Lecture title: cerebral cortex Lecture number: 4 Doctor: Eizz Elden meqdadi

Transcription

1 Nervous system Lecture title: cerebral cortex Lecture number: 4 Doctor: Eizz Elden meqdadi Raghad ibrahim فقل لمرج معال االمور بغ ر اجتهاد: رجوت لمحاال

2 *slides included in the sheet Cerebral Hemispheres Longitudinal fissure separates left & right cerebral hemispheres Cerebral cortex is gray matter overlying white matter 2 4 mm thick containing billions of cells grew so quickly formed folds (gyri) and grooves (sulci or fissures) Corpus callosum is band of white matter connecting left and right cerebral he mispheres Each hemisphere is subdivided into 4 lobes *cerebral cortex with laminae up to six, these layers different from area to another in brain according to function.

3 Cerebral Lobes Longitudinal fissure Lateral sulcus (of Sylvius) Frontal lobe Central sulcus (of Rolando) Parietal lobe Parieto occipital sulcus Occipital lobe Preoccipital notch Calcarine sulcus Temporal lobe Insula *central sulcus that separate frontal lobe from parietal lobe, and the only sulcus goes from longitudinal fissure up to the lateral fissure *most sulci interrupted but the central sulcus usually continuous. *lateral fissure divides both the frontal lobe and parietal lobe above from the temporal lobe below. *the lateral fissure with side branches: A) anterior ramus: 1) horizontal branch 2) ascending branch (vertical branch) B) posterior ramus *These rami can be converted to sulci *parieto-occipital sulcus separates between occipital and parietal lobes that appear mostly in the medial side and slightly in the lateral side and ends in the medial side. *preoccipital notch About 5 centimeters in front of the occipital lobe on the infero-lateral border is an indentation or notch. It is considered a landmark because the occipital lobe is located just behind the line that connects that notch with the parieto-occipital sulcus.

4 *this line from parietooccipital sulcus and preoccipital notch vertical to lateral fissure lead to complete separation between temporal and parietal lobes. Frontal Lobe: Laterally Sulcus Precentral gyrus sulcus Superior frontal gyrus frontal sulcus Middle frontal gyrus frontal sulcus Inferior frontal gyrus *Frontal lobe anterior to central sulcus and above lateral fissure Frontal lobe gyri:

5 Precentral gyrus : The 1st gyrus in front of the central sulcus is called anatomically Precentral gyrus,functionally Primary motor area. It was given number 4 *in front of precentral gyrus precentral sulcus (notice it is interrupted ) *precentral gyrus directs vertically the rest gyri of frontal lobe direct horizontally. *there are three frontal gyri other than precentral gyrus: Superior, middle and inferior frontal gyri, separate between them inferior and superior frontal sulci. *as we said the lateral fissure with anterior and posterior rami, and anterior rami with ascending and horizontal branches that divide inferior frontal lobe to 3 parts: *Orbital gyri (pars orbitalis): anterior to horizontal ramus *pars triangularis: between horizontal and vertical rami *pars opecularis: posterior to vertical ramus Inferior frontal gyrus Orbital gyri horizontal ramus

6 Triangular gyrus* Opercular gyrus* *form speak (Broca s) area ascending ramus In the back of inferior frontal gyrus "is special in the left hemisphere" is the area responsible for the speech "Broca's area". *pars opecularis + pars triangularis = functionally called broca's area *primary motor area for muscles responsible for the speech. Frontal Lobe: Inferiorly Rectus (straight) gyrus Most medial Olfactory sulcus Olfactory bulb Olfactory tract Medial & lateral olfactory striae Anterior perforating substance Orbital gyri

7 *olfactory bulb and olfactory tract within olfactory sulcus (or rectus sulcus) that above nasal cavity. *medial to olfactory sulcus (rectus gyrus). *olfactory tract divided to medial and lateral olfactory striae *olfactory tract crossing over other side hemisphere by medial olfactory stria *lateral olfactory stria to other olfactory cortical area *the area between medial and lateral olfactory striae (anterior perforated substance) *from google, Olfactory bulb, structure located in the forebrain of vertebrates that receives neural input about odors detected by cells in the nasal cavity. The axons of olfactory receptor (smell receptor) cells extend directly into the highly organized olfactory bulb, where information about odors is processed.

8 *from google, the olfactory tract is a bundle of afferent nerve fibers from the mitral and tufted cells of the olfactory bulb that connects to several target regions in the brain Parietal Lobe: Laterally sulcus Postcentral gyrus sulcus Superior parietal lobule sulcus Inferior parietal lobule

9 *parietal lobe posterior to central sulcus *postcentral gyrus The postcentral gyrus lies in the parietal lobe, posterior to the central sulcus, functionally primary somatosensory area. *posterior to post central gyrus (post central sulcus) *rest of parietal lobe with two gyri superior and inferior parietal gyri separated by intraparietal sulcus Inferior parietal lobule Supramarginal gyrus* Lateral sulcus Angular gyrus* Superior temporal sulcus *inferior parietal lobule divided into two gyri *lateral posterior ramus of lateral fissure ends within parietal lobe surrounded by supramarginal gyrus. *superior temporal sulcus ends in the parietal lobe and surrounded by angular gyrus * form language (Wernicke s) area *supramarginal+angular gyrus+superior temporal gyrus = wernicke s area (mostly found in the left cerebral hemisphere). *if brocas area damaged you lose the ability to speech *if wernickes area damaged you can talk but incomprehensible talking. بح ث البروكاز مسؤولة عن انقباض العضالت الت تساهم ف احداث الصوت واخراج الكالم ب نما الو رنكز مسؤولة عن فهم اللغة المنطوقة بح ث ف حال ضرر هذه المنطقة من الدماغ س تحدث االنسان اال انه ستكون الكلمات غ ر مترابطة ومفهومة.

10 Occipital Lobe: Medially Lingual gyrus Cuneus Precuneus (parietal lobe) sulcus

11 *sulcus within occipital lobe called calcarine sulcus. *calcarine sulcus extends toward temporal lobe. *in the occipital lobe (lingual gyri) *between calcarine sulcus and parieto-occipital lobe area called (cuneus). *in front to parieto-occipital lobe area called pre-cuneus. Temporal Lobe: Laterally sulcus Superior temporal gyrus Transverse temporal gyri (of Heschl) Buried in the lateral fissure Primary auditory cortex temporal sulcus Middle temporal gyrus temporal sulcus Inferior temporal gyrus

12 *inferior to lateral fissure (temporal lobe) *laterally, superior, middle and inferior temporal gyri. *superior and inferior temporal sulci (or middle temporal sulcus) *superior and middle temporal gyri appear completely laterally while small part of inferior temporal gyrus. *transverse temporal gyri From Wikipedia: The transverse temporal gyri (also called Heschl's gyri or Heschl's convolutions) are found in the area of primary auditory cortex buried within the lateral sulcus of the human brain. Transverse temporal gyri are superior to and are separated from the planum temporale (cortex involved in language production) by Heschl s sulcus. *superior temporal gyrus will continuous within the fissure toward the insula, this part buried inside the lateral fissure called transverse temporal gyrus, very important it is primary auditory cortex (responsible of hearing). Temporal Lobe: Inferiorly Inferior temporal gyrus Most lateral Occipitotemporal sulcus Occipitotemporal gyrus (fusiform gyrus) Extend to the occipital lobe Collateral sulcus Parahippocampal gyrus Most medial Uncus Small medial extension

13 *inferior temporal gyrus separated from other gyri by occipitotemporal sulcus (or inferior temporal sulcus). *after inferior temporal sulcus (occipitotemporal gyrus) or (fusiform gyrus), it is extended from temporal toward occipital lobe. *after fusiform gyrus (collateral sulcus ) then parahippocampal gyrus, anteromedial extension of it called (uncus), the believed it is related to olfaction process.

14 Main Medial Structures Corpus callosum parts Cingulate gyrus Continue with the parahippocampal gyrus sulcus Paracentral lobule Medial frontal gyrus

15 *corpus callosum commissural fibers between two hemisphers, above corpus callousum three is a sulcus called (callosal sulcus), above callosal sulcus (cingulate gyrus) part of limbic system it is cross from frontal lobe up to temporal lobe. *after cingulate gyrus (cingulate sulcus). *central sulcus ends medially, surrounded by paracentral gyrus, it is connection between primary motor area and somatosensory area, a connection between frontal and parietal lobes. *the rest of frontal lobe called (medial frontal gyrus) Collateral sulcus لوال المشقة ساد الناس كلهم الجود فقر واالقدام قت ال Medial Temporal Lobe Hippocampal Formation Parahippocampal gyrus Perirhinal cortex Entorhinal cortex Parahippocampal cortex Subiculum Hippocampal sulcus Hippocampus (cornu ammonis) CA1, CA2, CA3 Dentate gyrus

16 *collateral sulcus separated parahippocampal and occipitotemporal gyri. *from Wikipedia: Medial temporal lobe structures that are critical for long-term memory include the hippocampus, along with the surrounding hippocampal region consisting of the perirhinal, parahippocampal, and entorhinal neocortical regions. *parahippocampal with three areas: * Perirhinal cortex Entorhinal cortex Parahippocampal cortex *parahippocampal gyrus part of medial temporal lobe *parahippocampal cortex divided into three parts *most anterior part (perirhinal cortex) following uncus in olfaction process *middle part (entorhinal cortex) *most posterior part (parahippocampal cortex) part of limbic system *the most important one (entorhinal cortex) *deep to entorhinal cortex called (subiculum), there is a sulcus called hippocampal sulcus.

17 *hippocampal gyrus between hippocampal sulcus and collateral sulcus. *hippocampus (cornu ammonis ) *hippocampus divided into (CA1,CA2,CA3) شبه الكائن البحري المسمى بالحص ن *the end of hippocampus covered by another gyrus called (dentate gyrus.

18 *hippocampal formation: a compound structure of medial temporal lobe, The hippocampal formation consists of the dentate gyrus, the hippocampus proper (cornu ammonis [CA] regions), and the subiculum. *hippocampus part of hippocampus formation. *parahippocampus gyrus: (Syn. hippocampal gyrus) is a grey matter cortical region of the brain that surrounds the hippocampus and is part of the limbic system. *parahippocampus cortex A distinction must be made between the preceding terms and what each indicates. The hippocampal cortex has 3 layers Molecular layer at the center Consists of interacting axons & dendrites Hippocampus Prominent pyramidal cell layer of large neurons Polymorphic layer containing axons, dendrites & interneurons The dentate gyrus has 3 layers like hippocampus but the pyramidal cell layer is replaced by granule cell layer

19 Hippocampal Formation Intrinsic Circuitry Most of the hippocampal afferent come from the entorhinal cortex (perforant pathway) Granule cells in the dentate gyrus sends dense fibers (Mossy fibers) to CA3 CA3 pyramidal neurons send fibers through the fornix (alveus) and collaterals (Schaffer collaterals) to the CA1 CA1 sends fibers to subiculum Subiculum sends fibers to entorhinal cortex *from Wikipedia The trisynaptic circuit is a relay of synaptic transmission in the hippocampus, which is made up of three major cell groups: granule cells, CA3 ("Cornu Ammonis" area 3) pyramidal neurons, and CA1 ("Cornu Ammonis" area 1) pyramidal cells. The hippocampal relay involves 3 main regions within the hippocampus which are classified according to their cell type and projection fibers. The first projection of the hippocampus occurs between the entorhinal cortex and the dentate gyrus. The entorhinal cortex transmits its signals from the parahippocampal gyrus to the dentate gyrus via granule cell fibers known collectively as the perforant path. The dentate gyrus then synapses on pyramidal cells in CA3 via mossy cell fibers. CA3 then fires to CA1 via Schaffer collaterals which synapse in the subiculum and are carried out through the fornix. Collectively the dentate gyrus, CA1 and CA3 of the hippocampus compose the trisynaptic loop. EC DG via the perforant path(synapse 1), DG CA3 via mossy fibres(synapse 2), CA3 CA1 via schaffer collaterals(synapse 3)

20 *hippocampus also called old cortex. *if we talk about new cortex we excluded hippocampus cortex. *molecular layer function receive afferent fibers. *middle layer of cortex contain large number of pyramidal cells (most important cells of cortex) it gives efferent fibers outside the cortex. *polymorphic layer with mixed cells (neuroglia, small cells and neurons) *dentate gyrus with three layers but replaced the middle layer by granule cells. *granule cells connect the different parts of cortex itself no efferent fibers.

21 *entorhinal cortex after the formation reach by performant pathway toward different parts (parahippocampal gyrus, subiculum, hippocampus, and dentate gyrus). *from the dentate gyrus the circuit start, fibers to the ca3 called (mossy fibers pathway), btw hippocampal part (schaffere collateral pathway), ca1 to subiculum and from subiculum to entorhinal cortex, we forming complete circle. *the strongest theory that illustrate the memories process it is transfer of information through the circuit. *memories are action potential, if stopped the information will disappear, so the circuit very important to keep our memories. Alveus Fornix Efferent fibers of hippocampus to fornix Fimbria of hippocampus Fornix Parts Crura (posterior columns) Body Columns (anterior columns) Mamillary bodies *efferents from hippocampus collected together forming alveus *alveus collected and forming (fimbriae) *fimbriae forming (fornix) toward the hypothalamus mamillary bodies *fornix connected btw hippocampus and hypothalamus. *fornix part of limbic system.

22 Functional Organization of the Cerebral Cortex: Sensory Areas Primary somatosensory area postcentral gyrus. Primary visual area occipital lobe. Primary auditory area temporal lobe. Primary gustatory area base of the postcentral gyrus. Primary olfactory area temporal lobe.

23 Functional Organization of the Cerebral Cortex: Motor Areas Primary motor areaprecentral gyrus. Broca s speech area left cerebral hemisphere. Functional Organization of the Cerebral Cortex: Association Areas: a region of the cortex of the brain which connects sensory and motor areas, and which is thought to be concerned with higher mental activities.(frm Wikipedia) Somatosensory association area posterior to primary somatosensory area. Visual association area occipital lobe. Auditory association area temporal lobe. Wernicke s area left temporal and parietal lobes. Prefrontal cortex anterior portion of the frontal lobe.

24 Brodmann Numbers: Originally defined and numbered into 52 regions by the German anatomist KorbinianBrodmann in the early 1900's, the Brodmann areas of the cerebral cortex are defined by its cytoarchitecture (histological structure and cellular organization) Area 17 Primary visual cortex Areas 18 & 19 Secondary visual cortex Area 4 Primary motor cortex Area 6 Premotor area Area 3, 1, & 2 Somatosensory cortex Areas 41& 42 Auditory cortex Areas 44 & 45 Broca s area Areas 39 & 40 Wernicke s area Area 8 Frontal eye field Somatotopic Organization of Cortex (Homunculus) لن تعبر حتى ص ر الصبر مادة لحمك..