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Cerebrum and Deep Brain structures 4 year Intercalating Medical Student University of ManchesterCONTENTS 1. Embryology 2. Quiz 1 3. Gyri, Sulci and Lobes 4. Functional and Histological structure 5. Deep Brain structures 6. Quiz 2EMBRYOLOGY 1. At 4 weeks gestation, the neural tube will give rise to three outpouchings- prosencephalon (forebrain), the mesencephalon (midbrain), and the rhombencephalon (hindbrain) 2. In the next few weeks, the forebrain divides into endbrain (telencephalic) and inter- brain (diencephalic) vesicles 3. Between the 8 and 10 weeks of gestation, transitory furrows appear that last until the 4 month of gestation 4. During the 4 and 5 months of gestation, the first identifiable sulci (olfactory, calcarine, parietooccipital, cingulate, and central) begin to appear, followed by additional secondary and tertiary sulciQUIZ 1 1. How many total gyri are there in the frontal and temporal lobe? 1. 3 2. 4 3. 5 4. 6QUIZ 1 1. Which lobe is the hippocampus located in? 1. Frontal 2. Temporal 3. Insular 4. CingulateQUIZ 1 1. What makes up the temporal operculum? 1. Sylvian sulcus 2. Supratemporal gyrus 3. Infratemporal gyrus 4. Superior Temporal gyrusQUIZ 1 1. What cortex is marked in green? 1. Insular 2. Cingulate 3. Papez 4. TemporalQUIZ 1 1. Which lobe when affected cause contralateral neglect? 1. Frontal lobe 2. Parietal lobe 3. Temporal lobe 4. Occipital lobeSULCIANDGYRI 1. Complex pattern of ridges (gyri) and furrows (sulci) 2. Vary in size and shape from person to person 3. Separate the different lobesGENERALOVERVIEWCADAVERICDISSECTIONSCADAVERICDISSECTIONSHISTOLOGYOFTHECORTEX 1. Layer 1 – Most superficial layer 2. Layer 2 – Establishes intracortical connections 3. Lcommissural fibrese to association and 4. Layer 4 – Site of termination of afferent fibres from the thalamic nuclei 5. Lextracortical targetsojection fibres to 6. Layer 6 – Contains association and projection fibresFUNCTIONS 1. Brodmann’s Area were historically used 2. Lobar function is determined by the cortices they contain 3. Frontal lobe – Primary motor cortex, premotor cortex, supplementary motor cortex, visual eye fields, Broca’s area 4. Parietal lobe – Primary somatosensory cortex, sensory association cortex 5. Temporal lobe – Primary auditory cortex, auditory amygdalaion cortex, Wernicke’s area, Hippocampus and 6. Occipital lobe – Primary visual cortex, visual association cortex DEEPBRAINSTRUCTURES Cingulate gyrus Thalamus Hypothalamus Pituitary gland Pineal glandINSULALOBE • Triangular shape • Found at the floor of the lateral sulcus (Sylvian fissure). • Covered by the opercula of the frontal, temporal and parietal lobes. • Lthe insula and represents the level at which the middle cerebral of artery (MCA) bifurcates/trifurcates. • Major central sulcus that separates the insula: • Anterior: anterior, middle, posterior short gyri • Posterior: anterior and posterior long gyri • Connected to neocortex, basal ganglia, thalamus and limbic system. • Important role in desire, cravings, addiction and psychiatric disorders. THALAMUS • Paired gray-matter mass • Acts as a central hub which relays motor and sensory impulses between the higher centers of the brain and the PNS. • Lies at the core of the diencephalon which is derived from the prosencephalon. • Arterial supply: • Posterior cerebral artery (PCA) • Contributions from the posterior communicating artery (PCOMM) THALAMICNUCLEI • Nuclei are subdivided into dorsal and ventral nuclei. • Medial nuclei: integrate special, somatic and visceral afferent information with emotions. • Lateral nuclei: • VA and VL are involved in motor cortex activity. • capsule and corona radiata.rimary somatosensory cortex via internal Medial nuclei Lateral nuclei • Anterior nuclei is integrated with the limbic system and helps Anterior nuclei organize emotion and recent memory. • Medial geniculate body: • Primary thalamic auditory nucleus • Afferents from inferior colliculus • Efferents to primary auditory cortex in superior temporal gyrus • Lateral geniculate body: • Primary thalamic visual nucleus • Afferents from retina of both eyes • Efferents to the primary visual cortex in occipital lobeHYPOTHALAMUS • Centrally located part of the brain that connects the CNS to the endocrine system via the pituitary gland. • Connected to the pituitary by the pituitary stalk. • Part of the diencephalon. • Contains masses of grey matter (nuclei) that synthesize different hormones in response to physiological changes. • Divided into four regions, each containing different nuclei: • Preoptic à preoptic nucleus. • Supraoptic àsuprachiasmatic, supraoptic, paraventricular and anterior nuclei. • Tuberal à dorsomedial, ventromedial, arcuate, premammillary and lateral tuberal nuclei. • Mamillary à mamillary and posterior nuclei. • Arterial supply is via the anterior (ACA) and posterior circulation (PCA and PCOMM) with contributions from the superior hypophsyeal artery.KEYHYPOTHALAMICNUCLEI • Preoptic nucleus à thermoregulation • Supraoptic à produces vasopressin (ADH) and oxytocin • Suprachiasmatic à circadian rhythms • Paraventricular à secrete hormones like supraoptic • Paraventricular and supraoptic nuclei contain magnocellular neurosecretory cells. • Mamillary nuclei (bodies) à recollective memory • Other nuclei are involved in: • Hunger • Fear • Thermoregulation • Sexual activity • SleepPITUITARYGLAND(HYPOPHYSIS) • Pea-sized oval shaped endocrine organ that is suspended from the underside of the brain by the pituitary stalk. • Lies in the sella turcica of the sphenoid bone. • Superior surface is covered by the diaphragma sellae with the optic chiasm directly above it. • Two lobes: • composed of glandular epithelium à secretes GF, LH, FSH, ACTH, TSH, PRL, MSH. • Posterior lobe (neurohypophysis) à arises from the forebrain and is an extension of the hypothalamus à secretes ADH and oxytocin which are produced by the supraoptic and paraventricular nuclei of hypothalamus. • Arterial supply: • anastomotic network around the hypothalamus called the hypophyseal portal system. • Posterior lobe à superior hypophyseal artery (branch of C6), infundibular artery (branch of PCA) and inferior hypophyseal artery (branch of C4).PINEALGLAND(EPIPHYSIS) • Small cone-like neuroendcrine structure that projects posteriorly from the wallof third ventricle. • Rests in a groove between the two superior colliculi. • Part of the epithalamus of the diencephalon. • Penealocytes secretes melatonin and other polypeptide hormones into the surrounding network of fenestrated capillaries à important in maintaining the body’s circadian rhythm and regulating the sleep-wake cycle. • Has a role in the onset of puberty and the development of the reproductive system. • Posterior choroidal arteries of the PCABASAL GANGLIADIRECTP ATHWAY 1. Voluntary movement is initiated by the frontal cortex. 2. Excitatory signals are sent to spiny neurons in the striatum (caudate nucleus and putamen) via corticostriatal fibres, utilising the neurotransmitter glutamate. 3. The striatum then projects inhibitory (GABAergic) axons to the globus pallidus internus (GPi) and the substantia nigra reticulata, therefore preventing inhibition of thalamus. 4. Thalamus is now disinhibited and is able to send messages back to the cortex via thalamocortical fibres. 5. This therefore okays the desired movement. 6. Motor cortex then sends a signal down the spinal cord thus causing the desired movement.INDIRECTP ATHWAY 1. Voluntary movement is initiated by the frontal cortex. 2. Excitatory signals are sent to spiny neurons in the striatum (caudate neurotransmitter glutamate.rticostriatal fibres, utilising the 3. The striatum then projects GABAergic fibres to the globus pallidus externus (GPe). 4. GPe will decrease its inhibitory effects on the subthalamic nucleus. 5. Subthalamic nucleus increases in activity, sending excitatory glutamatergic fibres to the GPi. 6. signals to thalamus.n become more active, therefore sending inhibitory 7. Thalamocortical fibres are now inhibited and therefore excitation of the motor cortex ceases. 8. Cortex can no longer send an impulse down the spinal cord, resulting in a decrease in movement.LIMBICSYSTEM( PAPEZCIRCUIT) • Functions: • Feeding (satiety & hunger) • Forgetting (memory) • Fighting (emotional response) • Family (sexual reproduction and maternal instincts) • Fornicating (sexual arousal) • Key Parts: • Amygdala: almond shaped à fear and anxiety responses • Hippocampal formation: floor of temporal horn o lateral ventricle à memory, navigation, attentionQUIZ 2 1. Which thalamic nucleus does the DCML tract end in? 1. VPA 2. VPM 3. VL 4. VPLQUIZ 2 1. What makes up the corpus striatum? 1. Caudate + Putamen + Claustrum 2. Caudate + Putamen 3. Putamen + Globus Pallidus 4. Caudate + Putamen + Globus PallidusQUIZ 2 1. Which two hypothalamic nuclei release the posterior pituitary hormones? 1. Supraoptic + Suprachiasmatic 2. Pavaventricular 3. Suprachiasmatic + Preoptic 4. Supraoptic + ParaventricularQUIZ 2 1. What sulcus does the white box represent? 1. Intraparietal sulcus 2. Posterior ramus of Sylvian 3. Intermediate sulcus of Jensen 4. Interparietal sulcusQUIZ 2 1. What separates the putamen and the globus pallidus? 1. External capsule 2. Internal medullary lamina 3. Extreme capsule 4. External medullary laminaThank you for listening!! Email: sayan.biswas@nhs.net joshua.macarthur@student.manchester.ac.uk