CNS vs PNS Overview

CNS vs PNS

• Cell bodies of sensory neurons reside in ganglia of the PNS, outside the skull or spinal vertebrae.
• Sensory neuron process bifurcates, one side delivers sensory signals from the periphery, the other enters the CNS.
• Somatic NS controls voluntary movements, while the Autonomic NS controls involuntary functions.
• Motor neurons in the CNS mainly control somatic motor functions, axons become part of the PNS once they leave the vertebrae region.
• Autonomic preganglionic neurons often originate in the CNS and innervate postganglionic neurons in the PNS, located in various ganglia with autonomic motor functions.

Cerebrum vs Cerebellum

• Cerebrum has two hemispheres, left controls motor function on the right side, right hemisphere controls left side of the body (contralateral).
• Pyramidal decussation occurs in the lower medulla, where the corticospinal tract switches sides.
• Cerebellum controls movement ipsilaterally, left side controls left side, right side controls the right side.

Anatomical Terms

• Anatomical terms are consistent between human and mouse brains.
• Sagittal: divides the brain into left and right halves.
• Transverse: divides the brain into top and bottom portions.
• Anterior: front of the brain.
• Posterior: back of the brain.
• Dorsal: top of the brain.
• Ventral: bottom of the brain.
• Rostral: towards the front of the brain.
• Caudal: towards the back of the brain.
• Lateral: toward the side of the brain.
• Medial: toward the middle of the brain.

Gray Matter vs White Matter

• Gray matter: contains cell bodies and dendrites, responsible for processing information.
• White matter: contains myelinated axons that transmit information between different areas of the brain.
• The term "cortex" can refer to the cerebral cortex or the more superficial gray matter of any brain region.

Major Fissures

• Longitudinal fissure (aka sagittal or interhemispheric fissure): separates the two cerebral hemispheres.
• Transverse fissure: separates the cerebellum from the tectum in rodents and the cortex in humans.

Brain Lobes

• Frontal lobe: bounded by the lateral sulcus ventrally and the central sulcus caudally.
• Parietal lobe: bounded by the central sulcus rostrally, lateral sulcus ventrally, and parieto-occipital sulcus caudally.
• Occipital lobe: bounded by the parieto-occipital sulcus rostrally and the transverse fissure ventrally.
• Temporal lobe: bounded by the lateral sulcus rostrally and dorsally, and the parieto-occipital sulcus caudally.

PNS Divisions

• Somatic: controls voluntary movements.
• Autonomic: controls involuntary functions (smooth muscle, heart, glands).
• Ganglia: contain cell bodies of sensory neurons and postganglionic neurons.

Sympathetic and Parasympathetic Divisions

• Physically separated.

Cranial Ganglia

• 12 cranial nerves, sensory and motor signals mostly to/from head region and GI tract.
• Geniculate ganglion (cranial nerve VII) for taste, and also cranial nerves IX and X.
• Spiral ganglion for auditory and Scarpa's ganglion for vestibular.

Human Brain Development

• Gastrulation: days 11-15.
• Neural induction: days 11-15.
• Neural tube formation: days 16-25.
• Formation of brain vesicles and regionalization: day 28 and beyond.
• Telencephalic vesicles begin, neurogenesis, migration: day 36 and beyond.

Three Germ Layers

• Ectoderm: skin and nervous system.
• Mesoderm: muscle, bone, etc.
• Endoderm: internal organs.

Neural Tube

• Forms from ectoderm.
• Closure of neural tube leads to the formation of the brain and spinal cord.
• Neural crest: forms from ectoderm and gives rise to various cell types, including peripheral neurons and glial cells.

Somites

• Mesodermal origin.
• Contribute to bone and muscle related to spinal vertebrae.
• Added sequentially during development.

Morphogens

• Noggin: a neural inducer produced by mesoderm that induces the overlying ectoderm to become neural.
• Sonic hedgehog (Shh): a ventralizer for dorsal-ventral patterning.
• Retinoic acid (RA): a posteriorizer for anteroposterior patterning.

Explore the differences between the Central Nervous System (CNS) and the Peripheral Nervous System (PNS) in this quiz. Test your knowledge on sensory and motor neurons, as well as the roles of the somatic and autonomic nervous systems. Additionally, learn about the cerebrum and cerebellum's functions and their respective hemispheres.