Nervous System Structure

The Nervous System Central Nervous System (CNS) Peripheral Nervous System (PNS)

Neuraxis The imaginary line drawn through the CNS, from the base of the spinal cord to the front of the brain.

Nervous system directions, in relation to the neuraxis Anterior / Rostral Toward the nose (rOstral  nOse) Dorsal Toward the back Superior Above Lateral Away from the midline Ipsilateral Same side Posterior / Caudal Toward the tail (cAudal  tAil) Ventral Toward the belly Inferior Below Medial Toward the midline Contralateral Opposite side

Contralateral Ipsilateral

Nervous system planes Transverse Sagittal Horizontal Cross section Sagittal section Horizontal Horizontal section

Meninges Three protective layers surrounding the brain and spinal cord Layers of the meninges Brain Pia mater Arachnoid trabeculae Subarachnoid space Arachnoid membrane Dura mater Three protective layers surrounding the brain and spinal cord Dura Mater Arachnoid membrane Pia mater

Ventricles Openings in the brain that contain cerebrospinal fluid (CSF)

Cerebrospinal fluid CSF is made in the choroid plexus CSF flows through the ventricles into the subarachnoid space, where it surrounds the CNS.

Neural development Neural tube Develops into the CNS Neural tube forms 3 ventricles at the rostral end Tissue surrounding ventricles = ventricular zone

Neural development Forebrain Midbrain (Mesencephalon) Hindbrain Telencephalon Diencephalon Midbrain (Mesencephalon) Tectum Tegmentum Hindbrain Metencephalon Myelencephalon

Cellular development Founder cells - in developing brain Initial cells in the ventricular zone Symmetrical division Increases size of the ventricular zone Asymmetrical division Creates neurons while maintaining ventricular zone Stem cells - in the adult brain

Cellular development Radial glia Radial glia ensure development of systematic pathways in the brain.

Cellular development Cortical development ends with apoptosis Neurons grow into adult form with dendrites, axons & terminal buttons Neurons that do not connect with other neurons die

Forebrain - Telencephalon Cortex Limbic system Basal ganglia

Telencephalon Cerebral cortex – surrounds the cerebral hemispheres Gyri (singular: Gyrus) Sulci (Sulcus) Fissures Cortex consists of densely packed glia and neurons Four lobes of the brain Frontal Parietal Temporal Occipital

Cortex - Frontal lobe Prefrontal Cortex Involved in organization of thought, planning actions, and higher cognitive functions.

Cortex - Frontal lobe Primary motor cortex (PMC) Directly controls motor output Somatotopic organization Motor Association Cortex Involved in planning movement

Cortex - Parietal lobe Primary Somatosensory Cortex Receives sensory information Somatotopic organization Somatosensory Association Cortex Somatosensory perception and memories

Cortex - Temporal lobe Primary Auditory Cortex Receives auditory input Auditory Association Cortex Analyzes auditory information Auditory perception and memory storage

Coretex - Occipital lobe Primary Visual Cortex Receives input from the visual system Input comes from the contralateral visual field Visual Association Cortex Analyzes information received in the PVC Involved in visual perception

Cortical connections Corpus Callosum – large bundle of axons connecting corresponding regions of each hemisphere

Telencephalon – Limbic system Located within the telencephalon Includes: Limbic cortex Amygdala Hippocampus Mammillary bodies of the hypothalamus Fornix

Limbic system Major role in emotion, learning and memory

Telencephalon – Basal ganglia Motivation and generation of movement Include: Caudate nucleus Putamen Globus pallidus

Forebrain - Diencephalon Located between the telencephalon and the midbrain Includes: Thalamus Hypothalamus

Diencephalon Thalamus Composed of nuclei that relay information to the proper cortical regions Projection fibers

Diencephalon Hypothalamus Controls the autonomic nervous system and the endocrine system Two major structures control endocrine function Anterior pituitary gland Posterior pituitary gland

Midbrain (Mesencephalon) Structurally and evolutionarily between the diencepalon and the hindbrain Only two major structures Tectum Tegmentum

Midbrain - Tectum Located on the dorsal mesencephalon Superior colliculi Inferior colliculi

Midbrain - Tegmentum Located on the ventral mesencephalon Reticular formation Periaqueductal grey area Red nucleus Substantia nigra

Hindbrain Most primitive brain structure; responsible for basic survival functions Consists of the metencephalon and myelencephalon

Hindbrain - Metencephalon Cerebellum (dorsal brainstem) Attached to the pons by the cerebellar peduncles Coordinates movement Pons (ventral brainstem) Projects information from cortex to cerebellum Role in sleep and arousal

Hindbrain - Myelencephalon Caudal-most region of the brain Contains the medulla oblongata Cardiovascular & respiratory functions, muscle tone, arousal

Spinal cord Cells of the spinal cord Grey matter White matter Cell bodies and unmyelinated axons Dorsal horns Ventral horns White matter Myelinated axons web.lemoyne.edu/.../graphics/spinal_cord.jpg

Spinal cord Spinal nerves 31 pairs of spinal nerves attach to the spinal cord Each spinal nerve consists of a motor efferent (output) and a sensory afferent (input) As each nerve approaches the spinal cord, it splits into a dorsal and ventral root

Spinal cord Dorsal root – carries the sensory axon Cell body is in the dorsal root ganglion Axon enters the spinal cord Ventral root – carries the motor axon Cell body is in the ventral horn of the spinal cord Axon exits to the periphery

Cranial nerves 12 pairs of cranial nerves attach to the ventral surface of the brain. Sensory & motor functions of the face, head, neck and throat.

Peripheral Nervous System Somatic Nervous System Autonomic Nervous System Sensory input Motor control Sympathetic Nervous System Parasympathetic Nervous System “Fight or Flight” Response Utilization of energy resources “Rest & Digest” Response Conservation of energy resources