chapter 14 brain

8/7/2019 Chapter 14 Brain

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Chapter 14: The Brain


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The Brain: 4 Major Regions


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Nervous System Development


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The Brain

Embryological Development

Determines organization of brain structures

Neural tube Origin of brain

Enlarges into three primary brain vesicles

prosencephalon

mesencephalon

rhombencephalon


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The Brain

Five Secondary Brain Vesicles

Telencephalon

Diencephalon

Mesencephalon

Metencephalon

Myelencephalon


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The Brain

Origins of Brain Structures

Diencephalon and mesencephalon persist

Telencephalon: Becomes cerebrum

Metencephalon

Forms cerebellum and pons

Myelencephalon

Becomes medulla oblongata


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The Brain: 4 Major Regions


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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


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The Brain Ventricles of the Brain

Origins of ventricles

Neural tube encloses neurocoel

Neurocoel expands to form chambers (ventricles) lined withependymal cells

Each cerebral hemisphere contains one large lateral

ventricle

Separated by a thin medial partition (septum pellucidum)


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The Cerebrum

Lateral ventricles Septum Pellucidum


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Ventricles: fluid filled spaces


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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


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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


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Brain Protection and Support

Physical protection

Bones of the cranium

Cranial meninges

Cerebrospinal fluid

Biochemical isolation

Bloodbrain barrier


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The Meninges:Dura Mater

Arachnoid Mater

Pia Mater


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The Cranial Meninges

Have three layers:

Dura mater

Arachnoid mater

Pia mater

Are continuous with spinal meninges

Protect the brain from cranial trauma


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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


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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


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Dural Folds

Falx cerebri

Projects between the cerebral hemispheres

Contains superior sagittal sinus and inferior sagittalsinus

Tentorium cerebelli

Separates cerebellum and cerebrum

Contains transverse sinus

Falx cerebelli

Divides cerebellar hemispheres below the tentorium cerebelli


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Figure 143b The Relationship among the Brain, Cranium, andMeninges.


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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


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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


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CSF circulates

From choroid plexus

Through ventricles

To central canal of spinal cord

Into subarachnoid space around the brain, spinal cord, and

cauda equina


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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


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Resorption through Dural Sinus


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Blood Supply to the Brain

Supplies nutrients and oxygen to brain

Delivered by internal carotid arteries and

vertebral arteries

Removed from dural sinuses byinternal

jugular veins


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BloodBrain 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 bloodbrain barrier by releasing

chemicals that control permeability of endothelium


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BloodCSF 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


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Meninges stabilize brain in cranial cavity

Cerebrospinal fluid protects against sudden

movement CSF provides nutrients and removes wastes

Bloodbrain barrier and bloodCSF barrier

Selectively isolate brain from chemicals in blood that

might disrupt neural function


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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


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Brain Disorders

Cerebrovascular Disease

Disorders interfere with blood circulation to brain

Hemorrhagic (bleed)

Ischemic (blockage)

Stroke orcerebrovascular accident (CVA)

Shuts off blood to portion of brain

Neurons die


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Blood Supply to the BrainInterrupted blood supply = CVA


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Stress and Strokes(Case Study)


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Functional Anatomy of The Brain:4 Major Regions Brain Stem


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Brain Stem: Medulla, Pons, Mid-Brain


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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


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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


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Sensory and MotorNuclei of the Medulla

Oblongata

Associated with 5 of 12 cranial nerves (VIII,

IX, X, XI, XII)


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Figure 145a The Diencephalon and Brain Stem.


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Figure 145b The Diencephalon and Brain Stem.


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Figure 145c The Diencephalon and Brain Stem.


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Figure 146b The Medulla Oblongata and Pons.


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The Pons

The Pons

Links cerebellum with mesencephalon,

diencephalon, cerebrum, and spinal cord

Sensory and motor nuclei of cranial nerves V,

VI, VII, VIII


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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


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Brain Stem:Pons


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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)


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The Mesencephalon

Figure 148b The Mesencephalon.


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The Mesencephalon

Figure 148a The Mesencephalon.


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The Mesencephalon

Structures of the Mesencephalon

Cerebral peduncles

Nerve fiber bundles on ventrolateral surfaces

Contain:

descending fibers to cerebellum

motor command fibers


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Cerebellum: Learned Activities


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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


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The Cerebellum: 2 Views


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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


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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


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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


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The Cerebellum

Disorders of the Cerebellum

Ataxia

Damage from trauma or stroke

Intoxication (temporary impairment)

Disturbs muscle coordination


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F ti l A t f Th B i


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Functional Anatomy of The Brain:Diencephalon


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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


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Diencephalon: Thalamus and

Hypothalamus

Thalamus:-Connects BrainStem to Cerebrum

-Screens, Edits andIntegrates all Sensory

Input

Hypothalamus-Connects CNS toANS and Endocrine

-CoordinatesVisceral Response

Limbic System


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The Diencephalon

Figure 149 The Thalamus.


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The Diencephalon

The Thalamus

Filters ascending sensory information for primary

sensory cortex

Relays information between basal nuclei and cerebralcortex

The third ventricle

Separates left thalamus and right thalamus

Interthalamic adhesion (or intermediate mass):

projection of gray matter

extends into ventricle from each side


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Thalamus

Executive Secretary to

the Cerebrum

Major Relay Center

edits, integrates and

screens incoming

sensory input


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The Diencephalon

[INSERT Table. 14.5]


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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


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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 (daynight cycles)

Suprachiasmatic nucleus


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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


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Hypothalamus: Multiple Functions


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Diencephalon:Epithalamus, Thalamus, Hypothalamus

The Diencephalon


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The Diencephalon


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The Cerebrum


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The Cerebrum

The Cerebrum

Is the largest part of the brain

Controls all conscious thoughts and

intellectual functions

Processes somatic sensory and motor

information


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The Cerebrum

Gray matter

In cerebral cortex and basal nuclei

White matter

Deep to basal cortex

Around basal nuclei


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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


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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


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4 Lobes, plus 1


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Cortex = Gray Matter covering


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Cortex = Gray Matter covering

White Matter is deep to that

Corpus Callosum Connects Hemispheres


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The Cerebrum

White Matter of the Cerebrum

Association fibers

Commissural fibers

Projection fibers


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White Matter: making connections


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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


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The Cerebrum


Commissural fibers

Bands of fibers connecting two hemispheres:

corpus callosum

anterior commissure


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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


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The Cerebrum

The Basal Nuclei

Also called cerebral nuclei

Are masses of gray matter

Are embedded in white matter of cerebrum

Direct subconscious activities


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Basal Nucleii


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The Cerebrum

Structures of Basal Nuclei

Caudate nucleus

Curving, slender tail

Lentiform nucleus

Globus pallidus

Putamen

C


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The Cerebrum

Functions of Basal Nuclei

Involved with

The subconscious control of skeletal muscle tone

The coordination of learned movement patterns

(walking, lifting)


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Th C b


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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


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Th C b


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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)

Th C b


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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

Th C b


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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

Th C b


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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)

Th C b


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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

A i ti A


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Association Areas

Th C b


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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

Th C b


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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 Cerebr m


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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)

I t ti A


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Integrative Areas

The Cerebrum


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The Cerebrum

Interpretive Areas of Cortex

Brodmann areas

Patterns of cellular organization in cerebral cortex

Brodmans Areas: Rough mapping


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Brodman s Areas: Rough mapping,Only randomly connected to actual functions


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The Cerebrum


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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

F ti


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Functions

The Limbic System


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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


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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


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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


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The Limbic System

Figure 1411b The Limbic System.


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Reticular Activating System


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Reticular Activating System

Higher Order Functions


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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



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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


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Degenerative Brain Disorders

Alzheimers Disease


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Alzheimer s Disease

Alzheimers Brains


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Degeneration of Basal Nuclei:

Parkinsons Disease (Environmental)


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Parkinson s Disease (Environmental)

Huntingtons Disease (Genetic)

Loss of coordination of movement: Shakes & Tremors

Brain Chemistry


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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


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Cranial Nerves

12 pairs connected to brain Four Classifications of Cranial Nerves

Sensory nerves: carry somatic sensory information,

including touch, pressure, vibration, temperature, andpain

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


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Cranial Nerves


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Cranial Nerves

Figure 1419 The Olfactory Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1420 The Optic Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1421 Cranial Nerves Controlling the Extra-Ocular Muscles.

Cranial Nerves


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Cranial Nerves

Figure 1422 The Trigeminal Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1423a The Facial Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1424 The VestibulocochlearNerve.

Cranial Nerves


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Cranial Nerves

Figure 1425 The Glossopharyngeal Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1426 The Vagus Nerve.

Cranial Nerves


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Cranial Nerves

Figure 1426 The Vagus Nerve.

Cranial Nerves


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C a a e es

Figure 1427 The Accessory and Hypoglossal Nerves.

Cranial Nerves


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Cranial Nerves


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Cranial Reflexes


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Quiz Time


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chapter 14 brain

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