Chapter 14: The Brain

The Brain: 4 Major Regions

Nervous System Development
 The Brain
• Embryological Development
– Determines organization of brain structures
– Neural tube
• Origin of brain
• Enlarges into three primary brain vesicles
– prosencephalon
– mesencephalon
– rhombencephalon
 The Brain
• Five Secondary Brain Vesicles
– Telencephalon

– Diencephalon
– Mesencephalon
– Metencephalon
– Myelencephalon
 The Brain
• Origins of Brain Structures
• Diencephalon and mesencephalon persist
– Telencephalon:
• Becomes cerebrum

– Metencephalon
• Forms cerebellum and pons

– Myelencephalon
• Becomes medulla oblongata
The Brain: 4 Major Regions
 The Brain
• The brain is a large, delicate mass of neural tissue
containing internal passageways and chambers filled
with cerebrospinal fluid
• Each of the six major brain regions has specific functions

• Ascending from the medulla oblongata to the cerebrum,

brain functions become more complex and variable
• Conscious thought and intelligence are produced in the
neural cortex of the cerebral hemispheres
 The Brain
• Ventricles of the Brain
– Origins of ventricles
• Neural tube encloses neurocoel
• Neurocoel expands to form chambers (ventricles) lined with
ependymal cells
– Each cerebral hemisphere contains one large lateral
ventricle
• Separated by a thin medial partition (septum pellucidum)
 The Cerebrum

Lateral ventricles Septum Pellucidum

Ventricles: fluid filled spaces
 The Brain
• Ventricles of the Brain
– Third ventricle
• Ventricle of the diencephalon

• Lateral ventricles communicate with third ventricle:

– via interventricular foramen (foramen of Munro)

John Cummings Munro 1858-1910

 The Brain
• Ventricles of the Brain
– Fourth ventricle
• Extends into medulla oblongata

• Becomes continuous with central canal of the

spinal cord
• Connects with third ventricle:
– via narrow canal in mesencephalon
– aqueduct of midbrain
 Brain Protection and Support
• Physical protection
– Bones of the cranium

– Cranial meninges
– Cerebrospinal fluid

• Biochemical isolation
– Blood–brain barrier
The Meninges:
Dura Mater
Arachnoid Mater
Pia Mater
 Brain Protection and Support
• The Cranial Meninges
– Have three layers:
• Dura mater
• Arachnoid mater
• Pia mater

– Are continuous with spinal meninges

– Protect the brain from cranial trauma
 Brain Protection and Support
• The Cranial Meninges
– Dura mater
• Inner fibrous layer (meningeal layer)
• Outer fibrous layer (endosteal layer) fused to periosteum
• Venous sinuses between two layers
– Arachnoid mater
• Covers brain
• Contacts epithelial layer of dura mater
• Subarachnoid space: between arachnoid mater and pia
mater
– Pia mater
• Attached to brain surface by astrocytes
 Brain Protection and Support
• Dural Folds
– Folded inner layer of dura mater
– Extend into cranial cavity
– Stabilize and support brain
– Contain collecting veins (dural sinuses)
– Falx cerebri, tentorium cerebelli, and falx cerebelli
 Brain Protection and Support
• Dural Folds
– Falx cerebri
• Projects between the cerebral hemispheres
• Contains superior sagittal sinus and inferior sagittal
sinus
– Tentorium cerebelli
• Separates cerebellum and cerebrum
• Contains transverse sinus
– Falx cerebelli
• Divides cerebellar hemispheres below the tentorium cerebelli
 Brain Protection and Support

Figure 14–3b The Relationship among the Brain, Cranium, and

Meninges.
 Brain Protection and Support
• Cerebrospinal Fluid (CSF)
– Surrounds all exposed surfaces of CNS
– Interchanges with interstitial fluid of brain
– Functions of CSF
• Cushions delicate neural structures
• Supports brain
• Transports nutrients, chemical messengers, and
waste products
 Brain Protection and Support
• Cerebrospinal Fluid (CSF)
– Choroid plexus
• Specialized ependymal cells and capillaries:
– secrete CSF into ventricles
– remove waste products from CSF
– adjust composition of CSF

• Produces about 500 mL of CSF/day

Cerebrospinal Fluid (CSF)
Cerebrospinal Fluid (CSF)
 Brain Protection and Support
• Cerebrospinal Fluid (CSF)
– CSF circulates
• From choroid plexus
• Through ventricles
• To central canal of spinal cord
• Into subarachnoid space around the brain, spinal cord, and
cauda equina
 Brain Protection and Support
• Cerebrospinal Fluid (CSF)
– CSF in subarachnoid space
• Arachnoid villi:
– extensions of subarachnoid space
– extend through dura mater to superior sagittal sinus

• Arachnoid granulations:
– large clusters of villi
– absorb CSF into venous circulation
Resorption through Dural Sinus
 Brain Protection and Support
• 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
 Brain Protection and Support
• Blood–Brain Barrier
– Isolates CNS neural tissue from general circulation
– Formed by network of tight junctions
– Between endothelial cells of CNS capillaries
– Lipid-soluble compounds (O2, CO2), steroids, and
prostaglandins diffuse into interstitial fluid of brain and
spinal cord
– Astrocytes control blood–brain barrier by releasing
chemicals that control permeability of endothelium
 Brain Protection and Support
• Blood–CSF Barrier
– Formed by special ependymal cells

– Surround capillaries of choroid plexus

– Limits movement of compounds transferred
– Allows chemical composition of blood and CSF to
differ
 Brain Protection and Support
• Meninges stabilize brain in cranial cavity
• Cerebrospinal fluid protects against sudden
movement
• CSF provides nutrients and removes wastes
• Blood–brain barrier and blood–CSF barrier
– Selectively isolate brain from chemicals in blood that
might disrupt neural function
 Disorders of the Brain
• Meningitis
Viral
Bacterial (worse)
Injuries:
Contusion: Bruise
Concussion: Loss of consciousness
Hemmorhage: Subdural or subarachnoid
Cerebral Edema: Inflammatory swelling
Hydrocephalus: CSF produced >removed
 Brain Disorders
• Cerebrovascular Disease
– Disorders interfere with blood circulation to brain

– Hemorrhagic (bleed)
– Ischemic (blockage)
– Stroke or cerebrovascular accident (CVA)
• Shuts off blood to portion of brain
• Neurons die
 Blood Supply to the Brain
Interrupted blood supply = CVA
Stress and Strokes
(Case Study)
Functional Anatomy of The Brain:
4 Major Regions Brain Stem
Brain Stem: Medulla, Pons, Mid-Brain
 The Medulla Oblongata
• The Medulla Oblongata
– Allows brain and spinal cord to communicate
– Coordinates complex autonomic reflexes
– Controls visceral functions (Respiratory, Cardiac
and Vasomotor)
– Nuclei in the Medulla
• Autonomic nuclei: control visceral activities
• Sensory and motor nuclei: of cranial nerves
• Relay stations: along sensory and motor pathways
 The Medulla Oblongata
• Autonomic Nuclei of the Medulla Oblongata
– Reticular formation
• Gray matter with embedded nuclei
• Regulates autonomic functions
– Reflex centers
• Control peripheral systems:
– cardiovascular centers:
» cardiac center
» control blood flow through peripheral tissues
– respiratory rhythmicity centers
sets pace for respiratory movements
 The Medulla Oblongata
• Sensory and Motor Nuclei of the Medulla
Oblongata
• Associated with 5 of 12 cranial nerves (VIII,
IX, X, XI, XII)
 The Medulla Oblongata

Figure 14–5a The Diencephalon and Brain Stem.

 The Medulla Oblongata

Figure 14–5b The Diencephalon and Brain Stem.

 The Medulla Oblongata

Figure 14–5c The Diencephalon and Brain Stem.

 The Medulla Oblongata

Figure 14–6b The Medulla Oblongata and Pons.

 The Pons
• The Pons
– Links cerebellum with mesencephalon,
diencephalon, cerebrum, and spinal cord
– Sensory and motor nuclei of cranial nerves V,
VI, VII, VIII
 The Pons
• The Pons
– Nuclei involved with respiration
• Apneustic center and pneumotaxic center:
– modify respiratory rhythmicity center activity
– Nuclei and tracts
• Process and relay information to and from
cerebellum
• Ascending, descending, and transverse tracts:
– transverse fibers (axons):
» link nuclei of pons with opposite cerebellar
hemisphere
Brain Stem:Pons
 The Mesencephalon
• Structures of the Mesencephalon
– Tectum
• Two pairs of sensory nuclei (corpora quadrigemina):
– superior colliculus (visual)
– inferior colliculus (auditory)

– Tegmentum
• Red nucleus (many blood vessels)
• Substantia nigra (pigmented gray matter)
 The Mesencephalon

Figure 14–8b The Mesencephalon.

 The Mesencephalon

Figure 14–8a The Mesencephalon.

 The Mesencephalon
• Structures of the Mesencephalon
– Cerebral peduncles
• Nerve fiber bundles on ventrolateral surfaces

• Contain:
– descending fibers to cerebellum
– motor command fibers
Cerebellum: Learned Activities
 The Cerebellum
• Functions of the Cerebellum
– Adjusts postural muscles
– Fine-tunes conscious and subconscious
movements to produce smooth movements with
input from cerebral commands and input from
proprioceptors for balance
The Cerebellum: 2 Views
 The Cerebellum
• Structures of the Cerebellum
– Folia
• Surface of cerebellum
• Highly folded neural cortex
– Anterior and posterior lobes
• Separated by primary fissure
– Cerebellar hemispheres:
• Separated at midline by vermis
– Vermis
• Narrow band of cortex
– Flocculonodular lobe
• Below fourth ventricle
 The Cerebellum
• Structures of the Cerebellum
– Purkinje cells
• Large, branched cells
• Found in cerebellar cortex
• Receive input from up to 200,000 synapses
– Arbor vitae
• Highly branched, internal white matter of cerebellum
• Cerebellar nuclei: embedded in arbor vitae:
– relay information to Purkinje cells
 The Cerebellum
• Structures of the Cerebellum
– The peduncles
• Tracts link cerebellum with brain stem, cerebrum, and spinal
cord:
– superior cerebellar peduncles

– middle cerebellar peduncles

– inferior cerebellar peduncles

 The Cerebellum
• Disorders of the Cerebellum
– Ataxia
• Damage from trauma or stroke

• Intoxication (temporary impairment)

• Disturbs muscle coordination
Functional Anatomy of The Brain:
Diencephalon
 The Diencephalon
• Integrates sensory information and motor
commands
• Thalamus, epithalamus, and hypothalamus
– The pineal gland
• Found in posterior epithalamus
• Secretes hormone melatonin
Diencephalon: Thalamus and Hypothalamus
Thalamus:
-Connects Brain
Stem to Cerebrum
-Screens, Edits and
Integrates all Sensory
Input

Hypothalamus
-Connects CNS to
ANS and Endocrine
-Coordinates
“Visceral” Response
Limbic System
 The Diencephalon

Figure 14–9 The Thalamus.

 The Diencephalon
• The Thalamus
– Filters ascending sensory information for primary
sensory cortex
– Relays information between basal nuclei and cerebral
cortex
– The third ventricle
• Separates left thalamus and right thalamus
• Interthalamic adhesion (or intermediate mass):
– projection of gray matter
– extends into ventricle from each side
 Thalamus

Executive Secretary to
the Cerebrum

Major Relay Center

edits, integrates and

screens incoming
sensory input
The Diencephalon

[INSERT Table. 14.5]

 The Diencephalon
• Eight Functions of the Hypothalamus
– Provides subconscious control of skeletal muscle

Facial expressions with rage, sexual activity motions

– Controls autonomic function
– Coordinates activities of nervous and endocrine systems
– Secretes hormones
• Antidiuretic hormone (ADH) by supraoptic nucleus
• Oxytocin (OT; OXT) by paraventricular nucleus
 The Diencephalon
• Eight Functions of the Hypothalamus
– Produces emotions and behavioral drives
• The feeding center (hunger)
• The thirst center (thirst)

– Coordinates voluntary and autonomic functions as in

dangerous, stressful or emergency situations
– Regulates body temperature
• Preoptic area of hypothalamus

– Controls circadian rhythms (day–night cycles)

• Suprachiasmatic nucleus
 The Diencephalon
• The Hypothalamus
– Mamillary bodies
• Process olfactory and other sensory information
• Control reflex eating movements
– Infundibulum
• A narrow stalk
• Connects hypothalamus to pituitary gland
– Tuberal area
• Located between the infundibulum and mamillary bodies
• Helps control pituitary gland function
Hypothalamus: Multiple Functions
 Diencephalon:
Epithalamus, Thalamus, Hypothalamus
The Diencephalon
The Cerebrum
 The Cerebrum
• The Cerebrum
– Is the largest part of the brain
– Controls all conscious thoughts and
intellectual functions
– Processes somatic sensory and motor
information
 The Cerebrum
• Gray matter
– In cerebral cortex and basal nuclei

• White matter
– Deep to basal cortex

– Around basal nuclei

 The Cerebrum
• Structures of the Cerebrum
– Gyri of neural cortex
• Increase surface area (number of cortical neurons)
– Insula (island) of cortex
• Lies medial to lateral sulcus
– Longitudinal fissure
• Separates cerebral hemispheres
– Lobes
• Divisions of hemispheres
 The Cerebrum
• Structures of the Cerebrum
– Central sulcus divides
• Anterior frontal lobe from posterior parietal lobe

– Lateral sulcus divides

• Frontal lobe from temporal lobe

– Parieto-occipital sulcus divides

• Parietal lobe from occipital lobe
4 Lobes, plus 1
 Cortex = Gray Matter covering
White Matter is deep to that
Corpus Callosum Connects Hemispheres
 The Cerebrum
• White Matter of the Cerebrum
– Association fibers
– Commissural fibers

– Projection fibers
White Matter: making connections
 The Cerebrum
• White Matter of the Cerebrum
– Association fibers
• Connections within one hemisphere:
– arcuate fibers:
» are short fibers
» connect one gyrus to another
– longitudinal fasciculi:
» are longer bundles
» connect frontal lobe to other lobes in same hemisphere
 The Cerebrum
• White Matter of the Cerebrum
– Commissural fibers
• Bands of fibers connecting two hemispheres:
– corpus callosum
– anterior commissure
 The Cerebrum
• White Matter of the Cerebrum
– Projection fibers
• Pass through diencephalon
• Link cerebral cortex with:
– diencephalon, brain stem, cerebellum, and spinal cord
• Internal capsule:
– all ascending and descending projection fibers
 The Cerebrum
• The Basal Nuclei
– Also called cerebral nuclei
– Are masses of gray matter

– Are embedded in white matter of cerebrum

– Direct subconscious activities
Basal Nucleii
 The Cerebrum
• Structures of Basal Nuclei
– Caudate nucleus
• Curving, slender tail

– Lentiform nucleus
• Globus pallidus
• Putamen
 The Cerebrum
• Functions of Basal Nuclei
– Involved with
• The subconscious control of skeletal muscle tone

• The coordination of learned movement patterns

(walking, lifting)
Primary motor and sensory areas
 The Cerebrum
• Motor and Sensory Areas of the Cortex
– Central sulcus separates motor and sensory
areas
– Motor areas
• Precentral gyrus of frontal lobe:
– directs voluntary movements
• Primary motor cortex:
– is the surface of precentral gyrus
• Pyramidal cells:
– are neurons of primary motor cortex
Cerebral cortex
 The Cerebrum
• Association Areas
– Sensory association areas
• Monitor and interpret arriving information at sensory areas of
cortex

– Somatic motor association area (premotor cortex)

• Coordinates motor responses (learned movements)
 The Cerebrum
• Motor and Sensory Areas of the Cortex
– Sensory areas
• Postcentral gyrus of parietal lobe:
– receives somatic sensory information (touch, pressure,
pain, vibration, taste, and temperature)

• Primary sensory cortex:

– surface of postcentral gyrus
 The Cerebrum
• Special Sensory Cortexes
– Visual cortex
• Information from sight receptors
– Auditory cortex
• Information from sound receptors
– Olfactory cortex
• Information from odor receptors
– Gustatory cortex
• Information from taste receptors
 The Cerebrum
• Association Areas
– Sensory association areas
• Monitor and interpret arriving information at sensory areas of
cortex

– Somatic motor association area (premotor cortex)

• Coordinates motor responses (learned movements)
 The Cerebrum
• Sensory Association Areas
– Somatic sensory association area
• Interprets input to primary sensory cortex (e.g., recognizes
and responds to touch)
– Visual association area
• Interprets activity in visual cortex

– Auditory association area

• Monitors auditory cortex
Association Areas
 The Cerebrum
• Integrative Centers
– Are located in lobes and cortical areas of both
cerebral hemispheres
– Receive information from association areas
– Direct complex motor or analytical activities
 The Cerebrum
• General Interpretive Area
– Also called Wernicke area
– Present in only one hemisphere
– Receives information from all sensory association
areas
– Coordinates access to complex visual and auditory
memories
 The Cerebrum
• Other Integrative Areas
– Speech center
• Is associated with general interpretive area
• Coordinates all vocalization functions
– Prefrontal cortex of frontal lobe
• Integrates information from sensory association
areas
• Performs abstract intellectual activities (e.g.,
predicting consequences of actions)
Integrative Areas
 The Cerebrum
• Interpretive Areas of Cortex
– Brodmann areas
• Patterns of cellular organization in cerebral cortex
 Brodman’s Areas: Rough mapping,
Only randomly connected to actual functions
 The Cerebrum
• Hemispheric Lateralization
– Functional differences between left and right
hemispheres
– Each cerebral hemisphere performs certain
functions that are not ordinarily performed by
the opposite hemisphere
 The Cerebrum
• The Left Hemisphere
– In most people, left brain (dominant hemisphere)
controls
• Reading, writing, and math
• Decision making
• Speech and language

• The Right Hemisphere

– Right cerebral hemisphere relates to
• Senses (touch, smell, sight, taste, feel)
• Recognition (faces, voice inflections)
The Cerebral Hemispheres: Different
Functions
 The Limbic System
• The Limbic System
– Is a functional grouping that
• Establishes emotional states
• Links conscious functions of cerebral cortex with autonomic
functions of brain stem
• Facilitates memory storage and retrieval
 The Limbic System
• Components of the Limbic System
– Amygdaloid body
• Acts as interface between the limbic system, the
cerebrum, and various sensory systems
– Limbic lobe of cerebral hemisphere
• Cingulate gyrus
• Dentate gyrus
• Parahippocampal gyrus
• Hippocampus
 The Limbic System
• Components of the Limbic System
– Fornix
• Tract of white matter
• Connects hippocampus with hypothalamus
– Anterior nucleus of the thalamus
• Relays information from mamillary body to cingulate gyrus
– Reticular formation
• Stimulation or inhibition from hypothalamic nucleii
responsible for emotions (rage, fear, pain, sexual arousal,
pleasure) to cause effects from lethargy to heightened
alertness
 The Limbic System

Figure 14–11b The Limbic System.

Reticular Activating System
 Higher-Order Functions
• States of Consciousness
– Arousal and the reticular activating system (RAS)
• Awakening from sleep
• Function of reticular formation:
– extensive interconnections with sensory, motor, integrative nuclei,
and pathways along brain stem

• Determined by complex interactions between reticular formation

and cerebral cortex
 Higher-Order Functions
• Reticular Activating System (RAS)
– Important brain stem component
– Diffuse network in reticular formation
– Extends from medulla oblongata to mesencephalon
– Output of RAS projects to thalamic nuclei that
influence large areas of cerebral cortex
– When RAS inactive, so is cerebral cortex
– Stimulation of RAS produces widespread activation of
cerebral cortex
Degenerative Brain Disorders
Alzheimer’s Disease
Alzheimer’s Brains
 Degeneration of Basal Nuclei:
Parkinson’s Disease (Environmental)
Huntington’s Disease (Genetic)

Loss of coordination of movement: Shakes & Tremors

 Brain Chemistry
• Huntington Disease
– Destruction of ACh-secreting and GABA-secreting
neurons in basal nuclei
– Symptoms appear as basal nuclei and frontal lobes
slowly degenerate
– Difficulty controlling movements
– Intellectual abilities gradually decline
 Cranial Nerves
• 12 pairs connected to brain
• Four Classifications of Cranial Nerves
– Sensory nerves: carry somatic sensory information,
including touch, pressure, vibration, temperature, and
pain
– Special sensory nerves: carry sensations such as
smell, sight, hearing, balance
– Motor nerves: axons of somatic motor neurons
– Mixed nerves: mixture of motor and sensory fibers
XII Cranial Nerves: Number, Name, Function
 Cranial Nerves

Figure 14–19 The Olfactory Nerve.

 Cranial Nerves

Figure 14–20 The Optic Nerve.

 Cranial Nerves

Figure 14–21 Cranial Nerves Controlling the Extra-Ocular Muscles.

 Cranial Nerves

Figure 14–22 The Trigeminal Nerve.

 Cranial Nerves

Figure 14–23a The Facial Nerve.

 Cranial Nerves

Figure 14–24 The Vestibulocochlear Nerve.

 Cranial Nerves

Figure 14–25 The Glossopharyngeal Nerve.

 Cranial Nerves

Figure 14–26 The Vagus Nerve.

 Cranial Nerves

Figure 14–26 The Vagus Nerve.

 Cranial Nerves

Figure 14–27 The Accessory and Hypoglossal Nerves.

Cranial Nerves
Cranial Nerves
Cranial Reflexes
Quiz Time