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THE NERVOUS SYSTEM
Meet Patel and Auriana Semans
AP Biology
General Information
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Major components of the nervous system:
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Central Nervous System (CNS)- made up of spinal cord and brain
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Peripheral Nervous System (PNS)- made up of nerves
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Neurons- cells that make up the nervous system. They consist of
axon, 2 or more dendrites and cell containing nucleus.
Function of the Nervous System
The Nervous system has 3 main functions: sensory, integration and motor
>Sensory: it involves collection information from sensory receptors which
monitor internal and external conditions. These signals are then passed down
to central nervous system (CNS).
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>Integration: it involves processing of many sensory signals passed to CNS.
These signals are evaluated, committed to memory, discarded or used for
decision making. In other words its combining information from other/different
sources and analyzing them to make body run smoothly and effectively.
>Motor- once the network of interneurons is evaluated it releases hormone or
moves a part of the body to respond to stimulus.
Central Nervous System
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The Central Nervous System regulates our everyday function such as language,
emotion, creativity , expression and personality. The Central Nervous System
includes the brain and spinal cord.
Spinal cord serves signals between the brain and rest of the body. The function
of spinal cord is to connect large of peripheral nervous system to the brain and
serve as reflex center. The signal between spinal cord and body is passed
through spinal nerves.
Brain is responsible for integrating most sensory information and coordinating
body functions. Complex feelings such as emotions or thinking as well as
regulation of homeostasis is attributed to the brain. Brain receives its signals
from the spinal cord and 12 cranial nerves. Few examples of cranial nerves
are:
Optic nerve- carries visual information from eye to the brain.
Facial nerves- makes the muscle of face to make facial expressions.
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Contd…..
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Both spinal cord and brain consist of
Grey matter- contains cell bodies, dendrites and axon terminals of neurons.
Synapse mostly occurs in grey matter of the brain
White matter- made up of axons connecting different parts of grey matter to
each other.
The entire CNS is located inside Cerebrospinal Fluid and its essential to CNS as
it
1.Absorbs the shocks between the brain and the skull.
2. The brain and spinal cord float within Cerebrospinal fluid which reduces
their weight through buoyancy.
3. It helps maintain chemical homeostasis within the nervous system.
Peripheral Nervous System
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
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The main function of Peripheral Nervous System (PNS) is to connect CNS to
limbs and organs in the body. It consists of 12 pairs of spinal nerves and 31
pairs cranial nerves that help deliver signals throughout the body.
Peripheral Nervous System is divided into Somatic and Autonomic system.
Somatic Nervous System- its responsible for all voluntary movements as well
as processing sensory information that arrives from outside stimuli. Its like
passage way from environment to CNS.
Autonomic Nervous System- responsible for carrying internal body functions
such as breathing, heartbeat, digestive process etc. In other words it controls
subconscious parts of the body.
Contd…..

The Autonomic nervous system has two parts:
Characteristics
Sympathetic
When functioning?
emergencies
Digestive system
inhibits/slows down
Pupil
dilates
Heartbeat
accelerates
Breathing rate
increases
Parasympathetic
normal/everyday
promotes
constricts
slows down
slows down
Neurons

There are three basic parts of a neuron: the dendrites, the cell body and
the axon. The cell body contains the nucleus and most of the cellular
organelles. The dendrites are small tree like structures that pick up stimuli
from the environment. The axons send signals onto other neurons or cells in
the body.
Types of Neurons
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There are 3 types of neurons:
Sensory neurons - send information from the sense organs (outside) to the
C.N.S. They have long dendrites and short axons.
Motor neurons - send information from the C.N.S to the muscles. Causing the
muscles to move. They have short dendrites and long axons.
Interneurons - connect different neurons together, send information between
neurons. They have short dendrites and short axons.
How do Neurons transmit and receive
information??


The dendrites receive the information from sensory cells which then is
passed down to the cell body where the information is evaluated and on to
the axon. Once the information is at axon it travel downs length of axon in
form of electrical signal known as action potential.
Once the electrical impulse has reached end of axon it must be transmitted
to another neuron or cell through synapse. If neuron is adjoined to the
dendrites of another neuron electrical signals are instantaneously sent
allowing signal to continue its path. However in some cases of long distance
signaling neurotransmitters are used as they are chemical messengers that
are released from axon to cross synaptic gap and bind to receptor sites of
other neurons.
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Example of synapse using electrical signals as the dendrites of another
neuron are adjoined at end of axon so signal can keep flowing through.
References
1.
2.
3.
4.
"Nervous System." InnerBody. N.p., n.d. Web. 09 Apr. 2015.
Overview of the Autonomic Nervous System." : Autonomic Nervous System
Disorders: Merck Manual Home Edition. N.p., n.d. Web. 09 Apr. 2015.
Cherry, Kendra. "What Is a Neuron? Building Blocks of the Nervous
System." N.p., n.d. Web. 09 Apr. 2015.
"Peripheral Nervous System: Definition, Function & Parts |
Study.com."Study.com. N.p., n.d. Web. 09 Apr. 2015.
Quiz Questions
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1. Which nervous system controls the involuntary movements in body?
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2. The nervous system is made up of cells called__________
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3. What kind of neurons transmits impulses
a. towards the C.N.S.
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4. Identify the 3 parts of the neuron
b. away from the C.N.S
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5. The space between an axon of one neuron and the dendrite of another
neuron is called a(n) _____.
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synaptic cleft
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node of Ranvier
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internodes
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synapse
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synaptic terminal
Answers!!
1. Autonomic Nervous System
2. Neurons
3. a. sensory neurons
4. a. axon
5. D. Synapse
b. dendrites
b. motor neurons
c. nucleus