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MODULE 05: THE NERVOUS SYSTEM: IT KEEPS GETTING ON MY NERVES
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QUESTION: NERVOUS SYSTEMMODULE 05
THE NERVOUS SYSTEM:
IT KEEPS GETTING ON MY
NERVES
SECTION 01: ORGANIZATION OF THE NERVOUS
SYSTEM
FUNCTIONS OF THE NERVOUS SYSTEM As you have just learned, we can simplify the function of
the nervous system to gathering information from the
The nervous system is the body’s control and external or internal environment, integrating multiple signals
communication system. It is a complex system that controls to create a complete picture, and executing a motor
both voluntary and involuntary processes. The functions of output response to the environment.
the nervous system can be simplified into three steps:
sensory input, integration, and motor output. What are some examples of sensory input a person may
have received that results in leg movement?
Some possible examples are:
· Seeing a soccer ball
· Navigating a set of steps
· Moving out of the way of a car
ORGANIZATION OF THE NERVOUS SYSTEM
As the nervous system is quite complex, it is important for
anatomists to understand its organization. The nervous
system is divided into two principal subdivisions: the central
nervous system (C N S) and the peripheral nervous system
(P N S).
Central Nervous System (C N S)
The central nervous system (C N S) is made up of the brain
1. Sensory Input and spinal cord. The C N S is commonly referred to as the
The nervous system functions to allow us to gather vital ‘control center’ of the body.
sensory information about our external environment (e.g.
touch, temperature, sound) and internal environment (e.g. Peripheral Nervous System (P N S)
distension of the urinary bladder). The peripheral nervous system (P N S) is composed of all the
Sensory input from the environment is detected by sensory nerves outside of the brain and spinal cord. These include
nerves and travels through the body to communicate with the cranial nerves, spinal nerves, the autonomic nervous
other nerve cells. system and the special sense organs.
2. Integration
The nervous system needs to be able to put together all of OVERVIEW OF THE NERVOUS SYSTEM
the incoming sensory signals in order to create a complete
picture of the environment. Integration incorporates
multiple simultaneous signals. For example, the brain is able
to integrate different sound signals from each ear to
determine the location of a sound’s source. Integration
occurs in the brain or spinal cord.
3. Motor Input
Once sensory input has been integrated, the nervous
system functions to produce an appropriate response by
sending motor output signals through motor nerves. These
nerves communicate signals from the brain and spinal cord
to the skeletal, cardiac, or smooth muscle of the body, VIDEO: take notes
causing them to contract or relax.
, Briefly explain one similarity of efferent and afferent DIRECTION OF A NERVE IMPULSE
neurons.
Efferent and afferent neurons are part of the P N S and Neurons allow organs within the body to communicate with
function to carry electrical signals. one another through the rapid transduction of electrical
signals known as nerve impulses. It is important to note that
Briefly explain one difference between efferent and afferent a nerve impulse is unidirectional - only occurring in one
neurons. direction.
Efferent neurons are part of the motor division and carry Signals travel from the dendrites to the cell body through
signals away from the C N S. Afferent neurons are part of the axon to reach dendrites of adjacent neurons or target
the sensory division and carry signals to the C N S. organs. Signals do not travel in the opposite direction.
Which division of the nervous system would be responsible CLASSIFICATION OF NEURONS
for directly contracting the trapezius muscle?
Motor Division of the P N S Not all neurons look exactly the same. Neurons can be
classified based on the number of cellular processes
(dendrites and axon) that extend from the cell body.
SECTION 02: HISTOLOGY OF NEURAL TISSUE
1. Pseudounipolar (Unipolar)
Pseudounipolar neurons have one cellular process that
There are two principal cell types in the nervous system:
splits into a dendrite and an axon.
neurons and supporting cells.
General sensory nerves are an example of pseudounipolar
nerves.
NEURONS
You may be familiar with neurons, also known as nerve
cells. These cells are excitable and can generate and
transmit rapid electrical signals to other neurons.
The signal begins (input) at the dendrite, then travels towards the
cell body located in the middle of the neuron where it travels into
the cell body. The signal then exits the cell body to continue
travelling in the same direction along the axon (output).
NEURON STRUCTURE 2. Bipolar
Neurons are the structural units of the nervous system. Bipolar neurons are only found in special senses, like sight
Neurons allow for communication within and between the and hearing.
C N S and P N S.
Bipolar neurons have one dendrite and one axon that
All neurons have similar
extend directly from the cell body. Unlike pseudounipolar
structures:
neurons, bipolar neurons have two distinct processes.
• Cell body
• Cytoplasmic
Processes
– Dendrites
– Axon
1. CELL BODY The signal begins (input) at the dendrite and travels along the
The cell body is also called the ‘soma’ and houses the dendrite to meet the cell body. The signal then exits the cell body
nucleus and other organelles. The cell body functions to to continue travelling in the same direction along the axon
transfer electrical signals from the dendrites to the axon. (output).
2. DENDRITES 3. Multipolar
Dendrites receive the neuronal signal from other neurons Multipolar neurons have multiple
and transfer those signals to the cell body. dendrites and one axon,
summing to three or more cellular
3. AXON processes. The number of
There is only one axon per neuron. Axons carry the signal dendrites is variable.
from the cell body to the axon terminals, where the signal is
then transferred to other neurons or organs. Multipolar neurons are the most
common types of neurons. Motor
neurons are an example of
multipolar neurons.
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