All are mixed nerves
Structure of the Spinal Cord
• Extends from the
foramen magnum to
the first or second
lumbar vertebra.
• Ends in the conus
medullaris
• Filum terminale
– Extends from conus
medullaris to sacral
vertebrae
• Cauda equina
– = filum terminale +
dorsal & ventral
roots from spinal
nerves that extendHuman Anatomy, 3rd edition
Prentice Hall, © 2001
below conus
Coverings of the Spinal Cord
• 3 layers called meninges
• Dura mater
– Outer layer
• Arachnoid
– Middle layer
• Pia mater
– Adheres tightly to the surface of the spinal
cord
Meninges of the Spinal Cord
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Meninges of the Spinal Cord
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Sectional Anatomy of the Spinal
Cord
• Inner part consists of gray matter
– Unmyelinated cell bodies, neuroglia, &
dendrites
– Organized into “horns”
• Outer part consists
of white matter
– Tracts of
myelinated fibers
– Ascending tracts
are sensory
– Descending tracts
are motor
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Example of Ascending Nerve Tracts
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Spinal Nerves
• Connect to the spinal cord via a dorsal and a ventral
root
• Dorsal root is sensory
– Contains a dorsal root ganglion
• Ventral root
is motor
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Spinal Nerves
• The roots unite into
the spinal nerve
• Spinal nerves exit
through
intervertebral
foramen
• Split into branches,
or rami.
– Dorsal ramus
– Ventral ramus
– Regions of skin
supplied by a
spinal nerve =
dermatomes (“skin
Human Anatomy, 3rd edition
slices”)
Prentice Hall, © 2001
Dermatomes
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Nerve Plexuses
• Plexus = “braid”
• Nerves supplying
the limbs form
plexuses when
they leave the
spinal cord
– Cervical plexus
– Brachial plexus
– Lumbosacral
plexus
• Lumbar plexus
• Sacral plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Cervical Plexus
• Formed by spinal nerves C1 – C5
– Nerves innervate the neck and shoulder
region
– Phrenic nerve to the diaphragm
Human Anatomy, 3rd edition
Prentice Hall, © 2001
•
Brachial
Plexus
Formed by spinal nerves C5 – C8 and T1
– Nerves innervate the arm and shoulder
• Radial nerve
• Ulnar nerve
• Median nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Brachial Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Lumbosacral Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Lumbar Plexus
• Formed by spinal
nerves T12 and L1 –
L4.
– Innervates the
medial and anterior
portions of the
thigh and lower
abdominal regions
– Lateral femoral
cutaneous nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Sacral Plexus
• Formed by spinal
nerves L4 and L5,
and S1 and S2
– Innervates the
posterior portion of
the hip, thigh, and
leg, and the genital
region
– Sciatic nerve
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Sacral Plexus
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Spinal Reflexes
• Reflexes are automatic responses to
stimuli
• Spinal reflexes result from the stimulation
of a spinal reflex arc.
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Basic Elements of a Reflex Arc
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Spinal Cord Injuries
• Can affect sensory perception; motor
paralysis
• Location affects severity of the injury
• Spinal compression results from
squeezing the spinal cord within the
vertebral canal
• Spinal transection is the severing of
the spinal cord
Human Anatomy, 3rd edition
Prentice Hall, © 2001
Spinal Cord Injuries
• Quadriplegia
• Paraplegia
http://www.apparelyzed.com/paralysis.html
Gracile fasc
Cuneate fasc
Gracile fasc Goll
Burdach Cuneate fasc
Flechsig
Gower
s
Lat sp-thal
Gracile fasc Goll
Burdach Cuneate fasc
Flechsig
C(p)
Rubro
Mona
kow
Gower
s
Lat sp-thal
c
R
T
v
Fasciculi proprii
Flechsig
C(p)
Gower
s
Lat sp-thal
c
R
T
v
Gel sub
Zona
spongiousa
N
p
C(p)
t
h
I-m
I-lat
c
R
T
v