11.8.Overview of the nervous system.txt

• Understand the general divisions of the NA and their functions
• Understand anatomical direction, planes of section, and appearance of stained and unstained tissue of the CNS; describe the distribution of cranial nerves.
• Understand the general features of the nervous system including: gray/white matter, nuclei, ganglia, nerves, fasciculi (tracts), distribution of gray and white matter in brain vs. spinal cord, function and location of meninge and ventricles, and major blood vessels.

• All spinal nerves and cranial nerves
• All autonomic nerves: sympathetic, parasympathetic, enteric
• All ganglia associated with spinal, cranial, and autonomic nerves: .
• Dorsal Root Ganglia (sensory): contain the cell bodies of sensory spinal nerves
• Cranial nerve Ganglia (sensory): trigeminal, geniculate, spiral, vestibular, superior/inferior ganglia of CN IX, superior/inferior ganglia of CN X
• Autonomic Ganglia (motor): sympathetics and parasympathetics

• chain ganglia
• prevertebral ganglia: (celiac, aorticorenal, superior/inferior mesenterics)

• cilliary
• pterygopalatine
• submandibular
• otic
• terminal

• Composed of Brain and Spinal cord
• Transmit, integrate and process sensory and motor information

• Brain = cerebral hemispheres + brainstem + cerebellum
• Cerebral hemispheres: = telencephalon + diencephalon

• Cortex
• White matter
• Deep nuclei

• Thalamus
• Subthalamus
• Epithalamus
• Hypothalamus

Medulla, pons, midbrain

• 2 hemispheres each with a lateral and medial surface
• lobes
• gyrus
• fissures
• sulcus
• Major components: cortex, deep white matter, and the diencephalon

• Frontal
• Parietal
• Occipital
• Temporal
• Large areas separated by landmarks that correspond to specific functions

a folded, raised portion of surface; convolution

Deep spaces or depressions in the surface

Shallow depression between gyri

• Sensory perception
• Cognition (thinking, reasoning, planning, etc)
• Emotion and memory
• Language ( both comprehension and speech)
• Voluntary movement

• Midbrain, pons, medulla
• Cranial nerves II-XII located rostral to caudal, their positions essential for case solving

• Origin of cranial nerves: sensory, motor, and autonomic information for the head; autonomic information for the body
• A highway between cerebral hemispheres and spinal cord for sensory and motor pathways: …
• Contains vital autonomic centers controlling: consciousness, heartbeat, blood pressure, respiratory rhythm

• Located within the vertebral canal; it extends to vertebral level L1-L2: …
• Segments: cervical (8), thoracic (12), lumbar (5), sacral (5)
• Cervical and lumbosacral enlargements correspond to innervation of limbs

• Incoming sensory info and outgoing motor info for entire body
• Sympathetic and sacral parasympathetic innervation of viscera

• Dura, arachnoid, pia matters
• These 3 also create spaces for blood vessels and nerves to travel
• The spaces are potential sites for hematomas due to head trauma and vascular defects.
• Bacteria and viruses that invade the nervous system can infect the meninges, causing meningitis, which can secondarily affect the underlying nervous tissue.

Outer, toughest layer

Middle layer

Inner-most layer on the surface of the CNS

• Ventricles are located within the cerebral hemispheres and brainstem
• The spinal cord contains a potential space
• CSF is produces in the ventricles and flows into one of the meningeal spaces (subarachnoid space) to surround the brain and spinal cord to proide a protective cushion from surreounding bone.
• CSF also collects brain metabolites, which cannot enter blood vessls due to the BBB
• In lumbar puncture: CSF is sampled from a region around the spinal cord to assess CNS infections
• Sometimes the flow of CSF in the ventricular system is blocked, causing hydrocephalus, which leads to a dangerous increase in intracranial pressure

• Because of their special role in communication, nerve cells have unique structural features: cell body, axon, dendrites, terminals
• Glial cells are intimately associated with neuronal metabolism, signaling, protection, and repair
• Nerve cells communicate at synapses, which allow them to connect to form pathways and to integrate information
• Synaptic communication depends on release of NTs. Many neurological and psychiatric disorders result from abnormal NT release
• Diseases such as multiple sclerosis attach glial cells that prodce myelin surrounding nerve axons, impairing conduction of electrical signals
• Some neurological and psychiatric disorders (Parkinson’s Disease, schizophrenia, depression) result from abnormal release of NTs. Treatments for these disorders involve drugs that alter synaptic transmission

• Axons are collected into bundles. Nerve cell bocies are collected into groups. Asons and nerve cell bodies are separated from one another – because their tasks are different
• Cell body in PNS – ganglion
• Cell body in CNS – nucleus/gray matter
• Axon in PNS – Nerve
• Axon in CNS – Tract or Fasciculus/White Matter

• Unstained: axons (white matter) appear white due to the myelin that surrounds them. Cell bodies (gray matter) appear darker
• In Weigert stain – myelinated axons are stained black, but cell bodies are not stained
• The position of gray and white matter changes throughout the CNS from cerebral hemispheres to brainstem to spinal cord based on functional needs

Disorders of the nervous system usually involve specific locations of injury. These locations overlap with pathways carrying information and result in loss of specific functions. To understand and even predict the deficits that injuries cause, we must understand the arrangement of pathways inside the CNS.

Cerebral hemispheres, brainstem, and spinal cord have different 3-D shapes. Hemispheres are spherical, but the brainstem and spinal cord are cylindrical. Thus, coronal , horizontal, and sagittal section are used to study the hemispheres, but cross-sections (also transverse, axial, horizontal) primarily are used for the brainstem and spinal cord

• For the hemispheres: superior/dorsal; anterior, posterior, inferior/rostral
• For brainstem and spinal cord: superior, caudal, anterior/ventral, posterior/dorsal
• It is important to recognize the orientation of sections, which provides clues to the location in the CNS. Cross-sections of the brainstem and spinal cord differ in shape in different regions because their 3-D geometry changes over their length. As this module progresses, you will begin to recognize the shape of cross-sections.

• Arterial supply to CNS fro 2 major sources:
• Internal carotid arteries – 2
• Vertebral arteries – 2

• Form the anterior circulation
• Give rise to the anterior and middle cerebral arteries
• Supply most of the cerebral hemispheres (frontal, parietal, and superior temporal lobes and deep structures)

• Form the posterior circulation; form basilar artery then 1 posterior cerebral arteries
• Numerous branches of these arteries supply: spinal cord, brainstem, cerebellum, occipital lobe, and inferior temporal lobe
• Anterior and posterior circulation anastomose in Circle of Willis

Caused by a loss of blood supply to a region of the brain. It causes specific sensory/motor deficits that are related directly to structures in the damaged region.