The purpose of the bony skull is to protect the brain from injury. The skull is formed from 8 bones that fuse together along suture lines. These bones include the frontal, parietal (2), temporal (2), sphenoid, occipital and ethmoid (Fig. 1). The face is formed from 14 paired bones including the maxilla , zygoma, nasal, palatine, lacrimal, inferior nasal conchae, mandible, and vomer. Inside the skull are three distinct areas: anterior fossa, middle fossa, and posterior fossa (Fig. 2). Doctors sometimes refer to a tumor’s location by these terms, e.g., middle fossameningioma.
Model of Human brain
Model of Human brain
The brain requires a rich blood supply, and the space between the skull and the cerebrum contains many blood vessels. These blood vessels can be rupted during trauma, resulting in bleeding.
Cerebrum -The largest division of the brain. It is divided into two hemispheres, each of which is divided into four lobes.The cerebrum is the control centre of the brain, the largest and the most prominent part of human brain is cerebrum.7The cerebrum is the largest part of the brain and is composed of right and left hemispheres. It performs higher functions like interpreting touch, vision and hearing, as well as speech, reasoning, emotions, learning, and fine control of movement.The cerebellum is located under the cerebrum. Its function is to coordinate muscle movements, maintain posture, and balance.The brainstem includes the midbrain, pons, and medulla. It acts as a relay center connecting the cerebrum and cerebellum to the spinal cord. It performs many automatic functions such as breathing, heart rate, body temperature, wake and sleep cycles, digestion, sneezing, coughing, vomiting, and swallowing. Ten of the twelve cranial nerves originate in the brainstem.
The inner most layer which covers and is bound to the surface of the brain is called PIA Matter. It is a fibrous layer made up of many blood vessels, which carry food and oxygen to the brain. The outer layer is called dura matter and is composed of thick connective tissue. The arachnoid is the thin elastic web like layer between the PIA matter and the arachnoid is a space filled with CEREBROSPINAL FLUID. Cerebrospinal fluid seperates the middle and inner meninges and fills 4 interconnected ventricles or cavities in the brain, with in the ventricle cerebrospinal fluid act as a transport medium for substances that are important to brain function. The cerebrospinal fluid is a clear liquid that protects the brain from mechanical injury by acting as a shock absorber. In order for the brain to perform its functions, it must have a constant supply of food and oxygen. If the oxygen supply to the brain is cut off even for a few minutes, the brain will usually suffer enormous damage. Such damage may result in death.
The nodular white excresences seen here over the cerebral hemispheres at the vertex on both sides of the central fissure with falxcerebri of the brain are the arachnoid granulations. This is where the cerebrospinal fluid produced in the choroid plexuses of the ventricles and which has circulated out of the foramina of Magendie and Luschka and into the subarachnoid space is reabsorbed. http://library.med.utah.edu/WebPath/HISTHTML/NEURANAT/CNS206A.html
Cerebral Cortex - The outermost layer of gray matter making up the superficial aspect of the cerebrum.
The cerbrums surface-the neocortex is convoluted into hundreads of folds
The largest portion of the brain is the cerebrum. It consist of two hemesphere that are connected together at the corpus callosum.
In a normal brain there are four fluid filled spaces called ventricles (Figure 1)There are two large ventricles (lateral ventricles) located on either side of the brainTwo other ventricles (the third and fourth ventricles) are placed along the midlineWithin the ventricles are tufts of vascular tissue called the choroid plexus. As blood flows through the choroid plexus it distills a clear watery fluid (plasma – Choriod Plexus epithelial cells actively transport sodium, chloride and bicarbonate ions into the ventricles and water follows the resulting osmotic gradient.) into the ventricles called cerebrospinal fluid, or CSFCSF flows from the ventricles towards the surface of the brain and returns to the blood (Figure 2)From the lateral ventricles the CSF flows into the centrally placed third ventricle and then through a narrow channel called the aqueduct, into the fourth ventricleCSF then flows over the surface of the brain in the subarachnoid space, an area between the brain and the membrane (dura) lining the inside of the skull The CSF then returns to the blood by passing into the large veins that drain the brain called sinuses
Gyri – Elevated ridges “winding” around the brain.Sulci – Small grooves dividing the gyriCentral Sulcus – Divides the Frontal Lobe from the Parietal LobeFissures – Deep grooves, generally dividing large regions/lobes of the brainLongitudinal Fissure – Divides the two Cerebral HemispheresTransverse Fissure – Separates the Cerebrum from the CerebellumSylvian/Lateral Fissure – Divides the Temporal Lobe from the Frontal and Parietal Lobes
* Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.The right and left hemispheres of the brain are joined by a bundle of fibers called the corpus callosum that delivers messages from one side to the other. Each hemisphere controls the opposite side of the body. If a brain tumor is located on the right side of the brain, your left arm or leg may be weak or paralyzed. Not all functions of the hemispheres are shared. In general, the left hemisphere controls speech, comprehension, arithmetic, and writing. The right hemisphere controls creativity, spatial ability, artistic, and musical skills. The left hemisphere is dominant in hand use and language in about 92% of people.
The Frontal Lobe of the brain is located deep to the Frontal Bone of the skull.It plays an integral role in the following functions/actions:- Memory FormationEmotionsDecision Making/Reasoning Personality
LanguageIn general, the left hemisphere of the brain is responsible for language and speech and is called the "dominant" hemisphere. The right hemisphere plays a large part in interpreting visual information and spatial processing. In about one third of individuals who are left-handed, speech function may be located on the right side of the brain. Left-handed individuals may need special testing to determine if their speech center is on the left or right side prior to any surgery in that area. Aphasia is a disturbance of language affecting production, comprehension, reading or writing, due to brain injury – most commonly from stroke or trauma. The type of aphasia depends on the brain area affected.Broca’s area lies in the left frontal lobe (Fig 3). If this area is damaged, one may have difficulty moving the tongue or facial muscles to produce the sounds of speech. The individual can still read and understand spoken language but has difficulty in speaking and writing (i.e. forming letters and words, doesn't write within lines) – called Broca's aphasia. Wernicke's area lies in the left temporal lobe (Fig 3). Damage to this area causes Wernicke's aphasia. The individual may speak in long sentences that have no meaning, add unnecessary words, and even create new words. They can make speech sounds, however they have difficulty understanding speech and are therefore unaware of their mistakes.
According to this model, when you hear a word spoken, this auditory signal is processed first in your brain’s primary auditory cortex, which then sends it on to the neighbouringWernicke’s area. Wernicke’s area associates the structure of this signal with the representation of a word stored in your memory, thus enabling you to retrieve the meaning of the particular word. In contrast, when you read a word out loud, the information is perceived first by your visual cortex, which then transfers it to the angular gyrus, from which it is sent on to Wernicke’s area. Whether you hear someone else speak a word or you read the word yourself, it is the mental lexicon in Wernicke’s area that recognizes this word and correctly interprets it according to the context. For you then to pronounce this word yourself, this information must be transmitted via the arcuate fasciculus to a destination in Broca’s area, which plans the pronunciation process. Lastly, this information is routed to the motor cortex, which controls the muscles that you use to pronounce the word.
Arcuate Fasciculus - A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech. Damage may result in:Conduction Aphasia - Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech.
Parietal lobeInterprets language, words Sense of touch, pain, temperature (sensory strip) Interprets signals from vision, hearing, motor, sensory and memorySpatial and visual perception
Primary Visual Cortex – This is the primary area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc.Visual Association Area – Interprets information acquired through the primary visual cortex.
They play an integral role in the following functions:HearingOrganization/Comprehensionof languageInformation Retrieval (Memory and Memory Formation)
Cortical RegionsPrimary Auditory Cortex – Responsible for hearingPrimary Olfactory Cortex – Interprets the sense of smell once it reaches the cortex via the olfactory bulbs. (Not visible on the superficial cortex)Wernicke’s Area – Language comprehension. Located on the Left Temporal Lobe.Wernicke’s Aphasia – Language comprehension is inhibited. Words and sentences are not clearly understood, and sentence formation may be inhibited or non-sensical.Temporal lobeUnderstanding language (Wernicke’s area) MemoryHearing Sequencing and organization
The central core is found in all vertebrates. Its 5 main regions help regulate basic life processes, including breathing, pulse, arousal, movement, balance, sleep, and early stage of processing sensory information.
Thalamus begins the process of sensory information. It determines fundamental properties, such as whether something is good or bad and then forwards the information to the appropriate area of the cerebral cortex where information processing continues.
Pons triggers dreaming and wakening from sleep.
It coordinates body movements, controls posture and maintains equilibruim
The reticular formation signals the cerebral cortex to attend the new simulation and to remain alert even during sleep.
Medulla is the centre for breathing, walking, sleeping and beating of the heart.
The limbic system exists only in mammals. Its regions mediate motivated behavior and emotional states and memory processes. The limbic system also regulates body temperature, blood pressure, blood sugar level and other house keeping activities.
Plays an important role in emotion, learning and memory.
Role in aggression, eating, drinking and sexual behaviors
Monitors blood levels of glucose, salt, blood pressure and hormones. It also helps to regulate processes in the body through its connection to the central and autonomic nervous systems and endocrine systems.
Cranial nervesThe brain communicates with the body through the spinal cord and twelve pairs of cranial nerves (Fig. 6). Ten of the twelve pairs of cranial nerves that control hearing, eye movement, facial sensations, taste, swallowing and movement of the face, neck, shoulder and tongue muscles originate in the brainstem. The cranial nerves for smell and vision originate in the cerebrum.
MemoryMemory is a complex process that includes three phases: encoding (deciding what information is important), storing, and recalling. Different areas of the brain are involved in memory depending on the type of memory.Short-term memory, also called working memory, occurs in the prefrontal cortex. It stores information for about one minute and its capacity is limited to about 7 items. For example, it enables you to dial a phone number someone just told you. It also intervenes during reading, to memorize the sentence you have just read, so that the next one makes sense.Long-term memory is processed in the hippocampus of the temporal lobe and is activated when you want to memorize something for a longer time. This memory has unlimited content and duration capacity. It contains personal memories as well as facts and figures.Skill memory is processed in the cerebellum, which relays information to the basal ganglia. It stores automatic learned memories like tying a shoe, playing an instrument, or riding a bike.
Left Olfactory - Optic Chiasm - Right Oculomotor - Left Oculomotor - Right Trochlear - Left Trochlear - Right Trigeminal - Left Trigeminal - Right Abducens - Left Abducens - Right Facial - Left Facial - Right Acoustic - Left Acoustic - Right Glossopharyngeal & Vagus - Left Glossopharyngeal & Vagus - Right Hypoglossal -
There are many sizes and shapes of neurons, but all consist of a cell body, dendrites and an axon. The neuron conveys information through electrical and chemical signals. Try to picture electrical wiring in your home. An electrical circuit is made up of numerous wires connected in such a way that when a light switch is turned on, a light bulb will beam. A neuron that is excited will transmit its energy to neurons within its vicinity.Neurons transmit their energy, or “talk”, to each other across a tiny gap called a synapse (Fig. 11). A neuron has many arms called dendrites, which act like antennae picking up messages from other nerve cells. These messages are passed to the cell body, which determines if the message should be passed along. Important messages are passed to the end of the axon where sacs containing neurotransmitters open into the synapse. The neurotransmitter molecules cross the synapse and fit into special receptors on the receiving nerve cell, which stimulates that cell to pass on the message. Glia cellsGlia (Greek word meaning glue) are the cells of the brain that provide neurons with nourishment, protection, and structural support. There are about 10 to 50 times more glia than nerve cells and are the most common type of cells involved in brain tumors. Astroglia or astrocytes transport nutrients to neurons, hold neurons in place, digest parts of dead neurons, and regulate the blood brain barrier.Oligodendroglia cells provide insulation (myelin) to neurons.Ependymal cells line the ventricles and secrete cerebrospinal fluid (CSF).Microglia digest dead neurons and pathogens.
Human Brain Cerebrum ( touch, vision, hearing, speech, reasoning, emotions, learning & fine control movements) Cerebellum (Co-ordinate muscle Brain Stem (relay center movements, maintain connecting the cerebrum and cerebellum to posture, and balance.) the spinal cord. breathing, heart rate, body temperature, wake and sleep cycles,digestion, sneezing, coughing, vomiting, and 7 swallowing )
Parietal Lobe:Assist in sensory processes, Spatial interpretation, attention and languagecomprehension. Interprets language, words, Sense of touch, pain, temperature,Interprets signals from vision, hearing, motor, sensory and memory. 35
Occipital LobeThe Occipital Lobe of the Brainis located deep to the OccipitalBone of the Skull. Its primaryfunction is the processing,integration, interpretation, etc ofVISION and visual stimuli.Interprets vision (color, light, movement) 37
Occipital lobe Visual Association Area Interprets information acquired through the primary visual cortex. Primary Visual Cortex size, color, light, motion, dimensions 38
Cerebellum The cerebellum is involved in the coordination of voluntary motor movement, balance and equilibrium and muscle tone. Damage to the cerebellum can lead to: loss of coordination of motor movement, the inability to judge distance , the inability to perform rapid alternating movements, movement tremors , tendency toward falling, weak muscles, slurred speech & abnormal eye movements. 45
Cranial Nerves:Left Olfactory - Optic Chiasm - Right Oculomotor (pupi)- Left Oculomotor - Right Trochlear (eye)- Left Trochlear -Right Trigeminal(face sensation) - Left Trigeminal - Right Abducens (eye) - Left Abducens - Right Facial - Left Facial - Right Acoustic - LeftAcoustic - Right Glossopharyngeal & Vagus (taste,swallow, HR, digetion)- Left Glossopharyngeal & Vagus - Right Hypoglossal (tongue) 65