BRAIN & CRANIAL NERVES
The brain and spinal cord
develop from ectoderm
The brain and spinal cord develop
from the neural tube
• Prosencephalon (Forebrain)
• Mesencephalon ( Midbrain)
• Rhombencephalon (Hindbrain)
• Primary brain vesicles are present around
the 3rd week of development
Prosencephalon (forebrain)
• Differentiates in 5th week into:
• Telencephalon
–cerebral hemispheres
• Diencephalon
–thalamus; hypothalamus
–pineal gland
Midbrain
• Mesencephalon remains the same
• Brainstem = midbrain
Rhombencephalon
• Metencephalon
–cerebellum, pons
• Myelencephalon
–medulla oblongata
Meninges
• Dura mater
–dural septa (extensions): falx cerebri, falx
cerebelli, tentorium cerebelli
• Arachnoid
• Pia mater
• Cavities
–subarachnoid space, subdural space
4 Ventricles filled with CSF
• Lateral ventricles (paired)
–Interventricular foramen – connects to 3rd
ventricle
• Third ventricle
–Cerebral aqueduct – connects 3rd and 4th
ventricles
• Fourth ventricle
–Connects with central canal of spinal cord
Cerebrospinal Fluid
• Clear, colorless fluid that protects
brain
• Formed by the choroid plexus
• Absorbed by arachnoid villi
Parts of the Brain
Medulla oblongata
• Major reflex center for the cardiovascular and
respiratory system
– vasomotor, vasoconstriction
• Pyramids - decussation (crossing) center for
motor `tracts
• Non-vital center for coughing, hiccuping,
swallowing, vomiting
• Ascending/descending fibers pass through
• Cranial nerves VIII-XII arise here
PONS
• Acts as a bridge connecting the
spinal cord to the brain
• Major relay center for voluntary
skeletal movements from the
cerebral cortex to the cerebellum
• Coordinates with the medulla to
regulate respiration
• Cranial nerves V-VIII emerge here
Midbrain
• Corpora quadrigemina
–Visual and auditory reflex centers
• Cerebral peduncles - containing large
fiber tracts going to and from the brain
• Houses the cerebral aqueduct
• Cranial Nerves III-IV emerge here
Thalamus
• Two halves connected by the
intermediate mass
• Relay center for ALL sensory cranial
and spinal nerves
• Interpretation center for crude
awareness of pain, temperature and
pressure
• Location of 3rd ventricle
Hypothalamus
• Links the nervous system and
endocrine system
• Major regulator of homeostasis
• Regulates many ANS functions
• Regulates appetite, water balance,
thirst, body temperature
• Emotional part of brain - pleasure,
fear, rage
Cranial Nerves
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12 Pairs
1 Olfactory 2. Optic 3. Oculomotor 4. Trochlear 5. Trigeminal 6. Abducens -
smell
sight
eye movements
eye movements
eyes & face, chewing
eyes
Cranial Nerves (continued)
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7. Facial 8. Vestibulocochlear 9. Glossopharyngeal 10. Vagus 11. Accessory 12. Hypoglossal -
facial expression, taste
equilibrium, hearing
tonge & swallowing
heart, visceral organs
neck & back
tongue
Cerebellum
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Second largest area of the brain
2 cerebellar hemispheres
Arbor vitae - branchlike pattern
Vermis - wormlike structure that
connects left & right side
• Major coordination of skeletal muscle
contraction
• Assists with posture and balance
Cerebrum
• Cerebral cortex - outer layer of gray matter
• Two hemispheres separated by longitudinal
fissure
• Gyri - ridges on surface
• Sulci - grooves on surface
• Fissures
• Septum pellucidum - thin wall between
ventricles
Lobes of the Brain
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Frontal
Parietal
Occipital
Temporal
Central sulcus
Lateral sulcus
Cerebral Dominance
• Left hemisphere
–Language
–Logic
–Math
• Right Hemisphere
–Artistic
–Musical
–Creative
Cerebral Cortex Specialization
• Motor Areas
–Control opposite side of body
–Control voluntary motor functions
• Sensory Areas
–Detect sensations from opposite side of
body
• Association Areas
–Integrate diverse information into
purposeful action
Association Areas
• Prefrontal Cortex – intellect, learning, &
personality
• Language Areas
–Wernicke’s area – sounding out new words
–Brocas’s area – speech
• General Interpretation
• Visceral Interpretation
Basal Ganglia
• Cerebral nuclei
• Islands of gray matter located deep within the
white matter
• Function: controls large automatic skeletal
muscle movements and produce dopamine
White Matter
• Commissural fibers (corpus callosum) connect corresponding parts of two
hemispheres
• Association fibers - connect within the same
hemisphere
• Projection fibers (higher centers to lower
ones)
Limbic System
• Includes part of thalamus, hypothalamus, and
cerebrum
• Emotional brain
• Associated with memory
• Involuntary behavior for survival
• Pleasure and pain centers - fear, sorrow,
affection
Reticular Formation
• RAS System - reticular activating system
• Network of gray matter extending from the
medulla, pons, midbrain into the cortex
• Maintains consciousness
• Awaken from sleep
• Alerts brain of incoming sensory signals