Central Nervous System
CHAPTER 13
Basic parts of the CNS
 Brain
 Spinal Cord
Brain
 Basic Parts :
 Cerebrum
 Cerebellum
 Brain Stem
 Cerebral Cortex
Sulcus- valley (Fissures)
Gyrus- Mountains or raised areas
Sulcus and Fissures of the Brain
Cerebrum
 Cerebral Cortex
 Outer surface or covering of the cerebrum Gray Matter.
Highest center of brain – where decisions are made. Only site
of conscious awareness
 Receives and interprets sensory input, if it doesn’t reach the
cerebral cortex you won’t know what is going on.
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Brain death- usually means the cortex has been wiped out
Amount of cortex correlates with the intellectual capacity,
reptiles have very little compared to humans, rats do not have
convuluted cortex
Cerebral cortex
Cerebral Cortex - thin layer of gray matter
that is the outermost portion of cerebrum
(the part with all the wrinkles)
Cerebrum cont…
Central Sulcus – actually intersects the medial
longitudinal fissure.
Lobes of Brain
Frontal lobe- intellectual power
Temporal Lobe- Primarily hearing and speech
Occipital Lobe- receive and interprets visual
information
Parietal lobe- Sensory reception and processing
Lateral fissures of the brain
Midsaggital view
 Inside the hemispheres of the brain
 Thalamus- every bit of sensory information going
to cortex must go through the thalamus except
olfactory sense
 12 Cranial nerves on base of brain
Midsaggital brain
Hypothalamus
 Hypothalamus- beneath Thalamus
 Small but preforms many functions of greatest importance for
survival and enjoyment
 Links mind and body
 Links nervous to endocrine
 Regulates and coordinates autonomic behavior
 Regulates appetite, arousal, body temperature,
Base of brain
 Putamen and Globus Pallidus- Make up the Lentiform
nucleus which is the part of the basal ganglia responsible
for voluntary motor movement. (Effected in Parkinsons)
 Internal Capsule- all information to and from the
cortex pass through this capsule. Frequent site of stroke.
 Fibers out of thalamus pass through the internal capsule
to the cortex. Sensory thru thalamus
 Motor fibers descend thru internal capsule and then to
spinal cord for reaction.
3 types of fibers in Cerebrum
 Projection fibers- connect the cerebral cortex with
the CNS
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To cortex are sensory fibers
From cortex are motor fibers all thru the internal capsule
Fanning out of fibers from internal capsule to cortex are called
Corona Radi
 Association Fibers- connect two portions of the
cortex in the same hemisphere. Ie. Frontal lobe to
occipital lobe on the right.
Fiber types cont…
 Commisural fibers- connect corresponding
structures in different hemispheres. 3 sets:
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Corpus callosum
Anterior commisures
Posterior commisures
Without connections the 2 hemispheres are not
communicating.
Functional and Structural Areas of the Cerebral
Cortex
Sensory Fiber Distribution
Cerebellum (add to your notes)
 Connected to cerebrum
by 3 peduncles
 Dentate nucleusinfluences motor cortex
 Functions of cerebellum
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Coordination of motor
movement
Maintains balance
Controls posture
Brain Stem
Mid brain
 Controls visual and auditory reflexes
 Pineal body- prepare body for sleep or awake state-
produces melatonin
 Cerebral Peduncles- carry motor fibers from cortex
to spinal cord. Peduncles are the only thing
connecting the cerebellum to the cortex.
 Medulla- descending motor fibers.
Coverings of the Brain and Spinal Cord
 Outer Covering – Bone, skull and vertebrae
 Inner Coverings- Meninges of the cord continue
inside the spinal cavity beyond the end of the spinal
cord.
 Meninges- 3 membranous layers
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DURA MATER- tough protection from outside. Connective
tissue against bone. Doesn’t protect against trauma but
separates the brain and spinal cord from outside world. Has 3
important extensions

Falx Cerebri- between the two cerebral hemispheres. Contains
dural sinuses that function as veins, collecting blood from brain
tissues for return to heart. Also Superior saggital sinuses found in
cerebrum.
Meninges cont…
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Falx Cerebelli- separates the two hemispheres of the
cerebellum.
Tentorium Cerebelli- between cerebrum and cerebellum
 Arachnoid Mater- delicate cobwebby layer between
the dura mater and pia mater
 Pia Mater- Innermost transparent layer: adheres the
outer surface of the brain and SC, forms a slender
filament called the filum terminale, at level of the
sacrum.
Meninges
Cerebrospinal Fluid
 Functions:
 Provide a supportive, protective cushion
 Reservoir of circulating fluid, which is monitored by the brain
to detect changes in the internal environment.
 Fluid Spaces:
 CSF-found within the subarachnoid space around the brain
and spinal cord and within the cavities and canals of the brain
and spinal cord
 Ventricles- fluid filled spaces within the brain; four ventricles
within the brain
CSF- Ventricles of the Brain
Issues with CSF
 Hydrocephally- blockage of blood flow of CSF. No
communicating, fluid goes in but releases and
insignificant amount.
 Intracranial pressure results between the dura and
pia mater. Meningitis also causes this increase in
pressure. Signs include:
Loss of consciousness
 Pupils different sizes
 Pass out
 Headache
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 Treatment- drain CSF out of ventricle with a shunt to
another part of body- usually stomach.
Spinal Cord
 Structure of the spinal cord
 Oval shaped
 Anterior Median Fissure
 Posterior median sulcus
 Nerve roots laterally
Fibers of dorsal nerve root
 Carry sensory information into SC
 Dorsal Root ganglion- cell bodies are unipolar and make up gray
matter in dorsal root
 Fibers of Ventral Root
 Cary motor information out of spinal cord
 Cell bodies of multipolar, motor neurons are in the gray matter
of SC
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SC Anatomy Continued…
 Interneruons are located in the spinal cord’s gray
matter core
 Spinal nerve- single mixed nerve on each side of the
SC where the dorsal and ventral nerve roots join
together.
Gray Matter
 Extends the length of the cord
 Consists Primarily of cell bodies of interneurons and
motor neurons
 Looks like an H with the limbs being called anterior,
posterior, and lateral horns of gray matter.
White matter
 Surrounds gray matter and is subdivided in each half
on the cord into three funiculi: anterior posterior and
lateral horns of gray matter
 Each funiculus consists of large bundle of axons
divided into tracts
 Names of spinal tracts indicate the location of the
tract, the structure in which the axons originate and
the structure which they terminate.
Functions of the SC
 Routes of conduction to the brain
 Organized by structure and function
 Ascending Tracts:
 Lateral spinothalamic
 Anterior spinothalmic
 Fasciculus, gracilis and cuneateus
 Spinocerebellar
 spinotectal
Tracts continued
 Descending tracts:
 Lateral corticospinal tract
 Anterior corticospinal tract
 Reticulospinal tract
 Rubrospinal tract
 Tectospinal tract
 Vestibulospinal tract
CONSCIOUSNESS
 State of awareness of one’s self, one’s
environment, and other human beings (Figure
13-21)
 Depends on excitation of cortical neurons by
impulses conducted to them by the reticular
activating system
 Two current concepts about the reticular
activating system
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Functions as arousal system for the cerebral cortex
Functioning is crucial for maintaining consciousness
LANGUAGE
 Ability to speak and write words and understand
spoken and written words
 Speech centers: areas in the frontal, parietal, and
temporal lobes
 Left cerebral hemisphere contains speech centers in
approximately 90% of the population; contained in
either the right hemisphere or both in the remaining
10%
 Aphasias: lesions in speech centers
EMOTIONS
 Subjective experiencing and objective expressing of
emotions involve functioning of the limbic system (Figure
13-22)
 Limbic system: also known as the emotional brain
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Most structures of limbic system lie on the medial surface of the
cerebrum (cingulate gyrus and hippocampus)
Have primary connections with other parts of the brain, such as the
thalamus, fornix, septal nuclei, amygdaloid nucleus, and
hypothalamus
MEMORY
 A major mental activity
 Cortex is capable of storing and retrieving both
short- and long-term memory
 Temporal, parietal, and occipital lobes are among the
areas responsible for short- and long-term memory
 Structural changes in the neural pathways of the
cerebral cortex store long-term memories
 Limbic system plays a key role in memory