1.1 Neurons and glia are the primary cell types of all nervous systems
Learning goal: Has an idea of the huge diversity in cellular morphology of different
nerve cells.
Answer: Neurons show an extraordinary diversity in shape and size across the nervous
system. Despite sharing basic features like a cell body, dendrites, and an axon, individual
neurons can vary widely: some have no dendrites, while others have dendritic arbors as
complex as a mature tree.
This variability allows neurons to integrate information differently depending on their
structure, supporting the wide range of processing abilities in neural circuits. The
nervous system has a greater range of distinct cell types (morphology, molecular
identity, and function) than any other organ system.
Learning goal: Knows what the terms convergence and divergence mean in the context of a neuron
Answer:
• Divergence describes how many target cells a single neuron’s axon connects with. A minimally
divergent neuron connects to just one target, while a highly divergent neuron innervates multiple
targets, enabling wide signal distribution.
• Convergence refers to the degree to which a neuron's dendrites receive input from one or multiple
other neurons. High convergence means a neuron integrates inputs from many sources.
Learning goal: Know five types of glial cells and their function.
Answer:
• Astrocytes (CNS): Maintain the chemical environment for neurons, help form the blood–brain barrier, modulate synaptic activity, and serve
as neural stem cells in some regions.
• Oligodendrocytes (CNS): Form myelin sheaths around axons to
increase the speed of electrical signal conduction.
• Schwann cells (PNS): Myelinate axons in the peripheral nervous
system, like oligodendrocytes but outside the CNS.
• Microglial cells: Act as the brain’s immune cells, removing debris
and releasing cytokines to influence inflammation and cell survival.
• Glial precursor cells: Found among oligodendrocytes and
Schwann cells; these can generate new glia and sometimes new
neurons after injury or in cell culture.
Learning goal: Can determine when to use a Golgi staining and when a Nissl staining.
Answer:
• Golgi staining is used when detailed visualization of the full structure of individual neurons (including dendrites and
axons) is needed. It randomly stains a small number of cells, allowing detailed analysis of their morphology.
• Nissl staining is used when a general overview of the distribution, size, and density of neuron cell bodies across a tissue is
needed, but it does not show detailed processes like dendrites and axons.
1.2 Neurons are interconnected in ensembles called neural circuits
Learning goal: Describe the definitions of neural circuits and neuropil.
Answer: Neural circuits are organized groups of interconnected neurons that process specific types of information. They are defined by the
connections between identified groups of neurons and the capacity to process inputs into distinct outputs. Neuropil is the dense network of
interwoven axon terminals, dendrites, and glial cell processes (excluding cell bodies) where most synaptic connectivity occurs.
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,Learning goal: Know the terms afferent and efferent.
Answer: Both afferent and efferent neurons are types of projection neurons because their axons project over long distances.
• Afferent neurons carry information from the periphery toward the brain or spinal cord (or deeper centrally within them).
• Efferent neurons carry information away from the brain or spinal cord toward peripheral targets.
Learning goal: Can explain the knee-jerk response.
Answer: The knee-jerk reflex (myotatic reflex) is initiated when a muscle stretch
receptor is stimulated, generating receptor potentials that trigger action potentials.
These travel centrally along afferent sensory neurons whose cell bodies are in the
dorsal root ganglia.
The afferents synapse directly onto extensor motor neurons (causing muscle
contraction) and onto interneurons that inhibit flexor motor neurons (causing
muscle relaxation). This complementary activation ensures the leg extends properly in
response to a tap, helping maintain upright posture.
Learning goal: Knows the difference between intra- and extra-cellular
electrophysiological recordings.
Answer:
• Extracellular recording (A) places an electrode near a neuron to detect the pattern and
timing of action potentials without penetrating the cell.
• Intracellular recording (B) involves placing an electrode inside a neuron to measure
detailed membrane potentials, including the small graded potentials (receptor and synaptic
potentials) that precede action potentials.
Learning goal: Knows how calcium imaging and voltage sensitive dye imaging can record
intracellular responses.
Answer:
• Calcium imaging uses dyes or genetically encoded indicators to visualize transient changes
in intracellular calcium concentrations, which are associated with neuronal activity like action
potentials.
• Voltage-sensitive dye imaging uses dyes that embed in the neuronal membrane and
report changes in membrane potential, allowing visualization of electrical signals across
many neurons simultaneously.
Learning goal: Is familiar with optogenetics: channelrhodopsins.
Answer:
• Optogenetics uses light-sensitive proteins called opsins to control
neuron activity with light.
• Channelrhodopsins are a type of opsin that, when illuminated, allow
cations and anions to flow across the membrane, causing either
depolarization or hyperpolarization depending on the variant.
• Genes encoding channelrhodopsins can be introduced into neurons
via viral methods or in transgenic animals, allowing precise activation
or inhibition of neurons during experiments.
2|Page
, 1.3 Circuits that process related information constitute a neural system
Learning goal: Can give an example of a brain structure that is organized according to a topographic map.
Answer: A topographic map in neuroscience is an organized representation where neighboring points in sensory space (like points on the skin
or areas in the visual field) are mapped onto neighboring neurons in the brain, maintaining the spatial relationships from the sensory surface to
the brain structure. An example is the somatosensory cortex, where neurons are organized in a way that reflects a point-to-point
correspondence with specific parts of the body surface (as shown in topographic maps).
Learning goal: Knows the definition of a receptive field.
Answer: A receptive field is the region in sensory space (like an area of the body surface or a part of the retina) where a specific stimulus will
elicit a change in the action potential firing of a neuron.
Learning goal: Define the terms anterograde and retrograde.
Answer:
• Anterograde tracing refers to following neural connections from their source (cell body) to their termination (axon terminals). It tracks
how information travels outward from a neuron to where it sends its signals.
• Retrograde tracing refers to following connections from the terminus (axon terminals) back to the source (cell body). It tracks where the
input to a neuron is coming from.
Learning goal: Has knowledge of the brain area’s that belong
to the CNS and PNS.
Answer:
• CNS (Central Nervous System): Brain (including
cerebral hemispheres, diencephalon, cerebellum,
brainstem) and spinal cord.
• PNS (Peripheral Nervous System): Sensory neurons
linking sensory receptors to the CNS, motor neurons
connecting CNS to muscles (somatic motor division) or
organs (visceral/autonomic motor division), and
associated ganglia and nerves.
1.4 The genome controls brain organization and function
Learning goal: Has some idea of the number of human genes, how many are expressed in the nervous system and how many are specific for the
nervous system.
Answer: The human genome contains about 20,000 protein-coding genes. Approximately 17,000 of these genes (about 84%) are expressed in
the developing or mature nervous system. Of these, around 6,000 genes are expressed only in the nervous system.
3|Page
Learning goal: Has an idea of the huge diversity in cellular morphology of different
nerve cells.
Answer: Neurons show an extraordinary diversity in shape and size across the nervous
system. Despite sharing basic features like a cell body, dendrites, and an axon, individual
neurons can vary widely: some have no dendrites, while others have dendritic arbors as
complex as a mature tree.
This variability allows neurons to integrate information differently depending on their
structure, supporting the wide range of processing abilities in neural circuits. The
nervous system has a greater range of distinct cell types (morphology, molecular
identity, and function) than any other organ system.
Learning goal: Knows what the terms convergence and divergence mean in the context of a neuron
Answer:
• Divergence describes how many target cells a single neuron’s axon connects with. A minimally
divergent neuron connects to just one target, while a highly divergent neuron innervates multiple
targets, enabling wide signal distribution.
• Convergence refers to the degree to which a neuron's dendrites receive input from one or multiple
other neurons. High convergence means a neuron integrates inputs from many sources.
Learning goal: Know five types of glial cells and their function.
Answer:
• Astrocytes (CNS): Maintain the chemical environment for neurons, help form the blood–brain barrier, modulate synaptic activity, and serve
as neural stem cells in some regions.
• Oligodendrocytes (CNS): Form myelin sheaths around axons to
increase the speed of electrical signal conduction.
• Schwann cells (PNS): Myelinate axons in the peripheral nervous
system, like oligodendrocytes but outside the CNS.
• Microglial cells: Act as the brain’s immune cells, removing debris
and releasing cytokines to influence inflammation and cell survival.
• Glial precursor cells: Found among oligodendrocytes and
Schwann cells; these can generate new glia and sometimes new
neurons after injury or in cell culture.
Learning goal: Can determine when to use a Golgi staining and when a Nissl staining.
Answer:
• Golgi staining is used when detailed visualization of the full structure of individual neurons (including dendrites and
axons) is needed. It randomly stains a small number of cells, allowing detailed analysis of their morphology.
• Nissl staining is used when a general overview of the distribution, size, and density of neuron cell bodies across a tissue is
needed, but it does not show detailed processes like dendrites and axons.
1.2 Neurons are interconnected in ensembles called neural circuits
Learning goal: Describe the definitions of neural circuits and neuropil.
Answer: Neural circuits are organized groups of interconnected neurons that process specific types of information. They are defined by the
connections between identified groups of neurons and the capacity to process inputs into distinct outputs. Neuropil is the dense network of
interwoven axon terminals, dendrites, and glial cell processes (excluding cell bodies) where most synaptic connectivity occurs.
1|Page
,Learning goal: Know the terms afferent and efferent.
Answer: Both afferent and efferent neurons are types of projection neurons because their axons project over long distances.
• Afferent neurons carry information from the periphery toward the brain or spinal cord (or deeper centrally within them).
• Efferent neurons carry information away from the brain or spinal cord toward peripheral targets.
Learning goal: Can explain the knee-jerk response.
Answer: The knee-jerk reflex (myotatic reflex) is initiated when a muscle stretch
receptor is stimulated, generating receptor potentials that trigger action potentials.
These travel centrally along afferent sensory neurons whose cell bodies are in the
dorsal root ganglia.
The afferents synapse directly onto extensor motor neurons (causing muscle
contraction) and onto interneurons that inhibit flexor motor neurons (causing
muscle relaxation). This complementary activation ensures the leg extends properly in
response to a tap, helping maintain upright posture.
Learning goal: Knows the difference between intra- and extra-cellular
electrophysiological recordings.
Answer:
• Extracellular recording (A) places an electrode near a neuron to detect the pattern and
timing of action potentials without penetrating the cell.
• Intracellular recording (B) involves placing an electrode inside a neuron to measure
detailed membrane potentials, including the small graded potentials (receptor and synaptic
potentials) that precede action potentials.
Learning goal: Knows how calcium imaging and voltage sensitive dye imaging can record
intracellular responses.
Answer:
• Calcium imaging uses dyes or genetically encoded indicators to visualize transient changes
in intracellular calcium concentrations, which are associated with neuronal activity like action
potentials.
• Voltage-sensitive dye imaging uses dyes that embed in the neuronal membrane and
report changes in membrane potential, allowing visualization of electrical signals across
many neurons simultaneously.
Learning goal: Is familiar with optogenetics: channelrhodopsins.
Answer:
• Optogenetics uses light-sensitive proteins called opsins to control
neuron activity with light.
• Channelrhodopsins are a type of opsin that, when illuminated, allow
cations and anions to flow across the membrane, causing either
depolarization or hyperpolarization depending on the variant.
• Genes encoding channelrhodopsins can be introduced into neurons
via viral methods or in transgenic animals, allowing precise activation
or inhibition of neurons during experiments.
2|Page
, 1.3 Circuits that process related information constitute a neural system
Learning goal: Can give an example of a brain structure that is organized according to a topographic map.
Answer: A topographic map in neuroscience is an organized representation where neighboring points in sensory space (like points on the skin
or areas in the visual field) are mapped onto neighboring neurons in the brain, maintaining the spatial relationships from the sensory surface to
the brain structure. An example is the somatosensory cortex, where neurons are organized in a way that reflects a point-to-point
correspondence with specific parts of the body surface (as shown in topographic maps).
Learning goal: Knows the definition of a receptive field.
Answer: A receptive field is the region in sensory space (like an area of the body surface or a part of the retina) where a specific stimulus will
elicit a change in the action potential firing of a neuron.
Learning goal: Define the terms anterograde and retrograde.
Answer:
• Anterograde tracing refers to following neural connections from their source (cell body) to their termination (axon terminals). It tracks
how information travels outward from a neuron to where it sends its signals.
• Retrograde tracing refers to following connections from the terminus (axon terminals) back to the source (cell body). It tracks where the
input to a neuron is coming from.
Learning goal: Has knowledge of the brain area’s that belong
to the CNS and PNS.
Answer:
• CNS (Central Nervous System): Brain (including
cerebral hemispheres, diencephalon, cerebellum,
brainstem) and spinal cord.
• PNS (Peripheral Nervous System): Sensory neurons
linking sensory receptors to the CNS, motor neurons
connecting CNS to muscles (somatic motor division) or
organs (visceral/autonomic motor division), and
associated ganglia and nerves.
1.4 The genome controls brain organization and function
Learning goal: Has some idea of the number of human genes, how many are expressed in the nervous system and how many are specific for the
nervous system.
Answer: The human genome contains about 20,000 protein-coding genes. Approximately 17,000 of these genes (about 84%) are expressed in
the developing or mature nervous system. Of these, around 6,000 genes are expressed only in the nervous system.
3|Page
