Brain: Anatomy, Function, and Protection

Introduction to Physiology and Function of the Brain

  • Instructor Information

    • Assoc. Prof. Hugh Senior

    • Massey University, School of Health Sciences

    • Contact: (+649) 2136030, h.senior@massey.ac.nz

Learning Objectives

  • Discuss roles of glial cells in the central nervous system

  • Describe brain structure, development, and protection mechanisms

  • Explain location and function of different brain parts

  • Detail production, reabsorption, flow, and function of cerebrospinal fluid (CSF)

Central and Peripheral Nervous Systems (NS)

  • Central Nervous System (CNS)

    • Composed of brain and spinal cord

    • Contains neurons and support cells within skull and vertebral column

    • Processes sensory information for motor response

  • Peripheral Nervous System (PNS)

    • All neural structures outside the brain and spinal cord

    • Afferent: sensory receptors to CNS

    • Efferent: CNS to skeletal muscles or glands

    • Links CNS with external environment

Organization of the Nervous System

  • CNS

    • Structure: Brain and spinal cord

    • Function: Control centers

  • PNS

    • Communication lines between CNS and body

    • Sensory Division: Afferent nerve fibers to CNS

    • Motor Division: Efferent nerve fibers from CNS

    • Somatic (voluntary) and autonomic (involuntary) divisions

      • Sympathetic: Activates body systems in activity

      • Parasympathetic: Conserves energy, promotes rest

Tissues of the Nervous System

  • Neurons: Main communication cells

  • Neuroglia (Glial Cells): Supporting cells

    • Protect neurons and provide metabolic support

    • Not electrically active, can divide (unlike neurons)

Types of Support Cells in CNS and PNS

  • CNS Neuroglia:

    • Oligodendrocytes (myelinate axons)

    • Astrocytes (support and anchor neurons)

    • Microglial cells (immune defense)

    • Ependymal cells (line ventricles)

  • PNS Neuroglia:

    • Schwann cells (myelinate peripheral axons)

    • Satellite cells (support neurons in ganglia)

Structure of the Brain

  • Composed of wrinkled tissue, includes

    • Cerebral hemispheres

    • Cerebellum

    • Brain stem

  • Weight: ~1.6 kg (2% of body weight)

  • Receives ~20% of cardiac output

Brain Regions

  1. Cerebral Hemispheres

  2. Diencephalon (Thalamus, Hypothalamus)

  3. Brain Stem (Midbrain, Pons, Medulla)

  4. Cerebellum

Anatomical Terms

  • Gyri: Elevated ridges

  • Sulci: Grooves between gyri

  • Fissures: Deep grooves separating large brain regions

Cerebral Hemispheres

  • External gray matter (cortex)

  • Internal white matter (myelinated axons)

  • Divided into lobes: Frontal, Parietal, Occipital, Temporal, and Insula

  • Each hemisphere controls opposite side of the body (contralateral)

Functional Areas of the Cerebral Cortex

  • Motor Areas: Control voluntary movement

  • Sensory Areas: Awareness of sensation

  • Association Areas: Integrate information for meaning

Lobes of the Cerebral Cortex Functions

  1. Frontal Lobe

    • Executive functions, motor control, speech (Broca's area)

  2. Parietal Lobe

    • Sensory processing, spatial recognition

  3. Occipital Lobe

    • Visual processing (primary and visual association areas)

  4. Temporal Lobe

    • Auditory processing, language comprehension (Wernicke's area)

  5. Insula

    • Gustatory sensations

Internal Connection of the Brain

  • White Matter: Contains three types of fibers:

    1. Association Fibers: Connect different areas within the same hemisphere

    2. Commissural Fibers: Connect corresponding areas of both hemispheres (e.g., corpus callosum)

    3. Projection Fibers: Connect lower brain regions to the cortex

Basal Nuclei (Ganglia)

  • Subcortical regions influencing muscle movement

  • Involved in motor control and cognitive functions

  • Includes caudate nucleus, putamen, globus pallidus

Diencephalon Structures

  • Thalamus: Relay station for sensory and motor signals

  • Hypothalamus: Key homeostatic center

    • Controls autonomic functions (e.g., temperature, hunger)

  • Epithalamus: Includes pineal gland (melatonin secretion) and choroid plexus (produces CSF)

Brain Stem

  • Composed of midbrain, pons, and medulla oblongata

    • Mediates survival functions

    • Contains nuclei for most cranial nerves

Cerebellum Functions

  • Coordination of movement, balance, and motor learning

  • Compares intended movement with actual movement and adjusts accordingly

The Limbic System

  • Composed of structures involved in emotion and memory

  • Key areas include the hippocampus and amygdala

Reticular Formation

  • Network of neurons in brain stem

  • Controls wakefulness and filters sensory information for attention

Cerebrospinal Fluid (CSF)

  • Protective fluid surrounding brain and spinal cord

  • Production: 500 mL/day (replaced every 8 hours)

  • Functions: Cushioning, nutrient transport, waste removal

Blood-Brain Barrier

  • Protects brain's environment

  • Selectively allows substances to enter; important for maintaining homeostasis