Nervous System PDF

 I- Central nervous system It formed of : -The brain: Inside the skull. -The spinal cord: Inside the vertebral column. Parts of the brain: 1- Forebrain: It includes the cerebrum and diencephalon. 2- Midbrain: The part below the diencephalon. 3- Hindbrain:It includes the pons, med...

 I- Central nervous system It formed of : -The brain: Inside the skull. -The spinal cord: Inside the vertebral column. Parts of the brain: 1- Forebrain: It includes the cerebrum and diencephalon. 2- Midbrain: The part below the diencephalon. 3- Hindbrain:It includes the pons, medulla oblongata and the cerebellum.  Cerebrum Forebrain Diencephalon Midbrain Pons Hindbrain Medulla oblongata Cerebellum Brain stem: It is the part which connect the cerebrum with the spinal cord. It includes: The midbrain, the pons and the medulla oblongata. Around the brain and the spinal cord there are three layers of meninges: Dura matter, arachnoid matter, and pia matter. Between the dura and arachnoid matters (in subarachnoid space), there is the cerebrospinal fluid (CSF). CSF is clear, clorless fluid arised from the lateral ventricles of the cerebral hemisphere, pass to the 3rd ventricle between the diencephalon of both side, thenthrough the cerebral aquiduct of the midbrain to the 4th ventricle of the hindbrain. From the fourth ventricle, the fluid passes into the subarachnoid space which covers the brain and spinal cord through four openings in the roof of the 4th ventricle.  1- Cerebrum: - It is the largest part of the brain. - It is devided into 2 cerebral hemisphere by a medial longitudinal fissure. - Each cerebral hemisphere has three surface: Superolateral, medial and inferior surfaces. - Its surface shows sulci and gyri to increase its surface area. - Each cerebral hemisphere contain 3 main sulci: Central, lateral and parieto occipital sulci. - These sulci divide the hemisphere into main lobes: Frontral lobe: Contain motor gyri for the body. Parietal lobe: Contain sensory areas. Temporal lobe: Contain auditory area. Occipital lobe: Contain visual area. Cross section in the cerbral hemishere: - The superficial part formed of nerve cell bodies (grey matter) and form the cerebral cortex. - The deeper part formed of nerve cell axons (white matter). 2 - Brain stem: It is the part between the cerebrum and the spinal cord. Formed of 3 parts: - Midbrain: Just below the diencephalon and ontain canal called cerebral aqueduct. - Pons: between the midbrain and medulla oblongata. - Medulla oblongata:It continous downward with the spinal cord at the foramen magnum. Brain stem function: 1- It provides pathway for tracts between the cerebral cortex and spinal cord. 2 - Site of origin of nuclei of cranial nerves. 3- Cerebellum: Part of the brain lies behind the pons and medulla oblongata. Separated from them by 4th ventricle. Function of the cerebellum: - coordination of movement, maintaining posture and balance, muscle tone. Spinal cord: - Column of nerve tissue that begin at the base of the brain as a continuation of the medulla oblongata. - Descends in the vertebral canal of the vertebral column to ends at the intervertebral disk between 1st and 2nd lumbar vertebrae. - Surrounds by dura, arachnoid and pia matter. - It is devided into 5cervical, 12 thorscic, 5 lumbar, 5 sacral and 1 coccygeal segments. Croos section in the spinal cord: - It is formed of H shaped central gray matter (nerve cell body) and peripheral white matter (nerve cel axons). Spinal nerves: - 31 pairs of nerves arised from spinal cord segments and exit from the intervertebral foramina. - Each nerve connected to its spinal cord segments by ventral (anterior, motor) root and dorsal (posterior, sensory)root. - Ventral roots convey motor information through efferent nerve fibers. - Dorsal roots cnvey sensory information through afferent nerve fibers, and contain cllection of nerve cell bogy called (Dorsal root ganglion). - Both ventral and dorsal roots unite together formind a mixed nerve trunk. - Mixed nerve trunk divides outside the intervertebral foramina int dorsal and ventral rami.  II- Peripheral nervous system - There are 12 cranial nerves arised from the brain and 31 pairs of spinal nerves arised from the spinal cord. - Fibers of these nerves either ( fibers concerned with innervation of skin, skeletal muscle, their tendon, joint). or autonomic ( fibers concerned with innervation of viscera, heart, blood vessels and glands) it is either or Autonomic Nervous System Sympathetic Parasympathetic * Thoraco-lumbar origin (T1-L2 * Cranio-sacral origin: Cranial, or L3) 3,7,9&10. Sacral 2,3&4. * Short preganglionic fibers. * Long preganglionic fibers. * Long postganglionic fibers. * Short postganglionic fibers. * Sympathetic ganglia * Parasympathetic ganglia in arranged in form of head and neck – Terminal ganglia close to the organ. longitudinal chain along the sides of vertebral column. * Conserve energy & restore relaxation. * Prepare the body for responding to dangerous or stressful situations.