Lecture 02 - BIOL2230

Lecture Overview

Course: Anatomy of the Brain and Spinal CordInstructor: Kevin Danastas, Macquarie University (BIOL2230 Neurophysiology)Disclaimer: Material is for individual research and study only. Sharing without permission is prohibited.Recommended Reading Text: Stanfield (2017), Principles of Human Physiology, 6th Edition, Pearson.Chapters: 9.2 – 9.3

Anatomical Planes

• Sagittal Plane: Divides the body into left and right halves.

• Transverse Plane: Divides the body into upper (superior) and lower (inferior) parts.

• Coronal Plane: Divides the body into front (anterior) and back (posterior) sections.

Anatomical Terminology

• Directional Terms:

  • Anterior: Front side

  • Posterior: Back side

  • Superior: Above or higher than

  • Inferior: Below or lower than

  • Medial: Toward the midline

  • Lateral: Away from the midline

  • Ventral: Belly side

  • Dorsal: Back side

  • Ipsilateral: Same side

  • Contralateral: Opposite side

Learning Objectives

• Major anatomical features and functional organization of the spinal cord and nerves.

• Anatomical regions of cerebral hemispheres and organizational structure of the cortex.

• Anatomical structure and function of the hypothalamus, thalamus, epithalamus, and limbic system.

• Anatomy and functional organization of the cerebellum.

• Anatomy and functional organization of the brainstem and cranial nerves activities.

Spinal Cord Overview

• Connection: Links the Central Nervous System (CNS) to the Peripheral Nervous System (PNS).

• Length and Width: Approximately 40-50 cm long; 2 cm wide at mid-thoracic.

• Location: Extends from the medulla oblongata to the L1/L2 intervertebral disc, tapering to the conus medullaris.

• Cauda Equina: Bundle of nerves continuing down the vertebral column.

Structure of the Spinal Cord

• Gray and White Matter: Opposite arrangement compared to the brain—white matter outside and gray matter inside.

• Dorsal Horns: Sensory functions.

• Ventral Horns: Motor functions.

• Orientation: Identified through the ventral fissure.

Spinal Nerves

• Segments: 31 neural segments resulting in 31 pairs of spinal nerves:

  • 8 Cervical

  • 12 Thoracic

  • 5 Lumbar

  • 5 Sacral

  • 1 Coccygeal

• Emergence: Spinal nerves exit through openings between adjacent vertebrae.

Fascicles in Spinal Nerves

• Composition: Bundles of axons known as fascicles, held together by layers of connective tissue.

• Myelination: Staining reveals myelinated and unmyelinated axons within a fascicle.

Spinal Nerve Structure

• Formed by Dorsal (Posterior) Root: Afferent (sensory) fibers (Receptor → PNS → CNS).

• Ventral (Anterior) Root: Efferent (motor) fibers (CNS → PNS → Effector).

Forebrain Anatomy

• Components: Diencephalon and Telencephalon.

  Major Areas:

  • Cerebral Hemispheres: Responsible for complex functions such as thoughts, emotions, memories, and sensory-motor processing.

    • Lobes of the Cerebrum:

      • Frontal Lobe: Involved in decision making, problem solving, and controlling behavior and emotions. Houses the primary motor cortex, responsible for voluntary muscle movement.

      • Parietal Lobe: Processes sensory information related to touch, temperature, and pain. Contains the primary somatosensory cortex, which receives tactile information from the body.

      • Temporal Lobe: Important for auditory processing, memory, and language comprehension. Contains the hippocampus and auditory cortex.

      • Occipital Lobe: Primarily responsible for visual processing. Contains the primary visual cortex, which interprets visual information from the eyes.

    • Deep Structures: Basal ganglia (caudate nucleus, putamen) and limbic structures (hippocampus, amygdala).

Cerebral Cortex Features

• Organization: Divided into gyri (ridges) and sulci (grooves).

• Function: Processes sensory and motor information while controlling voluntary and involuntary functions.

• Lateralization: Determines that some functions are predominantly localized to one hemisphere.

Neuronal Organization in the Cortex

• Types of Neurons:

  • Pyramidal Neurons: Main output cells with large dendritic trees.

  • Stellate (Granular) Neurons: Shorter axons, primarily interneurons.

• Layer Distribution: Different areas of the cortex have varying distributions of pyramidal and stellate neurons, affecting their functionality.

Basal Nuclei Function

• Components: Include structures like the globus pallidus and caudate.

• Functions: Influence emotions, memory, and motor control.

White Matter Tracts

• Commissural Fibers: Connects left and right hemispheres (e.g., corpus callosum).

• Association Fibers: Connect areas within the same hemisphere.

• Projection Fibers: Ascending and descending tracts for communication to/from the cortex.

Brainstem Overview

• Components: Midbrain, Pons, Medulla oblongata.

• Functions: Regulates vital processes such as breathing, heart rate, and consciousness.

Cranial Nerves Functions

• 12 cranial nerves provide sensory and motor function to the head and neck.

• Key Nerves: Include olfactory, optic, oculomotor, and several mixed-class nerves serving varied functions.

Summary of CNS Structure

• Central Nervous System (CNS) Division: Includes the forebrain, midbrain, hindbrain, and spinal cord.