I. Central Nervous System – Brain and spinal cord
A. Spinal Cord –
1. Protection & Coverings – vertebrae – key
protection of bone
a.meninges – connective tissue coverings around
spinal cord and brain
- spinal meninges
- cranial meninges
Meningitis – inflammation of the
meninges
 dura mater – outer most layer “tough mother”
- irregular shaped
- cranial and spinal
 epidural space – fat and connective tissue
located here to protect spinal cord
 arachnoid – middle layer – spinal layer
- delicate web like appearance
- continous with arachnoid of brain
 pia mater – inner layer “delicate mother”
transparent layer of collagin and elastic fibers
that adhere to surface of spinal cord and brain
- has numerous blood vessels
 subarachnoid space – between arachnoid and
pia matter
- where cerebrospinal fluid circulates
fluid taken from here during spinal tap
2. General Features
a. length – 42-45 cm (16-18 inches)
- extend from foramen magnum to 2nd lumbar
vertebrae (not entire length of vertebral column)
b. cauda equina – nerves arising from lower
portion of cord angles down – “horses trail”
c. cervical enlargement – contains upper
extremity nerves
d. lumbar enlargement – nerves for lower
extremity
e. spinal segments – 31 spinal segments
3. Cross section structure – page 232
a. anterior median fissure - deep
b. posterior median sulcus – shallow
c. gray matter – H shaped – surrounded by
white matter
d. white matter – outer layer
4. Functions –
a. impulse conduction –
 spino thalamic tracts – pain, temperature,
crude touch, deep pressure
 posterior column tracts
 proprioception – muscle movement,
awareness
 discriminative touch
 2 point discrimination
 pressure
 vibrations
 pyramidal tracts – precise skeletal muscle
movements
 extrapyramidal tracts –
 head movements
 muscle tone
 posture
 equilibrium
b. reflex center – spinal reflexes
- fast, predictable, automatic response to a
change in the environment
 spinal nerves connect spinal cord tracts
and periphery – each pair connects at
roots –
 posterior (dorsal root) – sensory
only – to gray horn
 dorsal root ganglion – swelling
 anterior (ventral) – motor root –
takes to periphery
c. reflex arc and homeostasis
- pathway – origin – termination
1. receptor – sensory neuron portion –
generates impulse
2. sensory neuron
3. integrating center – part of CNS – on to
motor
4. motor neuron – to organ
5. effector – muscle or gland that responds
B. Spinal nerves – connects CNS to sensory receptors,
muscles and glands – part of SNS – 31 pairs
1. Names – named by region and level of spinal cord
from where they emerge – 8 pair cervical, 12 pair
thoracic, 5 pair lumbar, 5 pair sacral, 1 pair
coccygeal
- 1st pair exits the spinal cord between the atlas and
the occipital bone – all others exit through
intervertebral foramina
2. Composition - anterior and posterior root attachments
- mixed nerve – both sensory and motor fibers
3. Distribution –
a. branches – rami – dorsal, ventral
b. plexuses – ventral except T2 to T11 form
networks of nerves on both sides called plexuses
– cervical, brachial, lumbar, sacral (pg 256)
c. intercostal nerves – T2 to T11 intercostal or
thoracic nerves – muscles between ribs,
abdominal, skin, chest and back
C. Brain – (mushroom shaped) – one of the largest
shaped organs – weighs 3 lbs (1300g)
- 4 parts – protected by cranium and meninges
1. Cerebrospinal fluid – CSP – circulates through
subarachnoid space, around brain and spinal cord
and through ventrictes of brain
- ventricles – cavities of brain that communicate with
each other
- 2 lateral, 1 3rd and 1 4th ventricles
- 80-150 ml of CSF in CNS
- contains glucose, proteins, urea, and salts
- protects (shock absorber) – circulation functions
2. Blood supply – hydrocephalus – tumor or
blockage which causes accumulation
- well supplied with O2 and nutrients by a
circulatory route called circle of willis – (fig 16.9)
-brain requires 20% of body’s oxygen
- brief interruption - faint
- 1-2 min weakens cells, 4 min – permanent injury
because lysosomes destroy brain cells by releasing
enzymes
- blood also contains glucose – BBB blood brain
barrier controls rates
- protects brain cells but antibiotic cannot enter
3. Brain Stem – brain has no carbo storage so it
needs constant glucose
- Medulla oblongata - continuation of spinal
cord
- contains all ascending and descending tracts
between spinal cord and brain (white matter)
- 2 triangular pyramids – crosses sides decussation of pyramids – one side controls
other side
- severe blow to mandible twists and distorts
brain stem – (knock out)
- regulates rate and force of heartbeat and
breathing rhythm
- Pons – bridge – located above medulla and
consists of nucleii and scattered white fibers
- connects spinal cord to brain and brain
parts together
- helps regulate breathing
- Midbrain – pons to lower portion of
diencephalon
- contains motor fibers that connect cerebral
cortex to pons and spinal cord
- fibers that connect spinal cord to thalamus
- nuclei for oculomotor and truchlear nerves
4. Diencephalon – “through brain”
- Thalamus – mostly gray matter – serves as
relay station for sensory impulses
 Interpret impulses like pain,
temperature, light touch and pressure
- Hypothalamus – contains mostly
homeostatic mechanisms
1. autonomic nervous system – heart
rate, gastrovascular movement, urinary
bladder contraction
2. body temperature
3. rage and aggression
4. food intake
5. thirst center
6. conciousness and sleep patterns
5. RAS – reticular activating system
- circadian rhythm – 24 hr sleep and wake
pattern
- arousal caused by thalamus
- conciousness is a result – inactivation results
in sleep
- feedback causes increased activation
- altered by cocaine, amphetamines,
meditation, alcohol, anesthetics
- coma
6. Cerebrum – bulk of brain
- cerebral cortex thin area of gray matter
- 6 layers of nerve cell bodies
- during development – the brain increases in
size and gray matter enlarges faster than white
matter – thus it folds (fissures) longitudinal
fissure – separates left and right (hemispheres)
- corpus callosum – white matter that contains
fibers connecting the hemispheres – larger in
female
- Lobes – each hemisphere has 4 lobes divided by
sulci (shallow)or fissures (deep)
 frontal, parietal, temporal, and occipital
- Brain lateralization
- left handed – parietal, occipital lobes of RT
hemisphere are narrower and frontal of left is
narrower
- left hemisphere – right handed control
spoken and written language, numerical,
scientific skills and reasoning
- White matter – myelinated axons – 3
directions
1. association fibers – transmit impulses
between gyri of same hemispheres
2. commissural fiber – one side to another
ex – corpus callosum
3. projection fibers – transmit from cerebrum
to other parts of brain
- Basal Ganglia
- paired masses of gray matter within white of
each hemisphere
- control subconscious movements (swinging
of arms while walking)
- damage – uncontrollable shaking –
Parkinson’s
- Stroke – total paralysis of one side opposite
damage
- Limbic system
- wishbone shaped group of structures
encircling the brain stem and controls
emotions of pain, pressure, anger, rage, fear,
sorrow, sexual feelings, and affection
- also with cerebrum – functions in memory
- Functional areas (3 general)
1. sensory – visual, auditory, gustatory and
olfactory
2. motor – muscular, language
3. association – motor and sensory
connection (pg 231)
4. memory – engram - memory trace in
brain that represents an experience
7. Cerebellum – 2nd largest portion – behind medulla
and pons and below occipital lobes
- surface (cortex) consists of gray matter
- white matter resembles branches of tree
- subconcious skeletal movement for
coordination, balance and posture
- ataxia – lack of coordination
D. Neurotransmitters
1. Acetylcholine – usually excitatory, skeletal neuro
muscular junctions
2. Dopamine – emotional responses, subconscious
movement of skeletal muscle – Parkinson’s
3. Norephinephrine – neuro muscular and neuro
glandular junctions – related to arousal, dreaming
and mood
4. Seratonin – inhibitory – inducing sleep, sensory
perception, temp regulation and mood
5. Gamma aminobutric acid – inhibitory – target of
anti-anxiety drugs like valium
6. Substance P – associated with pain – stimulates
percelption of pain – opposite of endorphins
7. Enkephalins – suppress substance P
8. Endorphins – inhibit substance P and have pole in
memory, learning, sexual activity
- have been linked to depression and schizopherenia
E. Cranial nerves
Somatic Nervous System – 12 pairs of nerves – 10
pair organized from brain stem
- Roman numerals - designate
- some only sensory
- remainder are mixed