The document summarizes the anatomy and functions of the central nervous system and its parts. It describes the three meninges (dura mater, arachnoid mater, pia mater) that protect the CNS. It then discusses the structures and functions of the brainstem, cerebellum, diencephalon, and cerebral cortex. It also outlines the somatic sensory and motor pathways, as well as the autonomic nervous system including its sympathetic and parasympathetic divisions.

1. Inside:
 CNS and its
parts
 PNS and its
parts

2. Three Meninges
The meninges is the system of membranes which envelops the central nervous system. In mammals, the
meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary
function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.
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Dura mater
The dura mater [Latin: 'tough mother'] (also rarely called meninx fibrosa or pachymeninx) is a thick,
durable membrane, closest to the skull. It consists of two layers, the periosteal layer which lies closest to
the calvaria (skull), and the inner meningeal layer which lies closer to the brain. It contains larger blood
vessels which split into the capillaries in the pia mater. It is composed of dense fibrous tissue, and its
inner surface is covered by flattened cells like those present on the surfaces of the pia mater and
arachnoid. The dura mater is a sac which envelops the arachnoid and has been modified to serve several
functions. The dura mater surrounds and supports the large venous channels (dural sinuses) carrying
blood from the brain toward the heart.
The dura has four areas of infolding which include :
Falx cerebri, the largest, sickle-shaped; separates the cerebral hemispheres. Starts from the frontal crest
of frontal bone and the crista galli running to the internal occipital protuberance.
Tentorium cerebelli, the second largest, crescent-shaped; separates the occipital lobes from cerebellum.
The falx cerebri attaches to it giving a tentlike appearance.
Falx cerebelli, vertical infolding; lies inferior to the tentorium cerebelli, separating the cerebellar
hemispheres.
Diaphragma sellae, smallest infolding; covers the pituitary gland and sella turcica.
[edit]Arachnoid mater
The middle element of the meninges is the arachnoid mater, so named because of its spider web-like
appearance. It provides a cushioning effect for the central nervous system. The arachnoid mater is a
thin, transparent membrane. It is composed of fibrous tissue and, like the pia mater, is covered by flat
cells also thought to be impermeable to fluid. The arachnoid does not follow the convolutions of the
surface of the brain and so looks like a loosely fitting sac. In the region of the brain, particularly, a large

3. number of fine filaments called arachnoid trabeculae pass from the arachnoid through the subarachnoid
space to blend with the tissue of the pia mater.
The arachnoid and pia mater are sometimes together called the leptomeninges.
Pia mater
The pia mater [Latin: 'soft mother'] is a very delicate membrane. It is the meningeal envelope which
firmly adheres to the surface of the brain and spinal cord, following the brain's minor contours (gyri and
sulci). It is a very thin membrane composed of fibrous tissue covered on its outer surface by a sheet of
flat cells thought to be impermeable to fluid. The pia mater is pierced by blood vessels which travel to
the brain and spinal cord, and its capillaries are responsible for nourishing the brain.
Spaces
The subarachnoid space is the space which normally exists between the arachnoid and the pia mater,
which is filled with cerebrospinal fluid.
Normally, the dura mater is attached to the skull, or to the bones of the vertebral canal in the spinal
cord. The arachnoid is attached to the dura mater, while the pia mater is attached to the central nervous
system tissue. When the dura mater and the arachnoid separate through injury or illness, the space
between them is the subdural space.
meninges /me·nin·ges/ (mĕn-in´jēz) sing. meninx [Gr.] the three membranes covering the brain and
spinal cord: dura mater, arachnoid, and pia mater.menin´geal
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Spinal cord
The spinal cord in the simplest part of the central nervous system and is connected to the brain by the
delicate brain stem and contained within the spinal cavity. It is an oval shaped cylinder that tapers
slightly as it descends with two bulges as labeled in the diagram. The spinal cord mediates simple
reflexes and is extremely delicate and important. It provides conduction paths to and from the brain
called ascending tracts and descending tracts. The sensory impulses go up towards the brain and the

4. motor impulses come back down. It also is the reflex center for all spinal reflexes. IT switches impulses
from afferent to efferent neurons. ©8
Nerve roots
There are 31 spinal nerves connected to the spinal cord, numbered by the level they emerge from the
spinal cavity. These attach by 2 types of short roots, a ventral nerve root or a dorsal nerve root. Vertral is
anterior and dorsal is posterior. The dorsal is easily recognized by the spinal ganglion. The ventral roots
carry motor neurons to effectors, also known as muscles and glands. The dorsal root carry information
from receptors in the peripheral nerves. ©8

5. ©12
Function of the Brainstem: It performs sensory, motor, and reflex functions. The
spinothalamic tracts that pass through the brain stem are on the way to the thalamus.
Nuclei in the medulla have reflex centers like cardiac, vasomotor, and respiratory. Other
centers in the medulla are responsible for nonvital refluxes such as vomiting. The pons
contains centers for reflexes mediated by the 5th, 6th, 7th, and 8th cranial nerves. Finally,
the midbrain also contains reflex centers for certain cranial nerves such as eye
movements mediated by the 4th cranial nerve.

6. Functions and Structure of the Cerebellum
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Function: The cerebellum performs three general functions. It acts with the cerebral
cortex to produce movements by coordinating the groups of muscles. It helps control
posture by functioning below the level of consciousness to ensure smooth and steady
movements. It also controls skeletal muscles to maintain balance.

7. Structure and Function of the Diencephalon
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Function: The functions of the thalamus are the part it plays in the
mechanism responsible for sensations. Impulses from receptors upon
reaching the thalamus produce conscious recognition of the sensations. It
plays a part in the mechanism responsible for emotions by associating
sensory impulses with feelings. It plays a part in the alerting mechanism,
and the mechanism that produces complex reflex movements. The
functions of the hypothalamus are that it functions as a high autonomic
center and as a relay station between the cortex and the lower autonomic
centers. It synthesizes hormones, performs endocrine functions, essential
role in maintaining the waking state, appetite mechanism, and part of the
mechanism responsible for maintain body temperature.

8. Cerebral Cortex Structure and Function
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Functions: Functions of the cerebral cortex include: sensory functions being somatic or
“general senses”, motor functions such as movement of individual muscles, and
integrative functions such as consciousness, language, emotions, and memory. All the
parts of the cerebral cortex work together and individually to help with the mechanisms
that control many parts of the body.

9. The somatic nervous pathway is made up of nerves that connect to the skin, sensory organs and all
skeletal muscles. The system is responsible for nearly all voluntary muscle movements as well as for
processing sensory information that arrives through external stimuli, which are things like hearing, touch
and sight.
The somatic motor pathways include smooth muscle, cardiac muscle, and glands. The two divisions
would be sympathetic division and parasympathetic division.
Parietal lobe
Frontal lobe
Occipital lobe Thalamus
Cerebellum

10. Cerebrum
ain
Cervical Cerebellum
Enlargement
Spinal
Nerve
Cord
Root
ain
ain
Membranous covering
(meninges)
Lumbar Enlargement
Filum terminale

11. The Cerebral Cortex is described the “gray”
matter that covers the entire brain. The cerebral
has a very important function of responsible for
sensing and interpreting input from various sources
and maintaining cognitive function. Sensory
functions interpreted by the cerebral cortex include
hearing, touch, and vision. Cognitive functions
include thinking, perceiving, and understanding
language. For additional information on the
cerebral cortex visit the Cerebral Cortex and
Cerebral Cortex Lobes pages.
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Somatic Sensory and Motor Pathways
Somatic Sensory pathways send impulses to the cerebral
cortex for it to perform its sensory functions. Most impulses
sent to the cerebral cortex end up going through three levels
through three pools of sensory neurons primary, secondary,
and tertiary. Primary sensory neurons conduct from the
periphery to the central nervous system. Secondary sensory
neurons conduct from the cord or brainstem up to the
thalamus. Tertiary neurons conduct from the thalamus to the
postcentral gyrus which extend through the portion known as
the internal capsule to the cerebral cortex. Somatic Motor
pathways are there for the cerebral cortex to perform its
motor functions. Impulses are from the motor areas and are
sent to the skeletal muscles .

12. Brain
Pg. 414 & 417
Sensory to back of head, front
of neck, and upper part of
Cervical plexus found deep shoulder; motor to numerous
Cervical Plexus neck muscles
within the neck. Brachial
Plexus found deep within the
shoulder. Lumbar Plexus;
network of nerves located in
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the Lumbar region of the back
near the psoas muscle. Fibers
from the fourth and fifth
lumbar nerves and the first
four sacral nerves form the
Sacral Plexus. (LUMBOSACRAL
PLEXUS) when together. Last
Sensory to anterior abdominal wall,
sacral nerve, along with a few Lumbar Plexus
external genitalia; sensory to outer part
fibers from S4 joins with the
of thigh.
coccygeal nerve to form a
small coccygeal plexus. Nerves
innervate the floor of the Sacral Plexus Motor to quadriceps, Sartorius, and
pelvic cavity. Iliacus muscles. Motor to adductor
muscles of the thigh and medial side
of lower leg. Motor to calf and leg
Coccygeal Plexus muscles (skin of calf and foot).
Sensory to lateral surface on leg, and
dorsal surface on foot. Motor to
muscles on the back of the thigh.
Motor to buttock muscles, sensory to
skin of buttocks, posterior surface of
thigh and leg.

13. Pg. 418- 419 Dermatomes- “Each skin surface area supplied by sensory fibers of a given spinal nerve is
called a dermatome, name that means “skin section.” Image (4)

14. Pg. 421 Myotomes- “skeletal muscle or group of muscle’s that receives motor axons from a given spinal
nerve. “ Image (5)

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Pg. 421 Brain
Olfactory Nerve- sense of
smell
Facial Nerve- facial
expressions, secretion of
saliva, and tears.
Trigeminal Nerve- sensations
of head and face, chewing
Vestibulocochlear Nerve- movements.
Balance or equilibrium
sense.
Glossopharyngeal Nerve-
Brain Stem
Vagus Nerve- Sensations of tongue,
Sensations and swallowing movements, aid
movements. Slows in reflex control of blood
heart, increases pressure.
peristalsis.
Hypoglossal Nerve- tongue Accessory Nerve – Shoulder
movements movements, turning movements of
head, movements of viscera, and
voice production.

16. Afferent vs. Efferent
Function:
 Carries information into the Central Nervous System
 Afferent nerves in the Somatic Sensory system, feedback information detected by
receptors in skin, skeletal muscles and sense organs.
 In the ANS feedback information regarding the autonomic control of the viscera.
Purpose:
 Help us maintain homeostasis by sensing changes in internal and external environment
Above is a chart of the efferent and afferent and the difference between
them. ©7

17. Autonomic Nervous System
Function: Pathways in the ANS carry
information to the visceral effectors which are
the smooth muscles, cardiac muscles, and

18. glands. It powers itself without our conscious
knowledge. It has two efferent divisions
including the sympathetic and
parasympathetic division. They are made up
of autonomic nerves, ganglia, and plexuses.
The parasympathetic division is the “rest and
repair” division that uses acetylcholine it’s
transmitter to slow the heartbeat, promote
digestion etc. Parasympathetic stimulations
have different effects on effectors such as
constriction of bronchioles and contraction of
urinary bladder. The sympathetic division
opposes the parasympathetic impulses which
would for example, raise the heartbeat.

19. Sympathetic stimulations have effects like
dilation of bronchioles and relaxation of
urinary bladder. As a whole, the ANS
functions to regulate autonomic effectors to
maintain homeostasis. For example, X Vagus
goes to the heart and controls the heartbeat,
while the IX Glossopharyngeal goes to the
lungs and control respiratory actions.

20. Sympathetic and Parasympathetic Systems
Sympathetic divisions consist of neural pathways separate from the
parasympathetic pathways. Sympathetic impulses stimulate an effector while
parasympathetic impulses tend to inhibit it. Sympathetic division’s main purpose
is to serve as a responder to stressful/increased demanding situations and the
parasympathetic division’s main purpose is to serve as a non-emergency, routine
body maintenance function.
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Sympathetic is like an ambulance Parasympathetic is like a doctor’s visit
(Responding to immediate emergencies) (Routine checkup)