Title: The Brain and Cranial Nerves
1The Brain and Cranial Nerves
Slides accompany Chapter 14 and 15 of your
text, Fundamentals of Anatomy Physiology by
Frederic H. Martini
2Midbrain (mesencephalon)
- One inch in length
- Extends from pons to diencephalon
- Cerebral aqueduct connects 3rd ventricle above to
4th ventricle below
3Structures of the Mesencephalon
- Tectum
- 2 pairs of sensory nuclei (corpora quadrigemina)
- superior colliculus (visual)
- inferior colliculus (auditory)
4Relationship of mesencephalon to pons and
cerebellum
5Structures of the Mesencephalon
- Tegmentum
- red nucleus (many blood vessels)
- substantia nigra (pigmented gray matter)
6Structures of the Mesencephalon
- Cerebral peduncles
- nerve fiber bundles on ventrolateral surfaces
- contain
- descending fibers to cerebellum
- motor command (pyramidal) fibers
7Mesencephalon in Section
- Red nucleus-- rich blood supply iron-containing
pigment - Substantia nigra---helps controls subconscious
muscle activity - cortex cerebellum coordinate muscular movements
by sending information here from the cortex and
cerebellum - Cerebral peduncles---clusters of motor sensory
fibers
8The Mesencephalon
Figure 148a
9Midbrain(mesencephalon of the brainstem)
10Summary The Mesencephalon
Table 14-4
11Reticular Formation (Dont forget this diffuse
structure!)
- Motor function helps regulate muscle movements
- Sensory function Reticular activating system
(RAS) - Stimulation ? increased cortical activity
- Inactivation ? sleep
12Reticular Activating System
- RAS filters out repetitive, weak, irrelevant
stimuli. - LSD removes the filtering effect ?
sensory-overload. - Head Trauma (eg., lightweight boxers)
- ? concussion (mild, transient loss of
consciousness) - ? coma (loss of consciousness, hours to
lifetime).
13The Cerebellum
Figure 147a
14Cerebellum
- Adjusts postural muscles
- Fine-tunes conscious and subconscious movements
15Cerebellar Peduncles
- Three paired fiber tracts
- Superior peduncles connect the cerebellum to the
midbrain - Middle peduncles connect the pons to the
cerebellum - Inferior peduncles connect the medulla to the
cerebellum and carry ascending and descending
cerebellar tracts from the spinal cord. - All fibers in the cerebellum are ipsilateral
16Structures of the Cerebellum
Figure 147b
17Structures of the Cerebellum
- Cerebellar hemispheres
- separated at midline by vermis
- Vermis
- narrow band of cortex
- Flocculonodular lobe
- below fourth ventricle
18Structures of the Cerebellum
- Folia
- surface of cerebellum
- highly folded neural cortex
- Anterior and posterior lobes
- separated by primary fissure
19Arbor Vitae
Cerebellum
20Arbor Vitae
- Highly branched, internal white matter of
cerebellum - Cerebellar nuclei
- embedded in arbor vitae
- relay information to Purkinje cells
21Purkinje Cells
- Large, branched cells
- Found in cerebellar cortex
- Receive input from up to 200,000 synapses
22Disorders of the Cerebellum
- Ataxia
- damage from trauma or stroke
- intoxication (temporary disturbance)
- disturbs muscle coordination
23Summary The Cerebellum
Table 14-3
24What are the main components of the diencephalon
and their functions?
25The Diencephalon
- Integrates sensory information and motor commands
- Filters ascending sensory information for primary
sensory cortex - Relays information between basal nuclei and
cerebral cortex
Figure 145a
26The Diencephalon
- Thalamus, epithalamus, and hypothalamus
Figure 149
27The Third Ventricle
- Separates left thalamus and right thalamus
- Intermediate mass
- projection of gray matter
- extends into ventricle from each side
28Thalamic Nuclei
- Lateral geniculate nucleus relays visual
information - Medial geniculate nucleus relays auditory
information - Lateral group involved in emotional states and
integration of sensory information
29Summary Thalamic Nuclei
Table 14-5
30Hypothalamus
- Located below the thalamusit caps the brainstem
and forms the inferolateral walls of the third
ventricle - Mammillary bodies
- Small, paired nuclei Relay station for
olfactory pathways - control reflex eating movements
- Infundibulum stalk of the hypothalamus
connects to the pituitary gland
31The DiencephalonHypothalamus
Diencephalon
32The Hypothalamus
Figure 1410a
338 Functions of the Hypothalamus
- Provides subconscious control of skeletal muscle
- Controls autonomic function
- Coordinates activities of nervous and endocrine
systems
34Functions of the Hypothalamus
- Secretes hormones
- antidiuretic hormone (ADH) by supraoptic nucleus
- oxytocin (OT) by paraventricular nucleus
35Functions of the Hypothalamus
- Produces emotions and behavioral drives
- the feeding center (hunger)
- the thirst center (thirst)
36Functions of the Hypothalamus
- Coordinates voluntary and autonomic functions
- Regulates body temperature
- preoptic area of hypothalamus
37Functions of the Hypothalamus
- Controls circadian rhythms (daynight cycles)
- suprachiasmatic nucleus
38Summary The Hypothalamus
Table 14-6
39Epithalamus
Pineal Gland
- Above the thalamus
- Pineal gland
- secretes melatonina hormone involved with sleep
regulation, sleep-wake cycles, and mood
40Questions?
41Cerebrospinal Fluid (CSF)
- 80-150 ml (about ½ cup)
- Clear liquid containing glucose, proteins, ions
- Functions
- mechanical protection
- floats brain softens impact with bony walls
- chemical protection
- optimal ionic concentrations for action
potentials - circulation
- nutrients and waste products to and from blood
42CSF Composition
- Differs from plasma
- no (or very few) cells
- protein is lower
- ionic concentrations are different
- pH ? affects brain blood flow
- respiratory rate.
43Blood Brain Barrier
- Ependymal cells around choroid plexus (which
produce CSF) have tight junctions. - Capillaries of brain tissue have tight junctions
between endothelial cells. - Astrocytes wrap the small vessels.
- Many antibiotics and chemotherapy agents can not
pass from blood to brain.
44Blood Brain Barrier details to know
- Break-Down
- radiation, infection, neoplasm (cancer), manitol
(intentional disruption) - facilitated diffusion
- glucose, amino acids
- simple diffusion
- Small, neutrally charged molecules (i.e., lipid
soluble - molecules) pass easily.
- Water, CO2, O2,
- alcohol, caffeine, nicotine, heroin
- general anesthetics
45Brain Blood Flow
- Sources
- 2 internal carotids (R and L)
- 2 vertebral arteries and Circle of Willis
- (Study in more detail in lab.)
- 14 of cardiac output, and uses 20 of oxygen
used by body
46Brain Blood Flow
47Brain Blood Flow
- Flow depends on CO2 more than O2 concentration
- High CO2 ? increased blood flow
- Low CO2 ? decreased blood flow
- Hyperventilation ? blow off CO2 ? low blood flow
? dizzy spell -
- Other Factors extreme blood pressures
- intracranial pressure
- blood viscosity
48Brain Blood Flow Clinical Issues
- Low blood sugar (eg., too much insulin) starves
neurons - Mass (tumor, blood clot) ? decreased flow
- Heart attack ? decreased flow and confusion
- 10 seconds without blood ? pass out
- 4 minutes ? permanent brain damage
- lysosomes release enzymes
49Medical Example Subdural Hematoma
An subdural hematoma is a blood collection
Between the dura and arachnoid mater (external to
the brain) Since the skull cannot expand, the
brain shifts across the midline.
50Clinical CasesBleeding in the Brain
- Epidural Bleed
- Subdural Hematoma
- Intraparenchymal Bleed
51Clinical CasesBleeding in the Brain
- Epidural Bleed
- Subdural Hematoma
- Intraparenchymal Bleed
52Clinical CasesBleeding in the Brain
- Epidural Bleed
- Subdural Hematoma
- Intraparenchymal Bleed(s)
53Medical Examples
- Meningitis is inflammation of the meninges due to
bacterial or viral infection. - Encephalitis is inflammation of the brain
54Parkinsons Disease
- Unknown cause.
- Basal ganglia involved.
- Tremor, rigidity.
- New therapy.
55Basal Ganglia
- Connections to red nucleus, substantia nigra
subthalamus - Input output with cerebral cortex, thalamus
hypothalamus - Control large automatic movements of skeletal
muscles
56The Electroencephalogram
Figure 1417
57Seizure
- Is a temporary cerebral disorder
- Changes the electroencephalogram
- Symptoms depend on regions affected
584 Categories of Brain Waves
- Alpha waves
- found in healthy, awake adults at rest with eyes
closed - Beta waves
- higher frequency
- found in adults concentrating or mentally
stressed
594 Categories of Brain Waves
- Theta waves
- found in children
- found in intensely frustrated adults
- may indicate brain disorder in adults
- Delta waves
- during sleep
- found in awake adults with brain damage
60Synchronization
- A pacemaker mechanism
- synchronizes electrical activity between
hemispheres - Brain damage can cause desynchronization
61Herpes Virus
- CN V (trigeminal)
- Dermatomes
62Next time
- Special Senses and Cranial Nerves (not on
pre-midterm) - Review of somatic sensory and motor pathways
- Integration areas of the brain
- Limbic system
- Learning and Memory
63end