14-1
Directional Terms and Landmarks
14-2
Cerebrum • longitudinal fissure – deep
groove that separates cerebral hemispheres
• gyri - thick folds
• sulci - shallow grooves
• corpus callosum – thick nerve bundle at bottom of longitudinal fissure that connects hemispheres
Figure 14.1a
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Frontal lobe
Occipital lobe
Central sulcus
Longitudinal fissure
Parietal lobe
(a) Superior view
Cerebralhemispheres
14-3
Cerebellum
• occupies posterior cranial fossa
• marked by gyri, sulci, and fissures
• about 10% of brain volume
• contains over 50% of brain neurons
Figure 14.1b
Brainstem
Cerebellum
Cerebrum
Spinal cord
Rostral Caudal
Central sulcus
Lateral sulcus
Gyri
(b) Lateral view
Temporal lobe
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14-4
Brainstem
• brainstem – what remains of the brain if the cerebrum and cerebellum are removed
• major components
– diencephalon
– midbrain
– pons
– medulla oblongata
Figure 14.1b
Brainstem
Cerebellum
Cerebrum
Spinal cord
Rostral Caudal
Central sulcus
Lateral sulcus
Gyri
(b) Lateral view
Temporal lobe
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14-5
Median Section of the Brain
Figure 14.2a
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leaves
Thalamus
Hypothalamus
Frontal lobe
Corpus callosum
Cingulate gyrus
Optic chiasm
Pituitary gland
Mammillary body
Midbrain
Pons
Central sulcus
Parietal lobe
Parieto–occipital sulcus
Occipital lobe
Pineal gland
Habenula
Posterior commissure
Cerebral aqueduct
Fourth ventricle
Cerebellum
(a)
EpithalamusAnteriorcommissure
Temporal lobe
Medullaoblongata
14-6
Gray and White Matter• gray matter – the seat of neuron cell bodies,
dendrites, and synapses– forms surface layer, cortex, over cerebrum and
cerebellum
– forms nuclei deep within brain
• white matter - bundles of axons– lies deep to cortical gray matter, opposite relationship
in the spinal cord– composed of tracts, bundles of axons, that connect one
part of the brain to another, and to the spinal cord
Embryonic Neural TubeCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
leaves
(a) 19 days
(c) 22 days
Ectoderm
Notochord
Neural groove
Neural fold
Neural plate
(b) 20 days
(d) 26 days
Somites
Neural crestNeural crest
Neuralcrest
Neuraltube
14-7
Figure 14.3
14-8
Meninges of the Brain Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Subdural space
Skull
Pia mater
Blood vessel
Dura mater: Periosteal layer Meningeal layer
Arachnoid mater
Brain:
Gray matter
White matter
Arachnoid villusSubarachnoidspace
Superior sagittalsinus
Falx cerebri(in longitudinalfissure only)
Figure 14.5
14-9
Brain Ventricles
Figure 14.6 a-b
Lateral ventricles
Central canal
Lateral aperture
Fourth ventricle
Third ventricle
Median aperture
(a) Lateral view
Caudal
Interventricularforamen
Cerebralaqueduct
Rostral
Lateral ventricle
Third ventricle
Cerebrum
Lateral aperture
Fourth ventricle
Median aperture
(b) Anterior view
Interventricularforamen
Cerebralaqueduct
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
14-10
Ventricles and Cerebrospinal Fluid• ventricles – four internal chambers within the brain
– two lateral ventricles – one in each cerebral hemisphere – third ventricle - single narrow medial space beneath corpus
callosum– fourth ventricle – small triangular chamber between pons and
cerebellum• connects to central canal runs down through spinal cord
14-11
Cerebrospinal Fluid (CSF)choroid plexus – spongy mass of blood capillaries on the floor of
each ventricleProduced cerebrospinal fluid
ependyma – neuroglia that lines the ventricles and covers choroid plexus
produces cerebrospinal fluid
• cerebrospinal fluid (CSF) – clear, colorless liquid that fills the ventricles and canals of CNS– bathes its external surface
• ependymal cells modify blood filtrate
14-12
Functions of CSF• 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
• chemical stability– flow of CSF rinses away metabolic wastes from nervous
tissue and homeostatically regulates its chemical environment
14-13
Flow of Cerebrospinal FluidCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Choroid plexus in fourthventricle adds more CSF.
CSF flows out two lateral aperturesand one median aperture.
CSF fills subarachnoid space andbathes external surfaces of brainand spinal cord.
At arachnoid villi, CSF is reabsorbedinto venous blood of duralvenous sinuses.
1
2
3
4
56
7
7
8
1
2
3
4
5
6
7
8
CSF is secreted bychoroid plexus ineach lateral ventricle.
CSF flows throughInterventricular foraminainto third ventricle.
Choroid plexus in thirdventricle adds more CSF.
CSF flows down cerebralaqueduct to fourth ventricle.
Arachnoid villus
Superiorsagittalsinus
Arachnoid mater
Subarachnoidspace
Dura mater
Choroid plexus
Third ventricle
Cerebralaqueduct
Lateralaper ture
Fourth ventricle
Median aperture
Centralcanalof spinal cord
Subarachnoidspace ofspinal cordFigure 14.7
14-14
Blood Supply to the Brain
•brain is only 2% of the adult body weight, and receives 15% of the blood•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
14-15
Brain Barrier System• blood is also a source of antibodies, macrophages, bacterial toxins, and
other harmful agents
• brain barrier system – strictly regulates what substances can get from the bloodstream into the tissue fluid of the brain
• blood-brain barrier - protects blood capillaries throughout brain tissue– consists of tight junctions between endothelial cells that form the capillary
walls– astrocytes reach out and contact capillaries with their perivascular feet– induce the endothelial cells to form tight junctions that completely seal off
gaps between them– anything leaving the blood must pass through the cells, and not between
them– endothelial cells can exclude harmful substances from passing to the brain
tissue while allowing necessary ones to pass
14-17
Medulla Oblongata
• 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, movements of tongue and head
14-18
Medulla and PonsCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Diencephalon:
Midbrain:
Thalamus
Optic tract
Cranial nerves:
Oculomotor nerve (III)
Optic nerve (II)
Trochlear nerve (IV)
Trigeminal nerve (V)
Abducens nerve (VI)
Facial nerve (VII)
Vestibulocochlear nerve (VIII)
Glossopharyngeal nerve (IX)
Vagus nerve (X)
Accessory nerve (XI)
Hypoglossal nerve (XII)
Spinal nerves
Infundibulum
Mammillary body
Cerebral peduncle
Pyramid
Anterior median fissure
Pyramidal decussation
Spinal cord
(a) Anterior view
Pons
Medulla oblongata: Regions of the brainstem
Midbrain
Diencephalon
Pons
Medulla oblongata
Figure 14.8a
14-19
Pons
Figure 14.2a
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leaves
Thalamus
Hypothalamus
Frontal lobe
Corpus callosum
Cingulate gyrus
Optic chiasm
Pituitary gland
Mammillary body
Midbrain
Pons
Central sulcus
Parietal lobe
Parieto–occipital sulcus
Occipital lobe
Pineal gland
Habenula
Posterior commissure
Cerebral aqueduct
Fourth ventricle
Cerebellum
(a)
EpithalamusAnteriorcommissure
Temporal lobe
Medullaoblongata
• pons – anterior bulge in brainstem, rostral to medulla
14-20
Pons• ascending sensory tracts
• descending motor tracts
• pathways in and out of cerebellum• reticular formation in pons contains additional
nuclei concerned with:– sleep, respiration, and posture
14-21
Reticular Formation• reticular formation –
loosely organized web of gray matter that runs vertically through all levels of the brainstem
• clusters of gray matter scattered throughout pons, midbrain and medulla
• occupies space between white fiber tracts and brainstem nuclei
• has connections with many areas of cerebrum
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Visual input
Reticular formation
Thalamus
Radiations tocerebral cortex
Ascending generalsensory fibers
Descending motorfibers to spinal cord
Auditory input
Figure 14.10
14-22
Functions of Reticular Formation Networks
• somatic motor control
• cardiovascular control
• pain modulation
• sleep and consciousness
• habituation
14-23
Cerebellum
• the largest part of the hindbrain and the second largest part of the brain as a whole
• consists of right and left cerebellar hemispheres connected by vermis
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leaves
(b) Superior view
Folia
Anterior
Posterior
Anterior lobe
Vermis
Posterior lobe
Cerebellarhemisphere
Figure 14.11b
14-24
Cerebellum
• cerebellar peduncles – three pairs of stalks that connect the cerebellum to the brainstem
– inferior peduncles – connected to medulla oblongata (input)
– middle peduncles – connected to the pons (input)
– superior peduncles – connected to the midbrain (output)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Superior colliculus
Posterior commissure
Pineal glandInferior colliculus
Mammillary bodyMidbrain
Cerebral aqueduct
Oculomotor nerve
Pons
Fourth ventricle
Medulla oblongata
Gray matter
(a) Median section
White matter(arbor vitae)
Figure 14.11a
Input and Output to
Cerebellum
14-26
Cerebellar Functions• monitors muscle contractions and aids in motor
coordination
• evaluation of sensory input– comparing textures without looking at them– spatial perception and comprehension of different views of 3D
objects belonging to the same object
• timekeeping center– predicting movement of objects– helps predict how much the eyes must move in order to
compensate for head movements and remain fixed on an object
• hearing– distinguish pitch and similar sounding words
• planning and scheduling tasks
14-27
The Forebrain
Diencephalon
Mesencephalon
TelencephalonForebrain
Pons
CerebellumMetencephalon
Spinal cord
Hindbrain
(c) Fully developed
Midbrain
Myelencephalon(medulla oblongata)
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• forebrain consists of :– Thalamus– hypothalamus– cerebrum
Figure 14.4c
14-28
Thalamus
• Thalamus– nearly all input to the cerebrum passes by way of synapses in the thalamic nuclei, filters
information on its way to cerebral cortex– motor control - relays signals from cerebellum to cerebrum– memory and emotional functions of the limbic system – includes some cerebral
cortex of the temporal and frontal lobes and some of the anterior thalamic nuclei
14-29
• hypothalamus – forms part of the walls and floor of the third ventricle
– relay signals from the limbic system to the thalamus
• infundibulum – a stalk that attaches the pituitary gland to the hypothalamus
– major control center of autonomic nervous system and endocrine system
– plays essential roll in homeostatic regulation of all body systems
Hypothalamus
14-31
• functions of hypothalamic nuclei– hormone secretion– autonomic effects– thermoregulation– food and water intake – rhythm of sleep and waking– memory– emotional behavior
Hypothalamus
Cerebrum
• cerebrum – largest and most conspicuous part of the human brain– seat of sensory perception, memory, thought, judgment, and
voluntary motor actions
14-32
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leaves
Thalamus
Hypothalamus
Frontal lobe
Corpus callosum
Cingulate gyrus
Optic chiasm
Pituitary gland
Mammillary body
Midbrain
Pons
Central sulcus
Parietal lobe
Parieto–occipital sulcus
Occipital lobe
Pineal gland
Habenula
Posterior commissure
Cerebral aqueduct
Fourth ventricle
Cerebellum
(a)
EpithalamusAnteriorcommissure
Temporal lobe
Medullaoblongata
Figure 14.2a
14-33
Cerebrum - Gross Anatomy
• two cerebral hemispheres divided by longitudinal fissure– connected by white fibrous tract the corpus callosum
– gyri and sulci – increases amount of cortex in the cranial cavity
– gyri increases surface area for information processing capability
– some sulci divide each hemisphere into five lobes named for the cranial bones that overly them
Frontal lobe
Occipital lobe
Central sulcus
Longitudinal fissure
Parietal lobe
(a) Superior view
Cerebralhemispheres
Figure 14.1a,b
Brainstem
Cerebellum
Cerebrum
Spinal cord
Rostral Caudal
Central sulcus
Lateral sulcus
Gyri
(b) Lateral view
Temporal lobe
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14-34
• frontal lobe– voluntary motor functions – motivation, foresight, planning, memory, mood, emotion, social
judgment, and aggression
• parietal lobe– receives and integrates general sensory information, taste and some
visual processing
• occipital lobe– primary visual center of brain
• temporal lobe– areas for hearing, smell, learning, memory, and some aspects of
vision and emotion
• insula (hidden by other regions)– understanding spoken language, taste and sensory information from
visceral receptors
Functions of Cerebrum - Lobes
14-36
Limbic System• limbic system – center of emotion and learning
– hippocampus – in the medial temporal lobe - memory– amygdala – immediately rostral to the hippocampus - emotion
• circular patterns of feedback
14-37
Higher Brain Functions• higher brain functions - sleep, memory, cognition,
emotion, sensation, motor control, and language
• involve interactions between cerebral cortex and basal nuclei, brainstem and cerebellum
• functions of the brain do not have easily defined anatomical boundaries
• integrative functions of the brain focuses mainly on the cerebrum, but involves combined action of multiple brain levels
14-38
The Electroencephalogram
• electroencephalogram (EEG) – monitors surface electrical activity of the brain waves
– useful for studying normal brain functions as sleep and consciousness– in diagnosis of degenerative brain diseases, metabolic abnormalities, brain tumors, etc.
• brain waves – rhythmic voltage changes resulting from synchronized postsynaptic potentials at the superficial layer of the cerebral cortex
– 4 types distinguished by amplitude (mV) and frequency (Hz)• persistent absence of brain waves is common clinical and legal criterion of
brain death
Figure 14.18a
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© The McGraw-Hill Companies, Inc./Bob Coyle, photographer
1 second
Alpha ()
Beta ()
Delta ()
Theta ()
(a) (b)Figure 14.18b
14-39
Brain Waves
• alpha waves– awake and resting with eyes closed and mind wandering– suppressed when eyes open or performing a mental task
• beta waves– eyes open and performing mental tasks– accentuated during mental activity and sensory stimulation
• theta waves– drowsy or sleeping– if awake and under emotional stress
• delta waves– deep sleep
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Sensory Homunculus
14-41
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Fingers
Eye and eyelid
Tongue
Ankle
Lips
Face
JawPh
aryn
x
VocalizationSalivationMasticationSwallowing
NeckBrow
VHand
Wrist
Elb
ow
Sh
ou
lder
Tru
nk
Kne
e
Hip
Toes
IVIII
IIThumb (I)
I
II
IIIIV
V
(b)
Lateral Medial
Motor Homunculus
Figure 14.23b
Input and Output to
Cerebellum
14-43
Functional Regions of Cerebral Cortex
Wernicke area
Broca area
Primary motorcortex
Motor associationarea
Prefrontalcortex
Olfactoryassociationarea
Primary somestheticcortex
Somestheticassociation area
Primary gustatorycortex
Visual associationarea
Primaryvisual cortex
Primaryauditory cortex
Auditoryassociation area
Figure 14.21
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14-44
Language• language include several abilities: reading, writing,
speaking, and understanding words assigned to different regions of the cerebral cortex
• Wernicke area– permits recognition of spoken and written language and creates
plan of speech
– when we intend to speak, Wernicke area formulates phases according to learned rules of grammar
– transmits plan of speech to Broca area
• Broca area – generates motor program for the muscles of the larynx, tongue,
cheeks and lips
– transmits program to primary motor cortex for commands to the lower motor neurons that supply relevant muscles
14-45
Language CentersCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
leavesPrecentral gyrus
Anterior Posterior
Speech center ofprimary motor cortex
Primary auditorycortex(in lateral sulcus)
Postcentralgyrus
Angulargyrus
Primaryvisual cortex
Wernickearea
Brocaarea
Figure 14.25