1. Chapter 8 Lecture Outline
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2. Chapter 8 outline Structural organization of the brain Cerebrum
Diencephalon
Midbrain and hindbrain
Spinal cord tracts
Cranial and spinal nerves
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3. Structural Organization of the Brain
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4. Structure Organization of the Brain
Consists of brain and spinal cord
Receives input from sensory neurons
Directs activity of motor neurons
Association neurons integrate sensory and motor activity
Perform learning and memory
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5. CNS continued CNS composed of gray and white matter
Gray matter consists of neuron bodies and dendrites
White matter (myelin) consists of axon tracts
Adult brain weighs 1.5kg
Contains 100 billion neurons
Receives 20% of blood flow to body
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6. Embryonic Development
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7. Embryonic Development
Neural tube forms from groove in ectoderm by 20th day
Becomes the CNS
Neural crest cells develop where tube fuses
Become ganglia of PNS
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8. Embryonic Development continued
During 4th week, 3 swellings form on neural tube
These will become forebrain, midbrain and hindbrain
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9. Embryonic Development continued
During 5th week: Forebrain elaborates into telencephalon and diencephalon
Midbrain does not subdivide
Hindbrain forms metencephalon and myelencephalon
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10. Embryonic Development continued
Telencephalon grows disproportionately forming hemispheres of cerebrum
Ventricles and central canal are remnants of hollow part of neural tube
Contain cerebral spinal fluid (CSF)
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11. Cerebrum
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12. Cerebrum Is largest part of brain (80% of mass)
Is responsible for higher mental functions
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13. Cerebrum continued
Its right and left hemispheres are interconnected by tract of the corpus callosum
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14. Cerebral Cortex Is highly convoluted
An elevated fold is called a gyrus
A depressed groove is called a sulcus
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15. Cerebral Cortex continued
Each hemisphere has 5 lobes: frontal, parietal, temporal, occipital and insula
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16. Cerebral Cortex continued
Frontal lobe is separated from parietal by central sulcus
Precentral gyrus of frontal lobe is involved in motor control
Postcentral gyrus of parietal lobe receives sensory info from areas controlled by precentral gyrus
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17. Cerebral Cortex continued
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18. Cerebral Cortex continued
Temporal lobe contains auditory centers; receives sensory info from cochlea
Also links and processes auditory and visual info
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19. Cerebral Cortex continued
Occipital lobe is responsible for vision and coordination of eye movements
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20. Cerebral Cortex continued
Insula plays role in memory encoding
Integrates sensory info with visceral responses
Assesses bodily states that accompany emotions
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21. Visualizing the Brain
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22. Visualizing the Brain
X-ray computed tomography (CT) visualizes soft tissues
Positron-emission tomography (PET) is used to examine brain metabolism and blood flow, drug distribution
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23. Visualizing the Brain continued
Magnetic resonance imaging (MRI) shows brain function
in the image below
Functional MRI (fMRI) shows areas with increased neural activity by tracking blood flow
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24. Electroencephalogram (EEG)
Measures electrical activity of cerebral cortex
Used to diagnose epilepsy and brain death
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25. EEG Waves
Alpha waves are recorded from parietal and occipital lobes with person awake, relaxed, eyes closed
Beta waves are strongest from frontal lobes; evoked by visual stimuli and mental activity
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26. EEG Waves continued Theta waves come from temporal and occipital lobes
Common in newborns
In adults indicates severe emotional stress
Delta waves are from cerebral cortex
Common during adult sleep and in awake infants
In awake adult indicates brain damage
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27. Sleep 2 types of sleep are recognized REM - rapid eye movement
EEGs are similar to awake ones
Type when dreaming occurs
Non-REM has delta waves
Appears to be crucial for consolidation of short- into long-term memory
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28. Functional Specializations of the Brain
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29. Cerebral Nuclei
Are distinct masses of cell bodies located deep inside cerebrum
Function in control of voluntary movement
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30. Cerebral Nuclei continued
Have reciprocal excitatory connections with the cerebral cortex that create a motor circuit
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31. Cerebral Lateralization
Refers to specialization of each hemisphere for certain functions
Each cerebral hemisphere controls movement on opposite side of body
And receives sensory info from opposite side of body
Hemispheres communicate thru the corpus callosum (Fig 8.1) which contains about 200 million fibers
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32. Cerebral Lateralization continued
Left hemisphere possesses language and analytical abilities
Right hemisphere is best at visuospatial tasks
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33. Language Language areas of brain are known mostly from aphasias
= speech and language disorders due to brain damage
Broca’s area is necessary for speech
Wernicke’s area is involved in language comprehension
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34. Limbic System and Emotion
The hypothalamus and limbic system (shown in green) are crucial for emotions
Including aggression, fear, feeding, sex and goal-directed behaviors
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35. Learning and Memory
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36. Memory Includes short- and long-term memory
Involves a number of regions in brain
There are two types of long-term memory
Non-declarative (explicit) includes memories of simple skills and conditioning
Declarative (implicit) includes verbal memories
Amnesiacs have impaired declarative memory
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37. Memory continued Hippocampus is critical for acquiring new memories
And consolidating short- into long-term memory
Amygdala is crucial for fear memories
Storage of memory is in cerebral hemispheres
Higher order processing and planning occur in prefrontal cortex
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38. Long-Term Potentiation (LTP)
Glutamate activates AMPA and NMDA postsynaptic receptors in hippocampus
Promotes an inc. in Ca2+ concent. in cytoplasm
needed for LTP to be induced
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39. Long-Term Potentiation (LTP) continued
Post-synaptic neuron also receive input from other presynpatic neurons (release GABA)
GABA’s inihibiton lessened by another retrograde messenger prod. by post-synaptic neuron
endocannabinoid as retrograde messenger
stim. by depolarization (by glutamate)
effect termed—depolariztion-induced suppression of inhibition
may also effect LTP
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40. Neurogenesis in Hippocampus
Appears to be crucial for learning and memory
Hippocampus contains neural stem cells that continually produce new neurons (neurogenesis)
Stress or depression impede learning and cause hippocampus to shrink
Stress reduction and antidepressants return size to normal
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41. Brain Structures and their Functions
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42. Thalamus and Epithalamus
Are located at base of cerebral hemispheres
Thalamus is a relay center thru which all sensory info (except olfactory) passes to cerebrum
And plays role in level of arousal
Epithalamus contains the choroid plexus which secretes CSF
Also contains pineal gland which secretes melatonin
Involved in sleep cycle and seasonal reproduction
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43. Hypothalamus Is most important structure for homeostasis
Contains neural centers for hunger, thirst, body temperature
Regulates sleep, emotions, sexual arousal, anger, fear, pain and pleasure
Controls hormone release from anterior pituitary
Produces ADH and oxytocin
Coordinates sympathetic and parasympathetic actions
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44. Pituitary Gland Is divided into anterior and posterior lobes
Posterior pituitary stores and releases ADH (vasopressin) and oxytocin
Both made in hypothalamus and transported to pituitary
Hypothalamus produces releasing and inhibiting hormones that control anterior pituitary hormones
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45. Circadian Rhythms Are body's daily rhythms
Regulated by SCN (suprachiasmatic nucleus) of hypothalamus
SCN is the master clock
Adjusted daily by light from eyes
Controls pineal gland secretion of melatonin which regulates circadian rhythms
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46. Midbrain Contains: Superior colliculi -- involved in visual reflexes
Inferior colliculi -- relay auditory information
Red nucleus and substantia nigra -- involved in motor coordination
S. nigra dopamine neurons degenerate in Parkinson’s
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47. Midbrain continued
Mesolimbic dopamine neurons are involved in reward and addiction
Abused drugs cause dopamine release from the nucleus accumbens
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48. Hindbrain
Contains pons, cerebellum and medulla
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49. Respiratory Control Centers in Brain Stem
Contains several nuclei of cranial nerves
And 3 important respiratory control centers
Apneustic and pneumotaxic centers in pons
Rhythmicity center
in medulla oblongata
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50. Cerebellum
2nd largest structure in brain containing 50 billion neurons
Receives input from proprioceptors (joint, tendon and muscle receptors)
Involved in coordinating movements along with cerebral nuclei and motor areas of cortex
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51. Medulla Contains all tracts that pass between brain and spinal cord
nuclei of cranial nerves
And several crucial centers for breathing and cardiovascular systems (vital centers)
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52. Reticular Activating System (RAS)
Is an ascending arousal system that originates in groups of neurons in the pons, midbrain reticular formation, hypothalamus and basal forebrain
These project to the cerebral cortex and control its level of arousal
Activation of the RAS promotes wakefulness; inhibition promotes sleep
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53. Spinal Cord
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54. Spinal Cord Tracts
Sensory info from body travels to brain in ascending spinal tracts
Motor activity from brains travels to body in descending tracts
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55. Ascending Spinal Tracts
Ascending sensory tracts decussate (cross) so that brain hemispheres receive info from opposite side of body
Same for most descending motor tracts from brain
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56. Descending Spinal Tracts
Are divided into 2 major groups:
Pyramidal (or corticospinal) tracts descend from cerebral cortex to spinal cord without synapsing
Originate in motor cortex
Function in control of fine movements
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57. Descending Spinal Tracts continued
Extrapyramidal (or Reticulospinal) tracts descend with many synapses
Influence movement indirectly
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58. Descending Spinal Tracts continued
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59. Peripheral Nervous System
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60. Peripheral Nervous System (PNS)
Consists of nerves that exit from CNS and spinal cord, and their ganglia (= collection of cell bodies outside CNS)
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61. Cranial Nerves Consists of 12 pairs of nerves
2 pairs arise from neurons in forebrain
10 pairs arise from midbrain and hindbrain neurons
Most are mixed nerves containing both sensory and motor fibers
Table 8.7 Summary of Cranial Nerves
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62. Spinal Nerves
Are mixed nerves that separate next to spinal cord into dorsal and ventral roots
Dorsal root composed of sensory fibers
Ventral root composed of motor fibers
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63. Spinal Nerves continued
There are 31 pairs:
8 cervical pairs,
12 thoracic pairs,
5 lumbar pairs,
5 sacral pairs,
1 coccygeal pair
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64. Reflex Arc
Is a simple sensory input, motor output circuit involving only peripheral nerves and spinal cord
Sometimes arc has an association neuron between sensory and motor neuron
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