Brain Anatomy PDF

# Brain - It is one of the largest organs in the body and coordinates most body activities. - It is the center for all thought, memory, judgment, and emotion. - Each part of the brain is responsible for controlling different body functions, such as temperature regulation and breathing. - The brain...

# Brain - It is one of the largest organs in the body and coordinates most body activities. - It is the center for all thought, memory, judgment, and emotion. - Each part of the brain is responsible for controlling different body functions, such as temperature regulation and breathing. - The brain is contained in skull and weighs 1300 - 1400 g. - Made up of about 1000 billion neurons, each neuron is surrounded by about 10 glial cells (neuroglia). - Neurons cannot multiply, and many neurons are lost every day in life but glial cells can multiply throughout the life. - Brain is also covered by "Meninges" like spinal cord - outer duramater, middle arachnoidmater & inner piamater # Ventricles of the brain - There are certain cavities in the brain called as "ventricles". - These ventricles are filled with CSF. - There are 4 ventricles of brain: - 2 lateral ventricles in two hemispheres of the brain. - 4th between brain stem & cerebellum and is continuous with the central cavity of spinal cord. - 3rd lies between hypothalamus & thalamus # Parts of brain: - **Cerebrum** - Right cerebral hemisphere - Left cerebral hemisphere - **Cerebellum** - **Brain stem** - (1) Medulla - (2) Pons - (3) Mid brain - **Diencephelon** - (1) Thalamus - (2) Hypothalamus - (3) Epithalamus & Pineal gland # (A) Cerebrum - It is the largest section of the brain. - It is located in the upper portion of the brain and is the area that processes thoughts, judgment, memory, problem solving, and language, imaginations. - *Cerebral cortex* - the superficial layer of the cerebrum is "gray mater", and this is 2-4 mm thick called "Cerebral cortex" containing billions neurons. - During embryonic development when the brain size increases rapidly, the gray mater of the cortex enlarges much faster than deeper white mater so as result, the cortical region roles and fold upon itself. - The folds are called "gyri" or "convolutions". - The deepest grooves between the folds are called "fissures". - The shallower grooves between folds are called "sulci". - The most prominent fissure, the longitudinal fissure, separates the cerebrum into right and left halves called "cerebral hemispheres". Each hemisphere has 4 lobes. - The cerebrum is subdivided into the left and right. Both hemispheres are connected by a bridge of nerve fibers that relay information between 2 hemispheres called "corpus callosum". # Lobes of Cerebrum - **Frontal Lobe** - Most anterior portion of the cerebrum (under forehead) "central sulcus" separate frontal and perital lobe. - Controls motor function, personality, and speech. - Like Center of reasoning, Planning, some parts of speech, movement, Emotions, problem solving. - Also called as "motor cortex". - **Parietal lobe** - The most superior portion of the cerebrum (top of head). - Receives and interprets nerve impulses from sensory receptors and interprets language. - Receives sensory input from the skin. (touch, pressure, temperature, & pain). - Also called as "sensory cortex". - **(3) Occipital lobe** - The most posterior portion of the cerebrum (back of the head). - Receives input from the eyes and controls vision. - Also called as "visual cortex". - **4. Temporal lobe** - The left and right lateral portion of the cerebrum (on the sides of your head above your ears). - Controls hearing and smell. - Also called "Auditory cortex". ## Functions of cerebrum: - (1) Motor functions like control of voluntary movements. - (2) Sensory functions like perception of pain, temparature, touch, hearing, taste, & smell. - (3) Control of intelligence, speech, memory & learning etc. # (B) Cerebellum - Second largest portion of the brain. - Located beneath the posterior part of the cerebrum. - A deep groove known as "transverse fissure" separates cerebrum to cerebellum. - Aids in coordinating voluntary body movements and maintaining balance and equilibrium. ## External Structure - The external surface, called cerebellar cortex, look like butterfly, constricted area called "vermis". - The lateral wings or lobes called cerebellar hemisphere that is interconnected by a narrow portion called vermis. - Each hemisphere consists of lobes separated by deep fissures. ## Divisions & layers of cerebellum - (1) Anterior lobe - (2) Posterior lobe - (3) Flocculonodular lobe - on the inferior surface maintains equilibrium and balance - Superficial layer of cerebellum called "cerebellar cortex" consist of gray mater, series of slender & parallel folds called "folia". - Deep to gray mater white mater called "arbor vitae" resemble to branch of tree. - Even deeper white mater are "cerebellar nuclei", region of the gray mater having axons carrying impulses from cerebellum to other parts of brain. ## Functions of cerebellum: - (1) Coordinate contractions of skeletal muscles. - (2) Regulate posture and balance. - (3) May play a role in cognition/learning from experiences and language processing. # (C) Brain Stem - Consists of: - (1) Midbrain - (2) Pons - (3) Medulla oblongata - Superiorly continuous with Diencephalon. - Inferiorly continuous with spinal cord. - Posteriorly pons and medulla is separated by fourth ventricle. - Midbrain, pons and medulla connected to cerebellum by superior, middle and inferior cerebellar peduncle resp. ## (1) Mid brain - The midbrain or mesencephalon extends from the pons to the diencephalon and about 2.5 cm long. - It acts as a pathway for impulses to be conducted between the brain and the spinal cord. - Associated with vision, hearing, motor control, sleep/wake, arousal (alertness), and temperature regulation. - Screening of information before it reaches high brain structure. ## Functions of mid brain: - The midbrain serves important functions in motor movement, particularly movements of the eye, and in auditory and visual processing. - Dopamine produced in the substantia nigra and ventral tegmental area plays a role in excitation, motivation. - The midbrain helps to relay information for vision and hearing. ## (2) Pons: - Means bridge - connects the cerebellum to the rest of the brain. - Lies between midbrain above and medulla below in front of cerebellum. - Like medulla it also sensory tract and motor tract. - Contains nuclei that deals with respiration, swallowing, bladder control, hearing, equilibrium, eyeball movements, facial expressions etc. ## (3) Medulla oblongata - Lowermost part of the brain stem and continuation of the superior portion of spinal cord. - Situated at the base of the skull/starts from foramen magnum and extends to the inferior border of the pons, a distance of about 3 cm. - The ascending and descending sensory and motor white mater tracts (nerves) connecting brain to spinal cord pass through medulla oblongata. - Its very important because many "regulatory centers" are located here. - (1) The cardiovascular center: regulates the heart rate, force of heartbeat and diameter of blood vessels. - (2) The medullary rhythmicity center: responsible for maintaining basic rhythm of breathing. - (3) The vasomotor center: regulates blood pressure. - (4) Others: vomiting, swallowing, cough, hiccupping & sneezing etc. - 5 pairs of cranial nerves originates from the nuclei located in medulla oblongata. # (D) Diencephelon - Hypothalamus - Thalamus - Epithalamus ## What is diencephalon? - Posterior part of the forebrain that connects the midbrain with the cerebral hemispheres. - Encloses the third ventricle. ## (1) Thalamus - Contain mass of nerve cells. - Thalamus means "inner room" in Greek, as it sits deep in the brain at the top of the brainstem. - The thalamus is called the gateway to the cerebral cortex, as nearly all sensory inputs pass through it to the higher levels of the brain. - It makes up 80% of diencephalon. - Important relay station for all Incoming sensory nerves from periphery/spinal Cord with different impulses of pain, temperature, Touch, pressure are conveyed to thalamus first than Go to cerebrum. - This information is relayed from thalamus to cerebrum through thalamic nuclei: - (1) Median geniculate nucleus - related to hearing - (2) Lateral geniculate nucleus- related to vision - (3) Ventral posterior nucleus - related to taste & somatic sensations like touch, pain, pressure, cold, heat, vibrations etc. ## (2) Hypothalamus: - The hypothalamus sits under the thalamus at the top of the brainstem. Although the hypothalamus is small, it controls many critical bodily functions: - Controls autonomic nervous system. - Center for emotional response and behavior. - Regulates body temperature. - Regulates food intake (appetite). - Regulates water balance and thirst. - Controls sleep-wake cycles. - Controls endocrine system. - Controls CVS regulation - Heart rate and BP. ## (3) Epithalamus and Pineal gland: - Epithalamus is a small region superior and posterior to the thalamus. - It consists of pineal gland. - Pineal gland is about the size of the pea and protrudes from posterior midline of the 3rd ventricle. - It's an endocrine gland secrets hormone "Melatonin". - Darkness stimulates the pineal gland to secrets melatonin - it promotes sleepiness. # The cranial nerves: - The 12 pairs of cranial nerves named because they pass through bones of cranium and arise from the brain inside the cranial cavity. - These nerves may be sensory (carrying impulse to the brain), motor (carrying impulse from the brain to periphery) or mixed (containing both sensory and motor fibers) # Cranial nerves | Number | Name | Function | |:--------|:--------------|:-------------------| | I | Olfactory | Smell | | II | Optic | Sight | | III | Oculomotor | Moves eye, pupil | | IV | Trochlear | Moves eye | | V | Trigeminal | Face sensation | | VI | Abducens | Moves eye | | VII | Facial | Moves face, salivate | | VIII | Vestibulocochlear | Hearing, balance | | IX | Glossopharyngeal | Taste, swallow | | X | Vagus | Heart rate, digestion | | XI | Accessory | Moves head | | XII | Hypoglossal | Moves tongue | # Thank you