Nervous System PDF

NERVOUS SYSTEM - provides for higher mental function and emotional expression - maintains homeostasis - regulates the activities of muscles and glands - communication by this involves a combination of electrical and chemical signals - all body systems are under control or...

NERVOUS SYSTEM - provides for higher mental function and emotional expression - maintains homeostasis - regulates the activities of muscles and glands - communication by this involves a combination of electrical and chemical signals - all body systems are under control or regulation of this system - works with endocrine system in maintaining homeostasis and regulating systems - has three overlapping functions: 1. It uses millions of sensory receptors to monitor changes occurring both inside and outside the body  Stimuli = the changes  Sensory input = gathered information 2. It processes and interprets the sensory input and decide what should be done at each ORGANIZATION OF THE NERVOUS SYSTEM moment = Integration STRUCTURAL CLASSIFICATION - has two subdivisions: 3. It then causes a response or effect by activating muscles or glands via Motor Input 1.CENTRAL NERVOUS SYSTEM (CNS) - consists of the brain and spinal - occupies the dorsal body cavity - act as the integrating and command centers of nervous system - interprets incoming sensory information - issues instructions based on past - not all skeletal muscle activity experience and current conditions controlled by this is voluntary 2. PERIPHERAL NERVOUS SYSTEM (PNS)  Autonomic/ Involuntary Nervous - includes all parts of nervous system outside System the CNS (nerves that extend from spinal - regulates events that are involuntary cord and brain) - has two parts:  Sympathetic  Spinal nerves  Parasympathetic - carry impulses to and from the spinal - what one stimulates, the other cord inhibits  Cranial nerves - carry impulses to and from the brain NERVOUS TISSUE: STRUCTURE AND FUNCTION - both serve as communication lines - has two principal types of cells 1. SUPPORTING CELLS PNS FUNCTIONAL CLASSIFICATION - has two major varieties: - divides into two principal subdivisions:  Schwann Cells 1. SENSORY/ AFFERENT DIVISION - form the myelin sheathes around nerve - consists of nerves that convey carries fibers in the PNS impulses to the CNS from sensory receptors - keeps the CNS constantly informed of events  Satellite Cells going inside and outside the body - act as protective, cushioning cells for peripheral neuron cell bodies  Somatic Sensory Fibers - delivers impulses from the skin, skeletal NEUROGLIA muscles, and joints - also called as glial cells or glia - supporting cells in CNS that are “lumped  Visceral Sensory Fibers together” - transmit impulses from the visceral - not able to transmit nerve impulses organs - include many types of cells:  Astrocytes 2. MOTOR/ EFFERENT DIVISION - abundant star -shaped cells that - carries impulses from CNS to effector organs account for nearly half of neural tissue (muscles and glands) - form a living barrier between capillaries - impulses causes a motor response and neurons - has two subdivisions: - help determine capillary permeability - play a role in making exchanges  Somatic/ Voluntary Nervous System between capillaries and neurons - allows us to voluntarily control our - helps control the chemical environment skeletal muscles in the brain   Microglia  Processes - spinderlike phagocytes that monitor - armlike fibers very in length the health of nearby neurons dispose of  Dendrites - conveys incoming debris messages toward the cell body  Axons - generates nerve impulses  Ependymal cells and conduct them away from the - lines the central cavities of the brain cell body and spinal cord  Axon Hillock - conelike region of the cell body where axon arises  Oligodendrocytes  Axon terminals - contains hundreds - wraps their flat extensions tightly of tiny vesicles, or membranous around the nerve fibers, producing fatty sacs, that insulating coverings called Myelin contain chemicals called Sheaths neurotransmitters  Synaptic cleft - a tiny gap which separates each axon terminal from 2. NEURONS the next neuron - also called as nerve cells  Synapse - a functional junction - highly specialized to transmit message/ where an impulse is transmitted nerve impulses from one part of the body to from one neuron to another another - differ structurally from one another but all  Myelin Sheaths have cell body - a whitish, fatty material which has a waxy appearance, covers most of the  Cell body long fibers - the metabolic center of the neuron - protects and insulates the fibers - cytoplasm surrounding the nucleus - increases the transmission rate of nerve contains the usual organelles, except impulses that it lacks centrioles - abundant in cell body:  Terminology  Nissl Bodies - rough ER - Nuclei - clusters in CNS where cell  Neurofibrils - intermediate bodies are found filaments that are important in - Ganglia - small collections of cell bodies maintaining cell shape that are found in a few sites outside the CNS in the PNS - Tracts - bundles of nerve fibers running through the CNS - Nerves - bundles of nerve fibers running through the PNS  Functional Classification  - Sensory/ Afferent neurons - neurons - as this develop and grow, they enclose and carrying impulses from sensory obscure most of the brain, so many brain receptors to the CNS stem structures cannot normally be seen - Cutaneous Sense Organs - simpler unless a sagittal section is made types of sensory receptors in the skin - Gyri - elevated ridges of tissue that exhibits - Proprioceptors - simpler types of the entire surface of cerebrum sensory receptors in the muscles and - Sulci - shallow grooves that separates gyri tendons that detects the amount of stretch or tension in skeletal muscles  Cerebral Cortex - Motor/ Efferent neurons - neurons - speech, memory, logical and emotional carrying impulses from the CNS to the responses, consciousness, the viscera and/or muscles and glands interpretation of sensation, and - Interneurons/ Association neurons - voluntary movement connects the motor and sensory neurons in neural pathways  Cerebral White Matter - most of the remaining cerebral  Structural Classification hemisphere tissue - based on the number of processes, - composed of fiber tracts carrying including both dendrites and axons, impulses to, from, or within the cortex extending from the cell body - Multipolar neuron - several process  Basal Nuclei - Bipolar neurons - with two process - several “islands” of gray matter —one axon and one dendrite - buried deep within the white matter of - Unipolar neurons - single process the cerebral hemispheres emerging from the cell body - help regulate voluntary motor activities 2. DIENCEPHALON/ INTERBRAIN CENTRAL NERVOUS SYSTEM - sits atop the brain stem - enclosed by the cerebral hemispheres - major structures are:  Thalamus - encloses the shallow third ventricle of the brain - relay station for sensory impulses passing upward to the sensory cortex  Hypothalamus - makes up the floor of the diencephalon - important autonomic center FUNCTION ANATOMY OF THE BRAIN - has a role in regulating body - has four major regions: temperature, water balance, and metabolism 1. CEREBRAL HEMISPHERES - center for many drives and - collectively called as Cerebrum emotions - the most superior part of the brain   Epithalamus - forms the roof of the third ventricle - Pineal gland and Choroid plexus are the important parts of epithalamus 3. BRAIN STEM - about the size of a thumb in diameter and approximately 3 inches long - has many small gray matter areas - its structures are:  Midbrain - a relatively small part of the brain stem - extends from the mammillary bodies to the pons inferiorly  Pons - a rounded structure that protrudes just below the midbrain - have important nuclei involved in the control of breathing  Medulla Oblongata - the most inferior part of the brain stem - contains centers that control heart rate, blood pressure, breathing, - provides the precise timing for skeletal swallowing, and vomiting muscle activity and controls our balance - an important fiber tract area - the area where important SPINAL CORD pyramidal tracts cross over to the - a glistening white continuation of the brain opposite side stem - provides a two-way conduction pathway to  Reticular Formation - a diffuse mass of and from the brain gray matter that extends the entire - a major reflex center length of the brain stem - extends from the foramen magnum of the - neurons of this are involved in skull to the 1st or 2nd lumbar vertebra motor control of the visceral organs - cushioned and protected by meninges GRAY MATTER OF THE SPINAL CORD AND 4. CEREBELLUM SPINAL ROOTS - large, cauliflower-like that projects dorsally - looks like a butterfly or letter H in cross from under the occipital lobe of the section cerebrum - Dorsal/ Posterior Horns - two posterior - has two hemispheres and a convoluted projections surface - Ventral/ Anterior Horns - two anterior projections - gray matter surrounds the central canal of the cord which contains CSF PERIPHERAL NERVOUS SYSTEM - consists of nerves and scattered ganglia STRUCTURE OF A NERVE - Nerve - a bundle of neuron fibers found outside the CNS - Endoneurium - a delicate connective tissue sheath that surrounds each fiber - Perineurium - a coarser connective tissue that wrap groups of fibers to form Fascicles (fiber bundles) - Epineurium - a tough fibrous sheath that bound all the fascicles together to form the cordlike nerve CRANIAL NERVES - 12 pairs of this primarily serve the head and neck - only the vagus nerves extends to the thoracic and abdominal cavities - most of it are mixed nerves - Optic, Olfactory, & Vestibulocohlear nerves - purely sensory in function SPINAL NERVES AND NERVE PLEXUSES - each spinal nerve divides into  Dorsal Ramus  Ventral Ramus - rami contain both motor and sensory fibers  Essentials of Human Anatomy & Physiology 12th Edition. Marieb, E.N & Keller, 2016. S.M. Boston : Pearson. (PDF) AUTONOMIC/ INVOLUNTARY NERVOUS SYSTEM - the motor subdivision of the PNS that controls body activities automatically - composed of a specialized group of neurons that regulate cardiac muscle, smooth muscles, and glands - signals flood from the visceral organs into the CNS, and the ANS makes adjustments as necessary to best support body activities - has two arms:  Sympathetic/ Thoracombular Division - “fight-or-flight” system - mobilizes the body during extreme situations - working at full speed not only when you are emotionally upset but also when you are physically stressed  Parasympathetic/ Craniosacral Division - ”rest-and-digest” - allows us to unwind and conserve energy - neurons of the cranial region send their axons out in cranial nerves to serve the head and neck organs - chiefly concerned with promoting normal digestion - serves body organs by receiving fibers from both divisions - exceptions are most blood vessels and most structures of the skin, some glands, and the adrenal medulla (only receive sympathetic fibers) REFERENCE: