BIOL5_Ch8_NervousSys_II (1)

Central Nervous System

• Chapter 8 Overview

  • Covers anatomy, organization, and functions of the brain and spinal cord.

Chapter 8 Outline

• Anatomy review (separate video)

• Structural organization of the brain

• Visualizing the brain and its functions

• Components:

  • Cerebrum

  • Diencephalon

  • Brainstem

  • Cerebellum

  • Spinal Cord Tracts

CNS: Structural Organization of the Brain

• Components: Consists of the brain and spinal cord.

• Functions:

  • Receives input from sensory neurons.

  • Directs activity of motor neurons.

  • Association neurons integrate sensory and motor activity enabling learning and memory.

• Divisions:

  • Midbrain

  • Diencephalon

Embryonic Development of the Brain

• Neural Tube:

  • Forms during early embryonic development.

• Primary Brain Vesicles (Week 4):

  • Prosencephalon (forebrain)

• Secondary Brain Vesicles (Week 5):

  • Development leads to mature structures such as

    • Telencephalon: cerebrum

    • Diencephalon: thalamus, hypothalamus

• Adult Structures:

  • Cerebrum:

    • Composed of cerebral hemispheres, cortex, white matter, basal nuclei

  • Diencephalon:

    • Includes thalamus, hypothalamus, epithalamus, and retina

  • Brainstem:

    • Composed of midbrain, pons, medulla oblongata

  • Cerebellum

• Central Canal and Ventricles:

  • Fluid-filled cavities within the brain.

Parts of the Brain

• Cerebrum:

  • Contains the lobes and cerebral cortex.

• Diencephalon:

  • Composed of epithalamus, thalamus, hypothalamus, pituitary gland, mammillary body.

• Brainstem:

  • Composed of midbrain, pons, medulla oblongata.

• Cerebellum

Composition of the CNS

• Gray Matter:

  • Composed of neuron bodies and dendrites.

• White Matter:

  • Composed of axon tracts (myelinated).

• Brain Weight:

  • Adult brain weighs approximately 1.5 kg.

  • Contains ~90 billion neurons.

  • Receives 20% of total blood flow to the body.

Cerebral Cortex

• Structure:

  • Highly convoluted with folds (gyri) and grooves (sulci).

• Lobes:

  • Each hemisphere includes five lobes: frontal, parietal, temporal, occipital, and insula.

Visualizing the Brain

• Brain Imaging Techniques:

  • MRI: High detail imaging (gray/white matter, CSF).

  • fMRI: Shows increased neural activity via blood flow.

  • CT: Visualizes soft tissues using radiation, faster than MRI.

  • PET: Examines brain metabolism and blood flow.

  • EEG: Measures electrical activity in the cerebral cortex.

Functional Specializations of the Brain

• Cerebral Nuclei:

  • Masses of cell bodies involved in movement control (indirect).

• Cerebral Lateralization:

  • Specialization of the left hemisphere for language and the right hemisphere for visuospatial tasks.

• Language Areas:

  • Broca’s area (speech production)

  • Wernicke’s area (language comprehension).

Hypothalamus

• Functions:

  • Regulates homeostasis, hunger, thirst, body temperature, emotions.

  • Controls endocrine functions via hormone release.

  • Coordinates autonomic nervous system activities (sympathetic and parasympathetic).

Brain Stem and Cerebellum

• Brain Stem:

  • Connects brain to spinal cord, contains cranial nerve nuclei, and centers vital for breathing and cardiovascular regulation.

  • Medulla Oblongata: Essential for respiration, cardiac control, and rhythmicity of breathing.

• Cerebellum:

  • Contains ~69 billion neurons; coordinates movements and balance.

Spinal Cord Tracts

• Sensory Pathways:

  • Ascending tracts relay sensory information to the brain.

• Motor Pathways:

  • Descending tracts carry motor commands from the brain to the body.