1. The Brain and Cranial Nerves
Chapter 14
The Brain and Cranial Nerves

2. The Brain The Brain is part of Central Nervous System (CNS)
It is divided into 6 major parts:
The cerebrum
The diencephalon
The mesencephalon
The cerebellum
The pons
The medulla oblongata

3. Major divisions of the Brain

4. The real thing
Fig.14.01b

5. The Human Brain Ranges from 750 cc to 2100 cc
Contains almost 98% of the body’s neural tissue
Average weight about 1.4 kg (3 lb)

6. Protection of the Brain
The brain is protected by bone, meninges, and cerebrospinal fluid
Harmful substances are shielded from the brain by the blood-brain barrier

7. Cerebrospinal fluid
Protects by absorbing shock (it “floats” the brain.
Maintains the electrochemical environment (opitmal pH & osmolality).
Circulates nutrients and wastes.

8. The Ventricles

9. Formation of CSF

10. Choroid Plexuses
Figure 12.25a

11. Fig c
Cirulaation of CSF

12. Meninges
Three connective tissue membranes lie external to the CNS – dura mater, arachnoid mater, and pia mater
Functions of the meninges
Cover and protect the CNS
Protect blood vessels and enclose venous sinuses
Contain cerebrospinal fluid (CSF)
Form partitions within the skull

13. The Meninges of the Brain

14. Dura Mater
Three dural septa extend inward and limit excessive movement of the brain
Falx cerebri – fold that dips into the longitudinal fissure
Falx cerebelli – runs along the vermis of the cerebellum
Tentorium cerebelli – horizontal dural fold extends into the transverse fissure

15. Dural Folds Falx cerebri, tentorium cerebelli, and falx cerebelli
Figure 14–3b

16. Arachnoid Mater The middle meninx, which forms a loose brain covering
It is separated from the dura mater by the subdural space
Beneath the arachnoid is a wide subarachnoid space filled with CSF and large blood vessels
Arachnoid villi protrude superiorly and permit CSF to be absorbed into venous blood

17. Blood flow, O2 and the BBB
Though only 2% of body mass the brain consumes 20% of the oxygen and glucoseof the resting body.
No O2 for a minute = dizziness
4 minutes = brain damage
6 minutes = death
The brain is protected by the blood-brain barrier.

18. Blood-Brain Barrier: Functions
Selective barrier that allows nutrients to pass freely
Is ineffective against substances that can diffuse through plasma membranes
Absent in some areas (vomiting center and the hypothalamus), allowing these areas to monitor the chemical composition of the blood
Stress increases the ability of chemicals to pass through the blood-brain barrier

19. The Blood-brain barrier

20. The Brain Stem The brain stem is comprised of 3 main subdivisions:
The Medulla Oblongata
The Pons
The Mesencephalon

21. The diencephalon & brainstem

22. Medulla Oblongata: 3 Groups of Nuclei
Autonomic nuclei:
control visceral activities
Sensory and motor nuclei:
of cranial nerves
Relay stations:
along sensory and motor pathways

23. Nuclei of the medulla oblongata

24. Summary: The Medulla Oblongata
Table 14-2

25. Links cerebellum with mesencephalon, diencephalon, cerebrum, and spinal cord
The Pons
Figure 14–6c

26. The Pons: 4 Groups
Sensory and motor nuclei of cranial nerves V, VI, VII, VIII
Nuclei involved with respiration:
apneustic center and pneumotaxic center
modify respiratory rhythmicity center activity

27. The Pons: 4 Groups Nuclei and tracts:
process and relay information to and from cerebellum
Ascending, descending, and transverse tracts:
transverse fibers (axons)
link nuclei of pons with opposite cerebellar hemisphere

28. The Cerebellum
An autonomic & motor processing center
Figure 14–7a

29. Functions of the Cerebellum
Adjusts postural muscles
Fine-tunes conscious and subconscious movements

30. Structures of the Cerebellum
Figure 14–7b

31. Structures of the Cerebellum (1 of 2)
Folia:
surface of cerebellum
highly folded neural cortex
Anterior and posterior lobes:
separated by primary fissure

32. Structures of the Cerebellum (2 of 2)
Cerebellar hemispheres:
separated at midline by vermis
Vermis:
narrow band of cortex
Flocculonodular lobe:
below fourth ventricle

33. Summary: The Cerebellum
Table 14-3

34. The Mesencephalon
Figure 14–8a

35. Midbrain nuclei
Substantia nigra: dopamine release, control of subconscious muscle movents.
Red nuclei: synapses between neurons of cerebellum and cerebrum. Also origin of oculomotor nerve (CN III) and trochlear nerve (CN IV).

36. Some major functions mesencephalon
Cerebral peduncles: contain motor axons connecting cerebrum to brain stem and sensory axons that connect medulla to thalamus
Tectum:
Superior colliculi: visual reflexes, including pupillary reflexes.
Inferior colliculi: auditory path from ear to thalamus.
Startle reflex

37. Summary: The Mesencephalon
Table 14-4

38. The Diencephalon
The Thalamus - switch board for the cerebrum. Includes the:
Geniculate nuclei (part of the ventral group):
Medial processes auditory information.
Lateral processes visual input.
Other ventral nuclei connect motor & sensory areas of cortex to cerebellum & spinal cord
Anterior & medial nuclei
Anterior connects to limbic system & hypothalamus
Medial connects with cortex & limbic system

39. The Diencephalon

40. The Thalamus: Filters ascending sensory information for primary sensory cortex. Relays information between basal nuclei and cerebral cortex
Figure 14–9

41. Those pesky thalamic nuclei
Fig a-d

42. Oblique section of brain showing the Thalamus and basal nuclei
Fig e
Oblique section of brain showing the Thalamus and basal nuclei

43. Summary: Thalamic Nuclei
Table 14-5

44. The Hypothalamus Functions of the hypothalamus ANS control
, heart rate, respiration, sweating, digestion, urination, stress response
Hormones - ADH, oxytocin, GnRH et al.
Basic emotions - rage, sex drive, fear, pain pleasure.
Thirst & appetite
Temperature & sleep/wake (circadian) cycles

45. The Hypothalamus
Lies below thalamus
Figure 14–10a

46. Summary: The Hypothalamus
Table 14-6

47. The Limbic System Is a functional grouping that:
establishes emotional states
links conscious functions of cerebral cortex with autonomic functions of brain stem
facilitates memory storage and retrieval

48. The Limbic System
Figure 14–11a

49. The Limbic System
Figure 14–11b

50. Limbic System
Structures located on the medial aspects of cerebral hemispheres and diencephalon
Includes the rhinencephalon, amygdala, hypothalamus, and anterior nucleus of the thalamus
Parts especially important in emotions:
Amygdala – deals with anger, danger, and fear responses
Cingulate gyrus – plays a role in expressing emotions via gestures, and resolves mental conflict
Puts emotional responses to odors – e.g., skunks smell bad

51. Limbic System: Emotion and Cognition
The limbic system interacts with the prefrontal lobes, therefore:
One can react emotionally to conscious understandings
One is consciously aware of emotion in one’s life
Hippocampal structures – convert new information into long-term memories

52. Summary: The Limbic System
Table 14-7

53. The Cerebrum Major divisions of the Cerebrum
Hemispheres - left and right split down the middle by the longitudinal fissure.
Lobes:
Frontal, parietal, occipital, temporal and insula
Delineated by the sulci (singular sulcus):
Central
Parieto-occipital
Lateral

54. Lobes of the Cerebrum

55. Landmarks of the cerebrum

56. White Matter of the Cerebrum
Myelinated fibers (axons)
Association fibers
Commissural fibers
Projection fibers
Figure 14–13

57. Cerebral White Matter

58. The Basal Nuclei
Figure 14–14b, c

59. Functions of Basal Nuclei
Are involved with:
the subconscious control of skeletal muscle tone
the coordination of learned movement patterns (walking, lifting)

60. Functional map of the cerebrum
Fig

61. Motor and Sensory Areas of the Cortex
Figure 14–15a

62. Interpretive Areas of Cortex
Figure 14–15b

63. Hemispheric Lateralization
Figure 14–16

64. The Left Hemisphere
In most people, left brain (dominant hemisphere) controls:
reading, writing, and math
decision-making
speech and language

65. The Right Hemisphere Right cerebral hemisphere relates to:
senses (touch, smell, sight, taste, feel)
recognition (faces, voice inflections)

66. The Electroencephalogram
Figure 14–17

67. Types of Brain Waves
Alpha waves – Hz, regular and rhythmic, low-amplitude, slow, synchronous waves indicating an “idling” brain
Beta waves – Hz, rhythmic, more irregular waves occurring during the awake and mentally alert state
Theta waves – Hz, more irregular than alpha waves; common in children but abnormal in adults
Delta waves – Hz, high-amplitude waves seen in deep sleep and when reticular activating system is damped

68. Brain Waves: State of the Brain
Brain waves change with age, sensory stimuli, brain disease, and the chemical state of the body
EEGs can be used to diagnose and localize brain lesions, tumors, infarcts, infections, abscesses, and epileptic lesions
A flat EEG (no electrical activity) is clinical evidence of death

69. Cranial Nerves
Figure 14–18

70. The 12 cranial nerves On Old Olympus’ Towering Top A Frenchman Viewed
Greek
Villagers At
Home
The 12 cranial nerves

71. The Olfactory Nerve (I)
Figure 14–19

72. The Optic Nerves (II)
Figure 14–20

73. The Oculomotor Nerves (III)
Figure 14–21

74. The Trochlear Nerves (IV)
Figure 14–21

75. The Abducens Nerves (VI)
Figure 14–21

76. The Trigeminal Nerves (V)
Figure 14–22

77. The Facial Nerves (VII)
Figure 14–23

78. The Vestibulocochlear Nerves (VIII)
Figure 14–24

79. The Glossopharyngeal Nerves (IX)
Figure 14–25

80. The Vagus Nerves (X)
Figure 14–26

81. The Accessory Nerves (XI)
Figure 14–27

82. The Hypoglossal Nerves (XII)
Figure 14–27

83. Summary: Cranial Nerves
Table 14-9 (1 of 2)

84. Summary: Cranial Nerves
Table 14-9 (2 of 2)

85. Examples of Cranial Reflexes
Table 14-10

86. Clinical Stuff Epilepsy CVA & TIA Degenerative Diseases Alzheimers
Huntington’s
Parkinbson’s

87. Epilepsy
A victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking, characteristic of epileptic seizure
Epilepsy is not associated with, nor does it cause, intellectual impairments
Epilepsy occurs in 1% of the population

88. Epileptic Seizures
Absence seizures, or petit mal – mild seizures seen in young children where the expression goes blank
Grand mal seizures – victim loses consciousness, bones are often broken due to intense convulsions, loss of bowel and bladder control, and severe biting of the tongue

89. Control of Epilepsy
Epilepsy can usually be controlled with anticonvulsive drugs
Valproic acid, a nonsedating drug, enhances GABA and is a drug of choice
Vagus nerve stimulators can be implanted under the skin of the chest and can keep electrical activity of the brain from becoming chaotic

90. Cerebrovascular Accidents (Strokes)
Caused when blood circulation to the brain is blocked and brain tissue dies
Most commonly caused by blockage of a cerebral artery
Other causes include compression of the brain by hemorrhage or edema, and atherosclerosis
Transient ischemic attacks (TIAs) – temporary episodes of reversible cerebral ischemia
Tissue plasminogen activator (TPA) is the only approved treatment for stroke

91. Degenerative Brain Disorders
Alzheimer’s disease – a progressive degenerative disease of the brain that results in dementia
Parkinson’s disease – degeneration of the dopamine-releasing neurons of the substantia nigra
Huntington’s disease – a fatal hereditary disorder caused by accumulation of the protein huntingtin that leads to degeneration of the basal nuclei