Neuroscience Quiz on RAS and Hydrocephalus

Nervous System Organization

• The nervous system comprises the central nervous system (CNS) and the peripheral nervous system (PNS)
• The CNS includes the brain and spinal cord, acting as the body's integrative control center.
• The PNS connects the CNS to the body, facilitating communication.

Divisions of the Nervous System

• Sensory (Afferent) Division: Composed of sensory neurons that transmit signals from receptors to the CNS.
• Motor (Efferent) Division: Composed of motor neurons that convey signals from the CNS to effectors (muscles and glands).
• Somatic Nervous System: Controls voluntary movement of skeletal muscles.
• Autonomic Nervous System: Controls involuntary responses like heart rate and digestion.
• Sympathetic Division: Mobilizes body systems for "fight or flight" responses.
• Parasympathetic Division: Conserves energy and promotes "rest and digest" activities.

Major Divisions of the Brain

• Forebrain: Includes the cerebrum and diencephalon.
• Diencephalon: Contains the thalamus, hypothalamus, epithalamus, and subthalamus.

Embryology of the Brain

• Neural Tube: The CNS initially develops as a neural tube.
• Neurocoel: The lumen of the neural tube is filled with fluid (neurocoel)
• Neural Plate: Ectodermal tissues differentiate into a neural plate.
• Embryonic development of the brain involves stages where prosencephalon, mesencephalon, and rhombencephalon differentiate into further components.
• Three primary brain vesicles: the prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain).
• Five secondary brain vesicles: The forebrain divides into telencephalon and diencephalon, the midbrain does not subdivide, and the hindbrain divides into metencephalon and myelencephalon.

Major Regions and Landmarks of the Brain

• Medulla oblongata, Pons, Cerebellum, Mesencephalon, Diencephalon, Cerebrum

Gross Cerebral Structure

• Gyri: Upward folds on the cerebral hemispheres.
• Sulci: Downward folds on the cerebral hemispheres.
• Convolutions: The collective name for gyri and sulci.
• Fissures: Deep grooves in the brain surface.

The Cerebral Hemispheres

• Lobes and Sulci: Frontal, parietal, occipital, and temporal lobes; central, lateral, and parieto-occipital sulci.
• Fissures and Sulci: Medial longitudinal, central (Rolando), lateral (Sylvius), parieto-occipital fissures/sulci.
• Lobes: Important functions in various areas such as cognition, language, and reception.

Cerebral Lobes

• Frontal Lobes: Responsible for cognition, expressive language, motor planning, etc.
  • Prefrontal Lobe: Mediates executive functions, self-insight, mood regulation, and working memory.
• Parietal Lobes: Sensory detection, perception, and interpretation.
• Temporal Lobes: Auditory processing, language comprehension, and long-term memory.
• Occipital Lobes: Visual stimuli interpretation.
• Insula: Lies deep in the lateral fissure and related to basic survival mechanisms (e.g., taste), visceral sensation, autonomic functions, emotional regulation (empathy, awareness, regulation).

Hemispheric Specialization

• Right Hemisphere: Analysis by touch, spatial visualization, controls movement on the left side of body, receives sensory input from left side.
• Left Hemisphere: Speech center, writing, language, mathematics, controls movement on the right side of body, receives sensory input from right side.

Split-Brain Humans

• Roger Sperry's Experiments: Investigated the function of cerebral hemispheres in humans with severed corpus callosum.
• Results: The left hemisphere handles language, but not the right hemisphere.
• Each hemisphere is responsible for movement and vision on the opposite side of the body.

The Wada Procedure

• Involves injecting an anesthetic into the carotid artery to temporarily disable one hemisphere.
• Used to determine which hemisphere is dominant for language.
• Used to help assess the location of language centers before surgical procedures.

Gray Matter vs. White Matter

• Gray matter: Part of the CNS, located in the cortex and the nuclei of the brain. Consists of nerve cell bodies; non-myelinated.
• White matter: Located beneath gray matter in the internal regions of cerebrum and cerebellum. Composed of myelinated fiber tracts; bundles of axons. -Association fibers: Connect different areas within a hemisphere. -Commissural fibers: Connect corresponding areas of the two hemispheres (e.g., corpus callosum). -Projection fibers: Connect the cerebrum with other parts of the brain and spinal cord.

Diencephalon

• Structures: Thalamus, Hypothalamus, Epithalamus, Subthalamus
• Functions: Sensory relay, homeostasis control, hormone regulation (Hypothalamus), circadian rhythm regulation and more.

Pituitary Gland

• Endocrine gland that secretes hormones for growth, reproduction, and regulation of metabolic processes.
• Anterior Pituitary: Secretes growth hormone, prolactin, LH, FSH, TSH, and ACTH.
• Posterior Pituitary: Secretes antidiuretic hormone (ADH) and oxytocin.
• Works in coordination with the hypothalamus.

Infundibulum

• The stalk that connects the hypothalamus to the pituitary gland.

Posterior and Anterior Commissures

• Posterior Commissure: Connects the right and left halves of the diencephalon, allowing communication between the hemispheres.
• Anterior Commissure: Connects olfactory bulb to amygdala and potentially plays a role in olfaction and communication between hemispheres

Structures Near Diencephalon (Not Part of It)

• Corpus Callosum: Largest commissure, connects the cerebral hemispheres.
• Optic Chiasm: Crossing-over point for optic nerves at the base of the brain.

Mammillary Bodies

• Nuclei in the hypothalamus that aid in processing memory.

Internal Capsule

• Large fiber bundle connecting the cerebral cortex to the diencephalon.
• Carries descending motor messages and ascending sensory information.

Basal Ganglia

• Structures involved in controlling movement, including arm and leg movements during walking.
• Composed of the caudate nucleus, putamen, and globus pallidus.
• Additional structures associated with basal ganglia include the subthalamic nucleus and the substantia nigra.

Limbic System

• Functions: Emotions, memory, links to autonomic functions.
• Structures: Cingulate gyrus, dentate gyrus, parahippocampal gyrus, hippocampus.

Hippocampus

• Structure within the parahippocampal gyrus.
• Plays roles in memory consolidation, particularly for emotionally significant memories.
• Associated with memory storage/retrieval.

Fornix

• Tract of white matter connecting the hippocampus and hypothalamus.

Brainstem

• Composed of midbrain, pons, and medulla oblongata.
• Controls vegetative functions like respiration, reflexes (cough, gag, pupillary), swallowing.

Medulla Oblongata

• Continuous with the spinal cord.
• Contains nuclei for cranial nerves VIII, IX, X, XI, and XII, including cardiovascular centers, respiratory centers.
• Is a relay for sensory and motor pathways, and autonomic control of visceral organs.

Pons

• Bulge superior to the medulla oblongata.
• Contains nuclei for cranial nerves V, VI, VII, and VIII.

Midbrain

• Also called the mesencephalon.
• Contains nuclei called corpora quadrigemina, involved in auditory and visual processing.
• Includes nuclei of the reticular formation, involved in alertness.

Reticular Formation

• Diffusely located in the brainstem.
• Screens and relays information to the cortex, amplifying important signals.
• Divided into Reticular Activating System (RAS) and Reticular Inhibiting System (RIS)
• RAS: involved in wakefulness and alertness
• RIS: involved in unconsciousness

Cerebellum

• Two hemispheres with folds (folia).
• Includes anterior, posterior, and flocculonodular lobes.
• Vermis separates hemispheres.
• Has a role in subconscious coordination of movement.

Ventricular System

• Four ventricles: Lateral ventricles (1 & 2), third ventricle, and fourth ventricle.
• Filled with cerebrospinal fluid (CSF).
• Ventricles are interconnected to circulate CSF throughout the brain and spinal cord.

Cranial Meninges

• Three layers: Dura mater, Arachnoid mater, and Pia mater.
• Dura Mater: Outermost layer, tough and thick membrane, has two layers.
• Arachnoid Mater: Middle layer, spider-web-like appearance, subarachnoid space.
• Pia Mater: Innermost layer attached to the surface of the brain.

Dural Sinuses

• Large veins above the frontal and parietal lobes.
• Act as a circulatory system for cerebral veins and CSF.

Cerebrospinal Fluid (CSF)

• Clear, colorless fluid that bathes the brain and spinal cord.
• Functions: Protection, support, nutrient transport, waste removal.

Formation of CSF

• Produced by choroid plexus in the ventricles.
• Ependymal cells are involved in actively transporting needed nutrients, vitamins, ions, and removing wasted material.

Choroid Plexus

• Vascular structures in the brain ventricles that produce CSF.

Arachnoid Villi

• Projections of the arachnoid mater into the dural sinuses.
• Reabsorb CSF into venous circulation.

Cerebrospinal Fluid Pressure

• CSF maintains a constant pressure, independent of production rate.
• A spinal tap can be used in diagnosing disease processes

Hydrocephalus

• Condition of abnormal accumulation of CSF in ventricles, leading to elevated pressure.
• Can be caused by blockage, excessive production, or impaired reabsorption.
• Diagnosis often leads to treatment by placing a shunt for draining excess fluid from ventricles.

Blood-Brain Barrier

• Tight junctions between endothelial cells lining the blood vessels in the brain.
• Only lipid-soluble materials can pass directly through into the brain; water-soluble substances require transport mechanisms.