The%20Cerebellum

1
The Cerebellum

• 11 of brain mass
• Dorsal to the pons and medulla
• precise timing and appropriate patterns of
  skeletal muscle contraction
• Sports

2
Cognitive Function of the Cerebellum

• sequences of events during complex movements
• nonmotor functions such as word association and
  puzzle solving

3
Anterior lobe
Cerebellar cortex
Arbor vitae
Cerebellar peduncles
Posterior lobe
Superior
Middle
Choroid plexus of fourth ventricle
Inferior
Medulla oblongata
Flocculonodular lobe
(b)
Figure 12.17b
4
Limbic System

• Emotional or affective brain
• Amygdalarecognizes angry or fearful facial
  expressions, assesses danger, and elicits the
  fear response
• Cingulate gyrusplays a role in expressing
  emotions via gestures, and resolves mental
  conflict
• emotional responses to odors

5
Limbic System Emotion and Cognition

• The limbic system interacts with the prefrontal
  lobes, therefore
• We can react emotionally to things we consciously
  understand to be happening
• We are consciously aware of emotional richness in
  our lives

6
Reticular Formation

• Three broad columns along the length of the brain
  stem
• Raphe nuclei
• Medial (large cell) group of nuclei
• Lateral (small cell) group of nuclei
• Has far-flung axonal connections with
  hypothalamus, thalamus, cerebral cortex,
  cerebellum, and spinal cord

7
Reticular Formation RAS and Motor Function

• RAS (reticular activating system)
• Sends impulses to the cerebral cortex to keep it
  conscious and alert
• Filters out repetitive and weak stimuli (99 of
  all stimuli!)
• Severe injury results in permanent
  unconsciousness (coma)

8
Reticular Formation RAS and Motor Function

• Motor function
• Helps control coarse limb movements
• Reticular autonomic centers regulate visceral
  motor functions
• Vasomotor
• Cardiac
• Respiratory centers

9
Radiations to cerebral cortex
Visual impulses
Auditory impulses
Reticular formation
Descending motor projections to spinal cord
Ascending general sensory tracts (touch, pain,
temperature)
Figure 12.19
10
(a) Scalp electrodes are used to record brain
waveactivity (EEG).
Figure 12.20a
11
Brain Waves State of the Brain

• EEGs 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

12
Brain Waves

• Patterns of neuronal electrical activity
• Each persons brain waves are unique
• Can be grouped into four classes based on
  frequency measured as Hertz (Hz)

13
Types of Brain Waves

• Alpha waves (813 Hz)idling brain
• Beta waves (1430 Hz)mentally alert
• Theta waves (47 Hz)irregular common in
  children and uncommon in adults
• Delta waves (4 Hz or less)deep sleep and when
  during anesthesia may indicate brain damage

14
1-second interval
Alpha wavesawake but relaxed
Beta wavesawake, alert
Theta wavescommon in children
Delta wavesdeep sleep
(b) Brain waves shown in EEGs fall intofour
general classes.
Figure 12.20b
15
Epilepsy

• A victim of epilepsy may lose consciousness, fall
  stiffly, and have uncontrollable jerking
• not associated with intellectual impairments
• Epilepsy occurs in 1 of the population
• 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

16
Control of Epilepsy

• Anticonvulsive drugs
• Vagus nerve stimulators implanted under the skin
  of the chest

17
Consciousness

• Conscious perception of sensation
• Voluntary initiation and control of movement
• Capabilities associated with higher mental
  processing (memory, logic, judgment, etc.)

18
Consciousness

• Clinically defined on a continuum that grades
  behavior in response to stimuli
• Alertness
• Drowsiness (lethargy)
• Stupor
• Coma

19
Sleep

• State of partial unconsciousness from which a
  person can be aroused by stimulation
• Two major types of sleep
• Nonrapid eye movement (NREM)
• Rapid eye movement (REM)

20
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
21
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
• Daily sleep requirements decline with age
• Stage 4 sleep declines steadily and may disappear
  after age 60

22
Sleep Disorders

• Narcolepsy
• Insomnia
• Sleep apnea

23
Memory

• Storage and retrieval of information
• Two stages of storage
• Short-term memory
• Long-term memory (LTM)
• has limitless capacity

24
Transfer from STM to LTM

• Factors that affect transfer from STM to LTM
• Emotional statebest if alert, motivated,
  surprised, and aroused
• Rehearsal
• Association
• Automatic memory

25
Protection of the Brain

• Bone (skull)
• Membranes (meninges)
• Watery cushion (cerebrospinal fluid)
• Blood-brain barrier

26
Skin of scalp
Periosteum
Bone of skull
Dura mater
Periosteal
Meningeal
Superior sagittal sinus
Arachnoid mater
Pia mater
Arachnoid villus
Subdural space
Blood vessel
Falx cerebri (in longitudinal fissure only)
Subarachnoid space
Figure 12.24
27
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
1
CSF is produced by the choroid plexus of
each ventricle.
Cerebral aqueduct
Lateral aperture
2
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.
Fourth ventricle
Median aperture
2
Central canal of spinal cord
CSF flows through the subarachnoid space.
3
(a) CSF circulation
4
CSF is absorbed into the dural
venous sinuses via the arachnoid villi.
Figure 12.26a
28
Blood-Brain Barrier

• Helps maintain a stable environment for the brain
  
• Separates neurons from some bloodborne substances

29
Capillary
Neuron
Astrocyte
(a) Astrocytes are the most abundantCNS
neuroglia.
Figure 11.3a
30
Blood-Brain Barrier Functions

• 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
• where it is necessary to monitor the chemical
  composition of the blood

31
Homeostatic Imbalances of the Brain

• Degenerative brain disorders
• Alzheimers disease (AD) a progressive
  degenerative disease of the brain that results in
  dementia
• 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
  and cerebral cortex

32
Spinal Cord

• Location
• Begins at the foramen magnum
• Ends as conus medullaris at L1 vertebra
• Functions
• Provides two-way communication to and from the
  brain
• Contains spinal reflex centers

33
T12
Ligamentum flavum
L5
Lumbar puncture needle entering subarachnoid space
L4
Supra- spinous ligament
Filum terminale
L5
S1
Inter- vertebral disc
Cauda equina in subarachnoid space
Dura mater
Arachnoid matter
Figure 12.30
34
Cervical spinal nerves
Cervical enlargement
Dura and arachnoid mater
Thoracic spinal nerves
Lumbar enlargement
Conus medullaris
Lumbar spinal nerves
Cauda equina
Filum terminale
Sacral spinal nerves
(a) The spinal cord and its nerve roots,
with the bony vertebral arches removed. The
dura mater and arachnoid mater are cut
open and reflected laterally.
Figure 12.29a
35
Spinal Cord

• Spinal nerves
• 31 pairs
• Cervical and lumbar enlargements
• The nerves serving the upper and lower limbs
  emerge here
• Cauda equina
• The collection of nerve roots at the inferior end
  of the vertebral canal

36
Dorsal median sulcus
Gray commissure
Dorsal funiculus
Dorsal horn
Gray matter
White columns
Ventral funiculus
Ventral horn
Lateral funiculus
Lateral horn
Dorsal root ganglion
Spinal nerve
Central canal
Dorsal root (fans out into dorsal rootlets)
Ventral median fissure
Ventral root (derived from several ventral
rootlets)
Pia mater
Arachnoid mater
Spinal dura mater
(b) The spinal cord and its meningeal coverings
Figure 12.31b
37
Dorsal root (sensory)
Dorsal root ganglion
Dorsal horn (interneurons)
Somatic sensory neuron
Visceral sensory neuron
Visceral motor neuron
Spinal nerve
Ventral horn (motor neurons)
Ventral root (motor)
Somatic motor neuron
Interneurons receiving input from somatic sensory
neurons
Interneurons receiving input from visceral
sensory neurons
Visceral motor (autonomic) neurons
Somatic motor neurons
Figure 12.32
38
Ascending tracts
Descending tracts
Ventral white commissure
Fasciculus gracilis
Dorsal white column
Fasciculus cuneatus
Lateral reticulospinal tract
Dorsal spinocerebellar tract
Lateral corticospinal tract
Rubrospinal tract
Ventral spinocerebellar tract
Medial reticulospinal tract
Lateral spinothalamic tract
Ventral corticospinal tract
Ventral spinothalamic tract
Vestibulospinal tract
Tectospinal tract
Figure 12.33