1. Chapter 15 The Brain and Cranial Nerves

2. The Brain The average male adult brain weighs about 3.5 lbs. The average male adult brain weighs about 3.5 lbs. Composed of 3 divisions: Composed of 3 divisions: Cerebrum = Cerebral cortex and Basal nuclei Cerebrum = Cerebral cortex and Basal nuclei Cerebellum – posterior and inferior to cerebrum Cerebellum – posterior and inferior to cerebrum Brainstem: Diencephalon (Thalamus, Hypothalamus and Epithalamus), Midbrain (superior and inferior colliculi), Pons and Medulla oblongata Brainstem: Diencephalon (Thalamus, Hypothalamus and Epithalamus), Midbrain (superior and inferior colliculi), Pons and Medulla oblongata

5. Brain Meninges

6. Arachnoid villi Absorbs CSF back into venous sinuses and blood

7. Brain Ventricles Cavities within the cerebrum and brain stem where cerebrospinal fluid (CSF) is manufactured and circulated. Cavities within the cerebrum and brain stem where cerebrospinal fluid (CSF) is manufactured and circulated. Two lateral ventricles over thalamus and roll out into temporal lobes, medial third and fourth ventricles joined by cerebral aqueduct. Two lateral ventricles over thalamus and roll out into temporal lobes, medial third and fourth ventricles joined by cerebral aqueduct. Lateral ventricles look like a Rocky Mountain sheep Rams horns and communicate to third ventricle via interventricular foreamen. Lateral ventricles look like a Rocky Mountain sheep Rams horns and communicate to third ventricle via interventricular foreamen. CSF is formed by the ependymal cells of choroid plexus in all four ventricles; is an ultrafiltrate of blood- no cells present; high in Na and K. CSF is formed by the ependymal cells of choroid plexus in all four ventricles; is an ultrafiltrate of blood- no cells present; high in Na and K. CSF circulates through ventricular system as well as central canal of spinal cord and subarachnoid space around brain and spinal cord. CSF circulates through ventricular system as well as central canal of spinal cord and subarachnoid space around brain and spinal cord.

8. Brain Ventricles

11. CSF formation and circulation into and from blood vascular system. CSF formation and circulation into and from blood vascular system. CSF provides protection and nourishment to the brain and spinal cord. CSF provides protection and nourishment to the brain and spinal cord. Has higher levels of Na and K than blood. Has higher levels of Na and K than blood. CSF reduces weight of brain (1400 gm to 50 gm). CSF reduces weight of brain (1400 gm to 50 gm).

13. Cerebrum Cerebrum composes the vast majority of the brain mass (80%). It is divided into 2 halves or hemispheres, a right and a left hemisphere. Cerebrum composes the vast majority of the brain mass (80%). It is divided into 2 halves or hemispheres, a right and a left hemisphere. Longitudinal fissure- midsagittal groove dividing the two hemispheres into a right and left side. Longitudinal fissure- midsagittal groove dividing the two hemispheres into a right and left side. Consists of an outer layer of gray matter over white matter (like crust on white bread). Consists of an outer layer of gray matter over white matter (like crust on white bread). Sulci and gyri = valleys and ridges on surface of cerebral hemispheres. Sulci and gyri = valleys and ridges on surface of cerebral hemispheres. Five lobes: Frontal, parietal, occipital, temporal and insula. Five lobes: Frontal, parietal, occipital, temporal and insula.

14. Brain blood flow and barrier Blood flow to the brain is provided by the internal carotid arteries and the vertebral arteries. Blood flow to the brain is provided by the internal carotid arteries and the vertebral arteries. The blood brain barrier (BBB) is thought to be due to specialized endothelial cells that are influenced by the glial astrocytes. The blood brain barrier (BBB) is thought to be due to specialized endothelial cells that are influenced by the glial astrocytes. In the choroid plexus there is also a CSF-BBB formed by the ependymal cells. In the choroid plexus there is also a CSF-BBB formed by the ependymal cells. The BBB is absent in some places of the 3 rd and 4 th ventricles at patches called circumventricular organs where some substances may pass into the brain tissue. The BBB is absent in some places of the 3 rd and 4 th ventricles at patches called circumventricular organs where some substances may pass into the brain tissue.

16. Cerebral Cortex The cortex is the outer layer of the cerebrum is composed of gray matter and is where our “consciousness” is located. The cortex is the outer layer of the cerebrum is composed of gray matter and is where our “consciousness” is located. It allows us to be who we are, perceive sensations, comprehend and understand, as well as learn and, communicate with the ability to act and react at a conscious level. It allows us to be who we are, perceive sensations, comprehend and understand, as well as learn and, communicate with the ability to act and react at a conscious level.

17. Sulcus or Sulci sulcus/sulci – the valleys or grooves found between the gyri. Some of these also have specific names. sulcus/sulci – the valleys or grooves found between the gyri. Some of these also have specific names. central sulcus – separates the frontal and parietal lobes.. central sulcus – separates the frontal and parietal lobes.. lateral sulcus – separates the temporal lobe from the parietal/ frontal lobes. lateral sulcus – separates the temporal lobe from the parietal/ frontal lobes. parieto-occipital sulcus – separates the parietal and occipital lobes. parieto-occipital sulcus – separates the parietal and occipital lobes.

19. Gyrus or Gyri gyrus/gyri – the elevated ridges of tissue in the cortex gyrus/gyri – the elevated ridges of tissue in the cortex 1. precentral gyrus- motor cortex area 4 1. precentral gyrus- motor cortex area 4 2. post central gyrus- sensory cortex areas 1-3 2. post central gyrus- sensory cortex areas 1-3 - homunculus (little man)- portrays motor and sensory areas of body overlaying precentral and postcentral gyri of the cortex - homunculus (little man)- portrays motor and sensory areas of body overlaying precentral and postcentral gyri of the cortex

20. Sulci and Gyri

21. Humunculus “little man”

22. Functional areas of the Cortex Three important areas of cortex Motor areas control voluntary movement. Motor areas control voluntary movement. Sensory areas provide consciousness and awareness of sensations. Sensory areas provide consciousness and awareness of sensations. Association areas act mainly to integrate diverse information into decisive and meaningful actions. This is done via interneurons or association neurons. Association areas act mainly to integrate diverse information into decisive and meaningful actions. This is done via interneurons or association neurons.

23. Cortical motor, sensory and association areas

24. Motor Areas of Cerebral Cortex 1° (primary) Motor Cortex – located in the precentral gyrus.Also known as Broadmann’s area # 4. 1° (primary) Motor Cortex – located in the precentral gyrus.Also known as Broadmann’s area # 4. -Contains large Pyramidal neurons that allow us to perform precise and skilled movements with our skeletal muscles. -Motor innervation is contralateral i.e. the left side of the brain controls the right side of the body and vice versa. Broca’s Area – located superior to lateral sulcus and anterior to precentral gyrus. Associated with motor speech and is usually located in the left hemisphere Broca’s Area – located superior to lateral sulcus and anterior to precentral gyrus. Associated with motor speech and is usually located in the left hemisphere Premotor cortex anterior to precentral gyrus (Broadmann 6). Premotor cortex anterior to precentral gyrus (Broadmann 6). thought to be site of memory bank for fine motor skils.

25. Sensory Areas of Cerebral Cortex 1° (primary) Somatosensory Cortex – located in the postcentral gyrus of the parietal lobe. Areas 1-3 1° (primary) Somatosensory Cortex – located in the postcentral gyrus of the parietal lobe. Areas 1-3 Visual Sensory Area – Located on the extreme posterior tip of the occipital lobe. Receives input from retina; is largest cortical sensory area. Visual Sensory Area – Located on the extreme posterior tip of the occipital lobe. Receives input from retina; is largest cortical sensory area. Auditory Area – medial aspects of the temporal lobes. Auditory Area – medial aspects of the temporal lobes. Gustatory Area –parietal lobe deep to the temporal lobe at the tip of the tongue of humunculus. Gustatory Area –parietal lobe deep to the temporal lobe at the tip of the tongue of humunculus.

26. Cerebral anatomy to know Longitudinal and transverse fissures Longitudinal and transverse fissures Lateral, Central and Parieto-occipital sulci Lateral, Central and Parieto-occipital sulci Precentral (motor #4) and Postcentral (sensory #1-3) gyri Precentral (motor #4) and Postcentral (sensory #1-3) gyri Lobes: Frontal, Parietal, Temporal, Occipital and Insula Lobes: Frontal, Parietal, Temporal, Occipital and Insula Basal nuclei: Caudate nucleus, Putamen, Globus pallidus Basal nuclei: Caudate nucleus, Putamen, Globus pallidus Corpus callosum, septum pellucidum, fornix, and internal capsule Corpus callosum, septum pellucidum, fornix, and internal capsule

27. Cerebral anatomy to know White matter is myelinated neuronal tissue in brain and spinal cord and contains neuronal tracts. White matter is myelinated neuronal tissue in brain and spinal cord and contains neuronal tracts. Gray matter is unmyelinated and contains mostly neuronal nuclear groups or nuclei and unmyelinated tracts. Gray matter is unmyelinated and contains mostly neuronal nuclear groups or nuclei and unmyelinated tracts.

28. Coronal section

29. Cerebral White Matter is composed of myelinated processes. Within the white matter are “roads” of ordered groups of neuron processes called tracts. There are three major types of tracts in the cerebral cortex: is composed of myelinated processes. Within the white matter are “roads” of ordered groups of neuron processes called tracts. There are three major types of tracts in the cerebral cortex: 1. Commissural fibers – connect the gray matter between the two hemispheres. e.g. corpus callosum 2. Association fibers – connect adjacent gyri in same hemisphere. e.g. visual and auditory association areas. 3. Projection fibers – these connect to regions outside of the cerebrum e.g. internal capsule; corona radiata

30. Communication fibers

32. Basal Nuclei “Corpus striatum” Masses of cerebral gray matter buried deep in each hemisphere in the white matter and lateral to the thalamus. Masses of cerebral gray matter buried deep in each hemisphere in the white matter and lateral to the thalamus. Caudate nucleus, globus pallidus and putamen Caudate nucleus, globus pallidus and putamen Communicate with cortex in controlling movement Communicate with cortex in controlling movement Complete function is ??, but may regulate start, stop and intensity of voluntary body movements from cortical levels. Complete function is ??, but may regulate start, stop and intensity of voluntary body movements from cortical levels.

33. Basal Nuclei “Corpus striatum”

34. The Limbic System Concerned with sense of smell in association with long term memory and emotional responses (anger, fear, rage, sex and hunger). Concerned with sense of smell in association with long term memory and emotional responses (anger, fear, rage, sex and hunger). Includes cingulate gyrus, amygdala, hippocampus, septum, fornix, thalamus, hypothalamus and olfactory bulbs. Includes cingulate gyrus, amygdala, hippocampus, septum, fornix, thalamus, hypothalamus and olfactory bulbs.

35. The Limbic System

36. Diencephalon Thalamus is sensory relay nucleus from spinal cord and brainstem regions to the cerebral cortex. Located at top of brainstem, each half is joined by intermediate mass. Thalamus is sensory relay nucleus from spinal cord and brainstem regions to the cerebral cortex. Located at top of brainstem, each half is joined by intermediate mass. Hypothalamus nuclear group just inferior to thalamus consisting of ~ 12 nuclei. Third ventricle is roof. Hypothalamus nuclear group just inferior to thalamus consisting of ~ 12 nuclei. Third ventricle is roof. -Main visceral control center for many systems: regulates ANS, GI, cardiovascular centers, sleep/wake, emotions, behavior, hunger/thirst, body temp, memory, sex drive and endocrine system. Epithalamus pineal gland and habenula produce melatonin for sleep/wake. Epithalamus pineal gland and habenula produce melatonin for sleep/wake.

37. Diencephalon, Midbrain, Pons and Medulla

39. Hypothalamus

40. Epithalamus -Pineal gland -Habenular nuc.

41. Cerebral and Diencephalon Functions

42. Brain stem (see Figure 15.7; p. 422) Extends from posterior border of diencephalon to the beginning of spinal cord at foreamen magnum. Extends from posterior border of diencephalon to the beginning of spinal cord at foreamen magnum. Consists of Midbrain, Pons, and Medulla oblongata Consists of Midbrain, Pons, and Medulla oblongata -controls automatic behavior of systems necessary for life (e.g. cardiovascular, respiratory, emetic, etc.) -passageway for all tracts to cerebrum and spinal cord -contains nuclei of many cranial nerves to face and neck Has same pattern of gray/white matter as spinal cord (i.e. white matter surrounds gray matter) Has same pattern of gray/white matter as spinal cord (i.e. white matter surrounds gray matter)

43. Brain Stem (Lateral view)

44. Brain Stem (Diencephalon, Midbrain and Hindbrain)

45. Midbrain Lies between a plane that extends from behind pineal gland down to posterior end of mamillary bodies and caudally to the rostral part of the pons. Lies between a plane that extends from behind pineal gland down to posterior end of mamillary bodies and caudally to the rostral part of the pons. Central cavity is cerebral aqueduct with tectum (roof) dorsally and cerebral peduncles ventrally. Central cavity is cerebral aqueduct with tectum (roof) dorsally and cerebral peduncles ventrally. Periaqueductal gray is involved in fight or flight (Sympathetic) Periaqueductal gray is involved in fight or flight (Sympathetic) Contains copra quadrigemina (sup & inf colliculi) which are relay nuclei for vision and hearing, respectively. Contains copra quadrigemina (sup & inf colliculi) which are relay nuclei for vision and hearing, respectively. Other nuclei include substantia nigra and red nucleus Other nuclei include substantia nigra and red nucleus Contains nuclei for occulomotor (CN-III) and trochlear (CN- IV). Contains nuclei for occulomotor (CN-III) and trochlear (CN- IV).

46. Midbrain/Pons (X-section)

47. Midbrain/Hindbrain (lateral view)

48. Reticular Formation Composed of 100’s of small gray nuclei that extend from medulla, pons and midbrain and project up to the diencephalon, cerebellum and cerebrum. Composed of 100’s of small gray nuclei that extend from medulla, pons and midbrain and project up to the diencephalon, cerebellum and cerebrum. It receives diverse input and sends a continuous stream of information to cerebral cortex keeping it alert to all activity during sleep and consciousness. It is often referred to as the reticular activating system (RAS). It receives diverse input and sends a continuous stream of information to cerebral cortex keeping it alert to all activity during sleep and consciousness. It is often referred to as the reticular activating system (RAS). The motor portion sends neurons to the spinal cord via reticulospinal tracts. The motor portion sends neurons to the spinal cord via reticulospinal tracts. Functions include cardiovascular control, pain control, Functions include cardiovascular control, pain control, breathing, swallowing, and habituation to environment.

49. Reticular Formation

50. Pons Bulging region on inferior surface of brain stem. Bulging region on inferior surface of brain stem. Lies between the midbrain and medulla oblongata. Lies between the midbrain and medulla oblongata. Forms a bridge between left and right halves of cerebellum. Forms a bridge between left and right halves of cerebellum. Fourth ventricle separates pons from cerebellum. Fourth ventricle separates pons from cerebellum. Cranial nerves V (trigeminal), VI (abducens), and VII (facial) arise from pontine nuclei. Cranial nerves V (trigeminal), VI (abducens), and VII (facial) arise from pontine nuclei. Middle cerebellar peduncles carry fibers from Pons to cerebellum. Middle cerebellar peduncles carry fibers from Pons to cerebellum.

51. Pons

52. Pons (lateral view)

53. Medulla oblongata Extends from Pons to spinal cord Extends from Pons to spinal cord Pyramids (pyramidal tracts) decussate (crossover) at caudal border and are motor corticospinal tracts. Pyramids (pyramidal tracts) decussate (crossover) at caudal border and are motor corticospinal tracts. Cranial nerves VIII (vestibulocochlear), IX (glossopharyngeal), X (Vagus), XI (accessory) and XII (hypoglossal) arise from medullary nuclei near fourth ventricle. Cranial nerves VIII (vestibulocochlear), IX (glossopharyngeal), X (Vagus), XI (accessory) and XII (hypoglossal) arise from medullary nuclei near fourth ventricle. Visceral centers for cardiac, vasomotor and respiratory centers are in medulla. Visceral centers for cardiac, vasomotor and respiratory centers are in medulla.

54. Medulla oblongata

56. Cerebellum Cauliflower-like looking mass at posterior part of brain and dorsal to the pons and medulla. Cauliflower-like looking mass at posterior part of brain and dorsal to the pons and medulla. Coordinates and smoothes body movements, and maintains posture and equilibrium. Coordinates and smoothes body movements, and maintains posture and equilibrium. Two lateral hemispheres are connected by vermis Two lateral hemispheres are connected by vermis Hemispheres subdivided into 3 lobes: Hemispheres subdivided into 3 lobes: 1. anterior, 2. posterior and 3. flocculonodular Anterior and posterior coordinate movements Anterior and posterior coordinate movements Flocculonodular adjusts posture and equilibrium Flocculonodular adjusts posture and equilibrium

57. Cerebellum Has three regions: Outer cortical gray matter, Inner white matter (arbor vitae) and Deep cerebellar nuclei. Has three regions: Outer cortical gray matter, Inner white matter (arbor vitae) and Deep cerebellar nuclei. Cerebellar cortical nuclei function to smooth body movements. Cerebellar cortical nuclei function to smooth body movements. White matter contains tracts that carry information to White matter contains tracts that carry information to and from cerebral cortex. and from cerebral cortex. Deeper nuclei relay instructions to other areas of brain from cerebellar cortex to refine body movements. Deeper nuclei relay instructions to other areas of brain from cerebellar cortex to refine body movements.

58. Cerebellum Cerebellar cortex receives 3 forms of information : Cerebellar cortex receives 3 forms of information : 1). Equilibrium, 2). Position of muscles in limbs, neck and trunk and 3). Info from cerebral cortex. 1). Equilibrium, 2). Position of muscles in limbs, neck and trunk and 3). Info from cerebral cortex. Cerebellar peduncles are fibers tracts that connect cerebellum with different parts of brain. Cerebellar peduncles are fibers tracts that connect cerebellum with different parts of brain. Unlike cerebral motor outflow which is contralateral, cerebellar outflow is ipsilateral (same side). Unlike cerebral motor outflow which is contralateral, cerebellar outflow is ipsilateral (same side).

59. Cerebellum

60. Cerebellum

61. Cranial Nerves Twelve pairs of cranial nerves arise from nuclei in brain and migrate out of cranium to innervate peripheral organs. Twelve pairs of cranial nerves arise from nuclei in brain and migrate out of cranium to innervate peripheral organs. First 2 pairs arise from forebrain, the remainder come from brainstem nuclei First 2 pairs arise from forebrain, the remainder come from brainstem nuclei They are numbered in Roman numerals I thru XII. They are numbered in Roman numerals I thru XII. All cranial nerves except for X innervate head and neck. All cranial nerves except for X innervate head and neck. Cranial nerve X (Vagus) innervates head, neck, thorax and abdomen. Cranial nerve X (Vagus) innervates head, neck, thorax and abdomen.

62. Cranial Nerves I Olfactory nerve (S)VII Facial (B) II Optic nerve (S) VIII Vestibulochochlear (S) III Occulomotor (M) IX Glossopharyngeal (B) IV Trochlear (M) X Vagus (B) V Trigeminal (B) XI Accessory (M) VI Abducens (M) XII Hypoglossal (M) Oh, Oh, Oh To Touch And Feel Velvet, Good Vibrations And Harmony.

64. I. Olfactory nerves (S) I. Olfactory nerves (S) Strictly sensory for smell. Strictly sensory for smell. Nerve fibers are in cribriform plate of ethmoid bone Nerve fibers are in cribriform plate of ethmoid bone

65. I Olfactory nerve fibers

66. II. Optic nerves (S) Strictly sensory for vision Strictly sensory for vision Enters cranium via optic foramen anterior to pituitary gland in sella turcica. Enters cranium via optic foramen anterior to pituitary gland in sella turcica.

67. II Optic nerves

68. III. Occulomotor nerves (M) Primarily motor nerve to extrinsic eye muscles (inferior oblique, sup., inf. and medial rectus muscles) Primarily motor nerve to extrinsic eye muscles (inferior oblique, sup., inf. and medial rectus muscles)

69. III Occulomotor to eye muscles

70. IV. Trochlear nerves (M) Primarily motor to superior oblique eye muscles Primarily motor to superior oblique eye muscles

71. IV Trochlear nerve to sup. oblique

72. V. Trigeminal nerves (B) Mixed nerve with 3 divisions to face; largest cranial nerve. Mixed nerve with 3 divisions to face; largest cranial nerve.

73. V Trigeminal to face and jaw

74. VI. Abducens nerves (M) Primarily motor to lateral rectus muscle of eye Primarily motor to lateral rectus muscle of eye

75. VI Abducens to lateral rectus

76. VII. Facial nerves (B) Mixed nerve with 5 branches to neck and face. Mixed nerve with 5 branches to neck and face.

77. VII Facial nerve distribution – five branches to face & neck

78. VIII. Vestibulocochlear nerves (S) Purely sensory for hearing and equilibrium Purely sensory for hearing and equilibrium

79. VIII Vestibulocochlear to inner ear

80. IX. Glossopharyngeal nerves (B) Mixed nerve to pharynx, post. tongue, parotid glands Mixed nerve to pharynx, post. tongue, parotid glands

81. IX Glossopharyngeal to tongue and salivary glands

82. X. Vagus nerves (B) Mixed nerve extends to thoracic and abdominal cavities; parasympathetic to heart, lungs and abdomen Mixed nerve extends to thoracic and abdominal cavities; parasympathetic to heart, lungs and abdomen

84. XI. Accessory nerves (M) Motor nerves to larynx, pharynx and neck muscles for swallowing Motor nerves to larynx, pharynx and neck muscles for swallowing

85. XI Accessory to neck muscles

86. XII. Hypoglossal nerves (M) Motor to muscles of tongue Motor to muscles of tongue

87. XII Hypoglossal to tongue muscles