Lecture 12a

1
Lecture 12a

• The Brain

2
Final Exam (Exam 6)

• Chapters 12 - 14
• 75 points
• Multiple choice, T/F, matching, fill in
• Short answer, essays (2)
• Labeling (brain including functions, cranial
  nerves, spinal cord)

3
Overview

• Overview of the human brain
• Tour through the brain structures and functions
• Cerebral hemispheres and higher mental functions
• Meninges
• Venticles 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 bodys neural tissue
• Average weight 3 lb
• 1010 to 1011 neurons
• Trillions of connections
• men larger
• Women better connected

5
Major Regions and Landmarks
Figure 141
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 through 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
AnatomyBrain 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 go into
  

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,
  hiccuping, 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 Parkinsons
  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 149
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 1410a
37
Hypothalamus

• Captain of the Autonomic nervous system, master
  overseer of homeoastatsis
• 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 1414b, 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 1413
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 1411a
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 ofCerebral Hemispheres
58
The Cerebral Cortex
4 Lobes Frontal Parietal Temporal occipital
Figure 1412b
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 1415a
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
• 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
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

73
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

74
Types of Brain Waves
Figure 12.20b
75
Ventricles of the brain
76
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

77
Cranial meninges
78
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

79
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 thats
  spiderweb-like (arachnoid trabeculae)
• filled with cerebrospinal fluid (CSF)
• ?Subdural, subarachanoid spaces are frequent
  sites of intracranial bleeding

80
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

81
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

82
CSF flow through ventricles, to arachnoid space,
to dural sinuses (back to circulation)
83
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

84
BloodBrain 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 bloodbrain barrier by
  releasing chemicals that control permeability of
  endothelium

85
BloodBrain Barrier

• Lipidsoluble compounds (O2, CO2), steroids, and
  prostaglandins diffuse into interstitial fluid of
  brain and spinal cord
• Other things have to be transported in

86
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)

87
Degenerative Brain Disorders

• Alzheimers disease a progressive degenerative
  disease of the brain that results in dementia
  (usually frontotemporal)
• Parkinsons disease degeneration of the
  dopamine-releasing neurons of the substantia
  nigra
• Huntingtons disease a fatal hereditary
  disorder caused by accumulation of the protein
  huntingtin that leads to degeneration of the
  basal nuclei