Chapter 3 Central Nervous System (CNS) PDF

# Chapter 3 Central Nervous System (CNS) * CNS develops from the embryonic neural tube * The neural tube becomes the brain and spinal cord * The opening of the neural tube becomes the ventricles * Four chambers within the brain * Filled with cerebrospinal fluid ## Regions of th...

# Chapter 3 Central Nervous System (CNS) * CNS develops from the embryonic neural tube * The neural tube becomes the brain and spinal cord * The opening of the neural tube becomes the ventricles * Four chambers within the brain * Filled with cerebrospinal fluid ## Regions of the Brain * **Cerebral hemispheres** * Cerebrum * Diencephalon * Brain stem * Midbrain * Pons * Medulla oblongata * Cerebellum * Brain stem ### Cerebral Hemispheres (Cerebrum) * Paired (left and right) superior parts of the brain * Include more than half of the brain mass ### Cerebrum * The surface is made of ridges (gyri) and grooves (sulci). * Fissures (deep grooves) divide the cerebrum into lobes. * Surface lobes of the cerebrum * Frontal lobe * Parietal lobe * Occipital lobe * Temporal lobe ### Specialized Areas of the Cerebrum * 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 **Figure 8.** Components of the Wernicke-Geschwind model. ### Sensory and Motor Areas of the Cerebral Cortex: * Cerebral areas involved in special senses * Gustatory area (taste) * Visual area * Auditory area * Olfactory area ### Interpretation Areas of the Cerebrum * Speech/language region * Language comprehension region * General interpretation area ### Motor Areas of the Cerebrum For movement of head, arms, elbow, wrist, hands, fingers, thumb, neck, face, lips, jaws, tongue, pharynx, esophagus, small and large intestine, Hip, trunk and Legs. ### Layers of the Cerebrum * **Gray matter** * Outer layer * Composed mostly of neuron cell bodies * **White matter** * Fiber tracts inside the gray matter * Example: corpus callosum connects hemispheres * Basal nuclei - internal islands of gray matter * Regulates voluntary motor activities by modifying info sent to the motor cortex * Problems = ie unable to control muscles, spastic, jerky * Involved in Huntington's and Parkinson's Disease ### Diencephalon * Sits on top of the brain stem * Enclosed by the cerebral heispheres * Made of three parts * **Thalamus** * Surrounds the third ventricle. * The relay station for sensory impulses. * Transfers impulses to the correct part of the cortex for localization and interpretation. * **Hypothalamus** * Under the thalamus. * Important autonomic nervous system center * Helps regulate body temperature. * Controls water balance. * Regulates metabolism. * Neural control for pituitary gland for feedback control of hormonal secretion (hormonal control) through its releasing factors or releasing hormones. * An important part of the limbic system (emotions). * The pituitary gland is attached to the hypothalamus. **Figure 7.** The Diencephalon. * **Epithalamus** * Forms the roof of the third ventricle. * Houses the pineal body (an endocrine gland). * Includes the choroid plexus – forms cerebrospinal fluid. ### Brain Stem * Attaches to the spinal cord. * Parts of the brain stem * **Midbrain** * Mostly composed of tracts of nerve fibers. * Reflex centers for vision and hearing. * **Pons** * Cerebral aquaduct - 3rd-4th ventricles * The bulging center part of the brain stem * Mostly composed of fiber tracts * Includes nuclei involved in the control of breathing * **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 * Blood pressure regulation * Breathing * Swallowing * Vomiting * **Cerebellum** * Two hemispheres with convoluted surfaces. * Provides involuntary coordination of body movements. * Important for body balance **Figure 9.** The Brain Stem. ### Protection of the Central Nervous System * Scalp and skin * Skull and vertebral column * Meninges * Cerebrospinal fluid * Blood brain barrier **Figure 10.** Protection of the Central Nervous System. ### 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 **Figure 11.** * **Arachnoid layer** * Middle layer * Web-like * **Pia mater** * Internal layer * Clings to the surface of the brain ### Cerebrospinal Fluid * Similar to blood plasma composition * Formed by the choroid plexus * Forms a watery cushion to protect the brain * Circulated in arachnoid space, ventricles, and central canal of the spinal cord ### Ventricles and Location of the Cerebrospinal Fluid **Figure 11.** ### Blood Brain Barrier * Includes the least permeable capillaries of the body * Excludes many potentially harmful substances * Useless against some substances * Fats and fat soluble molecules * Respiratory gases * Alcohol * Nicotine * Anesthesia ### Cerebrum ### Lobes of the brain | The lobe | Site | Function | |---|---|---| | The Frontal lobes | In the front of the brain | 1 - Responsible for voluntary movements<br> 2 - Participate in execution of sequential task; speech output, skills, behavior, mood and memory. | | The Parietal lobes | Behind the frontal lobes and in front of occipital lobes. | 1 - They process sensory information such as temperature, pain, taste and touch. <br>2- Processing information about numbers. <br> 3- Awarenesss of the person to the position of his body parts, the space around him and his relationship to this space. | | The Temporal lobes | On each side of the brain | They process memory and auditory information and speech and language | | The Occipital lobes | At the back of the brain | They receive and process visual information. | | The Base Of The Brain: | | | | The structure | site | Function | | The cerebellum | At the base of the brain to the back. The cerebellum is the part of the brain that is located posterior to the medulla oblongata and pons | 1 - It controls equilibrium, posture and coordination. It receives information from our eyes, ears, muscles, and joints about what position our body is currently in (proprioception).<br> 2 - It contributes to generation of muscle tone. It coordinates skeletal muscles to produce smooth, graceful motions. <br> 3 - It is participating in some types of memory. It has some emotional role. <br> 4 - It exerts a complex influence on musical and mathematical skills. | | The brain stem: | | | | The sturcture | Site | Function | | The midbrain | Below the hypothalamus | Some cranial nerves that are responsible for eye muscle and hearing control exit the midbrain. | | The pons | A bridge between the midbrain and the medulla oblongata | 1 - Contains the nuclei and fibers of nerves that control eye muscle, facial muscle strength.<br> 2 - The pons houses the control centers for respiration and inhibitory functions | | The medulla Oblongata | The lowest part of the brain stem and is interconnected with the cervical spinal cord. | 1 - Helps control of involuntary actions including vital processes such as heart rate, blood pressure and respiration, digestion,......etc. <br> 2 - It carries the corticospinal tract which has motor function toward the spinal cord. | ### The Limbic System and Higher Mental Functions The Limbic System is a complex set of structures found just beneath the cerebrum and on both sides of the thalamus. It combines higher mental functions, and primitive emotion, into one system. It is often referred to as the emotional nervous system. It is not only responsible for our emotional lives, but also our higher mental functions, such as learning and formation of memories. The Limbic system explains why some things seem so pleasurable to us, such as eating and why some medical conditions are caused by mental stress, such as high blood pressure. There are two significant structures within the limbic system and several smaller structures that are important as well. **Figure 16.** The Limbic System. ### Structures of limbic system | The structure | The site | The function | |---|---|---| | The Thalamus | Lower central part of the brain medial to the basal ganglia | 1 - It integrates and relays sensory information. <br> 2 - It has a role in motor and memory control | | The Hypothalamus | Below the thalamus | 1 - It regulates automatic functions such as appetite, thirst and body temperature. <br> 2 - It secretes hormones that stimulate or suppress the release of other hormones (Neural control for hormonal secretion "feedback control") | | The Pituitary gland | At the base of the brain | 1 - It produces hormones that control many functions of other endocrine glands | | The Ventricles | In the interior of the cerebral hemispheres | It contains cerebrospinal fluid | | The Hippocampus | In the temporal lobe | It participates in memory and emotions | ### 1 - The amygdala (in the temporal lobe) responsible for feelings. The amygdala play an important role on the mediation and control of such activities and feelings as love, friendship, affection, and expression of mood. The amygdala is the center for identification of danger and is fundamental for self preservation. The amygdala is the nucleus responsible for fear. ### - 2 - The Fornix A small structure that is an important connecting pathway for the limbic system ### 3 - The Cingulate Gyrus It coordinates smells and sights, with pleasant memories of previous emotions. The region participates in the emotional reaction to pain and in the regulation of aggressive behavior.