Neurobiologie samenvatting
Neurobiology H1: Introduction
1.1: The origin of neuroscience & Views of the brain through history:
Ancient Egypt => described head injuries and mentioned the brain, even though Egyptians believed that the heart
was the seat of consciousness and emotion, not the brain.
Roman Empire => Pergamon who conducted dissections and advanced the idea that the brain controls behavior. He
showed the importance of the brain's ventricles.
Renaissance => more detailed brain studies were done.
• Vesalius describes the human brain and nervous system in his work ‘De humani corporis fabrica’.
• Descartes proposed model where mind and body are distinct, with pineal gland as interface between the 2.
17th and 18th centuries => In 1780 Galvani conducted experiments using frog legs and found that the muscles
contracted when an electric charge was applied to the nerves or muscles, the charge came from a Leyden jar. Galvani
was also able to cause muscle contraction without a charge, he concluded that there was another form of electricity
produced by living tissue. Scientists in this period also discovered that
• Brain = white matter inside & grey matter outside
• Spinal cord = white matter outside & grey matter inside
19th century => Scientists realized that
• Nerves are like wires and the nervous system can generate electricity.
• Dorsal (sensory fibers) and ventral (motor fibers) roots carry information in opposite directions.
• There is also a subdivision:
o A central nervous system = brain and spinal cord.
o A peripheral nervous system = network of nerves coursing through the body.
• Localisation of function in the brain
1.2: General Brain Anatomy
The brain is divided into 3 major divisions and these regions differ in function and embryological development
1) Forebrain => responsible for higher functions. It includes structures such as:
• Cerebrum => largest part of the brain and is divided into 2 hemispheres (left & right), each hemisphere is
divided into lobes (frontal, parietal, temporal & occipital).
• Hypothalamus => regulates homeostatic processes (T°, hunger, sleep-wake cycle, hormonal regulation, …).
• Limbic System => is involved in emotion, memory, and motivation.
2) Midbrain => contains the major motor supply to the muscles controlling eye movement and relays information for
some visual and auditory reflexes. It includes structures such as:
• Tectum and Tegmentum => involved in auditory and visual reflexes.
• Basal ganglia (with substantia nigra) => Degeneration of substantia nigra is associated with Parkinson's.
• Cerebral Peduncles => large axon bundles that carry motor commands from cerebral cortex to brainstem and
spinal cord.
3) Hindbrain => Controls basic life functions (breathing, heart rate, and balance). It includes structures such as:
• Cerebellum => located at the back of the brain and plays a role in coordination, balance, fine motor control
allowing smooth and precise movements.
• Pons => mass of nerve fibers forming a bridge between Medulla Oblongata and midbrain.
• Medulla Oblongata => lowest part of brainstem and controls heartbeat, breathing, and blood pressure.
,1.2.1: Brainstem
The brainstem is attached to the spinal cord at the bottom of the brain, and is composed of the midbrain, pons, and
medulla oblongata. It relays information between parts of the brain and regulates basic body functions.
1.2.2: Ventricular system & protective layers
Ventricles = series of interconnected cavities that are filled with cerebrospinal fluid (CSF). Ventricles fill the brain,
provide nutrients, and remove waste. The 4 main ventricles:
• 2 lateral ventricles (1 in each hemisphere)
• 3rd ventricle is in the midline of the brain
• 4th ventricle is located between the brainstem and cerebellum.
The brain is protected by several layers:
• Cranium (AKA skull) => protects the brain from external injury.
• Meninges => 3 protective membranes that cover the brain and the spinal cord:
o Dura Mater (outer layer) => thick and dense inelastic membrane, that
is composed of 2 layers closely connected that separate to form
sinuses for the passage of venous blood.
o Arachnoid Mater (middle layer) => delicate membrane that’s
separated from the pia mater by the subarachnoid cavity, which is
filled with CSF.
o Pia Mater (inner layer) => vascular membrane that directly covers the
brain's surface.
Cerebrospinal Fluid (CSF) provides additional protection and buoyancy to the brain and spinal cord.
1.3: Nervous System Disorders
• Alzheimer’s disease = progressive degenerative disease, characterized by dementia and is always fatal.
• Cerebral palsy = motor disorder caused by damage to the cerebrum at birth.
• Depression = disorder of mood, characterized by insomnia, loss of appetite, and feelings of dejection.
• Epilepsy = condition characterized by periodic disturbances of brain electrical activity which lead to seizures,
unconsciousness, and sensory disturbances.
• Multiple sclerosis = progressive disease that affects nerve condition, characterized by episodes of weakness,
lack of coordination, and speech disturbance.
• Parkinson’s disease = progressive disease that leads to difficulty in initiating voluntary movement.
• Schizophrenia = psychotic illness characterized by delusions, hallucinations, and bizarre behavior.
• Spinal paralysis = loss of feeling and movement caused by traumatic damage to the spinal cord.
• Stroke = loss of brain function caused by disruption of the blood supply, leading to permanent sensory,
motor, or cognitive deficits.
, Neurobiology H2: Neurons & Glia
2.1: Neurons
2.1.1: The neuron doctrine
The neuron doctrine = fundamental concept that states that the nervous system is made out of discrete individual
cells (AKA neurons), and these are the basic functional units of the brain and nervous system.
All neurons function independently, as they aren’t continuous with each other. They communicate with each other at
specialized junctions = synapses. There, there is a small gap (= synaptic cleft) between the transmitting and receiving
neurons, where neurotransmitters are released by one neuron and bind to the receptors on the other.
The information flows in 1 direction within a neuron: dendrites -> soma -> axon -> synapse = law of dynamic
polarization, proposed by Cajal.
2.1.2: Historical Background
Golgi supported the theory that the nervous system was a continuous network. When he developed a staining
technique (Golgi stain) that allow to visualize individual neurons under a microscope, Cajal used it to show that
neurons are separated from each other, forming layers. His work proved that neurons are not continuous, but
communicate through synapses.
The Golgi-Stain shows 2 parts of the neurons:
• Neuronal cell body (soma & perikaryon)
• Neurites (axons & dendrites)
=> Golgi stain allows the study of the entire neuron.
The Nissl Stain will stain all nuclei and neuron cell bodies => used to understand and study brain regions and the
cytoarchitecture in the central nervous system (CNS) but won't provide details about axons, dendrites, or synaptic
connections.
2.1.3: The Prototypical Neuron
Neuron = specialized nerve cell that serves as the functional unit of the nervous system => ca. 1011 neurons in the
brain and they have several functions:
• Process information
• Sense environmental changes
• Communicate these changes to other neurons
• Command body response
Anatomy of a neuron:
1) Neuronal Membrane => It’s a 5nm thick lipid bilayer that encloses the cytoplasm and separates it from the
external environment. It’s embedded with proteins for regulating in/out flow of ions and other substances. The
protein concentration in the membrane varies. The membrane is essential as it is a protective barrier and an active
participant in signal transmission and synaptic communication.
2) Cytoskeleton => A dynamic network of protein filaments and tubules forming an internal scaffolding for the
neuronal membrane. The cytoskeleton has 3 main types of protein filaments that are essential for proper
functioning:
• Microtubules => provide structural support.
• Microfilaments (= actin filaments) => help with intracellular transport, signaling, and cell movement.
• Neurofilaments (= intermediate filaments) => maintain the neuron’s shape and function over long periods.
, 3) Soma/Cell body => Is the central part of a neuron and it’s necessary for the neuron's survival, growth, and
function. It contains the following structures:
• Nucleus
• Nucleolus
• Cytoplasm
• Several organelles (Mitochondria, RER, SER & Golgi-apparatus)
• Lysosomes
4) Dendrites => Branched extensions of neurons specialized in receiving input from other neurons at synapses. At
synapses, dendrites interact with neurotransmitters and convert these chemical signals into electrical signals for
transmission to the soma of the receiving neuron. Many dendrites are studded with tiny protrusions (= dendritic
spines), these
• are the locations of many excitatory synapses
• allow neurons to form and strengthen connections in response to activity
5) Axons => Long, slender projection of a neuron that transmits action potentials from the soma to other neurons,
muscles, or glands. They allow signals to travel over long distances. Axons in humans have a diameter of 1 à 25µm (1
mm in a squid), and the length can be up to 1m. An axon has 3 parts:
• Axon hillock (beginning) = region where the axon connects to the soma and where the
action potential is initiated.
• Axon proper (middle) = axon part that extends from the soma to the axon terminals. It’s
responsible for transmitting the action potential along its length.
• Axon terminal (end) = small structures at the end of the axon, where it makes contact with
other neurons, muscle cells, or gland cells. The cytoplasm of the axon terminal is different
from the rest of the axon:
o No microtubules
o Presence of synaptic vesicles
o Lots of membrane proteins
o Large number of mitochondria
The ER of the soma doesn’t extend into the axon and the protein composition of the axon is unique.
Axoplasmic transport:
= materials (proteins, lipids, & organelles) are transported along the axons. The process relies on the cytoskeleton
(specifically microtubules), and molecular motors such as kinesin and dynein. It occurs in 2 directions:
• Anterograde transport = from soma to the axon terminal (uses kinesins)
• Retrograde transport = from the axon terminal back to the soma (uses dyneins)
VB: Mitochondrial trafficking and Ca²⁺ signaling:
• Mitochondrial trafficking = mitochondria move along the microtubules to areas where high ATP demand or
calcium buffering is needed (such as active synapses or nodes of Ranvier). Mitochondrial trafficking is
regulated by the energy demands of the cell and intracellular signaling molecules.
• Ca²⁺ signaling = is crucial for synaptic activity and plasticity in neurons. When neurons are activated, Ca²⁺ ions
enter the cytosol through voltage-gated calcium channels in the plasma membrane or are released from
intracellular stores like the ER.
=> Mitochondrial trafficking is influenced by local calcium levels. When calcium concentrations rise in specific
regions of the cell (at synapses), mitochondria often pause to buffer the calcium and supply ATP to power
calcium pumps. Mitochondria can take up Ca²⁺ through specialized channels, this helps prevent calcium overload
in the cytosol and maintains cellular homeostasis.
Neurobiology H1: Introduction
1.1: The origin of neuroscience & Views of the brain through history:
Ancient Egypt => described head injuries and mentioned the brain, even though Egyptians believed that the heart
was the seat of consciousness and emotion, not the brain.
Roman Empire => Pergamon who conducted dissections and advanced the idea that the brain controls behavior. He
showed the importance of the brain's ventricles.
Renaissance => more detailed brain studies were done.
• Vesalius describes the human brain and nervous system in his work ‘De humani corporis fabrica’.
• Descartes proposed model where mind and body are distinct, with pineal gland as interface between the 2.
17th and 18th centuries => In 1780 Galvani conducted experiments using frog legs and found that the muscles
contracted when an electric charge was applied to the nerves or muscles, the charge came from a Leyden jar. Galvani
was also able to cause muscle contraction without a charge, he concluded that there was another form of electricity
produced by living tissue. Scientists in this period also discovered that
• Brain = white matter inside & grey matter outside
• Spinal cord = white matter outside & grey matter inside
19th century => Scientists realized that
• Nerves are like wires and the nervous system can generate electricity.
• Dorsal (sensory fibers) and ventral (motor fibers) roots carry information in opposite directions.
• There is also a subdivision:
o A central nervous system = brain and spinal cord.
o A peripheral nervous system = network of nerves coursing through the body.
• Localisation of function in the brain
1.2: General Brain Anatomy
The brain is divided into 3 major divisions and these regions differ in function and embryological development
1) Forebrain => responsible for higher functions. It includes structures such as:
• Cerebrum => largest part of the brain and is divided into 2 hemispheres (left & right), each hemisphere is
divided into lobes (frontal, parietal, temporal & occipital).
• Hypothalamus => regulates homeostatic processes (T°, hunger, sleep-wake cycle, hormonal regulation, …).
• Limbic System => is involved in emotion, memory, and motivation.
2) Midbrain => contains the major motor supply to the muscles controlling eye movement and relays information for
some visual and auditory reflexes. It includes structures such as:
• Tectum and Tegmentum => involved in auditory and visual reflexes.
• Basal ganglia (with substantia nigra) => Degeneration of substantia nigra is associated with Parkinson's.
• Cerebral Peduncles => large axon bundles that carry motor commands from cerebral cortex to brainstem and
spinal cord.
3) Hindbrain => Controls basic life functions (breathing, heart rate, and balance). It includes structures such as:
• Cerebellum => located at the back of the brain and plays a role in coordination, balance, fine motor control
allowing smooth and precise movements.
• Pons => mass of nerve fibers forming a bridge between Medulla Oblongata and midbrain.
• Medulla Oblongata => lowest part of brainstem and controls heartbeat, breathing, and blood pressure.
,1.2.1: Brainstem
The brainstem is attached to the spinal cord at the bottom of the brain, and is composed of the midbrain, pons, and
medulla oblongata. It relays information between parts of the brain and regulates basic body functions.
1.2.2: Ventricular system & protective layers
Ventricles = series of interconnected cavities that are filled with cerebrospinal fluid (CSF). Ventricles fill the brain,
provide nutrients, and remove waste. The 4 main ventricles:
• 2 lateral ventricles (1 in each hemisphere)
• 3rd ventricle is in the midline of the brain
• 4th ventricle is located between the brainstem and cerebellum.
The brain is protected by several layers:
• Cranium (AKA skull) => protects the brain from external injury.
• Meninges => 3 protective membranes that cover the brain and the spinal cord:
o Dura Mater (outer layer) => thick and dense inelastic membrane, that
is composed of 2 layers closely connected that separate to form
sinuses for the passage of venous blood.
o Arachnoid Mater (middle layer) => delicate membrane that’s
separated from the pia mater by the subarachnoid cavity, which is
filled with CSF.
o Pia Mater (inner layer) => vascular membrane that directly covers the
brain's surface.
Cerebrospinal Fluid (CSF) provides additional protection and buoyancy to the brain and spinal cord.
1.3: Nervous System Disorders
• Alzheimer’s disease = progressive degenerative disease, characterized by dementia and is always fatal.
• Cerebral palsy = motor disorder caused by damage to the cerebrum at birth.
• Depression = disorder of mood, characterized by insomnia, loss of appetite, and feelings of dejection.
• Epilepsy = condition characterized by periodic disturbances of brain electrical activity which lead to seizures,
unconsciousness, and sensory disturbances.
• Multiple sclerosis = progressive disease that affects nerve condition, characterized by episodes of weakness,
lack of coordination, and speech disturbance.
• Parkinson’s disease = progressive disease that leads to difficulty in initiating voluntary movement.
• Schizophrenia = psychotic illness characterized by delusions, hallucinations, and bizarre behavior.
• Spinal paralysis = loss of feeling and movement caused by traumatic damage to the spinal cord.
• Stroke = loss of brain function caused by disruption of the blood supply, leading to permanent sensory,
motor, or cognitive deficits.
, Neurobiology H2: Neurons & Glia
2.1: Neurons
2.1.1: The neuron doctrine
The neuron doctrine = fundamental concept that states that the nervous system is made out of discrete individual
cells (AKA neurons), and these are the basic functional units of the brain and nervous system.
All neurons function independently, as they aren’t continuous with each other. They communicate with each other at
specialized junctions = synapses. There, there is a small gap (= synaptic cleft) between the transmitting and receiving
neurons, where neurotransmitters are released by one neuron and bind to the receptors on the other.
The information flows in 1 direction within a neuron: dendrites -> soma -> axon -> synapse = law of dynamic
polarization, proposed by Cajal.
2.1.2: Historical Background
Golgi supported the theory that the nervous system was a continuous network. When he developed a staining
technique (Golgi stain) that allow to visualize individual neurons under a microscope, Cajal used it to show that
neurons are separated from each other, forming layers. His work proved that neurons are not continuous, but
communicate through synapses.
The Golgi-Stain shows 2 parts of the neurons:
• Neuronal cell body (soma & perikaryon)
• Neurites (axons & dendrites)
=> Golgi stain allows the study of the entire neuron.
The Nissl Stain will stain all nuclei and neuron cell bodies => used to understand and study brain regions and the
cytoarchitecture in the central nervous system (CNS) but won't provide details about axons, dendrites, or synaptic
connections.
2.1.3: The Prototypical Neuron
Neuron = specialized nerve cell that serves as the functional unit of the nervous system => ca. 1011 neurons in the
brain and they have several functions:
• Process information
• Sense environmental changes
• Communicate these changes to other neurons
• Command body response
Anatomy of a neuron:
1) Neuronal Membrane => It’s a 5nm thick lipid bilayer that encloses the cytoplasm and separates it from the
external environment. It’s embedded with proteins for regulating in/out flow of ions and other substances. The
protein concentration in the membrane varies. The membrane is essential as it is a protective barrier and an active
participant in signal transmission and synaptic communication.
2) Cytoskeleton => A dynamic network of protein filaments and tubules forming an internal scaffolding for the
neuronal membrane. The cytoskeleton has 3 main types of protein filaments that are essential for proper
functioning:
• Microtubules => provide structural support.
• Microfilaments (= actin filaments) => help with intracellular transport, signaling, and cell movement.
• Neurofilaments (= intermediate filaments) => maintain the neuron’s shape and function over long periods.
, 3) Soma/Cell body => Is the central part of a neuron and it’s necessary for the neuron's survival, growth, and
function. It contains the following structures:
• Nucleus
• Nucleolus
• Cytoplasm
• Several organelles (Mitochondria, RER, SER & Golgi-apparatus)
• Lysosomes
4) Dendrites => Branched extensions of neurons specialized in receiving input from other neurons at synapses. At
synapses, dendrites interact with neurotransmitters and convert these chemical signals into electrical signals for
transmission to the soma of the receiving neuron. Many dendrites are studded with tiny protrusions (= dendritic
spines), these
• are the locations of many excitatory synapses
• allow neurons to form and strengthen connections in response to activity
5) Axons => Long, slender projection of a neuron that transmits action potentials from the soma to other neurons,
muscles, or glands. They allow signals to travel over long distances. Axons in humans have a diameter of 1 à 25µm (1
mm in a squid), and the length can be up to 1m. An axon has 3 parts:
• Axon hillock (beginning) = region where the axon connects to the soma and where the
action potential is initiated.
• Axon proper (middle) = axon part that extends from the soma to the axon terminals. It’s
responsible for transmitting the action potential along its length.
• Axon terminal (end) = small structures at the end of the axon, where it makes contact with
other neurons, muscle cells, or gland cells. The cytoplasm of the axon terminal is different
from the rest of the axon:
o No microtubules
o Presence of synaptic vesicles
o Lots of membrane proteins
o Large number of mitochondria
The ER of the soma doesn’t extend into the axon and the protein composition of the axon is unique.
Axoplasmic transport:
= materials (proteins, lipids, & organelles) are transported along the axons. The process relies on the cytoskeleton
(specifically microtubules), and molecular motors such as kinesin and dynein. It occurs in 2 directions:
• Anterograde transport = from soma to the axon terminal (uses kinesins)
• Retrograde transport = from the axon terminal back to the soma (uses dyneins)
VB: Mitochondrial trafficking and Ca²⁺ signaling:
• Mitochondrial trafficking = mitochondria move along the microtubules to areas where high ATP demand or
calcium buffering is needed (such as active synapses or nodes of Ranvier). Mitochondrial trafficking is
regulated by the energy demands of the cell and intracellular signaling molecules.
• Ca²⁺ signaling = is crucial for synaptic activity and plasticity in neurons. When neurons are activated, Ca²⁺ ions
enter the cytosol through voltage-gated calcium channels in the plasma membrane or are released from
intracellular stores like the ER.
=> Mitochondrial trafficking is influenced by local calcium levels. When calcium concentrations rise in specific
regions of the cell (at synapses), mitochondria often pause to buffer the calcium and supply ATP to power
calcium pumps. Mitochondria can take up Ca²⁺ through specialized channels, this helps prevent calcium overload
in the cytosol and maintains cellular homeostasis.
