Gross Anatomy and CNS Organization; Neuroimaging Techniques March 31, 2011

BASICS OF THE CENTRAL NERVOUS SYSTEM

Coronal Slice Sagittal Slice Horizontal Slice Frontal ViewMedial View Dorsal View 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

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

Gray, White, and Reticular Matter Gray Matter Color from capillary blood vessels and neuronal cell bodies White Matter Color from axons covered in an insulating layer of glial cells Reticular Matter Color 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: