Anatomy of the Nervous System

Anatomy of the Nervous System

• The nervous system is divided anatomically into the central nervous system (CNS) and the peripheral nervous system (PNS).
• The CNS comprises the brain and spinal cord.
• The brain is protected by the skull and the spinal cord by the vertebral column.
• The meninges (dura mater, arachnoid matter, and pia mater) cover the brain and spinal cord.
• Cerebrospinal fluid (CSF) is present within the ventricles of the brain and the central canal of the spinal cord.

CNS Components

• Brain: Consists of:
  • Cerebrum (forebrain): Largest part, responsible for higher-level functions. Divided into right and left hemispheres by the longitudinal fissure. Each hemisphere has three surfaces; superolateral, medial, and inferior; Contains lobes (frontal, parietal, temporal, and occipital).
  • Brain stem: Located between cerebrum and spinal cord. Includes midbrain, pons, and medulla oblongata. Acts as a pathway for tracts (neural pathways) between different areas of the brain and spinal cord. Serves as a control centre for various visceral functions (e.g., heart rate, blood pressure, respiration) Includes cranial nerve nuclei.
  • Cerebellum: Located beneath the occipital lobes, plays a crucial role in balance and integration of muscle tone, responsible for motor coordination. It is separate from the brainstem, and is behind the brainstem.

CNS Subdivisions (Brain Stem)

• Midbrain: Located beneath the diencephalon, includes a cerebral aqueduct.
• Pons: Located between midbrain & medulla oblongata
• Medulla Oblongata: Located at the base of the brain.

Spinal Cord

• It's a slender column of nerve fibers.
• It extends from the brainstem through the vertebral canal.
• It's continuous with the medulla oblongata.
• It gives off 31 pairs of spinal nerves and is segmented (8 cervical, 2 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal).
• It is divided into sections with (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal).
• It contains (gray matter, white matter) and a number of meninges.
• It contains central gray matter and peripheral white matter.
• The spinal cord extends from the base of the brain through the vertebral column.
• It terminates near the intervertebral disk between the first and second lumbar vertebrae (L1/2).

PNS Components

• Spinal Nerves: These emerge from the spinal cord and exit through intervertebral foramina.
  • Each spinal nerve has dorsal and ventral roots, which unite to form the spinal nerve proper.
  • Dorsal (posterior) roots contain sensory neurons, while ventral (anterior) roots carry motor neurons.
  • 31 pairs of spinal nerves.
• Cranial Nerves: 12 pairs of nerves that emerge from the brain and enter/exit from the skull.
  • Cranial nerves exhibit different functions (some sensory, some motor, or mixed).

Peripheral Nervous System (PNS) Subdivisions

• Somatic nervous system: Innervates skeletal muscles (voluntary control) and skin (sensory).
• Autonomic nervous system: Controls visceral functions (involuntary control). Divided into sympathetic and parasympathetic divisions.
  • Sympathetic Division: Originates from the thoracolumbar region (thoracolumbar outflow). Involved in "fight-or-flight" responses.
  • Parasympathetic Division: Originates from cranial regions and the sacral segments (craniosacral outflow). Active during "rest-and-digest" activities.

Cranial Nerves

• 12 pairs of nerves, numbered I-XII.
• Attached to the ventral surface of the brain.
• Exit the brain through foramina within the skull.
• I & II attach to forebrain.
• III-XII attach to the brainstem.
• Each cranial nerve has different functions. (e.g., sensory, motor).

Nerve Fiber Organization

• Nerves: Bundles of axons in the peripheral nervous system (PNS).
• Tracts: Bundles of axons in the central nervous system (CNS).
• Ganglia: Clusters of neuron cell bodies in the PNS.
• Nuclei: Clusters of neuron cell bodies in the CNS.

This quiz covers the anatomy of the nervous system, focusing on the central (CNS) and peripheral nervous systems (PNS). You'll learn about the components of the CNS, including the brain and spinal cord, as well as the protective structures surrounding them. Prepare to test your knowledge on the brain's divisions and functions.