Neuroanatomy Introduction

Nervous System Functions

• The nervous system is responsible for detecting environmental changes and coordinating responses within an organism.
• Cognition, muscle coordination, and memory storage are all functions attributed to the nervous system.
• The nervous system's ability to interact with and adapt to various environments is what makes it complex and adaptive.
• Learning and memory are higher functions associated with the nervous system.
• The nervous system can be impacted by diseases, trauma, or developmental issues.
• The nervous system contributes to maintaining homeostasis by coordinating muscle and gland responses to stimuli.

Neurones

• A neurone is commonly referred to as a nerve cell.
• The human body contains approximately 100 billion neurones.
• One of the main functions of a neurone is to receive and integrate information from sensory receptors or other neurones.
• Neurones contribute to the body's response to stimuli by transmitting signals to other neurones or effector organs.
• Neurones play a crucial role in maintaining homeostasis by transmitting signals that coordinate activities and responses in the body.
• Neurones process and integrate signals from sensory receptors or other neurones.

Neurone Function and Structure

• The cell membrane of a neurone is responsible for transmitting and maintaining electrical signals.
• Neurones communicate with each other through chemical synapses.
• The cell body (soma) of a neurone contains the nucleus and supports metabolic activities.
• Dendrites receive incoming signals from other neurones or sensory receptors.
• The primary role of an axon is to conduct electrical impulses away from the cell body.
• Nerve terminals (axon terminals) release neurotransmitters to communicate with adjacent cells.
• Neurones come in a variety of shapes and sizes but share core features.

Neuronal Resting Potential

• The typical resting potential of a neuron is -70 mV. This means the inside of the neuron is negatively charged compared to the outside.

Depolarization

• Sodium ions (Na⁺) rushing into the cell after a threshold is reached triggers depolarization. This influx of positive charge makes the inside of the neuron more positive.
• The threshold value is around -55 mV. Once this threshold is reached, an action potential is triggered.

Repolarization

• During repolarization, potassium channels open, allowing K⁺ to exit the cell. This outflow of positive charge makes the inside of the neuron more negative, bringing the membrane potential back towards its resting state.

Sodium-Potassium Pump

• The sodium-potassium pump actively transports sodium ions (Na⁺) out of the cell and potassium ions (K⁺) into the cell, restoring ion balance.
• This pump plays a crucial role in maintaining the resting potential and preparing the neuron for another action potential.

Refractory Period

• The refractory period follows an action potential, during which the neuron is less responsive to further stimuli.
• This period ensures that the action potential travels in one direction along the axon.

Action Potential Propagation

• An action potential propagates along an axon as a wave of depolarization and repolarization moving along the membrane.
• This wave of electrical activity is caused by the sequential opening and closing of sodium and potassium channels.

Peak of Action Potential

• The peak of an action potential occurs when the membrane potential reaches around +30 mV.
• At this point, the sodium channels close, and repolarization begins.

Synapses

• Synapses are the junctions between the axon terminal of one neuron and the dendrite or cell body of another neuron.
• The space between the presynaptic and postsynaptic neurons is called the synaptic cleft.

Neurotransmitters

• Neurotransmitters are chemical messengers released from vesicles in the presynaptic neuron.
• When neurotransmitters bind to receptors on the postsynaptic membrane, they can change the membrane potential of the postsynaptic cell.

Depolarization of the postsynaptic membrane

• Depolarization makes the membrane potential more positive and can initiate an action potential.

Enzymes in the synaptic cleft

• Enzymes in the synaptic cleft break down neurotransmitters to stop their action and clear the synapse.

Hyperpolarization of the postsynaptic membrane

• Hyperpolarization makes the membrane potential more negative, inhibiting the likelihood of an action potential.

Synapses

• Synapses are the junctions between the axon terminal of one neuron and the dendrite or cell body of another.
• The space between the presynaptic and postsynaptic neurons is called the synaptic cleft.
• Neurotransmitters are chemical messengers released from vesicles in the presynaptic neuron.
• Neurotransmitters can change the membrane potential of the postsynaptic cell when they bind to receptors on the postsynaptic membrane.

Action Potential

• Depolarization of the postsynaptic membrane makes the membrane potential more positive and can initiate an action potential.
• Hyperpolarization of the postsynaptic membrane makes the membrane more negative and inhibits the likelihood of an action potential.

Enzymes

• Enzymes in the synaptic cleft break down neurotransmitters to stop their action and clear the synapse.

Lambert-Eaton Myasthenic Syndrome (LEMS)

• Antibodies target voltage-gated calcium channels on the presynaptic nerve terminal
• Impaired calcium influx results in decreased release of acetylcholine (ACh)
• Primarily affects proximal muscles such as the shoulders and hips

Myasthenia Gravis (MG)

• Antibodies target acetylcholine receptors on the postsynaptic muscle membrane
• Antibody attack reduces the number of available receptors for acetylcholine
• Muscle weakness worsens with activity and improves with rest
• Most commonly affects muscles controlling eye movements, facial expressions, and swallowing

Sensory Neurones (Afferent Neurones)

• Transmit impulses from sensory receptors to the CNS
• Allow the brain to perceive sensations

Motor Neurones (Efferent Neurones)

• Transmit impulses from the CNS to muscles or glands
• Innervate skeletal muscles, also known as motor neurones

Interneurones

• Located entirely within the CNS
• Connect sensory and motor pathways within the CNS
• Process information and coordinate responses between sensory and motor neurones

Role of Neuroglia

• Neuroglia cells support and maintain the proper functioning of neurons.

Oligodendrocytes

• Oligodendrocytes are a type of neuroglia cell that forms the myelin sheath in the central nervous system (CNS).
• The myelin sheath increases the rate of action potential conduction along axons.

Astrocytes

• Astrocytes are another type of neuroglia cell that is involved in forming the blood-brain barrier.
• They also provide structural and metabolic support to neurons.

Microglia

• Microglia cells act as immune cells in the CNS, performing phagocytic roles.
• They maintain homeostasis and respond to tissue damage or pathogens.

Nervous System Development

• The ectoderm germ layer is responsible for the formation of the neural tube during early embryonic development, specifically in the third week.
• The neural tube develops into the central nervous system by the fifth week.
• The neural tube differentiates into three primary brain vesicles: prosencephalon, mesencephalon, and rhombencephalon.
• The prosencephalon develops into the telencephalon and diencephalon.
• The telencephalon forms the cerebral hemispheres by the seventh week.
• The diencephalon contains the thalamus which relays sensory and motor signals.
• The mesencephalon remains as the midbrain, responsible for visual and auditory processing.
• The rhombencephalon differentiates into the metencephalon and myelencephalon.
• The metencephalon develops into the pons and cerebellum.
• The pons aids in communication within the brain, while the cerebellum contributes to motor control and balance.
• The myelencephalon forms the medulla oblongata, which controls essential life functions like heart rate and breathing.

Brain Stem Structures

• The brain stem is comprised of the medulla oblongata, pons, and midbrain.
• The cerebellum is not part of the brain stem.

Brain Stem Function

• The brain stem's primary role is controlling automatic functions like heart rate and breathing.

Brain Stem and Spinal Cord

• The brain stem acts as a pathway for neural tracts, conveying signals between the brain and the spinal cord.

Cerebrospinal Fluid (CSF)

• CSF is produced by the choroid plexus in the ventricles.
• Its function is to cushion the brain, remove waste, and supply nutrients and hormones.
• CSF circulates through the ventricles and subarachnoid space and is ultimately reabsorbed into the bloodstream.

Ventricles

• The third ventricle is located in the diencephalon.
• The lateral ventricles are connected to the third ventricle by the interventricular foramen.
• The fourth ventricle is located between the brainstem and cerebellum.

Cerebrospinal Fluid (CSF) Protection

• CSF acts as a cushion and immune barrier for the brain, guarding against potential injuries and infections.

CSF Production

• CSF is produced by the choroid plexus, a network of capillaries located within the brain's ventricles.

CSF Volume

• The brain typically contains about 150 ml of CSF at any given time.

CSF Reabsorption

• CSF is reabsorbed back into the bloodstream through arachnoid villi, finger-like projections extending into the subarachnoid space.

Hydrocephalus

• Hydrocephalus is a condition where excess CSF accumulates, leading to increased intracranial pressure.
• This pressure can damage brain tissues and cause various neurological issues.

Causes of Hydrocephalus

• Hydrocephalus can arise from various factors, including:
  • Congenital defects (present at birth)
  • Tumors affecting CSF flow
  • Infections
  • Brain bleeding

Hydrocephalus Treatment

• Common treatments for hydrocephalus include:
  • Placement of a shunt system to drain excess CSF
  • Endoscopic third ventriculostomy (ETV) procedure, which creates an alternative pathway for CSF flow

Endoscopic Third Ventriculostomy (ETV)

• ETV aims to create a new drainage route for CSF by surgically connecting the third ventricle to the subarachnoid space.

Grey Matter

• Composed primarily of nerve cell bodies (soma) and dendrites.
• Found on the surface of the cerebral hemispheres, forming the cerebral cortex.
• Plays a crucial role in processing information, including sensory perception, memory, and decision-making.

White Matter

• Composed mainly of myelinated axons.
• Myelin sheath provides the white color.
• Serves as a communication network, connecting different grey matter areas and transmitting information between them.

Relationship Between Grey and White Matter

• Grey matter is responsible for processing information.
• White matter acts as the communication network between different grey matter areas.

Function of Myelin

• Insulates axons, which facilitates rapid transmission of nerve impulses.

Brain Nuclei

• Nuclei in the brain are clusters of nerve cell bodies (neurons) that share similar functions and connections.
• Function: They process and relay specific types of information, such as motor commands or sensory input from various parts of the body.
• Location: Motor neurons controlling related muscle groups are often organized within nuclei clusters.
• Importance: Nuclei play significant roles in the central nervous system (CNS) by processing and relaying information.
• Composition: They consist of nerve cell bodies that are functionally related, meaning they work together to achieve a specific task.
• Example: A nucleus might be responsible for relaying visual information from the eyes to the brain for interpretation.

Central Nervous System (CNS)

• Consists of the brain and spinal cord.
• Primarily responsible for processing and integrating sensory information, generating thoughts, and initiating motor responses.
• The spinal cord acts as a conduit for signals between the brain and the body, playing a role in reflex actions.

Peripheral Nervous System (PNS)

• Includes all nerves outside the CNS, connecting the brain and spinal cord to the body.
• Cranial nerves arise from the brain and transmit sensory and motor information for the head and neck.
• Spinal nerves are grouped based on their origin in the spinal cord and serve specific regions:
  • Cervical nerves: Serve the neck and upper limbs.
  • Thoracic nerves: Supply the chest and abdominal muscles.
  • Lumbar nerves: Serve the lower back and parts of the lower limbs.
  • Sacral nerves: Serve the pelvic region and lower limbs.

The Autonomic Nervous System (ANS)

• Regulates involuntary bodily functions such as heart rate, digestion, and breathing.
• Part of both the central nervous system (CNS) and the peripheral nervous system (PNS).

Sympathetic Nervous System

• Prepares the body for stressful or high-energy activities.
• Increases heart rate, dilates airways, and diverts blood flow to muscles.
• Often referred to as the "fight or flight" response.

Parasympathetic Nervous System

• Promotes energy storage, digestion, and relaxation.
• Slows heart rate, constricts airways, and promotes digestion.
• Complementary and often opposite effects to the sympathetic nervous system to maintain homeostasis (balance).

The Relationship Between the Sympathetic and Parasympathetic Systems

• Work together to maintain a balanced internal environment.
• The sympathetic system prepares the body for action, while the parasympathetic system promotes rest and recovery.

Innervation of Muscles and Glands

• The ANS innervates smooth muscle, cardiac muscle, and secretory glands, but not skeletal muscles.

Protection of the Brain and Spinal Cord

• The bones of the skull and vertebral column provide the outermost protection for the brain and spinal cord.

Meninges

• The meninges are a three-layered membrane that protects the brain and spinal cord.
• The three layers are:
  • Dura mater: The tough, outermost layer of the meninges that attaches to the inner surface of the skull.
  • Arachnoid mater: The middle layer with a web-like structure.
  • Pia mater: The innermost layer that adheres closely to the surface of the brain and spinal cord.

Subarachnoid Space

• The space between the arachnoid mater and pia mater is called the subarachnoid space.
• The subarachnoid space contains cerebrospinal fluid (CSF).

Cerebrospinal Fluid (CSF)

• The primary function of CSF is to cushion the central nervous system (CNS) and provide a protective barrier.

Scalp

• The scalp is an additional protective structure that covers the skull.

Blood Supply to the Brain

• Internal carotid arteries are the primary arteries supplying the anterior part of the brain.
• The internal carotid arteries branch into the anterior cerebral artery and middle cerebral artery.
• The vertebral arteries originate from the subclavian arteries.
• The vertebral arteries merge to form the basilar artery.
• The vertebral and basilar arteries primarily supply the cerebellum and brainstem.
• The Circle of Willis is a circular network of arteries at the base of the brain.
• The Circle of Willis serves as a collateral blood flow pathway in case of an arterial blockage.
• The Circle of Willis is formed by the internal carotid and vertebral arteries.

Brain Veins

• Brain veins are unique because they lack valves, allowing blood to flow in either direction.
• This is unlike other veins in the body which have one-way valves to prevent backflow.

Deep Cerebral Veins

• Deep cerebral veins are responsible for draining blood from the forebrain and deeper structures of the brain.

Superficial Veins

• Superficial veins sit in the subarachnoid space and drain blood from the outer parts of the brain

Dural Veins

• Dural venous sinuses are channels located between the layers of the dura mater.
• These sinuses collect blood from the brain veins.
• The superior sagittal sinus is a primary example of a dural venous sinus.

Blood Drainage

• Blood collected in the dural venous sinuses drains into the internal jugular vein.
• The internal jugular vein then carries deoxygenated blood from the brain back to the heart.

Brain Stem Structure and Function

• The midbrain is a part of the brain stem involved in visual and auditory processing.
• The pons is also part of the brain stem and is responsible for coordinating facial movements and acting as a communication bridge between different brain areas.
• The medulla oblongata is another part of the brain stem and is responsible for regulating heartbeat and blood pressure, and manages reflexes like coughing and swallowing.
• The thalamus is located above the midbrain and acts as a relay station for sensory and motor signals to the cerebral cortex, contributing to consciousness.
• Cranial nerves originating from the brain stem control functions like eye movement, facial sensation, and swallowing.
• The brain stem serves as a pathway for sensory and motor tracts between the brain and spinal cord.

The Medulla Oblongata

• Vital Role: The medulla oblongata is crucial for life as it controls involuntary functions.
• Essential Functions: It regulates heart rate, breathing rhythm, and reflexes like coughing and sneezing.
• Non-Medulla Function: Complex problem-solving is not a function of the medulla oblongata.
• Neural Communication: The medulla acts as a relay center, transmitting information between the thalamus and spinal cord.
• Anatomical Location: The caudal medulla is closest to the spinal cord.
• Cranial Nerve Importance: The vagus nerve (CN X) originates from the medulla and governs heart rate and digestion.
• Hypoglossal Nerve Function: The hypoglossal nerve (CN XII) regulates tongue movements, vital for speech and swallowing.
• Medulla and Pons: The rostral medulla is adjacent to the pons.
• Glossopharyngeal Nerve Role: The glossopharyngeal nerve (CN IX) controls taste, swallowing, and salivation.

Location and Size

• The pons is situated between the medulla oblongata and the midbrain.
• The pons is approximately 2.5 cm in length.

Function

• The pons serves as a relay center, connecting the cerebellum and cerebrum.
• The pons plays a crucial role in regulating breathing patterns.
• The pons is involved in the sleep-wake cycle and REM sleep.

Cranial Nerves

• The facial nerve (CN VII) originates from the pons and controls facial expressions.
• The vestibulocochlear nerve (CN VIII) originates from the pons and is responsible for hearing and balance.
• The abducens nerve (CN VI) originates from the pons and controls lateral eye movement.
• The trigeminal nerve (CN V) originates from the pons and is responsible for facial sensation, chewing, and muscle control.

Midbrain Functions

• Primary function: Controlling eye movement and processing auditory and visual information
• Contains: Tectum (dorsal portion) and Tegmentum (ventral portion)

Tectum (Dorsal Portion)

• Superior colliculi: Responsible for coordinating head and eye movements in response to visual stimuli
• Inferior colliculi: Primary role in auditory processing and sound localization

Tegmentum (Ventral Portion)

• Associated with: Maintaining arousal and alertness

Cranial Nerves

• Originate from the midbrain:
  • Oculomotor nerve (CN III): Controls most eye movements and pupil constriction
  • Trochlear nerve (CN IV): Controls the superior oblique muscle, which rotates the eye downwards and outwards

Reticular Formation: Location and Connections

• The reticular formation extends throughout the brainstem, connecting the medulla to the midbrain.
• The reticular formation has both incoming (afferent) and outgoing (efferent) connections, reaching various parts of the central nervous system (CNS).
• Axons within the reticular formation are long, allowing for transmission of signals over significant distances.

Reticular Formation: Key Functions

• The reticular formation plays a vital role in regulating arousal and consciousness.
• It contributes to controlling heart rate and blood pressure through interactions with the autonomic nervous system.
• The reticular formation is involved in regulating the rate and depth of breathing, in coordination with the medulla oblongata.
• The reticular formation's influence on maintaining alertness and regulating the sleep-wake cycle makes it crucial for survival.

The Thalamus: A Key Relay Station in the Brain

• The thalamus processes and relays sensory and motor signals to the cerebral cortex, regulating consciousness, sleep, and alertness.
• It's situated between the cerebral hemispheres, resembling the size of a small hen's egg.
• The thalamus is the biggest component of the diencephalon, a part of the brain that also includes the hypothalamus.
• The thalamus receives and transmits both sensory and motor information, serving as a critical hub for communication within the brain.
• It's supplied with blood by branches of the posterior cerebral artery.
• Its central location within the brain allows it to easily relay information to and from different regions, crucial for its role in consciousness and alertness.

Unilateral Brainstem Lesions: Causes and Symptoms

• Common Causes: Cerebrovascular accidents (CVAs), tumors, multiple sclerosis (MS)

• Ipsilateral Cranial Nerve Dysfunction: Damage to cranial nerves on the same side as the lesion, leading to motor or sensory issues.

• Contralateral Spastic Hemiparesis: A common outcome affecting the opposite side of the body, presenting as weakness and spasticity.

• Abnormal Babinski Sign: Indicates upper motor neuron damage, characterized by an upward extension of the big toe when the sole of the foot is stroked.

Bilateral Brainstem Lesions: Severity and Impact

• Severe Damage: Can lead to life-threatening outcomes such as coma or death due to damage to vital centers.

• Vital Centers Affected: Centers that control respiration and circulation, essential for life.

• Hyperreflexia: Exaggerated reflexes and increased spasticity, a potential outcome of unilateral brain stem lesion.

• Contralateral Hemisensory Loss: Loss of sensation on the side opposite to the lesion.

The Limbic System Structures & Their Functions

• The amygdala plays a crucial role in processing emotions, particularly fear and aggression. This structure is directly involved in the fear response.
• The hippocampus is essential for forming and consolidating memories, including both short-term and long-term memories. It plays a vital role in memory formation and recall.
• The hypothalamus manages autonomic functions like hunger, thirst, body temperature, and the sleep-wake cycle. It connects to the endocrine system and influences hormone release.
• The basal ganglia is associated with motor control, coordinating movement and learning. It plays a crucial role in smooth and coordinated movements.

Amygdala: Role in Cognition and Emotion

• The amygdala plays a critical role in emotional and social behaviors, as well as in episodic-autobiographical memory (EAM), which involves recalling personal experiences tied to emotions.
• The amygdala is particularly associated with negative emotions like fear, anxiety, and aggression.
• The amygdala is involved in evaluating facial expressions and recognizing emotional cues in others, contributing to social processing.
• The left amygdala is suggested to be involved in both positive (happiness) and negative (fear, anxiety, sadness) emotions.
• The right amygdala is more strongly associated with negative emotions, particularly fear and sadness, and is involved in declarative memory, which is the conscious recall of facts and events.
• The amygdala plays a critical role in attentional processing, influencing how emotional stimuli are perceived and responded to.

The Hippocampus and Memory

• The hippocampus is a brain structure crucial for transferring short-term memories into long-term storage.
• This process is known as memory consolidation.
• The hippocampus is heavily involved in spatial memory, which is essential for navigation and understanding spatial relationships.

Hippocampus & Conditions

• Damage to the hippocampus often leads to the inability to form new memories and short-term memory loss.
• A shrunken hippocampus has been linked to cognitive and emotional regulation issues, including schizophrenia and severe depression.

Hormonal Influence on the Hippocampus

• Oestrogen has a positive impact on the hippocampus, potentially increasing neural connectivity.

Clinical Implications

• Health and function of the hippocampus are vital for cognitive health.
• Deterioration of the hippocampus is linked to many neurological and psychiatric conditions, including Alzheimer's.
• Oestrogen's positive effect on the hippocampus is seen as a potential treatment avenue for Alzheimer's disease.
• The hippocampus plays a key role in spatial memory, which is essential for navigation and understanding our surroundings.

The Basal Ganglia: An Overview

• The basal ganglia are a group of structures located deep within the cerebral hemispheres.
• These structures play a crucial role in facilitating movement, inhibiting unwanted movements, and regulating behavior.

Key Components of the Basal Ganglia

• The basal ganglia include the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra.
• The hippocampus, however, is not part of the basal ganglia.

The Substantia Nigra's Significance

• The substantia nigra, a structure in the midbrain, is part of the basal ganglia.
• It is particularly important for movement regulation as it is responsible for producing dopamine.

Functionality of the Basal Ganglia

• The basal ganglia enable coordinated movements by facilitating the desired action and inhibiting counter-movements.
• This is essential for tasks like smoothly reaching for an object.
• The basal ganglia contribute to habit formation and action selection, playing a significant role in behavior.

Location of the Subthalamic Nucleus

• The subthalamic nucleus, one of the components of the basal ganglia, is located in the diencephalon.

Parkinson's Disease

• Degeneration of dopaminergic neurons in the substantia nigra is the primary impairment
• Common symptom: Rigidity and bradykinesia (slow movement)
• Impaired ability to inhibit contradictory movements and initiate smooth movement

Huntington's Disease

• Caused by the unusual activity of the globus pallidus
• Characterized by jerky and writhing involuntary movements known as chorea
• Progressively worsens, affecting movement, cognition, and psychiatric health

Basal Ganglia and Other Conditions

• Reduced dopamine levels due to basal ganglia degeneration are associated with Parkinson's disease
• Scientists are investigating how disruptions or malfunctions in the basal ganglia's neural circuits may contribute to Tourette’s syndrome, schizophrenia, and OCD

Hypothalamus: Maintaining Homeostasis

• The hypothalamus is the brain region primarily responsible for maintaining homeostasis, the body's stable internal environment.
• It accomplishes this by regulating both autonomic and endocrine functions.

Functions of the Hypothalamus

• Regulation of Body Temperature: The hypothalamus monitors and adjusts body temperature through sweating, shivering, and other mechanisms.
• Thirst and Hunger Control: This region monitors blood nutrient levels and regulates hunger and thirst to ensure adequate nutrient intake.
• Sleep Regulation: The hypothalamus plays a critical role in regulating sleep-wake cycles, ensuring the body gets sufficient rest.
• Hormonal Control: The hypothalamus produces hormones that control the pituitary gland, which in turn regulates the endocrine system, impacting everything from growth to reproduction.

Hypothalamic Inputs

• Neural Inputs: Receives signals from various brain regions, providing information for decision-making.
• Circulatory Inputs: Monitored blood contains a wealth of information about the body's internal state:
  • Blood Pressure: Hypothalamus responds to pressure fluctuations, regulating blood flow.
  • Temperature: The hypothalamus uses this data to adjust body temperature.
  • Nutrient Levels: Helps regulate hunger and thirst based on blood glucose and other nutrient levels.
  • Hormonal Signals: Responds to various hormones in the blood, providing insight into the body's overall state.

Hypothalamus and Internal Signals

• The hypothalamus receives information about the body's internal state through various signals:
  • Chemical Signals from Blood: Blood composition, including electrolyte balance, is essential for proper functioning.
  • Hormonal Signals in the Blood: Provides the hypothalamus with insights into the body's current metabolic state.

Hypothalamus Function

• The hypothalamus is responsible for maintaining homeostasis - regulating autonomic and endocrine functions.
• It controls body temperature, thirst and hunger, sleep regulation.
• It receives information about the body's state through neural and circulatory inputs:
  • Neural inputs from the brain provide information about sensory and emotional states.
  • Circulatory inputs consist of blood pressure, temperature, nutrient levels, and hormones.
• Hormones in the blood provide the hypothalamus with information about the body's metabolic state, including electrolyte balance.

The Hypothalamus and Sleep

• The hypothalamus plays a crucial role in regulating sleep as part of its homeostatic functions.

The Pituitary Gland: Master Regulator

• The pituitary gland is often called the "master gland" due to its crucial role in regulating various hormonal functions across the body.
• It is located at the base of the brain, connected to the hypothalamus via a stalk-like structure.
• The pituitary gland is divided into two main lobes: the anterior pituitary (front) and the posterior pituitary (back).

Posterior Pituitary

• The posterior pituitary does not produce its own hormones but stores and releases hormones synthesized by the hypothalamus.
• Vasopressin (antidiuretic hormone), released from the posterior pituitary, plays a vital role in regulating water balance in the body.

Anterior Pituitary

• The anterior pituitary synthesizes and secretes a range of hormones that control crucial bodily functions.
• Adrenocorticotropic hormone (ACTH) stimulates the adrenal glands to produce cortisol, which is essential for stress response and energy regulation.
• Luteinizing hormone (LH) is responsible for stimulating ovulation in females and testosterone production in males.
• Growth hormone (GH) promotes growth, cell repair, and metabolism, playing a key role in development.
• Prolactin is responsible for stimulating milk production after childbirth in women.
• Thyroid-stimulating hormone (TSH) regulates the thyroid gland's release of thyroid hormones, essential for metabolism and growth.

Hypothalamus and Pituitary Tumours

• Tumours in the hypothalamus or pituitary gland can disrupt hormone production, leading to either overproduction or underproduction.
• Overproduction of Growth Hormone (GH): Results in gigantism.
• Overproduction of Adrenocorticotropic Hormone (ACTH): Leads to Cushing's disease.
• Underproduction of ACTH: Causes adrenal insufficiency.
• Tumours affecting Vasopressin Regulation: Can cause diabetes insipidus.
• Tumours impacting the Optic Chiasma: May cause bitemporal visual field loss (loss of peripheral vision in both eyes).
• Tumours affecting Sexual Development: Can lead to precocious puberty.
• Hypothalamic and Pituitary Tumours and Eating Disorders: May be associated with obesity and bulimia.

Cerebellum Location & Connections

• Located beneath the cerebral hemispheres and behind the brainstem.
• Connected to the brainstem via three pairs of cerebellar peduncles:
  • Inferior Cerebellar Peduncles: Connect the cerebellum to the medulla.
  • Middle Cerebellar Peduncles: Connect the cerebellum to the pons.
  • Superior Cerebellar Peduncles: Connect the cerebellum to the midbrain.

Cerebellum Function

• Plays a crucial role in coordinating and fine-tuning movements, ensuring they are smooth and precise. It doesn't initiate movement, but it refines it, making it accurate and controlled.
• Maintains equilibrium (balance), contributing to our ability to stand, walk, and move without falling.
• Regulates muscle tone, ensuring muscles have the right level of stiffness for efficient movement.
• Adjusts and maintains posture during movement, keeping us upright and balanced.

Cerebellum Clinical Significance

• Damage to the cerebellum can lead to ataxia (loss of coordination), causing difficulty with movement, balance, and gait.
• Ataxia is characterized by jerky, uncoordinated movements, problems with balance, and unsteady gait.

Cerebellar Lesions and Motor Deficits

• Midline lesions in the cerebellum often lead to loss of postural control and balance issues.

• Unilateral cerebellar hemispheric lesions cause ipsilateral (same-side) motor deficits.

• Intention tremors are tremors that occur during voluntary movements and are a common symptom of cerebellar dysfunction.

• Bilateral cerebellar dysfunction can cause dysarthria, which is slurred speech.

• Cerebellar ataxia is a condition that results from damage or degeneration of the cerebellum.

• Bilateral cerebellar dysfunction can be caused by various factors such as alcoholic intoxication, hypothyroidism, inherited cerebellar degeneration, and multiple sclerosis (MS).

• Nystagmus is a rapid, involuntary eye movement often associated with cerebellar disorders and MS.

• An unsteady gait affecting walking stability is a typical result of incoordination in the leg due to a unilateral cerebellar lesion.

Cerebral Hemispheres

• The largest part of the forebrain
• Covered by the cerebral cortex, a superficial layer of grey matter
• Ridges and furrows on the cerebral cortex are known as gyri (ridges) and sulci (furrows)
• Folding pattern allows for a greater number of neurons, enhancing cognitive processing
• White matter, composed of axons, lies beneath the grey matter
• White matter connects different parts of the brain, facilitating communication

Cerebral Cortex

• Responsible for complex functions, including:
  • Thought
  • Memory
  • Sensory perception
  • Voluntary movement
• Divided into four lobes:
  • Frontal
  • Parietal
  • Temporal
  • Occipital

Cerebral Cortex Structure

• The cerebral cortex is a thin layer of brain tissue, only a few millimeters thick, yet it is densely packed with neurons and has multiple functional layers.

Cerebral Cortex Function

• The cerebral cortex is responsible for processing and interpreting sensory information.
• It plays a crucial role in motor function, generating commands that initiate voluntary movements and planning motor actions.
• It is involved in conscious perception and detailed interpretation of sensory stimuli.
• It processes both sensory and motor information.

Cerebral Cortex and Sensory Information

• Sensory information primarily ascends to the cortex through the thalamus.

Cerebral Cortex and Motor Function

• The cerebral cortex is the highest level of motor system representation.
• It initiates and plans motor actions.
• It is not directly involved in controlling reflexes.

Cerebral Lobes and Functions

• Frontal Lobe: Responsible for executive functions such as thinking, planning, organizing, and problem-solving. It also houses the motor cortex.
• Parietal Lobe: Primarily associated with sensation, perception, and integrating sensory information. It contains the sensory cortex.
• Occipital Lobe: Responsible for processing visual information.
• Temporal Lobe: Associated with memory, understanding, language, and auditory processing.

Motor and Sensory Cortexes

• Motor Cortex: Located in the frontal lobe, it processes voluntary movement commands.
• Sensory Cortex: Located in the parietal lobe, it receives and processes sensory information from the body.

Medulla Oblongata

• Medulla Oblongata: Located in the brainstem, it is vital for controlling essential functions like breathing, heart rate, and respiration.

Frontal Lobe Lesions

• Can lead to different types of seizures: Simple focal, complex partial, or generalized seizures
• May result in both motor and sensory deficits
• Can cause changes in behavior, decision-making, and emotional control
• Particularly affect executive functions, such as planning and decision-making

Space-Occupying Focal Lesions

• Can be caused by a tumor
• Lead to raised intracranial pressure (ICP)
• Prolonged raised ICP can have severe consequences
• Symptoms of raised ICP include headaches, nausea, and vomiting

Seizures

• Simple focal seizure: Electrical activity starts and remains in a limited brain region