presentation1 - linn–benton community...

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The Brain

The Nervous System

Introduction

� Integration

�Memory

�Learning

�Sensation and perception

Organization of Neural Tissue

• White matter versus gray matter

� Gray matter: short,

non-myelinated neurons

and neuron cell bodies

� White matter: myelinated

and non-myelinated axons

Gray

matter

White

matter


• Fiber bundles

– Nerve fibers = axon + myelin

– Bundles of nerve fibers

�CNS = tracts

�PNS = nerves

CNS tracts

PNS nerves


• Nerve cell bodies

– Collections of nerve cell bodies

�CNS = nucleus

� Largely in gray matter

�PNS = ganglion

�Exception: basal ganglia in the brain


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– Generally

• Central cavity surrounded by a gray matter core

– External white matter

• Composed of myelinated fiber tracts

– Brain has additional areas of gray matter

• Not present in spinal cord

Figure 12.4

Cerebrum

Cerebellum

Migratory

pattern of

neurons

Cortex of

gray matter

Inner gray

matter

Gray matter

Outer white

matter

Central cavity

Central cavity

Inner gray matter

Gray matter

Outer white matter

Central cavity

Inner gray matter

Outer white matter

Region of cerebellum

Brain stem

Spinal cord


Similar pattern with additional areas of gray matter

The Brain

• Functions

– Conscious perception

– Internal regulation

• Average adult male 3.5 lbs

• Average adult female 3.2 lbs

Same brain mass

to body mass ratio!

The Brain

• 4 Adult brain regions

1. Cerebral hemispheres (cerebrum)

2. Diencephalon

3. Cerebellum

4. Brain stem (midbrain, pons, and medulla)

The Brain

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The Brain

• Four major regions are connected by ventricles and aqueducts

The Brain

• Ventricles

– Filled with cerebrospinal fluid

– Lined by ependymal cells

– Continuous with one another, the subarachnoid

space, and the central canal of the spinal cord

The Cerebrum

• Cerebral hemispheres form superior part of

brain

• About 80% of brain mass

• 3 tissue layers

– Superficial cortex = gray matter

– Internal white matter

– Basal nuclei = islands of gray matter

Figure 12.6c

Parietal

lobe

Frontal lobe

Right cerebral

hemisphere

Occipital

lobe

Left cerebral

hemisphere

Cerebral veins

and arteries

covered by

arachnoid

mater

Longitudinal

fissure

Posterior(c)

Anterior

The Cerebrum

• Cerebral cortex

– Surface layer of cerebrum

– Gray matter

– “Executive Suite” – where the conscious mind is found

– Self-awareness, communication, memory,

understanding, voluntary movements

The Cerebrum

• Cerebral cortex

– Convolutions

• Gyri – elevated ridges

• Sulci – shallow grooves

• Fissures – deep grooves,

separate larger regions

of the brain

– May look random, but are

actually fairly consistent

between people

• Important landmarksFISSURES

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The Cerebrum

• Fissures divide cerebral hemispheres into 4 lobes

The Cerebrum

• 3 types of functional areas in the cerebral cortex

1. Motor areas*

• Control voluntary movement

2. Sensory areas*

• Conscious awareness of sensation

3. Association areas

• Integrate diverse information

* Do not confuse these areas with motor and sensory neurons. All neurons in

the cerebral cortex are interneurons

The Cerebrum

• Functional areas of the cerebral cortex

– Contralateral orientation

• Each hemisphere is primarily concerned with functions on

the opposite side of the body

– Hemispheres are functionally specialized

• Language on left, attention on the right

– Conscious behavior involves the entire cortex

• We are grossly oversimplifying

Figure 12.8a

Gustatory cortex

(in insula)

Primary motor cortex

Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area

(outlined by dashes)

Solving complex,

multitask problems

(a) Lateral view, left cerebral hemisphere

Motor areas

Prefrontal cortex

Sensory areas and related

association areasCentral sulcus

Primary somatosensory

cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing

Primary motor cortex Motor association cortex Primary sensory cortex

Sensory association cortex Multimodal association cortex

Cerebral Motor Activity


• Primary motor cortex

– Large pyramidal cells of the precentral gyrus

– Long axons → pyramidal (corticospinal) tracts

• Project all the way to the spinal cord

• All other descending motor tracts are chains of neurons

– Allows conscious control

• Precise, skilled, voluntary movements

Figure 12.9

Toes

Swallowing

Tongue

Jaw

Primary motor

cortex

(precentral gyrus)

Motor

Motor map inprecentral gyrus

Posterior

Anterior

Motor Homunculus

Somatotopy of precentral

gyrus (primary motor cortex)

Motor homunculi:

upside-down caricatures

representing the motor

innervation of body regions

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• Primary motor cortex

– Most of the neurons here control muscles with the most precise motor control – the face, tongue, and hands

– Individual neurons must work together to coordinate movement

– Neurons that control related movements intermingle

• Example: reaching the arm forward involves muscles in the shoulder and elbow

– Neurons controlling unrelated movements do not cooperate

• Example: hand and foot


• Premotor cortex

– Anterior to the precentral gyrus

– Controls learned, repetitious or patterned motor

skills

• “Muscle memory”


• Premotor cortex

– Coordinates simultaneous or sequential actions

• Examples: playing an instrument, typing

– Involved in the planning of movements that depend

on sensory feedback

• Example: Feeling for a light switch in the dark


• Broca’s area

– Anterior to the inferior region of the premotor area

– Present in one hemisphere (usually the left)

– Motor speech area that directs muscles of the

tongue

• Active as one prepares to speak, and as one plans other

voluntary motor activities


• Frontal eye field

– Anterior to the premotor cortex and superior to

Broca’s area

– Controls voluntary eye movements

Figure 12.8a

Gustatory cortex

(in insula)


Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area


Solving complex,

multitask problems


Motor areas

Prefrontal cortex




cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing




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Cerebral Vascular Accident (Stroke)

• Types

– Ischemic stroke

– Hemorrhagic stroke

• Result

– Tissue death called an infarct

– Effects are determined by

• Where it occurs

• How large the area involved

Stroke

Stroke Cerebral Vascular Accident (Stroke)

• Damage to the primary motor cortex

– Paralyzes muscles controlled by those areas

– Only voluntary control is lost – muscles still

contract reflexively

• Damage to the premotor cortex

– Loss of motor skills, but not of muscle strength or

movement

– Reprogramming the skill to another set of

premotor neurons is possible

Figure 12.8a

Gustatory cortex

(in insula)


Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area


Solving complex,

multitask problems


Motor areas

Prefrontal cortex

Sensory areas & related



cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing



Cerebral Sensory ActivityCerebral Sensory Activity

• Widely dispersed

– Parietal, temporal & occipital lobes

• Concerned with conscious awareness of

sensation

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Cerebral Sensory Activity

• Primary somatosensory cortex

– In the postcentral gyri, parietal lobe

– Stimuli from skin, skeletal muscles, and joints

– Capable of spatial discrimination

• Identification of body region being stimulated

• Ability to perceive separate points of contact on the same

body part

Figure 12.9

Genitals

Intra-

abdominal

Primary somato-

sensory cortex

(postcentral gyrus)

Sensory

Sensory map inpostcentral gyrus

Posterior

Anterior


• Primary somatosensory cortex

– The amount of sensory cortex devoted to a body

region depends on that region’s sensitivity, not its

size

– Most sensitive regions in humans: face (especially

lips) and fingertips


• Somatosensory association cortex

– Posterior to the primary somatosensory cortex

– Integrates sensory input from primary

somatosensory cortex

– Integrates and analyzes inputs

• Temperature, size, texture

• Recalls past sensory experiences with objects being felt

• Relationship of parts of objects being felt

– Example: reaching into pocket and discerning keys from coins

without looking


• Visual areas– Primary visual cortex

• Occipital lobe

• Receives visual information from the retinas

– Visual association area• Surrounds the primary visual cortex

• Uses past visual experiences to interpret visual stimuli – Example: color, form and movement

• Complex processing involves entire posterior half of the hemispheres

• (Brain Games)

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• Auditory areas

– Primary auditory cortex

• Temporal lobes

• Interprets information from inner ear

– Pitch, loudness and location

– Auditory association area

• Posterior to the primary auditory cortex

• Stores memories of sounds and permits perception of sounds

– Allows us to differentiate between a scream, a song, thunder, speech, etc.

Figure 12.8a

Gustatory cortex

(in insula)


Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area


Solving complex,

multitask problems


Motor areas

Prefrontal cortex




cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing




Association Areas

• Receive inputs from multiple sensory areas

• Send outputs to multiple areas

– Including the premotor cortex

• Function

– Allows us to give meaning to information received,

store it as memory, compare it to previous

experience, and decide on action to take

– Damage to association areas leads to functional

deficits

Association Areas

• Multimodal association areas (most of the

cortex)

– Seems to be where sensations, thoughts, and

emotions become conscious

– Where complex sensory input coordinates with

memory and the primary motor cortex to drive

action

Association Areas

• Example: You’re watching a volleyball match, and the ball is flying at

your face

Primary visual cortex:

Ball is getting bigger, shadow is moving

across the floor.

Primary auditory cortex:

Someone yells, “Look out!”

Visual association area:

That means the ball is moving closer to me.

Auditory association area:

That means danger.

Premotor cortex:

I should duck and put my hands in front of

my face.

Primary motor cortex:

Neck, shoulders, elbows, and arms, MOVE!!

Multimodal association area:

If I don’t move, I am going to get hit. I

should move!

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Association Activity

• Three areas

– Prefrontal cortex

– Posterior association area (not discussed here)

– Limbic association area

Figure 12.8a

Gustatory cortex

(in insula)


Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area


Solving complex,

multitask problems


Motor areas

Prefrontal cortex




cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing



Cerebral Association Activity


• Prefrontal cortex

– Most complicated cortical region

– Involved with intellect, cognition, recall and personality

– Contains working memory (needed for abstract ideas),

judgment, reasoning and conscience

– Development depends on feedback from social

environment and develops slowly


• Limbic association area

– Part of the limbic system

– Provides emotional impact that helps establish

memories

– Connections with prefrontal cortex regulate emotional

expression


• Prefrontal Labotomy

– Popular treatment for “delusions, obsessions, nervous tensions, and the like” in the 1940s and 50s

– Involves cutting or scraping away most of the connections to and from the prefrontal cortex

– Some patients died on the table or later committed suicide

– Some were severely brain damaged or developed seizures

– Some patients saw improvement of symptoms, but not without impairments to personality, intellect, and empathy

– “Surgically induced childhood”


• Walter Freeman and James Watt

– 1945 – developed the transorbital method of

lobotomy

– Required no surgery or anesthesia

– Initially pushed an ice pick (later a leukotome)

through the back of the eye socket

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Figure 12.8a

Gustatory cortex

(in insula)


Premotor cortex

Frontal eye field

Working memory

for spatial tasks

Executive area for

task management

Working memory for

object-recall tasks

Broca’s area


Solving complex,

multitask problems


Motor areas

Prefrontal cortex




cortexSomatosensory

association cortex

Somatic

sensation

Taste

Wernicke’s area


Primary visual

cortexVisual

association

area

Vision

Auditory

association area

Primary

auditory cortex

Hearing



Cerebral Association Activity Cerebral Lateralization

� Left hemisphere

�Math

�Logic

�Language

�Controls right side of body

• Right hemisphere

– Visual-spatial skills

– Intuition

– Emotion

– Art and music

– Controls left side of body

Cerebral White Matter

• Responsible for communication between areas

of the brain and the spinal cord

• Consists largely of myelinated fibers bundled

into large tracts

• Tracts are classified by the direction in which

they run

Cerebral White Matter

• Projection tracts– Connect cerebrum w/other body locations

– Run vertically

• Association tracts– Connect different parts of the same heisphere

– Adjacent gyri or different cortical lobes

• Commissural tracts– Connect corresponding gray matter areas in the two

hemispheres

– Allows the brain to function as a whole

– Largest: corpus callosum (severed in some medical experiments)

White Matter Tracts Cerebral Gray Matter

• Basal Nuclei

– Association of gray matter deep in cerebral

hemispheres

– Exact components controversial

– Contribute to muscle coordination and control by

excitatory innervation

• Examples: Determine intensity of movements, disorders

include Parkinson’s and Huntington’s

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Basal Nuclei Cerebral Gray Matter

• Special notes…

• Your text refers to the putamen and the globus

pallidus – together, these structures make up

the lentiform nucleus

• Your study guide refers to the amygdaloid

nucleus, which requires a different plane of

section…

Copyright 2009 John Wiley & Sons, Inc.

Review

• White versus grey matter

• Ventricles

• 4 brain regions

• 4 lobes of cerebral hemispheres

• 3 layers of cerebrum

– Cortex

• Motor

• Sensory

• Association

– White matter tracts

– Gray matter

Brain Regions

� 4 Adult brain regions


2. Diencephalon

3. Cerebellum


Diencephalon

• Three paired structures

– Thalamus

– Hypothalamus

– Epithalamus

• Encloses the third ventricle

• Surrounded by cerebral

hemispheres

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Figure 12.12

Corpus callosum

Choroid plexus

Thalamus

(encloses third

ventricle)

Pineal glandPosterior commissure

Corpora

quadrigeminaCerebralaqueduct

Arbor vitae (ofcerebellum)

Fourth ventricle

Choroid plexus

Cerebellum

Septum pellucidum

Interthalamic

adhesion

(intermediate

mass of

thalamus)

Interven-

tricular

foramen

Anterior

commissure

Hypothalamus

Optic chiasma

Pituitary gland

Cerebral hemisphere

Mammillary bodyPons

Medulla oblongata

Spinal cord

Mid-

brain

Fornix

Epithalamus

Diencephalon

• Thalamus

– Several nuclei

– Gateway of the cerebral cortex

– Major relay station for most

sensory impulses

– Information is sorted, edited,

bundled, and sent to the

correct place

Diencephalon

• Thalamus

– Relay center for cerebral activation

– Associated with reticular formation

• Neural pathways in the brain stem mediating consciousness

– Relay center for somatosensory information

• Except olfaction

– Coma is associated with thalamic injury

• Vegetative state = damage to cortical pathways

Refer to diagram on CNS 8

Diencephalon

• Hypothalamus

– Inferior to the thalamus

– Forms portions of walls of the third ventricle

– Caps the brain stem

– Consists of a number of nuclei

Diencephalon

• Hypothalamus

– Infundibulum

• Connects pituitary to hypothalamus

– Mammillary bodies

• Relay stations for olfactory pathways

– Responsible for most neurogenic homeostasis of

the body

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Diencephalon

• Hypothalamic function

– Autonomic control center for many visceral functions

• Examples

– Blood pressure, rate and force of heartbeat

– Regulates body temperature

– Hunger and G.I tract regulation

– Center for physical response to emotions

• Examples: Fear = pounding heart, dry mouth, high blood

pressure, sweating, paleness

– Tactile sexual response, not psychological/emotional

response

Diencephalon

• Hypothalamic Function

– Water balance and thirst

– Controls release of hormones by the anterior

pituitary and produces posterior pituitary hormones

– Regulation of sleep-wake cycles

Diencephalon

• Epithalamus

– Forms roof of third ventricle

– Pineal gland, choroid plexus

– Melatonin

– We’ll discuss it’s endocrine function later….

Brain Regions



2. Diencephalon

3. Brain stem (midbrain, pons and medulla)

4. Cerebellum

The Brain Stem

• Functions

– Supports most of the automatic basic life functions

– Pathway for fiber tracts

– Origin for most cranial nerves

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The Brain Stem

• Midbrain

– Associated with visual and auditory reflexes

• Pupillary reflex, startle reflex

– Cranial nerves III and IV

– Red nucleus

• Descending motor pathways involved in voluntary

movement

Figure 12.14

Frontal lobe

Olfactory bulb

(synapse point of

cranial nerve I)Optic chiasma

Optic nerve (II)

Optic tract

Mammillary body

Pons

Medulla

oblongata

Cerebellum

Temporal lobe

Spinal cord

Midbrain

Figure 12.15a

Optic chiasmaView (a)

Optic nerve (II)

Mammillary body

Oculomotor nerve (III)

Crus cerebri of

cerebral peduncles

(midbrain)

Trigeminal nerve (V)

Abducens nerve (VI)Facial nerve (VII)

Vagus nerve (X)

Accessory nerve (XI)

Hypoglossal nerve (XII)

Ventral root of first

cervical nerve

Trochlear nerve (IV)

PonsMiddle cerebellarpeduncle

Pyramid

Decussation of pyramids

(a) Ventral view

Spinal cord

Vestibulocochlear

nerve (VIII)

Glossopharyngeal nerve (IX)

Diencephalon

• Thalamus• Hypothalamus

Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Figure 12.15b

View (b)

Crus cerebri of

cerebral peduncles

(midbrain)

Infundibulum

Pituitary gland


Abducens nerve (VI)

Facial nerve (VII)

Vagus nerve (X)



Pons

(b) Left lateral view


Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Thalamus

Superior colliculus

Inferior colliculus


Superior cerebellar peduncle

Middle cerebellar peduncle

Inferior cerebellar peduncle

Vestibulocochlear nerve (VIII)

Olive

The Brain Stem

• Pons

– Bridge between midbrain and medulla oblongata

– Consists chiefly of tracts connecting different parts

of the CNS

• Longitudinal tracts connect the cerebellum to the

cerebrum and spinal cord

• Transverse tracts connect the two sides of the cerebellum

– Cranial nerves V- VIII (vestibular branch)

Figure 12.14

Frontal lobe

Olfactory bulb

(synapse point of

cranial nerve I)Optic chiasma

Optic nerve (II)

Optic tract

Mammillary body

Pons

Medulla

oblongata

Cerebellum

Temporal lobe

Spinal cord

Midbrain

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Figure 12.15b

View (b)

Crus cerebri of

cerebral peduncles

(midbrain)

Infundibulum

Pituitary gland


Abducens nerve (VI)

Facial nerve (VII)

Vagus nerve (X)



Pons

(b) Left lateral view


Diencephalon

Brainstem

Thalamus

Hypothalamus

Midbrain

Pons

Medulla

oblongata

Thalamus

Superior colliculus

Inferior colliculus


Superior cerebellar peduncle

Middle cerebellar peduncle

Inferior cerebellar peduncle

Vestibulocochlear nerve (VIII)

Olive

The Brain Stem

• Medulla oblongata

– Continuous with spinal cord

• Passage of motor & sensory impulses between brain &

spinal cord

– Decussation of tracts in pyramids

• Pyraminds: large corticospinal tracts descending from

motor cortex

• Reason that each cerebral hemisphere controls voluntary

movements of muscles on the opposite side of the body

Figure 12.10a

Corona radiata

Projection

fibers

Longitudinal fissure

Gray matter

White matter

Association

fibers

Lateral

ventricle

Fornix

Third

ventricle

Thalamus

Pons

Medulla oblongataDecussation

of pyramids

Commissural

fibers (corpus

callosum)

Internal

capsule

Superior

Basal nuclei

• Caudate

• Putamen

• Globus

pallidus

(a)

The Brain Center

• Medulla

– Synapses with neurons in the hypothalamus give

rise to several vital centers

• Cardiac – force and rate of heart contraction

• Vasomotor – changes blood vessel diameter

• Respiratory – rate and depth of breathing

• Swallowing

• Vomiting

– Cranial nerves VIII (cochlear branch) -XII

Brain Regions



2. Diencephalon


4. Cerebellum

The Cerebellum

• Dorsal to the pons & medulla

• Subconsciously provides precise timing &

appropriate patterns of skeletal muscle

contraction

• Contains both white & gray matter

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Figure 12.17b

(b)

Medulla

oblongata Flocculonodular

lobe

Choroid

plexus of

fourth

ventricle

Posterior

lobe

Arbor vitae

(white matter)

Cerebellar cortex

Anterior lobe

Cerebellar

peduncles• Superior• Middle• Inferior

The Cerebellum

• Functions

– Proprioception

• Sensing body position, motion, equilibrium

– Prime mover inhibition and antagonist activation

• Controls strength, direction, and extent of movements

– Progression

• Smooth transition from one body movement to another

• Dysfunction

– Dysmetria

– Dysarthria

Functional Brain Systems

• Networks of neurons that work together & span

wide areas of the brain

– Limbic system

– Reticular formation


• Limbic system

– Structures on the medial aspects of cerebral

hemispheres and diencephalon

– Includes parts of the diencephalon and some

cerebral structures that encircle the brain stem

Figure 12.18

Corpus callosum

Septum pellucidum

Olfactory bulb

Diencephalic structuresof the limbic system

•Anterior thalamicnuclei (flanking3rd ventricle)

•Hypothalamus

•Mammillary

body

Fiber tractsconnecting limbic system structures

•Fornix

•Anterior commissure

Cerebral struc-tures of the limbic system

•Cingulate gyrus

•Septal nuclei

•Amygdala•Hippocampus

•Dentate gyrus

•Parahippocampalgyrus


• Limbic system– Emotional brain

• Recognizes angry or fearful facial expressions

• Assesses danger & elicits the fear response

• Plays a role in expressing emotions via gestures and resolves mental conflict

• Connection to pre-frontal cortex allows us to “count to ten”

– Puts emotional responses to odors• Example: skunks = smell bad

– Alcohol and other depressants affect limbic system control

• Person is subject to exaggerated states of emotion

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• Reticular formation

– Broad columns of nuclei along the length of the

brain stem

– Far-flung axonal connections with hypothalamus,

thalamus, cerebral cortex, cerebellum & spinal cord

– Governs stimulation of the brain as a whole

Figure 12.19

Visualimpulses

Reticular formation

Ascending generalsensory tracts(touch, pain, temperature)

Descendingmotor projectionsto spinal cord

Auditoryimpulses

Radiationsto cerebralcortex


• Functions of the reticular formation

1. Somatic motor control

• Reticulospinal tract = improves smoothness of movement

2. Autonomic control

• Respiratory and cardiovascular centers

3. Arousal

• Reticular Activating System

– Keeps cortex alert and conscious

– Filters incoming sensory information and discards 99% of it

4. Pain modulation

• Can block pain transmission

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