PSY 402 – Cognitive Neuroscience
Midterm Study Guide
Define myelin, the process of myelination, and the purpose of myelination. What happens when certain
diseases cause demyelination?
Myelin and Myelination
Myelin is a fatty, insulating layer that surrounds the axons of neurons in both the central nervous
system (CNS) and peripheral nervous system (PNS). It is produced by oligodendrocytes in the CNS
and Schwann cells in the PNS. Myelin is crucial for the efficient transmission of electrical signals
(action potentials) along nerve fibers.
Myelination is the biological process through which myelin sheaths are formed around the axons. This
process begins prenatally and continues into early adulthood, with significant development occurring
in infancy and childhood. Myelination progresses in a specific order, starting with regions responsible
for basic motor and sensory functions and later moving to areas involved in more complex cognitive
tasks, like the frontal lobe.
Purpose of Myelination
1. Increases the Speed of Nerve Impulses:
Myelin allows for faster transmission of electrical signals by enabling saltatory conduction, where the
action potential jumps from one node of Ranvier (gaps in the myelin sheath) to the next.
2. Enhances Signal Efficiency:
It prevents electrical signals from dissipating, ensuring that the message reaches its destination
accurately and quickly.
3. Protects Nerve Fibers:
Myelin provides a protective coating that shields nerve fibers from damage.
4. Supports Cognitive and Motor Function Development:
The maturation of myelination is linked to developmental milestones in both cognitive and motor
abilities, such as language acquisition and coordination.
What Happens in Demyelination?
Demyelination refers to the loss or damage of the myelin sheath surrounding nerves. This disrupts the normal
flow of electrical signals, leading to slower or blocked nerve impulses, which can cause a wide range of
neurological symptoms.
Effects of Demyelination:
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, Slowed or Blocked Nerve Transmission: Results in muscle weakness, coordination problems, and
sensory disturbances.
Neurological Deficits: May include vision problems, numbness, tingling, fatigue, and cognitive
impairments.
Permanent Nerve Damage: In severe cases, the underlying axon may also become damaged, leading to
permanent disability.
Diseases Associated with Demyelination:
1. Multiple Sclerosis (MS):
o An autoimmune disorder where the immune system attacks the myelin in the central nervous
system.
o Symptoms include muscle weakness, vision problems, fatigue, and balance issues.
2. Guillain-Barré Syndrome (GBS):
o An autoimmune disorder affecting the peripheral nervous system.
o Causes rapid-onset muscle weakness and can lead to paralysis if untreated.
3. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP):
o A chronic form of Guillain-Barré, affecting the peripheral nerves over a longer period.
o Results in progressive weakness and numbness in the limbs.
4. Leukodystrophies:
o A group of genetic disorders that affect the growth or maintenance of myelin.
o Symptoms can appear in childhood and often include developmental delays and motor
dysfunction.
5. Progressive Multifocal Leukoencephalopathy (PML):
o A rare viral disease caused by the JC virus, typically affecting immunocompromised
individuals.
o Leads to severe neurological impairment and is often fatal.
Conclusion
Myelin is essential for rapid and efficient communication between neurons, playing a critical role in both
motor and cognitive functions. When diseases cause demyelination, the disruption of nerve signal
transmission can lead to debilitating neurological symptoms and, in severe cases, permanent disability.
Early detection and treatment of demyelinating diseases are vital to slowing disease progression and preserving
nerve function.
Describe the structure and function of the following cells: Schwann cells, glia, microglia, and neurons.
1. Schwann Cells
Structure:
Schwann cells are glial cells located in the peripheral nervous system (PNS). They have a spiral-
© 2024. Grand Canyon University. All Rights Reserved.
, shaped structure that wraps around the axons of peripheral neurons, forming the myelin sheath. Each
Schwann cell myelinates a single segment of one axon. They contain a nucleus and cytoplasm, which
are pushed to the outermost layer during the myelination process, forming the neurilemma.
Function:
o Myelination: Schwann cells insulate axons with myelin, increasing the speed and efficiency of
nerve impulse transmission through saltatory conduction.
o Nerve Regeneration: Unlike glial cells in the CNS, Schwann cells support axon regeneration
after injury by creating a pathway for regrowth.
o Support and Protection: They provide structural and metabolic support to neurons in the
PNS.
2. Glial Cells (Neuroglia)
Structure:
Glial cells are non-neuronal cells in the central nervous system (CNS) and peripheral nervous
system (PNS). They come in various forms, each with specialized structures:
o Astrocytes: Star-shaped cells with numerous projections.
o Oligodendrocytes: Similar to Schwann cells but located in the CNS, myelinating multiple
axons.
o Ependymal Cells: Ciliated cells lining the ventricles of the brain and central canal of the spinal
cord.
Function:
o Support Neurons: Glial cells provide structural and nutritional support to neurons.
o Myelination: Oligodendrocytes myelinate axons in the CNS.
o Blood-Brain Barrier: Astrocytes help maintain the blood-brain barrier, regulating the
passage of substances from the blood to the brain.
o Regulate Homeostasis: Glial cells help maintain the ionic balance and remove waste products.
o Repair and Scarring: They assist in repairing the nervous system after injury and form glial
scars in response to damage.
3. Microglia
Structure:
Microglia are small, spider-like cells with long, branching processes. They are the resident immune
cells of the central nervous system (CNS) and belong to the mononuclear phagocyte system. In their
resting state, they have a ramified (branched) structure, but they become amoeboid when activated
during injury or infection.
Function:
o Immune Defense: Microglia act as the first line of defense in the CNS, identifying and
responding to injury, infection, and disease.
o Phagocytosis: They engulf and remove pathogens, cellular debris, and dead neurons.
o Inflammatory Response: Microglia release cytokines and chemokines to mediate the
inflammatory response.
o Synaptic Pruning: They help refine neural circuits during development by eliminating
unnecessary synaptic connections.
4. Neurons
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, Structure:
Neurons are the primary functional units of the nervous system, specialized for transmitting
electrical signals. They have three main parts:
o Cell Body (Soma): Contains the nucleus and organelles necessary for cellular function.
o Dendrites: Branched projections that receive signals from other neurons and convey them
toward the cell body.
o Axon: A long, slender projection that transmits electrical impulses away from the cell body
toward other neurons, muscles, or glands. The axon may be covered with a myelin sheath to
speed up signal conduction.
o Axon Terminals: The endings of axons where neurotransmitters are released to communicate
with other neurons across synapses.
Function:
o Signal Transmission: Neurons transmit electrical impulses (action potentials) and chemical
signals to communicate with other cells.
o Processing Information: They integrate incoming signals from dendrites and determine
whether to generate an action potential.
o Synaptic Communication: Neurons release neurotransmitters at the synapse to activate or
inhibit other neurons, muscles, or glands.
o Specialization: Depending on their function, neurons can be classified as sensory neurons
(carrying signals from sensory receptors), motor neurons (sending signals to muscles), or
interneurons (connecting neurons within the CNS).
Summary Chart
Cell Type Structure Function
Schwann Spiral-shaped, wrap around PNS axons, Myelinate peripheral nerves, support nerve
Cells form myelin sheath regeneration
Various forms (astrocytes, oligodendrocytes, Support neurons, myelinate CNS axons, maintain
Glial Cells
ependymal cells) blood-brain barrier, repair
Small, branched (ramified), become Immune defense, phagocytosis, inflammatory
Microglia
amoeboid when activated response, synaptic pruning
Transmit electrical signals, process information,
Neurons Soma, dendrites, axon, axon terminals
synaptic communication
These cells work together to maintain the health and functionality of the nervous system, supporting everything
from basic reflexes to complex cognitive processes.
Describe the structure of a neuron and the functions of its component parts.
Structure of a Neuron and the Functions of Its Components
A neuron is the basic structural and functional unit of the nervous system, specialized in transmitting
electrical and chemical signals throughout the body. While neurons can vary in shape and size depending on
their function, they all share the same fundamental components:
© 2024. Grand Canyon University. All Rights Reserved.
Midterm Study Guide
Define myelin, the process of myelination, and the purpose of myelination. What happens when certain
diseases cause demyelination?
Myelin and Myelination
Myelin is a fatty, insulating layer that surrounds the axons of neurons in both the central nervous
system (CNS) and peripheral nervous system (PNS). It is produced by oligodendrocytes in the CNS
and Schwann cells in the PNS. Myelin is crucial for the efficient transmission of electrical signals
(action potentials) along nerve fibers.
Myelination is the biological process through which myelin sheaths are formed around the axons. This
process begins prenatally and continues into early adulthood, with significant development occurring
in infancy and childhood. Myelination progresses in a specific order, starting with regions responsible
for basic motor and sensory functions and later moving to areas involved in more complex cognitive
tasks, like the frontal lobe.
Purpose of Myelination
1. Increases the Speed of Nerve Impulses:
Myelin allows for faster transmission of electrical signals by enabling saltatory conduction, where the
action potential jumps from one node of Ranvier (gaps in the myelin sheath) to the next.
2. Enhances Signal Efficiency:
It prevents electrical signals from dissipating, ensuring that the message reaches its destination
accurately and quickly.
3. Protects Nerve Fibers:
Myelin provides a protective coating that shields nerve fibers from damage.
4. Supports Cognitive and Motor Function Development:
The maturation of myelination is linked to developmental milestones in both cognitive and motor
abilities, such as language acquisition and coordination.
What Happens in Demyelination?
Demyelination refers to the loss or damage of the myelin sheath surrounding nerves. This disrupts the normal
flow of electrical signals, leading to slower or blocked nerve impulses, which can cause a wide range of
neurological symptoms.
Effects of Demyelination:
© 2024. Grand Canyon University. All Rights Reserved.
, Slowed or Blocked Nerve Transmission: Results in muscle weakness, coordination problems, and
sensory disturbances.
Neurological Deficits: May include vision problems, numbness, tingling, fatigue, and cognitive
impairments.
Permanent Nerve Damage: In severe cases, the underlying axon may also become damaged, leading to
permanent disability.
Diseases Associated with Demyelination:
1. Multiple Sclerosis (MS):
o An autoimmune disorder where the immune system attacks the myelin in the central nervous
system.
o Symptoms include muscle weakness, vision problems, fatigue, and balance issues.
2. Guillain-Barré Syndrome (GBS):
o An autoimmune disorder affecting the peripheral nervous system.
o Causes rapid-onset muscle weakness and can lead to paralysis if untreated.
3. Chronic Inflammatory Demyelinating Polyneuropathy (CIDP):
o A chronic form of Guillain-Barré, affecting the peripheral nerves over a longer period.
o Results in progressive weakness and numbness in the limbs.
4. Leukodystrophies:
o A group of genetic disorders that affect the growth or maintenance of myelin.
o Symptoms can appear in childhood and often include developmental delays and motor
dysfunction.
5. Progressive Multifocal Leukoencephalopathy (PML):
o A rare viral disease caused by the JC virus, typically affecting immunocompromised
individuals.
o Leads to severe neurological impairment and is often fatal.
Conclusion
Myelin is essential for rapid and efficient communication between neurons, playing a critical role in both
motor and cognitive functions. When diseases cause demyelination, the disruption of nerve signal
transmission can lead to debilitating neurological symptoms and, in severe cases, permanent disability.
Early detection and treatment of demyelinating diseases are vital to slowing disease progression and preserving
nerve function.
Describe the structure and function of the following cells: Schwann cells, glia, microglia, and neurons.
1. Schwann Cells
Structure:
Schwann cells are glial cells located in the peripheral nervous system (PNS). They have a spiral-
© 2024. Grand Canyon University. All Rights Reserved.
, shaped structure that wraps around the axons of peripheral neurons, forming the myelin sheath. Each
Schwann cell myelinates a single segment of one axon. They contain a nucleus and cytoplasm, which
are pushed to the outermost layer during the myelination process, forming the neurilemma.
Function:
o Myelination: Schwann cells insulate axons with myelin, increasing the speed and efficiency of
nerve impulse transmission through saltatory conduction.
o Nerve Regeneration: Unlike glial cells in the CNS, Schwann cells support axon regeneration
after injury by creating a pathway for regrowth.
o Support and Protection: They provide structural and metabolic support to neurons in the
PNS.
2. Glial Cells (Neuroglia)
Structure:
Glial cells are non-neuronal cells in the central nervous system (CNS) and peripheral nervous
system (PNS). They come in various forms, each with specialized structures:
o Astrocytes: Star-shaped cells with numerous projections.
o Oligodendrocytes: Similar to Schwann cells but located in the CNS, myelinating multiple
axons.
o Ependymal Cells: Ciliated cells lining the ventricles of the brain and central canal of the spinal
cord.
Function:
o Support Neurons: Glial cells provide structural and nutritional support to neurons.
o Myelination: Oligodendrocytes myelinate axons in the CNS.
o Blood-Brain Barrier: Astrocytes help maintain the blood-brain barrier, regulating the
passage of substances from the blood to the brain.
o Regulate Homeostasis: Glial cells help maintain the ionic balance and remove waste products.
o Repair and Scarring: They assist in repairing the nervous system after injury and form glial
scars in response to damage.
3. Microglia
Structure:
Microglia are small, spider-like cells with long, branching processes. They are the resident immune
cells of the central nervous system (CNS) and belong to the mononuclear phagocyte system. In their
resting state, they have a ramified (branched) structure, but they become amoeboid when activated
during injury or infection.
Function:
o Immune Defense: Microglia act as the first line of defense in the CNS, identifying and
responding to injury, infection, and disease.
o Phagocytosis: They engulf and remove pathogens, cellular debris, and dead neurons.
o Inflammatory Response: Microglia release cytokines and chemokines to mediate the
inflammatory response.
o Synaptic Pruning: They help refine neural circuits during development by eliminating
unnecessary synaptic connections.
4. Neurons
© 2024. Grand Canyon University. All Rights Reserved.
, Structure:
Neurons are the primary functional units of the nervous system, specialized for transmitting
electrical signals. They have three main parts:
o Cell Body (Soma): Contains the nucleus and organelles necessary for cellular function.
o Dendrites: Branched projections that receive signals from other neurons and convey them
toward the cell body.
o Axon: A long, slender projection that transmits electrical impulses away from the cell body
toward other neurons, muscles, or glands. The axon may be covered with a myelin sheath to
speed up signal conduction.
o Axon Terminals: The endings of axons where neurotransmitters are released to communicate
with other neurons across synapses.
Function:
o Signal Transmission: Neurons transmit electrical impulses (action potentials) and chemical
signals to communicate with other cells.
o Processing Information: They integrate incoming signals from dendrites and determine
whether to generate an action potential.
o Synaptic Communication: Neurons release neurotransmitters at the synapse to activate or
inhibit other neurons, muscles, or glands.
o Specialization: Depending on their function, neurons can be classified as sensory neurons
(carrying signals from sensory receptors), motor neurons (sending signals to muscles), or
interneurons (connecting neurons within the CNS).
Summary Chart
Cell Type Structure Function
Schwann Spiral-shaped, wrap around PNS axons, Myelinate peripheral nerves, support nerve
Cells form myelin sheath regeneration
Various forms (astrocytes, oligodendrocytes, Support neurons, myelinate CNS axons, maintain
Glial Cells
ependymal cells) blood-brain barrier, repair
Small, branched (ramified), become Immune defense, phagocytosis, inflammatory
Microglia
amoeboid when activated response, synaptic pruning
Transmit electrical signals, process information,
Neurons Soma, dendrites, axon, axon terminals
synaptic communication
These cells work together to maintain the health and functionality of the nervous system, supporting everything
from basic reflexes to complex cognitive processes.
Describe the structure of a neuron and the functions of its component parts.
Structure of a Neuron and the Functions of Its Components
A neuron is the basic structural and functional unit of the nervous system, specialized in transmitting
electrical and chemical signals throughout the body. While neurons can vary in shape and size depending on
their function, they all share the same fundamental components:
© 2024. Grand Canyon University. All Rights Reserved.
