ANA 113Exam # 2 Study Guide: Lectures 13-25, 28-29Lecture 13: Nervous System Histology- Human Nervous Systemo Central Nervous System (CNS) Brain Spinal Cordo Peripheral Nervous System (PNS) Somatic (voluntary) Autonomic (involuntary) Both brain and spinal cord contain components of autonomic nervous system- Functional Classificationo Sensory (afferent) – delivers information to the CNSo Motor (efferent) – carries information to the peripheryo Associative (interferon) – located between sensory and motor neurons; modifies responses of other neurons- Structural Classificationo Multipolar – found throughout the brain and spinal cordo Bipolar – found in the retina of the eye and inner earo Unipolar – found in ganglia (clusters) that are adjacent to spinal cord- Neuron Structureo Cell body Contains most of the organelles typically found in cells – mitochondria, Golgi complex, nucleus, etc. No centrioles, so does not undergo mitosis Nissi Bodies (chromatophilic bodies) – clusters of free ribosomes that produce protein and RER Neurofibrils – represent the cytoskeleton; helps maintain the shape of the cell bodyo Processes Dendrites – more than one per neuron and transmits information to the cell body Axon (nerve fiber) – only one per neuron that transmits information from the cellbodyo Special Nerve Fiber Characteristics Myelin sheath – produced by oligodendrocytes (CNS) and Schwann cells (PNS); composed of lipid; conducts electrical impulse  Neurilemma – cell wall of oligodendrocyte and Schwann cell Nodes of Ranvier – area of axon not covered by myelin Synaptic vesicles - store various neurotransmitters that are released at the synapseo CNS Neuroglia Oligodendrocytes – produces a myelin covering around nerve fibers (axons)  Microglia – phagocytic cell that ingests dead or damaged tissue Astrocyte – assists in the nourishment of neurons and helps to form the blood-brain barrier Blood-Brain Barrier – composed of astrocyte, basement membrane, and endothelial cell wall of capillary; regulates what substances pass from blood to CNS Ependymal cells – line the cavities/ventricles of the braino PNS Neuroglia Schwann cells – produce a myelin covering around nerve fibers Satellite cells – regulate nourishment to neuronso Terminology Nuclei – cluster of neurons in CNS Ganglia (Ganglion) – cluster of neurons in PNS Nerve – bundles of axons in PNS Tract – bundles of axons in CNS- Communicationo Synapse – site of communication between neurons Pre-synaptic neuron – located before the clef Synaptic Clef – space between neurons Post-synaptic neuron – located afer the clefo Conduction of Nerve Impulse Continuous conduction – impulse travels in a continuous flow along an axon Saltatory conduction – impulse jumps or is transmitted from one Node of Ranvierto another- Nerve Fiberso A – most heavily myelineated; facilitates sharp paino B – intermediate in amount of myelino C – least amount of myelin or no myelin; facilitates dull pain - Neurotransmitterso Excitatory – cause depolarization of postsynaptic neuron Acetylcholine (Ach) – controls skeletal muscle Norepinephrine (NE) – controls autonomic nervous system Serotonin – plays a role in sleep Dopamine – a decrease in this may cause schizophrenia o Inhibitory – hyperpolarizes the postsynaptic neuron preventing transmission of the nerve impulse across the synapse Gamma Aminobutyric Acid (GABA) – inhibits cerebellum Enkephalins – effects mimicked by heroin/morphine Endorphins – effect mimicked by heroin/morphine Dopamine – found in autonomic systemLecture 14: Spinal Cord- Gross Anatomyo Located in vertebral canalo Extent – foramen magnum to intervertebral disc between L1 and L2o Conus medullaris – cone shaped terminal part of spinal cordo cauda equine (“horse’s tail”) – composed of nerve fibers (axons)o Filum terminale – from tip of conus medularis to sacrum; connective tissue fiber composed of pia matero Cervical and lumbar enlargements – thickened regions of spinal cord that control upper and lower limbs; cervical is bigger because upper body has finer movements- Coveringso Meninges – membranes that envelop the CNS Dura mater – outermost layer; tough as parchment Arachnoid – very thin middle layer; like cellophane Pia mater – connective tissue that touches spinal cord and braino Subarachnoid space – deep to arachnoid; between arachnoid and pia; contains cerebrospinal fluid (CSF)o CSF – produced in ventricles of the brain; clear, colorless and odorless fluido Epidural space – located external to dura mater; contains fato Subdural space – located internal to dura mater; normally, there is nothing found here; arachnoid pressed against durao Meningitis – inflammation (infection) of the meninges (usually arachnoid and pia mater)o Spinal tap/lumbar puncture Usually done between vertebrate L3-L4 or L4-L5 Iliac crest is used to locate vertebrate Skin  subcutaneous  ligament  dura mater  arachnoid mater- Spinal segmentso 31 segments Cervical – 8 Thoracic – 12 Lumbar – 5 Sacral – 5 Coccygeal – 1o White matter – composed of fibers; bundles of axons = tractso Gray matter – contains cell bodies of neuronso Ventral gray horn – contains motor neuron cell bodieso Ventral roots – contains motor fiberso Dorsal root ganglion – contains sensory neuron cell bodieso Dorsal root – contains sensory nerve fiberso Spinal nerve – dorsal (sensory) and ventral (motor) root - Reflexes and the Reflex Archo Withdrawal reflex – requires 2 synapses Receptor Sensory neuron Interneuron Motor neuron Effector (muscle) o Stretch reflex – requires 1 synapse  Receptor Sensory neuron Motor neuron EffectorLecture 15: Peripheral Nervous System- Sensory receptors o Photoreceptors – responsive to light; rods and cones located in the retina of the eyeo Chemoreceptors – respond to chemical stimulio Pain receptors – free nerve endings in the skin; respond to paino Thermoreceptors – located in the skin; respond to changes in temperature o Pressure receptors – located in the skin; respond to mechanical deformation Meissner (Tactile) corpuscles – sense light pressure Pacinian (Lamellar) corpuscles – sense deep pressureo