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PSYC 1113 Chapter 2


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PSYC 1113 Chapter 2

  1. 1. Chapter 2:Neuroscience andBehavior
  2. 2. Neurons and SynapsesTypes of NeuronsSensory Motor Interneurons
  3. 3. SpinalCordBrainSensoryNeuronSensory Neurons• INPUT From sensory organs to thebrain and spinal cordDrawing shows asomatic neuron
  4. 4. SpinalCordBrainSensoryNeuronMotorNeuronMotor Neurons• OUTPUT From the brain and spinalcord, to the muscles and glands
  5. 5. SpinalCordBrainSensoryNeuronMotorNeuronInterneurons• Interneuronscarryinformationbetween otherneurons onlyfound in thebrain andspinal cord
  6. 6. Parts of a Neuron
  7. 7. The Cell Body– round, centrally locatedstructure– contains DNA– controls protein manufacturing– directs metabolism– no role in neural signalingContains the cell’s nucleus
  8. 8. Dendrites• Information collectors• Receive inputs from neighboringneurons• Inputs may number in thousands• If enough inputs, the cell’s AXONmay generate an output
  9. 9. Dendritic Growth• Mature neurons generally can’t divide• But new dendrites can grow• Provides room for more connections toother neurons• New connections are basis for learning
  10. 10. Axon• The cell’s output structure• One axon per cell, 2 distinct parts– tubelike structure– branches at end that connect to dendritesof other cells
  11. 11. Myelin Sheath• White fatty casing on axon• Acts as an electrical insulator• Not present on all cells• When present, increases the speed ofneural signals down the axon
  12. 12. How Neurons Communicate• Neurons communicate by means of anelectrical signal called the actionpotential• Action potentials are based on themovements of ions between the outsideand inside of the cell• When an action potential occurs, amolecular message is sent to neighboringneurons
  13. 13. Action Potential Within a Neuron
  14. 14. Resting Potential• At rest, the inside of the cell is at -70 microvolts• With inputs to dendrites, the inside becomes more positive• If resting potential rises above threshold, an action potentialstarts to travel from cell body down the axon• Figure shows resting axon being approached by an actionpotential
  15. 15. Depolarization Ahead of AP• Action potential opens cell membrane to allow sodium (Na+) in• Inside of cell rapidly becomes more positive than outside• This depolarization travels down the axon as leading edgeof the action potential
  16. 16. Repolarization Follows• After depolarization potassium (K+) moves out restoringthe inside to a negative voltage• This is called repolarization• The rapid depolarization and repolarization produce apattern called a spike discharge
  17. 17. Finally, Hyperpolarization• Repolarization leads to a voltage below the restingpotential, called hyperpolarization• Now, neuron cannot produce a new action potential• This is the refractory period
  18. 18. Neuron to Neuron• Axons branch out and end near dendritesof neighboring cells• Axon terminals are the tips of the axon’sbranches• A gap separates the axon terminals fromdendrites• Gap is called the synapse
  19. 19. Neurotransmitter Release• Action potential causes vesicle toopen• Neurotransmitter released intosynapse• Locks onto receptor molecule inpostsynaptic membrane
  20. 20. Excitatory and InhibitoryMessages• Excitatory message—increases thelikelihood that the postsynapticneuron will activate• Inhibitory message—decreases thelikelihood that the postsynapticneuron will activate
  21. 21. Locks and Keys• Neurotransmittermolecules havespecific shapes• When NT binds toreceptor, ions enter• Receptor moleculeshave binding sites
  22. 22. Some Drugs Work on Receptors• Some drugs are shapedlike neurotransmitters• Antagonists: poorly fit thereceptor and block theNT– eg, beta blockers• Agonists: fit receptorwell and act like the NT– eg, nicotine
  23. 23. Types of Neurotransmitters• Acetylcholine• Dopamine• Serotonin• Norepinephrine• GABA• Endorphins
  24. 24. Acetylcholine (Ach)• Found in neuromuscularjunctions• Involved in muscle movements• Involved in learning and memory
  25. 25. Disruptions ofAcetylcholine Functioning• Curare—blocks ACh receptors– paralysis results• Nerve gases and black widow spidervenom; too much ACh leads to severemuscle spasms and possible death
  26. 26. Disruptions ofAcetylcholine Functioning• Cigarettes—nicotine works onACh receptors– can artificially stimulate skeletal muscles,leading to slight trembling movements
  27. 27. Alzheimer’s Disease• Deterioration of memory,reasoning, and language skills• Symptoms may be due a to lossof ACh neurons
  28. 28. Dopamine• Involved in movement, attention,and learning• Dopamine imbalance alsoinvolved in schizophrenia• Parkinson’s disease is caused bya loss of dopamine-producingneurons
  29. 29. Parkinson’s Disease• Results from loss of dopamine-producingneurons in the substantia nigra• Symptoms include– difficulty starting and stopping voluntarymovements– tremors at rest– stooped posture– rigidity– poor balance
  30. 30. Parkinson’s Disease• Treatments– L-dopa– transplants of fetal dopamine-producingsubstantia nigra cells– adrenal gland transplants– electrical stimulation of the thalamus hasbeen used to stop tremors
  31. 31. Serotonin• Involved in sleep• Involved in depression–Prozac works by keeping serotoninin the synapse longer, giving itmore time to exert an effect
  32. 32. Norepinephrine• Arousal• “Fight or flight” response
  33. 33. Endorphins• Control pain and pleasure• Released in response to pain• Morphine and codeine work on endorphinreceptors; involved in healing effects ofacupuncture• Runner’s high— feeling of pleasure aftera long run is due to heavy endorphinrelease
  34. 34. GABA• Inhibition of brain activity• Huntington’s disease involvesloss of neurons in striatum thatuse GABA–Symptoms:• jerky, involuntary movements• mental deterioration
  35. 35. Summary• Neuron structure• Action potentials• Synapses• Neurotransmitters• Receptors and ions• Agonists andantagonists
  36. 36. Parts of the Nervous System• Central nervous system (CNS)–Brain and spinal cord• Peripheral nervous system (PNS)–Carries messages to and from CNS
  37. 37. Central nervoussystemPeripheralnervous system
  38. 38. Sympathetic and parasympathetic divisionsof the nervous system
  39. 39. Endocrine System• Pituitary gland—attached to the base ofthe brain, hormones affect the function ofother glands• Adrenal glands—hormones involved inhuman stress response• Gonads—hormones regulate sexualcharacteristics and reproductiveprocesses; testes in males, ovaries infemales
  40. 40. Brain• Images• Brainstem– Hindbrain– Midbrain• Forebrain– Limbic system– Cortex
  41. 41. Hindbrain Structures• Cerebellum• Brainstem– medulla– reticularformation– pons
  42. 42. Cerebellum• Coordinated,rapid voluntarymovements– playing the piano,kicking, throwing,etc.• Lesions tocerebellum– jerky, exaggeratedmovements– difficulty walking– loss of balance– shaky hands
  43. 43. Medulla• Breathing• Heart rate• Digestion• Other vitalreflexes– swallowing– coughing– vomiting– sneezing
  44. 44. Reticular Formation• Network ofneurons in thebrainstem (andthalamus)• Sleep andarousal• Attention
  45. 45. Pons• Helps coordinatemovements onleft and rightsides of the body– eg, posturalreflexes that helpyou maintainbalance whilestanding ormoving
  46. 46. Forebrain Structures• Thalamus• LimbicSystem• Cortex
  47. 47. Thalamus• Relay station inbrain• Processes mostinformation to andfrom higher braincenters
  48. 48. The Limbic System• Hypothalamus• Amygdala• Hippocampus
  49. 49. Hypothalamus• Contains nuclei involved in a varietyof behaviors– sexual behavior– hunger and thirst– sleep– water and salt balance– body temperature regulation– circadian rhythms– role in hormone secretion
  50. 50. Hypothalamus and HormonesHypothalamusreleaseshormones orreleasing factors,which in turncause pituitarygland to releaseits hormones
  51. 51. Amygdala and Emotion• Identify emotion fromfacial expressionsAmygdala damagemakes this taskdifficult.(click on picture to advance photos)
  52. 52. Cortical Specialization• Localization—notion that differentfunctions are located in different areasof the brain• Lateralization—notion that differentfunctions are processed primarily onone side of the brain or the other
  53. 53. Lobes of the Cortex• Frontal lobe—largest lobe, producesvoluntary muscle movements; involved inthinking, planning, and emotional control• Temporal lobe—primary receiving area forauditory information• Occipital lobe—primary receiving area forvisual information• Parietal lobe—processes somaticinformation
  54. 54. Language and the Brain• Aphasia—partial orcomplete inability toarticulate ideas orunderstand languagebecause of brain injury ordamage• Broca’s area—plays role inspeech production• Wernicke’s area—playsrole in understanding andmeaningful speech
  55. 55. •Split-brain operation—procedure used to reduce recurrent seizures insevere cases of epilepsy•Corpus callosum—thick band of axons that connects the two cerebralhemispheres