1. Chapter 12 The Central Nervous System Part C Shilla Chakrabarty, Ph.D.

2. Electroencephalogram (EEG)
Records electrical activity that accompanies brain function
Measures electrical potential differences between various cortical areas
(a) Scalp electrodes are used to record brain wave activity (EEG).

3. Brain Waves Patterns of neuronal electrical activity
Generated by synaptic activity in the cortex
Each person’s brain waves are unique
Can be grouped into four classes based on frequency measured as Hertz (Hz)
Alpha waves (8–13 Hz)—regular and rhythmic, low-amplitude, synchronous waves indicating an “idling” brain
Beta waves (14–30 Hz)—rhythmic, less regular waves occurring when mentally alert
Theta waves (4–7 Hz)—more irregular; common in children and uncommon in adults
Delta waves (4 Hz or less)—high-amplitude waves seen in deep sleep and when reticular activating system is damped, or during anesthesia; may indicate brain damage

4. Brain Waves Indicate State Of The Brain
Alpha waves—awake but relaxed
Beta waves—awake, alert
Theta waves—common in children
Delta waves—deep sleep
(b) Brain waves shown in EEGs fall into four general classes.
1-second interval
Brain waves change with age, sensory stimuli, brain disease, and chemical state of the body
EEGs are 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

5. Epilepsy Control of Epilepsy Epilepsy occurs in 1% of the population
A victim of epilepsy may lose consciousness, fall stiffly, and have uncontrollable jerking
Epilepsy is not associated with intellectual impairments
Epileptic seizures are categorized as:
Absence seizures, or petit mal
Mild seizures seen in young children where the expression goes blank
Tonic-clonic (grand mal) seizures
Victim loses consciousness, bones are often broken due to intense contractions, may experience loss of bowel and bladder control, and severe biting of the tongue
Control of Epilepsy
Anticonvulsive drugs
Vagus nerve stimulators implanted under the skin of the chest can keep electrical activity of the brain from becoming chaotic

6. Consciousness Conscious perception of sensation
Voluntary initiation and control of movement
Capabilities associated with higher mental processing (memory, logic, judgment, etc.)
Clinically defined on a continuum that grades behavior in response to stimuli
Alertness
Drowsiness (lethargy)
Stupor
Coma
Loss of consciousness (e.g., fainting or syncopy) is a signal that brain function is impaired

7. Sleep
State of partial unconsciousness from which a person can be aroused by stimulation
Two major types of sleep (defined by EEG patterns)
Nonrapid eye movement (NREM)
Rapid eye movement (REM)
First two stages of NREM occur during the first 30–45 minutes of sleep
Fourth stage is achieved in about 90 minutes, and then REM sleep begins abruptly

8. Awake
REM: Skeletal
muscles (except
ocular muscles
and diaphragm)
are actively
inhibited; most
dreaming occurs.
NREM stage 1:
Relaxation begins;
EEG shows alpha
waves, arousal is easy.
NREM stage 2: Irregular
EEG with sleep spindles
(short high- amplitude
bursts); arousal is more
difficult.
NREM stage 3: Sleep
deepens; theta and
delta waves appear;
vital signs decline.
NREM stage 4: EEG is
dominated by delta
waves; arousal is difficult;
bed-wetting, night terrors,
and sleepwalking may
occur.
(a) Typical EEG patterns
Figure 12.21a

9. Sleep Patterns
Alternating cycles of sleep and wakefulness reflect a natural circadian (24-hour) rhythm
RAS activity is inhibited during, but RAS also mediates, dreaming sleep
The suprachiasmatic and preoptic nuclei of the hypothalamus time the sleep cycle
A typical sleep pattern alternates between REM and NREM sleep
(b) Typical progression of an adult through one night’s sleep stages
Awake
REM
Stage 1
Stage 2
Non
Stage 3
Stage 4
Time (hrs)

10. Importance of Sleep
Slow-wave sleep (NREM stages 3 and 4) is presumed to be the restorative stage
People deprived of REM sleep become moody and depressed
REM sleep may be a reverse learning process where superfluous information is purged from the brain
Daily sleep requirements decline with age
Stage 4 sleep declines steadily and may disappear after age 60
Sleep Disorders
Narcolepsy : Lapsing abruptly into sleep from the awake state
Insomnia: Chronic inability to obtain the amount or quality of sleep needed
Sleep apnea: Temporary cessation of breathing during sleep

11. Language Language implementation system Basal nuclei
Broca’s area and Wernicke’s area (in the association cortex on the left side)
Analyzes incoming word sounds
Produces outgoing word sounds and grammatical structures
Corresponding areas on the right side are involved with nonverbal language components

12. Memory Storage and retrieval of information Two stages of storage
Short-term memory (STM, or working memory)—temporary holding of information; limited to seven or eight pieces of information
Long-term memory (LTM) has limitless capacity
Factors that affect transfer from STM to LTM
Emotional state—best if alert, motivated, surprised, and aroused
Rehearsal—repetition and practice
Association—tying new information with old memories
Automatic memory—subconscious information stored in LTM

13. Memory: STM and LTM Outside stimuli
General and special sensory receptors
Data transfer
influenced by:
Excitement
Rehearsal
Association of
old and new data
Long-term
memory
(LTM)
Data permanently
lost
Afferent inputs
Retrieval
Forget
Data selected
for transfer
Automatic
Data unretrievable
Temporary storage
(buffer) in
cerebral cortex
Short-term
memory (STM)

14. Categories of Memory Declarative memory (factual knowledge)
Explicit information
Related to our conscious thoughts and our language ability
Stored in LTM with context in which it was learned
Nondeclarative memory
Less conscious or unconscious
Acquired through experience and repetition
Best remembered by doing; hard to unlearn
Includes procedural (skills) memory, motor memory, and emotional memory

15. Brain Structures Involved in Declarative Memory
Hippocampus and surrounding temporal lobes function in consolidation and access to memory
ACh from basal forebrain is necessary for memory formation and retrieval
Smell
Basal forebrain
Prefrontal cortex
Taste
Thalamus
Touch
Hearing
Vision
Hippocampus
Prefrontal
cortex
Basal
forebrain
Association
Sensory
input
ACh
Medial temporal lobe
(hippocampus, etc.)
(a) Declarative memory circuits

16. Brain Structures Involved in Nondeclarative Memory
Procedural memory
Basal nuclei relay sensory and motor inputs to the thalamus and premotor cortex
Dopamine from substantia nigra is necessary
Motor memory—cerebellum
Emotional memory—amygdala

17. (b) Procedural (skills) memory circuits
Sensory and
motor inputs
Association
cortex
Basal
nuclei
Premotor
cortex
Thalamus
Dopamine
Premotor
cortex
Substantia
nigra
Basal nuclei
Thalamus
Substantia nigra
(b) Procedural (skills) memory circuits
Figure 12.23b

18. Protection of the Brain
Bone (skull)
Membranes (meninges)
Watery cushion (cerebrospinal fluid)
Blood-brain barrier

19. Skin of scalp Periosteum Bone of skull Dura Periosteal mater Meningeal
Superior
sagittal sinus
Arachnoid mater
Pia mater
Subdural
space
Arachnoid villus
Blood vessel
Subarachnoid
space
Falx cerebri
(in longitudinal
fissure only)
Figure 12.24

20. Dura Mater
Strongest meninx
Two layers of fibrous connective tissue (around the brain) separate to form dural sinuses

21. Dural septa limit excessive movement of the brain
Dura Mater
Dural septa limit excessive movement of the brain
Falx cerebri—in the longitudinal fissure; attached to crista galli
Falx cerebelli—along the vermis of the cerebellum
Tentorium cerebelli—horizontal dural fold over cerebellum and in the transverse fissure

22. Superior sagittal sinus Falx cerebri Straight sinus Crista galli
of the
ethmoid
bone
Tentorium
cerebelli
Falx
cerebelli
Pituitary
gland
(a) Dural septa
Figure 12.25a

23. Arachnoid Mater Pia Mater Middle layer with weblike extensions
Separated from the dura mater by the subdural space
Subarachnoid space contains CSF and blood vessels
Arachnoid villi protrude into the superior sagittal sinus and permit CSF reabsorption
Pia Mater
Layer of delicate vascularized connective tissue that clings tightly to the brain

24. Skin of scalp Periosteum Bone of skull Dura Periosteal mater Meningeal
Superior
sagittal sinus
Arachnoid mater
Pia mater
Subdural
space
Arachnoid villus
Blood vessel
Subarachnoid
space
Falx cerebri
(in longitudinal
fissure only)
Figure 12.24

25. Cerebrospinal Fluid (CSF)
Composition
Watery solution
Less protein and different ion concentrations than plasma
Constant volume
Functions
Gives buoyancy to the CNS organs
Protects the CNS from blows and other trauma
Nourishes the brain and carries chemical signals

26. Right lateral ventricle (deep to cut)
Superior
sagittal sinus 4
Choroid
plexus
Arachnoid villus
Interventricular
foramen
Subarachnoid space
Arachnoid mater
Meningeal dura mater
Periosteal dura mater 1
Right lateral ventricle
(deep to cut)
Choroid plexus
of fourth ventricle 3
Third ventricle
CSF is produced by the
choroid plexus of each
ventricle. 1
Cerebral aqueduct
Lateral aperture
Fourth ventricle
CSF flows through the
ventricles and into the
subarachnoid space via the
median and lateral apertures.
Some CSF flows through the
central canal of the spinal cord. 2
Median aperture 2
Central canal
of spinal cord
CSF flows through the
subarachnoid space. 3
(a) CSF circulation
CSF is absorbed into the dural venous
sinuses via the arachnoid villi. 4
Figure 12.26a

27. Choroid Plexuses Produce CSF at a constant rate
Hang from the roof of each ventricle
Clusters of capillaries enclosed by pia mater and a layer of ependymal cells
Ependymal cells use ion pumps to control the composition of the CSF and help cleanse CSF by removing wastes
Figure 12.26b
Ependymal
cells
Capillary
Connective
tissue of
pia mater
Wastes and
unnecessary
solutes absorbed
Section
of choroid
plexus
(b) CSF formation by choroid plexuses
Cavity of
ventricle
CSF forms as a filtrate
containing glucose, oxygen,
vitamins, and ions
(Na+, Cl–, Mg2+, etc.)

28. Blood-Brain Barrier Helps maintain a stable environment for the brain
Separates neurons from some blood-borne substances
Composition
Continuous endothelium of capillary walls
Basal lamina
Feet of astrocytes
Provide signal to endothelium for the formation of tight junctions
Selective barrier
Allows nutrients to move by facilitated diffusion
Allows any fat-soluble substances to pass, including alcohol, nicotine, and anesthetics
Absent in some areas, e.g., vomiting center and the hypothalamus, where it is necessary to monitor the chemical composition of the blood

29. (a) Astrocytes are the most abundant CNS neuroglia.
Capillary
Neuron
Astrocyte
(a) Astrocytes are the most abundant CNS neuroglia.
Figure 11.3a

30. Homeostatic Imbalances of the Brain
Traumatic brain injuries
Concussion—temporary alteration in function
Contusion—permanent damage
Subdural or subarachnoid hemorrhage—may force brain stem through the foramen magnum, resulting in death
Cerebral edema—swelling of the brain associated with traumatic head injury

31. Homeostatic Imbalances of the Brain
Cerebrovascular accidents (CVAs)(strokes)
Blood circulation is blocked and brain tissue dies, e.g., blockage of a cerebral artery by a blood clot
Typically leads to hemiplegia, or sensory and speed deficits
Transient ischemic attacks (TIAs)—temporary episodes of reversible cerebral ischemia
Tissue plasminogen activator (TPA) is the only approved treatment for stroke

32. Homeostatic Imbalances of the Brain
Degenerative brain disorders
Alzheimer’s disease (AD): 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 and cerebral cortex