1

Brain

I. Overview

II. Brain Stem

III. Cerebellum

IV. Diencephalon

V. Cerebrum

VI. Cranial Nerves

2

Brain

I. Overview

A. Function

B. Protection

C. Blood Supply

D. Cerebrospinal Fluid

II. Brain Stem

III. Cerebellum

IV. Diencephalon

V. Cerebrum

VI. Cranial Nerves

3

The Brain and Cranial Nerves

1. Sensations

2. Memory

3. Emotions

4. Decision making

5. Behavior

4

Principal Parts of the Brain

1. Cerebrum

2. Diencephalon

a) Thalamus

b) Hypothalamus

3. Cerebellum

4. Brainstem

a) Medulla

b) Pons

c) Midbrain Cerebell

um

Brain Stem

Cerebrum

Diencephalon

5

Protective Coverings of the Brain

Pia Mater

Bone

Periosteum

Meninges same as around the spinal cord

1. dura mater

2. arachnoid mater

3. pia materArachnoid

Mater

PeriosteumAnd Bone

Dura Mater

6

Protective Coverings of the Brain

Dura mater extensions

1. falx cerebri

2. tentorium cerebelli

3. falx cerebelli

Falx cerebri

Falx cerebelli

Tentorium cerebelli

7

Blood Supply to Brain

Arterial blood supply is branches from circle of Willis on base of brain

Vessels on surface of brain----penetrate tissue

Uses 20% of our bodies oxygen & glucose needs

blood flow to an area increases with activity in that area

deprivation of O2 for 4 min does permanent injury

at that time, lysosome release enzymes

waste

Capillary

Ependymal cells

O2

Fluid

Elec.

Glucose

8

Blood Supply to Brain

Blood-brain barrier (BBB)

protects cells from some toxins and pathogens

proteins & antibiotics can not pass but alcohol & anesthetics do

tight junctions seal together epithelial cells, continuous basement membrane, astrocyte processes covering capillaries

waste

Capillary

Ependymal cells

O2

Fluid

Elec.

Glucose

9

Cerebrospinal Fluid (CSF)

80-150 ml (3-5oz)

Clear liquid containing glucose, proteins, & ions

Functions

1. mechanical protection

floats brain & softens impact with bony walls

2. chemical protection

optimal ionic concentrations for action potentials

3. circulation

nutrients and waste products to and from bloodstream

10

Origin of CSF

Choroid plexus = capillaries covered by ependymal cells

2 lateral ventricles, one within each cerebral hemisphere

roof of 3rd ventricle

fourth ventricle

Choroid plexus

Lateral Ventricle

s

Third Ventricle

sFourth

Ventricles

11

Drainage of CSF from Ventricles

One median aperture & two lateral apertures allow CSF to exit from the interior of the brain Lateral

apertureMedian aperture

15

Brain

I. Overview

II. Brain Stem

A. Medulla Oblongata

B. Pons

C. Midbrain

D. Reticular Formation

III. Cerebellum

IV. Diencephalon

V. Cerebrum

VI. Cranial Nerves

16

Medulla Oblongata

Continuation of spinal cord

Ascending sensory tracts

Descending motor tracts

Nuclei of 5 cranial nerves

Cardiovascular center

force & rate of heart beat

diameter of blood vessels

Respiratory center

medullary rhythmicity area sets basic rhythm of breathing

Information in & out of cerebellum

Reflex centers for coughing, sneezing, swallowing etc

Medulla

17

Ventral Surface of Medulla Oblongata

Ventral surface bulge

pyramids

large motor tract

decussation of most fibers

left cortex controls right muscles

Olive = olivary nucleus

neurons send input to cerebellum

proprioceptive signals

gives precision to movements

18

Dorsal Surface of Medulla Oblongata

Nucleus gracilis & nucleus cuneatus = sensory neurons

relay information to thalamus on opposite side of brain

5 cranial nerves arise from medulla -- 8 thru 12

Nucleus gracilis

Nucleus cutaneou

s

CN 7CN 8CN 9CN 10CN 11

CN 12

19

Injury to the Medulla

Hard blow to the back of the head may be fatal

Cranial nerve malfunctions on same side as injury;loss of sensation or paralysis of throat or tongue; irregularities in breathing and heart rhythm

20

Pons

One inch long

White fiber tracts ascend and descend

Pneumotaxic & apneustic areas help control breathing

Middle cerebellar peduncles carry sensory info to the cerebellum

Cranial nerves 5 thru 7

Pons

21

Midbrain

One inch in length

Extends from pons to diencephalon

Cerebral aqueduct connects 3rd ventricle above to 4th ventricle below

Midbrain

Third ventricle

Fourth ventricle

Cerebral aqueduc

t

22

Midbrain in Section

Cerebral peduncles

clusters of motor & sensory fibers

Substantia nigra

helps controls subconscious muscle activity

Dopamine

Red nucleus

rich blood supply & iron-containing pigment

cortex & cerebellum coordinate muscular movements by sending information here from the cortex and cerebellum Cerebral

peduncles

Red nucleus

Substantia nigra

23

Dorsal Surface of Midbrain

Corpora quadrigemina

superior colliculi

inferior colliculi

coordinate eye movements with visual stimuli

coordinate head movements with auditory stimuli

Superior colliculi

Inferior colliculi

24

Midbrain

Superior, middle & inferior peduncles attach to brainstem

inferior carries sensory information from spinal cord

middle carries sensory fibers from cerebral cortex & basal ganglia

superior carries motor fibers that extend to motor control areas

Inferior peduncle

s

Superior

peduncles

25

Reticular Formation

Scattered nuclei in medulla, pons & midbrain

Reticular activating system

alerts cerebral cortex to sensory signals (sound of alarm, flash light, smoke or intruder) to awaken from sleep

maintains consciousness & helps keep you awake with stimuli from ears, eyes, skin and muscles

Motor function is involvement with maintaining muscle tone

Reticular formatio

n

26

Brain

I. Overview

II. Brain Stem

III. Cerebellum

IV. Diencephalon

V. Cerebrum

VI. Cranial Nerves

27

Cerebellum

2 cerebellar hemispheres and vermis (central area)

Function

correct voluntary muscle contraction and posture based on sensory data from body about actual movements

sense of equilibrium

Vermis

28

Cerebellum

Transverse fissure between cerebellum & cerebrum

Cerebellar cortex (folia) & central nuclei are grey matter

Arbor vitae = tree of life = white matter

29

Brain

I. Overview

II. Brain Stem

III. Cerebellum

IV. Diencephalon

A. Thalamus

B. Hypothalamus

C. Epithalamus

D. Circumventricular Organs

V. Cerebrum

VI. Cranial Nerves

30

Diencephalon Surrounds 3rd Ventricle

Surrounds 3rd ventricle

Superior part of walls is thalamus

Inferior part of walls & floor is hypothalamus

Thalamus

(enclosed in 3rd

ventricle)

Hypothalamus

31

ThalamusThalamu

s (enclosed in 3rd

ventricle)

1 inch long mass of gray mater in each half of brain (connected across the 3rd ventricle by intermediate mass)

Relay station for sensory information on way to cortex

Crude perception of some sensations

32

Thalamic Nuclei

Nuclei have different roles

relays auditory and visual impulses, taste and somatic sensations

receives impulses from cerebellum or basal ganglia

anterior nucleus concerned with emotions, memory and acquisition of knowledge (cognition)

Emotions

Motor

Visual

Auditory

Emotions

Emotions,

Alertness,

Memory

Integrates with other

nuclei

33

Hypothalamus

Dozen or so nuclei in 4 major regions

mammillary bodies are relay station for olfactory reflexes

infundibulum suspends the pituitary gland

Major regulator of homeostasis

receives somatic and visceral input, taste, smell & hearing information; monitors osmotic pressure, temperature of blood

SmellConnects

to pituitary

gland

Pituitary gland

34

Functions of Hypothalamus

Controls and integrates activities of the ANS which regulates smooth, cardiac muscle and glands

Synthesizes regulatory hormones that control the anterior pituitary

Contains cell bodies of axons that end in posterior pituitary where they secrete hormones

Regulates rage, aggression, pain, pleasure & arousal

Feeding, thirst & satiety centers

Controls body temperature

Regulates daily patterns of sleep

SmellConnects

to pituitary

gland

Pituitary gland

35

Epithalamus

Pineal gland

endocrine gland the size of small pea

secretes melatonin during darkness

promotes sleepiness & sets biological clock

Habenular nuclei

emotional responses to odors

Pineal gland

Habenular nuclei

36

Subthalamus & CVO

Subthalamus

small area just inferior to thalamus

work with basal ganglia, cerebrum & cerebellum to control body movements

Circumventricular organs

in walls of 3rd & 4th ventricles

monitor changes in blood chemistry because lack blood brain barrier (parts of hypothalamus, pineal & pituitary gland)

sites of entry of HIV virus into brain (dementia)

37

Brain

I. Overview

II. Brain Stem

III. Cerebellum

IV. Diencephalon

V. Cerebrum

A. Lobes

B. White Matter

C. Basal Ganglia

D. Limbic System

E. Function of Cortex

1. Sensory

2. Motor

3. Association

4. Lateralization

5. Brain Waves

VI. Cranial Nerves

38

Cerebrum (Cerebral Hemispheres)

Cerebral cortex is gray matter overlying white matter

2-4 mm thick containing billionsof cells

grew so quickly formed folds(gyri) and grooves (sulci or fissures)

Gray matter

White matter

39

Cerebrum (Cerebral Hemispheres)

Longitudinal fissure separates left & right cerebral hemispheres

Corpus callosum is band of white matter connecting left and right cerebral hemispheres

Corpus callosum

Longitudinal

fissure

40

Lobes and Fissures Each hemisphere is subdivided into 4

lobes

1. Frontal lobe

Motor area

Personality, behavior

Emotions

Memory

2. Parietal lobe

Somatosensory – skin and muscle

3. Occipital lobe

Vision

4. Temporal lobe

Hearing

Smell

Taste

Frontal Parietal

Temporal

Occipital

41

Lobes and Fissures

Central sulcus (black)

precentral & postcentral gyrus

Parieto-occipital sulcus (red)

Lateral sulcus (yellow)

Frontal Parietal

Temporal

Occipital

43

Cerebral White Matter

1. Association fibers between gyri in same hemisphere

2. Commissural fibers from one hemisphere to other

3. Projection fibers form descending & ascending tracts

Association fibers

Commisural fibers

Projection fibers

44

Basal Ganglia

Connections to red nucleus, substantia nigra & subthalamus

Input & output with cerebral cortex, thalamus & hypothalamus

Control large automatic movements of skeletal muscles

Parkinson’s Disease

Caudate

Globus pallidusPutamen

45

Limbic System

Emotional brain

intense pleasure & intense pain

Strong emotions increase efficiency of memory

47

Sensory Areas of Cerebral Cortex

Receive sensory information from the thalamus

Primary somatosensory area = postcentral gyrus = 1,2,3

Primary visual area = 17

Primary auditory area = 41 & 42

Primary gustatory area = 43

48

Motor Areas of Cerebral Cortex

Voluntary motor initiation

Primary motor area = 4 = precentral gyrus

controls voluntary contractions of skeletal muscles on other side

Motor speech area = 44 = Broca’s area

production of speech -- control of tongue & airway

49

Association Areas of Cerebral Cortex

Somatosensory area = 5 & 7 (integrate & interpret)

Visual association area = 18 & 19 (recognize & evaluate)

Auditory association area(Wernicke’s) = 22(words become speech)

Gnostic area = 5,7,39 & 40 (integrate all senses & respond)

Premotor area = 6 (learned skilled movements such as typing)

Frontal eye field =8 (scanning eye movements such as phone book)

51

Hemispheric Lateralization

Functional specialization of each hemisphere more pronounced in men

Females have larger connections between 2 sides

Damage to left side produces aphasia

Damage to same area on right side produces speech with little emotional inflection

52

Electroencephalogram (EEG)

Brain waves are millions of nerve action potentials in cerebral cortex

diagnosis of brain disorders (epilepsy)

brain death (absence of activity in 2 EEGs 24 hours apart)

1. Alpha -- awake & resting

2. Beta -- mental activity

3. Theta -- emotional stress

4. Delta -- deep sleep

53

Brain

I. Overview

II. Brain Stem

III. Cerebellum

IV. Diencephalon

V. Cerebrum

VI. Cranial Nerves

54

Cranial Nerves

I. Olfactory

II. Optic

III. Oculomotor

IV. Trochlear

V. Trigeminal

VI. Abducens

VII. Facial

VIII. Vestibulocochlear

IX. Glossopharyngeal

X. Vagus

XI. Accessory

XII. hypoglossal

CN I

CN II

CN III

CN IV

CN V

CN VI

CN VII

CN VIII

CN IX

CN X

CN XI

CN XII

55

I -- Olfactory Nerve (S)

Extends from olfactory mucosa of nasal cavity to olfactory bulb

Sense of smell

Anosmia – loss of smell

56

II -- Optic Nerve (S)

Connects to retina supplying vision

Defect in

Visual acuity

Visual field

Visual field defect

Visual acuity defect

57

III = Oculomotor Nerve (S/M)

Sensory:

Proprioception – sense of position

Motor:

Levator palpebrae raises eyelid

Ptosis – drooping of eyelid

4 extrinsic eye muscles

Superior, medial, inferior, and inferior oblique

2 intrinsic eye muscles

accomodation for near vision (changing shape of lens during reading)

constriction of pupil

Diplopia – double vision

58

IV = Trochlear Nerve (M)

Sensory:

Proprioception – sense of position

Motor:

Superior oblique eye muscle

59

V = Trigeminal Nerve S/M)

Sensory:

touch, pain, & temperature receptors of the face

1. ophthalmic branch

2. maxillary branch

3. mandibular branch

Motor:

muscles of mastication

Tic douloureux - severe, stabbing

pain to one side of the face.

60

VI = Abducens Nerve (S/M)

Sensory:

Proprioception – sense of position

Motor:

Lateral rectus eye muscle

61

VII = Facial Nerve (S/M)

Sensory:

taste buds on anterior 2/3’s of tongue

Motor:

facial muscles

salivary & nasal and oral mucous glands & tears

Bell’s Palsy

62

VIII = Vestibulocochlear Nerve (S/M)

Cochlear branch begins in medulla

receptors in cochlea

hearing

if damaged deafness or tinnitus (ringing) is produced

Vestibular branch begins in pons

receptors in vestibular apparatus

sense of balance

vertigo (feeling of rotation)

ataxia (lack of coordination)

63

IX = Glossopharyngeal Nerve (S/M)

Sensory:

Somatic sensations & taste on posterior 1/3 of tongue

Motor:

Stylopharyngeus m. (lifts throat during swallowing)

Secretions of parotid gland

64

X = Vagus Nerve (S/M)

Sensory:

Receives sensations from viscera

Motor:

Controls cardiac muscle and smooth muscle of the viscera

Controls secretion of digestive fluids

Bradycardia

65

XI = Spinal Accessory Nerve (S/M)

Cranial portion

arises medulla

skeletal mm of throat & soft palate

Spinal portion

arises cervical spinal cord

sternocleidomastoid and trapezius mm.

66

XII = Hypoglossal Nerve (S/M)

Sensory:

Proprioception – sense of position

Motor:

Controls muscles of tongue during speech and swallowing

Injury deviates tongue to injured side when protruded