Gross Anatomy and CNS Organization; Neuroimaging Techniques

March 31, 2011

BASICS OF THE CENTRAL NERVOUS SYSTEM

Coronal Slice Sagittal Slice Horizontal Slice

Frontal View Medial View Dorsal View

MRI of patient with 16p11.2 Dup

MRI of patient with 16p11.2 Dup

• 14:1 male• Previous diagnoses: Intellectual Disability,

PDD-NOS, ADHD-Combined Type, Disruptive Behavior Disorder-NOS, Cognitive Disorder NOS.

• Current diagnoses: Mild Intellectual Disability, Vocal Tic Disorder, ADHD and Disruptive Behavior Disorder-NOS.

Neurons and Glia

Neurons and Glia

• Glial cells– Ependymal– Astrocyte– Microglial– Oligodendroglial– Schwann

Gray, White, and Reticular Matter

Gray MatterColor from capillary blood vessels and neuronal cell bodies

White MatterColor from axons covered in an insulating layer of glial cells

Reticular MatterColor and appearance from cell bodies and axons

Layers, Nuclei, Nerves, and Tracts

• Layers or Nuclei– Well-defined group of cell

bodies (e.g. thalamus)• Tract

– Large collection of axons projecting to or away from a layer or nucleus within the CNS (e.g. optic tract)

• Nerves– Fibers and fiber pathways

that enter and leave the CNS (e.g. auditory nerve)

REGIONS & STRUCTURES OF THE CENTRAL NERVOUS SYSTEM

The Central Nervous System

Ventricles

The Spinal Cord

• Spinal Cord Structure and the Spinal Nerves– Receives fibers from afferent sensory

receptors– Sends efferent fibers to control muscles– 30 spinal cord segments divided into five

regions• Cervical (8)• Thoracic (12)• Lumbar (5)

• Sacral (5)• Coccygeal Segment

• Dorsal Root: Strand of afferent fibers entering the spinal cord; Carries sensory information to the brain

• Ventral Root: Strand of efferent fibers leaving the spinal cord; Carries motor information to the body• Reflexes occur at the level of the spinal cord

Connections Between Central and Somatic Nervous System

• Cranial Nerves– 12 pairs, overseen by

the brain– Can have afferent

functions, efferent functions, or both

The Central Nervous System

The Brainstem

Hindbrain

Midbrain

Diencephalon• Hypothalamus

– Interacts with the pituitary gland– Participates in nearly all aspects of motivated behavior

• Thalamus– Relays sensory information to appropriate targets– Relays information between cortical areas– Relays information between forebrain and brainstem

Forebrain

• Three main structures– Basal Ganglia– Limbic System– Cerebral Cortex

Subcortical

Forebrain

• Basal Ganglia– Collection of nuclei that includes the:

• Putamen• Globus Pallidus• Caudate Nucleus

– Supports stimulus-response learning– Functions in sequencing movements

Forebrain

• Diseases of the Basal Ganglia– Huntington's Chorea

• Genetic disorder• Cell death in the basal ganglia• Involuntary “dance like” movements

– Parkinson’s Disease• Projection from the substantia nigra to the basal

ganglia dies• Rhythmical tremors in hands and legs• Rigid movement and difficulty maintaining balance

Forebrain

• Diseases of the Basal Ganglia– Tourette’s Syndrome

• Involuntary motor tics• Complex movements• Involuntary vocalizations

• Basal ganglia diseases are disorders of controlling movement, not producing movement

Forebrain

• Limbic System (limbic lobe)– Amygdala

• Emotion and species-typical behaviors– Hippocampus

• Memory and spatial navigation– Septum

• Emotion and species-typical behavior– Cingulate Cortex (cingulate gyrus)

Forebrain

• Neocortex (cerebral cortex)– Has expanded the most during evolution– Comprises 80% of the human brain– Two cerebral hemispheres, four lobes

Fissures, Sulci, and Gyri

• Fissure– A cleft in the cortex that is deep enough to

indent the ventricles• Sulci

– A shallow cleft in the cortex• Gyri

– A ridge in the cortex

Organization of the Cortex

• Primary Areas– Frontal lobe - Motor functions– Parietal lobe - Body senses– Temporal lobe - Auditory functions– Occipital lobe - Visual functions

Organization of the Cortex in Relation to its Inputs and Outputs

• Secondary Areas– Adjacent to primary areas– Receive input from the primary areas– Engaged in interpreting sensory input or

organizing movements• Tertiary Areas (Association Cortex)

– Located between secondary areas– Mediate complex activities

Cellular Organization of the Cortex– Brodmann’s Map

The Crossed Brain

• Brain has contralateral organization– Each symmetrical half

responds to sensory stimulation from the contralateral side or controls musculature on the contralateral side

CLINICAL VIGNETTES

Brain Structures & Functions:

Brain Structures & Functions:

Brain Structures & Functions: