Transcript Guided Notes for the Nervous System-

Guided Notes for the Nervous
System
Part One
Three Overlapping Functions of the
Nervous System
A. Uses millions of sensory receptors to
monitor stimuli inside and outside
the body (sensory input)
B. Processes and intercepts sensory
input and makes decisions
(integration)
C. Effects a response by activating
muscles or glands (motor output)
2. The nervous system works with the
endocrine system to regulate and
maintain homeostasis. While the
nervous system controls with rapid
electrical nerve impulses, the
endocrine system organs produce
hormones that are released into the
blood.
3. The central nervous system
consists of the brain and the spinal
cord, which act as the integrating and
command centers of the nervous
system. They interpret incoming
sensory information and issue
instructions based on past experience
and current conditions.
4. The peripheral nervous system
consists mainly of the nerves that
extend from the brain and spinal
cord. Spinal nerves carry impulses to
and from the spinal cord. Cranial
nerves carry impulses to and from the
brain.
5.There are two subdivisions of the PNS.
The sensory, or afferent, division
consists of nerve fibers that convey
impulses to the central nervous
system from sensory receptors
located in various parts of the body.
The motor, or efferent, division
carries impulses from the CNS to
effector organs, the muscles and
glands.
6. The motor division has two
subdivisions. The somatic nervous
system allows us to consciously, or
voluntarily, control our skeletal
muscles. The autonomic nervous
system regulates events that are
automatic, or involuntary, such as the
activity of smooth and cardiac
muscles and glands.
Major Differences Between
Neuroglia and Neurons
 Neuroglia are not able to transmit
nerve impulses
 Neuroglia never lose their ability to
divide
8. Schwann cells are supporting cells in
the PNS. They form the myelin
sheaths around nerve fibers that are
found in the PNS.
9. Neurons, also called nerve cells, are
highly specialized to transmit
messages (nerve impulses) from one
part of the body to another.
10. The cell body contains the
organelles and is the metabolic center
of the neuron. Neuron processes that
convey incoming messages toward
the cell body are called dendrites.
Processes that generate nerve
impulses away from the cell body are
axons. Neurons may have hundreds
of branching dendrites, but each
neuron has only one axon.
11. Most long nerve fibers are covered
with a whitish, fatty material called
myelin, which has a waxy
appearance.
12. Myelin protects and insulates nerve
fibers and increases the transmission
rate of nerve impulses.
13. Axons outside the CNS are
myelinated by Schwann cells.
A myelin sheath is a tight coil of
wrapped membranes of Schwann cells
which encloses the axon.
14. Instead of Schwann cells, neurons in
the CNS are myelinated by
oligodendrocytes, which form CNS
myelin sheaths.
15. In people with multiple sclerosis
(MS), the myelin sheaths around
nerve fibers are gradually destroyed
and converted to hardened sheaths
called scleroses.
16. Functional classification groups
neurons according to the direction the
nerve impulse is traveling relative to
the CNS. Sensory neurons are
neurons carrying impulses from
sensory receptors to the CNS. They
are also called afferent neurons.
Sensory neurons keep us informed
about what is happening both inside
and outside the body.
17. The dendrite endings of the sensory
neurons are usually associated with
specialized receptors that are
activated by specific changes
occurring nearby.
18. Neurons carrying impulses from the
CNS to the viscera, muscles, or
glands are called motor, or efferent
neurons.
19. Structural classification is based on
the number of processes extending
from the cell. If there are several, the
neuron is multipolar. This is the most
common type because all motor and
association neurons are multipolar.
20. Neurons with only two processes,
an axon and a dendrite are called
bipolar neurons. In adults, they are
found only in some special sense
organs (eye, ear).
21. Unipolar neurons have a single
process emerging from the cell body.
Sensory neurons found in PNS
ganglia are unipolar.
22. Neurons have two major functional
properties: irritability, which is the
ability to respond to a stimulus and
convert it into a nerve impulse, and
conductivity, the ability to transmit
the impulse to other neurons,
muscles and glands.
23. Reflexes are rapid, predictable, and
involuntary responses to stimuli.
Reflexes that occur over neural
pathways are called reflex arcs.
24. Autonomic reflexes regulate the
activity of smooth muscles, the heart,
and glands.
25. Somatic reflexes include all reflexes
that stimulate the skeletal muscles.