Module 3 - Lecture 1

Central Nervous System Anatomy: The Brain

Overview of the Nervous System

• Central Nervous System (CNS)

  • Brain and spinal cord.

• Peripheral Nervous System (PNS)

  • Comprised of cranial nerves and spinal nerves.

  • Afferent Division: Carries information towards the CNS.

  • Efferent Division: Carries information out of the CNS.

• Enteric Nervous System: Involved in digestion.

The Brain

• Most complex organ in the human body.

• Largest brain in humans relative to body weight compared to other mammals.

• Contains approximately 100 billion neurons.

Neurons (Brain Cells)

• Basic functional unit of the nervous system.

• Function by transmitting electrical signals.

• Components:

  • Cell body

  • Dendrites

  • Axon (surrounded by myelin, a fatty substance)

Lobes, Sulci, and Fissures of the Cerebral Hemispheres

• Cerebral hemispheres form the superior part of the brain, accounting for 83% of brain mass.

• Surface Markings:

  • Gyri: Ridges on the surface of the brain.

  • Sulci: Shallow grooves between gyri.

  • Fissures: Deep grooves.

    • Longitudinal Fissure: Separates the two hemispheres.

    • Central Sulcus: Separates the frontal lobe from the parietal lobe.

Lobes of the Cerebral Cortex

• Several sulci divide each hemisphere into four main lobes:

  • Frontal

  • Parietal

  • Temporal

  • Occipital

• Transverse Cerebral Fissure: Separates the cerebral cortex from the cerebellum.

• Insula (Insular Lobe): A lobe located deep within the lateral sulcus.

Major Parts of the Brain

1. Cerebrum

   • Cerebral Cortex

   • Subcortical Regions

2. Diencephalon

   • Thalamus

   • Hypothalamus

   • Pineal Gland

3. Brainstem

   • Midbrain

   • Pons

   • Medulla

4. Cerebellum

Cerebrum - Cerebral Cortex

• Functional Areas:

  • Frontal Lobe

    • Prefrontal Cortex: Higher thought functions.

    • Motor Cortex: Control of movement.

  • Parietal Lobe: Sensory perception.

  • Temporal Lobe: Hearing.

  • Occipital Lobe: Visual perception.

  • Primary Sensory Areas: Receive sensory information.

  • Association Areas: Integrate information.

Sensory and Motor Cortex - Homunculi

• Homunculus: "Little man"

• Neurons map out body regions in the sensory and motor cortex.

• Larger body areas on the homunculus indicate greater:

  • Control (motor cortex)

  • Sensitivity (sensory cortex)

Grey & White Matter

• Coronal Section of the Brain:

  • Outer layer = Cortex (grey matter)

  • Inner grey matter = Subcortical structures

  • Collections of cell bodies = Nuclei

White Matter Tracts

• Commissural Fibers: Connect grey matter of the two hemispheres.

  • Corpus Callosum

• Projection Fibers: Connect hemispheres with lower regions of the brain or spinal cord.

  • Internal Capsule

• Association Fibers: Connect areas within the same hemisphere.

Cerebrum - Subcortical Structures (Basal Ganglia/Nuclei)

• Caudate Nucleus

• Putamen

• Striatum: Caudate + Putamen

• Globus Pallidus: Control muscle movements; malfunction in Parkinson’s disease.

Diencephalon

• Thalamus: Relay station and integrating center.

• Hypothalamus: Control of homeostasis, center for behavioral drives (e.g., hunger, thirst, reproduction), influences autonomic and endocrine function.

• Endocrine Structures:

  • Pituitary Gland: Secretes hormones.

  • Pineal Gland: Secretes melatonin.

Brainstem

• Oldest part of the brain.

• Controls basic life systems.

• Contains pathways carrying sensory and motor information.

• Components:

  • Medulla Oblongata: Controls involuntary functions (e.g., respiration, blood pressure, heart rate, swallowing, vomiting).

  • Pons: Relay station, coordinates control of breathing.

  • Midbrain: Controls eye movement, relay signals for hearing and seeing reflexes.

Cerebellum

• Second largest structure of the brain.

• Folds called folia.

• Hemispheres connected by the vermis.

• Connects to the brainstem via peduncles.

• Processes sensory information and coordinates the execution of precise movements.