1. The Brain (& CNS)
Lecture 12a
BIOL241

2. Final Exam (Exam 4) Chapters 11 – 15* 100 points
Multiple choice, T/F, matching, fill in
Short answer, essays (2)*
Labeling (brain [including functions], cranial nerves, spinal cord)

3. Outline Overview of the human brain
Tour through the brain – structures and functions
Cerebral hemispheres and higher mental functions
Meninges
Ventricles and CSF
Brain disorders

4. The Human Brain Composed of wrinkled, pinkish gray tissue
Surface anatomy includes cerebral hemispheres, cerebellum, and brain stem
Ranges from 750 cc to 2100 cc
Contains almost 98% of the body’s neural tissue
Average weight, adult: 1300 – 1400 gm (~3 lb)
1010 to 1011 neurons
Trillions of connections
men = larger
Women = better connected

5. Major Regions and Landmarks
Figure 14–1

6. Embryology of the Brain
Table 14-1

7. Regions of the Adult Brain
Telencephalon (cerebrum) – cortex, white matter, and basal nuclei
Diencephalon – thalamus, hypothalamus, and epithalamus
Mesencephalon –midbrain (brain stem)
Metencephalon – pons (brain stem), cerebellum
Myelencephalon – medulla oblongata (brain stem)

8. Basic Pattern of the Central Nervous System
Spinal Cord
Central cavity surrounded by a gray matter core
External to which is white matter composed of myelinated fiber tracts
Brain
Similar to spinal cord but with additional areas of gray matter
Cerebellum has gray matter in nuclei
Cerebrum has nuclei and additional gray matter in the cortex
Figure 12.4

9. Some terms nucleus: collection of neuron cell bodies in the CNS
tract: collection of axons in the CNS
ganglia: collection of neuron cell bodies in the PNS
nerve: collection of axons in the PNS
Cranial nerves
Spinal nerves

10. Tour of the brain
From caudal/inferior to rostral/superior

11. The Brain Stem
Processes information between spinal cord and cerebrum or cerebellum
Controls automatic behaviors necessary for survival
Associated with 10 of the 12 pairs of cranial nerves (covered later)
Includes:
mesencephalon (midbrain)
pons
medulla oblongata
Note: some consider the diencephalon part of the brain stem as well

12. Brain Stem
Figure 12.15a

13. Anatomy: Brain stem
Most cranial nerves are located in the brain stem

14. Brain Stem
Figure 12.15b

15. Posterior view

16. Medulla Oblongata
Most inferior part of brain, connects brain to spinal cord
Relays information
Pyramids – two longitudinal ridges formed by corticospinal tracts
Regulates autonomic functions:
regulates arousal, heart rate, blood pressure, pace for respiration and digestion
Cranial nerves IX, X, XI, XII come off or enter

17. Medulla Oblongata
Figure 12.16c

18. Medulla Oblongata

19. Medulla Nuclei
Cardiovascular control center – adjusts force and rate of heart contraction
Respiratory centers – control rate and depth of breathing
Additional centers – regulate vomiting, hiccupping, swallowing, coughing, and sneezing

20. Pons

21. Pons Involved in somatic and visceral motor control
Contain the nuclei for cranial nerves V, VI, VII, VIII
Contains nuclei of the reticular formation
Control of respiration that modifies the info from the medulla
Nuclei and tracts passing through to the cerebellum (motor and somatosensory info)
Nuclei and tracts to other portions of the CNS (just passing through)

22. Cerebellum

23. Cerebellum “little brain” Second largest part of brain (~10% mass)
Provides precise timing and appropriate patterns of skeletal muscle contraction to coordinate repetitive body movements and help learning complex motor behaviors
Adjusts the postural muscles of the body, controls balance and equilibrium
Has 2 hemispheres, covered with cerebellar cortex
Recognizes and predicts sequences of events
Cerebellar activity occurs subconsciously (as does all processing that occurs outside the cerebral cortex)

24. Cerebellum – side view

25. Cerebellum
Cerebellum receives impulses of the intent to initiate voluntary muscle contraction
Monitors all proprioceptive info and visual info about body position
Cerebellar cortex calculates the best way to perform a movement
Programs and fine tunes movements by detecting mismatches in intended and actual movements
-- when learning to ride a bike, throw a curve ball or tie your shoe, cerebellum activity is high. When they become automatic, cerebellum is no longer involved

26. Mesencephalon

27. Mesencephalon Also called midbrain
Processes sight, sound, and associated reflexes
Maintains consciousness
Cranial nerve nuclei III and IV
2 basic divisions
tectum (roof)
tegmentum

28. Mesencephalon Process of visual and auditory sensations
corpora quadrigemina (in tectum) = superior colliculi (visual reflex) and inferior colliculi (auditory reflex)
Substantia nigra (in tegmentum)
Neurons inhibit activity of cerebral nuclei by releasing dopamine
If damaged, results in less dopamine released and muscle tone increases: muscle rigidity, difficulty initiating movement = Parkinson’s Disease
Reticular formation: maintain consciousness

29. Midbrain Nuclei
Figure 12.16a

30. Mesencephalon

31. Diencephalon
Figure 12.12

32. Diencephalon Located under cerebrum and cerebellum
Links cerebrum with brain stem
Integrates sensory information and motor commands
Cranial nerve II

33. Diencephalon Pineal Gland Secretes hormone melatonin Thalamus:
relays and processes sensory information
Hypothalamus:
hormone production
emotion
autonomic function

34. Diencephalon: Thalamus
Paired, egg-shaped masses connected at the midline by the intermediate mass
Nuclei project to and receive fibers from the cerebral cortex
Figure 14–9

35. Thalamus Sensory Relay station
All sensory that is projected to the cerebral cortex stops here first except smell
Filters ascending sensory information for primary sensory cortex
Relays information between basal nuclei and cerebral cortex
Mediates sensation, some motor activities, cortical arousal (thus learning, and memory)

36. Diencephalon: Hypothalamus
Lies below
thalamus
Figure 14–10a

37. Hypothalamus
Captain of the Autonomic nervous system, master overseer of homeostasis
Emotions and behavior: mediates perception of pleasure, fear, and rage
Regulation of body temperature, blood pressure, digestive tract motility, rate and depth of breathing, and many other visceral activities
Food intake (drives)
Water balance/thirst
Day/night rhythms
Endocrine functions- ADH and oxytocin

38. Structures of the Hypothalamus
Mamillary bodies:
Relay station for olfactory information
control reflex eating movements

39. Pituitary Gland Major endocrine gland, controls all others
Connected to hypothalamus via infundibulum (stalk)
Interfaces nervous and endocrine systems because it is controlled by the hypothalamus

40. Telencephalon
Basal nuclei
Cerebrum

41. The Basal Nuclei (Ganglia)
Figure 14–14b, c

42. Basal Nuclei Also called basal ganglia
Masses of gray matter found deep within the cortical white matter
The corpus striatum is composed of three parts
Caudate nucleus
Lentiform nucleus = putamen and the globus pallidus
Fibers of internal capsule running between and through caudate and lentiform nuclei
Direct subconscious activities

43. Functions of Basal Nuclei
Are involved with:
Subconscious control of skeletal muscle tone
Regulate attention and cognition
Regulate intensity of slow or stereotyped movements (walking, lifting)
Inhibit antagonistic and unnecessary movement
Subconscious habit learning
May store simple movement patterns

44. Basal Nuclei
Figure 12.11b

45. Cerebrum Largest part of brain (make up 83% of its mass)
Controls higher mental functions including all conscious thoughts and experience including all intellectual functions (more about this later)
Processes somatic sensory and motor information
Divided into left and right cerebral hemispheres
Surface layer of gray matter (cerebral cortex)

46. (Cerebral) Cortex Gray matter covering cerebral hemispheres
Accounts for 40% of the mass of the brain
Folded surface increases surface area
Elevated ridges = gyri (gyrus)
Shallow depressions = sulci (sulcus)
Deep grooves = fissures

47. Cerebral Gray and White Matter
Gray matter:
Cell bodies
Found in cerebral cortex and basal nuclei
White matter:
Fiber tracts (axons)
Deep to cerebral cortex
Surrounding basal nuclei

48. White Matter of the Cerebrum
Myelinated fibers (axons)
Association fibers:
arcuate: local
longitudinal: within one hemisphere
Commissural: between hemispheres
Projection: link cerebral cortex with rest of CNS
Figure 14–13

49. Examples Projection Fibers: Internal capsule
all ascending and descending projection fibers to and from cerebral cortex, passes though basal nuclei
Commissural fibers: corpus callosum
Connect the two cerebral hemispheres

50. Fiber Tracts in White Matter
Figure 12.10b

51. Limbic System
Figure 12.18

52. The Limbic System
One of two networks of neurons working together and spanning wide areas of the brain – the other is the consciousness regulating reticular formation (where?)
A of the medial functional grouping of the medial cerebral hemispheres and diencephalon that:
establishes emotional states and drives
links conscious functions of cerebral cortex with autonomic functions of brain stem
Allows us to react emotionally to conscious understanding and to be aware of emotions
facilitates memory storage and retrieval

53. The Limbic System
Figure 14–11a

54. Components of the Limbic System
Amygdala
deals with anger, danger, and fear responses, along with emotional smell memories
Limbic lobe of cerebral hemisphere:
Cingulate gyrus: plays a role in expressing emotions via gestures, and resolves mental conflict (emotion)
Hippocampus: convert new information into long-term memories (patient H.M.?)

55. Components of the Limbic System Continued
Fornix:
tract of white matter that connects hippocampus with hypothalamus
Diencepalic structures:
Portions of thalamus, hypothalamus

56. Reticular Formation
Sends impulses to the cerebral cortex to keep it conscious and alert
Figure 12.19

57. Higher Level Functions of Cerebral Hemispheres

58. The Cerebral Cortex 4 Lobes: Frontal Parietal Temporal Occipital
Figure 14–12b

59. Cerebral cortex
It enables sensation, communication, memory, understanding, and voluntary movements
Temporal lobe: memory, hearing
Frontal lobe: executive function, language
Parietal lobe: sense of self
Occipital lobe: vision

60. Cerebral Cortex landmarks
Lateral sulcus
Longitudinal fissure
Central sulcus
Precentral gyrus (primary motor)
Postcentral gyrus (primary sensory)
Association areas are for integrating information

61. Motor and Sensory Areas of the Cortex
Central sulcus separates motor and sensory areas
Figure 14–15a

62. Functional Areas of the Cerebral Cortex
The three types of functional areas are:
Motor areas – control voluntary movement
Sensory areas – conscious awareness of sensation
Association areas – integrate diverse information

63. Functional Areas of the Cerebral Cortex
Figure 12.8a

64. Functional Areas of the Cerebral Cortex
Figure 12.8b

65. Motor Areas Precentral gyrus of frontal lobe: Primary motor cortex:
directs voluntary movements
Primary motor cortex:
is the surface of precentral gyrus

66. Sensory Areas Postcentral gyrus of parietal lobe:
receives somatic sensory information (touch, pressure, pain, vibration, taste, and temperature)
Primary sensory cortex:
surface of postcentral gyrus

67. Association Areas
Any brain region that receives input from more than one sensory modality
aka “integrative areas” or higher level association areas
Relative abundance determines intellectual capacity
Include:
Prefrontal cortex
Language areas
General (common) interpretation area
Visceral association area

68. Functional Principles of the Cerebral hemispheres
Each cerebral hemisphere receives sensory information from, and sends motor commands to, the opposite side of body
The 2 hemispheres have somewhat different functions although their structures are alike
Correspondence between a specific function and a specific region of cerebral cortex is not precise
No functional area acts alone; conscious behavior involves the entire cortex

69. Higher level: Prefrontal Cortex
Most complicated region, coordinates info from all other association areas
Important in intellect, planning, reasoning, mood, abstract ideas, judgement, conscience, and accuratley predicting consequences
Phineas Gage?

70. Phineas Gage

71. Phineas Gage
In 1848 in Vermont, had a 3.5-foot-long, 13 lb. metal rod blown into his skull, through his brain, and out of the top of his head. Gage survived. In fact, he never even lost consciousness.
Friends reported a complete change in his personality after the incident. He lost all impulse control.

72. “Right Brain – Left Brain”

73. Hemispheric Lateralization
Functional differences between left and right hemispheres
In most people, left hemisphere (dominant hemisphere) controls:
reading, writing, and math, decision-making, logic, speech and language (usually)
Right cerebral hemisphere relates to:
recognition (faces, voice inflections), affect, visual/spatial reasoning, emotion, artistic skills

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

75. Types of Brain Waves
Figure 12.20b

76. Ventricles of the brain

77. Ventricles
Lined by ependymal cells which help to form the choroid plexus
There are two lateral ventricles in the cerebral hemispheres
Third ventricle is located in the diencephalon
Fourth ventricle is located between the pons and the cerebellum

78. Cranial meninges

79. Cranial meninges
Dura mater consists of an outer (endosteal layer) and an inner (meningeal layer)
In between the layers find the dural sinus
Arachnoid membrane covers the surface of the brain, have a subarachnoid space
Pia mater is anchored to the brain by astrocytes, wraps brain tightly like saran wrap

80. Inter-Layer Spaces – just like in the brain
Subdural space:
between arachnoid mater and dura mater
Subarachnoid space:
between arachnoid mater and pia mater
contains collagen/elastin fiber network that’s “spiderweb-like” (arachnoid trabeculae)
filled with cerebrospinal fluid (CSF)
Subdural, subarachanoid spaces are frequent sites of intracranial bleeding

81. Cerebrospinal Fluid (CSF)
Surrounds all exposed surfaces of CNS
Cushions, supports, and transports
Interchanges with interstitial fluid of brain
Like plasma or interstitial fluid elsewhere except much more pure
Arachnoid villi protrude superiorly into dural sinus and permit CSF to be absorbed into venous blood

82. Choroid Plexuses
Clusters of capillaries lined by ependymal cells that form tissue fluid filters, which hang from the roof of each ventricle
Have ion pumps that allow them to alter ion concentrations of the CSF
Help cleanse CSF by removing wastes

83. CSF flow: through ventricles, to arachnoid space, to dural sinuses (back to circulation)

84. Blood Supply to the Brain
Supplies nutrients and oxygen to brain
Delivered by internal carotid arteries and vertebral arteries
Removed from dural sinuses by internal jugular veins

85. Blood–Brain Barrier
Isolates CNS neural tissue from general circulation
Formed by network of tight junctions between endothelial cells of CNS capillaries and by feet of astrocyte processes
Astrocytes control blood–brain barrier by releasing chemicals that control permeability of endothelium

86. Blood–Brain Barrier
Lipid–soluble compounds (O2, CO2), steroids, and prostaglandins diffuse into interstitial fluid of brain and spinal cord
Other things have to be transported in

87. Cerebrovascular Disease
Disorders interfere with blood circulation to brain
Stroke or cerebrovascular accident (CVA):
shuts off blood to portion of brain
neurons die
Tissue plasminogen activator (TPA) is the only approved treatment for stroke (except aspirin)
Transient Ischemic Attach (TIA)

88. Degenerative Brain Disorders
Alzheimer’s disease – a progressive degenerative disease of the brain that results in dementia (usually frontotemporal)
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