Neuroscience Chapter on Brain Structure

Nervous System Overview

• The nervous system is responsible for controlling the body's internal environment (homeostasis), experiencing and interpreting sensations, controlling voluntary movements and mediating automatic reactions, and perceptions, behaviors and memories.

Intended Learning Outcomes

• Describe the functions of the nervous system
• Describe the organization of the nervous system
• Identify major parts of the brain
• Describe the gross anatomical features of the spinal cord
• Describe protective structures of the brain and spinal cord

Functions of the Nervous System

• Controls the body's internal environment to maintain homeostasis
• Allows for the experience and interpretation of a range of sensations
• Controls all voluntary movements and mediates automatic reactions
• Is responsible for perceptions, behaviors, and memories

Nervous System Organization

• Nervous system is divided into central nervous system (CNS) and peripheral nervous system (PNS)
  • CNS: brain and spinal cord
  • PNS: includes:

    • autonomic nervous system - communicates with internal organs and glands

      • sympathetic division (arousing)
      • parasympathetic division (calming)

    • somatic nervous system - communicates with sense organs and voluntary muscles

    • sensory (afferent) nervous system - carries sensory input

    • motor (efferent) nervous system - carries motor output

Peripheral Nervous System (Somatic Nervous System)

• Somatic nervous system consists of somatic and special sense receptors
• Sensory neurons carry impulses from receptors to the CNS
• Motor neurons carry impulses from the CNS to skeletal muscles

Afferent Neurons—Sensory—

• Carry information from sensory receptors to the CNS (either cranial or spinal nerves)

Integrative Neurons—Interneurons—

• Integrate and analyze sensory information and decide on an action

Efferent Neurons—Motor—

• Carry information from the brain or spinal cord to muscles or glands (either cranial or spinal nerves)

Effectors (Muscles & Glands)

• Carry out the action initiated by the motor command

The Central Nervous System

• The human brain is the most complex organ in the body
• Contains approximately 86 billion neurons and 10-50 trillion neuroglia
• Each neuron typically forms about 1,000 synapses with other neurons

Major Parts of the Brain

• Cerebrum: includes the outer cerebral cortex, internal region of cerebral white matter, and basal ganglia
• Diencephalon (Thalamus): Located in the middle of the brain, beneath the cerebral cortex and above the midbrain, involved in sensory relay and other functions
• Brainstem (Midbrain, Pons, Medulla Oblongata): Continuous with the spinal cord, controlling vital functions
• Cerebellum: Found just below the cerebrum and behind the pons, involved in motor coordination and learning

Protective Structures (Meninges)

• Meninges are three layers covering the brain and spinal cord
  • Outermost: Dura Mater
  • Middle: Arachnoid
  • Innermost: Pia Mater

Ventricles

• Cavities within the brain filled with cerebrospinal fluid (CSF)
• Lateral ventricles project forward into hemispheres, the third ventricle lies between the right and left halves of the thalamus, and the fourth ventricle lies between the brainstem and the cerebellum

Clinical Application: Hydrocephalus

• Abnormal build-up of fluid in the ventricles
• In infants, blockage of cerebral aqueduct can cause widening of ventricles, putting pressure on brain tissues causing brain damage or death.

Spinal Cord

• Carries incoming and outgoing messages between the brain and the rest of the body
• Contains 100 million neurons and supporting neuroglia
• Extends from the brainstem to the second lumbar vertebra

Further Reading

• Tortora's principles of anatomy and physiology (Chapters 13 & 14)

Test your knowledge on brain structures and their functions with this quiz focused on the frontal, occipital lobes, and structural features of the brain. Understand the roles of gyri, sulci, and more as you assess your grasp of neuroscience concepts.