1

Chapter 11Brain Anatomy & Functions

2

Meninges

• Membranes surrounding CNS• Protect CNS• Three layers• Dura mater • Outer layer• Adheres to cranial bones• Tough

3

• Arachnoid mater • Thin, weblike

• Pia mater • Inner layer•Adhere directly to

brain•Very thin• Fibrous and

vascular

Meninges

4

• Spinal Cord• Same three layers

• Provides protection

Meninges

5

Ventricles

• Interconnected cavities •Within cerebral hemispheres and brain stem •Continuous with central canal of spinal cord

• Filled with cerebrospinal fluid (CSF)

6

• Lateral ventricles

• Third ventricle

• Fourth ventricle

• Cerebral aqueduct

Ventricles

7

Ventricles

8

Cerebrospinal Fluid

• Secreted by choroid plexus• Circulates in ventricles, central canal of spinal cord, and subarachnoid space• Completely surrounds brain and spinal cord between the meninges

9

• Clear liquid• 80-150 ml in CNS• Contains proteins,

glucose, and salts• Nutritive and protective

• Shock absorber• Helps maintain stable

ion concentrations in CNS

Cerebrospinal Fluid

10

Spinal Cord

• Slender column of nervous tissue continuous with brain

• Extends downward through vertebral canal

• Begins at level of foramen magnum & terminates near first & second lumbar

11

Cross Section of Spinal Cord

12

Functions of Spinal Cord

• Center for spinal reflexes

• Conduit for nerve impulses to and from the brain

13

Reflex Arcs

Reflexes – automatic, subconscious responses to stimuli within or outside the body

14

Brain

15

Brain

Functions• Interprets sensations• Determines perception• Stores memory• Reasoning• Makes decisions• Coordinates muscular movements• Regulates visceral activities• Determines personality

Major Parts• Cerebrum

• Two hemispheres• Basal nuclei • Diencephalon• Brainstem• Cerebellum

16

Brain

17

Brain Development

Three Major Vesicles1. Forebrain2. Midbrain3. Hindbrain

18

Brain Development

19

• Looks like cap of a mushroom

• Spread over diencephalon

• 7/8 total mass • Fills most of

cranium

Cerebrum

20

• Result from displacement & distortion of neurons at the moment of impact

• Concussion•Abrupt but temporary loss of consciousness

following a blow to the head or the sudden stopping of a moving head

•No visible bruising but post traumatic amnesia may occur

Clinical Application: Cerebrum

21

• Contusion•Visible bruising of the brain due to trauma

and blood leaking from microscopic vessels

• Pia mater is torn

•Results in unconsciousness for several minutes to many hours

Clinical Application: Cerebrum

22

• Laceration• Tearing of the brain, usually from skull

fractures or gunshot wound

• Large blood vessels bleed into the brain and can cause cerebral hematoma, and increase cranial pressure

Clinical Application: Cerebrum

23

Lobes of Cerebral Hemispheres

• Name of lobe corresponds with name of cranial bone

• Frontal• Parietal• Temporal• Occipital• Insula

24

Functions of the Cerebrum• Interpreting impulses

• Initiating voluntary movements

• Storing information as memory

• Retrieving stored information

• Reasoning

• Seat of intelligence and personality

25

Functional Regions of Cerebral Cortex

Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system

26

• Cerebral Cortex • Surface of cerebrum

• Convolutions • Folds in cerebrum• Bumps or gyri

• Sulci• Shallow grooves

• Fissures• Deep grooves

Structure of Cerebrum

27

Structure of Cerebrum

• Corpus callosum• Connects cerebral hemispheres

• Longitudinal fissure• Separates hemispheres

• Transverse fissure• Separates cerebrum from cerebellum

28

Sensory Areas

• Cutaneous Sensory Area

• Parietal lobe

• Interprets sensations on skin

• Visual Area• Medial Occipital lobe

• Interprets vision

29

• Primary Gustatory• Taste

• Near bases of the central sulci

• Primary Olfactory • Smell

• Arise from centers deep within the cerebrum

Sensory Areas

30

• Auditory Area• Superior part

of temporal lobe near lateral cerebral sulcus

• Interprets hearing

Sensory Areas

31

Sensory Areas

32

Association Areas

• Regions that are not primary motor or primary sensory areas• Widespread throughout the cerebral cortex• Analyze and interpret sensory experiences• Provide memory, reasoning, verbalization, judgment, emotions

33

Association Areas

Frontal Lobe Association Areas• Concentrating• Planning• Complex problem solving

Parietal Lobe Association Areas• Understanding speech• Choosing words to express thought

Temporal Lobe Association Areas• Interpret complex sensory experiences • Store memories of visual scenes, music, and complex patterns

Occipital Lobe Association Areas• Analyze and combine visual images with other sensory experiences

34

Hemisphere Dominance

• The left hemisphere is dominant is most individuals

• Dominant hemisphere controls

• Speech• Writing• Reading• Verbal skills• Analytical skills• Computational skills

• Nondominant hemisphere controls

• Nonverbal tasks• Motor tasks• Understanding and interpreting musical and visual patterns• Provides emotional and intuitive thought processes

35

• Anatomical• Frontal lobe of left hemisphere is smaller

• Left handed people•Right parietal and occipital lobes are narrower

Hemisphere Differences

36

• Right Hemisphere• Left handed

• Music and artistic awareness

• Space and patter perception

• imagination

• Left Hemisphere• Right handed

• Numerical and scientific skills

• Sign language and reasoning

Hemisphere Differences

37

Memory

Short Term• Working memory• Closed neuronal circuit• Circuit is stimulated over and over• When impulse flow ceases, memory does also• Unless it enters long-term memory via memory consolidation

Long Term• Changes structure or function of neurons• Enhances synaptic transmission

38

Motor Areas

• Primary Motor Areas• frontal lobes• control voluntary muscles

• Broca’s Area• anterior to primary motor cortex• usually in left hemisphere• controls muscles needed for speech

• Frontal Eye Field• above Broca’s area• controls voluntary movements of eyes and eyelids

39

Motor Areas

40

Functions of the Cerebral Lobes

41

Diencephalon

• Between cerebral hemispheres and above the brainstem• Surrounds third ventricle

• Thalamus• Hypothalamus• Optic tracts• Optic chiasma• Infundibulum• Posterior pituitary• Mammillary bodies• Pineal gland

42

Diencephalon

Thalamus•Oval structure above midbrain

•Gateway for sensory impulses heading to cerebral cortex

• Receives all sensory impulses (except smell)

• Channels impulses to appropriate part of cerebral cortex for interpretation

•Interpretation of pain, temperature, and pressure

43

Hypothalamus• Small portion inferior to thalamus• Protected by sella turcica • Maintains homeostasis by regulating visceral

activities • Water concentrations• Hormone concentrations• Blood temperature

• Links nervous and endocrine systems

Diencephalon

44

• Homeostatic functions• Regulates autonomic nervous system• Reception & integration of sensory impulses from

viscera• Mind over body (stress--heart rate increases)• Rage & aggression• Regulates body temperature• Regulates food intake (hunger & full feelings)• Thirst• Sleep patterns

Diencephalon

45

Diencephalon

Consists of• portions of frontal lobe• portions of temporal lobe• hypothalamus• thalamus• basal nuclei• other deep nuclei

Functions• controls emotions• produces feelings• interprets sensory impulses

Limbic System

46

Brain Stem

Three Parts1. Midbrain2. Pons3. Medulla Oblongata

47

Midbrain

•“Mesencephalon”

•Between diencephalon and pons

• Contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain

48

• Cerebral aqueduct– Connects 3rd & 4th

ventricles of brain• Cerebral peduncles – bundles

of nerve fibers– Motor pathway between

cerebrum & lower parts of nervous system

• Corpora quadrigemina – centers for visual and auditory reflexes

Midbrain

49

Pons

• Rounded bulge on underside of brainstem

• Between medulla oblongata and midbrain

• Helps regulate rate and depth of breathing

• Relays nerve impulses to and from medulla oblongata and cerebellum

50

Medulla Oblongata

• Enlarged continuation of spinal cord• Conducts ascending and descending impulses between brain and spinal cord• Contains 3 reflex centers

• Cardiac•Heart rate & force of contraction

• Vasomotor•Controls diameter of blood vessels

• Respiratory •Controls breathing patterns

51

• Contains various nonvital reflex control centers – Coughing

– Sneezing

– Swallowing

– Vomiting

Medulla Oblongata

52

• Reticular Formation• Complex network of nerve fibers scattered throughout the brain stem

• Extends into the diencephalon

• Connects to centers of hypothalamus, basal nuclei, cerebellum, and cerebrum

• Filters incoming sensory information

• Arouses cerebral cortex into state of wakefulness

Medulla Oblongata

53

Cerebellum

• Inferior to occipital lobes• Posterior to pons and medulla oblongata• Two hemispheres

• Vermis connects hemispheres• Cerebellar cortex

• Gray matter on surface• Arbor vitae

• White matter inside•Tree-like pattern

• Cerebellar peduncles • nerve fiber tracts

54

• Dentate nucleus • Largest nucleus in

cerebellum• Integrates sensory

information concerning position of body parts

• Coordinates skeletal muscle activity

• Maintains posture

Cerebellum

55

• Damage results in• Lack of muscle control

• Change of speech pattern

• Severe dizziness

• Disturbances of gait (walking)

Cerebellum

56

Life-Span Changes

• Brain cells begin to die before birth• Over average lifetime, brain shrinks 10%• Most cell death occurs in temporal lobes• By age 90, frontal cortex has lost half its neurons• Number of dendritic branches decreases• Decreased levels of neurotransmitters• Fading memory• Slowed responses and reflexes• Increased risk of falling• Changes in sleep patterns that result in fewer sleeping hours

57

Clinical Application

Cerebral Injuries and Abnormalities

Cerebral Palsy• Motor impairment at birth• Caused by blocked cerebral blood vessels during development• Seizures• Learning disabilities

Cerebrovascular Accident• Stroke• Sudden interruption in blood flow• Brain tissues die