BIOL 243L Lab 10 Study Guide

BIOL 243L Lab 10 Study Guide: Brain and Cranial Nerves

Meninges and Cranial Structures

Definition and Differences

  • Meninges: The protective membranes covering the brain and spinal cord, comprising three layers: dura mater, arachnoid mater, and pia mater.

  • Dural Venous Sinuses: Channels within the dura mater that collect venous blood from the brain and direct it into the internal jugular veins.

  • Dural Folds: Extensions of the dura mater that support and separate different parts of the brain.

    • Falx Cerebri: A sickle-shaped fold that divides the two cerebral hemispheres.

    • Falx Cerebelli: Separates the two cerebellar hemispheres.

    • Tentorium Cerebelli: A horizontal fold that separates the cerebrum from the cerebellum.

Layers of the Meninges

  • Dura Mater: The outermost layer, tough and protective.

  • Arachnoid Mater: The middle layer, resembling a spider web.

  • Pia Mater: The innermost layer, adheres closely to the brain's surface.

Spaces Associated with the Meninges

  • Epidural Space: Located between the dura mater and the skull.

  • Subdural Space: Between the dura mater and arachnoid mater; contains serous fluid.

  • Subarachnoid Space: Between the arachnoid mater and pia mater; contains cerebrospinal fluid (CSF).

Types and Symptoms of Hematomas

  • Epidural Hematoma: Accumulation of blood between the skull and dura mater; symptoms can include loss of consciousness, headache, nausea.

  • Subdural Hematoma: Bleeding between the dura mater and the arachnoid mater; may cause headaches, confusion, and changes in behavior or consciousness.

  • Subarachnoid Hematoma: Bleeding into the subarachnoid space; symptoms include sudden severe headache and potential symptoms of meningeal irritation.

Cerebrospinal Fluid (CSF)

Production and Pathway

  • Choroid Plexus: A network of cells in the ventricles of the brain responsible for producing CSF.

  • Pathway: CSF circulates from the lateral ventricles to the third ventricle through the interventricular foramen, then to the fourth ventricle via the cerebral aqueduct.

    • Reabsorption: Occurs in the arachnoid granulations into the venous system.

Blood Supply to the Brain

Circle of Willis

  • Circle of Willis: An anatomical ring of blood vessels at the base of the brain that provides collateral circulation between the anterior and posterior cerebral blood supplies.

  • Significance: Ensures continuous blood flow even if one of the major arteries is occluded.

Major Brain Regions

Overview

  • Prosencephalon (Forebrain): Divided into:

    • Telencephalon: Comprises the cerebral hemispheres responsible for higher brain functions.

    • Diencephalon: Contains the thalamus and hypothalamus, involved in sensory and autonomic functions.

  • Mesencephalon (Midbrain): Functions mainly in vision, hearing, motor control, sleep/wake, arousal, and temperature regulation.

  • Rhombencephalon (Hindbrain): Divided into:

    • Metencephalon: Contains the pons and cerebellum, involved in coordination and balance.

    • Myelencephalon: Corresponds to the medulla oblongata, responsible for autonomic functions like breathing and heart rate.

Lobes and Functions

  • Frontal Lobe: Associated with reasoning, planning, parts of speech, emotions, and problem-solving.

  • Parietal Lobe: Processes sensory information regarding the location of parts of the body.

  • Temporal Lobe: Involved in processing auditory information and memory.

  • Occipital Lobe: Primarily responsible for visual processing.

Surface Anatomy of the Brain

Key Features

  • Fissures: Deep grooves that separate major regions of the brain.

  • Sulci: Small grooves in the brain surface, dividing gyri.

  • Gyri: Elevated ridges of the cerebral cortex.

Central Sulcus

  • Central Sulcus: The prominent groove separating the frontal lobe from the parietal lobe.

    • Precentral Gyrus: Located anterior to the central sulcus, responsible for voluntary movement; primary motor cortex.

    • Postcentral Gyrus: Located posterior to the central sulcus, responsible for sensory perception; primary somatosensory cortex.

Diencephalon Structures

Key Components

  • Thalamus: Relay station for sensory and motor signals to the cerebral cortex, essential for consciousness and alertness.

  • Hypothalamus: Regulates autonomic functions, controls the endocrine system, and maintains homeostasis (e.g., temperature regulation, thirst).

  • Pineal Gland: Produces melatonin, which regulates sleep-wake cycles.

Brain Stem Structures

Pons and Medulla

  • Pons: Contains pathways that relay signals between the cerebellum and the cerebrum; involved in regulatory functions such as sleep and arousal.

  • Medulla Oblongata: Controls autonomic functions like heart rate, respiration, and blood pressure.

Corpora Quadrigemina

  • Structures: Four colliculi (two superior and two inferior).

    • Superior Colliculi: Involved in visual processing and eye movement control.

    • Inferior Colliculi: Involved in auditory processing.

Cerebellum

Function

  • Coordinates voluntary movements, balance, and posture. Helps refine motor performance.

Histology of Cortex

Cerebral and Cerebellar Cortex

  • Cerebral Cortex: The outer layer of the cerebrum, involved in higher functions like thought and action.

  • Cerebellar Cortex: The outer layer of the cerebellum, involved in processing sensory information for coordination.

Basal Nuclei (Basal Ganglia)

Function

  • Involved in regulating voluntary motor movements, procedural learning, routine behaviors, and emotion regulation.

Sheep Brain Dissection

Structures to Recognize

  • Names and functions of relevant structures in the sheep brain are crucial for understanding comparative anatomy and basic neuroanatomy.

Cranial Nerves

Recognition and Functions

  • Cranial Nerve Names and Numbers: Students must memorize the twelve cranial nerves, their Roman numeral designations, and basic functions.

Effects of Damage

  • Understanding the clinical implications of damage to specific cranial nerves is essential for diagnosing neurological conditions. Each nerve's function can be affected markedly upon injury or disease, leading to varied symptoms such as loss of sensation, motor dysfunction, and autonomic dysregulation.