Central Nervous System

Chapter 13Central Nervous SystemBasic parts of the CNSBrain Spinal Cord

BrainBasic Parts : CerebrumCerebellumBrain Stem

Cerebral CortexSulcus- valley (Fissures)Gyrus- Mountains or raised areas

Sulcus and Fissures of the Brain

CerebrumCerebral CortexOuter surface or covering of the cerebrum Gray Matter. Highest center of brain where decisions are made. Only site of conscious awarenessReceives and interprets sensory input, if it doesnt reach the cerebral cortex you wont know what is going on.

Brain death- usually means the cortex has been wiped outAmount of cortex correlates with the intellectual capacity, reptiles have very little compared to humans, rats do not have convuluted cortexCerebral cortex Cerebral Cortex - thin layer of gray matter that is the outermost portion of cerebrum (the part with all the wrinkles)

Cerebrum contCentral Sulcus actually intersects the medial longitudinal fissure.Lobes of BrainFrontal lobe- intellectual powerTemporal Lobe- Primarily hearing and speechOccipital Lobe- receive and interprets visual informationParietal lobe- Sensory reception and processing

Lateral fissures of the brain

Midsaggital viewInside the hemispheres of the brain

Thalamus- every bit of sensory information going to cortex must go through the thalamus except olfactory sense12 Cranial nerves on base of brainMidsaggital brain

HypothalamusHypothalamus- beneath ThalamusSmall but preforms many functions of greatest importance for survival and enjoymentLinks mind and bodyLinks nervous to endocrine

Regulates and coordinates autonomic behaviorRegulates appetite, arousal, body temperature,

Base of brain

Putamen and Globus Pallidus- Make up the Lentiform nucleus which is the part of the basal ganglia responsible for voluntary motor movement. (Effected in Parkinsons)

Internal Capsule- all information to and from the cortex pass through this capsule. Frequent site of stroke.Fibers out of thalamus pass through the internal capsule to the cortex. Sensory thru thalamusMotor fibers descend thru internal capsule and then to spinal cord for reaction.

3 types of fibers in CerebrumProjection fibers- connect the cerebral cortex with the CNSTo cortex are sensory fibersFrom cortex are motor fibers all thru the internal capsuleFanning out of fibers from internal capsule to cortex are called Corona Radi

Association Fibers- connect two portions of the cortex in the same hemisphere. Ie. Frontal lobe to occipital lobe on the right.

Fiber types contCommisural fibers- connect corresponding structures in different hemispheres. 3 sets:Corpus callosumAnterior commisuresPosterior commisures

Without connections the 2 hemispheres are not communicating.

Functional and Structural Areas of the Cerebral Cortex

Sensory Fiber Distribution

Cerebellum (add to your notes)Connected to cerebrum by 3 pedunclesDentate nucleus- influences motor cortexFunctions of cerebellumCoordination of motor movementMaintains balanceControls posture

Brain Stem

Mid brainControls visual and auditory reflexesPineal body- prepare body for sleep or awake state- produces melatonin

Cerebral Peduncles- carry motor fibers from cortex to spinal cord. Peduncles are the only thing connecting the cerebellum to the cortex. Medulla- descending motor fibers.

Coverings of the Brain and Spinal CordOuter Covering Bone, skull and vertebraeInner Coverings- Meninges of the cord continue inside the spinal cavity beyond the end of the spinal cord.Meninges- 3 membranous layersDURA MATER- tough protection from outside. Connective tissue against bone. Doesnt protect against trauma but separates the brain and spinal cord from outside world. Has 3 important extensionsFalx Cerebri- between the two cerebral hemispheres. Contains dural sinuses that function as veins, collecting blood from brain tissues for return to heart. Also Superior saggital sinuses found in cerebrum.

Meninges contFalx Cerebelli- separates the two hemispheres of the cerebellum.Tentorium Cerebelli- between cerebrum and cerebellum

Arachnoid Mater- delicate cobwebby layer between the dura mater and pia materPia Mater- Innermost transparent layer: adheres the outer surface of the brain and SC, forms a slender filament called the filum terminale, at level of the sacrum.Meninges

Cerebrospinal FluidFunctions:Provide a supportive, protective cushionReservoir of circulating fluid, which is monitored by the brain to detect changes in the internal environment. Fluid Spaces:CSF-found within the subarachnoid space around the brain and spinal cord and within the cavities and canals of the brain and spinal cordVentricles- fluid filled spaces within the brain; four ventricles within the brain

CSF- Ventricles of the Brain

Issues with CSFHydrocephally- blockage of blood flow of CSF. No communicating, fluid goes in but releases and insignificant amount. Intracranial pressure results between the dura and pia mater. Meningitis also causes this increase in pressure. Signs include:Loss of consciousnessPupils different sizesPass outHeadacheTreatment- drain CSF out of ventricle with a shunt to another part of body- usually stomach.Spinal CordStructure of the spinal cordOval shapedAnterior Median FissurePosterior median sulcusNerve roots laterally Fibers of dorsal nerve rootCarry sensory information into SCDorsal Root ganglion- cell bodies are unipolar and make up gray matter in dorsal rootFibers of Ventral RootCary motor information out of spinal cordCell bodies of multipolar, motor neurons are in the gray matter of SCSC Anatomy ContinuedInterneruons are located in the spinal cords gray matter coreSpinal nerve- single mixed nerve on each side of the SC where the dorsal and ventral nerve roots join together.

Gray Matter Extends the length of the cordConsists Primarily of cell bodies of interneurons and motor neuronsLooks like an H with the limbs being called anterior, posterior, and lateral horns of gray matter.

White matterSurrounds gray matter and is subdivided in each half on the cord into three funiculi: anterior posterior and lateral horns of gray matterEach funiculus consists of large bundle of axons divided into tracts Names of spinal tracts indicate the location of the tract, the structure in which the axons originate and the structure which they terminate.

Functions of the SCRoutes of conduction to the brainOrganized by structure and function

Ascending Tracts:Lateral spinothalamicAnterior spinothalmicFasciculus, gracilis and cuneateusSpinocerebellarspinotectalTracts continuedDescending tracts:Lateral corticospinal tractAnterior corticospinal tractReticulospinal tractRubrospinal tractTectospinal tractVestibulospinal tractCONSCIOUSNESSState of awareness of ones self, ones environment, and other human beings (Figure 13-21)Depends on excitation of cortical neurons by impulses conducted to them by the reticular activating systemTwo current concepts about the reticular activating systemFunctions as arousal system for the cerebral cortexFunctioning is crucial for maintaining consciousness

LANGUAGEAbility to speak and write words and understand spoken and written wordsSpeech centers: areas in the frontal, parietal, and temporal lobesLeft cerebral hemisphere contains speech centers in approximately 90% of the population; contained in either the right hemisphere or both in the remaining 10%Aphasias: lesions in speech centersEMOTIONSSubjective experiencing and objective expressing of emotions involve functioning of the limbic system (Figure 13-22)Limbic system: also known as the emotional brainMost structures of limbic system lie on the medial surface of the cerebrum (cingulate gyrus and hippocampus)Have primary connections with other parts of the brain, such as the thalamus, fornix, septal nuclei, amygdaloid nucleus, and hypothalamus

MEMORYA major mental activityCortex is capable of storing and retrieving both short- and long-term memoryTemporal, parietal, and occipital lobes are among the areas responsible for short- and long-term memoryStructural changes in the neural pathways of the cerebral cortex store long-term memoriesLimbic system plays a key role in memory