Brain Anatomy Final Study Guide PDF

​ Cerebrum: largest portion of the brain → divided into “half brains” called the right and left hemispheres and 4 lobes: ○​ Frontal Lobe: function includes voluntary motor control, decision making, planning, concentration, and personality ○​ Parietal Lobe: function includes...

​ Cerebrum: largest portion of the brain → divided into “half brains” called the right and left hemispheres and 4 lobes: ○​ Frontal Lobe: function includes voluntary motor control, decision making, planning, concentration, and personality ○​ Parietal Lobe: function includes receiving afferent sensory information ○​ Temporal Lobe: function includes hearing and smell stimulus ○​ Occipital Lobe: function includes vision stimulus ​ Thalamus: The largest part, containing nuclei that receive sensory information (auditory and visual) and project to the cerebral cortex ○​ plays roles in motor function regulation, emotional responses, and mood development Hypothalamus: Found at the bottom of the diencephalon ​ it regulates homeostasis, emotional responses to odors, and connects to the pituitary gland via the infundibulum ​ It plays a crucial role in autonomic functions and maintains physiological processes ​ Brainstem: 1.​ Main parts: medulla oblongata, pons, midbrain 2.​ Key functions: relay station for signals, autonomic functions, coordination of reflexes 3.​ Medulla Oblongata: Located at the inferior portion ​ It serves as a relay station for ascending sensory and descending motor tracts ​ It contains nuclei for autonomic functions (respiratory, cardiac, vasomotor) and cranial nerves (trigeminal, facial, vestibulocochlear, glossopharyngeal, vagus, hypoglossal) 4.​ Pons: Positioned above the medulla ​ It connects different brain regions and relays information from the cerebrum to the cerebellum through pontine nuclei  ​ It contains ascending and descending tracts and nuclei for cranial nerves (trigeminal, abducens, facial, vestibulocochlear, glossopharyngeal) 5.​ Midbrain: Located superior to the pons ​ it serves as a pathway for nerve connections between the cerebral hemispheres and contains auditory (inferior colliculi) and visual (superior colliculi) centers ​ Cerebellum: located beneath the occipital lobe and connected to the brainstem via the pons 1.​ The cerebellum features a cortex made of gray matter, with deep cerebellar nuclei located in the inferior center of the white matter, known as the arbor vitae, which resembles a branching tree 2.​ Cerebellum consists of these three sections: 3.​ Flocculonodular Lobe: involved in balance and eye movement control 4.​ Vermis and Medial Portions of Lateral Hemispheres: Responsible for posture, locomotion, and fine motor coordination, facilitating smooth and coordinated movements 5.​ Lateral Hemispheres: Associated with the frontal lobe's cerebral cortex, playing a role in planning, practicing, and learning complex movements Structures that Protect the Brain - 1.​ Bones of the skull: ​ Frontal bone, parietal bone, temporal bone, occipital bone, sphenoid bone, ethmoid bone 1.​ Cranial meninges: ​ Meninges: specialized membranes that provide protection, physical stability, and shock absorption ​ Dura Mater: superficial layer, composed of two layers: - Meningeal (innermost) layer of the dura mater - Periosteal (outermost) layer of the dura mater - Between the two layers is the dural sinuses → the dural venous sinuses (superior sagittal sinus), which contains interstitial fluid and blood vessels, receiving blood from the brain (draining) and site where cerebrospinal fluid is thought to return to venous circulation via arachnoid granulations ​ Arachnoid Mater: Mid-layer, has web-like threads in the subarachnoid space that connect the arachnoid mater with the pia mater ​ Subarachnoid space filled with cerebrospinal fluid and cerebral vasculature ​ Pia Mater: Innermost membrane, highly vascularized and delicate 1.​ Cerebrospinal fluid ​ Cerebrospinal fluid: clear liquid with small amounts of proteins that circulate in the circumventricular organs and subarachnoid space ​ Function: prevents contact of neural tissue with surrounding bones, provides support for the brain, regulates ions and nutrients in the extracellular environment 1.​ Blood brain barrier ​ protects the brain by filtering out harmful substances while allowing essential nutrients through, maintaining a stable environment ​ Prevents many proteins, including toxins and viruses, from entering nervous tissue from circulatory system 1.​ Rich blood supply ​ ensures a constant flow of oxygen and nutrients while removing waste like carbon dioxide ​ The steady supply is crucial because the brain cannot store energy and needs continuous blood flow Function, Production, and Flow of Cerebrospinal Fluid - Function: ​ Protection: Cushions the brain and spinal cord, acting as a shock absorber to prevent injury. ​ Buoyancy: Reduces the effective weight of the brain, preventing compression of neural tissue. ​ Homeostasis: Maintains a stable environment by regulating ion balance and removing waste products. ​ Circulation: Transports nutrients, hormones, and waste between the blood and nervous tissue Production: ​ CSF circulates in the ventricular system composed on 4 ventricles: lateral ventricle (1st and 2nd), third ventricle, fourth ventricle ​ Choroid Plexus: ○​ Specialized capillary networks located in the ventricles (mainly in the lateral, third, and fourth ventricles). ○​ Ependymal cells form single-layered epithelium that secretes CSF ○​ Filters blood plasma and actively secretes CSF into the ventricles ​ Composition: ○​ Clear and colorless fluid. ○​ Contains water, glucose, ions (e.g., Na+, K+, Cl-), and minimal protein. ​ Daily Production: ○​ ~500 mL/day, with a constant volume of ~150 mL circulating at any given time (excess is absorbed) Flow:  ​ Lateral ventricles → Interventricular foramen → Third ventricle → Cerebral aqueduct → Fourth ventricle → Subarachnoid space → Arachnoid granulations → Bloodstream Blood-Brain Barrier - Function: Prevents many proteins, including toxins and viruses, from entering nervous tissue from circulatory system Structure: Endothelial cells have tight junctions Feet of astrocytes and pericytes support the tight junctions Thus, only certain substances (e.g., lipid-soluble substances & glucose) can diffuse through the BBB Similarities and Differences of Spinal and Cranial Meninges - ​ Both have 3 meningeal layers: ​ Dura Mater ​ However, within the cranium there are two layers: periosteal and meningeal layer which house special structures such as sural folds and venous sinuses for venous blood drainage, whereas the spinal meningeal has a single-layered structure forming a dural sac creating an epidural space ​ Arachnoid Mater ​ Pia Mater ​ Both function to protect the brain and spinal cord from mechanical stress, and to support the blood vessels and to form a continuous cavity through which the cerebrospinal fluid passes, nutrient delivery ​ Spinal meninges have an epidural space which is filled w/ cerebrospinal fluid and very few nerves whereas the cranial meninges has a potential space between dura mater and skull, tightly fused, making the epidural space normally absent Arterial Supply to Brain - Flow: Blood reaches brain via the common carotid arteries → internal carotid arteries → vertebral arteries → basilar artery → connected at the circle of Willis