بسم الله الرحمن الرحیم

Each Cerebral hemisphere is made from:  Cortex, a superficial gray mater  Centrum Semiovale, a deep massive neuronal processes, (white mater) Deep basal nuclei Lateral ventricle

Ventricular System L V L V 3rd 4th Lateral Ventricles Third Ventricle Cerebral Aqueduct Fourth Ventricle 4th Central Canal

Lateral Ventricle Body Horn Anterior Horn Posterior Horn Inferior Horn Parietal Lobe Frontal Lobe Occipital Lobe Temporal Lobe

Four Ventricles Lined by ependymal cells CSF filled chambers Communicating with central canal of spinal cord Lined by ependymal cells

Basal Nuclei - The term basal nuclei (basal ganglia) is applied to a collection of masses of gray matter situated within each cerebral hemisphere. They are the: corpus striatum the amygdaloid nucleus the claustrum The corpus striatum is situated lateral to the thalamus. It is almost completely divided by a band of nerve fibers, the internal capsule, into the caudate nucleus and the lentiform nucleus The caudate nucleus, a large C-shaped mass of gray matter that is closely related to the lateral ventricle, Iies lateral to the thalamus

Brain white mater 1. Commissural fibers: 2. Association fibers: Corpus callosum Fornix Anterior commisure Posterior commisure habenularc ommissure 2. Association fibers: Long association Short association fasciculus Superior long association fasciculus Inferior long association fascculus Uncinate (frontotemporal) fasciculus 3. Projection fibers Ascending Descending

Red: projection fibres Green: commissural fibres Blue: association fibres

Forceps major & minor & tapetum

The anterior commissure is a small bundle of nerve fibers that crosses the midline in the lamina terminalis When traced laterally a smaller or anterior bundle curves forward on each side toward the anterior perforated substance and the olfactory tract. A larger bundle curves posteriorly on each side and grooves the inferior surface of the lentiform nucleus to reach the temporal lobes'

Anterior commissure

The posterior commissure is a bundle of nerve fibers that crosses the midline immediately above the opening of the cerebral aqueduct into the third ventricle It is related to the inferior part of the stalk of the pineal gland Various collections of nerve cells are situated along its length. The destinationsand functional significance of many of the nerve fibers are not known However the fibers from the pretectal nuclei involved in the pupillary light reflex are believed to cross in this commissure on their way to the parasympathetic part of the oculomotor nuclei.

The fornix is composed of myelinated nerve fibers and constitutes the efferent system of the hippocampus that passes to the mammillary bodies of the hypothalamus The nerve fibers first form the alveus,which is a thin layer of white matter covering the ventricular surface of the hippocampus and then converge to form the fimbria. The fimbriae of the two sides increase in thickness and, on reaching the posterior end of the hippocampus, arch forward above the thalamus and below the corpus callosum to form the posterior columns of the fornix. The two columns then come together in the midline to form the body of the fornix The commissure of the fornix consists of transverse fibers that cross the midline from one column to another just before the formation of the body of the fornix The function of the commissure of the fornix is to connect the hippocampal formations of the two sides.

Figure 9-10: The diencephalon

The habenular commissure is a small bundle of nerve fibers that crosses the midline in the superior part of the root of the pineal stalk The commissure is associated with the habenular nuclei, which are situated on either side of the midline in this region The habenular nuclei receive many afferents from the amygdaloid nuclei and the hippocampus These afferent fibers pass to the habenular nuclei in the stria medullaris thalami Some of the fibers cross the midline to reach the contralateral nucleus through the habenular commissure The function of the habenular nuclei and its connections in humans is unknown

Association fibers

Commissural fibers

Projection

Function of cerebral cortex Cerebral Cortex is: the outer layer of the cerebrum that consists of gray matter which deals with conscious motor action, sensation, memory, communication, reasoning, emotions, intelligence.

Functions of Cerebral lobes Frontal Lobe ----- controls conscious muscle action, planning for movements, motor memory, voluntary eye movements. Parietal Lobe ----- Controls conscious interpretation of sensation from muscles, tongue and cutaneous areas. Temporal Lobe --- conscious interpretation of auditory and olfactory sensations. Memory of sounds and smells. Occipital Lobe ------- the most posterior lobe of the cerebrum which deals with conscious seeing, eye focus and integrating visual memory with other sensations.

Insula (Island of Reil) (‘fifth lobe’) Covered by parietal and temporal lobes, not visible from the outside within the lateral fissure It is a component of a functional lobe which is called limbic lobe Limbic lobe is related to emotional and autonomic response to external stimuli

Cerebral cortex Sensory Area of the Cerebral Cortex – Located in areas posterior to the central sulcus. Receives and interprets conscious sensory impulses. The postcentral gyrus of the parietal lobe is a key ridge of gray matter that allows a person to judge the source of sensory stimuli. Motor Area of the Cerebral Cortex --- Located in areas anterior to the central sulcus. Plans and initiates impulses for conscious motor movements. The precentral gyrus of the frontal lobe is an another key ridge of gray matter that allows a person to operate specific areas of the body. Association Area of Cerebral cortex

Cytoarchitecture of cerebral cortex

Cytoarchitecture of cerebral cortex

Cytoarchitecture of cerebral cortex

Cytoarchitecture of cerebral cortex

Cytostructure of cerebral cortex 1 – Molecular layer 2 – External granular layer 3 – External pyramidal layer 4 - Internal granular layer 5 – Internal pyramidal layer 6 – Multiform layer

Cytoarichitecture of cerebral cortex based on Brodmann divisioions Brodmann area Location Function 17 Banks of cal.sul Primary visual c 18, 19 Medial aspect of occipital lobe Secondary visual cortex 3,1,2 Postcentral gyr. primary somato. 4 Precentral gyr. Primary motor 6 Sup&middle f.g. Premotore cort. 44,45 Inf. front. gyirus Speech 41,42 Sup. tem .gyr. Auditory cortex

Function of Brain Structures Continued Sensory Area of the Cerebral Cortex Located in areas posterior to the central sulcus. Receives and interprets conscious sensory impulses. The postcentral gyrus of the parietal lobe is a key ridge of gray matter that allows a person to judge the source of sensory stimuli. Motor Area of the Cerebral Cortex Located in areas anterior to the central sulcus. Plans and initiates impulses for conscious motor movements. The precentral gyrus of the frontal lobe is a another key ridge of gray matter that allows a person to operate specific areas of the body.

Brain Structure Functions Continued Association Areas ----- Regions of the cerebral cortex that analyze, recognize and act on sensory input and communicate with the motor areas. Examples include the visual and auditory association areas.

Primary Motor Cortex

Somatic Sensory Cortex

6 1 4 8 Supramarginal 10 3 Angular 2 22 44 41 42 17 45

Important areas in frontal cortex Supplamentary cortex = medial surface of area 6 (area 24 in cingulate gyrus) Prefrontal cortex = predominanatly area 9, 45 & 46 Premotor area = area 6 (which is in front of area 4)

The localisation of language functions in the human brain

Speech Speech area normally in left cerebral cortex Wernicke’s area: Sensory speech Broca’s area: Motor speech Aphasia: Absent or defective speech or language comprehension 1) Broca’s aphasia (expressive aphasia, motor aphasia) 2) Wernicke’s aphasia (no comprehension & failure to convey meaning

How to speak in response to seeing a word or hearing it. Figure 9-23: Cerebral processing of spoken and visual language

Spinal tap

Brain Herniation Syndromes Herniation occurs when mass effect is severe enough to push intracranial structures from one compartment into another. The 3 most clinically important herniation syndromes are caused by heriation through the tentorial notch (transtentorial), centrally and downward (central), and under the falx cerebri (subfalcine)