DIENCEPHALON. ..Central core of the forebrain..consists of three paired structures

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2 DIENCEPHALON..Central core of the forebrain..consists of three paired structures thalamus, hypothalamus, epithalamus..encloses the third ventricle

3 Diencephalon between cerebral hemispheres and brainstem surrounds third ventricle thalamus hypothalamus optic tracts optic chiasm infundibulum posterior pituitary mammillary bodies pineal gland 11-32

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5 Thalamus Paired, egg-shaped masses that form the superolateral walls of the third ventricle Connected at the midline by the intermediate mass Nuclei project and receive fibers from the cerebral cortex Final relay point for ascending sensory information Coordinates the activities of the cerebral cortex and basal nuclei

6 Grey matter nucleus of thalamus Subdivisions of the Thalamus Medial nuclear group, lateral nuclear group, anterior nuclear group Internal medullary lamina Intralaminar nuclei Midline thalamic nuclei Thalamic reticular nucleus

7 Relay Nuclei Most of thalamus consists of relay nuclei. Relay nuclei receive inputs from pathways, process the input and send it on to a particular region of cerebral cortex. All sensory modalities except for olfaction have a relay in the lateral thalamus that projects to a specific region of cerebral cortex. Ventral posterior lateral nucleus (VPL): somatosensory relay from body (C2 and below) Ventral posterior medail nucleus (VPM): somatosensory relay from cranial nerves Lateral geniculate nucleus: visual relay Medial geniculate nucleus: auditory relay Ventral lateral nucleus: motor relays from cerebellum and basal ganglia Anterior nuclear group: limbic connections to cingulate gyrus

8 Intralaminar Nuclei Unlike relay nuclei, their main inputs and outputs are from the basal ganglia. Caudal intralaminar nuclei: including large centromedian nucleus; involved mainly in basal ganglia circuitry Rostral intralaminar nuclei: reciprocal connections with basal ganglia; connections with ascending reticular activating system Reticular Nucleus Only nucleus of thalamus not projecting to cerebral cortex. Inputs from other thalamic nuclei and cortex and projects to other thalamic nuclei. Inhibitory control of other thalamic nuclei Also may function in alertness & attention

9 Hypothalamus Located below the thalamus, it caps the brainstem and forms the inferolateral walls of the third ventricle Mammillary bodies Small, paired nuclei bulging anteriorly from the hypothalamus Relay station for olfactory pathways Infundibulum stalk of the hypothalamus; connects to the pituitary gland Main visceral control center of the body

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11 --optic part --tubersl part --mamillary part

12 Optic part: 1. Supraoptic nucleius 2. Paraventrical nucleus Tuberal part: 3. Ventromeddial nucleus 4.Dorsomedial nucleus 5.Tuberal nucleus Mamillary part 6.Posterior nucleius 7.Lateral nucleus

13 Functions 1. Endocrine control: regulate secretion of TSH, ACTH, STH, LH,FSH 2. Neurosecretion; supraoptic and paraventricular nuclei produce ADH and oxytocin 3. Controls autonomic function, Regulates blood pressure, rate and force of heartbeat, digestive tract motility, rate and depth of breathing, and many other visceral activities 4. Produces emotions and behavioral drives 5. Regulates feelings of hunger and satiety 6. Regulates sleep and the sleep cycle

14 Epithalamus Most dorsal portion of the diencephalon; forms roof of the third ventricle Pineal gland extends from the posterior border and secretes melatonin Melatonin a hormone involved with sleep regulation, sleep-wake cycles, and mood Choroid plexus a structure that secretes cerebral spinal fluid (CSF)

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18 Cerebral Hemispheres Form the superior part of the brain and make up 83% of its mass Contain ridges (gyri) and shallow grooves (sulci) Contain deep grooves called fissures Are separated by the longitudinal fissure Have three basic regions: cortex, white matter, and basal nuclei

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20 Deep sulci divide the hemispheres into five lobes: Frontal, parietal, temporal, occipital, and insula Three fissure: 1.Central sulcus( sulcus of Roando) separates the frontal and parietal lobes 2. Parieto-occipital sulcus separates the parietal and occipital lobes 3. Lateral sulcus separates the parietal and temporal lobes

21 FRONTAL LOBE --PRECENTRAL SULCUS : is in front of & parallel to the central sulcus --precentral gyrus: between precentral and c entral sulcus; -- Superior & inferior frontal sulci : divide remaining front lobe into SUPERIOR, MIDDLE & INFERIOR.

22 PARIETAL LOBE --POSTCENTRAL SULCUS : is behind & parallel to central sulcus, bound the POSTCENTRAL GYRUS. --Interparietal sulcus extend from middle of the postcentral sulcus, divide into SUPERIOR & INFERIOR PARIETAL lobules. --inferior parietal lobule have SUPRAMARGINAL GYRUS & ANGULAR GYRUS, respectively

23 TEMPORAL LOBE: --superior & inferior temporal sulci divide the laeral surface of temporal lobe into SUPERIOR, MIDDLE & INFERIOR TEMPORAL GYRI.

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25 OCCIPITAL LOBE -Calcarine sulcus: continues for a short distance over the occipital pole & joins the parieto-occipital sulcus. The cortex on both sides of calcarine sulcus represents the striate cortex. CINGULATE gyrus: is seperated from the corpus callosum by the callosal sulcus.

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28 The cortex superficial gray matter; accounts for 40% of the mass of the brain Each hemisphere acts contralaterally (controls the opposite side of the body) The three types of functional areas are: Motor areas control voluntary movement Sensory areas conscious awareness of sensation Association areas integrate diverse information

29 MOTOR AREA: Located in the precentral gyrus Composed of pyramidal cells whose axons make up the corticospinal tracts Allows conscious control of precise, skilled, voluntary movements BRODMANN S 4, giant pyramidal dell of Betz present here.

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31 PREMOTOR AREA: Located anterior to the precentral gyrus Controls learned, repetitious, or patterned motor skills Brodmann;s area..6

32 SENSORY AREA: Located in the postcentral gyrus, this area: Receives information from the skin and skeletal muscles BRODMANN;S area..3,1.2 Associate sensory area Located posterior to the primary somatosensory cortex Integrates sensory information Forms comprehensive understanding of the stimulus Determines size, texture, and relationship of parts

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34 VISUAL AREA: Primary visual (striate) cortex Seen on the extreme posterior tip of the occipital lobe Most of it is buried in the calcarine sulcus Receives visual information from the retinas BROADMANN S AREA 17 Visual association area Surrounds the primary visual cortex Interprets visual stimuli (e.g., color, form, and movement)

35 ACOUSTIC AREA: Primary auditory cortex Located at the superior margin of the temporal lobe Receives information related to pitch, rhythm, and loudness BRODMANN AREA: 41, 42 Auditory association area Located posterior to the primary auditory cortex Stores memories of sounds and permits perception of sounds Wernicke s area: which is nearby Broca's area but in the temporal lobe, right next to the auditory cortex. This is were we understand the meaning of speech, and damage to this area will leave you with receptive aphasia, meaning that you will be unable to understand what is being said to you

36 Broca s area Located anterior to the inferior region of the premotor area Present in one hemisphere (usually the left) A motor speech area that directs muscles of the tongue Is active as one prepares to speak

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38 Fron tal Lobe Parie Parie Primary tal MotorPrimary Lobe Area Sensory Area Premotor leg Area trunk Sensory arm Association Higher Area Intellectual hand Functions Visual face Association tongue Area Speech Primary Language Motor Visual Comprehension Area Primary Area & Formation Auditory Area Memory The Cerebr al Cortex Temp oral Lobe Occipi tal Lobe

39 INTERNAL STRUCTURE BASAL GANGLIA : consists Corpus striatum Lentiform nucleus( putamen & globus pallidus) Caudate nucleus Claustrum Amygdaloid body Function Regulate voluntary movement Integrative or just a relay station? Pathology Movement disorders (e.g. Parkinson s) Neostriatum: caudate + putamen Paleostriatum: globus

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41 The limbic system has three functions: It mediates the sense of smell It mediates emotional behaviour It plays an important role in memory. Structures on medial and basal surfaces of cerebral hemispheres Cingulate gyrus + parahippocampal gyrus + hippocampal formation + fornix + amygdala + septum + mammillary bodies Limbic system include the amygdala, the hippocampus and the fornix Recall that the amygdala is for emotion regulation,and perception of odor Hippocampus and fornix are important for learning and memory

42 Cingulate gyrus Anterior nucleus of thalamus Thalamus Para-olfactory area Fornix Mamillary bodies of hypothalamus Hypothalamus Hippocampus Uncus Amygdala Para-hippocampal gyrus

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44 Three connective tissue membranes external to the CNS dura mater, arachnoid mater, and pia mater Functions: -Cover and protect the CNS -Protect blood vessels and enclose venous sinuses -Contain cerebrospinal fluid (CSF) -Form partitions within the skull

45 BLOOD SUPPLY OF BRAIN & SPINAL CORD Brain recive the blood from vertebral artery and internal carotid artery Vertebral Deep cervical Ascending cervical Transverse cervical Inf. thyroid Thyrocervical Suprascapular Subclavian

46 Blood supply to brain Brain is supplied by: Internal carotid Aa. Basilar A. (formed by fusion of vertebral Aa.) Together they contribute to the Circle of Willis that sends branches to supply cerebral hemispheres

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48 Venous Drainage Internal Jugular Brain External Jugular Scalp, face Vertebral cervical vertebrae, spinal cord, neck muscles Dural sinuses Veins in brain to Internal Jugular

49 Ventricles of the Brain Arise from expansion of the lumen of the neural tube The ventricles are: The paired C-shaped lateral ventricles The third ventricle found in the diencephalon The fourth ventricle found in the hindbrain dorsal to the pons

50 Ventricles of the Brain Figure 12.5

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52 Flow of CSF Choroid plexus Ventricles Subarachnoid space through lateral and median apertures of 4th ventricle Blood of dural sinuses via arachnoid villi

53 There are four cavities in the brain, called ventricles. The ventricles are filled with cerebrospinal fluid (CSF), which provides the following functions: Absorbs physical shocks to the brain Distributes nutritive materials to and removes wastes from nervous tissue Provides a chemically stable environment There are four ventricles: Each of two lateral ventricles occupies a cerebral hemisphere The third ventricle is connected by a passage (interventricular foramen) to each of the two lateral ventricles The fourth ventricle connects to the third ventricle (via the cerebral aqueduct) and to the central canal of the spinal cord (a narrow, central tube extending the length of the spinal cord). Additional openings in the fourth ventricle also allow CSF to flow into the subarachnoid space.

54 Blood-Brain Barrier (BBB) Selective Permeability: Substances that can pass include oxygen, glucose, carbon dioxide, alcohol, anesthetics & water Substances that can not pass include medications such as many antibiotics & systemic chemotherapy agents. Brain capillary endothelium less permeable, tightly joined Toxins cannot penetrate O2 & glucose pass through Lipid soluble substances pass

55 Major Functions 1. Sensory perception 2. Voluntary control of movement 3. Language 4. Personality traits 5. Sophisticated mental events, such as thinking memory, decision making, creativity, and self-consciousness 1. Inhibition of muscle tone 2. Coordination of slow, sustained movements 3. Suppression of useless patterns of movements 1. Relay station for all synaptic input 2. Crude awareness of sensation 3. Some degree of consciousness 4. Role in motor control 1. Regulation of many homeostatic functions, such as temperature control, thirst, urine output, and food intake 2. Important link between nervous and endocrine systems 3. Extensive involvement with emotion and basic behavioral patterns 1. Maintenance of balance 2. Enhancement of muscle tone 3. Coordination and planning of skilled voluntary muscle activity 1. Origin of majority of peripheral cranial nerves 2. Cardiovascular, repiratory, and digestive control centers 3. Regulation of muscle reflexes involved with equilibrium and posture 4. Reception and intergration of all synaptic input from spinal cord; arousal and activation of cerebral cortex 5. Role in sleep-wake cycle Brain component Cerebral cortex Basal nuclei Thalamus Hypothalamus Cerebellum Brain stem (midbrain, pons, and medulla)

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