NERVOUS SYSTEM

The Nervous System

• The nervous system is the body's control center and communication network, responsible for coordination of movement, response to environmental stimuli, intelligence, self-awareness, thought, and emotion.

Central Nervous System

• Composed of the brain and spinal cord, which acts as the body's control center and coordinates the body's activities.
• The brain contains parts that function in the coordination of movement, sensing, and consciousness, as well as areas that are below the level of conscious control.
• The brain is protected by the cranial bones, cranial meninges, and cerebrospinal fluid, which acts as a shock absorber and circulates nutrients.
• The brainstem is divided into three main parts: diencephalon, pons, and medulla oblongata.

Peripheral Nervous System

• Divided into two main parts: Somatic Nervous System and Autonomic Nervous System.
• Somatic Nervous System carries motor information and sensory information between the skin, sensory organs, and skeletal muscles to the central nervous system.
• Autonomic Nervous System relays information from the central nervous system to organs and is involuntary.
• Autonomic Nervous System is further divided into Sympathetic Nervous System (controls in times of stress) and Parasympathetic Nervous System (controls the body in times of rest).

Neurons

• A nerve cell is the basic unit of the nervous system, and there are billions of neurons in the body.
• Neurons are specialized for information processing and signaling, relaying and receiving messages between the brain and the body.

Brain Lobes

• The four lobes of the brain are:
  • Occipital lobe: manages vision
  • Temporal lobe: manages hearing and speech
  • (Two lobes not specified in the text)

Spinal Cord

• Acts as the nervous system's "superhighway", containing a central canal filled with cerebrospinal fluid.
• Composed of gray matter (inner layer) containing cell bodies of neurons and short fibers, and white matter (outer layer) containing long fibers of interneurons.

Spinal Nerves

• 31 pairs of spinal nerves emerge from the spinal cord, divided into:
  • Cervical: 8 pairs
  • Thoracic: 12 pairs
  • Lumbar: 5 pairs
  • Sacral: 5 pairs
  • Coccygeal: 1 pair

Reflex and Reflex Arc

• A reflex is an involuntary reaction to an external stimulus, and a reflex arc is the pathway that causes a reflex.