Chapter 13: Anatomy of the Nervous System

Anatomy of the Nervous System

Overview of the Brain

• Cerebrum: Largest part of the brain, making up the majority of its mass.

• Longitudinal Fissure: Separates the cerebrum into right and left hemispheres.

Structures of the Cerebrum

• Corpus Callosum: Deep within the cerebrum, A band of nerve fibers connects the two hemispheres, facilitating communication.

• Cerebral Cortex: The outer layer of gray matter on the cerebrum that appears wrinkled.

Brain Surface Features

*Gyri (Singular: Gyrus): Elevated ridges on the brain's surface.

• Sulci (Singular: Sulcus): Grooves between the gyri, which define the boundaries of different regions.

Lobes of the Cerebral Cortex

• Frontal Lobe: Responsible for motor functions and higher cognitive processes like personality and short-term memory.

• Precentral Gyrus: Primary motor cortex that controls voluntary motor functions.

• Parietal Lobe: Involved in somatosensation—processing sensations like touch, pressure, pain, and body position.

• Postcentral Gyrus: Primary somatosensory cortex for integrating sensory information.

• Temporal Lobe: Related to auditory processing and memory functions due to its proximity to the limbic system.6

• Occipital Lobe: Primarily responsible for processing visual information; works closely with parietal and temporal lobes.

Subcortical Structures

• Basal Nuclei: Group of nuclei responsible for movement planning and cognitive processing.

• Basal Forebrain: Involved in acetylcholine production and key areas like the hippocampus and amygdala (memory and emotion).

• Limbic Cortex: Part of the limbic system involved in emotion and behavior.

Diencephalon

• Thalamus: Relays sensory information (except smell) to the cortex; integrates incoming and outgoing messages.

• Hypothalamus: Regulates homeostasis, autonomic functions, and the endocrine system.

Brainstem and Cerebellum

• Brainstem: Composed of the midbrain, pons, and medulla oblongata, connecting the brain to the spinal cord.

• Midbrain: Coordinates sensory perceptions (visual, auditory, somatosensory).

• Pons: Connects the cerebellum and plays a role in regulating breathing and sleep.

• Medulla Oblongata: Regulates cardiovascular and respiratory functions.

• Cerebellum: Integrates movement and sensory feedback; coordinates balance and motor control.

• Arbor Vitae: The white matter within the cerebellum, resembling a tree structure.

Spinal Cord Anatomy

• Divided into four regions matching the vertebral column: cervical, thoracic, lumbar, and sacral.

• Ends in the cauda equina—a bundle of nerves, rather than extending the full length of the vertebral column.

• Gray Matter: Forms horns (anterior, posterior, lateral) in the spinal cord for processing different types of information (sensory and motor).

• White Matter: Organized into columns responsible for ascending sensory and descending motor pathways.

Meninges and Cerebrospinal Fluid (CSF)

• Meninges: Protective membranes consisting of three layers:

• Dura Mater: Tough, fibrous outer layer.

• Arachnoid Mater: Middle layer, web-like protective layer.

• Pia Mater: Thin, delicate inner layer that adheres to the brain's surface.

• Cerebrospinal Fluid (CSF): Circulates within the ventricles to cushion the brain, remove waste, and maintain homeostasis.

• Produced by the choroid plexus; flows between the ventricles and into the subarachnoid space.

Peripheral Nervous System (PNS)

• Composed of ganglia (clusters of nerve cell bodies) and nerves (bundles of axons).

• Cranial Nerves: 12 pairs responsible for sensory and motor functions in the head and neck.

• Examples include:

  • Olfactory Nerve: Sense of smell (sensory).

  • Optic Nerve: Vision (sensory).

  • Vagus Nerve: Autonomic functions of thoracic and abdominal organs (sensory and motor).

• Spinal Nerves: 31 pairs that are combined sensory and motor nerves branching from the spinal cord, organized into nerve plexuses (cervical, brachial, lumbar, sacral).