Download Notes: Nervous System PPT 1

UNIT B Chapter 12: Nervous System
Chapter 12: Nervous System
In this chapter, you will learn about the
structure and function of the nervous
system.
How might a researcher study the
effects of frequent head trauma?
Sport-Related Head Trauma and Brain
Function. Neurosurgeon Dr. Robert Cantu has
studied the brains of many deceased athletes,
including hockey and football players. He has
found that these players often suffered from
chronic traumatic encephalopathy (CTE), a
degenerative brain disease caused by repeated
blunt impact to the head.
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How might one determine which part
of the brain has been affected by
repeated blunt impacts?
Given the available information about
CTE, what steps do you feel should be
taken to prevent its occurrence (if any)?
UNIT B Chapter 12: Nervous System
Nervous Tissue
The nervous system coordinates and regulates the
functioning of the body’s other systems.
The nervous system consists of two major systems:
Central nervous system (CNS): brain and spinal cord
Peripheral nervous system (PNS):
• nerves that carry sensory messages CNS
• Nerves that carry motor commands from the CNS to
the muscles and glands
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Section 12.1
UNIT B Chapter 12: Nervous System
Section 12.1
The nervous system contains two types of cells:
Neurons (Nerve Cells):
• transmit nerve impulses between parts of the nervous system
Neuroglia (Glial Cells):
1. support and nourish neurons,
2. maintain homeostasis,
3. form myelin that surrounds neurons,
4. aid in signal transmission,
5. destroy and remove the carcasses of dead neurons (clean up).
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Neuronal Structure
UNIT B Chapter 12: Nervous System
Section 12.1
Most Neurons have three parts:
• Cell body: contains the nucleus
and other organelles
• Dendrites: extensions leading
toward the cell body that
receive signals from other
neurons and send them to the
cell body
• Axon: conducts nerve
impulses away from the cell
body toward other neurons or
effectors
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Figure 12.2 Types
of neurons.
UNIT B Chapter 12: Nervous System
Section 12.1
3 Types of Neurons:
• Sensory neurons: detect
changes in the environment,
take messages to the CNS;
• Interneurons: receive input
from sensory neurons and other
interneurons in the CNS
• Motor neurons: take messages
away from the CNS to an
effector (an organ, muscle fibre,
or gland);
o Effectors carry out responses
to environmental changes
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Figure 12.2 Types
of neurons.
Flow of Information from Receptors to
Effectors of Nervous System
Reflex Arc: nerve pathway followed by a
reflex action
UNIT B Chapter 12: Nervous System
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Section 12.1
The nervous system contains two types of cells:
Neurons:
• transmit nerve impulses between parts of the nervous system
Neuroglia (Glial Cells):
1. support and nourish neurons,
2. maintain homeostasis,
3. form myelin that surrounds neurons,
4. aid in signal transmission,
5. destroy and remove the carcasses of dead neurons (clean up).
Neuroglia is found in both CNS and PNS
Glial Cells in CNS
Glial Cells in PNS
Oligodendrocytes
Astrocytes
Microglia
Ependymal Cells
Satellite Cells
Schwann cells
Neuroglia Glial Cells of CNS
Glia of CNS
Oligodendrocytes - support and insulate axons
Astrocytes -regulate transmission of electrical impulses in brain.
Microglia -mediate immune responses in CNS by acting as
macrophages, clearing cellular debris and dead neurons from
nervous tissue through the process of phagocytosis
Ependymal Cells - line the CSF-filled ventricles in the brain and
the central canal of the spinal cord
Glial Cells of PNS
Glial Cells of PNS
Satellite Cells – cover the surface of nerve cell bodies
Schwann cells – produce myelin in PNS
UNIT B Chapter 12: Nervous System
Section 12.1
Myelin Sheath
Some axons are covered by a
protective myelin sheath.
Myelin:
• proteins and phospholipids
forming a whitish insulating
sheath around many nerve
fibers,
• increase the speed at which
impulses are conducted.
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Figure 12.3 Myelin sheath. a. In the
PNS, a myelin sheath forms when
Schwann cells wrap themselves around
an axon. b. Electron micrograph of a
cross section of an axon surrounded by
a myelin sheath.
Myelin Sheath
UNIT B Chapter 12: Nervous System
Section 12.1
Myelin in the PNS
• produced by Schwann cells by wrapping around
axon and laying down many layers of plasma membrane
• Each Schwann cell myelinates only part of an
axon, leaving gaps called nodes of Ranvier
• The myelin sheath plays an important role in
nerve generation in the PNS
• If an axon is severed, the myelin sheath remains
and serves as a passageway for new fibre growth
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Myelin in the CNS:
• produced by oligodendrocytes
• Nerve regeneration does not occur to any significant degree in
the CNS
UNIT B Chapter 12: Nervous System
Section 12.1
2 Types of Nervous tissue in the CNS:
• Grey matter
o Contains neurons with short, non-myelinated axons
o Found in the surface layer of the brain and the central part
of the spinal cord
• White matter
o Contains myelinated axons that run together in bundles
called tracts
o Found deep within the grey matter of the brain and
surrounds the grey matter in the spinal cord
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Brain
UNIT B Chapter 12: Nervous System
Check Your Progress
1. Identify the three classes of neurons, and describe their
relationship to each other.
2. Describe the three parts of a neuron.
3. Distinguish the cell types that form the myelin in the PNS
versus the CNS.
4. Review the structure of grey matter and white matter, and
describe where each is found in the CNS and the PNS.
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Section 12.1
UNIT B Chapter 12: Nervous System
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Section 12.1
UNIT B Chapter 12: Nervous System
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Section 12.1