Anatomy of the Nervous System 23-24 PDF - Al-Farahidi University

College of Pharmacy Al-Farahidi University Anatomy of the Nervous System Human Anatomy for 1st-year Pharmacy Students ‫ رائد ضياء هاشم‬.‫د‬.‫م‬.‫ا‬ 23-24  Al-Farahidi University College of Ph...

College of Pharmacy Al-Farahidi University Anatomy of the Nervous System Human Anatomy for 1st-year Pharmacy Students ‫ رائد ضياء هاشم‬.‫د‬.‫م‬.‫ا‬ 23-24  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students Anatomy of the Nervous system Adaptation to the environment is one of the most important features characterizing our body. This magic feature is a result of integration and cooperation between various systems in the body, at the top of which are the nervous system and the endocrine system. The nervous system enables the body to react to continuous changes in its external and internal environments. It controls and integrates various activities of the body, such as circulation and respiration. The nervous system is divided into two main parts: the central nervous system, which consists of the brain and spinal cord, and the peripheral nervous system, which consists of a paired series of cranial and spinal nerves and their associated ganglia. Functionally, the nervous system can be further divided into the somatic nervous system and the autonomic nervous system. The somatic nervous system acts upon the body’s external environment, primarily through the actions of skeletal muscles, and uses mostly voluntary responses to consciously perceived sensory signals from the body wall and limbs. The autonomic nervous system (ANS) acts upon the body’s internal environment, primarily through the actions of smooth muscle, cardiac muscle, and glands, and uses mostly involuntary responses to sensory signals that are not consciously perceived. 1  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students Nervous tissue consists of two main cell types: neurons (nerve cells and neuroglia（glial cells). 1- Neurons: These are regarded as the functional units of the nervous system. Each neuron has three main components: the cell body and two types of processes termed dendrites and an axon. Dendrites typically conduct nerve impulses toward the cell body and are the short processes of the cell body. The axon usually conducts impulses away from the cell body and dendrites and is the longest process of the cell body. 2- Glial cells - Five times as abundant as neurons - non-excitable cells - Support, insulate and nourish the neurons The interior of the CNS is organized into the grey and white matter. Grey matter consists largely of nerve cell bodies embedded in neuroglia. White matter consists largely of nerve processes (axons) and blood vessels embedded in the neuroglia. Central Nervous System The central nervous system (CNS) consists of the brain and spinal cord. The primary roles of the central nervous system are to integrate and coordinate incoming and outgoing neural signals and to carry out higher mental functions, such as thinking and learning. The CNS is enveloped with a membranous layer called meninges which are composed of three layers called: 1- Dura mater (the outermost layer) 2- Arachnoid mater (the middle layer) 3- Pia matter (innermost layer) 2  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students The meninges have essential functions that include: 1- Protection of the brain and spinal cord from mechanical trauma. 2- Supporting the blood vessels supplying the cerebrum and cranium. 3- providing nourishment and waste removal from the brain. It should be mentioned that the cerebrospinal fluid (CSF) passes through the subarachnoid space. Its total volume is 150 ml. The brain is composed of three main parts: the brainstem, cerebellum, and cerebrum. 1- Cerebrum The cerebrum is the largest part of the brain. The most conspicuous features on the surface of each hemisphere are numerous folds called gyri, which greatly increase the surface area of the cortex, and intervening grooves called sulci. The cerebrum is divided into two hemispheres: the left and right hemispheres. The left and right hemispheres are interconnected by the corpus callosum, yet they are responsible for different actions, which is known as brain lateralization. With language, reasoning, and math skills, the left hemisphere is more prominent while the right hemisphere is more related to creativity and intuitive, predominating in artistic and musical settings. Each hemisphere is divided into 4 lobes: a. Frontal b. Parietal c. Temporal d. Occipital 3  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students Each hemisphere controls the opposite side of the body, but not all functions of the hemispheres are shared (the left controls speech, comprehension, arithmetic, and writing; the right controls creativity, spatial ability, artistic, and musical skills). Each cerebral lobe has a specific function that can be summarized as follows: The frontal lobe: 1- Memory 2- Speech and language 3- Personality The parietal lobe 1- Learning 2- Spatial sensation 3- Stereognosis (the ability to distinguish between objects based on their size, shape, weight, and other characteristics). The Temporal Lobe 1- perceiving sounds and assigning their meaning 2- remembering sounds 3- recognition of language The occipital lobe 1- Vision Blood supply of the brain Four large arteries supply blood to the brain: 1- the paired internal carotid arteries 2- 2- the paired vertebral arteries. These four blood vessels feed into the cerebral arterial circle of WILLIS. 4  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students 2- The cerebellum The cerebellum, alternatively known as the little brain, is in charge of coordinating and smoothing out voluntary movements. It is divided into 3 lobes that communicate with other areas of the brain via Purkinje cells and cerebellar peduncles. It is largely made up of afferent fibers that provide signals to the cerebellum when voluntary motor activities are performed. The cerebellum communicates constantly with the cerebral cortex, receiving higher-level instructions about the brain's intentions, processing them in the cerebellar cortex, and then delivering information to the cerebral motor cortex to cause voluntary muscle contractions. These contractions are computed to estimate the force, direction, and momentum required to ensure smooth and coordinated contractions. 3- The brainstem It is that part of the CNS that connects the cerebrum to the spinal cord and cerebellum. It is primarily divided into 3 main parts: Midbrain Pons medulla oblongata It contains the neurons that are responsible for many vital functions in the human body including: - blood pressure and heart rate regulation - breathing - sleeping - consciousness 5  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students The spinal cord The spinal cord is the elongated, cylindrical part of the central nervous system below the head. It is completely enclosed within the vertebral canal of the vertebral column. At the gross anatomic level, the spinal cord begins above the foramen magnum, where it is continuous with the medulla oblongata of the brain. In the adult, it terminates inferiorly at about the level of the first lumbar vertebra. The spinal cord ends inferiorly as a tapered cone termed the conus medullaris. A prolongation of the pia mater descends from the apex of the conus and attaches to the back of the coccyx. Its length is about 45 cm in men and 43 cm in women. The spinal cord is responsible for carrying signals from the brain to the rest of the body and vice versa, although it might act independently from the brain in certain cases (spinal reflexes). The spinal cord contains the roots of 31 spinal nerves: - 8 cervical - 12 thoracic - 5 lumbar - 5 sacral - 1 coccygeal 6  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students Peripheral Nervous System (PNS) The peripheral nervous system consists of the cranial and spinal nerves and their associated ganglia. In other words, it includes all components of the nervous system other than the brain and the spinal cord. A ganglion is a cluster of neuron cell bodies located outside the CNS. In dissection, the cranial and spinal nerves appear as greyish-white cords. They are made up of bundles of neuron processes (axons) supported by delicate areolar tissue. Cranial Nerves Cranial nerves are twelve pairs of nerves originating from the brain. Some of these nerves have motor functions only, sensory functions only or mixed. 7  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students These nerves are: i. Olfactory ii. Optic iii. Oculomotor iv. Trochlear v. Trigeminal vi. Abducent vii. Facial viii. Vestibulocochlear ix. Glossopharyngeal x. Vagus xi. Accessory xii. Hypoglossal. They are originating from multiple sites of the brain: o To the forebrain: First and second nerves. o To the midbrain: Third and fourth nerves. o To the pons: Fifth, sixth, seventh and eighth nerves. o To the medulla oblongata: Ninth, tenth, eleventh and twelfth nerves. The Vagus nerve has an exception in its distribution as it extends to the thorax and abdomen while other cranial nerves' distribution is limited to the head and neck. Spinal Nerves A total of 31 pairs of spinal nerves leave the spinal cord and pass-through intervertebral foramina in the vertebral column. The spinal nerves are named according to the region of the vertebral column with which they are associated: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each nerve splits into branches outside the spinal column. The dorsal ramus contains nerves that service the trunk's dorsal regions; it transports visceral motor, somatic motor, and somatic sensory information to and from the back's skin and muscles (epaxial muscles). The ventral ramus contains nerves that service the remaining ventral sections of the trunk, as well as the 8  Al-Farahidi University College of Pharmacy st Human Anatomy for 1 year pharmacy students upper and lower limbs (hypaxial muscles). These nerves transport visceral motor, somatic motor, and sensory information to and from the ventrolateral body surface, body wall structures, and limbs. 9