Nervous system sullivan CNS

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Nervous system sullivan CNS
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2011-10-11 20:29:55
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  1. NERVOUS SYSTEM
    • One of the two control and communication systems of the body
    •  Nervous system rapid, complex network
    •  Endocrine system slow/via blood
  2. The nervous system is divided into two subdivisions:
    • CENTRAL NERVOUS SYSTEM (CNS) includes the brain and spinal cord
    • PERIPHERAL NERVOUS SYSTEM (PNS)
    •  Afferent division-brings sensory information from receptors to the CNS
    •  Efferent division-carries motor commands from CNS to muscles and glands
  3. SENSORY NERVOUS SYSTEM (AFFERENT)
    • Subdivided into:
    •  Somatic sensory-caries information from skeletal muscles, joints and skin to CNS
    •  Visceral sensory-caries information from smooth muscle, cardiac muscle and gland activity
  4. MOTOR NERVOUS SYSTEM (EFFERENT)
    • Subdivided into:
    •  Somatic motor-which controls the contraction of skeletal muscles
    •  Autonomic motor- which regulates smooth, cardiac muscle and gland activity
  5. The CNS and PNS perform three general functions:
    •  Collecting information-receptors detect changes in the internal and external environment (sensory input) and send it to the CNS
    •  Processing and evaluating information-CNS determines what response is required
    •  Responding to information-CNS initiates nerve impulses (motor output) to effectors (muscles or glands)
  6. TWO TYPES OF CELLS IN THE NERVOUS SYSTEM:
    • 1. Neurons (nerve cells)-electrically excitable cells that initiate, transmit and receive nerve impulses
    • 2. Neuroglial cells-non-excitable cells that support and protect the neurons
  7. NEURONS
    • Made up of cell body and processes:
    •  Cell body (perikaryon/soma)
    •  Contains nucleus
    • (Amitotic, large nucleolus, chromosomes)
    •  Cytoplasm, mitochondria, golgi, nissl granules (ER), microtubules, and microfilaments
    •  High metabolic rate
    •  Most cells bodies in CNS
  8. 2 TYPES OF PROCESSES:
    • Dendrites
    •  Short, highly branched, unmyelinated receptive surfaces of neuron
    •  Carry information to cell body
    • Axon
    •  Long slender process arising from hillock of cell body
    •  Most are myelinated
    •  Carry information away from cell body
    •  Axon may have collateral branches
    •  Axon ending have synaptic knobs
    •  Most axons surrounded by phospholipid . . . . myelin sheath
    • 1. Neurolemmocytes-from myelin sheath on axons outside CNS
    • 2. Oligodendrocytes-from myelin sheaths on axons inside CNS
    • Myelinated axons transmit impulses faster
    • Interruptions in myelin sheath called . . . . nodes of Ranvier
  9. WITH THE DISEASE MULTIPLE SCLEROSIS
    Myelin sheaths are lacking on axons because it either doesn’t form or degenerates which interferes with transmission
  10. STRUCTUREAL TYPES OF NEURONS
    • Neurons are classified according to the number of processes coming off the cell body:
    •  Unipolar-single short process that branches like a T (sensory neurons
    •  Bipolar-two processes, one dendrite and one axon (eye, ear, and embryo)
    •  Multipolar- many dendrites and a single axon, most common of all neurons ( most motor neurons and interneuron)
  11. FUNCTIONAL TYPES OF NEURONS
    • Neurons are classified according to the direction the nerve impulse is traveling:
    •  Sensory(afferent)-transmit impulses to the CNS (from sensory receptors)
    •  Motor (efferent)-transmit impulses from the CNS (to muscle or glands)
    •  Interneurons- transmit impulses between sensory and motor neurons
  12. NEUROGLIAL CELLS
    •  Aka glia
    •  In both CNS and PNS
    •  Smaller than nerurons
    •  Physically protect and nourish neurons
    •  More numerous than neurons
    •  Capable of mitosis
    •  Brain tumors are more likely to be derived from glia than neurons
  13. NEUROGLIAL CELLS OF THE CNS
    • Four types:
    • 1. Astrocytes-blood brain barrier, support
    • 2. Ependymal cell- lines ventricles, central canal, choroid plexuses
    • 3. Microglial cell-Phagocytes
    • 4. Oligodendrocyte-myelin sheaths in CNS
  14. NEUROGLIAL CELLS OF THE PNS
    • Two types:
    • 1. Satellite cells –support/protection in ganglia
    • 2. Neurolemmocytes-myelin sheaths in PNS
    • (schwann cells)
  15. CONNECTIVE TISSUE IN NERVOUS SYSTEM
    •  Endoneurium- areolar connective tissue sheath around fiber
    •  Perineurium- dense irregular connective tissue around fasiculi
    •  Epineurium-dense irregular connective tissue with collagen fibers around whole nerve
  16. NERVES AND TRACTS
    • Nerves
    •  Contain faciculi wrapped in connective tissue
    •  In the PNS
    •  Most nerves contain both sensory and motor fibers (mixed)
    • Tracts
    •  Contains fasiculi (no connective tissue)
    •  In the CNS
    •  Tract are either sensory (ascending) or motor (descending)
    •  Types: association, commissural, projection
  17. GANGLIA AND NUCLEI
    • Ganglia
    •  Clusters of cells bodies in PNS
    • Nuclei
    •  Clusters of neuron cell bodies in CNS
  18. NERVE IMPULSE TRANSMISSION
    •  Mechanism by which neurons carry signals
    •  Nearly all body cells have and electrical difference between the outside and the inside of their cell membranes
    •  Due to this electrical potential difference nerve cells (and muscle cells) are excitable
    •  Neurons can be excited by stimulation of sensory receptors and by other neurons
    •  When a neuron is stimulated the electrical difference across the cell membrane is altered
    •  This alteration is propagated along the length of the neuron as a . . . nerve impulse
  19. NEUROTRANSMITTERS
    •  Neurotransmitters (chemicals) transmit impulse across synapse (the space between two neurons) from a presynaptic neuron to postsynaptic neuron
    •  Neurotransmitters are stored in synaptic vesicles in axon endings of presynaptic neuron
  20. SOME NEUROTRANSMITTERS IN THE BODY
    •  Acetylcholine
    •  Epinephrine
    •  Norepinepherine
    •  Dopamine
    •  Endorphins/enkephalins
    •  Serotonin
    •  Gamma aminobutyric acid (gaba)
  21. EMBRYONIC DEVELOPMENT OF THE BRAIN
    • 4th week 5th week
    • Prosencephalon
    • (Forebrain) Telencephalon
    • Diencephalon
    • Mesencephalon
    • (midbrain) Mesencephalon
    • Rhombencephalon
    • (hindbrain) Metencephalon
    • Myelencephalon
  22. EMBRYONIC AREAS
    • 1. Telencephalon-forms the cerebrum
    • 2. Diencephalon-forms thalamus, hypothalamus, epithalamus
    • 3. Mesencephalon-forms the midbrain
    • 4. Metencephalon-forms the pons and cerebellum
    • 5. Myelencephalon-forms the medulla oblongata
  23. BRAIN
    • Gray matter:
    •  Interneuron and motor neuron cell bodies
    •  Forms the cortex that covers the surface of the adult brain
    •  Also makes up neuron clusters called cerebral nuclei in CNS
    • White matter:
    •  Made up of myelinated axons
    •  Lies deep to the gray matter of the cortex
  24. CRAINIAL MENINGES
    • Connective tissue layers that:
    •  Separates the brain from the cranium
    •  Enclose and protects blood vessels brain
    •  Contain and circulate cerebrospinal fluid (CSF)
    •  Form some of the veins (sinuses) that drain blood from the brain
  25. Three meninges are:
    •  Dura mater
    •  Arachnoid
    •  Pia mater
  26. DURA MATER
    •  Tough mother
    •  Dense irregular connective tissue
    •  Outermost meninx, double layered
    • 1. Outer . . . periosteal dura
    • 2. Inner . . . meningeal dura
    •  Space between the two layers of dura creates veins filled with blood called . . . dural sinuses
    •  Dura terminates at level of 2nd sacral vertebra
  27. ARACHNOID MATER
    •  Delicate avasular connective tissue with collagen/elastic fibers
    •  Between pia/dura maters
    •  Subarachnoid space (space under arachnoid) is filled with CSF
    •  Folds in arachnoid mater called villi function as 1 way passageways to allow CSF to diffuse from subarachnoid space into the blood in the dural sinuses
  28. PIA MATER
    •  Soft mother
    •  Thin, transparent, areolar connective tissue
    •  Innermost, delicate, vascular
    •  Follows contour of brain
    •  Pia mater, capillaries and ependymal cells together make up the choroid plexuses (which produce CSF)
  29. VENTRICLES
    •  Four cavities within the brain
    •  Continuous with one another and with the central canal of the cord
    •  Ventricles contain cerebrospinal fluid
  30. VENTRICLES IN THE BRAIN
    • Lateral ventricles (2)
    •  One in each hemisphere of the cerebrum
    •  Separated by a thin septum pellucidum
    •  Interventricular foramina (foramina of Monro) connect to 3rd
    • Third ventricle
    •  In the diecephalon
    •  Cerebral aqueduct (mesencephalon/aqueduct of Sylvius)
    • Fourth ventricle
    •  Between pons and cerebellum
    •  Median and lateral (2) apertures (foramina of Magendie and Luschka) connect to subarachnoid space
    •  Also connects to central canal of cord
  31. CEREBROSPINAL FLUID (CSF)
    •  Formed by an ultrafiltration process from choroid plexuses in the roof of ventricles
    •  Circulates inside the brain (in ventricles) and outside the brain in subarachnoid space (between arachnoid and pia mater)
    •  Reabsorbed into arachnoid villi then into dural sinuses (returned to venous circulation
    •  CNS contains 150ml of CSF
    •  500ml CSF produced/reabsorbed each day
    •  Clear, colorless fluid similar to plasma (except more Na+, Cl-, no protein)
    •  CSF functions to cushion and protect the brain
    •  CSF carries nutrients and metabolic waste to/from nervous tissue
    •  CNS “floats” in CSF
  32. CEREBRUM
    •  2 cerebral hemispheres
    •  Tracts (bundles of axons) allow communication between hemispheres
    •  Corpus callosum
    •  Convolutions (gyri/sulci) central and lateral
    •  Deep groves called fissures
    •  Cerebral cortex (gray matter/ white matter)
    •  Longitudinal fissure between hemispheres
    •  Falx cerebri
    •  Lateral ventricles
  33. Basal nuclei are clusters of neurons found deep within white matter of cerebrum
    • Basal nuclei:
    •  Provide subconscious control and integration of skeletal muscles tone
    •  Coordination of learned movement patterns
    •  Process, integrate and relay information from cerebral cortex to thalamus
    •  Caudate nucleus, amygdaloid body, lentiform nucleus (putamen and globus pallidus)
  34. The two hemispheres appear as anatomic mirror images but they display some functional differences, termed hemisphere lateralization.
    •  Left hemisphere. . . . categorical hemisphere (language, analytical, math, etc.)
    •  Right hemisphere. . . Representational hemisphere (imagination, music, art, etc)
    • However, both hemispheres are in constant communication via corpus callosum
  35. CEREBRAL HEMISPHERE
    • Divided into five lobes:
    • 1. Frontal lobe . . . . . .voluntary motor function, decision making
    • verbal communication and personality
    • 2. Parietal lobe . . . . . .general sensory functions
    • 3. Temporal lobe . . . .hearing and smelling
    • 4. Occipital lobe . . . . processes incoming visual information
    • 5. Insula . . . . . . . . . . memory and taste
    •  Motor areas . . . . . . . . .frontal lobe
    •  (control skeletal muscles)
    •  Sensory areas . . . . . . . parietal, occipital, temporal lobes and insula
    •  (sensations)
    •  Association areas . . . . frontal, occipital, parietal and temporal lobes
    •  (integrate information)
  36. DIENCEPHALON
    • Components of the diencephalon include:
    •  Epithalamus
    •  Thalamus
    •  Hypothalamus
  37. EPITHALAMUS
    •  Roof of diencephalon
    •  Pineal gland which secretes the hormone melatonin to regulate day-night cycles
  38. THALAMUS
    •  Pair of oval masses on each side of 3rd ventricle connect via intermediate mass
    •  Between cerebral hemispheres
    •  Gray matter
    •  Relay station for sensory information projecting to somatosensory cortex
    •  All sensory impulses except olfactory converge on thalamus and synapse
  39. HYPOTHALAMUS
    •  Anterior inferior to thalamus
    •  Lower sidewalls and floor of 3rd ventricle
    •  Infundibulum (stalk) extends inferiorly to attach to the pituitary gland
    •  Control of the ANS and endocrine system
    •  Produces, releasing, and inhibitory factors
    •  Produces oxytocin and antidiuretic hormone
    •  Controls behavior, food, and water intake
    •  Controls body temperature
    •  Controls sleep-wakefulness
  40. LIMBIC SYSTEM
    •  Structures that form a ring (limbus) around the diencephalon
    •  The limbic system is composed of nuclei and tracts that collectively process and experience emotions
    •  Cingulated gyrus, hippocampus, amygdaloid body, fornix, nuclei, etc
  41. BRAINSTEM
    • Three regions form the brainstem:
    • 1. Midbrain (mesencephalon)
    • 2. Pons
    • 3. Medulla oblongata
  42. MIDBRAIN
    •  Dorsal midbrain consists of 4 rounded elevations:
    •  Corpora quadrigemina. . . .
    •  Superior colliculi-visual reflex centers
    •  Inferior colliculi-auditory reflex centers
    • Trochlear nerve (IV) emerges dorsally, just bellow corpora
  43. Ventral midbrain consists of . . .
    •  Cerebral peduncles
    •  . . . which are descending motor axons
    • Ocularmotor nerve(III) emerges ventrally
    • Cerebral aqueducts run thru midbrain
    • Nuclei of cranial nerves (III) and (IV) in midbrain
  44. PONS
    •  Rounded bridge on underside of brainstem
    •  Sensory and motor tracts in pons connect brain to cord
    •  Contains the pneumotaxic and apneustic centers . . .
    •  . . . regulates rate/depth of breathing and influence respiratory center of medulla
    •  Nuclei for cranial nerves V, VI, VII, some of VIII
  45. MEDULLA OBLONGATA
    •  Most inferior part of the brainstem which continues with the spinal cord inferior
    •  Fourth ventricle to central canal of cord
    •  All tracts ascend/descend thru medulla
    •  Pyramids on ventral surface are motor tracts. Some tracts in medulla decussate. (so motor areas on one side of cortex control muscles on other side of body)
    •  Nuclei of cranial nerves VII, IX, X, XI, XII
    • Medulla oblongata . . .contains several autonomic nuclei which group to form three important centers
    •  Cardiac center-regulates heart rate and strength of contraction
    •  Vasomotor center-controls blood pressure by regulating the contraction and relaxation of smooth muscle in the walls of arterioles
    •  Respiratory center-reglates respiratory rate. Influenced by the apneustic and pneumotaxic centers of the pons
    • Other nuclei-coughing, sneezing, salivation, swallowing, gaging, and vomiting
  46. CEREBELLUM
    •  2nd largest part of the brain
    •  Behind cerebrum
    •  Highly convoluted surface
    •  2 cerebellar hemispheres
    •  Cortex/gray matter
    •  Arbor vitae/white matter
    •  Three pairs of cerebellar peduncle connect cerebellum to midbrain, pons and medulla
  47. CEREBELLAR FUNCTION
    •  Coordinates skeletal muscle movements for smooth, coordinated movements
    •  Stores learned movement patterns
    •  Maintains equilibrium and posture
    •  Receives proprioceptive (sensory) information from the muscle
    • and joints to regulate body position
    •  Monitors the position of joints and muscle tone
  48. SPINAL CORD
    •  18 inches in length
    •  CNS below the medulla
    •  Passes thru vertebral canal of vertebrae
    •  Extends from foramen magnum to level of 1st or 2nd lumbar vertebra
    •  Serves as link between brain and the rest of body
  49. FUNCTIONS
    •  Pathway (sensory/motor impulses
    •  Spinal reflexes
  50. GROSS ANATOMY OF THE SPINAL CORD
    •  Spinal cord is shorter than the vertebral canal
    •  Tapering inferior end of the spinal cord is called the conus medullaris (usally at the level of the first/second lumbar vertebra)
    •  Inferior to the conus medullaris group of axons called cauda equine project inferiorly from the spinal cord
    •  Within the cauda equine is the filum terminale which is a thin strand of pia mater (anchors conus medullaris to coccyx)
  51. Spinal cord…is separated into 2 regions
    • Inner…gray matter
    • Outer…white matter
    • Gray matter—dendrites and cell bodies of neurons, unmyelinated axons, and glial cells
    • White matter—myelinated axons
  52. GRAY MATTER
    •  Anterior horn: contains cell bodies of somatic neurons which innervate skeletal muscle
    •  Lateral horn: found only in the T1-L2 of the spinal cord. Contains cells bodies of autonomic motor neurons which innervate cardiac muscle, smooth muscle and glands
    •  Posterior horn: contains axons of sensory neurons and cell bodies of interneurons
  53. WHITE MATTER
    • The white matter of the spinal cord is external to the gray matter and is partitioned into three areas called funiculi:
    •  Posterior
    •  Lateral
    •  Anterior
  54. Axons within each funiculus = tracts
    A tract + its nucleus is called a …pathway
  55. PATHWAY
    • Pathways are ascending and descending
    •  Ascending pathways……carry sensory information from the body to the brain
    •  Descending pathways……transmit motor information from the brain to muscles or glands

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