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- Innermost layer, Sticks to surface of brain, Anchored by astrocytes
• Arachnoid mater- Subarachnoid space separates arachnoid and pia mater, where CSF
circulates
• 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 (separates cerebral hemispheres)
• Tentorium cerebelli (protects cerebellar hemispheres)
• Falx cerebelli (separates cerebellar hemispheres)
• 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 = increase in pressure = distortion of brain tissue =
loss of consciousness
• 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 = subdural hematoma
Protection
3. Cerebrospinal Fluid
• carries oxygen & glucose
• mechanical protection- shock absorber, buoys the brain
• chemical protection- accurate amount of ion concentration for signals
• produced in choroid plexuses-from ependymal cells
• 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- water on the brain
• Occurs when too much reabsorption of CSF in infants
• Caused by genetics, trauma, meningitis, tumor, or
hemorrhage
Ventricles- filled with CSF
• 1& 2. Lateral- each side of cerebrum,
separated by septum pellucidum
• 3. Third- b/w rt. & left sides of thalamus
• 4. Fourth- b/w brain stem & cerebellum
• Blood Supply to the Brain
• Supplies nutrients and oxygen to brain
• Delivered by internal carotid arteries and vertebral arteries
• Removed from dural sinuses by internal jugular veins
• Blood–Brain Barrier (BBB)
• Isolates CNS neural tissue from general circulation- tight junctions
• Only lipid-soluble 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 Astrocytes
• 4 breaks (allows hormones to enter): hypothalamus, pituitary gland, pineal gland,
choroid plexus
• Blood–CSF Barrier
•
•
•
•
Formed by special ependymal cells
Surrounds capillaries of choroid plexus
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-from medulla to midbrain
• Cardiovascular center (heart rate, blood vessels) & Respiratory rhythmicity center
(respiratory pace, reflexes for vomiting, coughing, sneezing)
Brain Stem
2. Pons
• Sensory/Motor: jaw, face, eye muscle & internal ear
• Respiration: Apneustic & pneumotaxic- monitors medulla
• Link cerebellum w/brain stem, cerebrum, spinal cord
Brain Stem
3. Midbrain/Mesencephalon- elevations
• Corpora Quadrigemina:
• superior colliculi- movements of eyes, head, & neck in response to vision
• inferior colliculi-movements of head & trunk in response to hearing
• Red nucleus & Substantia Nigra- subconscious muscle activities (posture),
• Reticular Activating System- alert & attentive
Cerebellum- 2nd largest
• cerebellar hemispheres (lobes) & central vermis (separates lobes)
• evaluates how well movements are being carried out, makes muscle
contractions smooth
• posture & balance
Peduncles-link to brainstem
Problems with Cerebellum
• Ataxia- disturbance in muscular coordination
• Inability to sit or stand without assistance
• From trauma, stroke, drugs (alcohol)
Diencephalon- integration of
sensory with motor
1. Thalamus- relay station
• sensory impulses (touch, pain, temp, pressure,
proprioception (position))
• Influences emotional state
• Projects visual & auditory information
• Part of limbic system
2. Epithalamus- roof
-Pineal gland- melatonin (day-night cycles)
3. Subthalamus- body movements
Diencephalon
4. Hypothalamus
• Subconscious control of skeletal muscle associated with rage, pleaure, pain, &
sexual arousal
• control of ANS- contraction of smooth & cardiac muscle
• Inhibits or stimulates Pituitary gland- hormones (HGH, LH, FSH,
TSH(metabolism)), connected by infundibulum
• Secretes 2 hormones
• ADH-water balance, blood pressure
• Oxytocin- smooth muscle contractions of uterus & mammary glands
• Satiety (hunger) & thirst centers
• body temperature
• circadian rhythms- sleep schedule
Limbic system- “emotional brain”
Hypothalamus, pituitary, amygdala, and hippocampus
Hippocampus-long term memory
Amygdala- emotions (fear, aggression, sex & pleasure)
Hypothalamus- hunger, thirst, body temp, pleasure
Charles Whitman
• engineering student and retired U.S.
Marine
• 1966-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=Tt
OQnM3LQkE
Cerebrum- largest
• “seat of intelligence”- read, write,
speak, memory, imagination
• Corpus callosum- division between the
hemispheres
• divided by lobes-parts of skull bones
• Basal ganglia- control automatic
movements of skeletal muscle,
(swinging arms while walking,
laughing), muscle tone
Cerebral Features:
• Gyri – Elevated ridges “winding” around the brain.
• Sulci – Small grooves dividing the gyri
– Central Sulcus (Fissure of Rolando) – Divides the Frontal
Lobe from the Parietal Lobe
• Fissures – Deep grooves, generally dividing large
regions/lobes of the brain
– 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:
- Memory Formation
- Emotions
- Decision Making/Reasoning
- Personality
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
http://www.youtube.com/watch?v=9QXI_BxlY7M
Frontal Lobe - Cortical Regions
• Primary Motor Cortex (Precentral Gyrus) – Cortical site involved
with controlling movements of the body.
• Broca’s Area – Controls facial neurons, speech, and language
comprehension. Located on Left Frontal Lobe.
– Broca’s Aphasia – Results in the ability to comprehend speech, but
the decreased motor ability (or inability) to speak and form words.
• Orbitofrontal Cortex – Site of Frontal Lobotomies
* Desired Effects:
- Diminished Rage
- Decreased Aggression
- Poor Emotional
Responses
* Possible Side Effects:
- Epilepsy
- Poor Emotional Responses
- Perseveration (Uncontrolled, repetitive
actions, gestures, or words)
• Olfactory Bulb - Cranial Nerve I, Responsible for sensation of Smell
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:
- Senses and integrates sensation(s)
- Spatial awareness and perception
(Proprioception - Awareness of
body/ body parts in space and
in relation to each other)
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.
• Its primary function is the
processing, integration,
interpretation, etc. of VISION and
visual stimuli.
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:
- Hearing
- Organization/Comprehension
of language
- Information Retrieval
(Memory and Memory Formation)
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 – Language comprehension.
Located on the Left Temporal Lobe.
- Wernicke’s Aphasia – Language comprehension is
inhibited. Words and sentences are not clearly
understood, and sentence formation may be inhibited or
non-sensical.
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 - Where auditory comprehension and speech
articulation are preserved, but people find it difficult to repeat heard
speech.
Modified from: http://www.bioon.com/book/biology/whole/image/1/1-8.tif.jpg
Fusiform gyrus in Temporal Lobe
1.processing of color information
2.face and body recognition
3.word recognition
The Cerebral Cortex
• Frontal (Forehead to top)  Motor Cortex
• Parietal (Top to rear)  Sensory Cortex
• Occipital (Back)  Visual Cortex
• Temporal (Above ears)  Auditory Cortex
Sensory Areas – Sensory Homunculus
Hemispheric Lateralization
Left
• Reading, writing, math
• Decision making
• Speech & language
• Detail
• Literal meaning
Right
• Senses
• Recognition (faces, voice)
• Overall picture
• Spatial perception
• Emotional
• Musical
Contra-lateral division of labor
• Right hemisphere controls
left side of body and visual
field
• Left hemisphere controls
right side of body and visual
field
Problems with the Brain
• Contusion- bruise
• Concussion- temporary loss of consciousness & some amnesia
• Aneurysm- balloon of vessel
• Embolism-something carried to a spot it shouldn’t be (fat)
• Stroke-lack of brain functions because of cut off blood supply
• Alzheimer’s- loss of Ach, causes plaques
• Apraxia- don’t know what to do with something
• Ex: comb hair with a fork
• Parkinson’s- decrease in dopamaine
• resting tremors, loss of voluntary movement
Imaging- 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- Radio waves & magnetic fields to distinguish brain tissue
• Positron Emission Tomography/PET- 3D image of functional
processes in the brain, (not just the structure)
• uses glucose to develop a visual display of brain activity
https://www.youtube.com/watch?v=qabTdk928eQ&list=PLw2f
LCAnU7j7Xr_9sl6XEGW2MyyfwM0Kb&index=1
• Brains from Humans
• https://www.youtube.com/watch?v=_3gKVOeXpxU&list=UUdofq4hH
bT3ZDzgYUqsDd1A&index=36
• https://www.youtube.com/watch?v=bN8oYVilps&index=34&list=UUdofq4hHbT3ZDzgYUqsDd1A
Sheep Brain Dissection
• https://www.youtube.com/watch?v=YRHS0DSox8Y