Nervous system


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Nervous system

  2. 2. NERVOUS SYSTEM <ul><li>is the master controlling and communicating system of the body; works with other organ system; </li></ul><ul><li>electrical impulses which act as signaling device and as a means of communicating with body cells are specific and cause an immediate response; </li></ul><ul><li>three overlapping functions: </li></ul><ul><ul><ul><li>monitor changes occurring both inside and outside the body (stimuli); the gathered input is called SENSORY INPUT; </li></ul></ul></ul><ul><ul><ul><li>it process and interprets the sensory input and decides on the input (INTEGRATION) </li></ul></ul></ul><ul><ul><ul><li>it effects a response by activating muscles or glands (MOTOR OUTPUT) </li></ul></ul></ul>
  3. 3. <ul><li>Structural Classifications: </li></ul><ul><ul><li>Central Nervous System (CNS) – consists of the brain and spinal cord; </li></ul></ul><ul><ul><li>Peripheral Nervous System (PNS) – outside the CNS; consists of the spinal nerves and cranial nerves </li></ul></ul><ul><li>Functional Classification: (concerned only with PNS structures) </li></ul><ul><ul><li>Sensory or Afferent division – consists of nerves that convey impulses to the CNS from sensory receptors located in various parts of the body; </li></ul></ul><ul><ul><ul><li>Sensory fibers delivering impulses from the skin, skeletal muscles, and joints are called SOMATIC SENSORY FIBERS; </li></ul></ul></ul>
  4. 4. <ul><ul><ul><li>Sensory fibers transmitting impulses from the visceral organs are called VISCERAL SENSORY FIBERS; </li></ul></ul></ul><ul><ul><li>2. Motor or Efferent division – carries impulses from the CNS to the effector organs, the muscles and glands; </li></ul></ul><ul><ul><ul><li>Somatic Nervous System – allows conscious or voluntary control of our movements; </li></ul></ul></ul><ul><ul><ul><li>Autonomic Nervous System – regulates events that are involuntary; such as the activity of smooth and cardiac muscles and glands; </li></ul></ul></ul><ul><ul><ul><ul><ul><li>Sympathetic NS </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Parasympathetic NS </li></ul></ul></ul></ul></ul>
  5. 5. <ul><li>STRUCTURE AND FUNCTIONS </li></ul><ul><ul><li>the nervous system is made up of two principal types of cells: </li></ul></ul><ul><ul><ul><ul><li>Supporting Cells </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Neurons </li></ul></ul></ul></ul><ul><li>SUPPORTING CELLS </li></ul><ul><ul><li>these cells in the CNS are lumped together as NEUROGLIA ; </li></ul></ul><ul><ul><li>generally made up of cells that support, insulate, and protect the delicate neurons; </li></ul></ul><ul><ul><li>types of neuroglia: </li></ul></ul><ul><ul><ul><li>Astrocytes – most abundant; form a living barrier between capillaries and neurons; play a role in making exchanges between the capillaries and neurons; </li></ul></ul></ul>
  6. 6. <ul><ul><ul><li>2. Microglia – are phagocytes that dispose of debris (dead brain cells, bacteria, etc.) </li></ul></ul></ul><ul><ul><ul><li>3. Ependymal cells – line the cavities of the brain and spinal cord; their beating cilia helps circulate CSF and forms a protective cushion around the CNS; </li></ul></ul></ul><ul><ul><ul><li>4. Oligodendrocytes – forms myelin sheath around the nerve fibers in the CNS ; </li></ul></ul></ul><ul><li>Supporting Cells in the PNS comes in two major forms: </li></ul><ul><ul><ul><li>Schwann Cells – form myelin sheath around the nerve fibers in the PNS ; </li></ul></ul></ul><ul><ul><ul><li>Satellite Cells – act as protective, cushioning cells; </li></ul></ul></ul>
  7. 7. <ul><li>NEURONS </li></ul><ul><ul><li>also called nerve cells ; </li></ul></ul><ul><ul><li>are the functional unit of the nervous system; </li></ul></ul><ul><ul><li>are highly specialized to transmit nerve impulses from one part of the body to another; </li></ul></ul><ul><ul><li>parts: </li></ul></ul><ul><ul><ul><li>Cell Body – contains the nucleus and is the metabolic center of the cell; </li></ul></ul></ul><ul><ul><ul><li>Dendrites – neuron processes that conduct nerve impulses toward the cell body; </li></ul></ul></ul><ul><ul><ul><li>Axons – processes that conduct nerve impulses away from the cell body; </li></ul></ul></ul>
  8. 8. <ul><ul><li>most long nerve fibers are covered with a whitish, fatty material, called MYELIN; </li></ul></ul><ul><ul><ul><ul><li>also protects and insulates the fibers and increases the transmission rate of nerve impulses; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>most axons are wrapped with myelin called MYELIN SHEATH; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>MULTIPLE SCLEROSIS </li></ul></ul></ul></ul><ul><li>Clusters of neuron cell bodies in the CNS are called NUCLEI; </li></ul><ul><li>Small collections of cell bodies in the PNS are called GANGLIA; </li></ul>
  9. 9. <ul><li>Functional Classification of a Neuron: </li></ul><ul><ul><li>Sensory / Afferent Neurons – carrying impulses from the sensory receptors to the CNS; </li></ul></ul><ul><ul><li>Motor / Efferent Neurons – carrying impulses from the CNS to the viscera and/or muscles and glands; </li></ul></ul><ul><ul><li>Interneurons – connect the motor and sensory neurons; </li></ul></ul>
  10. 10. <ul><li>Structural Classification of Neurons (based on the no. of processes) </li></ul><ul><ul><li>Multipolar Neurons – several processes; most common structural type; </li></ul></ul><ul><ul><li>Bipolar Neurons – contain two processes, an axon and a dendrite; </li></ul></ul><ul><ul><li>Unipolar Neurons – contain a single neuronal process; </li></ul></ul><ul><li>Neurons have two major functional properties: </li></ul><ul><ul><li>Irritability – ability to respond to a stimulus and convert it to a nerve impulse; </li></ul></ul><ul><ul><li>Conductivity – ability to transmit the impulse to other neurons, muscles, or glands; </li></ul></ul>
  11. 11. <ul><li>REFLEXES – are rapid, predictable, and involuntary response to stimuli; </li></ul><ul><ul><ul><li>Occur over neural pathways called REFLEX ARC (a complete circuit consisting of a sensory neuron ending in the spinal cord, connecting neuron within the cord, and a motor neuron to a muscle ); </li></ul></ul></ul><ul><ul><ul><li>Autonomic Reflexes regulate the activity of smooth muscles, the heart, and glands; ex. Salivary and Pupillary reflex </li></ul></ul></ul><ul><ul><ul><li>Somatic Reflexes includes all reflexes that stimulate the skeletal muscles; </li></ul></ul></ul>
  12. 12. <ul><li>CENTRAL NERVOUS SYSTEM </li></ul><ul><ul><li>originates in the NEURAL TUBE ; </li></ul></ul><ul><ul><li>is the part enclosed by bone or the cranium; </li></ul></ul><ul><ul><li>it includes the BRAIN and the SPINAL CORD; </li></ul></ul><ul><ul><li>the chambers of the brain are called VENTRICLES (filled with cerebrospinal fluid ) </li></ul></ul><ul><ul><li>Four Major Parts: </li></ul></ul><ul><ul><ul><li>Cerebrum </li></ul></ul></ul><ul><ul><ul><li>Diencephalon </li></ul></ul></ul><ul><ul><ul><li>Brainstem </li></ul></ul></ul><ul><ul><ul><li>Cerebellum </li></ul></ul></ul>
  13. 13. <ul><li>Anatomy of the Brain </li></ul><ul><ul><li>the brain is the largest and most complex mass of nervous tissue in the body; </li></ul></ul><ul><li>Four major regions of the brain: </li></ul><ul><li>Cerebral Hemispheres (cerebrum) </li></ul><ul><ul><li>are paired superior part of the brain; </li></ul></ul><ul><ul><li>enclose and obscure most of the brain stem; </li></ul></ul><ul><ul><li>Gyri – elevated ridges of tissue on the surface of the cerebral hemispheres; </li></ul></ul><ul><ul><li>Sulci – hollow grooves that separates the gyri; </li></ul></ul><ul><ul><li>The cerebral hemispheres are separated by a single deep fissure called the LONGITUDINAL FISSURE; </li></ul></ul>
  14. 14. <ul><li>Lobes of the brain: </li></ul><ul><ul><li>Parietal Lobe – area for somatic sensory; </li></ul></ul><ul><ul><li>Frontal Lobe – area for motor movement; </li></ul></ul><ul><ul><li>Occipital Lobe – area for vision; </li></ul></ul><ul><ul><li>Temporal Lobe – auditory and olfactory area; </li></ul></ul>
  15. 15. <ul><li>A specialized area that is involved in our ability to speak is called BROCA’S AREA; </li></ul><ul><li>Areas involved in higher intellectual reasoning and language comprehension is called WERNICKE’S AREA; </li></ul><ul><li>Layers of cell bodies of Neurons: </li></ul><ul><ul><li>Gray Matter – outermost layer; functional area; </li></ul></ul><ul><ul><li>White Matter – deeper layer; composed of fibers tracts carrying impulses to or from the cortex; form tracts or bundles that connect two parts of the cerebrum to other parts of the brain. </li></ul></ul><ul><li>The cerebral hemispheres are connected by one large fiber tract called CORPUS CALLOSUM; </li></ul>
  16. 16. <ul><li>2. Diencephalon </li></ul><ul><ul><li>Or interbrain; </li></ul></ul><ul><ul><li>Sits atop the brainstem and is enclosed by the cerebral hemispheres; </li></ul></ul><ul><ul><li>Major structures: </li></ul></ul><ul><ul><ul><ul><li>Thalamus – encloses the third ventricle , is a relay station for sensory impulses passing upward to the sensory cortex; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Hypothalamus – forms the floor of the third ventricle; is an important autonomic NS center because it plays a role in regulation of body temperature, water balance, and metabolism; also secretes oxytocin and ADH; </li></ul></ul></ul></ul>
  17. 17. <ul><li>3. Brainstem </li></ul><ul><ul><li>Is found on the lower part of the brain hidden by the cerebral hemispheres; </li></ul></ul><ul><ul><li>Provides a pathway for ascending and descending tracts; </li></ul></ul><ul><ul><li>Their nuclei form the cranial nerves and control vital activities such as breathing and BP; </li></ul></ul><ul><ul><li>RETICULAR FORMATION – is a diffuse mass that extends in the entire length of the brainstem; </li></ul></ul>
  18. 18. <ul><li>Parts of Brainstem: </li></ul><ul><li>Midbrain – contains the cerebral aqueduct of Sylvius; </li></ul><ul><ul><li>contains nuclei that act as reflex centers involved with vision and hearing; </li></ul></ul>
  19. 19. <ul><li>Parts of Brainstem….. </li></ul><ul><li>2. Pons – rounded structure that protrudes below the midbrain; </li></ul><ul><ul><li>contains many fiber tracts; </li></ul></ul><ul><ul><li>involved in control of breathing; </li></ul></ul><ul><ul><li>also contains nuclei of several cranial nerves; </li></ul></ul>
  20. 20. <ul><li>Parts of Brainstem… </li></ul><ul><li>3. Medulla Oblongata – is the most inferior part of the brainstem; </li></ul><ul><ul><li>also an important fiber tract area; </li></ul></ul><ul><ul><li>Also contains nuclei that regulate vital visceral functions; </li></ul></ul><ul><ul><li>Contains centers that control heart rate, BP, breathing, swallowing, and vomiting; </li></ul></ul>
  21. 21. <ul><li>4. Cerebellum </li></ul><ul><ul><li>Is a large, cauliflowerlike structure that projects dorsally from under the occipital lobe of the cerebrum; </li></ul></ul><ul><ul><li>Provides the precise timing or good coordination of skeletal muscle activity and controls our balance, posture, and equilibrium; </li></ul></ul><ul><ul><li>Ataxia means clumsy, disorganized movements when the cerebellum is injured; </li></ul></ul>
  22. 22. PROTECTION OF THE CNS <ul><li>because of the delicate nature of the neurons, the body provides many protective structures to protect them: </li></ul><ul><ul><ul><li>Skull </li></ul></ul></ul><ul><ul><ul><li>Vertebral Column </li></ul></ul></ul><ul><ul><ul><li>Meninges – this are three connective tissue membranes that covers and protect the CNS; </li></ul></ul></ul><ul><ul><ul><ul><ul><li>The outermost layer (DURA MATER) is a double-layered membrane that surrounds the brain; </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>The middle meningeal layer is the weblike ARACHNOID MATER; </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>The innermost layer is the PIA MATER which clings tightly to the surface of the brain and spinal cord; </li></ul></ul></ul></ul></ul>
  23. 23. <ul><li>The FALX CEREBRI is the fold of dura mater that passes transversely across the upper end of the posterior cranial fossa in the transverse fissure; </li></ul><ul><ul><li>also separates the occipital lobe of the cerebrum from the upper surface of the cerebellum; </li></ul></ul><ul><li>The SUBARACHNOID SPACE is filled with CSF; </li></ul><ul><li>ARACHNOID VILLI absorb CSF into the venous blood; </li></ul><ul><li>MENINGITIS – inflammation of the meninges; </li></ul><ul><li>ENCEPHALITIS – inflammation of the brain; </li></ul>
  24. 24. <ul><ul><ul><li>4. Cerebrospinal Fluid (CSF) </li></ul></ul></ul><ul><ul><ul><ul><li>Is a watery broth similar to blood plasma; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Formed by the CHOROID PLEXUS; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Is found in and around the brain and spinal cord which forms a watery cushion that protects these fragile structures against blows and trauma; </li></ul></ul></ul></ul><ul><li>EPIDURAL SPACE – is the interval between the dura mater and cranial bones ; in the SPINE, it is the space between the dura mater and the vertebral canal; </li></ul><ul><li>SUBDURAL SPACE – is the interval between the arachnoid and dura mater of the brain or the spinal cord; </li></ul>
  25. 25. <ul><li>FLOW OF CSF </li></ul><ul><li>CHOROID PLEXUS </li></ul><ul><li>LATERAL VENTRICLES </li></ul><ul><li>FORAMEN OF MONROE </li></ul><ul><li>THIRD VENTRICLE </li></ul><ul><li>AQUEDUCT OF SYLVIUS </li></ul><ul><li>FOURTH VENTRICLE </li></ul><ul><li>FORAMEN OF MAGENDIE AND LUSCHKA </li></ul><ul><li>SUBARACHNOID SPACE (space between the arachnoid and pia mater) </li></ul><ul><li>ARACHNOID VILLI DURAL SINUSES VENOUS SYSTEM </li></ul>
  26. 26. <ul><li>THE BLOOD BRAIN BARRIER </li></ul><ul><ul><li>the brain is very dependent on a constant environment; </li></ul></ul><ul><ul><li>separates the neurons from blood-borne substances; </li></ul></ul><ul><ul><li>composed of least permeable capillaries in the body; </li></ul></ul><ul><ul><li>water-soluble substances like water, glucose, and essential amino acids pass easily; </li></ul></ul><ul><ul><li>is virtually useless against fats, respiratory gases, and other fat-soluble molecules that diffuse easily thru all the plasma membranes; </li></ul></ul>
  27. 27. <ul><li>SPINAL CORD </li></ul><ul><ul><li>is a glistening white continuation of the brainstem; </li></ul></ul><ul><ul><li>provides a two-way conduction pathway to and from the brain; </li></ul></ul><ul><ul><li>enclosed within the vertebral or spinal column; </li></ul></ul><ul><ul><li>extends from the FORAMEN MAGNUM of the skull to the 1st or 2nd lumbar vertebra; </li></ul></ul><ul><ul><li>it is protected and cushioned by meninges; </li></ul></ul>
  28. 28. <ul><li>In humans, 31 pairs of spinal nerves arise from the cord; </li></ul><ul><li>Collection of spinal nerves at the inferior end of the vertebral canal is called CAUDA EQUINA; </li></ul>
  29. 29. <ul><li>the gray matter of the spinal cord is H-shaped and is found more interior; </li></ul><ul><li>the two posterior projections are the DORSAL or POSTERIOR HORNS for sensory functions; </li></ul><ul><li>the two anterior projections are the VENTRAL or ANTERIOR HORNS for motor function of the somatic nervous system (voluntary); </li></ul><ul><li>the LATERAL HORN is a bulge on each limb of gray substance in the thoracic and upper lumbar segments; </li></ul><ul><li>the gray matter surrounds the central canal of the cord which contains the CSF; </li></ul>
  30. 30. <ul><li>PLEXUSES: </li></ul><ul><ul><li>Cervical Plexus – on each side of the body is made up of the ventral divisions of the C1-C4; </li></ul></ul><ul><ul><ul><ul><ul><li>Supplies the skin and muscles of the scalp, neck, and part of the face; </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>The PHRENIC NERVE originates from this plexus; </li></ul></ul></ul></ul></ul><ul><ul><li>Brachial Plexus – formed by C5-T1; lies posterior to the clavicle; </li></ul></ul><ul><ul><ul><ul><ul><li>Supplies the shoulder and upper limb; </li></ul></ul></ul></ul></ul><ul><ul><li>Lumbar Plexus – formed by L1-L4; lies in the posterior abdomen in the area of the psoas muscle; supplies the FEMORAL NERVE; </li></ul></ul><ul><ul><li>Sacral Plexus – formed by L4-S3; located within the pelvis on the posterolateral wall; the largest branch is the SCIATIC NERVE; </li></ul></ul>
  31. 31. <ul><li>PERIPHERAL NERVOUS SYSTEM </li></ul><ul><ul><li>consists of nerves and scattered groups of neuronal cell bodies found outside the CNS; </li></ul></ul><ul><li>A. NERVES </li></ul><ul><ul><li>Is a bundle of neuron fibers found outside the CNS; </li></ul></ul><ul><ul><ul><li>Afferent / Sensory Nerve </li></ul></ul></ul><ul><ul><ul><li>Efferent / Motor Nerve </li></ul></ul></ul><ul><li>B. CRANIAL NERVES (CN) </li></ul><ul><ul><li>arise directly from the base of the brain (brainstem), and are not associated with the spinal cord; </li></ul></ul><ul><ul><li>The 12 pairs primarily serve the head and neck except for the CN X (vagus) which extends to the thoracic and abdominal cavities; </li></ul></ul><ul><ul><li>most cranial nerves are mixed (both motor and sensory function); </li></ul></ul>
  32. 32. <ul><ul><li>“ OOOTTAFAGVAH” </li></ul></ul><ul><li>CN I – olfactory n. II – optic n. </li></ul><ul><li> III – oculomotor n. IV – trochlear n. </li></ul><ul><li> V – trigeminal n. </li></ul><ul><li> VI – abducens n. VII – facial n. </li></ul><ul><li>VIII – auditory n. </li></ul><ul><li>IX – glossopharyngeal n X – vagus n. </li></ul><ul><li>XI – spinal </li></ul><ul><li>accessory n. </li></ul><ul><li>XII – hypoglossal n. </li></ul>“ Pls. read your book!”
  33. 33. <ul><li>AUTONOMIC NERVOUS SYSTEM </li></ul><ul><ul><li>is the motor subdivision of the PNS that controls body activities automatically; </li></ul></ul><ul><ul><li>regulates cardiac muscle activity, smooth muscle contraction, and secretion of exocrine glands; </li></ul></ul><ul><ul><li>has a chain of two motor neurons: </li></ul></ul><ul><ul><ul><li>Preganglionic axons – axons before the ganglion; leaves the CNS to synapse with the second motor neuron in a ganglion outside the CNS; </li></ul></ul></ul><ul><ul><ul><li>Postganglionic axons – the axon extends to the organ it serves; </li></ul></ul></ul>
  34. 34. <ul><li>two divisions (usually they are antagonistic) </li></ul><ul><ul><ul><li>Sympathetic NS (thoracolumbar division) – is often called the “fight-or-flight” system; </li></ul></ul></ul><ul><ul><ul><ul><li>Controls body functions that are essential for survival; </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Effects: </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Increases heart rate </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Increases BP </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Bronchial dilation </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Decreases peristalsis </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Dilated pupils </li></ul></ul></ul></ul></ul>
  35. 35. <ul><ul><ul><ul><li>Parasympathetic NS (craniosacral division) </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>is most active when the body is at rest and not threatened in any way; </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>Concerned with normal body functions, usually opposite the SNS; </li></ul></ul></ul></ul></ul>
  36. 36. <ul><li>BLOOD SUPPLY OF THE BRAIN: </li></ul><ul><ul><li>the brain is supplied by a specialized form of blood vessels called the CIRCLE OF WILLIS; </li></ul></ul><ul><ul><li>Arteries that supply the brain: </li></ul></ul><ul><ul><ul><li>internal carotid artery – branch of the common carotid artery; </li></ul></ul></ul><ul><ul><ul><li>vertebral artery – branch of the subclavian artery; </li></ul></ul></ul><ul><ul><ul><li>middle meningeal artery – branch of the external carotid artery; </li></ul></ul></ul>