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