Nervous System Lecture Notes PDF

GENERAL ANATOMY FIRST TERM || FINALS|| DRA.REPIL LECTURE NERVOUS SYSTEM OVERVIEW CELL BODY / SOMA ➔ 2 kg (4.5 lbs) in mass...

GENERAL ANATOMY FIRST TERM || FINALS|| DRA.REPIL LECTURE NERVOUS SYSTEM OVERVIEW CELL BODY / SOMA ➔ 2 kg (4.5 lbs) in mass ➔ Contains the organelles of a cells including the ➔ 3% of the total body weight nucleus ➔ Smallest yet m,ost complex system ➔ Processes and interprets all the messages that it receives and transmits They are grouped together in the entire nervous system (Gray matter) TWO MAIN SUBDIVISIONS DENDRITES A. CENTRAL NERVOUS SYSTEM (CNS): - PROCESSING CENTER ➔ Often receives stimulus and transmit it towards the body B. PERIPHERAL NERVOUS SYSTEM (PNS): - DELIVERY NETWORK AXON ➔ Often transmit the message away from the body ➔ Axons vary in length and are usually a lot longer than A.1 PARTS OF CENTRAL NERVOUS SYSTEM dendrites ➔ Covered by a membrane axolemma NAME COMPONENTS FUNCTION AXON TERMINAL OF PART ➔ Most distal end of the axon BRAIN CEREBRUM encased on the ➔ will transfer the impulse or the message to another BRAINSTEM skull and neuron or an effector organ. CEREBELLUM vertebral column AXON HILLOCK ➔ A cone shaped-portion of the cell body as it SPINAL CERVICAL CORD embedded in CORD THORACIC CORD connects into the axon the muscles and LUMBAR CORD ➔ Attached is the initial segment which is the most viscera SACROCOCCYGEAL excitable part of the axon. CORD NUCLEUS (NUCLEI) B.1 PARTS OF THE PERIPHERAL NERVOUS SYSTEM ➔ Within the brain but outside of the cerebral cortex GANGLION ( GANGLIA) NAME OF PART COMPONENTS SPINAL NERVE 31 PAIRS NAME OF PART COMPONENTS CRANIAL NERVES 12 PAIRS Outside of the spinal cord PERIPHERAL NERVES Autonomic ganglion A cluster of neuronal cell bodies and their AUTONOMIC NERVES dendrites and is essentially a junction between autonomic nerves originating from STRUCTURAL CLASSIFICATION OF NEURONS the CNS and autonomic nerves innervating their target organs in the periphery. Dorsal root/ Spinal ganglion  ➔ Lines the ventricles of the brain and spinal cord to MYELIN SHEATH form the CSF ➔ lipid-rich insulating material MICROGLIA ➔ arranged in multiple concentric layers ➔ Phagocytic cells and macrophages or scavengers ➔ Produced by the Schwann cells in the PNS and of the CNS Oligodendrocytes in the CNS ➔ Form the part of the NS’s defense against infection or injury NODES OF RANVIER WHITE MATTER VS GRAY MATTER NAME OF PART COMPONENTS WHITE MATTER Represents nerve fibers (axon) or process of neurons Primarily composed of myelinated axons The whitish color of myelin gives the white matter its name ➔ Points along the axon NOT myelinated ➔ Allows SALTATORY conduction: Impulse jumps from GREY MATTER Represents the cell bodies of neurons one node to another along the length of the axon for arranged in a laminar layer or layered manner faster conduction It appears greenish because of the NISSL BODIES. The NB impart a gray color and there is little to no myelin in TYPES OF NEURON ACCORDING TO STRUCTURE these areas shaped like the letter H or a butterfly NAME OF PART COMPONENTS UNIPOLAR NEURON WITH SINGLE AXON BIPOLAR NEURO WITH 1 DENDRITE 1 AXON MULTIPOLAR NEURON WITH SEVERAL DENDRITES AND 1 AXON NEUROGLIA/ GLIAL CELLS SYNAPSES CNS PNS ➔ Communication between neurons ➔ Occurs from the axon terminal of the transmitting ASTROCYTES SCHWANN CELLS/ neurons to the receptive region of the receiving NEUROLEMMOCYTES axon OLIGODENDROCYTES SATELLITE CELLS TYPES OF SYNAPSE MICROGLIA EPENDYMAL CELLS CNS PNS AXODENDRITIC Connection formed between ASTROCYTES the axon of one neuron and ➔ A structure and metabolic sport the dendrite of another ➔ Satellite cells — specific to PNS AXOSOMATIC Direct communication ➔ Regulators of electrolyte balance between axon of one neuron ➔ Formation of BBB( BLOOD-BRAIN- BARRIER) to the cell body of another ➔ Repair of damage tissue axon AXOAXONIC Made by neurons into the EPENDYMAL CELLS synapse of another neuron  a somatic nervous system and an autonomic nervous system ORGANIZATION OF THE NERVOUS SYSTEM a. Somatic nervous system (SNS) - conveys output from the CNS to skeletal muscles only. Because its motor responses CENTRAL NERVOUS SYSTEM can be consciously controlled, the action of this part of the PNS is voluntary. ➔ Consist of brain and spinal cord ➔ The CNS processes many kinds of incoming sensory b.Autonomic nervous system (ANS) - conveys output from formation the CNS to smooth muscle, cardiac muscle, ➔ Source of thoughts, emotion, and memories and glands. Because its motor responses are not normally ➔ Most signals that stimulate muscles to contract and under conscious control, the action of the ANS is involuntary glands to secrete originate in the CNS 2 main branches of ANS: BRAIN SPINAL CORD 1. Sympathetic division Part of the CNS that is Connected through the brain ➔ helps support exercise or emergency actions—the in the skull through the foramen magnum so-called “fight-or flight” responses of the occipital bone and is encircled by the bones of 2. Parasympathetic division vertebral column ➔ “rest-and-digest” activities ➔ With a few exceptions, effectors (motor division) contains about 85 Contains about 100 million receive innervation from both of these parts, and billion neurons neurons usually the two divisions have opposing actions. ➔ SYM AND PARA DO NOT WORK TOGETHER PERIPHERAL NERVOUS SYSTEM ➔ Consist of all nervous tissue outside the CNS ( A third branch of ANS: Enteric plexuses ( 2ND BRAIN) nerves and sensory receptors) ➔ an extensive network of over 100 million neurons ➔ 12 PAIRS of cranial nerves emerges from the brain confined to the wall of the digestive canal. and 13 PAIRS of spinal nerves emerges from the ➔ regulate the activity of the smooth muscle and spinal cord glands of the digestive canal. ➔ Divided into 2 divisions: ➔ Spinal cord ng reflex arch A. SENSORY AFFERENT DIVISION B. MOTOR EFFERENT DIVISION Although the enteric plexuses can function independently, they communicates with and are regulated by the other NERVE branches of the ANS A nerve is a bundle of hundreds to thousands of axons plus associated connective tissue and blood vessels that lies outside the brain and spinal cord SENSORY RECEPTOR Structure of the NS that monitors changes in the external or internal environment. Ex: touch receptors in the skin, photoreceptors in the eye and olfactory receptors in the nose A. SENSORY AFFERENT DIVISION ➔ conveys input into the CNS from sensory receptors in the body. FUNCTIONS OF THE NERVOUS SYSTEM ➔ provides the CNS with sensory information about the somatic senses (tactile thermal, pain, and proprioceptive sensations) and special senses (smell, taste, vision, hearing,and equilibrium) B. MOTOR EFFERENT DIVISION ➔ conveys output from the CNS to effectors (muscles and glands). This division is further subdivided into  SENSORY FUNCTION INTEGRATIVE FUNCTION MOTOR FUNCTION INPUT PROCESS OUTPUT BRAIN SPINAL CORD Detects stimuli such as increase in bp Process Information by analyzing it called integration sensory information is integrated, the nervous system may elicit an appropriate WHITE MATTER – inner part WHITE MATTER – outer part motor response by activating effectors (muscles and glands) through cranial and spinal nerves GRAY MATTER – outer part GRAY MATTER – inner part Carried into the brain and spinal causes muscles to contract and glands cord through cranial and spinal to secrete nerves EXTERNAL ANATOMY OF SPINAL CORD CRANIAL NERVES SPINAL CORD ➔ Rough oval shape, being flattened slightly NO. NAME TYPE OF DESCRIPTION anteriorly and posteriorly. FUNCTION ➔ ADULTS: extend from the medulla oblongata, I OLFACTORY SENSORY SMELL the inferior part of the brain, to the superior II OPTIC SENSORY VISION border of the second lumbar vertebra ➔ NEWBORN INFANTS: extends to the third or III OCULOMOTOR MOTOR MOVEMENT OF EYEBALLS AND UPPER EYELID AND CONSTRUCTION OF PUPIL fourth lumbar vertebra IV TROCHLEAR MOTOR MOVEMENT OF EYEBALLS When the spinal cord is viewed externally, two conspicuous V TRIGEMINAL MIXED V1. OPHTHALMIC: FOR MASTICATION enlargements can be seen. TEMPERATURE INTERNAL PTERYGOID MASSETER CERVICAL ENLARGEMENT EXTERNAL PTERYGOID ➔ Superior enlargement that extends from the V2. BUCE V3. MANDIBULAR fourth cervical vertebra (C4) to the first thoracic vertebra (T1) VI ABDUCENS MOTOR MOVEMENT OF EYEBALLS ➔ Nerves to and from the upper limbs arise VII FACIAL MIXED -Functions for all facial expression from the CE - anterior 2/3 of the tongue TEMPORAL ZYGOMATIC LUMBOSACRAL ENLARGEMENT BUCCAL MANDIBULAR ➔ Inferior enlargement that extends from the CERVICAL ninth to 12 thoracic vertebra VII VESTIBULOCOCHLEAR / AUDITORY NERVE SENSORY Hearing and equilibrium ➔ Nerves to and from the lower limbs arise from the lumbar enlargement IX GLOSSOPHARYNGEAL MIXED Posterior ⅓ of the tongue X VAGUS MIXED Taste from epiglottis. Swallowing, CONUS MEDULLARIS vocalization, and coughing. Constriction of respiratory passageways. ➔ conical structure that is inferior to the lumbar XI ACCESSORY/SPINAL MOTOR Movement of head and pectoral girdle enlargement and where the spinal cord NERVE terminates as a tapering,which ends at the XII HYPOGLOSSAL MOTOR Speech, manipulation of food, and level of the intervertebral disc between the swallowing first and second lumbar vertebrae (L1–L2) in adults. C1 & C2 : FOUND IN THE CORTEX C2: NOT TRUE CN, DIRECT TO THE CORTEX ➔ Spinal Tap – L3-L4, L4-L5 C3-C12: FOUND IN THE BRAIN STEM FILUM TERMINALE SPINAL CORD AND SPINAL NERVES ➔ An extension of the pia mater that extends inferiorly, fuses with the arachnoid mater and dura mater, and anchors the spinal cord to the ➔ The spinal cord and spinal nerves contribute coccyx. to homeostasis by providing quick, reflexive responses to many stimuli. ➔ Spinal cord is the pathway for sensory input to the brain and motor output from the brain.  ROOTS ➔ two bundles of axons, called roots, ROOTLETS ➔ connect each spinal nerve to a segment of the cord by even smaller bundles of axons Posterior root and rootlets ➔ contain only sensory axons, which conduct nerve impulses from sensory receptors in the skin, muscles, and internal organs into the central nervous system. SPINAL GANGLION (dorsal root) ➔ which contains the cell bodies of sensory SPINAL NERVES neurons. ➔ are the paths of communication between the Anterior root and rootlets spinal cord and specific regions of the body. ➔ contain axons of motor neurons, which conduct ➔ 31 pairs of spinal nerves that emerges from nerve impulses from the CNS to effectors the intervertebral foramen (muscles and glands). 8 pairs of cervical nerves (C1-C8) CAUDA EQUINA (horse’s tail) 12 pairs of thoracic nerves (T1–T12) ➔ are roots of the lower spinal nerves angle 5 pairs of lumbar nerves (L1–L5) inferiorly alongside the filum terminale in the 5 pairs of sacral nerves (S1–S5) vertebral canal like wisps of hair. 1 pair of coccygeal nerves (Co1) INTERNAL ANATOMY OF SPINAL CORD ANTERIOR MEDIAN POSTERIOR MEDIAN FISSURE SULCUS Wide groove on the anterior Narrow furrow on the posterior (ventral) side dorsal side GRAY MATTER ➔ Gray commissure forms the crossbar of the H. ➔ center of the gray commissure is a small space called the central canal ➔ At its superior end, the central canal is continuous with the fourth ventricle (a space that contains cerebrospinal fluid) in the medulla oblongata of the brain. ➔ Anterior to the gray commissure is the anterior white commissure, which connects the white matter of the right and left sides of the spinal cord NUCLEI ➔ clusters of neuronal cell bodies HORNS ➔ Subdivided regions of gray matter on each side of spinal cord ANTERIOR GRAY HORN ➔ Contains somatic motor nuclei ➔ cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles POSTERIOR GRAY HORN ➔ contain axons of incoming sensory neurons as well as cell bodies and axons of interneurons. ➔ Recall that cell bodies of sensory neurons are located in the spinal ganglion of spinal nerves. LUMBAR PLEXUS LATERAL GRAY HORN ➔ Between the posterior and anterior gray horn ➔ Present only in thoracic and upper lumbar and mid sacral segments of the spinal cord PERIPHERAL NERVES CERVICAL PLEXUS SACRAL PLEXUS BRACHIAL PLEXUS