Chapter 14 Part 2

1. Chapter 14Part 2 The Brain and Cranial Nerves Lecture Outline

2. Cerebrum (Cerebral Hemispheres) • Cerebral cortex is gray matteroverlying white matter • 2-4 mm thick containing billions of cells • grew quickly; formed folds(gyri) and grooves (sulci or fissures) • Longitudinal fissure separates left & right cerebral hemispheres • Corpus callosum is a commisure (band of white matter) connecting left and right cerebral hemispheres • Each hemisphere is subdivided into 4 lobes Principles of Human Anatomy and Physiology, 11e

3. Lobes • Each cerebral hemisphere is further subdivided into four lobes by sulci or fissures (Figure 14.11 a,b) • frontal, parietal, temporal, and occipital. • A fifth part of the cerebrum, the insula, lies deep to the parietal, frontal, and temporal lobes and cannot be seen in an external view of the brain. Principles of Human Anatomy and Physiology, 11e

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5. Longitudinal fissure (green) Frontal lobe Central sulcus (yellow) precentral & postcentral gyrus Parietal lobe Parieto-occipital sulcus Occipital lobe Lateral sulcus (blue) Temporal lobe Insula Lobes and Fissures Principles of Human Anatomy and Physiology, 11e

6. Insula within Lateral Fissure Principles of Human Anatomy and Physiology, 11e

7. White Matter • The white matter is under the cortex and consists of myelinated axons running in three principal directions (Figure 14.12). • Association fibers connect and transmit nerve impulses between gyri in the same hemisphere. • Commissural fibers connect gyri in one cerebral hemisphere to the corresponding gyri in the opposite hemisphere. • Projection fibers form ascending and descending tracts that transmit impulses from the cerebrum to other parts of the brain and spinal cord. Principles of Human Anatomy and Physiology, 11e

8. Cerebral White Matter • Association fibers between gyri in same hemisphere • Commissural fibers from one hemisphere to other • Projection fibers form descending & ascending tracts Principles of Human Anatomy and Physiology, 11e

9. Basal Ganglia The basal ganglia are paired masses of gray matter in each cerebral hemisphere (Figure 14.13). • Connections to red nucleus, substantia nigra & subthalamus • Input & output with cerebral cortex, thalamus & hypothalamus • Control large automatic movements of skeletal muscles Principles of Human Anatomy and Physiology, 11e

10. Deep Structures Principles of Human Anatomy and Physiology, 11e

11. Caudate nucleus • Lentiform and cuadate nuclei are known as the corpus striatum. • Nearby structures functionally linked to the basal ganglia are the substantia nigra and the subthalamic nuclei. • They are responsible for helping to control muscular movements. • Damage to the basal ganglis results in tremor, rigidity, and involuntary muscle movements. In Parkinson’s disease neurons from the substantia nigra to the putamen and cuadate nucleus degenerate. • Basal ganglia also help initiate and terminate some cognitive processes. Obsessive compulsive disorder, schizophrenia, chronic anxiety are thought to involve dysfunction of the circuits between the basal ganglis and limbic system Principles of Human Anatomy and Physiology, 11e

12. Limbic System • The limbic system is found in the cerebral hemispheres and diencephalon (Figure 14.14). • limbic lobe • dentate gyrus • amygdala • septal nuclei • mammilary bodies, mammilothalmic tract • anterior and medial nuclei of the thalamus, • olfactory bulbs • fornix, stria terminalis, stria medulllaris, • medial forebrain bundle • It functions in emotional aspects of behavior and memory, and is associated with pleasure and pain. Principles of Human Anatomy and Physiology, 11e

13. Limbic System • Emotional brain--intense pleasure & intense pain • Strong emotions increase efficiency of memory Principles of Human Anatomy and Physiology, 11e

14. Brain Injuries • Brain injuries are commonly associated with head injuries and result, in part, from displacement and distortion of neuronal tissue at the moment of impact and in part from the release of disruptive chemicals from injured brain cells. • Various degrees of brain injury are described by the terms • concussion, contusion, and laceration. Principles of Human Anatomy and Physiology, 11e

15. Brain Injuries • Causes of damage • displacement or distortion of tissue at impact • increased intracranial pressure • infections • free radical damage after ischemia • Concussion---temporary loss of consciousness • headache, drowsiness, confusion, lack of concentration • Contusion--bruising of brain (less than 5 min unconsciousness but blood in CSF) • Laceration--tearing of brain (fracture or bullet) • increased intracranial pressure from hematoma Principles of Human Anatomy and Physiology, 11e

16. Sensory Areas • The sensory areas of the cerebral cortex are concerned with the reception and interpretation of sensory impulses. • Some important sensory areas include • primary somatosensory area, • primary visual area, • primary auditory area, and • primary gustatory area Principles of Human Anatomy and Physiology, 11e

17. Sensory Areas of Cerebral Cortex Receive sensory information from the thalamus Primary somatosensory area = postcentral gyrus = 1,2,3 Primary visual area = 17 Primary auditory area = 41 & 42 Primary gustatory area = 43 Principles of Human Anatomy and Physiology, 11e

18. Motor Areas • The motor areas are the regions that govern muscular movement. • Two important motor areas are • primary motor area and • Broca’s speech area. (Figure 14.15) Principles of Human Anatomy and Physiology, 11e

19. Motor Areas of Cerebral Cortex • Voluntary motor initiation • Primary motor area = 4 = precentral gyrus • controls voluntary contractions of skeletal muscles on other side • Motor speech area = 44 = Broca’s area • production of speech -- control of tongue & airway Principles of Human Anatomy and Physiology, 11e

20. Association Areas of Cerebral Cortex • Somatosensory area = 5 & 7 (integrate & interpret) • Visual association area = 18 & 19 (recognize & evaluate) • Auditory association area(Wernicke’s) = 22(words become speech) • Gnostic area = 5,7,39 & 40 (integrate all senses & respond) • Premotor area = 6 (learned skilled movements such as typing) • Frontal eye field =8 (scanning eye movements such as phone book) Principles of Human Anatomy and Physiology, 11e

21. Association Areas • The association areas are concerned with complex integrative functions such as memory, emotions, reasoning, will, judgment, personality traits, and intelligence. (Figure 14.15) • Injury to the association or motor speech areas results in aphasia, an inability to use or comprehend words. (Clinical Application) Principles of Human Anatomy and Physiology, 11e

22. Aphasia Language areas are located in the left cerebral hemisphere of most people Inability to use or comprehend words = aphasia • nonfluent aphasia = inability to properly form words • know what want to say but can not speak • damage to Broca’s speech area • fluent aphasia = faulty understanding of spoken or written words • faulty understanding of spoken or written words • word deafness = an inability to understand spoken words • word blindness = an inability to understand written words • damage to common integrative area or auditory association area Principles of Human Anatomy and Physiology, 11e

23. Hemispheric Lateralization • Although the two cerebral hemispheres share many functions, each hemisphere also performs unique functions. • hemispheric lateralization (Figure 14.16). • The left hemisphere is more important for right-handed control, spoken and written language, and numerical and scientific skills. • The right hemisphere is more important for left-handed control, musical and artistic awareness, space and pattern perception, insight, imagination, and generating mental images of sight, sound, touch, taste, and smell. • Table 14.3 summarizes some of the distinctive functions that are more likely to reside in the left or right hemisphere. Principles of Human Anatomy and Physiology, 11e

24. Hemispheric Lateralization • Functional specialization of each hemisphere more pronounced in men • Females generally have larger connections between 2 sides • Damage to left side produces aphasia • Damage to same area on right side lead to speech with little emotional inflection Principles of Human Anatomy and Physiology, 11e

25. Brain Waves • An EEG may be used to diagnose epilepsy and other seizure disorders, infectious diseases, tumors, trauma, hematomas, metabolic abnormalities, degenerative diseases, and periods of unconsciousness and confusion; it may also provide useful information regarding sleep and wakefulness. • An EEG may also be one criterion in confirming brain death (complete absence of brain waves in two EEGs taken 24 hours apart). • Figure 14.17 shows four kinds of brain waves that can be recorded from normal individuals. Principles of Human Anatomy and Physiology, 11e

26. Electroencephalogram (EEG) • Brain waves are millions of nerve action potentials in cerebral cortex • diagnosis of brain disorders (epilepsy) • brain death (absence of activity in 2 EEGs 24 hours apart) • Alpha -- awake & resting • Beta -- mental activity • Theta -- emotional stress • Delta -- deep sleep Principles of Human Anatomy and Physiology, 11e

27. II -- Optic Nerve • Connects to retina supplying vision Principles of Human Anatomy and Physiology, 11e

28. I -- Olfactory Nerve • Extends from olfactory mucosa of nasal cavity to olfactory bulb • Sense of smell Principles of Human Anatomy and Physiology, 11e

29. Developmental Anatomy of the NS • Begins in 3rd week • ectoderm forms thickening (neural plate) • plate folds inward to form neural groove • edges of folds join to form neural tube • Neural crest tissue forms: • spinal & cranial nerves • dorsal root & cranial nerve ganglia • adrenal gland medulla • Layers of neural tube form: • marginal layer which forms white matter • mantle layer forms gray matter • ependymal layer forms linings of cavities within NS Principles of Human Anatomy and Physiology, 11e

30. Dorsal View of Neural Groove Principles of Human Anatomy and Physiology, 11e

31. Development of Principal Parts • By end of 4th week, 3 anterior enlargements occur • prosencephalon • mesencephalon • rhombencephalon Principles of Human Anatomy and Physiology, 11e

32. Development of Principal Parts • By 5th week, 5 enlarged areas exist • Prosencephalon • telencephalon • diencephalon • Mesencephalon • Rhombencephalon • metencephalon • myelencephalon • Neural tube defects • associated with low levels of folic acid (B vitamins) • spina bifida is failure to close of vertebrae • anencephaly is absence of skull & cerebral hemispheres Principles of Human Anatomy and Physiology, 11e

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34. Aging & the Nervous System • Years 1 to 2 • rapid increase in size due to increase in size of neurons, growth of neuroglia, myelination & development of dendritic branches • Early adulthood until death • brain weight declines until only 93% by age 80 • number of synaptic contacts declines • processing of information diminishes • conduction velocity decreases • voluntary motor movements slow down • reflexes slow down Principles of Human Anatomy and Physiology, 11e

35. DISORDERS: HOMEOSTATIC IMBALANCES • The most common brain disorder is a cerebrovascular accident (CVA or stroke). • Third leading cause of death after heart attacks and cancer • CVAs are classified into two principal types: • ischemic (the most common type), due to a decreased blood supply • hemorrhagic, due to a blood vessel in the brain that bursts. • Common causes of CVAs are intracerebral hemorrhage, emboli, and atherosclerosis. • Tissue plasminogen activator (t-PA) used within 3 hours of ischemic CVA onset will decrease permanent disability Principles of Human Anatomy and Physiology, 11e

36. Transient Ischemic Attack (TIA) • Episode of temporary cerebral dysfunction • Cause • impaired blood flow to the brain • Symptoms • dizziness, slurred speech, numbness, paralysis on one side, double vision • reach maximum intensity almost immediately • persists for 5-10 minutes & leaves no deficits • Treatment is aspirin or anticoagulants; artery bypass grafting or carotid endarterectomy Principles of Human Anatomy and Physiology, 11e

37. Alzheimer Disease (AD) • Dementia = loss of reasoning, ability to read, write, talk, eat & walk • Afflicts 11% of population over 65 • Great loss of neurons in specific regions (e.g., hippocampus and cerebral cortex); loss of neurons that release acetylcholine • Plaques of abnormal proteins deposited outside neurons (amyloid plaques). • Tangled protein filaments within neurons (neurofibrillary tangles). Principles of Human Anatomy and Physiology, 11e

38. Tumors • Brain tumor is an abnormal growth of tissue it may be malignant or benign. • Attention Deficit Hyperactivity Disorder (ADHD) is a laerning disorder characterized by poor attention span, hyperactivity and inappropriate impulsiveness. Principles of Human Anatomy and Physiology, 11e

39. CRANIAL NERVE Review • Twelve pairs of cranial nerves originate from the brain (Figure 14.5) • named primarily on the basis of distribution and numbered by order of attachment to the brain. • Some cranial nerves (I, II, and VIII) contain only sensory fibers and are called sensory nerves. The rest are mixed nerves because they contain both sensory and motor fibers. • Figures 14.18 – 14.27 illustrate the distribution of many of the cranial nerves. • Table 14.4 presents a summary of cranial nerves, including clinical applications related to their dysfunction. Principles of Human Anatomy and Physiology, 11e

40. Cranial Nerve Review Principles of Human Anatomy and Physiology, 11e

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