Nervous System Overview

Nervous System

• The nervous system is divided into the central nervous system (CNS) and the peripheral nervous system.
• The CNS consists of the brain and spinal cord.
• The peripheral nervous system consists of the somatic component, and the autonomic component.

Central Nervous System (CNS)

• The CNS is protected by the skull and vertebral column, cerebrospinal fluid (CSF), and meninges.
• Meninges:
  • Dura mater
  • Arachnoid mater
  • Pia mater

Brain

• The brain is divided into the cerebrum, cerebellum, brainstem, and diencephalon.

Cerebrum

• The cerebrum is the largest part of the brain.
• It is divided into right and left hemispheres.

Cerebellum

• The cerebellum is located below the posterior portion of the cerebrum.
• It is formed of two cerebellar hemispheres, united by a median vermis.

Brainstem

• The brainstem consists of the midbrain, pons, and medulla oblongata.

Midbrain

• The midbrain extends between the diencephalon above and the pons below.
• It is the shortest part of the brainstem.
• It contains a narrow canal called the aqueduct of midbrain.

Pons

• The pons extends between the midbrain above and the medulla oblongata below.
• It lies in front of the cerebellum.

Medulla Oblongata

• The medulla oblongata is the lowest part of the brainstem.
• It is continuous with the pons above and the spinal cord below.
• It is responsible for regulating breathing, heartbeat, and blood pressure.

Diencephalon

• The diencephalon consists of the thalamus and hypothalamus.

Thalamus

• The thalamus is a mass of gray matter in the middle of the cerebrum.
• It is located on each side of the third ventricle.

Hypothalamus

• The hypothalamus is located below the thalamus and immediately above the pituitary gland.
• It forms the floor of the third ventricle.

Spinal Cord

• The spinal cord is located in the upper two-thirds of the vertebral canal.
• It is continuous with the medulla.
• It contains a narrow central canal called the central canal, containing CSF.
• The spinal cord is formed of outer white matter and inner gray matter (H-shaped).

Spinal Nerves

• There are 31 pairs of spinal nerves arising from the spinal cord.
• The distribution of spinal nerves:
  • 8 cranial pairs
  • 12 thoracic pairs
  • 5 lumbar pairs
  • 5 sacral pairs
  • 1 coccygeal pair
• Each nerve is formed by the union of a ventral root and a dorsal root.
• Each spinal nerve is further divided into a ventral (anterior) ramus and a dorsal (posterior) ramus.

Cranial Nerves

• There are 12 pairs of cranial nerves.
• Olfactory nerve (I): sense of smell
• Optic nerve (II): sense of vision
• Oculomotor nerve (III): motor to the eye
• Trochlear nerve (IV): motor to the eye
• Trigeminal nerve (V): sensory to eye, face, nasal cavity, mouth cavity, and motor to muscles of mastication.
• Abducent nerve (VI): motor to the eye.
• Facial nerve (VII): taste, motor for muscles of facial expression.
• Vestibulocochlear nerve (VIII): hearing, sense of balance.
• Glossopharyngeal nerve (IX): taste, sensory to pharynx and middle ear.
• Vagus nerve (X): taste, motor and sensory to larynx, pharynx, thoracic and abdominal organs.
• Accessory nerve (XI): motor to larynx, pharynx, the sternocleidomastoid muscle and trapezius muscle.
• Hypoglossal nerve (XII): motor to muscles of the tongue.

Autonomic Nervous System

• The autonomic nervous system consists of motor and sensory neurons supplying the viscera.
• It is classified into two main components: the sympathetic and parasympathetic nervous systems.

Sympathetic Nervous System

• The sympathetic nervous system originates from the thoracic and lumbar regions of the spinal cord.
• It prepares the body for urgent activity, such as "fight or flight."

Parasympathetic Nervous System

• The parasympathetic nervous system originates from some cranial nerves and from the sacral region of the spinal cord.
• It regulates the normal functions of the organs it supplies.

This quiz covers the structure and components of the nervous system, highlighting the central nervous system (CNS) and peripheral nervous system. Learn about the brain's divisions, including the cerebrum, cerebellum, and brainstem, as well as their protective features. Test your knowledge about the key elements of the nervous system.