Neuroanatomy: Structure and Organization

• Functional Neuroanatomy (BMS 345) Lecture 1 is an overview of neuroanatomy
• This material should be a review from BS300

Nervous System Definitions

• Central Nervous System (CNS) equals brain plus spinal cord
• Peripheral Nervous System (PNS) equals nerves plus ganglia
• A neuron is a nerve cell
• Groups of cell bodies in the CNS are cortex, nuclei, and spinal cord columns
• Ganglia are groups of cell bodies in the PNS

Parts of a Neuron

• Soma and dendrites are the input end of the neuron
• Axon is the line
• Nerve terminal is output, fork, or Y
• Grey Matter is a circle
• White Matter lies on line
• Nucleus/Cx is a circle
• Tract (Nerve-PNS) lies on line
• Nucleus/Cx is fork or Y
• (Ganglion-PNS) is a circle

Nuclei and Tracts

• Nuclei contain cell bodies, dendrites, and nerve terminals
• Nuclei are where neurons within the CNS communicate
• Tracts contain axons, but no neuronal cell bodies, dendrites, or nerve terminals
• Tracts serve as pathways
• A group of cell bodies in the PNS is a ganglion
• Within a given tract, all axons serve a similar function
• The optic tract contains axons of neurons found in the retina and carries visual information
• Within one nucleus, all neurons serve a similar function
• The lateral geniculate nucleus of the thalamus involves neuronal cell bodies involved with vision
• Pathway equals a group of nuclei and tracts carrying similar information, and equals functional system
• The pathway includes neurons in the eye sending axons thru the optic nerve and optic tract
• The pathway includes synapses in the lateral geniculate nucleus
• The pathway includes LGN neurons sending their axons thru particular tracts to the cerebral cortex
• All of these nuclei and tracts collectively make up a pathway or functional system involved in vision

Directional Terms

• Superior is toward the top of the skull
• Inferior is toward the bottom of the spinal cord
• Medial is near the midline
• Lateral is away from the midline

Parts of the CNS

• The parts of the CNS, starting at the inferior (caudal) end, include the spinal cord, medulla, pons, midbrain, diencephalon, and cerebral hemispheres
• The forebrain includes the diencephalon and cerebral hemispheres
• The brainstem includes the medulla, pons and midbrain
• The cerebellum is posterior to the pons and medulla, but is not part of the brainstem

Spinal Cord

• Spinal nerves bring information into and out of the CNS
• The spinal cord contains ascending tracts that bring information to the brain
• The spinal cord contains descending tracts that bring information from the brain
• Nuclei are groups of cell bodies processing information

Medulla

• The medulla is continuous with the spinal cord and part of the brain stem
• Cranial nerves IX, X, XI & XII enter and/or exit at the level of the medulla
• The medulla also contains associated nuclei for respiration and cardiac centers
• The medulla contains ascending tracts that bring information to the brain
• The medulla contains desceding tracts that bring information from the brain
• Specific nuclei groups of cell bodies process information

Pons

• The pons is continuous with the medulla and is also part of the brainstem
• Cranial nerves VI, VII, and VIII enter and/or exit at the medulla/pons junction
• CN V is large and located right in the middle of the pons
• It's a major relay to the cerebellum
• Pons contains ascending tracts that bring information to brain
• Pons contains desceding tracts that bring information from brain
• Specific nuclei groups of cell bodies process information

Midbrain

• The midbrain is continuous with the pons and part of the brainstem
• The brainstem equals the medulla, pons, and midbrain
• Cranial nerves III & IV exit at the level of the midbrain
• Cranial Nerves III & IV are related to visual reflexes
• The midbrain contains ascending tracts that bring information to the brain
• The midbrain contains descending tracts that bring information from the brain
• It contains specific nuclei that are groups of cell bodies processing information

Cerebellum

• The cerebellum is located basically in the roof of the pons, but not part of the brainstem
• It's involved with motor functions

Diencephalon

• The diencephalon includes the subthalamus, hypothalamus, thalamus, and epithalamus
• The hypothalamus is important for homeostasis to keep the body and brain within specific parameters necessary for health and life, such as temperature and feeding drive
• The thalamus is an antechamber to the cerebral cortex, and all sensory information (except olfaction) goes thru the thalamus first

Cerebral Hemispheres

• Includes the cerebral cortex, subcortical white matter, and basal nuclei
• The cerebral cortex contains layers of neuronal cell bodies about 5 mm thick
• The cerebral cortex forms a huge sheet that is too big to fit in the skull as a smooth layer, so it's convoluted into bumps and creases
• Bumps of the cerebral cortex equal gyri, and creases equal sulci
• Cerebral cortex is responsible for perception, voluntary movement, and "higher functions"
• Subcortical white matter consists of masses of tracts bringing information to and from each region of the cerebral cortex
• Basal nuclei (also referred to as basal ganglia) include groups of cell bodies involved in motor functions located deep to the cerebral cortex within the cerebral hemispheres

Directional Terms in CNS

• Posterior/Anterior/Superior/Inferior do not change depending on location in the CNS and are the preferred terms
• Dorsal equals your back
• Ventral equals your front
• For the spinal cord and brainstem, dorsal equals posterior and ventral equals anterior
• Rostral is toward the brain, and caudal is toward the feet
• For the forebrain (diencephalon and cerebral hemispheres), dorsal/superior is the top of your head and ventral/inferior is the underneath surface
• Rostral/anterior is toward the front, and caudal/posterior is toward the back because the rostrocaudal axis is bent at the brainstem/diencephalon junction

General Functions of Cranial Nerves

• I. Olfactory-smell
• II. Optic-vision
• III. Oculomotor-eye movement and pupil response
• IV. Trochlear-eye movement
• V. Trigeminal - somatosensation of head and chewing
• VI. Abducens - eye movement
• VII. Facial-sensory and motor, including taste, innervation of muscles of facial expression, and salivary glands
• VIII. Vestibulocochlear - sensory related to head position and movement, and hearing
• IX. Glossopharyngeal - visceral sensory, taste
• X. Vagus-visceral innervation, parasympathetic, taste
• XI. Accessory - neck and shoulder muscles
• XII. Hypoglossal-tongue muscles

Explore the organization of the central nervous system, including axon tracts and neural pathways. Understand directional terms like superior and inferior. Examine the functions of key brainstem areas and neural nuclei.