Nervous System Overview by Dr. Mennat Allah Saqr

Lecture Overview

• The lecture is on the nervous system, specifically the central and peripheral nervous systems
• The lecturer is Dr. Mennat Allah Saqr, specializing in Anatomy and Embryology at Alexandria University
• The objectives of the lecture include classifying the nervous system and relating brain parts to their functions, differentiating between spinal and cranial nerves, and relating the divisions of the autonomic nervous system to their origins

Central Nervous System (CNS)

• The CNS consists of the brain and spinal cord
• The brain occupies the cranial cavity
• The brain's structure includes the cerebrum (with two cerebral hemispheres), the brain stem, and the cerebellum
• The spinal cord occupies the upper two-thirds of the vertebral canal
• The brain is covered by three membranes (meninges): dura mater, arachnoid mater, and pia mater

Brain

• Lies inside the skull (cranial cavity)
• Coverings include the dura mater, arachnoid mater, and pia mater
• The brain is composed of different parts, including the cerebrum, cerebellum, and brain stem
• Cerebrum: Contains four lobes (frontal, parietal, temporal, and occipital)
• Frontal Lobe: Involved in motor function
• Parietal Lobe: Involved in sensory function
• Temporal Lobe: Involved in hearing, smell, and taste
• Occipital Lobe: Involved in vision
• The lobes are separated by sulci and gyri

Cerebellum

• Located beneath the posterior part of the cerebral hemispheres (occipital lobe)
• Functions include regulation of muscle tone, equilibrium, and coordination of movements

Brain Stem

• Located at the base of the brain, extending downwards into the spinal cord
• Composed of midbrain, pons, and medulla oblongata
• Contains centers for respiration, cardiovascular control and nuclei for cranial nerves

Spinal Cord

• Situated within the vertebral canal
• Extends from the foramen magnum (the lower end of the medulla oblongata), to the second lumbar vertebra (L2)
• Responsible for transmitting peripheral and autonomic nerves
• Plays a role in reflex arcs

Peripheral Nervous System (PNS)

• The PNS consists of cranial nerves and spinal nerves and the autonomic nervous system
• Somatic nervous system:
  • Cranial nerves (12 pairs): Supply the head and neck
  • Spinal nerves (31 pairs): Supply the neck, thorax, abdomen, pelvis, and lower limbs (cervical, thoracic, lumbar, sacral, coccygeal)
• Autonomic nervous system:
  • Sympathetic division: Originates in the thoracolumbar region; "fight or flight" response
  • Parasympathetic division: Originates in the craniosacral region; "rest and digest"

Reflex Arc

• A neural pathway responsible for involuntary responses to stimuli

• Involves afferent (sensory) and efferent (motor) neurons connected by the spinal cord

• The process of a reflex arc is demonstrated with an example of how a person reacts to a hot object