Chapter 12

Page 1

I. Central Nervous

System

A. development

1. neural plate

· ridge in middle of ectoderm

2. neural tube

· hollow

· becomes CNS

3. neural crest

· give rise to PNS

4. swellings in

neural tube and what they become

a.) primary

vesicles

· forebrain- prosencephalon

· midbrain- mesencephalon

· hindbrain- rhombencephalon

b.)

secondary vesicles

· forebrainà telencephalon (cerebral)

àdiencephalon (thalamus, hypothalamus)

· midbrainà midbrain

· hindbrainà metencephalon à pons, cerebellum

à

myelencephalon àmedulla

B. Regions of Adult Brain

1. Ventricles

· contain CSF=

cerebrospinal fluid

· a.) lateral ventricles (2)- “C” shaped

o interventricular foramen to 3rd ventricle

· b.) 3rd ventricle- on midline

o cerebral aqueduct to 4th ventricle

· c.) 4th ventricle

o under cerebellum

2. cerebral hemispheres

a.) cortex

· outer, wrinkly, gray matter (thin layer lining

without fatty stuff like white matter)

o gyri = bumps

o sulci = grooves (in between the bumps)

(i)

frontal lobe

· part of the brain that is in front of central

sulcus

· personality (Phineas Gage)

· for speech- Broca’s area on lift side of the brain

(lateralized)

· motor control- precentral gyrus is primary motor

cortex

(ii) parietal lobe

· somatic sensation

o postcentral gyrus is primary sensory cortex

(iii)

temporal lobe

· primary auditory cortex

· deep structure includes hippocampus important for

memory

(iv)

occipital lobe

· primary visiual cortex

(v)

large sulci

· central

sulcus- separates frontal from parietal

· lateral sulcus- separates temporal from parietal

· longitudinal fissure between left and right

hemispheres

· transverse fissure between cerebrum and cerebellum

· parieto occipital sulcus

b.) white

matter – made white by oligodendrocytes of tracts

(i)

commissures

· connect left and right halves

o e.g. corpus callosum

(ii)

association fibers

· local axons

(iii)

projection fibers

· long distance axons

o e.g. corticospinal tract for movement control

c.) basal

nuclei (basal ganglia)

(i)

corpus striatum =

caudate + putamen

· motor control

· cells die in Huntington’s disease

(ii)

globus pallidus - internal and external

· motor control

(iii)

Parkinson’s vs. Huntington’s disease

· Parkinson’s disease:

o basal nuclei lose input from substantia nigra as it

does off and dopamine lost

o treat with left-dopa and brain stimulation

o tremor at rest, difficulty starting movement,

shuffle (walking), mask (facial appearance), soft spoken

· Huntington’s disease

o basal nuclei cells die

o autosomal dominant

o continuous movement mental deterioration

o fatal

o treat with dopamine blockers

3. diencephalon

a.) thalamus

· relays information to cortex

o lateral geniculate nucleus relays visual information

to occipital cortex

o medial geniculate nucleus relays auditory

information to temporal cortex

· intermediate mass- connects left and right half

b.) hypothalamus

· below thalamus, above pituitary

· controls endocrine functions of pituitary by way of

infundibulum

· motivation/ satisfaction

· autonomic, homeostatic functions

c.) epithalamus

· pineal gland

o makes melatonin- sleepy hormone

4. brainstem

a.) midbrain

- between pons and diencephalon

· cerebral peduncles (feet of the cerebral)

· cerebral aqueduct

· superior colliculus- visual relexes

· inferior colliculus- auditory reflexes

· substantia nigra (dies in Parkinson’s)

b.) pons

– “bridge”

· fiber tracts

· nuclei for coronial nerves V- VIII (5-8)

c.) medulla

oblongata

· spinal cord of head

· pyramids- axons (projection) from motor cortex

o decussation- crossing place

· cardiovascular and respiratory control

5. Cerebellum

· fine tuning of movement

· balance

a.) cortex:

“folia” ridges of cerebellum

· two hemispheres (Left and Right) with vermis

intermediate

o

each had lobes

o

e.g. anterior,

posterior

· purkinje cells large cells send axons to deep

cellular nuclei

b.) arbor

vitae - white matter

· myelinated axons to and from the cerebellar cortex

c.) deep

cerebellar nuclei- gray matter

(many somas)

· sends signals to others brain areas to control

movement

· affects movement on same side of body

· sends signals to thalamus to motor cortex and

brainstemà

spinal cord

6. The limbic system

· group of brain areas involved in emotion

a.) amygdala

“almond”

· deep to temporal lobe

· fear and aggression

b.)

hypothalamus

·

in

diencephalon (see above)

·

desire/ satisfaction

c.)

cingulate gyrus

·

belt of cortex

above corpus callosum

·

conflict, pain

·

Tan: left front Broca’s; learned from him, his

speech production was slow, but was able to process what he heard

·

Gage: pre-frontal cortex; his problems was emotional

control, making choices

·

HM: hippocampus; hard time learning new things

·

Charles Whitman: amygdala; went from being a

well-respected young man to killing people (knew something was wrong with his

brain)

C. Sleep

1. Stages of sleep

· we cycle through different stages of sleep; go

through the stages of sleep 4-5 times each night

· stage 1:

relax- show alpha waves

· stage 2:

more relax-show alpha waves and sleep spindles (bumps/ jumps of burst on graph)

· stage 3:

deeper- mix of delta and theta waves

· stage 4:

deepest- all delta

· REM

(about an hour of sleep): eyes move, EEG is high frequency

o other movements inhibited (so we don’t act out our

dreams)

o dream (story dream)

D. Memory

1. Stages of memory

· a.) short term- lasts for a few seconds; stores <

10 items

· b.) long term- some memories are consolidated and

can last for years

o rehearsal and associating new data with stored data

2. Categories of memory

· declarative memories- recall facts

o patients HM lost ability to form new ones

· procedural memories- skills learning

o patient HM kept this

3. Brain structures involved in

memory

· for declarative memory: hippocampus and basal

forebrain are important; Ach is important (not the only one)

· for procedural memory: basal nuclei and premotor

cortex help form memories; dopamine is important (not the only one)

E. Protections of

the CNS

1. Meninges = “membranes” (PAD the CNS)

· a.) pia: inner, thin

· b.) arachnoid matter: middle layer (looks like a

spider web)

o has CSF under it in subarachnoid space

· c.) dura mater: outer thick- periosteal (outer) and

meningeal (inner) layers

o i.) falx cerebri: in longitudinal fissure

o ii.) falx cerebelli: behind cerebellum midline

o iii.) tentorium cerebelli: in transverse fissure

(sits between the falx cerebri and falx cerebelli)

2. C.S.F. = cerebrospinal fluid

· a.) plasma likes fliud

· b.) around (subarachnoid space) CNS and inside it

(ventricles central canal)

(baths

and surrounded by)

· c.) made by choroid plexus (network of capillaries)-

ventricles capillaries; drained back to blood in dural sinuses

3. Blood brain barrier

· protect chemical environment of brain

· made up of capillary wall cells in the brain are

tightly joined

· astrocytes reinforce the barrier

· not absolute

F. Cranial Nerves

(generally part of PNS; come off brain: Roman Numerals) (look at figure 13.30 in the

textbook)

CN I

· olfactory nerve- smell

CN II

· optic nerve- see

CN III

· oculomotor nerve- move eyes

CN IV

· trochlear nerve- moves the eyes (moves them in a

weird twisty motion)

o e.g. looking in the mirror, tilt head to the side,

notice eyes will twist a little

CN V

· trigeminal nerve- touch of face; also has the

function to help us chew (mixed nerve has both sensory and motor)

CN VI

· abducens nerve- moves eyes laterally

CN VII

· facial nerve- facial expression; taste

CN VIII

· vestibulocochlear nerve- balance and hearing

CN IX

· glossopharyngeal nerve- sensory, motor for tongue

and throat

CN X

· vagus nerve- parasympathetic system (rest and

digest)

o e.g. slows heart

CN XI

· accessory nerve- controlling neck muscles

CN XII

· hypoglossal nerve- controls tongue muscles

G. Spinal Cord - nervous tissue - about as thick as one

finger

1. extent

· starts at foramen magnum; ends at L1 vertebra (¯ pointing at the bullet point underneath)

o conus medullaris – inferior end

o cauda equina – nerves within L vertebrae, sacrum

2. enlargements

· cervical enlargement: for upper limb

· lumbar enlargement: for lower limb

3. in cross section (drawing)

a.) central

grooves

· anterior medial fissure

· posterior medial sulcus

b.) grey

matter

· central canal is in grey commissure

· 1.) dorsal horn- interneurons for touch/ pain

o receive input unipolar sensory neurons (sensory

neurons somas are in dorsal root ganglion)

· 2.) ventral horn- somas of motor neurons

· 3.) lateral horn- somas of sympathetic (fight/

flight)

neurons

c.) white

matter (look at figure 12.30; draw

it)

(i).

main columns (funiculi)

· anterior, posterior (dorsal), lateral columns

· made of myelinated tracts (that makes it white

because there is a chuck of it)

(ii). ascending tracts within columns

· fasciculus gracilis (for lower limb) and fasciculus cuneatus

(for upper limb) are within dorsal column- light touch, proprioception

· lateral spinothalamic trac is in lateral column-

carries information about pain and temperature

(iii).

descending tracts (motor)

· lateral corticospinal tract in lateral column

o axons project from motor cortex go through this

tract and control spinal cord motor neurons

§ function in finely controlled movements