Intro to the Nervous System
Notice: To optimize your learning in this course, we advise that you complete the labs and
modules as indicated in the BIOD 152 Lab Schedule.
The nervous system receives and processes infor
...
Intro to the Nervous System
Notice: To optimize your learning in this course, we advise that you complete the labs and
modules as indicated in the BIOD 152 Lab Schedule.
The nervous system receives and processes information and sends out signals to the muscles and
glands to elicit an appropriate response. In this way, the nervous system integrates and controls
the other systems of the body.
In the human nervous system, the central nervous system (Figure below) includes the brain and
the spinal cord (dorsal nerve cord), which lie in the midline of the body.
The skull protects the brain and the vertebrae protect the spinal cord. The central nervous system
can send signals or impulses to and receive impulses from the peripheral nervous system. The
peripheral nervous system includes all nerves not in the brain or spinal cord which are the cranial
nerves that connect directly to the brain and the spinal nerves which project from either side of
the spinal cord. The peripheral nervous system connects all parts of the body to the central
nervous system and can be divided into a sensory or afferent division and a motor or efferent
division. The peripheral nervous system receives impulses from the sensory organs via the
afferent division and then relays signals or impulses from the central nervous system to muscles
and glands via the motor or efferent division. The efferent division can be further divided into the
somatic system and the autonomic system. The somatic system nerves control skeletal muscles,
skin, and joints. The autonomic system nerves control the glands and smooth muscles of the
internal organs and are not generally under conscious control and can be divided into two
systems: the sympathetic system which activates and prepares the body for vigorous muscular
activity, stress, and emergencies and the parasympathetic system which lowers activity, operates
during normal situations, permits digestion, and conserves energy.
Problem Set 1:
1. The function of the nervous system is to integrate and control the other body systems. Explain
how the nervous system does this.
the nervous system is divided into the central and peripheral nervous system. Within the
peripheral nervous system their is the autonomic system which communicated with smooth
muscle and internal organs and glands. Also in the peripheral system is somatic system which
communicates with sense organs and voluntary muscles.
2. List the 2 parts of the central nervous system.
Brain and spinal cord
3. How are the parts of the central nervous system protected?
brain and the vertebrae
4. How do the central nervous system and the peripheral nervous system interact?
through signals and impulses
5. What is included in the peripheral nervous system?
all the nerves not in the brain or spinal cord
6. What are the 2 divisions of the peripheral nervous system?
sensory (afferent) and motor (efferent)
7. Describe the movement of nerve impulses in the peripheral nervous system.
Within the peripheral nervous system their is the autonomic system which communicated with
smooth muscle and internal organs and glands. Also in the peripheral system is somatic system
which communicates with sense organs and voluntary muscles.
8. What are the 2 divisions of the efferent division of the peripheral nervous system?
autonomic and somatic systems
9. What is controlled by the somatic and autonomic nervous systems?
automatic communicates with smooth muscles, internal organs and glands.
somatic communicates with skeletal muscles, skin and joints
10. What are the 2 divisions of the autonomic nervous system?
sympathetic and parasympathetic
11. What is the function of the sympathetic nervous system?
to arouse and activate muscles for activity, stress and emergency
12. What is the function of the parasympathetic nervous system?
To calm and lower activity. Permits digestion and conserves energy
Neurons
Neurons (Figure below) are nerve cells that vary in size and shape. They do not undergo mitosis
(cell division), require enormous amounts of fuel, are able to survive just minutes without
oxygen, and can last an entire human lifetime. Neurons all have three parts: the dendrites, the
cell body, and the axon.
The neuron cell body, which synthesizes all nerve cell products, consists of a large nucleus with
surrounding cytoplasm containing the normal organelles. The dendrites are numerous short
extensions that emanate from the cell body which receive information from other neurons
conducting those nerve impulses toward the cell body. The single axon, on the other hand,
conducts nerve impulses away from the cell body to its axon terminals where it is emitted across
a synapse to the dendrite of another neuron. Axons can vary in length being very short or as long
as three feet, the length of the axon which extends from the bottom of the spine to the big toe.
Axons are composed of cells like the cell body but lack rough endoplasmic reticulum, depending
on the cell body for necessary proteins. The peripheral nerve axon is coated in short sections
called Schwann cells which are mainly composed of a white fatty layer called the myelin sheath
rolled around the axon which insulates the nerve fiber from others and increases the speed of
nerve impulses. There are also unmyelinated fibers, which are common in the gray matter of the
brain and spinal cord, in which the Schwann cells do not wrap around the axon but are just
loosely associated with the axon. The Schwann cell insulating sections are not continuous,
having gaps between them called Nodes of Ranvier. At these exposed nodes, the nerve impulse is
forced to jump to the next node in a manner called salutatory conduction, greatly increasing the
nerve impulse transmission along the axon. The cell body contains the nucleus and other
organelles typically found in cells with the exception of centrioles (since it is not capable of
mitosis). One of the main functions of the cell body is to manufacture neurotransmitters, which
are chemicals stored in secretory vesicles at the end of axon terminals. When neurotransmitters
are released by the axon terminal vesicles, they participate in the transmission of the nerve
impulse from one neuron to another.
Problem Set 2:
13. Identify the parts of the neuron shown in the diagram below.
a. Dendrite
b. Cell body
c. Nucleus
d. Axon
e. Myelin sheath
f. Schwann cell
g. Node of Ranvier
h. Axon terminal
14. List 3 unusual characteristics of neurons.
Do not undergo mitosis. Need oxygen to survive. Require a lot of energy and fuel to survive.
15. List the 3 parts of a neuron.
The cell body, dendrites, and axon
16. Describe the structure and function of the neuron cell body.
The cell body has a large nucleus with cytoplasm. It synthesizes all nerve cell products. The cell
body produces neurotransmitters and chemicals. When the neurotransmitters are released by the
axon terminals vesicles out of storage in secretory vesicles, they then help the process of nerve
impulses form one neuron to another.
17. Describe the structure and function of the dendrite.
The dendrite has numerous short extensions that receives information from other neurons
conducting them toward the cell body.
18. Describe the axon, including the number in each neuron, function, structure and organelles.
The axon can very in length, can be short or up to three feet tall. conducts nerve impulses away
from the cell body towards the axon terminal to be able to communicate from one neuron to
another. Axons are composed of cells like the cell body but lack rough endoplasmic reticulum.
19. Describe the composition and function of Schwann cells.
Schwann cells are composed of white fatty layer called myelin sheath which insulates nerve
fibers from other and increases nerve impulse speed.
20. Describe the location and function of the Nodes of Ranvier.
Nodes of Ranvier are located in the gaps between the non continuous shwann cells. These gaps
force impulses to jump to the next node which is called salutatory conduction which increases
the transmission of nerve impulses down the axon.
21. What important organelle is absent from the neuron cell body and what does the absence of
this organelle indicate about activity of the cell body?
Centrioles are absent in the cell body resulting in no mitosis in the cell body.
22. Describe the function and site of synthesis and storage of neurotransmitters.
The cell body produces neurotransmitters and chemicals. When the neurotransmitters are
released by the axon terminals vesicles out of storage in secretory vesicles, they then help the
process of nerve impulses form one neuron to another.
Neuroglial Cells
A nerve consists of hundreds of thousands of axons (#3) wrapped together in a connective tissue.
In the peripheral nervous s
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