Ch 14- Brain & Cranial
Nerves
Protection
1.
2.
Bones of the cranium
Cranial meninges- Are continuous with spinal meninges
• Protect the brain from cranial trauma (head injury resulting from impact with
another object)
• 3 layers
• Pia mater• Arachnoid mater• Dura mater
• 2 layers – outer layer fused to periosteum of cranial bones
• Outer and inner layer separated by gap where fluids and BVs are located
• Dural folds: Inward folding of inner layer of dura mater
• Provides additional stabilization and support (seatbelt)
• Falx celebri
• Tentorium cerebelli
• Falx cerebelli
• Dural sinuses: large collecting veins within dural folds, includes
superior/inferior sagittal sinus and transverse sinus
Severe Head Injuries
• Bleeding in cranial cavity can result in:
• Epidural hemorrhage- cranial artery breaks and blood is forced between dura
mater and cranial cavity =
• Cranial vein break = delay in symptoms; fatal if not treated
• Subdural hemorrhage: blood enters inner layer of dura mater from small
vein/dural sinuses; delay in symptoms
• Pool of blood forming outside of damaged vessel =
Protection
3. Cerebrospinal Fluid
• circulation- exchange of nutrients & waste, through ventricles/central canal
• CSF reaches subarachnoid space and flows around brain, spinal cord and cauda equina
• CSF fluid is absorbed into venous circulation at arachnoid granulations and returns to choroid plexus
Hydrocephalus• Occurs when too much reabsorption of CSF in infants
• Caused by genetics, trauma, meningitis, tumor, or
hemorrhage
Ventricles- filled with CSF
• 1& 2. Lateral• 3. Third• 4. Fourth-
• Blood Supply to the Brain
• Supplies nutrients and oxygen to brain
• Delivered by
• Removed from
• Blood–Brain Barrier (BBB)
• Isolates CNS neural tissue from general circulation• Only
compounds (O2, CO2), steroids, and
prostaglandins can diffuse into interstitial fluid of CNS
• Have to choose a treatment that will cross, ex: tetracycline cannot break through to treat
meningitis
• Controlled by
• 4 breaks (allows hormones to enter):
• Blood–CSF Barrier
•
•
•
•
Formed by
Surrounds capillaries of
Limits movement of compounds transferred
Allows chemical composition of blood and CSF to differ
A. Brain Stem
• 1. Medulla Oblongata-.
• pyramids- bulges, largest motor tracts cross over
• Relay to thalamus
• sensory & motor b/w brain & s.c.
• Motor: muscles of pharynx, neck, back, & viscera of thoracic/peritoneal cavity
• Autonomic controls: Reticular Formation-
Brain Stem
2. Pons
• Sensory/Motor:
• Respiration:
• Link cerebellum w/brain stem, cerebrum, spinal cord
Brain Stem
3. Midbrain/Mesencephalon- elevations
• Corpora Quadrigemina:
• superior colliculi• inferior colliculi-
• Red nucleus & Substantia Nigra• Reticular Activating System-
Cerebellum- 2nd largest
• cerebellar hemispheres (lobes) & central vermis
•
Peduncles-link to brainstem
Problems with Cerebellum
• Ataxia• Inability to sit or stand without assistance
• From trauma, stroke, drugs (alcohol)
Diencephalon- integration of
sensory with motor
1. Thalamus- relay station
2. Epithalamus- roof
-Pineal gland-
3. Subthalamus-
Diencephalon
4. Hypothalamus
•
Limbic system- “emotional brain”
Hypothalamus, pituitary, amygdala, and hippocampus
HippocampusAmygdalaHypothalamus-
Charles Whitman
• engineering student and retired U.S.
Marine
• He killed his wife and mother before
going to the top of the University of
Texas tower and opened fire on
persons crossing the campus and on
nearby streets. He ended up killing
16 people and wounded 31, before
being killed by police officers. The
shooting spree lasted 96 minutes.
• Post-mortem revealed a brain
tumor near his amygdala.
• http://www.youtube.com/watch?v=
TtOQnM3LQkE
Cerebrum- largest
• Corpus callosum• divided by lobes-parts of skull
bones
• Basal ganglia-
Cerebral Features:
• Gyri –
• Sulci –
– Central Sulcus (Fissure of Rolando) – Divides the Frontal
Lobe from the Parietal Lobe
• Fissures –
– Longitudinal Fissure – Divides the two Cerebral Hemispheres
– Transverse Fissure – Separates the Cerebrum from the
Cerebellum
– Sylvian/Lateral Fissure – Divides the Temporal Lobe from the
Frontal and Parietal Lobes
Gyri (ridge)
Sulci
(groove)
Fissure
(deep
groove)
http://williamcalvin.com/BrainForAllSeasons/img/bonoboLH-humanLH-viaTWD.gif
Specific Sulci/Fissures:
Central Sulcus
Longitudinal Fissure
Sylvian/Lateral
Fissure
Transverse Fissure
Lobes of the Brain (4)
• Frontal
• Parietal
• Occipital
• Temporal
* Note: Occasionally, the Insula is considered the fifth lobe. It is located deep
to the Temporal Lobe.
The lobes of the cerebral hemispheres
Planning, decision
making speech
Sensory
Auditory
Vision
Lobes of the Brain - Frontal
• The Frontal Lobe of the brain is located deep to the
Frontal Bone of the skull.
• It plays an integral role in the following functions/actions:
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-
Phineas Gage
• 1848- Working on Railroad
• Tamping iron sent through skull
• Quick recovery but never the same
• Before: capable, efficient, best foreman
• After: anti-social, liar, grossly profane – WHY??
• Joins the circus & died 12 years later
Frontal Lobe - Cortical Regions
• Primary Motor Cortex (Precentral Gyrus) – Cortical site involved
with controlling movements of the body.
• Broca’s Area –
– Broca’s Aphasia –
• Orbitofrontal Cortex – Site of Frontal Lobotomies
* Desired Effects:
- Diminished Rage
- Decreased Aggression
- Poor Emotional
Responses
• Olfactory Bulb -
* Possible Side Effects:
- Epilepsy
- Poor Emotional Responses
- Perseveration (Uncontrolled, repetitive
actions, gestures, or words)
Primary Motor
Cortex/ Precentral
Gyrus
Broca’s Area
Orbitofrontal
Cortex
Olfactory Bulb
Regions
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Lobes of the Brain - Parietal Lobe
• The Parietal Lobe of the brain is located deep to the
Parietal Bone of the skull.
• It plays a major role in the following functions/actions:
-
Parietal Lobe - Cortical Regions
• Primary Somatosensory Cortex (Postcentral
Gyrus) – Site involved with processing of tactile
and proprioceptive information.
• Somatosensory Association Cortex - Assists
with the integration and interpretation of
sensations relative to body position and orientation
in space. May assist with visuo-motor coordination.
• Primary Gustatory Cortex – Primary site
involved with the interpretation of the sensation of
Taste.
Primary
Somatosensory
Cortex/
Postcentral Gyrus
Somatosensory
Association Cortex
Primary Gustatory
Cortex
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Lobes of the Brain – Occipital Lobe
• The Occipital Lobe of the Brain
is located deep to the Occipital
Bone of the Skull.
Occipital Lobe – Cortical Regions
• Primary Visual Cortex – This is the primary area of
the brain responsible for sight -recognition of size,
color, light, motion, dimensions, etc.
• Visual Association Area – Interprets
information acquired through the primary visual
cortex.
Primary Visual
Cortex
Visual
Association Area
Lobes of the Brain – Temporal Lobe
• The Temporal Lobes are located on the sides of the
brain, deep to the Temporal Bones of the skull.
• They play an integral role
in the following functions:
Temporal Lobe – Cortical Regions
• Primary Auditory Cortex – Responsible for hearing
• Primary Olfactory Cortex – Interprets the sense of
smell once it reaches the cortex via the olfactory
bulbs. (Not visible on the superficial cortex)
• Wernicke’s Area –
- Wernicke’s Aphasia –
Primary Auditory
Cortex
Wernike’s Area
Primary Olfactory
Cortex (Deep)
Conducted from Olfactory Bulb
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Regions
• Arcuate Fasciculus - A white matter tract that connects Broca’s Area and
Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows
for coordinated, comprehensible speech. Damage may result in:
- Conduction Aphasia -
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Fusiform gyrus in Temporal Lobe
The Cerebral Cortex
• Frontal (Forehead to top) 
• Parietal (Top to rear) 
• Occipital (Back) 
• Temporal (Above ears) 
Sensory Areas – Sensory Homunculus
Hemispheric Lateralization
Left
Right
Contra-lateral division of labor
Problems with the Brain
• Contusion• Concussion• Aneurysm• Embolism• Stroke• Alzheimer’s• Apraxia• Ex: comb hair with a fork
• Parkinson’s• resting tremors, loss of voluntary movement
Electroencephalogram (EEG)
• Monitors brain activity
• Typical brain waves
• Alpha waves: occur in brains of
healthy, awake adults resting with
eyes close
• Beta waves: occur during intense
concentration, stress,
psychological tension
• Theta waves: occur during sleep in
normal adults, children, frustrated
adults
• Delta waves: seen during deep
sleep, infants and awake adults
when tumor, vascular blockage,
inflammation has caused damage
Seizure
• Is a temporary cerebral disorder
• Changes the electroencephalogram
• Symptoms depend on regions affected
Imaging
• MRI-
• Positron Emission Tomography/PET-
https://www.youtube.com/watch?v=qabTdk928eQ&list=PLw2f
LCAnU7j7Xr_9sl6XEGW2MyyfwM0Kb&index=1