week one

LO 3.1 List and describe the major divisions of the nervous system.

There are two central divisions: the central nervous system, located in the spine and skull, and the peripheral nervous system, which is outside of it. The CNS is composed of two divisions: the brain and the spinal cord. The brain controls functions, and the spinal cord sends signals.

The peripheral nervous system is also composed of two divisions. The somatic nervous system allows for interaction with the world and is composed of nerves that bring in sensory information and nerves that send out motor signals. The autonomic nervous system controls involuntary functions like heart rate and breathing.

Within the ANS, there are two more divisions: the sympathetic and parasympathetic nervous systems. The sympathetic nervous system controls fight-or-flight responses, such as a stress response when faced with unsafe circumstances. If one saw a bear, heart rate would increase, and pupils would dilate due to this nervous system response, helping with fight or flight. The parasympathetic nervous system is the rest-and-digest mode for when you are not in danger, allowing for a calming down of the body's functions, which slows heart rate and allows the body to function normally.

The cranial nerves are also part of the PNS, as they extend out of the brain rather than the spinal cord. Humans have 12 pairs of cranial nerves. Some are purely for sensory information gathering, such as the olfactory nerve, which allows for scent detection. Others serve both sensory and motor functions. The vagus nerve is the longest cranial nerve. It extends into the gut and aids in digestion, as well as regulating other autonomic functions.

LO 3.2 Describe the three meninges and explain their functional role.

The outer membraine is tough, called the dura mater folloed by the fine arachnoid membraine due to its spiderlike thinness and then the subarachnoid membrauin which contains mny large blood vessels. This is then folloed by the delicaqte pia mater  which adheres to the surface of the cns.

The brain and spinal cord are the most protected organs in the body as they are encased in bone and three protective membranes. These are called the three meninges

LO 3.3 Explain where cerebrospinal fluid is produced and where it flows.

The CNS is also protected by cerebrospinal fluid (CSF), which fills the subarachnoid space, the central canal of the spinal cord, and the cerebral ventricles in the brain. This ventricle refers to the four large internal chambers of the brain, consisting of the two lateral ventricles, third, and fourth.

All three fluid-filled spaces are interconnected by a series of openings and thus form a single reservoir. The fluid cushions the brain. Those without experience may get headaches and stabbing pain after jerking their heads.

The fluid is produced by the choroid plexuses (a network of capillaries that protrude into the ventricles from the pia mater). The excess fluid is absorbed from the subarachnoid space into large blood-filled spaces called dural sinuses, which run through the dura mater and drain into the jugular artery. However, there is an assumption that it is more complex.

Occasionally, the fluid's flow is blocked by a tumor near channels that link the ventricles. The buildup from this expands the walls of the ventricles and, thus, the brain. This is called hydrocephalus and is treated by draining the fluid.

LO 3.4 Explain what the blood–brain barrier is and what functional role it serves.

Cells of the Nervous System

The blood-brain barrier (BBB) is a protective mechanism that prevents harmful substances from entering the brain. It is formed by tightly packed cells in the walls of cerebral blood vessels, unlike the looser arrangement in other parts of the body, which allows easier passage of molecules. The BBB selectively allows certain essential substances, like glucose, to pass through, often through active transport. However, large molecules, particularly proteins, are generally blocked. Impairments in the BBB are linked to various central nervous system disorders, and the ability of drugs to affect brain activity depends on how easily they can cross this barrier.

LO 3.5 Draw, label, and define the major features of a multipolar neuron

The neuron cell membrane consists of a lipid bilayer with embedded protein molecules, including channel proteins that allow molecules to pass through and signal proteins that transmit signals into the neuron. Neurons are classified based on the number of processes extending from their cell body: multipolar neurons have multiple processes, unipolar neurons have one, and bipolar neurons have two. Interneurons have short or no axons and integrate neural activity within a single brain structure. The nervous system has two main types of structures: clusters of cell bodies, known as nuclei in the CNS and ganglia in the PNS, and bundles of axons, called tracts in the CNS and nerves in the PNS.

LO 3.6 Briefly describe four kinds of glial cells.

Neuroanatomical Techniques and Directions

Glial cells, or glia, outnumber neurons in the brain, with about two glia for every three neurons. There are several types of glia, including:

Oligodendrocytes: These glial cells form myelin sheaths around axons in the central nervous system, increasing conduction speed. Unlike Schwann cells in the peripheral nervous system, oligodendrocytes can provide myelin for multiple axons, but they cannot guide axonal regeneration after injury.

Schwann Cells: Found in the peripheral nervous system, Schwann cells also form myelin but can guide axonal regeneration after injury.

Microglia: These small cells respond to injury or disease by multiplying, clearing debris, and triggering inflammation.

Astrocytes: The largest glial cells, astrocytes have star-shaped extensions that help maintain the blood-brain barrier, regulate blood flow, and support synapse formation and neural activity. They also play roles in brain injury responses and cognition.

While glia were once thought to primarily support neurons, research now reveals they perform crucial functions in brain activity, injury response, and overall neural health.

LO 3.7 Compare several neuroanatomical research techniques.

The major challenge in visualizing neurons is not their small size, but rather the dense packing of neurons and the complex intertwining of their axons and dendrites. Simply looking through a microscope at unprepared neural tissue does not reveal much about their structure. To overcome this, neuroanatomy relies on various tissue preparation methods, each highlighting a different aspect of neuronal structure. By combining knowledge from these different preparations, researchers can gain a more comprehensive understanding.

Common Neuroanatomical Techniques

Golgi Stain: One of the most significant discoveries in early neuroscience came in the 1870s with the Golgi stain, discovered accidentally by Italian physician Camillo Golgi. Golgi was attempting to stain the meninges but noticed that a chemical reaction caused silver chromate to invade certain neurons, staining them black. This technique made it possible to view individual neurons, albeit only in silhouette. The Golgi stain is primarily used to study the overall shape of neurons.

Nissl Stain: Although the Golgi stain reveals the shape of a few neurons, it does not indicate the number of neurons in an area. The Nissl stain, developed by German psychiatrist Franz Nissl in the 1880s, overcomes this limitation. Using cresyl violet or similar dyes, the Nissl stain binds to DNA and RNA, molecules abundant in neuron cell bodies. This allows researchers to estimate the number of neurons in an area by counting the Nissl-stained dots, typically in regions with dense neuronal bodies.

Electron Microscopy: While light microscopy has a magnification limit of about 1,500 times, which is insufficient for studying fine details of neuronal structure, electron microscopy provides much higher magnification. This method involves coating thin slices of neural tissue with electron-absorbing substances, which are taken up by different parts of neurons to varying degrees. A beam of electrons is passed through the tissue, and the resulting image—an electron micrograph—captures intricate details of neuronal structure. Scanning electron microscopy produces three-dimensional images, but it has a lower magnification than conventional electron microscopy. Despite its exceptional detail, electron microscopy can sometimes make it harder to visualize general aspects of neuroanatomical structure.

Neuroanatomical Tracing Techniques: These techniques are used to trace the pathways of axons in the brain, either from their cell bodies to their terminals (anterograde tracing) or from their terminals back to their cell bodies (retrograde tracing). In anterograde tracing, a chemical is injected into a cell body, where it is taken up and transported along the axon to the terminal buttons. After several days, brain slices are analyzed to identify the locations of the chemical. Retrograde tracing, on the other hand, involves injecting chemicals into the terminals, which are then transported backward along the axons to the cell bodies.

Each of these techniques has its strengths and weaknesses, and when combined, they provide a detailed and multifaceted view of the nervous system's structure and function.

LO 3.8 Illustrate the neuroanatomical directions.

Anatomy of the Central Nervous System

Note for the sections asking you to list and describe the components of each of the five divisions of the human brain, it is less about what division they belong to, and more about describing each of the ‘components’.

Directional Coordinates in the Nervous System

In the vertebrate nervous system, three main directional axes are used to describe positions and orientations of structures:

Anterior–Posterior: This axis refers to the front (anterior) and back (posterior) of the body or brain. In some contexts, these are also called rostral (anterior) and caudal (posterior).

Dorsal–Ventral: Dorsal refers to the back or top (e.g., top of the head), and ventral refers to the front or bottom (e.g., chest).

Medial–Lateral: Medial means towards the center or midline of the body, while lateral refers to moving away from the midline, towards the outer sides of the body.

Special Considerations in Humans

In humans, the upright posture alters the way we use these directional terms compared to typical quadrupeds (four-legged animals). This results in a different orientation of the cerebral hemispheres relative to the spine and brainstem.

Dorsal and Ventral Complications: The terms dorsal and ventral are applied differently in humans because of the upright posture. For example, in humans, the top of the head (dorsal) and the back (also dorsal) are considered to be in different directions, but they are both labeled as dorsal due to their position relative to the body.

Superior and Inferior: To prevent confusion, superior (top) and inferior (bottom) are often used to describe the top and bottom of the human head, rather than using dorsal and ventral.

Proximal and Distal

These terms are used to describe relative distances from the central nervous system (CNS).

Proximal means closer to the CNS, while distal means farther from the CNS.

Brain Sectioning

The nervous system is often studied by examining slices of brain tissue, which can be cut in three primary planes:

Horizontal Section: A slice made horizontally across the brain.

Frontal (Coronal) Section: A vertical slice that divides the brain into front and back portions.

Sagittal Section: A vertical slice that divides the brain into left and right halves.

Midsagittal Section: A slice down the middle of the brain.

Cross Section: A slice cut perpendicular to the long axis of any structure (such as the spinal cord).

This system of directional terms helps researchers accurately describe the location of brain structures and the relationships between different parts of the nervous system, which is vital for both functional and anatomical studies.

LO 3.9 Draw and label a cross section of the spinal cord.

Structure of the Spinal Cord

1. Gray Matter vs. White Matter:

   • Gray Matter: The inner, H-shaped region of the spinal cord is gray matter. It consists mainly of cell bodies and unmyelinated interneurons.

   • White Matter: Surrounding the gray matter is the white matter, which is made up primarily of myelinated axons. The myelin sheath gives white matter its characteristic glossy white appearance.

2. Gray Matter Anatomy:

   • The dorsal arms of the gray matter are called the dorsal horns.

   • The ventral arms of the gray matter are called the ventral horns.

3. Spinal Nerves:

   • Spinal Nerves: There are 31 pairs of spinal nerves that connect to the spinal cord, one pair on the left and one on the right, at various levels of the spine.

   • Each spinal nerve divides into two roots as it approaches the spinal cord:

     • Dorsal Root

     • Ventral Root

Functions of the Dorsal and Ventral Roots

1. Dorsal Root:

   • The dorsal root carries sensory (afferent) information, meaning it transmits signals from the body to the spinal cord and brain. These axons are unipolar neurons, with their cell bodies located in the dorsal root ganglia, just outside the spinal cord. Many of their synaptic terminals are located in the dorsal horns of the gray matter.

2. Ventral Root:

   • The ventral root carries motor (efferent) information, sending signals from the spinal cord to muscles or organs. These axons are multipolar neurons, with cell bodies located in the ventral horns.

   • Neurons in the somatic nervous system project to skeletal muscles.

   • Neurons in the autonomic nervous system project to ganglia, where they synapse with other neurons that then project to internal organs.

Summary

• The spinal cord is composed of gray matter (cell bodies and unmyelinated neurons) and white matter (myelinated axons).

• The dorsal horns and ventral horns refer to the parts of the gray matter.

• Dorsal root axons are sensory, while ventral root axons are motor, serving the somatic and autonomic nervous systems.

LO 3.10 List and discuss the five major divisions of the human brain.

Understanding the Brain’s Five Divisions

Learning the “Neighborhoods” of the Brain:

Just as learning the names and locations of neighborhoods in an unfamiliar city is essential for navigation, understanding the five primary divisions of the brain is crucial for understanding its organization and function.

Reticular Formation:

The reticular formation is a network of nuclei located in the central core of the brainstem, from the posterior boundary of the myelencephalon to the anterior boundary of the midbrain.

It plays a role in several functions, including sleep, attention, movement, muscle tone regulation, and various cardiac, circulatory, and respiratory reflexes.

Sometimes referred to as the reticular activating system due to its role in arousal, the term "system" can be misleading because the reticular formation has a variety of functions.

The Early Development of the Brain

Embryonic Development:

In the vertebrate embryo, the tissue that becomes the central nervous system (CNS) initially forms a fluid-filled tube.

The first signs of the developing brain appear as three swellings at the anterior end of this tube. These three swellings will eventually develop into the forebrain, midbrain, and hindbrain.

Formation of the Five Divisions:

Before birth, these initial three swellings divide further into five divisions, which form the adult brain:

Telencephalon (the forebrain)

Diencephalon (part of the forebrain)

Mesencephalon (midbrain)

Metencephalon (hindbrain)

Myelencephalon (hindbrain)

This five-part division happens because the forebrain and hindbrain each split into two additional divisions.

Mnemonic for Remembering the Divisions:

A helpful mnemonic for remembering the five divisions is: "The telencephalon is on the top, and the other four divisions follow below it in alphabetical order."

The Adult Brain and Its Divisions

Telencephalon:

The telencephalon grows the most during development, forming the left and right cerebral hemispheres.

Brain Stem:

The other four divisions of the brain (diencephalon, mesencephalon, metencephalon, and myelencephalon) are collectively known as the brain stem. The brain stem supports the cerebral hemispheres and regulates many vital functions.

The Myelencephalon:

The myelencephalon, located at the base of the brainstem, is often referred to as the medulla. This region plays a key role in autonomic functions like heart rate, breathing, and blood pressure.

Summary

The brain is organized into five divisions that develop from the initial three swellings of the neural tube.

The telencephalon (forebrain) grows the most during development and gives rise to the cerebral hemispheres, while the other divisions form the brain stem.

The reticular formation is a crucial network of nuclei involved in several functions, but its role in arousal is just one aspect of its broader involvement in bodily regulation.

LO 3.11 List and describe the components of the myelencephalon.

Myelencephalon (Medulla):

Location: The myelencephalon is the most posterior division of the brain, positioned at the lower part of the brainstem, connecting the brain to the spinal cord.

Function: It is primarily composed of tracts, which are bundles of nerve fibers that transmit signals between the brain and the body. These tracts facilitate communication, allowing for the brain to control and receive information from the body.

Reticular Formation:

Location: The reticular formation is a complex network of about 100 tiny nuclei that spans the central core of the brainstem, from the posterior boundary of the myelencephalon (medulla) to the anterior boundary of the midbrain.

Appearance: Its netlike structure is why it is named the reticular formation ("reticulum" means "little net").

Functions of the Reticular Formation:

The reticular formation plays a role in a variety of functions beyond arousal:

Sleep: It contributes to the regulation of sleep-wake cycles.

Attention: It helps modulate attention and alertness.

Movement: It aids in motor control and coordination.

Muscle Tone: It is involved in maintaining muscle tone.

Autonomic Reflexes: It plays a role in cardiac, circulatory, and respiratory reflexes, ensuring the proper functioning of vital physiological systems.

Reticular Activating System:

The reticular formation is sometimes referred to as the reticular activating system (RAS) because of its involvement in arousal and alertness.

However, the term "system" can be misleading, as the reticular formation's role is much broader, encompassing the regulation of various physiological functions.

Summary:

The myelencephalon (medulla) is responsible for relaying signals between the brain and body, while the reticular formation is a network of nuclei in the brainstem that plays a crucial role in regulating sleep, attention, movement, muscle tone, and various autonomic reflexes.

Though sometimes associated with arousal, the reticular formation has a broader range of functions, making the term "system" less accurate.

LO 3.12 List and describe the components of the metencephalon.

Metencephalon:

The metencephalon houses important structures involved in ascending and descending tracts—bundles of nerve fibers that carry signals between the brain and the body. For example, motor signals from the brain are carried through descending tracts to the muscles, allowing you to move your arms or legs, while sensory signals (such as touch or pain) are carried in the opposite direction through ascending tracts.

It also contains part of the reticular formation, which is involved in regulating sleep cycles, arousal, and alertness. This network helps determine whether you're in a deep sleep or waking up alert, and plays a role in attention (for example, focusing on a conversation in a noisy room).

Pons:

The pons is a prominent structure on the brainstem’s ventral surface (the front-facing side). It forms one of the two main divisions of the metencephalon. Think of it as a relay station that connects the medulla, cerebellum, and higher brain regions.

Function: The pons plays a critical role in regulating breathing. For example, during exercise, the pons helps adjust your breathing rate to meet the increased oxygen demand of your muscles. It also influences sleep, particularly in the REM phase, when you experience vivid dreams. Damage to the pons can result in sleep disturbances or difficulty breathing.

Another key role of the pons is in communication between different parts of the brain. For instance, it helps transmit signals from the motor cortex (which controls voluntary movement) to the cerebellum, ensuring smooth and coordinated movements.

Cerebellum:

The cerebellum, often called the "little brain," is a large, convoluted structure located on the dorsal surface of the brainstem (the back-facing side). It looks like a miniature brain with its folds, or gyri.

Sensorimotor Function: The cerebellum is crucial for the precise control of movements. For example, when you reach for a glass of water, the cerebellum helps you smoothly move your arm and adjust its position as you approach the glass. If you're playing a musical instrument, such as the piano, the cerebellum allows you to make precise finger movements with little thought.

It helps with balance, such as when you're walking or running. The cerebellum processes information from your inner ear and muscles to keep you steady, even when you're walking on an uneven surface like a rocky path.

Adaptation: The cerebellum also helps adapt your movements to changing conditions. For example, if you're walking on ice, your cerebellum helps you adjust your posture to prevent falling. If you're learning a new sport, such as tennis, the cerebellum allows you to adjust your movements to hit the ball accurately.

Cerebellar Damage:

Motor Impairments: Damage to the cerebellum can result in difficulty controlling precise movements. For instance, people with cerebellar damage may struggle to coordinate their hands and fingers when typing or playing a musical instrument. They may also have difficulty walking or performing tasks that require fine motor control, such as buttoning a shirt.

Cognitive Deficits: Interestingly, cerebellar damage doesn’t only impair motor skills. It can also lead to cognitive deficits:

Decision-making: For example, damage to the cerebellum might make it harder to assess situations and make quick decisions, like determining the best course of action when faced with an emergency.

Language difficulties: Individuals with cerebellar damage may also experience problems with speech production or language processing, such as struggling to articulate words clearly or organizing their thoughts into coherent sentences.

These findings suggest that the functions of the cerebellum extend beyond just sensorimotor control. The cerebellum may also play a role in broader cognitive functions, including planning, cognitive flexibility, and emotional regulation. For example, people with cerebellar damage may find it harder to adjust their behavior in social situations or manage emotional responses effectively.

Summary:

The metencephalon contains two major structures: the pons and the cerebellum. The pons is involved in regulating breathing, sleep, and communication between various parts of the brain, while the cerebellum is critical for motor control, balance, and the adaptation of movements. Damage to the cerebellum can impair both movement and cognitive functions, suggesting its involvement in a range of psychological and physiological processes.

LO 3.13 List and describe the components of the mesencephalon.

The mesencephalon, or midbrain, is a crucial division of the brainstem with two main subdivisions: the tectum and the tegmentum. Below is a more detailed breakdown with examples to clarify their functions:

Tectum:

The tectum (which means "roof") is located on the dorsal surface of the mesencephalon, meaning it's on the back-facing side of the midbrain. It is responsible for processing sensory information, particularly related to vision and hearing.

Inferior Colliculi: The posterior pair of bumps in the tectum are called the inferior colliculi, and they have an auditory function. For instance, the inferior colliculi help localize sound in space. When you hear a noise behind you, the inferior colliculi help your brain determine the direction and distance of the sound. This is crucial for auditory processing and sound localization.

Superior Colliculi: The anterior pair of bumps are known as the superior colliculi, and they have a visual-motor function. They play an essential role in directing your body’s orientation toward visual stimuli. For example, if a bright light suddenly flashes in your peripheral vision, the superior colliculi will trigger an involuntary head-turn toward the light. This visual reflex allows you to quickly orient your attention to important visual cues in your environment.

In lower vertebrates, the tectum is entirely involved in visual-motor functions and is sometimes referred to as the optic tectum. This is particularly evident in animals like fish or amphibians, where it is crucial for guiding movements toward visual stimuli, such as when they quickly swim away from predators.

Tegmentum:

The tegmentum is the division of the mesencephalon located ventral (or underneath) to the tectum. It is involved in a wide range of functions, including motor control, pain modulation, and motivation. The tegmentum contains several important structures that are critical for sensorimotor processing and pain regulation.

Periaqueductal Gray (PAG): The periaqueductal gray surrounds the cerebral aqueduct, which is the duct connecting the third and fourth ventricles in the brain. The PAG is especially significant due to its role in mediating the analgesic (pain-reducing) effects of opioid drugs. For instance, when you take a painkiller like morphine, it acts on the periaqueductal gray to block pain signals, making you feel less discomfort. The PAG also plays a role in fear responses and defensive behaviors (like freezing or fleeing) when you encounter dangerous situations.

Substantia Nigra: The substantia nigra, meaning "black substance," is a key structure involved in movement regulation. It's most famous for its role in Parkinson's disease. In healthy individuals, the substantia nigra releases dopamine, a neurotransmitter that helps control voluntary movements. For example, the smooth and coordinated movement of your arms when you walk is aided by dopamine from the substantia nigra. In Parkinson’s disease, the degeneration of the substantia nigra leads to symptoms like tremors and rigidity, as the body can no longer effectively control motor movements.

Red Nucleus: The red nucleus is another structure of the tegmentum that plays a key role in motor control, particularly in limb movement. The red nucleus is involved in motor coordination, especially movements of the arms and legs. For example, when you perform a controlled action like reaching for an object, the red nucleus helps coordinate the movements of your arms and hands. Damage to the red nucleus can impair motor coordination, leading to issues like tremors or difficulty performing smooth, voluntary movements.

Summary:

The mesencephalon plays a significant role in sensory processing (particularly visual and auditory functions) and sensorimotor control. The tectum, with its inferior and superior colliculi, helps process auditory and visual stimuli and coordinates the body's response to those stimuli. The tegmentum, located below the tectum, is crucial for regulating pain, motor control, and other functions, with important structures like the periaqueductal gray, substantia nigra, and red nucleus contributing to these processes.

LO 3.14 List and describe the components of the diencephalon.

Thalamus:

The diencephalon is composed of two primary structures: the thalamus and the hypothalamus. These structures play vital roles in processing sensory information, regulating body functions, and controlling behavior.

Thalamus:

• The thalamus is a large, two-lobed structure that forms the top of the brainstem. One lobe sits on each side of the third ventricle, and the two lobes are connected by a thin bridge of tissue called the massa intermedia, which runs through the ventricle. On the surface of the thalamus, you can see white lamina (layers) made up of myelinated axons, which help with the transmission of electrical signals.

  • Sensory Relay Nuclei: The thalamus is primarily known for its role in relaying sensory information. It contains several sensory relay nuclei, which receive sensory signals, process them, and transmit them to the appropriate sensory areas of the cortex for further processing. Some of the most well-known sensory relay nuclei include:

    • Lateral Geniculate Nucleus: This is involved in the visual system, receiving input from the retina and sending it to the visual cortex in the occipital lobe, which allows you to perceive and interpret visual information. For example, the lateral geniculate nucleus processes information about light, shape, and motion.

    • Medial Geniculate Nucleus: This nucleus is involved in the auditory system, receiving signals from the inferior colliculus in the midbrain and sending them to the auditory cortex in the temporal lobe, which helps you interpret sound. It plays a role in processing various sound qualities such as pitch and volume.

    • Ventral Posterior Nucleus: This is part of the somatosensory system, which processes tactile sensations like touch, temperature, and pain. The ventral posterior nucleus relays information from the skin and other body parts to the somatosensory cortex for perception of sensation.

  • Feedback Signals: An interesting aspect of sensory relay nuclei is that they are not just one-way streets. They receive feedback signals from the areas of the cortex they project to, meaning there is ongoing communication between the thalamus and the cortex. This feedback helps modulate sensory input, contributing to processes such as attention and sensory filtering. For example, when you focus on one specific sound in a noisy room, the thalamus and cortex work together to enhance that signal and suppress irrelevant background noise.

Hypothalamus:

• Located just below the anterior thalamus (with “hypo” meaning “below”), the hypothalamus plays a crucial role in regulating several motivated behaviors, such as eating, sleep, sexual behavior, and the body's homeostasis (the maintenance of stable internal conditions).

  • Hormonal Regulation: The hypothalamus exerts its effects in part by regulating the release of hormones from the pituitary gland, which hangs beneath it on the ventral surface of the brain. The pituitary is sometimes called the “master gland” because it controls the release of hormones that affect growth, metabolism, and reproductive processes. For example, the hypothalamus regulates the release of oxytocin, which is involved in labor and breastfeeding, and antidiuretic hormone (ADH), which helps regulate water balance in the body.

  • Optic Chiasm: On the inferior surface of the hypothalamus is the optic chiasm, where the optic nerves from each eye meet and partially decussate (cross over to the opposite side of the brain). This crossing of fibers ensures that information from the left visual field is processed in the right hemisphere and vice versa. The optic chiasm is essential for binocular vision, helping the brain combine the visual input from both eyes to form a cohesive image of the world.

  • Mammillary Bodies: The mammillary bodies are a pair of spherical nuclei located just behind the pituitary gland. Although they are part of the hypothalamus, they are often mentioned separately due to their involvement in memory processing, particularly in the formation of episodic memories. For instance, damage to the mammillary bodies is linked to memory deficits seen in conditions like Wernicke-Korsakoff syndrome, which is commonly associated with chronic alcohol use and thiamine deficiency.

Summary:

• The diencephalon is a critical brain region involved in both sensory processing and behavioral regulation. The thalamus acts as a relay station for sensory information, processing and transmitting it to the appropriate parts of the cortex for interpretation. The hypothalamus regulates important bodily functions, including motivated behaviors and hormone release through the pituitary gland, and plays a role in visual processing (via the optic chiasm) and memory (via the mammillary bodies).

LO 3.15 List and describe the components of the telencephalon.

Cerebral Cortex

The cerebral cortex, or "cerebral bark," covers the cerebral hemispheres and is composed mainly of small, unmyelinated neurons, giving it a gray color, thus often referred to as "gray matter." Below the cortex lies the white matter, made up of myelinated axons.

Humans have a highly convoluted cerebral cortex, which increases its surface area without expanding the overall brain volume. However, not all mammals share this trait; most are lissencephalic, meaning they have a smooth cortex. The convolutions are categorized into fissures (large furrows), sulci (small furrows), and gyri (ridges between them). The largest fissure, the longitudinal fissure, almost completely separates the cerebral hemispheres, with a few tracts, called cerebral commissures, connecting them. The corpus callosum is the largest of these.

Lobes of the Cerebral Cortex

The lateral surface of each hemisphere is divided by two major fissures: the central and lateral fissures, which separate the cortex into four main lobes: the frontal, parietal, temporal, and occipital lobes. Among the largest gyri are the precentral and postcentral gyri in the frontal and parietal lobes, respectively, and the superior temporal gyrus in the temporal lobe.

The cerebral lobes should not be viewed as functional units. The cortex is better understood as a flat sheet of cells, folded during development into these lobes. Each lobe has associated functions, but it is important to remember that functions are not confined to one specific lobe. For example, the occipital lobes are primarily responsible for visual processing, the parietal lobes for sensation and spatial awareness, the temporal lobes for hearing, language, and memory, and the frontal lobes for motor control and higher cognitive functions like planning and decision-making.

Neocortex

Approximately 90% of the human cerebral cortex is neocortex (also known as isocortex), consisting of six layers. These layers differ in terms of cell body size, density, and types of neurons they contain. Pyramidal cells, which are large and multipolar, are a common type of neuron, while stellate cells are smaller, star-shaped interneurons. Neurons in the neocortex often form mini-circuits that process specific functions within vertical columns.

Notably, the thickness of the layers varies between cortical regions. Sensory areas, for instance, have thick layer IV, which is specialized for receiving sensory input from the thalamus. Conversely, motor areas have thick layer V, which is involved in sending signals from the cortex to the brainstem and spinal cord.

Hippocampus

The hippocampus, located in the medial temporal lobe, is not part of the neocortex. It has only three layers and plays a critical role in certain types of memory. Its shape, resembling a seahorse, gives it its name ("hippocampus" meaning "sea horse").

LO 3.16 List and describe the components of the limbic system and of the basal ganglia.

The subcortical portion of the telencephalon, although largely occupied by axons connecting to and from the neocortex, contains several significant nuclear groups. Some of these structures are associated with either the limbic system or the basal ganglia system. It's important to note that the term "system" in these contexts can be misleading, as it implies a level of certainty that is not fully supported. There is ongoing uncertainty about the exact roles these systems play, the structures they should include, and whether it's even appropriate to conceptualize them as single systems. However, these terms still provide a useful framework for understanding the organization of several subcortical structures.

Limbic System

The limbic system is a circuit of midline structures that encircle the thalamus. The name "limbic" means "ring," and this system is primarily involved in regulating motivated behaviors, including the classic "four F’s": fleeing, feeding, fighting, and sexual behavior. Major components of the limbic system include the amygdala, hippocampus, mammillary bodies, fornix, cingulate cortex, and septum.

The limbic circuit can be traced starting from the amygdala, an almond-shaped nucleus located in the anterior temporal lobe. The hippocampus, positioned posterior to the amygdala, runs beneath the thalamus in the medial temporal lobe. From here, the circuit continues with the cingulate cortex, a large strip of cortex in the cingulate gyrus that encircles the dorsal thalamus, and the fornix, which is the major tract in the limbic system. The fornix leaves the dorsal end of the hippocampus, arcs forward along the superior surface of the third ventricle, and terminates in the septum and mammillary bodies. The septum, a midline nucleus, is located at the anterior tip of the cingulate cortex. Multiple tracts connect the septum and mammillary bodies with the amygdala and hippocampus, completing the limbic ring.

Key Structures and Functions:

• Amygdala: Primarily involved in processing emotions, particularly fear.

• Hippocampus: Plays a role in memory formation.

• Hypothalamus: Regulates motivated behaviors such as eating, sleep, and sexual activity.

• Cingulate Cortex and Fornix: Serve as important pathways in the limbic system, linking various components.

• Septum and Mammillary Bodies: These structures also play roles in the coordination of emotional responses and motivated behaviors.

The hippocampus, hypothalamus, and amygdala have been studied more extensively, with each contributing to essential behavioral functions such as memory, emotion, and motivation.

Basal Ganglia

The basal ganglia consist of several structures, including the caudate, putamen, and globus pallidus. The caudate and putamen, which have a striped appearance, are collectively known as the striatum. The major output of the striatum is the globus pallidus, a pale, circular structure located between the putamen and the thalamus.

The basal ganglia are crucial for the execution of voluntary motor responses and decision-making processes. One of the key areas of interest within the basal ganglia is the nucleus accumbens, located in the medial portion of the ventral striatum. This area is implicated in the rewarding effects of addictive substances and other reinforcers.

A significant connection within the basal ganglia is the pathway from the substantia nigra in the midbrain to the striatum. The deterioration of this pathway is associated with Parkinson's disease, which is characterized by symptoms such as rigidity, tremors, and difficulty in initiating voluntary movement.

Conclusion

The limbic system and basal ganglia are essential in understanding the regulation of behavior, emotion, motivation, and movement. While these systems are not yet fully understood, they provide a framework for conceptualizing the intricate network of subcortical structures involved in human behavior. Further research into these systems will continue to illuminate their roles in both normal and pathological states.

Week one lecture:

What is biopsychology?

Fundamental curiosity about the biological basis of behavior: e.g. thought, emotions, actions, consciousness, the brain’s capacity, what makes us unique or different compared to other living things Understanding, diagnosing, treating and supporting neurological and psychological conditions The opportunity to enhance human potential e.g. Optimising learning and behaviour, computer-brain interfaces, AI etc

The scientific study of the biology of behaviour

The core goal of biological psychology is to objectively characterise and understand behaviour Behavior here is defined as any observable action, reaction, or process — whether conscious or unconscious, voluntary or involuntary — through which an organism interacts with its environment.

Historial foundations of biopsychology

As psychologists, you will be assessed against core competencies (e.g. applies scientific knowledge to inform safe and effective practice, safe ethical conduct, demonstrates health equity etc.) As researchers, we make important theoretical and translational contributions to psychology*; e.g. “What is the nature of disease?” “How do we determine the validity of diagnostic concepts?” “How does disease impact our personhood?” History provides us with ‘conceptual competence’

Things to think about: How different types of investigation have evolved, e.g. Invasive methods Non-invasive methods Psychopharmacology Cellular and molecular Computational modelling How available technology has shaped methods of investigation over time How communication, and dominance or privileging of particular languages or methods of communication, has shaped the global understanding and practice of biological psychology over time How dominant societal attitudes and assumptions, theoretical frameworks, and philosophies have shaped research and clinical practice over time

1600 BC: Edwin Smith Papyrus

• First written reference to the word “brain” in a surgical context.

• Describes brain structure and early observations of brain function, including how injuries to one side of the brain affect the opposite leg.

6th Century BCE: Sushruta Samhita

• Recognized the brain's role in cognition and behavior.

• Early biopsychological model linking mental health to biological factors (Vata, Pitta, Kapha).

• Introduced the idea of mental health treatment through surgery, diet, and herbs.

5th-4th Century BCE: Brain as the Centre of Thought

• Alcamaeon of Croton (500 BCE) identified the brain as the center of thought.

• Hippocrates (460-370 BCE) refuted the heart-centered thought theory and recognized epilepsy’s brain origin.

• Herophilus (335-280 BCE) illustrated the central nervous system and identified the brain's role in thought and sensation.

10th Century: Ibn Sina’s Canon of Medicine

• Integrated global medical knowledge and introduced empirical observation, influencing medicine for centuries.

16th Century: René Descartes

• Introduced mind-body dualism, suggesting that mind and body are separate entities.

• Proposed reflexes, where external stimuli trigger automatic bodily responses, laying the foundation for neuroscience.

19th Century: Darwin’s Evolutionary Theory

• Darwin's work emphasized the biological basis for emotional and cognitive traits across species.

• Suggested that emotions serve adaptive functions and can be observed in both humans and animals.

18th-19th Century: Technological Advances

• Santiago Ramón y Cajal made groundbreaking discoveries in cellular imaging and microscopy.

• Joseph Erlanger & Herbert Gasser further advanced the understanding of nerve impulse transmission.

20th Century: Advancements in Neuroscience and Psychopharmacology

• Watson and Crick discovered DNA in 1953, advancing our understanding of genetics in brain function.

• 1960s psychopharmacology advancements contributed to the understanding of mental disorders as discrete entities with specific treatments.

20th-21st Century: Computational Neuroscience

• Began investigating if the brain operates like a Turing Machine and developed models like Parallel Distributed Processing and Bayesian inference.

• The brain’s role in predictive coding suggests that mental health conditions could result from differences in prediction and inference processes.

Part 3: Dominant frameworks for understanding biological psychology … and how this ties to this unit

Biopsychology's Development in the Modern Era

19th Century: Biological Foundations of Psychiatry

• Emil Kraepelin: Revolutionized the classification of mental disorders by emphasizing biological and neurological foundations.

• Santiago Ramón y Cajal: With his pioneering work in microscopy, he discovered the structure of neurons, significantly contributing to the understanding of brain cells and their connections.

20th Century: Standardization and Growth of Psychiatry

• Freud (1856-1939): His psychoanalytic theory dominated, though it was soon challenged by a growing biological understanding of mental disorders.

• Post-WWII (1947-1952): DSM & ICD-6: Efforts were made to better classify and diagnose psychiatric conditions.

• DSM-III (1980): Prof. Robert Spitzer’s revision of the Diagnostic and Statistical Manual of Mental Disorders (DSM) into a more empirically-based diagnostic system, moving away from psychoanalysis and aligning psychiatry more closely with biological medicine.

• DSM-V (2013): Led by Prof. Thomas Insel, a shift was made toward dimensional and spectrum-based approaches to diagnosis, moving away from a view of mental disorders as discrete, separate entities.

Contemporary Trends and Critiques

Technological and Methodological Advances

• 20th Century (Technological Advances): Developments in cellular imaging, nerve cell recordings, and neuroplasticity expanded understanding of the brain's complexity.

• Computational Neuroscience: The exploration of how computers and brains may function similarly, including models like predictive coding that see the brain as trying to minimize uncertainty.

Bias and Sociocultural Considerations

• Historical Use of Biology in Justifying Harm: The misuse of biological theories (e.g., brain size or genetic determinism) to justify colonialism, slavery, eugenics, and other discriminatory practices.

• Contemporary Issues: The inclusion of homosexuality in the DSM until 1973 and ongoing debates about genetic and biological determinism in mental health.

Critical Thinking in Biopsychology

The growing understanding of the brain in both historical and modern contexts has necessitated critical thinking in biopsychology:

• Evaluating Evidence: Psychologists and researchers must assess the quality, reliability, and validity of data and arguments.

• Conceptual Humility: Recognizing the limitations of scientific and philosophical endeavors and appreciating diverse perspectives in explaining mental health and brain function.

• Sociocultural Bias: The need to be aware of dominant societal perspectives that might reflect and perpetuate biases in psychological practices.

Conclusion

The study of the brain and mental health has evolved from early anatomical observations to sophisticated, multidimensional approaches in the 21st century. Understanding biopsychology requires not only an appreciation of the scientific advancements but also a critical lens through which biases and assumptions can be questioned and examined. The development of the Research Domain Criteria (RDoC) project and other current initiatives highlight a growing commitment to more nuanced, dimensional models of mental health that consider the biological, psychological, and social factors at play.