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Anatomy & Physiology I
Chapter 10
Cerebrum
Cerebral hemispheres
Diencephalon
Thalamus
Hypothalamus
Brain stem
Midbrain
Pons
Medulla oblongata
Cerebellum
Corpus callosum
Thalamus
Hypothalamus
Midbrain
Pons
Medulla
oblongata
Cerebellum
Cerebral cortex – outer layer of gray matter
Gyri – elevated ridges
Sulci – shallow grooves
Fissures – deep grooves
Five Lobes
Frontal
Parietal
Temporal
Occipital
Insula (within the hemisphere)
External
surface of
the brain,
superior
view.
The division
into two
hemispher
es and into
lobes is
visible.
Surface markings
Central sulcus
Separates the frontal lobe and the parietal lobe
Longitudinal fissure
Separates the two hemispheres
Lateral sulcus
Separates the temporal lobe from the frontal and parietal
Transverse cerebral fissure
Separates the cerebrum and the cerebellum
Precentral gyrus
Immediately anterior to the central sulcus
Postcentral gyrus
Immediately posterior to the central sulcus
Precentral gyrus
Frontal lobe
Central
sulcus
Postcentral gyrus
Parietal lobe
Lateral sulcus
Occipital lobe
Temporal lobe
Transverse cerebral fissure
Cerebellum
Fissure
Gyrus
Cortex (gray matter)
Sulcus
White matter
Frontal lobe
Central
sulcus
Gyri of insula
Temporal lobe
(pulled down)
Figure 12.6b
Anterior
Longitudinal
fissure
Frontal lobe
Cerebral veins
and arteries
covered by
arachnoid
mater
Parietal
lobe
Right cerebral
hemisphere
Occipital
lobe
Left cerebral
hemisphere
Posterior
Figure 12.6c
three connective tissue membranes that
envelop the brain and spinal cord
lies between the nervous tissue and bone
protect the brain and provide structural framework
for its arteries and veins
Dura mater – outer layer
Dural sinuses - collect blood circulating
through brain
Arachnoid mater – middle layer
Pia mater – innermost layer (adheres to brain)
Skull
Dura mater
Subdural space
Subarachnoid
space
Arachnoid mater
Pia mater
Cerebrum:
Gray matter
White matter
Terminology: What’s The Meaning?
• Epidural
• Subdural
• Subarachnoid
inflammation of the meninges
serious disease of infancy & childhood; especially between 3
months and 2 years of age
caused by bacterial and virus invasion of the CNS by way
of the nose and throat
bacterial meningitis can cause swelling the brain,
enlarging the ventricles, and hemorrhage
signs include high fever, stiff neck, drowsiness, and
intense headache and may progress to coma – death
within hours of onset
diagnosed by examining the CSF for bacteria
lumbar puncture (spinal tap) draws fluid from subarachnoid
space between two lumbar vertebrae
14-14
Clear fluid found in and around the brain and
spinal cord
Formed by choroid plexus in ventricles
Absorbed into bloodstream by arachnoid villi
CSF provides these functions:
Buoyancy
Protection
Chemical stability
buoyancy
allows brain to attain considerable size without being
impaired by its own weight
if it rested heavily on floor of cranium, the pressure
would kill the nervous tissue
protection
protects the brain from striking the cranium when the
head is jolted
shaken child syndrome and concussions do occur from
severe jolting
chemical stability
flow of CSF rinses away metabolic wastes from nervous
tissue
14-16
Path of CSF through ventricles:
Lateral ventricles
Interventricular foramen
3rd ventricle
Cerebral aqueduct
4th ventricle
CSF then continues through the central canal
(spinal cord) and outside the brain and spinal cord
About 500ml of CSF is produced and drained
from the CNS daily
What happens if production and drainage are not
balanced?
Arachnoid villus
8
Superior
sagittal
sinus
Arachnoid mater
1 CSF is secreted by
choroid plexus in
each lateral ventricle.
2 CSF flows through
Interventricular foramina
into third ventricle.
3 Choroid plexus in third
ventricle adds more CSF.
4 CSF flows down cerebral
aqueduct to fourth ventricle.
Subarachnoid
space
Dura mater
1
2
Choroid plexus
Third ventricle
3
7
4
5 Choroid plexus in fourth
ventricle adds more CSF.
6 CSF flows out two lateral apertures
and one median aperture.
7 CSF fills subarachnoid space and
bathes external surfaces of brain
and spinal cord.
8 At arachnoid villi, CSF is reabsorbed
into venous blood of dural
venous sinuses.
Cerebral
aqueduct
Lateralaper ture
Fourth ventricle
6
5
Median aperture
7
Centralcanal
of spinal cord
Subarachnoid
space of
spinal cord
Frontal lobe
Motor area
Speech centers
Parietal lobe
Sensory area
Estimation of distances, sizes, shapes
Temporal lobe
Auditory area
Olfactory area
Occipital lobe
Visual receiving area
Visual association area
ZOOMING IN
• What cortical
area is posterior
to the central
sulcus? What
area is anterior
to the central
sulcus?
Auditory areas
Auditory receiving
Auditory association
Speech comprehension (Wernicke area)
Motor areas
Motor speech (Broca area)
Written speech center
Visual areas
Visual language images receiving
Short-term memory
Information retain for few seconds to
minutes; lost unless reinforced
Long-term memory
Transfer of short term memory to long term
memory requires rehearsal (repetition)
Information stored for later recall
Requires mental alertness
Procedural Memory
Motor (physical) memory of movements
Tying shoes, typing, playing instruments, sports
Thalamus
Sorts sensory impulses
Directs impulses within cerebral cortex
Hypothalamus
Maintains homeostasis
Controls sympathetic and parasympathetic
divisions of autonomic nervous system
Influences heartbeat, blood flow, hormone
secretion
Regions of the diencephalon. The figure shows the relationship among the
thalamus, hypothalamus, and pituitary gland (hypophysis).
ZOOMING IN • To what part of the brain is the pituitary gland attached?
Networks of neurons that work together and
span wide areas of the brain
Limbic system – Emotional Brain
Includes the amygdala, cingulate gyrus and
hippocampus
Reticular formation – Consciousness
Mass of gray matter extending through the
entire brainstem
Thalamic Nuclei
Corpus callosum
•Hypothalamus
•Cingulate gyrus
•Amygdala
•Hippocampus
Olfactory bulb
Includes centers for both gratification and aversion
gratification – sensations of pleasure or reward
aversion – sensations of fear or sorrow
Emotional or affective brain
Amygdala—recognizes angry or fearful facial
expressions, assesses danger, and elicits the fear
response
Cingulate gyrus—plays a role in expressing
emotions via gestures, and resolves mental conflict
Hippocampus – plays a significant role in learning
and memory formation
Puts emotional responses to odors
Example: skunks smell bad
Hippocampus and amygdala—play a role in
memory
plays central role in states of consciousness,
such as alertness and sleep
Consciousness is a state of wakefulness
Very sensitive to the effects of certain drugs and
alcohol
Combination of tranquilizers and alcohol can
damage the reticular formation, causing permanent
unconsciousness
Consciousness depends on the reticular
activating system (RAS)
Reticular Formation
Visual
impulses
Radiations
to cerebral
cortex
Auditory
impulses
Reticular formation
Ascending general
sensory tracts
(touch, pain, temperature)
Descending
motor projections
to spinal cord
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)
Nuclei that control cranial nerves III and IV
Superior part of brain stem
Reflexes involving eyes and ears
substantia nigra
dark gray to black nucleus pigmented with melanin
motor center that relays inhibitory signals to
thalamus & basal nuclei preventing unwanted body
movement
degeneration of neurons leads to tremors of
Parkinson disease
Forms part of the anterior wall of the fourth ventricle
Fibers of the pons
Connect higher brain centers and the spinal cord
Relay impulses between the motor cortex and the
cerebellum
Origin of cranial nerves V, VI, VII and VIII
Nuclei that help maintain normal rhythm of breathing
reticular formation in pons contains additional nuclei
concerned with:
sleep, respiration, and posture
cardiac center
adjusts rate and force of heart
vasomotor center
adjusts blood vessel diameter
respiratory centers
control rate and depth of breathing
reflex centers
for coughing, sneezing, gagging, swallowing,
vomiting, salivation, sweating
Location of cranial nerves - IX, X, XI, XII
Three parts
Vermis
Left hemisphere
Right hemisphere
Functions
Help coordinate voluntary muscles
Help maintain balance
Help maintain muscle tone
(A) Posterior view
showing the two
hemispheres.
(B) Midsagittal
section showing
the distribution of
gray and white
matter.
The three parts of the
brain stem
(midbrain, pons,
and medulla
oblongata) are
also labeled.
Cerebellum receives impulses from the cerebral cortex
of the intent to initiate voluntary muscle contraction
Signals from proprioceptors and visual and equilibrium
pathways continuously “inform” the cerebellum of the
body’s position and momentum
Cerebellar cortex calculates the best way to smoothly
coordinate a muscle contraction
A “blueprint” of coordinated movement is sent to the
cerebral motor cortex and to brain stem nuclei
Record electric currents given off by brain nerve
cells
Study sleep patterns
Diagnose disease
Locate tumors
Study drug effects
Determine brain death
Scalp electrodes are used to record brain wave
activity (EEG).
Alpha waves (8–13 Hz)—regular and rhythmic, lowamplitude, synchronous waves indicating an “idling”
brain
Beta waves (14–30 Hz)—rhythmic, less regular waves
occurring when mentally alert
Theta waves (4–7 Hz)—more irregular; common in
children and uncommon in adults
Delta waves (4 Hz or less)—high-amplitude waves seen
in deep sleep and when reticular activating system is
damped, or during anesthesia; may indicate brain
damage
1-second interval
Alpha waves—awake but relaxed
Beta waves—awake, alert
Theta waves—common in children
Delta waves—deep sleep
(b) Brain waves shown in EEGs fall into
four general classes.
Figure 12.20b
Change with age, sensory stimuli, brain disease,
and the chemical state of the body
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
Hydrocephalus
Abnormal CSF accumulation within brain
Causes
Congenital malformation
Tumor
Inflammation
Hemorrhage
Encephalitis
Inflammation of the brain
Viral causes
Toxic substances causes
Viral vaccine causes
Stroke (Cerebrovascular Accident; CVA)
Most common brain disorder
sudden death of brain tissue caused by ischemia
atherosclerosis, thrombosis, ruptured aneurysm
effects range from unnoticeable to fatal
blindness, paralysis, loss of sensation, loss of speech
common
recovery depends on surrounding neurons,
collateral circulation
Tumors
Gliomas – tumor arising from glial cells
Neuroma – tumor arising from nerves
Meningioma – tumors arising from meninges
Cerebral palsy (CP)
Group of neuromuscular disorders that result from injury to
an infant before, during or shortly after delivery.
All forms cause impairment of skeletal muscle activity
Mental retardation and speech difficulty may accompany CP
Epilepsy
Disorder in which neurons of the brain fire suddenly and
unpredictably
May be caused by brain tumors, toxins, trauma, or fever.
Grand mal seizure - motor areas fire repeatedly causing
convulsive seizures and loss of consciousness
Petit mal seizure - sensory areas affected; not accompanied
by convulsions or prolonged unconsciousness
brain is only 2% of the adult body weight, and receives
15% of the blood
750 mL/min
neurons have a high demand for ATP, and therefore,
oxygen and glucose, so a constant supply of blood is
critical to the nervous system
10 second interruption of blood flow may cause loss of
consciousness
1 – 2 minute interruption can cause significant impairment of
neural function
4 minutes with out blood causes irreversible brain damage
14-45
Injury
Head trauma can lead to injury within skull
Epidural hematoma
Subdural hematoma
Intracerebral hematoma
Cerebral concussion
the brain must communicate with the rest
of the body
most of the input and output travels by way of the
spinal cord
12 pairs of cranial nerves arise from the base of the
brain
exit the cranium through foramina
lead to muscles and sense organs located mainly in
the head and neck
14-47
some cranial nerves are classified as motor, some
sensory, others mixed
sensory (I, II, and VIII)
motor
(III, IV, VI, XI, and XII)
stimulate muscle but also contain fibers of proprioception
mixed
(V, VII, IX, X)
sensory functions may be quite unrelated to their motor
function
facial nerve (VII) has sensory role in taste and motor
role in facial expression
14-48
Cranial Nerves
12 pairs
Remember: all nerves (cranial and spinal) carry
signals toward or away from the CNS
Four categories
Special sensory impulses
General sensory impulses
Somatic motor impulses
Visceral motor impulses
Cranial nerves.
The 12 pairs of
cranial nerves
are seen from
the base of the
brain.
The Cranial Nerves (functions)
I. Olfactory – sense of smell
II. Optic – vision
III. Oculomotor – eye movement (innervates most eye
muscles)
IV. Trochlear – eye movement (innervates one eye
muscle; so)
V. Trigeminal – facial sensation
VI. Abducens – eye movement (innervates one eye
muscle; lr)
The Cranial Nerves (functions)
VII. Facial – facial movement (expressions), taste
sensation, saliva and tear secretion
VIII. Vestibulocochlear – sense of hearing and
equilibrium
IX. Glossopharyngeal – tongue and throat
movement (swallowing), saliva secretion
X. Vagus – regulation of viscera; muscles of larynx
& pharynx
XI. Accessory – Swallowing, head, neck and
shoulder movement
XII. Hypoglossal – tongue movement
Trigeminal neuralgia (tic douloureux)
recurring episodes of intense stabbing pain in
trigeminal nerve area (near mouth or nose)
pain triggered by touch, drinking, washing face
treatment may require cutting nerve
Bell palsy
degenerative disorder of facial nerve causes paralysis
of facial muscles on one side
may appear abruptly with full recovery within 3 - 5
weeks
14-53
Decreased brain size and weight
Decreased speed of information processing
Slowed movements
Diminished memory
Reduced blood flow to brain