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Nolte – Chapter 3 (Gross Anatomy and General Organization of the Central Nervous System and Peripheral Nervous System) and all Class-Notes and LabNotes tagged with Chapter 3. Dorsal-Ventral all throughout CNS o The cephalic flexure would spate the axes, but we keep the terminology as if it was the same. Cephalic flexure visible at the junction between the brainstem and the diencephalon. Corpus collosum o Splenium at posterior o Body o Genu at anterior Goes a bit ventral to the rostrum. A particularly deep sulci is a fissure Lobe and section markers o Frontal lobe Anterior limit: None Ventral Limit: Separated from the temporal lobe by the lateral sulcus (sylvian fissure) Most ventral region is the orbital part. Ventral Limit(Medial): On the medial surface extends to the cingulate sulcus (but doesn’t include) Posterior Limit (Medial): imaginary continuation of the central sulcus to the cingulate. o Parietal Lobe Anterior Limit: Central Sulcus Posterior Limit: Imaginary line connecting the top of the parieto occipital sulcus and the preoccipital notch. Ventral Limit: as if the calcarine and sylvian connected. Vental Limit(Medial): subparietal and calcarine sulci Posterior limit (medial) parietooccipital sulcus. o Temporal Lobe Dorsal Limit: Sylvian Fissure extension to calcarine Posterior Limit: line connecting top of the parietooccipital notch and the preoccipital notch. Posterior Limit(Medial): imaginary line from preoccipital notch to the splenium. Dorsal Limit (Medial): Collateral Sulcus. o Occipital Lobe Anterior Limit: parietal and temporal lobes on both medial and lateral and surface. o Limbic Lobe Encircles the telencephalon-diencephalon junction. Interposed between corpus collosum and rest of cortical lobes. The operculum covers the insula o Made up of frontal, parietal and temporal. o Circular sulcus outlines the insula and marks it borders with the opercula. Gross Function/Anatomy o Precentral and forward is motor. o Post central and back is sensory. o IFG is split into 3 Oribital(anterior), triangular(middle), opercular(posterior up to the precentral gyrus). Brocas is in Orbital and triangular. o Gyrus rectus The medulla part of the frontal lob just medial to olfactory bulb On the other side of the olfactory bulb(siting in its sulcus) st the orbital gyrus extension. o Parietal Lobe Somatosensory Postcerntral sulcus Superior parietal Lobule Intraparietal sulcus runs from the postcentral gyrus to the parietooccipital sulcus to separate it from the inferior parietal lobule. Inferior parietal lobule Made up of supramarginal gyrus(anterior up to the postcentral gyrus) and angular gyrus(rest) Supramarginal caps the lateral fissure. Angular caps the superior temporal gyrus. Medial Back to the parietoccipital sulcus is the precuneus and bounded ventrally by the calcarine. All that is left after precuneus is the posterior paracentral lobule. These two are separated by the cingulate sulcus. o Temporal Lobe Superior Temporal gyrus Primary auditory cortex Wernicke’s area is the posterior most portion of this. Wraps around in the anterior portion a bit to the medial Medial side Fusiform is most dorsal o Separated by the occipitotemporal sulcus from the inferior temporal sulcus o Occipital ParietoOccippital and calcarine corner off the cuneus. Just inferior to that calcarine sulcus is the lingual gyrus. Most inferior is the fusiform gyrus Lateral Side is all “lateral occipital gyri” V1 is contained in the walls of the calcarine sulcus Rest of the lobe is “visual association” o Limbic Cingulate and parahippocampal Cingulate is on top of diencephalon After it hooks around the genu we see the subcollasal area cap off the cingulate gyrus. Parahippocampal is below. Anterior end that hooks back is the uncus. o Amygdala lies beneath the uncus and the hippocampus follows posteriorly. Superior to it we see the hippocampal sulcus Diencephalon o Thalamus has the third ventricle as a roof(their meeting point is the stria medullaris) o The medial surfaces are fused by the massa intermedia o Hypothalamic sulcus seperates the thalamus from the more inferior hypothalamus. o Hypothalamus connectes with the pituitary by the infundibular stalk. o More inferior are the mammillary bodies. SCN takes 10% of retinal input Right on top of optic chiasm o On the dorsal side, right above the superior colliculi, we find the pineal gland. Midbrain o The tectum goes over the cerebral aqueduct and is made up of the collulculi and the brachium of the inferior. o The cerebral peduncles o Red nuclei Rubrospinal tract starter Important motor nuclei for cerebellum Pons o Pontine tegmentum forms floor of the fourth ventricle. Medulla o Rostral open, caudal closed. o Medullary pyramids are just below the basal pons. Decussate at region of medulla to the spinal cord. Cerebellum o Vermis – midline Lateral hemisphere encapsulating it o Anterior lobe Separated by the primary fissure. Afferent inputs from spinal cord o Flocculonodular lobe Nodulus(vermal portion), flocculus(vestibulocochlear nerve) Afferents from vestibular o Posterior love Largest Gets relay from pontine nuclei. Coordination of voluntary movements. Hippocampus o Efferent fiber bundle: fornix o Folded into the termporal lobe forming part of the wall of the alteral ventricle. o Becomes smaller as the temporal lobe curves into the parietal lobe. Ends near the splenium of the CC o Fornix ends in the mammillary bodies. Basal Ganglia o Lenticular nucleus Putamen and globus pallidus o Caudate Head in frontal lobe Body and tail that follow the lateral ventricle around into the temporal lobe Sepearted from the lenticular by the internal capsule which interconnects cerebrum with basal ganglia processes and thalamus Relevant Cranial Nerves o II goes into the chiasm and becomes the tract Only one that projects directly into the diencephalon(remember retina is actually part of diencephalon) o III emerges from the interpeduncular fossa between the cerebral peduncles. This is just below the mammilarry bodies The infundibulum is superior to mammillary bodies. o IV the only to emerge from the dorsal side Just caudal to the inferior colliculi o V emerges from the lateral portion of the basal pons. Miscellaneous o Thalamocortical fibers are uncrossed o Cerebellum is ipsilateral o Spinothalamic is pain-temperature o Cerebellar outputs return to the motor cortex and affect corticospinal activite (but go through thalamus) Must cross midline before thalamus. Basal ganglia also affect motor output this way. They don’t receive sensory input as directly, though. o Layer IV receives sensory input If this layer is tiny, then its probably not a sensory based cortex o Layer V is output (pyramidals) Go down through the peduncles and medulla(decussate) and go down the spinal cord to contact primary motor neurons This is the coricospinal tracts o Layer VI receives input from thalamus Peripheral Nervous System Peripheral nerves do not cross the midline Afferent o Go towards the CNS o Primary afferents in the dorsal root ganglia hug the spinal cord These are psudounipolar Efferent o Fibers that go away o Cell bodies reside inside the gray matter Dorsal-Ventral o Bell-Magendie Law Sensory axons enter the dorsal root But not limbo-sacral pain fibers Motor axons exit via the ventral root Plexi o Organized web of fibers like a tree branch that get more and more focal as you get closer to innervations. E.g: brachial plexus will cover everything in the arms. Peripheral Nerves and Conduction o Ia are primary muscle spindle afferents o Ib are golgi tendon organ afferents o II are spindle secondaries Meissner, merkel, etc. o III are free nerve endings for temperature and sharp pain o IV(c) are free nerve endings as well Unmyelinated Slow pain o Reception depends on intensity and duration pacininian can absorb initial energy and adapt quickly, so vibration would be something that would get it to fire. o Receptor type depends on location and quality homonculus o Extrinsic mechanism can affect reception as well bright light can be received but can also trigger a contraction of the pupil. intrafusal and extrafusal efferents can made more and less sensitive. Glia o Schwann Wrap around the axon in an engulfing fashion also provide metabolic support especially in dorsal root ganglia they can make a type of matrix and rovide scaffolding for axonal growth after injury. Muscle Spindles o receptor organs that lie in parallel to our muscle fibers o tell us about the length of our muscle and the rate of change of this muscle o nuclear chain fibers and their flower outbranches respond primarily to length and will fire when the muscle is lengthened. o nuclear bag fibers with their annulospiral endings will to the rate of change o Gamma motor neurons will regulate the sensitivity to stretch when muscle is relaxed. allows the nucleur bag to stay tense Golgi tendon organs are between the muscle and tendon and will be activated by isometric contractions. o respond to tension o slow adapting, so they can keep up the maintenance. Autonomic Nervous System o nerves that go to our viscera o all the efferents go through a ganglia o Sympathetic flight or fight efferents comes out of ventral horn B type fibers will synapse near the sympathetic ganglion with acetylcholine and then innervate with norepinephrine. o except for sweat glands which are cholinergic. o preganglionic can also innervate the adrenal medulla that then secretes norep. the sympathetic ganglion are near the spinal cord and primarily in thoracic and upper lumbar o thoracolumbar outflow. can be interconnected to form a sympathetic chain. travel from spinal cord to the sympathetic chain ganglion via the white communicating rami o Parasympathetic more normal Ganglion are closer to the vicera of interest use acetylcholine on parasympathetic ganglia and the actual viscera. mainly in sacral spinal nerves and cranial nerves none in the limbs more focal in its control than the sympathetic. o There is always a stop at autonomic ganglia(post ganglionic) the preganglionic has its cell body in the CNS and are thinly myelinated in route to the ganglia. the actual postgalionic innervations are unmyelinated. this is different from the somatic motor system where we just have the cell body in CNS whose axons go directly to skeletal muscle. Injuries o damage to a nerve causes willerian degeneration, where neurons distal to the cut will start to die and the axon will regress to the closest node of ranvier. the schwann cells will remain, though, as scaffolding. o Collateral sprouting can occur from preserved tips f axons they can follow the NGF given off by schwann cells and simultaneously grow through the schwann scaffolding. Pain o Nociceptive. hurt ow. o Neuropathic dull aching (due to damage of neural tissue) o Free nerve endings release potassium and other chemical mediators o C fibers slow conduction(no myelinated) 2nd pain o A-delta Fibers III fast conducting 1st pain o Gate-Theory incoming pain stimuli can be regulated because the incoming stimuli compete with sensory inputs and cortical modulations. we rub periphery so that the signal can compete touch will be faster than the slow transmitting c fibers, so we keep touching and rubbing to overpower the slow pain. o Referred pain the area to which pain is referred correspond to the dermatome innervated by the spinal segment to which the visceral afferent project. visceral afferent fibers accompany sympathetic efferents o subserve visceral reflexes and don’t really reach consciousness but can if it is enough or if the organ is inflamed.