Neurons brain edited


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Neurons brain edited

  1. 1. Neurons and the BrainMA. LEA A. RONDA, Ph.D.1
  2. 2. Organization of the Nervous System A. Divisions of the nervous system i. There are two major divisionsCentral nervous system All neurons in the brain and spinal cordPeripheral nervous system Consists of the nerves connecting thebrain and spinal cord to the other partsof the body2
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  39. 39. The Central Nervous System Brain Spinal cord A collection of neuronsand supportive tissuerunning from the base ofthe brain down thecenter of the back. Protected by spinalcolumn.39
  40. 40. The Withdrawal Reflex40
  41. 41. Peripheral Nervous System Somatic Includes the nerves that are connected to sensoryreceptors and skeletal muscles. Carries messages to and from the sense receptor musclesand surface of the body Autonomic The sympathetic nervous system mobilizes bodilyresources and increases the output of energy duringemotion and stress. The parasympathetic nervous system operates duringrelaxed states and that conserves energy Connects with the internal organs and glands41
  42. 42.  ii. The sensory nerves of the somaticsystem transfer information aboutexternal stimuli from the skin, muscles,and joints to the CNS iii. The motor nerves of the somaticsystem carry impulses from the centralnervous system to the muscles iv. Most of the nerve fibers connectingthe brain to the body are located in thespinal cord42
  43. 43. Organization of the Nervous System43
  44. 44. Communication in the Nervous System The structure of the neuron Different kinds of neurons How neurons communicate Action potential Chemical messengers in the nervous system Neurotransmitters Major neurotransmitters Endorphins Endocrine system Hormones44
  45. 45. NEURONS – the basic elementsof behavior Nerve cells The building blocks of the nervoussystem A specialized cell that transmit neuralimpulses to other neurons, glands andmuscles45
  46. 46. Structure of a Neuron Dendrites - a cluster of fibers atone end of a neuron receive information fromother neurons and transmittowards the cell body. Cell body keeps the neuron alive anddetermines whether it willfire.46
  47. 47.  Axon extending fiber thatconducts impulses awayfrom the cell body andtransmits to other cells. Terminal buttonssmall bulges at the end ofaxons that send messages toother neurons47
  48. 48.  Nerve Bundle of axonsbelonging to manyneuronsNucleus a group of cell bodiesin the brain and spine Ganglion A group of cellbodies outside thebrain and spine Glial cells Nonneuronal cellsthat hold theneurons in placeand remove deadneurons and wasteproductsStructure of a Neuron48
  49. 49. Structure of a Neuron Myelin Sheath Fatty insulation that may surround the axon of aneuron.49
  50. 50.  Myelin sheath A protective coat of fat and protein that wrapsaround the axon Serves to increase the velocity with whichelectrical impulses travel through axons “if your hand touches a painfully hot stove,the information regarding the pain is passedthrough axons in the hand and arm that have arelatively thick coating of myelin sheath,speeding the message of pain so that you canreact instantly.50
  51. 51. Different Kinds of Neurons51
  52. 52. Neurons in the News Canadian research has provided evidencefor neurogenesis: the production of newneurons from immature stem cells. Stem cells are immature cells that renewthemselves and have the potential todevelop into mature cells; givenencouraging environments, stem cells fromearly embryos can develop into any celltype.52
  53. 53. How Neurons Communicate Axon terminals releaseneurotransmitter. Neurotransmitter enterssynaptic gap. Neurotransmitter bindsto receptors that it fits.53
  54. 54. Action Potential A brief change in electrical voltage which occursbetween the inside and outside of an axon when aneuron is stimulated. It produces an electricalimpulse.54
  55. 55. Action Potential An electrochemical impulse that travelsfrom the cell body down to the end of theaxon Occurs because the cell membrane issemipermeable When a neuron is not generating an actionpotential it is a resting neuron and ionpumps keep sodium ion out of the cellmaintaining the resting membrane potential55
  56. 56.  When a neuron is stimulated, it isdepolarized, sending sodium ions into thecell The myelin sheath speeds the signaldown the neuron, allowing forsalutatory conduction in which thenerve impulse jumps from one gap tothe next These gaps are called nodes of Ranvier56
  57. 57.  Synaptic transmission i. A neuron fires an action potential when thestimulation reaching it exceeds a certainconsistent threshold ii. The all-or-none principle says that actionpotentials are constant and occur only if thethreshold is reached iii. When an action potential reaches thesynaptic terminals it stimulated the synapticvesicles which cross the synapse and bind toreceptors57
  58. 58.  ReceptorsThese are proteins lodged in thedendritic membrane of the receivingor postsynaptic neuronThe neurotransmitter and receptorhave to match in order to effect thereceiving cell and cause it fire58
  59. 59.  iv. If a neurotransmitter is not usedimmediately, it is cleared from the synapsethrough reuptake, in which it is reabsorbedby the synaptic terminal where it wasreleased v. The neurotransmitter may also gothrough degradation, in which enzymes insynaptic gap react with theneurotransmitter to break it up chemicallyand make it inactive59
  60. 60. Neurotransmitter A chemical substance that is released by atransmitting neuron at the synapse and thatalters the activity of a receiving neuron.60
  61. 61. Major Neurotransmitters Serotonin Dopamine Acetylcholine (ACh) Norepinephrine Gamma amino butryic acid (GABA) Glutamate Endorphins61
  62. 62. Acetylcholine i. Found at many synapses and is usuallyexcitatory ii. Prevalent in the hippocampus wherememories are formed Has a role in Alzheimer’s diseaseiii. Released at every synapse where a neuronterminates at a skeletal muscle fiber Directed onto end plates located on themuscle cells which cause them to contract62
  63. 63. Norepinephrine Part of the monoamines and is producedmainly in the brain stem Cocaine and amphetamines prolong theaction of norepinephrine leading to elevatedmood states Lithium speeds up norepinephrine reuptakeleading to depressed mood63
  64. 64. Dopamine Similar to norepinephrine and relatedto feelings of pleasure Too much dopamine may causeschizophrenia and too little isassociated with Parkinson’s disease64
  65. 65. Serotonin Plays an important role in theregulation of mood, sleep and appetite Antidepressant drugs, called serotoninreuptake inhibitors, increase serotoninlevels65
  66. 66. Glutamate An excitatory neurotransmitter ispresent in neurons of the centralnervous system Believed to play a role in learningand memory66
  67. 67. GABA A major inhibitory transmitter used inthe majority of synapses in the brain Used as anxiety reducing drugs67
  68. 68. Opioids and Substance P68
  69. 69. Mapping the Brain Lesion method Electroencephalogram (EEG) Transcranial magnetic stimulation (TMS) Positron-Emission tomography (PET) Magnetic resonance imaging (MRI)69
  70. 70. Mapping the Brain Lesioning Involves damaging and removing sections ofbrain in animals, then observing their effects. Transcranial magnetic stimulated (TMS) Stimulates brain cells using a powerfulmagnetic field produced by a wire coil placedon the head. Can be used to temporarily inactivate neuralcircuits.70
  71. 71. Electroencephalogram (EEG) A recording of neural activity detected byelectrodes.71
  72. 72. Positron Emission Tomography (PET) A method for analyzing biochemical activity in thebrain, using injections of a glucose-like substancecontaining a radioactive element. Active areas haveincreased blood flow. Sensors detectradioactivity. Different tasks showdistinct activity patterns.72
  73. 73. Magnetic Resonance Imaging (MRI) Method for studying body andbrain tissue. Magnetic fields align certainions and compounds. When field is removed, thesemolecules release energy asradio waves. Computer calculates tissuedensity from radio waves. Provides clear, 3D images.73
  74. 74. A Walk Through the Brain The brain stem The cerebellum The thalamus The hypothalamus and the pituitary gland The amygdala The hippocampus The cerebrum and lobes of the cerebral cortex74
  75. 75. Organization of the brain Three regions based on location HindbrainIncludes structures located in theposterior part of the brain MidbrainLocated in the middle of the brain ForebrainAnterior part of the brain75
  76. 76.  Three concentric layers of the brain The central core Known as the brain stem controls involuntaryand primitive behaviors Includes all structures in the hindbrain andmidbrain as well as the thalamus andhypothalamus Limbic system Control emotion Cerebrum Regulates higher intellectual process76
  77. 77. The Brain Stem Pons involved in sleeping, waking anddreaming. Medulla A narrow structure responsible forcertain automatic functions such asbreathing and heart rate. Reticular activating system (orformation) arouses cortex and screens incominginformation. Important role in controlling arousaland in the ability to focus attention 77
  78. 78. The Cerebellum Regulates movement andbalance and learning newmotor responses Involved in rememberingsimple skills and acquiredreflexes. Plays a part in analyzingsensory information,solving problems andunderstanding words.78
  79. 79. The Thalamus Acts as sensory relay station,directing information from thesense receptors to the cerebrum Relays sensory messages to thecerebral cortex. Includes all sensory messagesexcept those from olfactory bulb. Also important for control ofsleep and wakefulness79
  80. 80. Pituitary GlandHypothalamus and Pituitary Gland Involved in emotions and drives vital tosurvival including fear, hunger, thirst,and reproduction. Plays a role in the sensation of emotionsand responses to stress Also regulates autonomic nervoussystem. Controls the production of hormones Regulates endocrine activity to maintainhomeostasis- process that maintains thenormal level of functioningcharacteristic of a healthy organism80
  81. 81.  The pituitary gland is asmall endocrine glandwhich releases hormonesand regulates otherendocrine glands.81Pituitary Gland
  82. 82. The Limbic system A set of structures closely interconnectedwith the hypothalamus that imposeadditional controls over instinctivebehaviors regulated by the hypothalamusand brain stem Contains the hippocampus and amydala Involved in emotional behavior82
  83. 83. The Amygdala Responsible for arousaland regulation of emotionand the initial emotionalresponse to sensoryinformation. Plays important role inmediating anxiety anddepression. Regulated emotions suchas fear83
  84. 84. The Hippocampus Responsible for thestorage of newinformation in memory. Compares informationwith what the brain hascome to expect aboutthe world. “Gateway to memory”because it enables us tonavigate through theenvironment.84
  85. 85. The Cerebrum Largest brain structure. Consists of upper part of brain and divided intotwo cerebral hemispheres which are connectedby the corpus callosum. In charge of most sensory, motor and cognitiveprocesses. Surrounded by cerebral cortex, a collection ofseveral thin layers of cells (gray matter).85
  86. 86. The Cerebrum The outer layer is the cerebral cortex Composed of two hemispheres on the leftand right sides connected by the corpuscallosum Each hemisphere is divided into fourlobes-the frontal, parietal, occipital andtemporal86
  87. 87. Lobes of the Cerebral Cortex Occipital lobes Visual cortex. Parietal lobes Somatosensory cortex. Temporal lobes Memory, perception, emotion and auditory cortex. Left lobe, Wernicke’s area. Frontal lobes Emotion, planning, creative thinking and motor cortex. Left lobe, Broca’s area.87
  88. 88.  Primary motor area Controls voluntary movement of the body Primary somatosensory area Located in the parietal lobe, controls heat,cold, touch, pain, and sense of bodymovement Primary visual area Primary auditory area88
  89. 89. Lobes of the Cerebral Cortex89
  90. 90. Phineas Gage Gage was a railroadconstruction foreman An 1848 explosion forceda steel tamping rodthrough his head Others said he was “…nolonger Gage…” Lost his job, worked as asideshow exhibit90
  91. 91. The Corpus Callosum Millions of myelinatedaxons connecting thebrain’s hemispheres. Provides a pathway forcommunication betweenthe hemispheres. If surgically severed fortreatment of epilepsy,hemispheres cannotcommunicate directly.91
  92. 92. Split-Brain Experiment92
  93. 93. Split-Brain Experiment Subjects were presented information to one or theother side of their brains. Patients identified verbally the pictures to the right(i.e., boy). When asked to point to the face seen, the patientspointed to the left picture.93
  94. 94. Where Is the Self? Most scientists assume that what we call “mind,”“consciousness,” self-awareness,” or “subjectiveexperience” can be explained in physical terms as aproduct of the brain. Some contend that the brain consists ofindependent modules and that the self is anillusion. No one understands yet how subjective experienceis linked to physical processes in the brain.94
  95. 95. Are There “His” and “Hers” Brains? After analyzing 49 studies of sex differences inbrain anatomy, Canadian researchers found smalldifferences between the two groups and largerdifferences within groups. There does appear to be sex differences inlateralization of language. Males show lefthemisphere activation only. Females, left andright. There also appears to be differences in amountsof grey matter. Females have more.95
  96. 96. 3 Ways to Interpret These Findings These supposed differences are stereotypes. A biological difference does not necessarilyhave implications for behaviour orperformance. Sex differences in the brain could be the resultrather than the cause of behaviouraldifferences.