ByNoor Mariammustafa Chapter 13: Nervous System (Part 2)

The Brain

• The cerebrum is the largest portion of the human brain, divided into left and right cerebral hemispheres by the longitudinal fissure.
• The cerebral cortex, a highly convoluted outer layer, covers the cerebral hemispheres and is responsible for sensation, voluntary movement, and thought processes.
• The white matter, the inner part of the cerebrum, consists of long myelinated axons organized into tracts.
• The two hemispheres are connected by the corpus callosum.

Lobes of Cerebral Hemisphere

• The lobes of the cerebral hemisphere include:
  • Frontal lobe
  • Parietal lobe
  • Temporal lobe
  • Occipital lobe

Basal Nuclei

• Basal nuclei integrate motor commands to ensure proper muscle stimulation or inhibition.
• Composed of hippocampus (crucial role in learning and memory) and amygdala (emotional overtones to experiences).

Limbic System

• Involved in emotions, learning, and memory.
• Crucial role in learning and memory.

Higher Mental Functions

Memory and Learning

• Memory: ability to hold a thought in mind or recall events from the past.
• Learning: retaining and utilizing past memories.
• Types of memory:
  • Short-term vs. long-term
  • Semantic memory (numbers, words, etc.)
  • Episodic memory (persons, events, etc.)
  • Skill memory (motor activities, initially conscious while learning, automatic once learned)

Language and Speech

• Depends on semantic memory and motor centers in the occipital and temporal lobes.
• Wernicke's area: ability to comprehend speech.
• Broca's area: ability to speak and write.

The Brain (continued)

• Diencephalon: made up of hypothalamus and thalamus, integrates center for maintaining homeostasis.
• Cerebellum: second-largest part, involved in muscle coordination, tone, and maintaining posture/balance.
• Brain stem: contains midbrain, pons, and medulla oblongata, connects cerebrum with other brain parts, regulates breathing and heartbeat.

Reticular Activating System (RAS)

• Reticular formation: complex network of nuclei and fibers extending the length of the brain stem.
• Involves the thalamus, serving as a central relay station for sensory impulses (except smell).
• Acts as a "gatekeeper" to the cerebrum, arouses the cerebrum via the thalamus, and causes a person to be alert.