The nervous system is composed of the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord, which act as the main control centers. The brain is divided into the cerebrum, cerebellum, and brain stem. The PNS connects the CNS to the rest of the body and is composed of nerves and ganglia. It can be subdivided into sensory and motor nerves. Together, the nervous system allows the body to coordinate activities, sense the environment, and produce responses.

1.  A physically connected network of cells, tissues and organs that
allow us to communicate with and react to the environment and
perform life activities. Main Functions are;
 Sensing the world
--Vision, Hearing, Smell, Taste and Touch
 Transmitting information
 Processing information
 Producing a response

2.  The functional unit of the nervous system is the nerve cell,
known as the NEURON.
 They send electrochemical messages around the body

3.  Dendrites : Receive chemical signals from neighboring cells.
 Cell Body/Soma: contains the nucleus & organelles
 Axon: long extension that carries electrical messages away
from the body to the terminal axons
 Terminal Axons: passes the signal to the next cell.
 Myelin sheath: Protective covering for axon

4.  Supportive cell in the central nervous system which
surround neurons and provide support for and insulation
between them.
 Bringing the cells of nervous tissue together structurally and
functionally
 Unlike neurons, glial cells do not conduct electrical
impulses.

5. a) Astrocytes: star shaped cells found between neurons and blood
vessels. They are the most abundant glial cells.
Function: structural support, transport of substance between blood
vessels and neurons.
b) Microglial cells: small ovoid cells.
Function: structural support and phagocytosis (immune protection).

6. c) Ependymal cells: cuboidal or columnar shaped cells.
Function: form a porous layer through which substances diffuse between
the interstitial fluid and the cerebrospinal fluid.
d) Oligodendrocytes: resemble astrocytes but have less processes and
arranged in rows along nerve fibers.
Function: produce myelin sheet within the brain and spinal cord.

7.  The human nervous system consists of the Central Nervous System
(CNS) and the Peripheral Nervous System (PNS).
1. CNS is composed of the brain (located in the cranial cavity) and the
spinal cord (located in the vertebral cavity), which serve as the main
control centers for all body activities.
2. PNS is composed of nerves derived from the brain and spinal cord (12
pairs of cranial nerves and 31 pairs of spinal nerves), which serve as
linkage between the CNS and the body.

8. 2. PNS can be subdivided into Sensory (afferent) nerves and
Motor (efferent) nerves.
 Sensory nerves send nerve impulse from the body to CNS, while motor
nerves send impulse from CNS to effector organs.
 Motor (efferent) nerves are divided into the
 Somatic Nervous System (SNS) which regulates the voluntary
contraction of skeletal muscles and
 Autonomic nervous system (ANS) which regulates the involuntary
control of smooth, cardiac muscles and glands.
o Finally, the ANS can be divided into
 Sympathetic branch where general sympathetic nerves stimulate
activities of the effector organs
 Parasympathetic branch where parasympathetic nerves inhibit
activities of the effector organs.

10. Central Nervous System (CNS)
 Consists of brain and spinal cord
 Functions:
Acts as body’s control center
and coordinates physiological
activities
Receives sensory signals and
determines appropriate
response
Stores memory
Carries out thought and so
on.

11.  Menings:
1. Body membranes that cover the brain and spinal cord forprotection and
nourishing purposes.
2. Consists of 3 layers: (each layer is a "menix")
a) Dura mater : outermost layer that attachesthe brain to cranial bones,
and the spinal cord to vertebrae. Made upof fibrous connective tissue
that protects the CNS.
a) Arachnoid mater : middle layer made up of thin membranes that
lack blood vessels. It reabsorbs cerebrospinal fluid (CSF).
b) Pia mater : innermost layer made of thin membranes that contain
capillaries for providing nourishment to the brain and spinal cord.
Forms capillary networks called plexuses which produce CSF .

13.  The largest organ in the nervous system; composed of about 100 billion
neurons
 Divided into 3 main regions: Cerebrum, Cerebellum, and
the Brain Stem.
 Contains spaces called ventricles where choroid plexuses of pia
mater produce cerebrospinal fluid (CSF), and these ventricles allow
CSF to circulate around the brain and into the spinal cord (through the
central canal).

15.  Cerebral Cortex (outer region) is made of gray matter (unmyelimated
neurons) which contains up 75% of all neurons in the nervous system,
while Cerebral Medulla (inner region) is made of white matter
(myelinated neurons).
 Consists of left and right hemispheres, created by the longitudinal
fissure at the center of cerebrum, and are connected by the corpus
callosum.
 Its surface is marked by ridges called convolutions (gyri) which are
separated by grooves called sulcus (or fissure, if the grooves are
deeper).

17. 1. Frontal lobe controls skeletal
muscle movement and
intellectual processes.
2. Parietal lobe controls
sensations and speech.
3. Temporal lobe controls hearing
and memory.
4. Occipital lobe controls vision.

18. BRAIN STEM
 Consists of mainly four
parts:
 Medulla Oblongata
 Pons
 Midbrain
 Diencephalon

20. BRAIN STEM
 The Medulla Oblongata
 Direct rostral extension of the spinal cord
 Resembles the spinal cord both in organization and function
 Regulates blood pressure and respiration
 The Pons
 Relay information about movement and sensation from the
cerebral cortex to the cerebellum.
 The dorsal portion of the pons contains structures involved in
respiration, taste and sleep.

21. BRAIN STEM
 The Pons
 Relay information about movement and sensation from the
cerebral cortex to the cerebellum.
 The dorsal portion of the pons contains structures involved in
respiration, taste, and sleep.

22. BRAIN STEM
 The Midbrain
 Provide important linkages between the components of motor
systems
– The cerebellum, the basal ganglia, and the cerebral
hemispheres
 Also contains components of the auditory and visual systems.
 Several regions ‐ connected to the extra-ocular muscles of the eye
 The major pathway for controlling eye movements.

23.  Diencephalon
 Mainly consists of Thalamus and Hypothalamus.
 Thalamus- It is a major relay center to direct nerve impulses from
various sources to the proper destinations.
 Hypothalamus (an important area for regulating homeostatic
activities, such as hunger, thirst, sex drive, and even addictions)
 Other parts of diencephalon
 Optic tracts and Optic chiasma that is formed by optic nerves crossing
over.
 infundibulum- site of attachment of pituitary gland
 Pituitary gland- hangs from the floor of hypothalamus
 Pineal gland- produce melatonin that controls sleep - awake cycle.
BRAIN STEM

24. Cerebellum
The cerebellum is a brain structure that has an important role in motor
control. Particularly, it is active in the coordination, precision and timing
of movements, as well as in motor learning.
The cerebellum is located at the back of the brain. It lies at the same
level of the pons of brain stem.
The cerebellum consists of two hemispheres. Like other structures in the
central nervous system, the cerebellum consists of grey matter and white
matter:
 Grey matter– located on the surface of the cerebellum. It is tightly
folded, forming the cerebellar cortex.
 White matter– located underneath the cerebellar cortex.

25.  A long nerve cord that begins at the
foramen magnum and ends at the
sacral region.
 In general, the location of the spinal
nerve corresponds with the location of
the effector organ (e.g. cervical nerves
connect to muscles and glands on the
head, face, and neck).
Spinal Cord Nerves

26.  Spinal nerves are divided into 31
segments (named after the vertebral
regions), each segment gives rise to
a pair of spinal nerves.
 Most spinal nerves form networks
called plexuses.
 C1 to C4 from cervical plexus which
serves the head, face and neck.
 C5 to T1 from brachial plexus which
serves the shoulder, arm and hands.
 T 2 to T11 do not form any plexus.
 T12 to S5 form lumbosacral plexus
which serves the lower body and
lower limbs.
 Coccygeal nerves do not form any
plexus.
Spinal Cord Nerves