Central Nervous System

Central Nervous System (CNS) ● The CNS forms from the embryonic neural tube ○ the tube develops into the brain and spinal cord ○ its opening turns into ventricles, which are four brain chambers filled with cerebrospinal fluid Protection of the CNS ● ● ● Scalp and skin Cranial bones Meninges ○ Pia, arachnoid, and dura mater ○ cranial dura mater is composed of 2 layers ● Cerebrospinal fluid Meninges ● Dura Mater ○ Double-layered external covering ■ Periosteum - attached to surface of the skull ■ Meningeal Layer - outer covering of the brain ○ Folds inward in several areas ● Arachnoid Layer ○ Middle layer ○ Web-like ● Pia Mater ○ Internal layer ○ Clings to the surface of the brain Blood-Brain Barrier (BBB) ● The BBB shields brain cells from harmful substances and pathogens by blocking many materials from entering the brain. ○ It can also stop therapeutic drugs from passing through. ○ Brain injuries might damage the BBB, allowing restricted substances to enter brain tissue. Blood Flow to the Brain ● Blood flows to the brain via the vertebral and carotid arteries and flows back to the heart via the jugular veins. Cerebrospinal Fluid (CSF) ● ● ● ● Like blood plasma in composition Made by the choroid plexus Acts as a cushion to protect the brain Flows through the arachnoid space, ventricles, and spinal cord’s central canal. Ventricles and the Choroid Plexus ● ● The ventricles of the brain contain CSF The choroid plexuses make CSF Regions of the Brain 1. Cerebral Hemispheres (cerebrum) ● Paired (left and right) upper parts of the brain ● ● Make up more than half of the brain’s mass The surface has ridges (gyri) and grooves (sulci) ● Largest part; consist of two hemispheres connected by the corpus callosum ● Controls higher brain functions; interprets sensory impulses, initiates muscular movements, stores memories, handles reasoning, develops intelligence. A. Lobes of the Cerebrum ● Fissures (deep grooves) divide the cerebrum into lobes ● Surface lobes of the cerebrum ○ Frontal Lobe ○ Parietal Lobe ○ Occipital Lobe ○ Temporal Lobe B. Specialized Areas of the Cerebrum ● The limbic system is found in the cerebral hemispheres and diencephalon ○ Somatic Sensory Area - receives impulses from the body’s sensory receptors ○ Primary Motor Area - sends impulses to skeletal muscles ○ Broca’s Area - involved in our ability to speak C. Layers of the Cerebrum ● Gray Matter ○ Outer layer ○ Composed mostly of neuron cell bodies ● White Matter ○ Beneath cerebral cortex ○ Fiber tracts inside the gray matter ○ Example: corpus callosum connects hemispheres ■ commissural fiber ● Basal Nuclei - clusters of gray matter inside the brain ○ Relays motor impulses from the cerebral cortex, passing into brain stem and spinal cord; assists in coordination of voluntary movements ● Helps control voluntary movements by adjusting signals sent to the motor cortex ● Issues can cause muscle problems like spasms or jerky movements ● Linked to diseases like Huntington’s and Parkinson’s ● Aphasia - (a=without; -phasia=speech) inability to use or comprehend words. ● Nonfluent Aphasia - Inability to properly articulate or from words. Caused by the damage in the Broca’s speech area. ● Fluent Aphasia - Characterized by faulty understanding of spoken or written words. Caused by the damage to Wernicke’s area, the common integrative or auditory association area. 2. ■ ■ ■ ■ Diencephalon ● ● ● Sits on top of the brain stem Enclosed by the cerebral hemispheres Masses of gray matter (thalamus hypothalamus) and ○ A. Made of three parts: ● • Hypothalamus ○ helps maintain homeostasis ○ below thalamus ○ key part of the limbic system (handles emotions) ○ connected to the pituitary gland ○ plays a major roles in the autonomic nervous system ○ regulates body temperature, water balance, and metabolism ○ regulates hormonal output of anterior pituitary gland and acts as an endocrine organ (producing ADH and oxytocin) • 3. Thalamus ○ Located around the third ventricle ○ Main relay center for sensory signals going to the cerebral cortex, except for smell ○ Sends signals to the correct part of the cerebral cortex for processing and understanding Epithalamus ○ makes up the roof of the third ventricle ○ contains the pineal gland (part of the endocrine system) ○ has the choroid plexus, which produces cerebrospinal fluid ○ Habenular Nuclei emotional responses to odors Brain Stem ● Attaches to the spinal cord A. Parts of the brain stem: ● Midbrain ○ ○ ○ ○ ● Pons ○ ○ ○ ○ ● mostly composed of tracts of nerve fibers reflex centers for vision and hearing cerebral aqueduct - 3rd-4th ventricles contains nuclei of cranial nerves III, IV the bulging center part of the brain stem mostly composed of fiber tracts includes nuclei involved in the control of breathing contains nuclei of cranial nerves V, VI, VII, VIII Medulla Oblongata ○ ○ ○ ○ the lowest part of the brain stem merges into the spinal cord includes important fiber tracts contains important control centers: ■ heart rate control 4. blood pressure regulation breathing swallowing vomiting contains nuclei of cranial nerves IX, X, XI, XII. Cerebellum ● ● ● ● ● ● Two hemispheres with bumpy surfaces large tissue mass, inferior to cerebrum, posterior to brain stem connected by the vermis communicates with rest of CNS via tracts; integrates sensory information about body part positions; coordinates muscles activities; maintain posture helps with automatic coordination of body movements ○ checks how well motor actions from the cerebrum are performed ○ maintains posture and balance Ataxia - (a=without; -taxia=order) inability to coordinate muscular movements caused by the damage in the cerebellum